MicroRNA-215 Regulates Fibroblast Function: Insights from a Human Fibrotic Disease

MicroRNAs are implicated in the regulation of gene expression via various mechanisms in health and disease, including fibrotic processes. Pterygium is an ocular surface condition characterized by abnormal fibroblast proliferation and matrix deposition. We aimed to investigate the role of microRNAs in pterygium and understand the relevant cellular and molecular mechanisms. To achieve this objective, a combination of approaches using surgically excised paired human pterygium and conjunctival tissues as well as cultured primary fibroblast cells from tissue explants were evaluated. Fibroblast dysfunction has been shown to play a central role in pterygium pathology. Here we show that miR-215, among a few others, was down-regulated (2-fold) in pterygium compared to control, and this was consistent in microarray, real-time PCR and fluorescent in-situ hybridization. The effects of increased miR-215 were investigated by adding exogenous miR-215 to fibroblasts, and this showed a decrease in cell proliferation but no significant apoptosis compared to control. Further cell cycle analysis showed that miR-215 depressed progression of cells at G1/S as well as G2/M. A few cell cycle related transcripts were downregulated (2.2-4.5-fold) on addition of miR-215: Mcm3, Dicer1, Cdc25A, Ick, Trip13 and Mcm10. Theoretic binding energies were used to predict miR-215 binding targets and luciferase reporter studies confirmed Mcm10 and Cdc25A as direct targets. In summary, mir-215 could play a role in inhibiting fibroblast proliferation in ocular surface conjunctiva. Dampening of this mir-215 could result in increased fibroblast cell cycling and proliferation, with possibly increased fibroblastic production of matrix, inducing pterygium formation.