MicroRNA-494 inhibits nerve growth factor-induced cell proliferation by targeting cyclin D1 in human corneal epithelial cells

Abstract

Nerve growth factor (NGF) is expressed in the human corneal epithelium and stroma. It is an efficient therapy for human corneal ulcers caused by neurotropic disease. However, little is known about the molecular mechanism of NGF in healing human corneal epithelial diseases. Numerous microRNAs (miRNAs) are expressed in the cornea and miRNAs have important roles in regulating corneal development. In the present study, novel miRNA regulators were demonstrated to be involved in NGF-induced human corneal epithelial cell (hCEC) proliferation. NGF treatment significantly downregulated the expression of miRNA-494 in hCECs in vitro. Furthermore, miRNA-494 increased G1 arrest in the immortalized human corneal epithelial cell (ihCEC) line and suppressed cell proliferation. Accordingly, bioinformatics programs and luciferase reporter assay demonstrated that miRNA-494 directly targeted cyclin D1 by binding to a sequence in the 3'-untranslated region. In addition, overexpression of miRNA-494 decreased both basal and NGF-induced cyclin D1 expression. NGF treatment partially suppressed miRNA-494 expression and restored cyclin D1 expression. Furthermore, co-transfection of miRNA-494 with the cyclin D1 ORF clone partially restored cyclin D1 mRNA and protein expression. These findings indicate that miRNA-494 and its target cyclin D1 may be a crucial axis for NGF in regulating the proliferation of hCEC. Specific modulation of miRNA-494 in hCEC could represent an attractive approach for treating cornea epithelial diseases.