Abstract
Purpose:
microRNAs (miRNAs) are small non-coding RNAs, which negatively regulate gene expression. miRNAs are found within cells and in exosomes circulating in body fluids such as tears. We hypothesized that miRNAs in tears may regulate corneal epithelial cell function. The purposes of present experiment were to 1) determine which miRNAs are highly expressed in monkey tears, and 2) examine the involvement of miRNAs in corneal function.
Methods:
Exosomes were isolated from monkey tears and sera, and confirmed by immunoblotting for the exosome biomarker CD63. Extracted exosome miRNAs were subjected to microarray analysis (3D-GeneTM Human miRNA Oligo chip). Selected miRNAs were quantified by qPCR. To examine the function of miRNAs, mimics and inhibitors of miRNAs were transfected into human corneal epithelial cells (HCE-T) that were counted 48 hrs after transfection. Human trabecular meshwork cells served as controls.
Results:
Microarray analysis showed that 108 miRNAs were expressed more than 3 fold higher in tears than sera. Of 9 miRNAs selected, qPCR analysis confirmed that miR-3610, miR-184, miR-1908, and miR-203 showed preferred expression in tears. miR-3610, miR-184 and miR-1908 had no effect on HCT-T cell proliferation. Importantly, transfection of a miR-203 mimic significantly reduced HCE-T cell proliferation, while the miR-203 inhibitor significantly increased proliferation. In the control human trabecular meshwork cells, miR-203 inhibitor did not increase proliferation.
Conclusions:
miR-203 is present in HCE-T cells and tears and may be a specific negative regulator of cell proliferation. The positive proliferative effect of miR-203 inhibitor on HCE-T cells, but not on the cells of the trabecular meshwork, suggested that miR-203 inhibitors might be useful in the treatment of corneal epithelial defects.