We applied in the previous study miRNA microarray screening analysis to identify several differentially expressed miRNAs, including miR-183 in normal, eutopic, and ectopic endometrium. Knockdown of
miR-183 expression induced the invasiveness and inhibition of apoptosis in endometrial stromal cells. The current study aims to identify the miR-183 targets with relevance to cell functions in endometrial stromal cells, to verify the interaction of miR-183 with its target genes, and to confirm the role of miR-183 in the process of endometriosis. Using microarray analysis, we identified 27 differentially expressed genes (19 were upregulated and 8 downregulated), from which we selected 4 downregulated genes (ITGB1, AMIGO2, VAV3, and PSEN2) based on GO databases for functional analysis and significant pathway analysis. Western blotting analyses showed that integrin
Affecting 6–10% of women at reproductive age, endometriosis is a common chronic gynecological disorder associated with infertility, severe pelvic pain, and menstrual disorders [
MicroRNAs (miRNAs) are small, noncoding regulatory RNAs that regulate the stability and translation of mRNAs by inhibiting ribosome functions, deadenylating the poly(A) tail, and degrading target mRNA [
A single microRNA molecule is able to modulate multiple target genes; thus it is involved in multiple cell functions including proliferation, invasiveness, and differentiation [
In a previous study, we identified several differentially expressed miRNAs among normal, eutopic, and ectopic endometrium. MiR-183 was found to be the most downregulated miRNA in both the ectopic and eutopic tissues compared to normal endometrium. Functional studies indicated that miR-183 may contribute to endometrial stromal cell apoptosis and impose a negative regulatory impact on cell invasiveness, but it has no effect on endometrial stromal cell proliferation. The study suggested that aberrant miR-183 expression may be involved in the development and progression of endometriosis [
In the present study, we aim to identify the functional targets of miR-183 using an overexpression model. We examine if miR-183 exerts its effects by directly binding to and inhibiting the ITGB1 promoter activity. In addition, we investigate if miR-183 could regulate stromal cell invasiveness. The findings from these experiments will help us to better understand the miR-183-mediated molecular mechanism in endometric stromal cells.
All the eutopic and normal endometrial tissues were obtained at the Nanjing Maternity and Child Health Care Hospital Affiliated to Nanjing Medical University by uterine curettage from patients with or without endometriosis. None of the patients had received preoperative hormonal therapy, and all samples were histologically confirmed by pathologists. All samples were collected from the proliferative phase of the menstrual cycle. The phase of the menstrual cycle was determined based on histologic evaluation of the endometrium with the assistance of pathologists. The average age of the patients was
The endometrial stromal cells (ESC) from normal women without endometriosis were used as control. Tissue digestion and stromal cell isolation and culture were performed according to the method described in previous publication [
The lentivirus gene transfer vector carrying precursor of hsa-miR-183 (Genbank accession number: MIMAT0000261) and encoding green fluorescence protein (GFP) were constructed by Genechem Co., Ltd., Shanghai, China, and confirmed by DNA sequencing. The primers of RNA were 5′-GAGGATCCCCGGGTACCAAGGGAGTGGGCAGGCTA and 5′-ATAAGCTTGATATCGTCCCTGCACCCTTGGAAGCA. The recombinant lentivirus for miR-183 overexpression (miR-183-lentivirus) and the control lentivirus (GFP-lentivirus) were prepared and titered to
The sequence of inhibitor of hsa-miR-183-5p was TATGGCACTGGTAGAATTCACT. The recombinant lentivirus of miR-183-5p inhibitor (In-miR-183 lentivirus) and the control lentivirus (GFP-lentivirus) were prepared and titered to
ESC from women without endometriosis were plated in 6-well plates (5 × 104 cells/well) overnight. The lentiviruses were diluted in 0.2 mL complete medium containing polybrene (8 mg/mL) and added to the cells for 12 h of incubation at 37°C, followed by incubation in 0.3 mL of freshly prepared polybrene-DMEM for 24 h. The media were replaced with fresh DMEM and the cells were cultured for 3 days. The lentivirus transduction efficiency of ESC was determined by the detection of GFP signals under a fluorescence microscope at 72 h after transduction. The miR-183 expression in stably transduced ESC was measured by real-time PCR. The ESC transfected with miR-183-lentivirus, In-miR-183-lentivirus, and GFP-lentivirus were kept for further analysis.
For the microarray analyses, groups were divided into the ESC with miR-183 overexpression and the control ones. Total RNA was extracted using TRIzol (Invitrogen) according to the manufacturer’s instructions. Gene expression profiling was conducted using PrimeView Human Gene Expression Array (Affymetrix). The array contains 530,000 probes covering more than 36,000 transcripts and variants, which represent more than 20,000 genes mapped through RefSeq or via UniGene annotation. All subsequent technical procedures and quality controls were performed by Genechem Co., Ltd., Shanghai, China. The arrays were scanned using a GeneChip Scanner 3000 (Affymetrix, Inc., CA, USA). Raw data were extracted from the scanned images and analyzed using GeneSpring GX software version 11.5 (Agilent Technologies, CA, USA).
The data were normalized using the PLIER default protocol. Significant differentially expressed genes were analyzed using an unpaired
Differentially expressed genes were uploaded to the Ingenuity database (Ingenuity Systems, Redwood City, CA, USA) for pathway and functional analyses. Genes were further annotated and classified based on the Gene Ontology (GO) consortium annotations from the GO Bostaurus database using GOEAST (Gene Ontology Enrichment Analysis Software Toolkit).
ESC proteins were extracted with RIPA buffer [(50 mM Tris-HCl, pH 8.0, 150 mM NaCl, 1% (v/v) NP-40, 0.5% (v/o) sodium deoxycholate, and 0.1% (w/o) sodium dodecyl sulphate (SDS)] supplemented with a protease inhibitor cocktail (Sigma). After incubating on ice for 30 min, cell debris was removed by centrifugation at 12,000 g for 10 min. Cell lysates were resolved in 12% SDS-PAGE electrophoresis and transferred to the PVDF membrane (Bio-Rad, Hercules, CA). Nonspecific binding was blocked by incubating the membranes in Tris-buffered saline containing 5% nonfat milk (TBST, 50 mmol/L Tris–HCl, 150 mmol/L NaCl, and 0.1% Tween-20) for 1 h at room temperature. Membranes were incubated overnight at 4°C with AMIGO2 antibody (1 : 400, RD), integrin
The mutant construct of ITGB1 3′UTR was obtained by introducing the mutation into the 7 nucleotides (GUGCCAUU) of the seed region for miR-183. The mutant construct of AMIGO2 3′UTR was obtained by introducing two mutations into the 7 nucleotides (GUGCCAUA) (UGCCAUA) of the seed region for miR-183. The miR-183 target sequences in the coding region of ITGB1/AMIGO2 were amplified by PCR and cloned into GV143 that contained a firefly luciferase reporter gene. Wild-type ITBG1/AMIGO2 3′UTR or mutant ITBG1/AMIGO2 3′UTR and the empty 3′UTR vector were cotransfected into ESC. Cell transfection using Lipofectamine 2000 and normalization for transfection efficiency was performed according to the recommendation of manufacturer (Invitrogen). Luciferase activity was measured 24 h after transfection using the Dual-Luciferase Reporter Assay System (Promega Corp., Madison, WI).
Endometrial tissue was minced with a scalpel blade. Total RNA was isolated using TRIzol (Takara, Otsu, Shiga, Japan) and cDNA was synthesized using the SYBR Prime Script RT-PCR kit (Takara) on the ABI Prism 7500 Sequence Detection System according to manufacturer’s instructions. The housekeeping gene
To further validate direct targeting of ITGB1 by miR-183, functional rescue experiment was performed by cotransfection with miR-183 mimic and plasmid constructs expressing ITGB1 in ESC using Lipofectamine 2000 (Invitrogen) as described above. The expression plasmid pcDNA-ITGB1, encoding human ITGB1, was purchased from Genechem. The presence of complete ITGB1 coding regions was confirmed by DNA sequencing.
ESC (2.5 × 104) were seeded on a transwell insert coated with extracellular matrix (ECM) (8 mm pore size, 24-well format; Corning Costar) in 2% FBS medium. Complete medium (10% FBS) was added to the lower chamber. To determine the amount of invasion, cells were incubated for 24 h and then removed from the upper chamber using a cotton swab. The invaded cells on the underside of the insert were fixed with methanol, stained with crystal violet for 2 min, and rinsed with phosphate buffered saline (PBS). The undersides of the membrane were photographed to compare the number of invaded cells per insert. The transmigrated cells were counted using a light microscope. Invasive cells were scored by counting 10 random high-power fields per filter.
Data represents mean ± SEM from at least 3 independent experiments. Difference between experimental and control groups was determined by Student’s
In order to screen target genes in response to miR-183, we used microarrays representing more than 20,000 genes mapped through RefSeq or via UniGene annotation. We studied gene expression alterations (up- or downregulation) at 24 h after transfection. The changes of gene expression in miR-183-overexpressing endometrial stromal cells were analyzed. Differential expression was found in 27 genes at
Hierarchical clustering of differentially expressed genes in miR-183-overexpressing endometrial stromal cells versus control cells. Gene expression profiling was conducted using PrimeView Human Gene Expression Array. Raw data were extracted from the scanned images and analyzed with GeneSpring GX software version 11.5. The data was normalized using the iterative PLIER default protocol. Differentially expressed genes were analyzed with the unpaired Student
By using the Gene Ontology (GO) database, we systematically extracted and analyzed the information of three GO categories, “biological process,” “molecular function,” and “cellular component.” It was revealed that the identified genes were involved in hemophilic cell adhesion (ITGB1, AMIGO2), cell-cell adhesion (ITGB1, AMIGO2), cell migration (ITGB1, MYH9), positive regulation of catalytic activity (PSEN2, SHC1), and proteolysis (MYH9, PSEN2) (Table
List of genes with fold of change ≥1.5 (
Gene | Gene set name |
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ITGB1, AMIGO2 | Hemophilic cell adhesion |
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ITGB1, AMIGO2 | Cell to cell adhesion |
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ITGB1, MYH9 | Cell migration |
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PSEN2, SHC1 | Positive regulation of catalytic activity |
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MYH9, PSEN2 | Proteolysis |
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Significant pathway analysis revealed that the gene expression alterations in endometrial stromal cells were involved in pathways of PTEN (ITGB1, SHC1), TFF (ITGB1, SHC1), ECM (ITGB1, SHC1), ERK (ITGB1, SHC1), integrin (ITGB1, SHC1), pathogenic
List of genes with fold of change ≥1.5 (
Gene | Gene set name | Pathways |
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ITGB1, SHC1 | BIOCARTA_PTEN_PATHWAY | PTEN dependent cell cycle arrest and apoptosis |
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ITGB1, SHC1 | BIOCARTA_TFF_PATHWAY | Trefoil factors initiate mucosal healing |
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ITGB1, SHC1 | BIOCARTA_ECM_PATHWAY | Erk and PI-3 kinase are necessary for collagen binding in corneal epithelia |
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ITGB1, SHC1 | BIOCARTA_ERK_PATHWAY | Erk1/Erk2 Mapk signaling pathway |
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ITGB1, SHC1 | BIOCARTA_INTEGRIN_PATHWAY | Integrin signaling pathway |
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ITGB1, TUBB | KEGG_PATHOGENIC_ESCHERICHIA_COLI_INFECFECTION | Pathogenic |
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SHC1, VAV3, GNB2 | KEGG_CHEMOKINE_SIGNALING_PATHWAY | Chemokine signaling pathway |
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ITGB1, SHC1, VAV3 | KEGG_FOCAL_ADHESION | Focal adhesion |
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ITGB1, VAV3, MYH9 | KEGG_REGULATION_OF_ACTIN_CYTOSKELETON | Regulation of actin cytoskeleton |
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ITGB1, VAV3 | KEGG_LEUKOCYTE_TRANSENDOTHELIAL_MIGRATRATION | Leukocyte transendothelial migration |
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Because of the inhibitory property of miRNA on target genes, we chose from the list of 8 downregulated genes (ITGB1, AMIGO2, VAV3, PSEN2, LHFPL2, HS2ST1, AHSA2, and UQCRB) in miR-183-overexpressing cells. Biological function analysis using GO databases revealed that ITGB1 and AMIGO2 were involved in cell adhesion and/or cell migration. These two genes were selected for further study. PubMed reports showed VAV3 and PSEN2 were both involved in cell invasion [
Western blotting (Figure
Confirmation of microarray data with Western blotting analyses. The endometrial stromal cells transfected with miR-183-lentivirus (low dose or high dose), In-miR-183-lentivirus (low dose or high dose), and GFP-lentivirus (NC, normal control) were used to examine the expression alterations of integrin
To investigate if ITBG1 and AMIGO2 are the direct targets of miR-183, we performed luciferase assay to determine whether miR-183 binds to the 3′UTR of ITBG1/AMIGO2 mRNA (Figure
ITGB1, but not AMIGO2, is the direct target of miR-183. (a) The binding site of miR-183 in the 3′UTR of ITGB1 (top) and AMIGO2 (bottom) 3′UTR, along with the mutant construct in the predicted binding region. (b) MiR-183, but not AMIGO2, directly targets ITBG1. Endometrial stromal cells were cotransfected with wild-type reporter containing the ITBG1/AMIGO2 3′UTR or mutant ITBG1/AMIGO2 3′UTR plus miR-183 or negative control using Invitrogen Lipofectamine 2000 reagents. Luminescence was measured after 24 hours of transfection. Reporter plasmid expressing ITGB1 mRNA that contains sequences potentially targeted by miR-183 displayed a significantly decreased luciferase activity in cells transfected with miR-183 (
Real-time RT-PCR results indicated that ITGB was significantly increased in the eutopic endometrial tissues from patients with endometriosis (
Validation of ITGB1 expression in eutopic endometrium with endometriosis (
To ascertain that miR-183 regulates the function of endometrial stromal cells through its interaction with ITGB1, a rescue experiment was performed. Overexpression of ITGB1 partially rescued the repressive effects of miR-183, leading to elevated invasion abilities in the cells (Figure
Overexpression of ITGB1 rescued the repressive effects of miR-183 on endometrial stromal cells, leading to elevated invasive abilities in transwell assays. Endometrial stromal cells were infected with miR-183-lentivirus, miR-183/ITGB1-lentivirus, and GFP-lentivirus in upper wells. After 24 hours, the number of cells that invaded through Matrigel was counted in at least 10 fields per well. (a) Representative photographs show that miR-183 inhibited the invasiveness of endometrial stromal cells, whereas ITGB1 partially rescued the repressive effects of miR-183. (b) Cell counting results indicate that ITGB1 overexpression rescued the repressive effects of miR-183.
In the previous study, we performed miRNA microarray screening and identified several differentially expressed miRNAs in the normal, eutopic, and ectopic endometrium. Among these miRNA species, miR-183 was found to be downregulated in the ectopic and eutopic tissues. Functional analysis indicated that miR-183 promoted endometrial stromal cell apoptosis and had a negative regulatory impact on the invasive ability of cells, although it had no effect on cell proliferation [
MiR-183 is a member of a miRNA family (miR-183, miR-182, and miR-96) that clusters within a 2–4 kb region at chromosome 7q32. These miRNAs are known to regulate cell differentiation, apoptosis, motility, adhesion, and invasion [
To systematically investigate the potential mechanism by which miR-183 may contribute to the development of endometriosis, we performed microarray analysis to identify the target genes with relevance to cell functions in miR-183-overexpressing endometrial stromal cells. Eight genes were found to be downregulated in endometrial stromal cells with miR-183 overexpression. Among them, the GO databases, pathway analyses, and PubMed reports pointed to important association of 4 genes (ITGB1, AMIGO2, VAV3, and PSEN2) with cell adhesion, cell migration, and cell invasiveness. Western blotting results showed that endometrial stromal cell secreted integrin
According to Sampson’s theory, endometriosis is thought to be initiated via retrograde endometrium into peritoneal cavity during menstruation. However, while this phenomenon occurs in approximately 75–90% of women, far fewer suffer the disease, suggesting that additional factors must contribute to the process. Invasion to ectopic locations is the key step for the initiation of endometriosis, during which adhesion molecules play an important role. The integrin family includes glycoproteins that form dimeric structure and mediate cell attachment to the ECM components [
AMIGO2 (ALI1, DEGA) was first reported to be preferentially expressed in the central nervous system. Sequence analyses revealed that the protein contains seven leucine-rich repeats, one IgC2-like loop, and a transmembrane domain and displays homology to Kek and Trk families [
To investigate whether miR-183 directly targets ITGB1 and AMIGO2, dual luciferase reporter assays were carried out. We found that miR-183 negatively regulated the expression of ITBG1 by directly targeting its 3′UTR but might not directly regulate the expression of AMIGO2. We further detected differential expression of ITGB1 in endometrium with or without endometriosis by quantitative RT-PCR. The higher expression of integrin
In conclusion, altered miR-183 expression may cause deregulation of its target gene ITBG1, affecting the cell adhesiveness and invasiveness of endometrial stromal cells, which in turn lead to pathogenesis of endometriosis. These findings revealed a novel pathologic role of miR-183 for endometriosis. It would be of great interest to investigate if these alterations may serve as biomarkers for the prediction and/or treatment of endometriosis. The regulation of miR-183 and the exact mechanism by which miR-183 regulates ITBG1 expression remain to be characterized.
The authors declare that they have no conflict of interests.
This study was supported by grants from the National Natural Science Foundation of China (nos. 81100405 and 81471438), the Key Program of Nanjing Medical Science and Technology Development Foundation, Nanjing Department of Health (no. QRX11109).