BioMed Research International
Volume 2018 (2018), Article ID 8472309, 15 pages
https://doi.org/10.1155/2018/8472309

Review Article

Biochemical Stimulus-Based Strategies for Meniscus Tissue Engineering and Regeneration

Mingxue Chen,¹ Weimin Guo,¹ Shunag Gao,² Chunxiang Hao,³ Shi Shen,1,4 Zengzeng Zhang,1,5 Zhenyong Wang,1,5 Zehao Wang,¹ Xu Li,1,6 Xiaoguang Jing,1,5 Xueliang Zhang,1,7 Zhiguo Yuan,¹ Mingjie Wang,¹ Yu Zhang,¹ Jiang Peng,¹ Aiyuan Wang,¹ Yu Wang,¹ Xiang Sui,¹ Shuyun Liu,¹ and Quanyi Guo¹

¹Institute of Orthopedics, Chinese PLA General Hospital, Beijing Key Lab of Regenerative Medicine in Orthopedics, Key Laboratory of Musculoskeletal Trauma & War Injuries, PLA, No. 28 Fuxing Road, Haidian District, Beijing 100853, China
²Center for Biomaterial and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, No. 5 Yiheyuan Road, Haidian District, Peking University, Beijing 100871, China
³Institute of Anesthesiology, Chinese PLA General Hospital, No. 28 Fuxing Road, Haidian District, Beijing 100853, China
⁴Department of Bone and Joint Surgery, The Affiliated Hospital of Southwest Medical University, No. 25 Taiping Road, Luzhou 646000, China
⁵First Department of Orthopedics, First Affiliated Hospital of Jiamusi University, No. 348 Dexiang Road, Xiangyang District, Jiamusi 154002, China
⁶School of Medicine, Nankai University, Tianjin 300071, China
⁷Shanxi Traditional Chinese Hospital, No. 46 Binzhou West Street, Yingze District, Taiyuan 030001, China

Correspondence should be addressed to Shuyun Liu; clear_ann@163.com and Quanyi Guo; doctorguo_301@163.com

Received 28 September 2017; Accepted 19 December 2017; Published 17 January 2018

Academic Editor: Haining Zhang

Copyright © 2018 Mingxue Chen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Meniscus injuries are very common and still pose a challenge for the orthopedic surgeon. Meniscus injuries in the inner two-thirds of the meniscus remain incurable. Tissue-engineered meniscus strategies seem to offer a new approach for treating meniscus injuries with a combination of seed cells, scaffolds, and biochemical or biomechanical stimulation. Cell- or scaffold-based strategies play a pivotal role in meniscus regeneration. Similarly, biochemical and biomechanical stimulation are also important. Seed cells and scaffolds can be used to construct a tissue-engineered tissue; however, stimulation to enhance tissue maturation and remodeling is still needed. Such stimulation can be biomechanical or biochemical, but this review focuses only on biochemical stimulation. Growth factors (GFs) are one of the most important forms of biochemical stimulation. Frequently used GFs always play a critical role in normal limb development and growth. Further understanding of the functional mechanism of GFs will help scientists to design the best therapy strategies. In this review, we summarize some of the most important GFs in tissue-engineered menisci, as well as other types of biological stimulation.

1. Introduction

Meniscus injuries are very common in athletes and middle-aged and older people [1]. The blood supply and nerve distribution to the meniscus are variable. The meniscus can be subdivided into three areas: the inner white region, which lacks a blood supply; the outer red region, which has a blood supply; and the middle red–white region, which shows transitional features. Meniscus injuries to the inner white region or middle red–white region remain hard to repair [2]. Orthopedic surgeons usually use a partial meniscectomy to treat these meniscus injuries. However, this inevitably leads to osteoarthritis (OA) of the injured knee [3]. Meniscus allograft transplantation can overcome this dilemma to an extent. However, there are some limitations to transplantation, such as viral transmission, graft preservation, and mismatching [4].

The development of tissue engineering and regeneration medicine provides a new avenue for meniscus repair. By combining cells and scaffolds, we can form tissue-engineered constructs. However, it is difficult to use these constructs to repair the injury tissues. Biomechanical or biochemical stimulation can enhance the maturation and remodeling of these constructs. Hence, we usually regard the seed cells, scaffolds, and biomechanical and biochemical stimulation as the three indispensable elements of tissue engineering. Meniscal fibrochondrocytes and stem cells are the two most important kinds of seed cell [5]. They all play critical roles in meniscus regeneration. Scaffolds can be roughly divided into scaffolds derived from synthetic polymers or from biological materials [5]. It is very hard to regenerate the injured tissue solely with a combination of seed cells and scaffold. However, biomechanical and biochemical stimulation can build a bridge between the tissue-engineered construct and the functional tissue. The biomechanical stimulation usually mimics the native meniscus biomechanical microenvironment, such as the compressive loading or tensile strength [6, 7]. However, this review focuses on the effects of biochemical stimulation of the tissue-engineered meniscus.

The most familiar biochemical stimulation is growth factor (GF). The GFs used usually play a significant role in normal limb development and growth [8–11]. They can influence cell migration, proliferation, differentiation, and apoptosis. When used for tissue regeneration, they may also play important roles in tissue maturation and remodeling. Finally, we summarize other forms of biological stimulation that are used in the tissue-engineered meniscus.

2. Growth Factors and Gene Therapy for Meniscus Tissue Engineering

The desirable properties and functions of the native meniscus are largely dependent on the maintenance of the unique extracellular matrix (ECM) and its structure, which is generally modulated by the anabolic and catabolic activities of meniscal cells [74]. Growing evidence indicates that in addition to genetic factors, growth factors play a key role in the metabolic activity of fibrochondrocytes and further affect development, homeostasis, and regeneration [75–78]. By binding to specific receptors on the target cell surface, growth factors may initiate signal transduction cascades and further affect cellular processes and metabolic activity. Growth factors may promote meniscus repair and regeneration via multiple mechanisms, including recruitment of fibrochondrogenic cells, enhancement of fibrochondrogenic cell proliferation, and stimulation of ECM production. Thus, local administration of growth factors may create a favorable microenvironment and further promote meniscus repair. Growth factors commonly used for meniscus and cartilage regeneration are summarized in Table 1. Of the numerous bioactive molecules, the most important and thoroughly studied growth factors include the transforming growth factor-β (TGF-β) superfamily, basic fibroblast growth factor (bFGF), and insulin-like growth factor-1 (IGF-1). The effects of other growth factors, such as connective tissue growth factor (CTGF), vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), hepatocyte growth factor (HGF), and platelet-rich plasma (PRP), on meniscus regeneration have also been evaluated.

Table 1: Commonly used growth factors for cartilage and meniscus tissue engineering and regeneration.

Growth factor
Cell types
Culture conditions
Findings
Authors and reference

TGF-β1
Meniscal fibrochondrocytes
Monolayer culture
Increase collagen and GAG synthesis
Tanaka et al. [12]

Pangborn and Athanasiou [13]

TGF-β
Meniscal fibrochondrocytes
Monolayer/alginate beads/explant culture
Increase proteoglycan synthesis
Collier and Ghosh [14]

TGF-β1
Meniscal fibrochondrocytes
PGA scaffold culture
Increase collagen and GAG synthesis
Pangborn and Athanasiou [15]

TGF-β1
Meniscal fibrochondrocytes
Meniscus explant culture
Increase collagen and GAG synthesis
Imler et al. [16]

TGF-β1 and C-ABC
Cocultures of meniscal fibrochondrocytes and articular chondrocytes
Agarose scaffold culture
Increase collagen synthesis and the Young’s modulus and ultimate tensile strength
MacBarb et al. [17]

TGF-β1 and C-ABC
Meniscal fibrochondrocytes and articular chondrocytes
Agarose scaffold culture
Enhance compressive and tensile properties
Huey and Athanasiou [18]

TGF-β1 and HP
Meniscal fibrochondrocytes
PLLA scaffold culture
Increase collagen and GAG deposition and compressive properties
Gunja et al. [19]

TGF-β1
Meniscal fibrochondrocytes and articular chondrocyte
Monolayer culture
Increase SMA content
Zaleskas et al. [20]

TGF-β1
Articular chondrocytes
Explant culture
Reduce MMP-1, MMP-3, MMP-8, and MMP-13 expression and induced TIMP-2 and TIMP-3 production
Hui et al. [21]

TGF-β1
Articular chondrocytes
Monolayer culture
Suppress MMP-13, MMP-14 expression
Takahashi et al. [22]

TGF-β1
Human synovium-derived stem cells
Monolayer culture
Enhance chondrogenic differentiation and proliferation
Kim et al. [23]

TGF-β1
BMSCs
Monolayer culture
Enhances chondrogenic differentiation and proliferation
Jian et al. [24]

TGF-β
MSCs
Monolayer culture
Induce chondrogenic differentiation
Augustyniak et al. [25]—

Tang et al. [26]

TGF-β1, TGF-β2, IGF-I
Dedifferentiated adult human articular chondrocytes
Monolayer culture
Reexpress aggrecan and type II collagen genes
Yaeger et al. [27]

TGF-β1
BMSCs
Chitosan/gelatin scaffolds culture
Promoted chondrogenic differentiation of MSCs, cartilage matrix synthesis, repair of rabbit cartilage defects
Diao et al. [28]

TGF-β3
BMSCs
PLGA-gelatin/chondroitin sulfate/hyaluronic acid hybrid scaffold in rabbit
Enhance MSCs proliferation and abundant ECM production, cartilage regeneration
Fan et al. [29]

TGFβ3
None
PCL-HA scaffold in rabbit
Regenerate articular cartilage by homing of endogenous cells
Bochyńska et al. [30]

TGFβ3 and CTGF
None
PCL scaffold in sheep
Lead to heterogeneous meniscus regeneration
Lee et al. [31]

BMP-2
Dedifferentiated articular chondrocytes
Monolayer culture
Reverse chondrocyte dedifferentiation
Gouttenoire et al. [32]

BMP-2
None
Intra-articular injection in mice
Enhance matrix turnover in native and IL-damaged cartilage
Davidson et al. [33]

BMP-2
Articular chondrocytes
Solvent preserved human meniscus explant culture
Stimulate chondrocytes migration and proliferation and enhance meniscus repair
Minehara et al. [34]

BMP-7
Articular chondrocytes
Monolayer culture
Counteract chondrocyte catabolism induced by proinflammatory cytokines
Elshaier et al. [35]

Huch et al. [36]

BMP-7
None
Intra-articular injection in sheep
Fill meniscal defect with cellular fibrous tissue
Forriol et al. [37]

BMP-7
None
Injection into Achilles tendon in rats
Regenerate meniscus-like tissue
Ozeki et al. [38]

BMP-2/-4/-6
hBMSC
Monolayer culture
Enhance chondrogenic differentiation
Sekiya et al. [39]

BMP-2/-4/-6/ -7 and CDMP-1/-2
Articular chondrocytes
Alginate beads culture
BMP-7 are most potent in upregulating proteoglycan production and counteract catabolic activity mediated by IL-1
Chubinskaya et al. [40]

BMP-7 and TGF-β1
Synovial mesenchymal stem cells
Pellet culture
Enhance chondrogenesis from synovium-derived MSCs
Miyamoto et al. [41]

BMP-2/BMP-7, TGF-β1
Synovial tissue
Agarose scaffold culture
Enhance chondrogenic differentiation of synovial explants
Shintani and Hunziker [42]

bFGF
Meniscal fibrochondrocytes
Monolayer culture
Enhance proliferation
Hiraide et al. [43]

Kasemkijwattana et al. [44]

bFGF
Meniscal fibrochondrocytes
PGA scaffold culture
Enhance proliferation
Stewart et al. [45]

bFGF
Meniscal fibrochondrocytes
Alginate scaffold culture
Enhance proliferation and SMA expression
Cucchiarini et al. [46]

bFGF
BMSCs
Monolayer culture
Enhance proliferation
Sotiropoulou et al. [47]

bFGF
MSCs
Monolayer culture
Maintain the multilineage differentiation potential of MSCs
Buckley and Kelly [48]—

Martin et al. [49]

bFGF and hypoxia
Meniscal fibrochondrocytes
Three-dimensional pellet culture
Reexpress collagen type II and PGs gene
Adesida et al. [50]

bFGF
Intervertebral disc cells
Monolayer and alginate beads culture
Suppress proteoglycan production
Li et al. [51]

bFGF
Articular chondrocytes
Monolayer culture
Suppress collagen type II and decorin synthesis
Sonal [52]

bFGF
Articular chondrocytes
Monolayer culture
Upregulate MMPs, aggrecanases, nitric oxide and superoxide anion expression
Muddasani et al. [53]

bFGF
Articular chondrocytes
Alginate culture
Antagonizes proteoglycan synthesis
Loeser et al. [54]

bFGF
Articular chondrocytes
Gelatin-chondroitin-hyaluronan hybrid scaffold culture
Repair with hyaline-like cartilage
Deng et al. [55]

bFGF and hypoxia
Meniscal fibrochondrocytes
PLLA scaffold culture
Enhance GAGs production and compressive properties of constructs
Gunja and Athanasiou [56]

bFGF and TGF-β3
None
Electrospun PCL scaffolds culture
Improve meniscus repair and scaffold integration
Ionescu et al. [57]

IGF–1
Meniscal fibrochondrocytes
Alginate scaffold culture
Increase collagen and GAG synthesis as well as mechanical properties
Puetzer et al. [58]

IGF-1
Meniscal fibrochondrocytes
Monolayer culture
Enhanced proliferation and ECM formation
Tumia and Johnstone [59]

IGF-1
BMSCs
Monolayer culture
Modulate chondrogenic differentiation
Longobardi et al. [60]

IGF-1
Meniscal fibrochondrocytes
Explant culture
Stimulated cell migration
Bhargava et al. [61]

IGF-1
BMSC (transfection of hIGF-1 gene)
Intra-articular injection in goat
Promote the repair of full-thickness meniscal defects
Zhang et al. [62]

IGF-1
Articular chondrocytes
(transfection of hIGF-1 gene)
Polymerized fibrinogen in equine model
Enhance cartilage healing
Goodrich et al. [63]

IGF-1 and TGF-β1
BMSCs
Three-dimensional fibrin disk culture
Enhance chondrogenic differentiation
Worster et al. [64]

IGF-1 and TGF-β1
None
Explant culture
Improve repair of meniscus avascular zone
Izal et al. [65]

IGF–1, TGF-β1, bFGF
Fibroblast-like synoviocytes
PGA/PLLA scaffold culture
Enhance collagen type II and aggrecans expression
Fox et al. [66]

IGF and BMP-7
Articular chondrocytes
Monolayer culture
Suppress MMP-13 expression
Im et al. [67]

VEGF
None
VEGF-coated sutures in a sheep
Fail to promote meniscus healing
Petersen et al. [68]

HGF
Meniscal fibrochondrocytes
(transfection of HGF-1 gene)
PGA scaffold in mice
Induce blood vessel formation in engineered constructs
Hidaka et al. [69]

CTGF
Meniscal fibrochondrocytes
Fibrin glue in rabbits model
Promote healing of meniscal defect in the avascular zone
He et al. [70]

CTGF
None
Hydrogel collagen scaffold in rats model
Enhance articular cartilage regeneration
Nishida et al. [71]

PDGF-AB
Meniscal fibrochondrocytes
Monolayer culture
Increase proliferation and matrix formation
Tumia and Johnstone [72]

PRP
Meniscal fibrochondrocytes
Gelatin hydrogel in a rabbit model
Promote meniscus repair
Ishida et al. [73]

2.1. The TGF-β Superfamily

The TGF-β superfamily consists of more than 30 members and includes TGF-βs, activins, and bone morphogenetic proteins (BMPs) [79, 80]. Growth factors from the TGF-β superfamily are involved in regulating various cellular processes, including cell survival, growth, proliferation, migration, differentiation, and apoptosis, as well as synthesis and degradation of the ECM [80–82]. TGF-βs and BMPs have been studied most extensively and have shown great potential in the field of tissue engineering and regenerative medicine over the past few decades [77]. Thus, it is possible that local administration of these factors may benefit functional meniscus regeneration.

2.1.1. TGF-βs

There are three different isoforms of TGF-β in mammals: TGF-β1, TGF-β2, and TGF-β3 [83]. The most thoroughly studied TGF-βs in the musculoskeletal system are TGF-β1 and TGF-β3 [77]. TGF-β is very effective for stimulating collagen production and glycosaminoglycan (GAG) synthesis by meniscal cells [12, 14, 18, 19]. For example, Pangborn and Athanasiou [13, 15] evaluated the effects of four common growth factors (TGF-β1, PDGF-AB, IGF-I, and bFGF) on meniscal fibrochondrocyte ECM synthesis in monolayers or in three-dimensional (3D) cultures. These studies found that treatment with TGF-β1 led to the greatest amount of collagen and GAG production compared to other growth factors. Similarly, Imler et al. [16] demonstrated that TGF-β1 was the most potent stimulator of both collagen and GAG synthesis. In addition, a combination of TGF-β1 and chondroitinase ABC (C-ABC) improved the biochemical and biomechanical properties of an agarose scaffold seeded with bovine meniscus cells and articular chondrocytes [17, 18]. TGF-β1 also markedly increased the amount of alpha-smooth muscle actin (α-SMA) in meniscal cells, which plays a crucial role in the contraction of the collagen–GAG matrix [20]. Not only does TGF-β enhance ECM synthesis, but it also blocks matrix degradation via downregulation of proteases such as matrix metalloproteases (MMPs) or upregulation of inhibitors of MMPs (TIMPs) [21, 22]. In addition, TGF-β is a chief anticatabolic agent counteracting the deleterious effects of catabolic cytokines. For example, several studies [21, 22, 84] have reported that TGF-β may effectively suppress the catabolic effects mediated by interleukin (IL)-1 and tumor necrosis factor (TNF)-α, including the upregulation of MMPs (MMP-1, MMP-3, MMP-8, MMP-13, and MMP-14) and downregulation of ECM-related genes. In addition, TGF-β may increase TIMP production [21].

In addition to regulating matrix metabolism, another chief function of TGF-β in meniscus tissue engineering is the recruitment, proliferation, and fibrochondrogenic differentiation of mesenchymal stem cells (MSCs) [23, 24, 85]. In general, TGF-β plays a crucial role in chondrogenesis [25, 86], and studies have revealed that TGF-β3 has the strongest chondrogenic effects of all isoforms [26, 87, 88]. The synergistic effects of TGF-β and IGF-1 on the induction of dedifferentiated articular chondrocytes from their original phenotype were also observed [27]. Kulyk et al. revealed that, in this process, TGF-β upregulates transcription factor SOX9 through the Smad pathway, followed by enhancement of cartilage gene expression, such as type II collagen and aggrecan.

Furthermore, several studies have demonstrated that TGF-β supplementation can promote cartilage and meniscus repair and has promise for meniscus regeneration [28–30]. For example, Lee et al. [89] investigated the potential of anatomically correcting TGF-β3-infused bioscaffolds for articular cartilage regeneration. Histological and mechanical results showed that TGF-β3-infused bioscaffolds promoted hyaline cartilage formation in the articular surface with excellent mechanical properties similar to those of native articular cartilage 4 months after implantation in a rabbit model. Moreover, this study was the first to demonstrate that TGF-β3 stimulates articular cartilage regeneration through the recruitment of endogenous stem or progenitor cells, chondrogenic differentiation, and histogenesis and provided evidence that complex tissues may regenerate by homing of endogenous cells without cell transplantation. Similarly, McNulty and Guilak [90] found that applying TGF-β1 enhanced cellular accumulation and increased the shear strength of the repaired tissue, which suggests that TGF-β1 is essential for cartilage integrity and may be a potent alternative for enhancing meniscal repair.

In general, TGF-β is likely to push cells toward a more chondrocytic phenotype and to induce hyaline cartilage formation. Freymann et al. [91] revealed that TGF-β enhanced the production of specific cartilage and collagen type II proteoglycans by mesenchymal or meniscus cells but did not significantly increase the formation of type I collagen in meniscus 3D micromass or scaffold cultures, which is the main component of fibrocartilage tissue and plays a crucial role in the tensile strength of the native meniscus. Because the unique inhomogeneous feature of the meniscus presents a tremendous challenge for total meniscus regeneration, the use of various combinations of growth factors may be a promising solution. Lee et al. [31] spatiotemporally delivered a combination of CTGF and TGF-β3 to regenerate the meniscus in a sheep model. They demonstrated that spatiotemporally delivered CTGF and TGF-β3 could lead to heterogeneous meniscus regeneration by inducing endogenous stem/progenitor cells to differentiate and synthesize zone-specific types I and II collagen.

However, several unfavorable side effects of TGF-β1 treatment must be mentioned, such as induction of synovial fibroplasias and fibrosis, stimulation of osteophyte formation, and recruitment of inflammatory leukocytes [84, 92, 93]. Fortunately, studies have reported that applying local inhibitors of TGF-β may help block these undesirable side effects [84].

2.1.2. Bone Morphogenetic Proteins (BMPs)

BMPs also belong to the TGF-β superfamily and play a crucial role in bone and cartilage formation and repair [94–96]. They share several functions with TGF-βs and have potential for meniscal regeneration [97]. The distinct and key function of BMPs is osteogenic differentiation of human MSCs (hMSCs), but they are not restricted to bone and also induce osteoblastic [98, 99], tenogenic [100], and chondrogenic [101] differentiation of MSCs. For instance, a study examined the capacity of BMP-2, BMP-4, and BMP-6 to promote chondrogenic differentiation of MSCs and encourage cartilage formation in vitro. It found that BMP-2 is more effective than others for chondrogenic differentiation of MSCs [39]. Gouttenoire et al. [32] reported the specific capability of BMP-2 to reverse chondrocyte dedifferentiation by increasing cartilage-specific collagen type II production in dedifferentiated chondrocytes. In addition, Shintani and Hunziker [42] evaluated the potential of BMP-2, BMP-7, and TGF-β1 for inducing chondrogenic differentiation of synovial explants. In that study, all three growth factors induced chondrogenic differentiation of synovial MSCs and enhanced the formation of cartilaginous tissue. However, BMP-7 was more potent and effective than the other growth factors in inducing chondrogenesis. In addition, Miyamoto et al. [41] reported that the effects of BMP-7 on chondrogenic differentiation of MSCs were enhanced when it was combined with TGF-β3.

BMPs have a clear role in modulating tissue homeostasis and blocking degradation processes [102, 103]. Chubinskaya compared the anabolic activity of BMPs (BMP-2, BMP-4, BMP-6, and BMP-7) and cartilage-derived morphogenetic proteins (CDMP-1 and CDMP-2) in human articular chondrocytes [40]. BMP-2, BMP-4, and BMP-7 were more potent in upregulating proteoglycan production than the other three growth factors, with the highest proteoglycan content on day 9 in the presence of BMP-7. Furthermore, under simultaneous treatment with IL-1β and the aforementioned growth factors, only BMP-7 effectively antagonized the inhibition of proteoglycan synthesis mediated by IL-1β. Similar studies have also demonstrated that BMP-7 effectively counteracted chondrocyte catabolism induced by various proinflammatory cytokines such IL-1, IL-6, IL-8, MMP-1, MMP-13, and TNF-α [35, 36, 67, 104]. The prominent proanabolic and anticatabolic properties of growth factors are essential to their clinical application, particularly under local inflammatory conditions triggered by trauma, degenerative disease, or surgery. In addition, BMP-7 increases matrix synthesis without stimulating uncontrolled fibroblast proliferation and osteophyte formation [105, 106]. It is interesting that BMP-2 may enhance matrix turnover in native and IL-damaged cartilage, as evidenced by upregulated collagen type II and aggrecan expression and increased aggrecan degradation, which suggests that BMP-2 treatment may lead to a reparative response in chondrocytes after cartilage injury or osteoarthritis [33].

BMPs effectively promote cartilage and osteochondral regeneration [107, 108]. BMPs have also been evaluated for their potential in meniscus repair and regeneration. For example, Forriol et al. [37] investigated the effects of BMP-7 treatment on meniscal defects in a sheep model. In that study, defects were made in the avascular region of the medial meniscus and treated with Putty® (control group) or osteogenic protein-1 (OP-1) Putty, which contains BMP-7 (experimental group). After 12 weeks, meniscal defects in the experimental group were filled with cellular fibrous tissue that connected both edges of the defects. In addition, Minehara et al. [34] developed a chemotactic cell-seeding technique with a solvent-preserved human meniscus scaffold to improve meniscal repair. They found that rhBMP-2 stimulated chondrocyte migration and proliferation as well as proteoglycan production throughout the meniscus tissue, which suggests a potential application of rhBMP-2 as a chemokinetic factor for loading into a scaffold for cartilage and meniscus tissue engineering. In another study, the Achilles tendon was treated with BMP-7 and transplanted into a rat meniscal defect model [38]. After 12 weeks, regenerated meniscus-like tissue was observed; this may effectively prevent cartilage degeneration.

In general, BMP-2 and BMP-7, which are approved by the Food and Drug Administration (FDA) for clinical use, have shown promising effects on chondrocyte differentiation, ECM production, and fibrocartilaginous tissue regeneration. Synergistic effects have been observed when BMP-7 is combined with other growth factors such as IGF-1 and TGF-β1 [109], which suggests that the addition of these factors may lead to greater improvements in meniscus repair and regeneration.

2.2. Basic Fibroblast Growth Factor (bFGF)

The fibroblast growth factor (FGF) family is composed of 18 structurally related signaling molecules [110, 111]. Basic FGF, also known as bFGF, FGF2, or FGF-β, is an important member of the FGF family and is found in the cartilaginous matrix [78, 102, 112, 113]. The mitogenic effects of FGF on MSCs were first reported by Oliver more than 27 years ago [114]. FGF is a powerful mitogen for a variety of cell types, including chondrocytes, fibrochondrocytes, osteoblasts, and adipocytes [102]. Numerous studies [45, 115, 116] have demonstrated the strong stimulating effects of bFGF on meniscal cell proliferation in monolayer cultures as well as in tissue-engineered constructs. For example, one study [44] evaluated the effects of nine growth factors (EGF, NGF, IGF-1, TGF-α, TGF-β, a-FGF, b-FGF, PDGF-AA, and PDGF-AB) on meniscal fibrochondrocyte proliferation in a monolayer culture. EGF, bFGF, TGF-α, and PDGF-AB stimulate cell proliferation, with bFGF having the greatest effect. Cucchiarini et al. [46] investigated the effects of bFGF on proliferation and metabolic activities of meniscal cells using a gene-based approach in which bFGF was vectored with a recombinant adeno-associated virus; increased cell proliferation and alpha-smooth muscle actin (α-SMA) expression were observed. Sotiropoulou et al. [47] also demonstrated that adding bFGF to culture media enhanced the proliferative capacity of hMSCs. In addition, FGF maintains the multilineage differentiation potential of MSCs during proliferation, including chondrogenic, osteogenic, adipogenic, and neurogenic differentiation [48, 49, 117, 118].

Monolayer expansion may result in loss of expression of collagen type II and matrix-forming phenotypes of meniscal cells. However, Adesida et al. [50] demonstrated the ability of bFGF to restore the chondrogenic phenotype of passaged meniscal cells based on reexpression of collagen type II and proteoglycan at both the gene and protein levels. In that study, supplementation with bFGF upregulated expression of collagen type II 200-fold in subsequent 3D pellet cultures. Moreover, this favorable effect was further enhanced under 5% oxygen culture conditions.

The specific role of bFGF in anabolic and catabolic processes remains controversial. Studies have demonstrated the capacity of bFGF to stimulate the anabolic activity of cartilage and meniscus [13]. For example, Tumia and Johnstone [115] demonstrated that meniscal cells from all zones responded positively to bFGF supplementation by enhancing DNA synthesis and ECM formation. Cheng et al. [119] also demonstrated that bFGF boosted the kinetics of MSC chondrogenesis, resulting in faster differentiation and leading to enhanced ECM accumulation. However, several studies [16, 51] revealed that bFGF was the least effective stimulator of both protein and proteoglycan production. In addition, Loeser et al. [54] reported that bFGF had dramatic antagonistic effects on proteoglycan accumulation promoted by IGF-1 and/or BMP-7. bFGF is also an antagonist of collagen type II and decorin production induced by IGF-1 and TGF-β in porcine articular chondrocytes [52]. Moreover, some evidence suggests that bFGF leads to the upregulation of MMPs and aggrecanases and increases reactive oxygen species such as nitric oxide (NO) and the superoxide anion [53]. The role of two members of the FGF family, FGF-2 and FGF-18, in cartilage homeostasis was evaluated by Ellman et al. [120, 121], who concluded that bFGF is a catabolic mediator in human cartilage via increased matrix-degrading enzyme activity and decreased ECM production, whereas FGF-18 is likely an anabolic regulator in human articular chondrocytes, enhancing ECM formation and chondrogenic differentiation and inhibiting cell proliferation.

Despite its controversial effects on cartilage homeostasis, the effects of bFGF on tissue regeneration and repair were investigated and revealed positive results [43, 55, 122, 123]. Deng et al. [55] developed gelatin microspheres in combination with controlled-release bFGF for cartilage repair in a rabbit model. Histological results showed that defects were filled with hyaline-like cartilage after 24 weeks, which indicates the great potential of a bFGF-loaded scaffold for promoting cartilage regeneration. In another study [56], meniscal cells were cultured on poly L-lactic acid (PLLA) scaffolds with bFGF under hypoxic conditions. After 4 weeks, histological results demonstrated synergic effects of hypoxia and bFGF on enhancing GAG production and compressive properties of tissue-engineered meniscus constructs in vitro. In addition, Ionescu et al. [57] investigated the effects of bFGF as a promitotic manager and TGF-β3 as a promatrix formation manager on meniscus repair and integration with electrospun polycaprolactone (PCL) scaffolds. This study biochemically, histologically, and mechanically showed that short-term delivery of bFGF or sustained delivery of TGF-β3 enhanced integration for bovine meniscus tissues, which suggests that both bFGF and TGF-β3 have the potential to promote meniscus repair.

Miyakoshi et al. [124] reported that local administration of bFGF led to inflammatory responses and osteophyte formation in a rabbit model. bFGF was also closely associated with synovial proliferation and hyperplasia in rheumatoid arthritis joints [120]. Given the potentially deleterious effects and controversial role of bFGF in articular development, the use of bFGF for meniscus repair and regeneration must be further explored. Although there is less literature on the role of FGF-18 in meniscus repair, it has shown promising anabolic effects on chondrocytes [121, 125]. More detailed studies are necessary to define the exact effects of FGF on meniscal cells, explants, and engineered constructs and to provide evidence for meniscus regeneration.

2.3. Insulin-Like Growth Factors (IGFs)

Two distinct forms of IGFs, IGF-1, and IGF-2 play a pivotal role in tissue metabolism [126]. IGF-1 is a vital anabolic growth factor of cartilaginous tissue under normal conditions and has been studied most in cartilage and meniscus tissue engineering [67, 127]. In general, IGF-1 enhances anabolic effects and inhibits catabolic responses. Puetzer et al. [58] explored the effects of IGF-1 on the mechanical and biochemical properties of meniscal constructs. After 4 weeks, IGF-1 treatment led to a 26-fold increase in GAG production, a 10-fold increase in collagen production, and a 3-fold increase in the equilibrium modulus of engineered meniscal constructs compared to 0-week controls, providing evidence for IGF-1 as a potential treatment in meniscal regeneration. A mixture of bFGF, TGF-β1, and IGF-1 elevates expression of collagen type II and aggrecans in fibroblast-like synoviocytes in vitro [66]. In another study [59], IGF-1 applied to monolayer cultures for 48 h enhanced fibrochondrocyte proliferation and formation of ECM in all zones of the meniscus. What is interesting is that the meniscal cells from the avascular region responded more favorably than those from the vascular region. This indicates that fibrochondrocytes from avascular meniscal tissue are able to express their intrinsic potential to regenerate when exposed to suitable growth factors. In addition, IGF-1 effectively decreases expression of aggrecanase-1 and reduces the release of degrading molecules such as MMPs [67]. For example, Im et al. [67] demonstrated the prominent suppressive effects of the combination of IGF-1 and BMP-7 on MMP-13 expression: IGF-1 and BMP-7 decreased inflammatory cytokine expression and/or their intermediate gene products. However, chondrocyte responsiveness to IGF-1 may diminish with age and under conditions of inflammation due to overexpression of IGF binding proteins [128–131]. BMP-7 seems attractive for counteracting these effects because of its robust anticatabolic actions. Therefore, synergistic effects resulting in enhanced ECM production were observed when BMP-7 and IGF-I were used in combination [109, 132].

Apart from its anabolic effects on cartilaginous tissue, IGF-1 promoted the chondrogenic differentiation of MSCs, which may be further enhanced when combined with TGF-β1 [60, 64]. IGF-1 also stimulated cell migration in specific regions of the meniscus [61]. Together, these findings support the regenerative potential of IGF for cartilage and meniscus tissue engineering. Zhang et al. [62] studied the ability of human IGF-1- (hIGF-1-) meshed bone marrow stromal cells (BMSCs) to promote the repair of full-thickness meniscal defects and found that defects were completely filled with white tissue 16 weeks after treatment in a goat model that was histologically and biochemically similar to normal meniscal fibrocartilage. In another study, Goodrich et al. [63] investigated the ability of chondrocytes modified by an adenovirus vector encoding equine IGF-1 to enhance cartilage healing in an equine model. Histological results showed that defects were filled with a more hyaline-like tissue at 8 months, whereas control defects were covered with irregular and more fibrous tissue. Izal et al. [65] also reported that treatment with TGF-β1 and IGF-1 in combination improved repair of the meniscus avascular zone by enhancing meniscal cell proliferation and tissue attachment.

2.4. Other Growth Factors and Small Bioactive Molecules

In addition to the aforementioned growth factors, other growth factors, such as CTGF, VEGF, PDGF, HGF, and PRP, have been studied for their ability to improve meniscal repair and regeneration. Inducing angiogenesis may be essential to enhancing the healing capacity of the meniscus tissue. Thus, VEGF seems to be attractive for improving meniscus repair by stimulating angiogenesis. However, Petersen et al. [68, 133] demonstrated that VEGF failed to promote healing in the meniscus in a sheep meniscal longitudinal injury model treated with VEGF-coated sutures. In addition, HGF induces blood vessel formation in engineered meniscal fibrochondrocyte-polyglycolic acid (PGA) constructs without increasing any mechanical properties [69]. The effects of CTGF were also assessed. He et al. [70] studied the reparative effects of CTGF on enhancing meniscal repair in the meniscal avascular zone in a rabbit model and demonstrated that CTGF might promote healing of defects by stimulating ECM deposition within the repair zone. Nishida et al. [71] also reported that CTGF-hydrogel collagen scaffolds enhanced articular cartilage regeneration in a rat model. PDGF also enhanced wound healing and ECM production as well as cell proliferation; thus, it was believed to be capable of enhancing tissue regeneration and repair [126]. Tumia and Johnstone [72] investigated the capacity of PDGF-AB to improve meniscal tissue regeneration in all three zones of the meniscus and found that it enhanced fibrochondrocyte proliferation and new matrix formation, which suggests that PDGF may be of benefit in meniscus regeneration. PRP is the source of multiple growth factors, including TGF-β, PDGF, VEGF, IGF-1, bFGF, and EGF [73, 134]. Because growth factors are effective in meniscal healing, PRP may be a potent agent for meniscal repair. PRP promoted cartilage regeneration by increasing ECM content in a rabbit model [134]. Ishida [73] also demonstrated the ability of PRP to encourage matrix deposition and proliferation of meniscal cells in a monolayer culture, histologically enhancing the healing of meniscal defects with tissue that resembled the inner region of the meniscus in a rabbit model. However, Zellner et al. [135] reported no improvements in the healing of a meniscus defect after treatment with PRP-loaded hyaluronan-collagen composite matrices.

Several small bioactive molecules, such as kartogenin (KGN), aptamer, Y-27632, and E7 peptide, have also attracted great interest and shown promising results in cartilage and meniscus regeneration. For example, Huang et al. [136] reported that KGN not only promoted chondrogenic differentiation of tendon stem cells in vitro but also enhanced meniscus-like tissue formation in a rabbit model. Hu et al. [137] demonstrated that an aptamer-bilayer scaffold could specifically recognize and bind with MSCs, while efficiently recruiting them to enrich the MSCs around the osteochondral defect, successfully achieving osteochondral regeneration. A biphasic scaffold functionalized with E7 peptide was also demonstrated to enhance cartilage regeneration via the specific homing of endogenous stem cells [138]. The rho-kinase inhibitor Y-27632 also favors the differentiation of chondroprogenitors and prevents the dedifferentiation of articular chondrocytes [139, 140].

2.5. Gene Therapy

Gene therapy is a novel approach to meniscus tissue engineering that aims to transfer specific genes into an organism or tissue using viral or nonviral vectors or direct injection [102, 141]. Because growth factor concentration gradients and the duration of treatment may play a crucial role in meniscus repair, an important aspect of growth factor treatment is their delivery, given their short biological half-life and rapid clearance potential. To achieve controlled and extended growth factor release, gene transfer techniques may be favored for the local administration of specific factors. The major advantage of gene therapy is high-concentration delivery and persistent expression of these growth factors at the repair site [141–144]. A variety of vectors are currently used for gene transfer in meniscus tissue engineering, including nonviral vectors, adenoviral vectors, retroviral/lentiviral vectors, herpes simplex virus (HSV) vectors, and recombinant adeno-associated virus (rAAV) vectors. Each exhibits specific characteristics [46, 62, 69, 145–149]. In general, nonviral vectors are safe because of their lack of inherent replication capability, but their lower efficiency limits their widespread application [150, 151]. Adenoviral vectors are characterized by high transduction efficiency and a low risk of carcinogenesis, but they are immunogenic and fail to maintain long-term transgene expression [147, 152, 153]. Retroviral/lentiviral vectors permit prolonged transgene expression by integrating into the host cell genome. Although retroviral vectors only transduce actively replicating cells, this obstacle can be overcome with the application of lentiviral vectors, which are most effective for transduction in nondividing cells [153–156]. However, the potential for insertional mutagenesis and tumor gene activation makes them unattractive candidates for clinical application. The advantage of HSV vectors is their ability to deliver long transgenes and a relatively high level of transduction efficiency in nondividing cells. Nevertheless, several studies have revealed that they are toxic and mediate only short-term transgene expression [154]. rAAV vectors are promising gene vehicles because they not only exhibit high transduction efficacy in both dividing and nondividing cells but also allow for long-term transgene expression [46, 148, 149, 154, 157]. In addition, these vectors demonstrate fewer immunogenic effects and are not pathogenic. All of these features make them an attractive choice for tissue engineering. Currently, there are two primary methods of gene transfer: direct injection of a gene into the target tissue and implantation of a genetically modified cell into the body. Numerous experiments have shown the feasibility of gene transfer to several tissues of the musculoskeletal system. Thus, gene transfer of regenerative factors appears to be a promising option for promoting meniscal repair and regeneration.

To date, only a few studies have used gene therapy strategies for meniscus tissue engineering. Growth factors used for gene transfer, including TGF-β1, HGF, and bFGF, have demonstrated the potential to enhance meniscus repair and regeneration. For example, bFGF vectored with rAAV enhanced cell proliferation, cell survival, and α-SMA expression in human meniscal fibrochondrocytes in vitro. This study demonstrated the feasibility of gene transfer for aiding in the repair of meniscal defects [158]. In another study [149], human meniscal fibrochondrocytes modified using a TGF-β rAAV enhanced cell proliferation and matrix synthesis. The TGF-β rAAV vectors were injected directly into the defects in meniscal explants and promoted repair of the meniscus lesions. In addition, meniscal cells and MSCs transduced with adenoviral vectors encoding TGF-β1 and seeded type I collagen–GAG matrices were transplanted into the injured avascular region of bovine menisci. After 3 weeks of in vitro culture, the constructs showed enhanced cellularity, collagen and proteoglycan production, and repair of the meniscal lesions with new tissue [147]. Previously, we also mentioned a study in which BMSCs with the transfected hIGF-1 gene were mixed with calcium alginate gel and aided in the repair of meniscus defects [151]. In general, gene therapy has the potential to enhance meniscus repair and regeneration, but more work is needed to identify the best candidate genes and ideal combinations of genes for meniscus regeneration.

2.6. Other Types of Biological Stimulation

Because a lack of blood supply creates a hypoxic environment in the inner region of the meniscus, scientists have attempted to mimic this environment in in vitro cultures to restore a differentiated phenotype. For example, Adesida et al. [50] demonstrated that low oxygen tension may enhance the matrix-forming phenotype of meniscal cells. Meniscal cells from the inner and outer regions responded differently to hypoxia culture. Indeed, cells from the outer meniscus showed greater sensitivity to lowered oxygen tension than cells from the inner meniscus. The response of meniscal cells to hypoxia was mediated by transcription factor hypoxia inducible factor-1α (HIF-1α), which may play a crucial role in determining the phenotype of inner meniscus cells [159]. Additive and synergistic effects of bFGF and hypoxia were also found on the enhancement of GAG accumulation and the compressive properties of engineered meniscus constructs in vitro [56].

Coculture systems have also been used for meniscus tissue engineering. Gunja and Athanasiou [160] used cocultures of second-passage meniscus cells and primary articular chondrocytes at varying ratios (100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100) to enhance the biochemical and biomechanical properties of engineered constructs. Coculture systems with a higher percentage of chondrocytes led to significantly greater production of collagen type I, collagen type II, and GAG as well as compressive properties, whereas constructs with a higher percentage of meniscus cells resulted in a greater collagen type I content. This study illustrates that it is possible to achieve matrix content and mechanical properties close to native values of the meniscal inner and outer regions using a variety of coculture ratios. In another study, Cui et al. [161] investigated the use of coculture systems of human meniscal cells with MSCs at different ratios (100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100) for meniscus tissue engineering and regeneration. The 75% meniscal cell/25% MSC coculture system showed optimal meniscus ECM production and the lowest hypertrophic expression of MSC genes such as COL10A1 and MMP13 during chondrogenic differentiation. This study indicates that coculture of meniscal cells with MSCs has the potential to expand the limited supply of meniscal cells with enhanced ECM production without hypertrophy.

3. Conclusion, Challenges, and Future Perspectives

Currently, there is no ideal treatment for the meniscus injuries. Tissue engineering is an attractive and promising strategy for repairing or regenerating the meniscus defects. However, regeneration of the functionally engineered meniscus remains challenging because of its complicated structure and functions. This review clearly demonstrates that biochemical stimulus plays a crucial role in the repair and regeneration of the engineered meniscus. There seems to be great potential for growth factors loading to promote regeneration of the engineered meniscus.

Individual growth factors are potent stimulators and have significant effects on many cellular processes, such as cell proliferation, differentiation, and metabolic activity, as well as meniscus repair and regeneration. Numerous experimental studies have demonstrated the synergistic effects of combinations of growth factors on meniscus repair and regeneration. Future investigations are warranted to explore the effects on meniscus tissue engineering of small bioactive molecules, which have already been shown to promote cartilage regeneration. The design of a good growth factor application strategy needs to consider the spatiotemporal specificity of meniscus regeneration. Nevertheless, it is easier than ever to achieve a spatial-specific growth factors distribution using a 3D printing approach. It is also important to develop a sequential release model for multiple growth factors that mimics cell migration and proliferation in the early regeneration stage, differentiation in the middle regeneration stage, and tissue remodeling in the final maturation stage. Gene therapy approaches may help to achieve this in the future.

Physical mechanical loading also plays a vital role in the development, remolding, and regeneration of the meniscus. The combination of mechanical stimulation and growth factors may yield great benefits for meniscus tissue engineering in the future.

Abbreviations

GF: | Growth factor
ECM: | Extracellular matrix
GAG: | Glycosaminoglycan
TGF-β: | Transforming growth factor-β
FGF: | Fibroblast growth factor
bFGF: | Basic fibroblast growth factor
IGF-1: | Insulin-like growth factor-1
CTGF: | Connective tissue growth factor
VEGF: | Vascular endothelial growth factor
PDGF: | Platelet-derived growth factor
HGF: | Hepatocyte growth factor
PRP: | Platelet-rich plasma
BMP: | Bone morphogenetic protein
OP-1: | Osteogenic protein-1
EGF: | Epidermal growth factor
NGF: | Nerve growth factor
HIF-1: | Hypoxia inducible factor-1α
C-ABC: | Chondroitinase ABC
α-SMA: | Alpha-smooth muscle actin
3D: | Three-dimensional
MMP: | Matrix metalloprotease
TIMP: | Inhibitors of matrix metalloprotease
IL: | Interleukin
TNF: | Tumor necrosis factor
OA: | Osteoarthritis
MSC: | Mesenchymal stem cell
BMSC: | Bone marrow stromal cell
hMSC: | Human mesenchymal stem cell
CDMP: | Cartilage-derived morphogenetic protein
PLLA: | Poly L-lactic acid
PCL: | Polycaprolactone
PGA: | Polyglycolic acid
HSV: | Herpes simplex virus
rAAV: | Recombinant adeno-associated virus
KGN: | Kartogenin
FDA: | Food and Drug Administration.

Conflicts of Interest

The authors declare no conflicts of interest.

Authors’ Contributions

All authors were involved in the study and approved its final version. Mingxue Chen and Weimin Guo contributed equally to this work.

Acknowledgments

This work was supported by the National Key R&D Program of China (2017YFC1103404), the High Technology Research and Development Program of China (2012AA020502, 2015AA020303), the National Natural Science Foundation of China (81472092), the Beijing Science and Technology Development Foundation (Z161100005016059), and the Natural Science Foundation of Beijing (7172203).

References

R. W. B. Wyatt, M. C. S. Inacio, K. D. Liddle, and G. B. Maletis, “Prevalence and incidence of cartilage injuries and meniscus tears in patients who underwent both primary and revision anterior cruciate ligament reconstructions,” The American Journal of Sports Medicine, vol. 42, no. 8, pp. 1841–1846, 2014.

C. Starke, S. Kopf, W. Petersen, and R. Becker, “Meniscal repair, Arthroscopy,” Journal of Arthroscopic & Related Surgery: Official Publication of the Arthroscopy Association of North America and the International Arthroscopy Association, vol. 25, no. 9, pp. 1033–1044, 2009.

J. D. Lamplot and R. H. Brophy, “The role for arthroscopic partial meniscectomy in knees with degenerative changes: a systematic review,” The Bone & Joint Journal, vol. 98-b, no. 7, pp. 934–938, 2016.

M. G. Hannon, M. K. Ryan, and E. J. Strauss, “Meniscal allograft transplantation a comprehensive historical and current review,” Bulletin of the Hospital for Joint Diseases, vol. 73, no. 2, pp. 100–108, 2015.

T. Trzeciak, M. Richter, W. Suchorska et al., “Application of cell and biomaterial-based tissue engineering methods in the treatment of cartilage, menisci and ligament injuries,” International Orthopaedics, vol. 40, no. 3, pp. 615–624, 2016.

D. J. Huey and K. A. Athanasiou, “Tension-compression loading with chemical stimulation results in additive increases to functional properties of anatomic meniscal constructs,” PLoS ONE, vol. 6, no. 11, Article ID e27857, 2011.

M. Petri, K. Ufer, I. Toma et al., “Effects of perfusion and cyclic compression on in vitro tissue engineered meniscus implants,” Knee Surgery, Sports Traumatology, Arthroscopy, vol. 20, no. 2, pp. 223–231, 2012.

N. Itoh, “FGF10: A multifunctional mesenchymal-epithelial signaling growth factor in development, health, and disease,” Cytokine & Growth Factor Reviews, vol. 28, pp. 63–69, 2016.

D. M. Ornitz and P. J. Marie, “Fibroblast growth factor signaling in skeletal development and disease,” Genes & Development, vol. 29, no. 14, pp. 1463–1486, 2015.

G. D. Agrogiannis, S. Sifakis, E. S. Patsouris, and A. E. Konstantinidou, “Insulin-like growth factors in embryonic and fetal growth and skeletal development (Review),” Molecular Medicine Reports, vol. 10, no. 2, pp. 579–584, 2014.

L. Jin and X. Li, “Growth differentiation factor 5 regulation in bone regeneration,” Current Pharmaceutical Design, vol. 19, no. 19, pp. 3364–3373, 2013.

T. Tanaka, K. Fujii, and Y. Kumagae, “Comparison of biochemical characteristics of cultured fibrochondrocytes isolated from the inner and outer regions of human meniscus,” Knee Surgery, Sports Traumatology, Arthroscopy, vol. 7, no. 3, pp. 75–80, 1999.

C. A. Pangborn and K. A. Athanasiou, “Effects of growth factors on meniscal fibrochondrocytes,” Tissue Engineering Part A, vol. 11, no. 7-8, pp. 1141–1148, 2005.

S. Collier and P. Ghosh, “Effects of transforming growth factor beta on proteoglycan synthesis by cell and explant cultures derived from the knee joint meniscus,” Osteoarthritis and Cartilage, vol. 3, no. 2, pp. 127–138, 1995.

C. A. Pangborn and K. A. Athanasiou, “Growth factors and fibrochondrocytes in scaffolds,” Journal of Orthopaedic Research, vol. 23, no. 5, pp. 1184–1190, 2005.

S. M. Imler, A. N. Doshi, and M. E. Levenston, “Combined effects of growth factors and static mechanical compression on meniscus explant biosynthesis,” Osteoarthritis and Cartilage, vol. 12, no. 9, pp. 736–744, 2004.

R. F. MacBarb, E. A. Makris, J. C. Hu, and K. A. Athanasiou, “A chondroitinase-ABC and TGF-β1 treatment regimen for enhancing the mechanical properties of tissue-engineered fibrocartilage,” Acta Biomaterialia, vol. 9, no. 1, pp. 4626–4634, 2013.

D. J. Huey and K. A. Athanasiou, “Maturational growth of self-assembled, functional menisci as a result of TGF-β1 and enzymatic chondroitinase-ABC stimulation,” Biomaterials, vol. 32, no. 8, pp. 2052–2058, 2011.

N. J. Gunja, R. K. Uthamanthil, and K. A. Athanasiou, “Effects of TGF-β1 and hydrostatic pressure on meniscus cell-seeded scaffolds,” Biomaterials, vol. 30, no. 4, pp. 565–573, 2009.

J. M. Zaleskas, B. Kinner, T. M. Freyman, I. V. Yannas, L. J. Gibson, and M. Spector, “Growth factor regulation of smooth muscle actin expression and contraction of human articular chondrocytes and meniscal cells in a collagen-GAG matrix,” Experimental Cell Research, vol. 270, no. 1, pp. 21–31, 2001.

W. Hui, A. D. Rowan, and T. Cawston, “Modulation of the expression of matrix metalloproteinase and tissue inhibitors of metalloproteinases by TGF-β1 and IGF-1 in primary human articular and bovine nasal chondrocytes stimulated with TNF-α,” Cytokine, vol. 16, no. 1, pp. 31–35, 2001.

N. Takahashi, K. Rieneck, P. M. van der Kraan et al., “Elucidation of IL-1/TGF-β interactions in mouse chondrocyte cell line by genome-wide gene expression1,” Osteoarthritis and Cartilage, vol. 13, no. 5, pp. 426–438, 2005.

Y. I. Kim, J.-S. Ryu, J. E. Yeo et al., “Overexpression of TGF-β1 enhances chondrogenic differentiation and proliferation of human synovium-derived stem cells,” Biochemical and Biophysical Research Communications, vol. 450, no. 4, pp. 1593–1599, 2014.

H. Jian, X. Shen, I. Liu, M. Semenov, X. He, and X. F. Wang, “Smad3-dependent nuclear translocation of beta-catenin is required for TGF-beta1-induced proliferation of bone marrow-derived adult human mesenchymal stem cells,” Genes & Development, vol. 20, no. 6, pp. 666–674, 2006.

E. Augustyniak, T. Trzeciak, M. Richter, J. Kaczmarczyk, and W. Suchorska, “The role of growth factors in stem cell-directed chondrogenesis: a real hope for damaged cartilage regeneration,” International Orthopaedics, vol. 39, no. 5, pp. 995–1003, 2015.

Q. O. Tang, K. Shakib, M. Heliotis et al., “TGF-β3: a potential biological therapy for enhancing chondrogenesis,” Expert Opinion on Biological Therapy, vol. 9, no. 6, pp. 689–701, 2009.

P. C. Yaeger, T. L. Masi, J. L. B. De Ortiz, F. Binette, R. Tubo, and J. M. McPherson, “Synergistic action of transforming growth factor-β and insulin-like growth factor-I induces expression of type II collagen and aggrecan genes in adult human articular chondrocytes,” Experimental Cell Research, vol. 237, no. 2, pp. 318–325, 1997.

H. Diao, J. Wang, C. Shen et al., “Improved cartilage regeneration utilizing mesenchymal stem cells in TGF-beta1 gene-activated scaffolds.,” Tissue Engineering Part A, vol. 15, no. 9, pp. 2687–2698, 2009.

H. Fan, H. Tao, Y. Wu, Y. Hu, Y. Yan, and Z. Luo, “TGF-β3 immobilized PLGA-gelatin/chondroitin sulfate/hyaluronic acid hybrid scaffold for cartilage regeneration,” Journal of Biomedical Materials Research Part A, vol. 95, no. 4, pp. 982–992, 2010.

A. I. Bochyńska, G. Hannink, R. Verhoeven, D. W. Grijpma, and P. Buma, “The effect of tissue surface modification with collagenase and addition of TGF-β3 on the healing potential of meniscal tears repaired with tissue glues in vitro,” Journal of Materials Science: Materials in Medicine, vol. 28, no. 1, article no. 22, 2017.

C. H. Lee, S. A. Rodeo, L. A. Fortier, C. Lu, C. Erisken, and J. J. Mao, “Protein-releasing polymeric scaffolds induce fibrochondrocytic differentiation of endogenous cells for knee meniscus regeneration in sheep,” Science Translational Medicine, vol. 6, no. 266, article 266ra171, 2014.

J. Gouttenoire, U. Valcourt, M.-C. Ronzière, E. Aubert-Foucher, F. Mallein-Gerin, and D. Herbage, “Modulation of collagen synthesis in normal and osteoarthritic cartilage,” Biorheology, vol. 41, no. 3-4, pp. 535–542, 2004.

E. N. B. Davidson, E. L. Vitters, P. L. E. M. van Lent, F. A. J. van de Loo, W. B. van den Berg, and P. M. van der Kraan, “Elevated extracellular matrix production and degradation upon bone morphogenetic protein-2 (BMP-2) stimulation point toward a role for BMP-2 in cartilage repair and remodeling,” Arthritis Research & Therapy, vol. 9, no. 5, article no. R102, 2007.

H. Minehara, K. Urabe, K. Naruse et al., “A new technique for seeding chondrocytes onto solvent-preserved human meniscus using the chemokinetic effect of recombinant human bone morphogenetic protein-2,” Cell and Tissue Banking, vol. 12, no. 3, pp. 199–207, 2011.

A. M. Elshaier, A. A. Hakimiyan, L. Rappoport, D. C. Rueger, and S. Chubinskaya, “Effect of interleukin-1β on osteogenic protein 1-induced signaling in adult human articular chondrocytes,” Arthritis & Rheumatology, vol. 60, no. 1, pp. 143–154, 2009.

K. Huch, B. Wilbrink, J. Flechtenmacher et al., “Effects of recombinant human osteogenic protein 1 on the production of proteoglycan, prostaglandin E2, and interleukin-1 receptor antagonist by human articular chondrocytes cultured in the presence of interleukin-1β,” Arthritis & Rheumatology, vol. 40, no. 12, pp. 2157–2161, 1997.

F. Forriol, P. Ripalda, J. Duart, R. Esparza, and A. R. Gortazar, “Meniscal repair possibilities using bone morphogenetic protein-7,” Injury, vol. 45, no. 4, pp. S15–S21, 2014.

N. Ozeki, T. Muneta, H. Koga et al., “Transplantation of achilles tendon treated with bone morphogenetic protein 7 promotes meniscus regeneration in a rat model of massive meniscal defect,” Arthritis & Rheumatology, vol. 65, no. 11, pp. 2876–2886, 2013.

I. Sekiya, B. L. Larson, J. T. Vuoristo, R. L. Reger, and D. J. Prockop, “Comparison of effect of BMP-2, -4, and -6 on in vitro cartilage formation of human adult stem cells from bone marrow stroma,” Cell and Tissue Research, vol. 320, no. 2, pp. 269–276, 2005.

S. Chubinskaya, D. Segalite, D. Pikovsky, A. A. Hakimiyan, and D. C. Rueger, “Effects induced by BMPS in cultures of human articular chondrocytes: Comparative studies,” Growth Factors, vol. 26, no. 5, pp. 275–283, 2008.

C. Miyamoto, T. Matsumoto, K. Sakimura, and H. Shindo, “Osteogenic protein-1 with transforming growth factor-β1: Potent inducer of chondrogenesis of synovial mesenchymal stem cells in vitro,” Journal of Orthopaedic Science, vol. 12, no. 6, pp. 555–561, 2007.

N. Shintani and E. B. Hunziker, “Chondrogenic differentiation of bovine synovium: Bone morphogenetic proteins 2 and 7 and transforming growth factor β1 induce the formation of different types of cartilaginous tissue,” Arthritis & Rheumatology, vol. 56, no. 6, pp. 1869–1879, 2007.

A. Hiraide, N. Yokoo, K.-Q. Xin et al., “Repair of articular cartilage defect by intraarticular administration of basic fibroblast growth factor gene, using adeno-associated virus vector,” Human Gene Therapy, vol. 16, no. 12, pp. 1413–1421, 2005.

C. Kasemkijwattana, J. Menetrey, H. Goto, C. Niyibizi, F. H. Fu, and J. Huard, “The use of growth factors, gene therapy and tissue engineering to improve meniscal healing,” Materials Science and Engineering C: Materials for Biological Applications, vol. 13, no. 1-2, pp. 19–28, 2000.

K. Stewart, M. Pabbruwe, S. Dickinson, T. Sims, A. P. Hollander, and J. B. Chaudhuri, “The effect of growth factor treatment on meniscal chondrocyte proliferation and differentiation on polyglycolic acid scaffolds,” Tissue Engineering Part A, vol. 13, no. 2, pp. 271–280, 2007.

M. Cucchiarini, S. Schetting, E. F. Terwilliger, D. Kohn, and H. Madry, “rAAV-mediated overexpression of FGF-2 promotes cell proliferation, survival, and α-SMA expression in human meniscal lesions,” Gene Therapy, vol. 16, no. 11, pp. 1363–1372, 2009.

P. A. Sotiropoulou, S. A. Perez, M. Salagianni, C. N. Baxevanis, and M. Papamichail, “Characterization of the optimal culture conditions for clinical scale production of human mesenchymal stem cells,” Stem Cells, vol. 24, no. 2, pp. 462–471, 2006.

C. T. Buckley and D. J. Kelly, “Expansion in the presence of FGF-2 enhances the functional development of cartilaginous tissues engineered using infrapatellar fat pad derived MSCs,” Journal of the Mechanical Behavior of Biomedical Materials, vol. 11, pp. 102–111, 2012.

I. Martin, A. Muraglia, G. Campanile, R. Cancedda, and R. Quarto, “Fibroblast growth factor-2 supports ex vivo expansion and maintenance of osteogenic precursors from human bone marrow,” Endocrinology, vol. 138, no. 10, pp. 4456–4462, 1997.

A. B. Adesida, L. M. Grady, W. S. Khan, and T. E. Hardingham, “The matrix-forming phenotype of cultured human meniscus cells is enhanced after culture with fibroblast growth factor 2 and is further stimulated by hypoxia,” Arthritis Research & Therapy, vol. 8, article R61, 2006.

X. Li, H. S. An, M. Ellman et al., “Action of fibroblast growth factor-2 on the intervertebral disc,” Arthritis Research & Therapy, vol. 10, no. 2, article no. R48, 2008.

D. Sonal, “Prevention of IGF-1 and TGFβ stimulated type II collagen and decorin expression by bFGF and identification of IGF-1 mRNA transcripts in articular chondrocytes,” Matrix Biology, vol. 20, no. 4, pp. 233–242, 2001.

P. Muddasani, J. C. Norman, M. Ellman, A. J. Van Wijnen, and H.-J. Im, “Basic fibroblast growth factor activates the MAPK and NFκB pathways that converge on Elk-1 to control production of matrix metalloproteinase-13 by human adult articular chondrocytes,” The Journal of Biological Chemistry, vol. 282, no. 43, pp. 31409–31421, 2007.

R. F. Loeser, S. Chubinskaya, C. Pacione, and H.-J. Im, “Basic fibroblast growth factor inhibits the anabolic activity of insulin-like growth factor 1 and osteogenic protein 1 in adult human articular chondrocytes,” Arthritis & Rheumatology, vol. 52, no. 12, pp. 3910–3917, 2005.

T. Deng, S. Huang, S. Zhou, L. He, and Y. Jin, “Cartilage regeneration using a novel gelatin-chondroitin-hyaluronan hybrid scaffold containing bFGF-impregnated microspheres,” Journal of Microencapsulation, vol. 24, no. 2, pp. 163–174, 2007.

N. J. Gunja and K. A. Athanasiou, “Additive and synergistic effects of bFGF and hypoxia on leporine meniscus cell-seeded PLLA scaffolds,” Journal of Tissue Engineering and Regenerative Medicine, vol. 4, no. 2, pp. 115–122, 2010.

L. C. Ionescu, G. C. Lee, K. L. Huang, and R. L. Mauck, “Growth factor supplementation improves native and engineered meniscus repair in vitro,” Acta Biomaterialia, vol. 8, no. 10, pp. 3687–3694, 2012.

J. L. Puetzer, B. N. Brown, J. J. Ballyns, and L. J. Bonassar, “The effect of IGF-I on anatomically shaped tissue-engineered menisci,” Tissue Engineering Part: A, vol. 19, no. 11-12, pp. 1443–1450, 2013.

N. S. Tumia and A. J. Johnstone, “Regional regenerative potential of meniscal cartilage exposed to recombinant insulin-like growth factor-I in vitro,” The Journal of Bone & Joint Surgery (British Volume), vol. 86, no. 7, pp. 1077–1081, 2004.

L. Longobardi, L. O'Rear, S. Aakula et al., “Effect of IGF-I in the chondrogenesis of bone marrow mesenchymal stem cells in the presence or absence of TGF-β signaling,” Journal of Bone and Mineral Research, vol. 21, no. 4, pp. 626–636, 2006.

M. M. Bhargava, E. T. Attia, G. A. C. Murrell, M. M. Dolan, R. F. Warren, and J. A. Hannafin, “The effect of cytokines on the proliferation and migration of bovine meniscal cells,” The American Journal of Sports Medicine, vol. 27, no. 5, pp. 636–643, 1999.

H. Zhang, P. Leng, and J. Zhang, “Enhanced meniscal repair by overexpression of hIGF-1 in a full-thickness model,” Clinical Orthopaedics and Related Research, vol. 467, no. 12, pp. 3165–3174, 2009.

L. R. Goodrich, C. Hidaka, P. D. Robbins, C. H. Evans, and A. J. Nixon, “Genetic modification of chondrocytes with insulin-like growth factor-1 enhances cartilage healing in an equine model,” The Journal of Bone & Joint Surgery (British Volume), vol. 89, no. 5, pp. 672–685, 2007.

A. A. Worster, B. D. Brower-Toland, L. A. Fortier, S. J. Bent, J. Williams, and A. J. Nixon, “Chondrocytic differentiation of mesenchymal stem cells sequentially exposed to transforming growth factor-β1 in monolayer and insulin-like growth factor-I in a three-dimensional matrix,” Journal of Orthopaedic Research, vol. 19, no. 4, pp. 738–749, 2001.

I. Izal, P. Ripalda, C. A. Acosta, and F. Forriol, “In vitro healing of avascular meniscal injuries with fresh and frozen plugs treated with TGF-beta1 and IGF-1 in sheep,” International Journal of Clinical and Experimental Pathology, vol. 1, no. 5, pp. 426–434, 2008.

D. B. Fox, J. J. Warnock, A. M. Stoker, J. K. Luther, and M. Cockrell, “Effects of growth factors on equine synovial fibroblasts seeded on synthetic scaffolds for avascular meniscal tissue engineering,” Research in Veterinary Science, vol. 88, no. 2, pp. 326–332, 2010.

H.-J. Im, C. Pacione, S. Chubinskaya, A. J. Van Wijnen, Y. Sun, and R. F. Loeser, “Inhibitory effects of insulin-like growth factor-1 and osteogenic protein-1 on fibronectin fragment- and interleukin-1β-stimulated matrix metalloproteinase-13 expression in human chondrocytes,” The Journal of Biological Chemistry, vol. 278, no. 28, pp. 25386–25394, 2003.

W. Petersen, T. Pufe, C. Stärke et al., “The effect of locally applied vascular endothelial growth factor on meniscus healing: gross and histological findings,” Archives of Orthopaedic and Trauma Surgery, vol. 127, no. 4, pp. 235–240, 2007.

C. Hidaka, C. Ibarra, J. A. Hannafin et al., “Formation of vascularized meniscal tissue by combining gene therapy with tissue engineering,” Tissue Engineering Part A, vol. 8, no. 1, pp. 93–105, 2002.

W. He, Y.-J. Liu, Z.-G. Wang, Z.-K. Guo, M.-X. Wang, and N. Wang, “Enhancement of meniscal repair in the avascular zone using connective tissue growth factor in a rabbit model,” Chinese Medical Journal, vol. 124, no. 23, pp. 3968–3975, 2011.

T. Nishida, S. Kubota, S. Kojima et al., “Regeneration of defects in articular cartilage in rat knee joints by CCN2 (connective tissue growth factor),” Journal of Bone and Mineral Research, vol. 19, no. 8, pp. 1308–1319, 2004.

N. S. Tumia and A. J. Johnstone, “Platelet derived growth factor-AB enhances knee meniscal cell activity in vitro,” The Knee, vol. 16, no. 1, pp. 73–76, 2009.

K. Ishida, R. Kuroda, M. Miwa et al., “The regenerative effects of platelet-rich plasma on meniscal cells in vitro and its in vivo application with biodegradable gelatin hydrogel,” Tissue Engineering Part A, vol. 13, no. 5, pp. 1103–1112, 2007.

E. A. Makris, P. Hadidi, and K. A. Athanasiou, “The knee meniscus: structure-function, pathophysiology, current repair techniques, and prospects for regeneration,” Biomaterials, vol. 32, no. 30, pp. 7411–7431, 2011.

S. Font Tellado, E. R. Balmayor, and M. Van Griensven, “Strategies to engineer tendon/ligament-to-bone interface: Biomaterials, cells and growth factors,” Advanced Drug Delivery Reviews, vol. 94, pp. 126–140, 2015.

N. Bhardwaj, D. Devi, and B. B. Mandal, “Tissue-engineered cartilage: The crossroads of biomaterials, cells and stimulating factors,” Macromolecular Bioscience, vol. 15, no. 2, pp. 153–182, 2015.

L. A. Fortier, J. U. Barker, E. J. Strauss, T. M. McCarrel, and B. J. Cole, “The role of growth factors in cartilage repair,” Clinical Orthopaedics and Related Research, vol. 469, no. 10, pp. 2706–2715, 2011.

F. Forriol, “Growth factors in cartilage and meniscus repair,” Injury, vol. 40, pp. S12–S16, 2009.

X.-H. Feng and R. Derynck, “Specificity and versatility in TGF-β signaling through smads,” Annual Review of Cell and Developmental Biology, vol. 21, pp. 659–693, 2005.

M. Y. Wu and C. S. Hill, “TGF-β superfamily signaling in embryonic development and homeostasis,” Developmental Cell, vol. 16, no. 3, pp. 329–343, 2009.

C.-H. Heldin, K. Miyazono, and P. ten Dijke, “TGF-β signalling from cell membrane to nucleus through SMAD proteins,” Nature, vol. 390, no. 6659, pp. 465–471, 1997.

Y. Shi and J. Massagué, “Mechanisms of TGF-β signaling from cell membrane to the nucleus,” Cell, vol. 113, no. 6, pp. 685–700, 2003.

L. A. Poniatowski, P. Wojdasiewicz, R. Gasik, and D. Szukiewicz, “Transforming growth factor beta family: Insight into the role of growth factors in regulation of fracture healing biology and potential clinical applications,” Mediators of Inflammation, vol. 2015, Article ID 137823, 17 pages, 2015.

E. N. Blaney Davidson, P. M. van der Kraan, and W. B. van den Berg, “TGF-β and osteoarthritis,” Osteoarthritis and Cartilage, vol. 15, no. 6, pp. 597–604, 2007.

A. M. Mackay, S. C. Beck, J. M. Murphy, F. P. Barry, C. O. Chichester, and M. F. Pittenger, “Chondrogenic differentiation of cultured human mesenchymal stem cells from marrow,” Tissue Engineering Part A, vol. 4, no. 4, pp. 415–428, 1998.

A. T. Mehlhorn, H. Schmal, S. Kaiser et al., “Mesenchymal stem cells maintain TGF-β-mediated chondrogenic phenotype in alginate bead culture,” Tissue Engineering Part A, vol. 12, no. 6, pp. 1393–1403, 2006.

M. B. Mueller, M. Fischer, J. Zellner et al., “Hypertrophy in mesenchymal stem cell chondrogenesis: effect of TGF-β isoforms and chondrogenic conditioning,” Cells Tissues Organs, vol. 192, no. 3, pp. 158–166, 2010.

T. A. Ahmed and M. T. Hincke, “Mesenchymal stem cell-based tissue engineering strategies for repair of articular cartilage,” Histology and Histopathology, vol. 6, pp. 669–689, 29.

C. H. Lee, J. L. Cook, A. Mendelson, E. K. Moioli, H. Yao, and J. J. Mao, “Regeneration of the articular surface of the rabbit synovial joint by cell homing: a proof of concept study,” The Lancet, vol. 376, no. 9739, pp. 440–448, 2010.

A. L. McNulty and F. Guilak, “Integrative repair of the meniscus: Lessons from in vitro studies,” Biorheology, vol. 45, no. 3-4, pp. 487–500, 2008.

U. Freymann, M. Endres, U. Goldmann, M. Sittinger, and C. Kaps, “Toward scaffold-based meniscus repair: effect of human serum, hyaluronic acid and TGF-ß3 on cell recruitment and re-differentiation,” Osteoarthritis and Cartilage, vol. 21, no. 5, pp. 773–781, 2013.

H. M. van Beuningen, P. M. van der Kraan, O. J. Arntz, and W. B. van den Berg, “Transforming growth factor-β1 stimulates articular chondrocyte proteoglycan synthesis and induces osteophyte formation in the murine knee joint,” Laboratory Investigation, vol. 71, no. 2, pp. 279–290, 1994.

A. C. Bakker, F. A. J. van de Loo, H. M. van Beuningen et al., “Overexpression of active TGF-beta-1 in the murine knee joint: evidence for synovial-layer-dependent chondro-osteophyte formation,” Osteoarthritis and Cartilage, vol. 9, no. 2, pp. 128–136, 2001.

A. C. Carreira, G. G. Alves, W. F. Zambuzzi, M. C. Sogayar, and J. M. Granjeiro, “Bone morphogenetic proteins: structure, biological function and therapeutic applications,” Archives of Biochemistry and Biophysics, vol. 561, pp. 64–73, 2014.

J. M. Wozney and V. Rosen, “Bone morphogenetic protein and bone morphogenetic protein gene family in bone formation and repair,” Clinical Orthopaedics and Related Research, no. 346, pp. 26–37, 1998.

A. C. Carreira, F. H. Lojudice, E. Halcsik, R. D. Navarro, M. C. Sogayar, and J. M. Granjeiro, “Bone morphogenetic proteins: facts, challenges, and future perspectives,” Journal of Dental Research, vol. 93, no. 4, pp. 335–345, 2014.

J. Fan, Y. Gong, L. Ren, R. R. Varshney, D. Cai, and D.-A. Wang, “In vitro engineered cartilage using synovium-derived mesenchymal stem cells with injectable gellan hydrogels,” Acta Biomaterialia, vol. 6, no. 3, pp. 1178–1185, 2010.

D. N. Kim, Y. H. Joung, P. Darvin et al., “Methylsulfonylmethane enhances BMP-2-induced osteoblast differentiation in mesenchymal stem cells,” Molecular Medicine Reports, vol. 14, no. 1, pp. 460–466, 2016.

K. Lavery, P. Swain, D. Falb, and M. H. Alaoui-Ismaili, “BMP-2/4 and BMP-6/7 differentially utilize cell surface receptors to induce osteoblastic differentiation of human bone marrow-derived mesenchymal stem cells,” The Journal of Biological Chemistry, vol. 283, no. 30, pp. 20948–20958, 2008.

L. Dai, X. Hu, and X. Zhang, “Different tenogenic differentiation capacities of different mesenchymal stem cells in the presence of BMP-12,” Journal of Translational Medicine, vol. 13, article 200, 2015.

H. Nochi, H. S. Jin, J. Lou, H. D. Adkisson, W. J. Maloney, and K. A. Hruska, “Adenovirus mediated BMP-13 gene transfer induces chondrogenic differentiation of murine mesenchymal progenitor cells,” Journal of Bone and Mineral Research, vol. 19, no. 1, pp. 111–122, 2004.

U. G. Longo, M. Loppini, F. Forriol, G. Romeo, N. Maffulli, and V. Denaro, “Advances in meniscal tissue engineering,” Stem Cells International, vol. 2012, Article ID 420346, 7 pages, 2012.

C. Merrihew, S. Soeder, D. C. Rueger, K. E. Kuettner, and S. Chubinskaya, “Modulation of endogenous osteogenic protein-1 (OP-1) by interleukin-1 in adult human articular cartilage,” The Journal of Bone & Joint Surgery, vol. 85, no. 3, pp. 67–74, 2003.

S. Chubinskaya, L. Otten, S. Soeder et al., “Regulation of chondrocyte gene expression by osteogenic protein-1,” Arthritis Research & Therapy, vol. 13, no. 2, article no. R55, 2011.

J. Flechtenmacher, K. Huch, E. J.-M. A. Thonar et al., “Recombinant human osteogenic protein 1 is a potent stimulator of the synthesis of cartilage proteoglycans and collagens by human articular chondrocytes,” Arthritis & Rheumatology, vol. 39, no. 11, pp. 1896–1904, 1996.

Z. Fan, S. Chubinskaya, D. C. Rueger, B. Bau, J. Haag, and T. Aigner, “Regulation of anabolic and catabolic gene expression in normal and osteoarthritic adult human articular chondrocytes by osteogenic protein-1,” Clinical and Experimental Rheumatology, vol. 22, no. 1, pp. 103–106, 2004.

S. Chubinskaya, M. Hurtig, and D. C. Rueger, “OP-1/BMP-7 in cartilage repair,” International Orthopaedics, vol. 31, no. 6, pp. 773–781, 2007.

S. Scarfi, “Use of bone morphogenetic proteins in mesenchymal stem cell stimulation of cartilage and bone repair,” World Journal of Stem Cells, vol. 8, no. 1, pp. 1–12, 2016.

R. F. Loeser, C. A. Pacione, and S. Chubinskaya, “The combination of insulin-like growth factor 1 and osteogenic protein 1 promotes increased survival of and matrix synthesis by normal and osteoarthritic human articular chondrocytes,” Arthritis & Rheumatology, vol. 48, no. 8, pp. 2188–2196, 2003.

A. Beenken and M. Mohammadi, “The FGF family: biology, pathophysiology and therapy,” Nature Reviews Drug Discovery, vol. 8, no. 3, pp. 235–253, 2009.

D. M. Ornitz and P. J. Marie, “FGF signaling pathways in endochondral and intramembranous bone development and human genetic disease,” Genes & Development, vol. 16, no. 12, pp. 1446–1465, 2002.

S.-L. Chia, Y. Sawaji, A. Burleigh et al., “Fibroblast growth factor 2 is an intrinsic chondroprotective agent that suppresses ADAMTS-5 and delays cartilage degradation in murine osteoarthritis,” Arthritis & Rheumatology, vol. 60, no. 7, pp. 2019–2027, 2009.

T. L. Vincent, C. J. McLean, L. E. Full, D. Peston, and J. Saklatvala, “FGF-2 is bound to perlecan in the pericellular matrix of articular cartilage, where it acts as a chondrocyte mechanotransducer,” Osteoarthritis and Cartilage, vol. 15, no. 7, pp. 752–763, 2007.

L. I. Oliver, D. B. Rifkin, J. Gabrilove, M.-J. Hannocks, and E. L. Wilson, “Long-term culture of human bone marrow stromal cells in the presence of basic fibroblast growth factor,” Growth Factors, vol. 3, no. 3, pp. 231–236, 1990.

N. S. Tumia and A. J. Johnstone, “Promoting the proliferative and synthetic activity of knee meniscal fibrochondrocytes using basic fibroblast growth factor in vitro,” The American Journal of Sports Medicine, vol. 32, no. 4, pp. 915–920, 2004.

R. J. Webber, M. G. Harris, and A. J. Hough, “Cell culture of rabbit meniscal fibrochondrocytes: Proliferative and synthetic response to growth factors and ascorbate,” Journal of Orthopaedic Research, vol. 3, no. 1, pp. 36–42, 1985.

L. A. Solchaga, K. Penick, J. D. Porter, V. M. Goldberg, A. I. Caplan, and J. F. Welter, “FGF-2 enhances the mitotic and chondrogenic potentials of human adult bone marrow-derived mesenchymal stem cells,” Journal of Cellular Physiology, vol. 203, no. 2, pp. 398–409, 2005.

M. Rodrigues, L. G. Griffith, and A. Wells, “Growth factor regulation of proliferation and survival of multipotential stromal cells,” Stem Cell Research & Therapy, vol. 1, no. 4, article 32, 2010.

T. Cheng, C. Yang, N. Weber, H. T. Kim, and A. C. Kuo, “Fibroblast growth factor 2 enhances the kinetics of mesenchymal stem cell chondrogenesis,” Biochemical and Biophysical Research Communications, vol. 426, no. 4, pp. 544–550, 2012.

M. B. Ellman, H. S. An, P. Muddasani, and H.-J. Im, “Biological impact of the fibroblast growth factor family on articular cartilage and intervertebral disc homeostasis,” Gene, vol. 420, no. 1, pp. 82–89, 2008.

M. B. Ellman, D. Yan, K. Ahmadinia, D. Chen, H. S. An, and H. J. Im, “Fibroblast growth factor control of cartilage homeostasis,” Journal of Cellular Biochemistry, vol. 114, no. 4, pp. 735–742, 2013.

A. Inoue, K. A. Takahashi, Y. Arai et al., “The therapeutic effects of basic fibroblast growth factor contained in gelatin hydrogel microspheres on experimental osteoarthritis in the rabbit knee,” Arthritis & Rheumatism, vol. 54, no. 1, pp. 264–270, 2006.

S. Miot, P. S. de Freitas, D. Wirz et al., “Cartilage tissue engineering by expanded goat articular chondrocytes,” Journal of Orthopaedic Research, vol. 24, no. 5, pp. 1078–1085, 2006.

N. Miyakoshi, M. Kobayashi, K. Nozaka, K. Okada, Y. Shimada, and E. Itoi, “Effects of intraarticular administration of basic fibroblast growth factor with hyaluronic acid on osteochondral defects of the knee in rabbits,” Archives of Orthopaedic and Trauma Surgery, vol. 125, no. 10, pp. 683–692, 2005.

E. E. Moore, A. M. Bendele, D. L. Thompson et al., “Fibroblast growth factor-18 stimulates chondrogenesis and cartilage repair in a rat model of injury-induced osteoarthritis,” Osteoarthritis and Cartilage, vol. 13, no. 7, pp. 623–631, 2005.

M. B. Schmidt, E. H. Chen, and S. E. Lynch, “A review of the effects of insulin-like growth factor and platelet derived growth factor on in vivo cartilage healing and repair,” Osteoarthritis and Cartilage, vol. 14, no. 5, pp. 403–412, 2006.

P. Buma, N. N. Ramrattan, T. G. Van Tienen, and R. P. H. Veth, “Tissue engineering of the meniscus,” Biomaterials, vol. 25, no. 9, pp. 1523–1532, 2004.

J. A. Martin, S. M. Ellerbroek, and J. A. Buckwalter, “Age-related decline in chondrocyte response to insulin-like growth factor-I: The role of growth factor binding proteins,” Journal of Orthopaedic Research, vol. 15, no. 4, pp. 491–498, 1997.

R. F. Loeser, G. Shanker, C. S. Carlson, J. F. Gardin, B. J. Shelton, and W. E. Sonntag, “Reduction in the chondrocyte response to insulin-like growth factor 1 in aging and osteoarthritis: Studies in a non-human primate model of naturally occurring disease,” Arthritis & Rheumatology, vol. 43, no. 9, pp. 2110–2120, 2000.

J. Schalkwijk, L. A. B. Joosten, W. B. Van Den Berg, and L. B. A. Van De Putte, “Chondrocyte nonresponsiveness to insulin-like growth factor 1 in experimental arthritis,” Arthritis & Rheumatology, vol. 32, no. 7, pp. 894–900, 1989.

S. Doré, J. Pelletier, J. A. Dibattista, G. Tardif, P. Brazeau, and J. Martel‐Pelletier, “Human Osteoarthritic Chondrocytes Possess an Increased Number of Insulin‐Like Growth Factor 1 Binding Sites but are Unresponsive to its Stimulation,” Arthritis & Rheumatism, vol. 37, no. 2, pp. 253–263, 1994.

S. Chubinskaya, A. Hakimiyan, C. Pacione et al., “Synergistic effect of IGF-1 and OP-1 on matrix formation by normal and OA chondrocytes cultured in alginate beads,” Osteoarthritis and Cartilage, vol. 15, no. 4, pp. 421–430, 2007.

W. Petersen, T. Pufe, C. Stärke et al., “Locally applied angiogenic factors—a new therapeutic tool for meniscal repair,” Annals of Anatomy, vol. 187, no. 5-6, pp. 509–519, 2005.

L. Brass, “Understanding and evaluating platelet function,” American Society of Hematology. Education Program, vol. 2010, pp. 387–396, 2010.

J. Zellner, M. Mueller, A. Berner et al., “Role of mesenchymal stem cells in tissue engineering of meniscus,” Journal of Biomedical Materials Research Part A, vol. 94, no. 4, pp. 1150–1161, 2010.

H. Huang, H. Xu, and J. Zhao, “A novel approach for meniscal regeneration using kartogenin-treated autologous tendon graft,” The American Journal of Sports Medicine, vol. 45, no. 14, pp. 3289–3297, 2017.

X. Hu, Y. Wang, Y. Tan et al., “A Difunctional Regeneration Scaffold for Knee Repair based on Aptamer-Directed Cell Recruitment,” Advanced Materials, vol. 29, no. 15, Article ID 1605235, 2017.

H. Huang, X. Zhang, X. Hu et al., “A functional biphasic biomaterial homing mesenchymal stem cells for invivo cartilage regeneration,” Biomaterials, vol. 35, no. 36, pp. 9608–9619, 2014.

E. Matsumoto, T. Furumatsu, T. Kanazawa, M. Tamura, and T. Ozaki, “ROCK inhibitor prevents the dedifferentiation of human articular chondrocytes,” Biochemical and Biophysical Research Communications, vol. 420, no. 1, pp. 124–129, 2012.

H.-C. Chou, L.-T. Huang, T.-F. Yeh, and C.-M. Chen, “Rho-kinase inhibitor Y-27632 attenuates pulmonary hypertension in hyperoxia-exposed newborn rats,” Acta Pharmacologica Sinica, vol. 34, no. 10, pp. 1310–1316, 2013.

M. D. Kofron and C. T. Laurencin, “Orthopaedic applications of gene therapy,” Current Gene Therapy, vol. 5, no. 1, pp. 37–61, 2005.

T. N. Vo, F. K. Kasper, and A. G. Mikos, “Strategies for controlled delivery of growth factors and cells for bone regeneration,” Advanced Drug Delivery Reviews, vol. 64, no. 12, pp. 1292–1309, 2012.

M. Cucchiarini, A. L. McNulty, R. L. Mauck, L. A. Setton, F. Guilak, and H. Madry, “Advances in combining gene therapy with cell and tissue engineering-based approaches to enhance healing of the meniscus,” Osteoarthritis and Cartilage, vol. 24, no. 8, pp. 1330–1339, 2016.

C. H. Evans and J. Huard, “Gene therapy approaches to regenerating the musculoskeletal system,” Nature Reviews Rheumatology, vol. 11, no. 4, pp. 234–242, 2015.

H. Goto, F. D. Shuler, C. Niyibizi, F. H. Fu, P. D. Robbins, and C. H. Evans, “Gene therapy for meniscal injury: Enhanced synthesis of proteoglycan and collagen by meniscal cells transduced with a TGFβ1 gene,” Osteoarthritis and Cartilage, vol. 8, no. 4, pp. 266–271, 2000.

H.-P. Lee, A. Rey-Rico, M. Cucchiarini, and H. Madry, “Nonviral gene transfer into human meniscal cells. Part II: Effect of three-dimensional environment and overexpression of human fibroblast growth factor 2,” International Orthopaedics, vol. 38, no. 9, pp. 1931–1936, 2014.

A. F. Steinert, G. D. Palmer, R. Capito et al., “Genetically enhanced engineering of meniscus tissue using ex vivo delivery of transforming growth factor-β1 complementary deoxyribonucleic acid,” Tissue Engineering Part A, vol. 13, no. 9, pp. 2227–2237, 2007.

H. Madry, M. Cucchiarini, G. Kaul, D. Kohn, E. F. Terwilliger, and S. B. Trippel, “Menisci are efficiently transduced by recombinant adeno-associated virus vectors in vitro and in vivo,” The American Journal of Sports Medicine, vol. 32, no. 8, pp. 1860–1865, 2004.

M. Cucchiarini, K. Schmidt, J. Frisch, D. Kohn, and H. Madry, “Overexpression of TGF-β via rAAV-Mediated Gene Transfer Promotes the Healing of Human Meniscal Lesions Ex Vivo on Explanted Menisci,” The American Journal of Sports Medicine, vol. 43, no. 5, pp. 1197–1205, 2015.

S. Elsler, S. Schetting, G. Schmitt, D. Kohn, H. Madry, and M. Cucchiarini, “Effective, safe nonviral gene transfer to preserve the chondrogenic differentiation potential of human mesenchymal stem cells,” The Journal of Gene Medicine, vol. 14, no. 7, pp. 501–511, 2012.

H.-N. Zhang, P. Leng, Y.-Z. Wang, and J. Zhang, “Treating human meniscal fibrochondrocytes with hIGF-1 gene by liposome,” Clinical Orthopaedics and Related Research, vol. 467, no. 12, pp. 3175–3182, 2009.

H. Goto, F. D. Shuler, C. Lamsam et al., “Transfer of LacZ marker gene to the meniscus,” The Journal of Bone & Joint Surgery, vol. 81, no. 7, pp. 918–925, 1999.

V. Martinek, A. Usas, D. Pelinkovic, P. Robbins, F. H. Fu, and J. Huard, “Genetic engineering of meniscal allografts,” Tissue Engineering Part A, vol. 8, no. 1, pp. 107–117, 2002.

T. G. Gerich, S. Ghivizani, F. H. Fu, P. D. Robbins, and C. H. Evans, “Gene transfer into the patellar tendon of rabbits: a preliminary study of locoregional expression of growth factors,” Wiener klinische Wochenschrift, vol. 109, no. 11, pp. 384–389, 1997.

J. M. Brunger, N. P. T. Huynh, C. M. Guenther et al., “Scaffold-mediated lentiviral transduction for functional tissue engineering of cartilage,” Proceedings of the National Acadamy of Sciences of the United States of America, vol. 111, no. 9, pp. E798–E806, 2014.

K. A. Glass, J. M. Link, J. M. Brunger, F. T. Moutos, C. A. Gersbach, and F. Guilak, “Tissue-engineered cartilage with inducible and tunable immunomodulatory properties,” Biomaterials, vol. 35, no. 22, pp. 5921–5931, 2014.

M. Cucchiarini, M. Ekici, S. Schetting, D. Kohn, and H. Madry, “Metabolic activities and chondrogenic differentiation of human mesenchymal stem cells following recombinant adeno-associated virus-mediated gene transfer and overexpression of fibroblast growth factor 2,” Tissue Engineering Part A, vol. 17, no. 15-16, pp. 1921–1933, 2011.

T. P. Lozito, P. G. Alexander, H. Lin, R. Gottardi, A. W.-M. Cheng, and R. S. Tuan, “Three-dimensional osteochondral microtissue to model pathogenesis of osteoarthritis,” Stem Cell Research & Therapy, vol. 4, no. 1, article no. S6, 2013.

A. B. Adesida, L. M. Grady, W. S. Khan, S. J. Millward-Sadler, D. M. Salter, and T. E. Hardingham, “Human meniscus cells express hypoxia inducible factor-1α and increased SOX9 in response to low oxygen tension in cell aggregate culture,” Arthritis Research & Therapy, vol. 9, article R69, 2007.

N. J. Gunja and K. A. Athanasiou, “Effects of co-cultures of meniscus cells and articular chondrocytes on PLLA scaffolds,” Biotechnology and Bioengineering, vol. 103, no. 4, pp. 808–816, 2009.

X. Cui, A. Hasegawa, M. Lotz, and D. D'Lima, “Structured three-dimensional co-culture of mesenchymal stem cells with meniscus cells promotes meniscal phenotype without hypertrophy,” Biotechnology and Bioengineering, vol. 109, no. 9, pp. 2369–2380, 2012.