Signature microRNAs in human cornea limbal epithelium

This study was aimed to identify the signature microRNAs, which regulate the biological processes of corneal epithelial progenitor cell (CEPC) homeostasis and regulation through characterizing the differential expression profile of microRNAs in human limbal epithelium containing adult CEPC versus central corneal epithelium without CEPC. MicroRNA microarray had identified 37 microRNAs enriched in human corneal epithelium. Among them, nine were significantly upregulated in limbal epithelium and one in central corneal epithelium after validation by TaqMan® real-time polymerase chain reaction. In addition to our previous finding of miR-143 and 145, the expression of miR-10b, 126, and 155 was localized in limbal epithelium (LE) (predominantly basal layers) by using locked nucleic acid-based in situ hybridization. Potential target genes were predicted by TargetScan Human v6.0 and compared to the reported human cornea epithelial gene profile GSE5543. Analyzed by web-based Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and DAVID Functional Annotation Bioinformatics Resources v6.7, the downregulated genes were involved in pathways of immune response and cellular protection, apoptosis, and cell movement whereas upregulated genes with cell survival, cell-matrix interaction, and cell-cell adhesion. We found a constant occurrence of miR-143, 145, and 155 in all KEGG pathways regulating limbal epithelial events. By Ingenuity Systems (IPA®) analysis, these microRNAs could cooperatively regulate cell growth and apoptosis via tumor necrosis factor activation and MYC repression. Our findings thus suggest a unique microRNA signature existing in human limbal epithelium and participating in CEPC homeostasis.