Mesenchymal stem cells (MSCs) are defined as pluripotent cells found in numerous human tissues, including bone marrow and adipose tissue. Such MSCs, isolated from bone marrow and adipose tissue, have been shown to differentiate into bone and cartilage, along with other types of tissues. Therefore, MSCs represent a promising new therapy in regenerative medicine. The initial treatment of meniscus tear of the knee is managed conservatively with nonsteroidal anti-inflammatory drugs and physical therapy. When such conservative treatment fails, an arthroscopic resection of the meniscus is necessary. However, the major drawback of the meniscectomy is an early onset of osteoarthritis. Therefore, an effective and noninvasive treatment for patients with continuous knee pain due to damaged meniscus has been sought. Here, we present a review, highlighting the possible regenerative mechanisms of damaged meniscus with MSCs (especially adipose tissue-derived stem cells (ASCs)), along with a case of successful repair of torn meniscus with significant reduction of knee pain by percutaneous injection of autologous ASCs into an adult human knee.
The menisci are two semilunar, fibrocartilaginous disks located between the medial and lateral articular surfaces of the femur and tibia in each knee. Their key functions are (i) the transfer of weight, (ii) absorption of shock during dynamic movements of the knee, and (iii) protecting the cartilage in the joint [
MSCs were first identified and isolated from bone marrow (BM) in the late 1960s [
According to ISCT, the criteria for identification of MSCs are as follows: (i) MSCs must adhere to plastic under standard culture conditions; (ii) MSCs must express the surface molecules CD105, CD73, and CD90 and lack expression of CD45, CD34, CD14 or CD11b, CD79
Human ASCs were first discovered and identified in the early 2000s in the form of stromal vascular fraction (SVF) and shown to possess self-renewal capacity and the capability to differentiate into adipocytes, osteoblasts, and chondrocytes [
Currently, ASCs have been shown to differentiate toward cells that are mesodermal and nonmesodermal in origin. In 2005, Brzoska et al. reported
In case of meniscus repair, a few studies showing the direct differentiation of MSCs into meniscal cells were reported in animal models. Mizuno et al. reported that synovium-derived MSCs were able to attach to the meniscal defect of a rat and differentiate into cartilage cells [
Potential mechanisms for regeneration and repair of damaged meniscus by MSCs (especially ASCs) can include the following: (i) transplanted cells differentiate into de novo tissue [
Although the potential for ASCs to differentiate into various tissues of the body seems to be limitless, the ability of ASCs to promote tissue regeneration and repair may also depend on their paracrine effects. ASCs have the capability to secrete various growth factors that can modulate host tissue environment [
When immunity has been oversurmounted, lymphocytes and mononuclear cells can damage the host tissue. ASCs can promote tissue repair and regeneration through immune-suppressing lymphocytes and peripheral blood mononuclear cells, thus preventing overinflammation [
In case of meniscal repair, implanted BM-derived MSCs can produce factors that inhibit scarring (fibrosis) and apoptosis, promote angiogenesis, and stimulate host progenitors to divide and differentiate into functional regenerative units [
Although it is not clear, at this time, if paracrine effects via neovascularization and immunosuppression are involved in regeneration and repair of meniscus, it is very possible that one of the many growth factors excreted by ASCs can have a profound trophic, paracrine effect on the surrounding intact meniscus.
Understanding platelet physiology has led to the concept of utilizing platelet growth factors in natural regenerative therapies. A simple centrifugation system can isolate and concentrate platelets from an autologous blood sample, producing platelet-rich plasma (PRP). PRP contains a high concentration of autologous growth factors. With activation, platelet degranulation is induced and a concentrated pool of autologous growth factors can be released to injured site to augment natural regenerative pathways [
Clinical applications of PRP have so far demonstrated encouraging therapeutic results. Mishra and Pavelko reported greater than 90% reduction in elbow pain with PRP injections of chronic elbow tendinosis [
Growth factors in PRP have been shown to enhance the healing properties of the inner avascular part of rabbit meniscal cells and to enhance the biological activities of the meniscal cells for meniscal tissue regeneration [
Potential mechanisms for possible regeneration of the damaged meniscus by PRP can include the following: (i) platelet growth factors can be released to damaged meniscus to augment natural regenerative pathways; (ii) the released growth factors from PRP have a chemotactic and mitogenic effect on MSCs; (iii) PRP can be a potential contributor in initiating angiogenesis; and/or (iv) PRP has been shown to stimulate stem cells to proliferate as well as differentiate.
In addition to PRP growth factors, various other elements can affect MSC differentiation in their natural environment [
According to Korean law (Rules and Regulations of the Korean Food and Drug Administration), this study does not need approval by ethics and science committees [
The inclusion criteria, exclusion criteria, and outcome endpoints are listed in Tables
Inclusion criteria.
Description | |
---|---|
(1) MRI evidence of meniscal tear | |
(2) Orthopedic evaluation that determined that patient was a candidate for an arthroscopic meniscectomy | |
(3) Either male or female | |
(4) Under 60 years of age | |
(5) An unwillingness to proceed with arthroscopic resection of the meniscus | |
(6) The failure of conservative management | |
(7) Ongoing pain |
Exclusion criteria.
Description | |
---|---|
(1) Active inflammatory or connective tissue disease thought to affect the patient's pain (i.e., lupus, rheumatoid arthritis, fibromyalgia) | |
(2) Active endocrine disorder that might affect the patient's pain (i.e., hypothyroidism, diabetes) | |
(3) Active neurological disorder that might affect the patient's pain (i.e., peripheral neuropathy, multiple sclerosis) | |
(4) Active cardiac disease |
Outcome endpoints (obtained at three months after treatment).
Description | |
---|---|
(1) Pre- and posttreatment VAS (visual analog scale) walking index | |
(2) Pre- and posttreatment functional rating index | |
(3) Pre- and posttreatment range of motion | |
(4) Pre- and posttreatment MRI (magnetic resonance imaging) |
For pain score, functional rating index, visual analog scale (VAS), physical therapy (PT), and range of motion (ROM) were determined as previously described [
The patient was restricted from taking steroids, aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and Asian herbal medications for one week prior to the procedure.
In the operating room, approximately 40 mL of packed adipose tissue was obtained by liposuction of the subcutaneous layer of the lower abdominal area using sterile techniques [
ASCs were extracted through the use of digestive enzymes (0.07% type 1 collagenase; Adilase, Worthington, Lakewood, NJ, USA) and centrifugation (500 g) [
After the left knee was cleaned with 5% povidone-iodine (Choongwae Pharmaceutical Co., Seoul, Korea) and draped in a sterile fashion, the injection site was anesthetized with 2% lidocaine (Daehan Pharmaceutical Co., Gyeonggido, Korea). On the day of liposuction, the ASC mixture (15 mL) was injected into the medial Tibiofemoral joint and into the medial inferior retropatellar joint on the day of liposuction with a 20-gauge, 1 1/2-inch needle under ultrasonic guidance. On the third and seventh day after the initial injection, another dose of PRP with CaCl2 and hyaluronic acid (1 mL) was injected in the same fashion as the first day. On the fourteenth day after the initial injection, a low-dose (254.8 nmol/L) dexamethasone (Huons, Chungbuk, Korea) was added to PRP with CaCl2. On day 28, the last dose of PRP with CaCl2 was injected.
The patient was followed up with telephone questionnaires every six months at 6, 12, and 18 months. Each time, the patient was asked the following questions. (i) Was the symptom improvement persistent? (ii) Did you experience any complications (e.g., infection, illness) you believe may be due to the procedure? If yes or maybe, please explain. (iii) Have you been diagnosed with any form of cancer since the procedure? If yes, please explain.
A 32-year-old female has been experiencing left knee pain for the last two years prior to the office visit. The patient denied any history of significant trauma, except exercising on a treadmill. On the day of the initial evaluation, she reported moderate pain (visual analog scale (VAS) score of 5) on rest and increased pain when walking (VAS walking index (VWI) of 7; Figure
(a) Outcome of pain measurements. (b) Range of motion from the patient. VAS is visual analog scale and error bars indicate standard deviations (
MRI sagittal sequential T2 views of the knee. Pretreatment MRI scans ((a) (sequential image: 5/20) and (c) (6/20)) show a tear (arrow) within the posterior horn of the medial meniscus. Posttreatment MRI scans at three months ((b) (5/20) and (d) (6/20)) indicate the healed meniscus (triangle) that has been repaired by ASCs mixture-based treatment.
MRI coronal sequential T2 views of the knee. Pretreatment MRI scans ((a) (sequential image: 14/20) and (c) (15/20)) show a tear (arrow) within the posterior horn of the medial meniscus. Posttreatment MRI scans at three months ((b) (14/20) and (d) (15/20)) indicate the healed meniscus (triangle) that has been restored by ASCs mixture-based treatment.
When such conservative treatment fails, an arthroscopic resection of the meniscus is necessary [
From June 2009, autologous, noncultured ASCs can now be used as a source of MSCs in Korea [
After obtaining autologous ASCs and preparing PRP as previously described [
The patient was offered the sixth, twelfth, and eighteenth month postprocedure MRIs, but she refused to undergo postprocedure MRIs due to symptom improvement and financial reasons. Therefore, the longer-term (more than three months) followups were conducted based on telephone questionnaires. Until 18 months, her symptom improvement was persistent and she did not report any serious side effects (cancer or any complications). A recent report supports this result [
A diagnostic MRI of the knee was performed on the patient before ASC mixture-based treatment. Consequently, posttreatment MRIs were performed to compare pre- and posttreatment images. The MRI T2 sequence was used for its ability to show bony anatomy. Due to slight differences in patient positioning and slight movement of the patient during the MRI procedures, there was some difficulty in capturing the exact and identical treatment location. However, the pre-and posttreatment MRI results can be compared with sequential views to compensate for any possible errors [
In the clinical result of ASC mixture application, significant MRI signal changes were apparent in the T2 views of the knee along injection sites (the medial Tibiofemoral joint and the medial inferior retropatellar joint). These significant signal changes can be interpreted as signs of persistent and restored meniscus. Due to reduction in the knee pain, the patient was reluctant to undergo a knee meniscal biopsy to determine the true nature of the cartilage-like tissue. Although the true nature of the restored tissue is unclear, the torn meniscus is believed to be restored, based on previous studies showing cartilage recovery using mesenchymal stem cells (MSCs) in patients with osteonecrosis, osteoarthritis, and chondromalacia patellae [
With regard to the mechanism of the possible regenerative meniscal repair, there are few plausible possibilities: (i) direct differentiation of the stem cells (e.g., ASCs) [
It has been estimated that approximately 400,000 ASCs are contained in 1 mL of adipose tissue [
Although this clinical report was not a randomized and controlled trial, the key clinical feature of this clinical result is demonstrating the possible availability of potentially effective and noninvasive treatment in patients with continuous knee pain due to meniscus tear. In addition, although there was no placebo (ASC-free) group, the patient had received PRP and hyaluronic acid injections without ASCs. This treatment did not provide any clinical improvement. The patient experienced significant reduction of the knee pain only after percutaneous injection of ASC mixture.
The authors have no conflict of interests.
This work was supported by the National Research Lab Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (no. 2011-0027928); the Marine and Extreme Genome Research Center Program funded by Ministry of Oceans and Fisheries, Republic of Korea; and the Next Generation BioGreen 21 Program (no. PJ009082) of Rural Development Administration in Republic of Korea. The authors appreciate the SVF extraction and consultation of ED Co., Ltd. (SCELDIS, Republic of Korea). Jaewoo Pak and Jung Hun Lee worked equally on this paper.