Pterygium samples and control conjunctiva tissue samples: A total of 263 conjunctiva tissues were analysed in this study, including 234 pterygium samples and 29 control conjunctiva tissues. All pterygium samples were obtained from patients who diagnosed with primary pterygium undergoing a surgical resection and control conjunctiva tissues were collected from patients who underwent cataract surgery from December 2014 to October 2019 at Zhongnan Hospital of Wuhan University. Samples were stored at -80°C immediately after surgery until used.
This study was approved by the Medical Ethical Committee of Zhongnan Hospital of Wuhan University and followed the tenets of the Declaration of Helsinki and its later amendments. Informed consents were obtained from all patients before the study was carried out.
MiRNA microarray assay: Total RNA was isolated from frozen tissue using miRNeasy Mini Kit (Qiagen, Hilden, Germany) according to the manufacturer’s instruction before evaluated by the NanoDrop2000 spectrophotometer (Thermo Scientific, MA, USA). Total RNA was purified and labelled using FlashTagTM Biotin HSR RNA Labelling Kit (P/N 901911, Affymetrix) according to the manufacturer’s instructions to obtain biotin labelled miRNA. Array hybridization and wash were performed by GeneChip® Hybridization, Wash and Stain Kit (P/N900720, Affymetrix Santa Clara CA, USA) and GeneChip Eukaryotic Hybridization Control Kit (P/N 900454, Affymetrix Santa Clara CA, USA) in Hybridization Oven 645 (P/N 00-0331 (220V), Affymetrix Santa Clara CA, USA) and Fluidics Station 450 (P/N 00-0079, Affymetrix Santa Clara CA, USA) according to the manufacturer’s instructions. Arrays were scanned by GeneChip® Scanner 7G (Affymetrix, Santa Clara, CA, USA) using Command Console Software 3.2 (Affymetrix, Santa Clara, CA, USA) with default settings. Raw data was normalized by RMA and DABG algorithm, Expression Console (Affymetrix, Santa Clara, CA, USA).
Rtranscription and quantitative real-time PCR: MiRNA and cDNA were synthesized from 500ng total RNA by RevetAid RT Reverse Transcription Kit (Thermo Scientific, MA, USA) with specific miRNAs stem-loop RT primers (Table 1) and oligo d(T)18 , using reverse transcription and quantitative real-time polymerase chain reaction (qRT-PCR). The miRNAs or mRNA expression levels were detected using Bio-Rad CFX96TM real-time PCR detection system (Bio-Rad, CA, USA) and each sample was detected in duplicate. Each assay consisted of 1 × SYBR Green quantitative real-time PCR master mix (Bio-Rad, CA, USA), 0.5 μM of forward and reverse primers (Table 1), and 1 μl cDNA template in a total volume of 20 μl. Non-template control was used as negative control, miRNAs reactions were normalized to U6, mRNA was normalized to GAPDH and the relative expression levels were calculated using the 2-△Cq method.
Cell culture: The human conjunctiva epithelial cell line (HConEpic, HCE) was purchased from BeNa Culture Collection (Beijing, China), which was primary culture cells (Supplementary 1). HCEs were supplemented with High glucose Dulbecco’s modified Eagle’s medium (H-DMEM, HyClone) containing 10% fetal bovine serum (Gibco) and 1uM penicillin-streptomycin (Gibco). Cells were grown at a humidified atmosphere of 5% CO2 at 37°C. After 24h incubation in growth medium, TGF-b and EGF were added to obstain the optimal concentrations (10nM & 20nM). The medium was changed every other day and TGF-b and EGF were reintroduced to maintain the concentrations, and the cells that harvested after 7 days were used for subsequent experiments.
Immunofluorescence staining: For EMT markers detection, HCEs were fixed with 3.5% paraformaldehyde, permeabilized with 0.1% Triton X-100, blocked with 2% bovine serum albumin (BSA, sigma, USA), and incubated over night at 4°C with primary antibodies as following: anti-N-cadherin (1:100, Abclonal, China), anti-E-cadherin (1:100) and anti-vimentin (1:100). After washing with phosphate buffered saline (PBS, Gibco), the cells were incubated for 1 hour with fluorescein isothiocyanate (FITC)-conjugated mouse immunoglobulin G secondary antibody (1:200). The stained cells were counterstained with 4’, 6-diamidino-2-phenylindole (DAPI, Invitrogen, USA) and viewed under a consistent fluorescence in situ hybridization (FISH) imager (BX51, Olympus, Tokyo, Japan).
Plasmids construction and transient transfection: MiR-199a-3p and miR-199a-5p mimics and inhibitors were purchased from RiboBio Co. Ltd (Ribo, China) and short hairpin RNAs (shRNAs) knocking down DUSP5 and MAP3K11 were purchased from Shanghai Genechem Co. Ltd (Genechem, China) (Table 2). To overexpress DUSP5 and MAP3K11, a full-length coding sequence (CDS) was amplified, and the EcoRI-HF and XhoI sites (NEB, USA) were used to insert the CDS product into pCMV-myc vector (Invitrogen, NY, USA). Before transfection, 2*105 cells were seeded into each well of 6-well plates. After 24h incubation in growth medium without penicillin-streptomycin, the cells were transiently transfected with miRNA mimics and inhibitors using riboFECTTM CP (Ribo, China), or with plasmids using Lipofectamine 2000 (Invitrogen, Carlsbad, CA, USA). The cells were incubated for an additional 24-48h for the following experiments.
Wound healing and transwell assay: HCEs dealt with TGF-b and EGF for 7d, were seeded equivalently into 6-well culture plates and then treated with transient transfection for 24h before scratching or resuspending. A wound was scratched onto the monolayer with a sterile 20ul tip (Axygen, Union City, CA, USA). Images of HCEs migrating into the wound were captured at time points of 0, 24 and 48h by an inverted microscope.
The migration assay was performed using upper chambers of Transwell insert (0.8um pore size, Corning Incorporated, Costar, USA) with 4*105cells in serum-free medium for 48h. After migration, cells passed through the coated membrane to the lower surface, where cell were fixed with 4% paraformaldehyde and stained with 0.1% crystal violet. The cell was counted under a microscope.
Cell apoptosis determined by flow cytometry: The flow cytometry was performed to analyse the apoptosis of HCEs. Cells were re-suspended with Annexin V-FITC and propidiumiodide (PI) successively according to the manufacture’s protocol (BestBio, China) at the concentration of 106 cells/ml. Cell apoptosis was analysed by flow cytometry (FACSCanto II; BD Bioscience, Franklin Lake, NJ).
Western blot analysis: After cells were seeded in 6-well plates for 48-72h, cells were washed with PBS and harvested in RIPA with phosphorylase inhibitor and phenylmethanesulfonyl fluoride (PMSF). Equal amounts of the supernatant were loaded per lane and resolved by SDS-polyacrylamide electrophoresis. Then, proteins were transferred onto polyvinylidene fluoride (PVDF) membrane (Millipore, USA) and blocked by 5% BSA. Primary antibodies should be probed overnight at 4°C, including rabbit anti-MAP3K11, anti-DUSP5, anti-Vimentin, anti-E-Cadherin, anti-N-Cadherin antibodies and mouse anti-GAPDH (abClone) antibody. Membranes were washed in Tris buffered saline tween (TBS-T) and incubated with horseradish peroxidase-conjugated anti-rabbit or anti-mouse secondary antibodies. Membranes were washed in TBS-T and then exposed using the electrochemical luminescence (ECL) system. Protein loading was normalized by GAPDH.
Dual-luciferase reporter assay: The DUSP5 or MAP3K11 fragments of 3’UTR whole region containing the wild-type binding sites of miR-199a -3p or miR-199a-5p, were cloned into pmirGLO vector (Promega, Madison, WI, USA) to generated DUSP5-WT and MAP3K11-WT vectors. Then the DUSP5-MUT, MAP3K11-MUT1, MAP3K11-MUT2 and MAP3K11-MUT1+2 vectors containing mutant loci were constructed, since there are 2 binding sites between miR-199a-5p and MAP3K11. For luciferase reporter assay, 293T and HCE were plated in 12-well plates and transfected with miR-199a-3p or miR-199a-5p mimics and mimic-NC (50nM) or miR-199a-3p or miR-199a-5p inhibitor and inhibitor-NC (100nM), and 1ug of blank plasmids. After about 36h of transfection, luciferase activity was detected by the Dual Luciferase Reporter Assay Kit (Promega, WI, USA) and the Promega GloMax 20/20 luminometer (Promega, WI, USA). All experiments were performed in triplicates and the relative luciferase activity ratios of firefly luciferase activity normalized to Renilla luciferase were calculated.
MiRNAs target gene prediction and GO/pathway analysis: Differentially expressed miRNAs were subjected to target gene prediction analysis using TargetScan, miRDB, mirTarBase, miRanda, Targetminer and miRNAorg. The predicted results of target genes were shown by Venn diagram. GO network maps and term enrichment analysis were performed by using plug-in of Cytoscape: ClueGO and CluePedia, with terms defined by GO_BiologicalProcess-GOA_07.12.2015 and KEGG pathway. Significance was defined by p value < 0.05 and Kappa score threshold of 0.4 for pathways reporting.
Statistical analysis: All data were analysed by GraphPad-Prism8.0 (Graph Pad, CA, USA) in independent t-test, Mann–Whitney U test or Pearson Correlation. p < 0.05 (two-tailed) was considered statistically significant.