Analysis of miR‐21‐5p and ‐3p expression and function during pathological neovascularization

Abstract

Retinal neovascularization (RNV) is a sight compromising complication of diabetes and prematurity. Previous studies from our laboratory have shown that the small noncoding microRNA, microRNA‐21‐5p (miR‐21‐5p), is an inducer of RNV. Emerging new evidence has shown that miRNA passenger strands, the 3p forms, which were thought to be degraded, possess biological functions. In this study, we have investigated the role of miR‐21‐3p in RNV. In particular, we have assessed the effect of miR‐21‐3p on the same molecular targets of miR‐21‐5p: the tissue inhibitor of matrix metalloproteinases 3 (TIMP3), peroxisome proliferator‐activated receptor alpha (PPAR‐α) and pigment epithelium‐derived factor (PEDF). Real‐time PCR (RT‐PCR) showed that the expression of miR‐21‐3p is significantly upregulated in retinas and blood spot samples of mice subjected to oxygen‐induced retinopathy (OIR), a model of RNV. Furthermore, we noted a significant upregulation of miR‐21‐3p levels, measured by RT‐PCR, in human retinal endothelial cells (HuREC) and pigment epithelial cells (ARPE‐19) when exposed to angiogenic stimuli such as 20ng/mL of vascular endothelial growth factor (VEGF) or to hypoxic conditions (pO2= 2+/−0.5) for different times (1, 3, 6, and 12 hours). Transfection of HuREC and ARPE‐19 with miR‐21‐3p mimic (50nM) for 24 and 48 hours had only marginal inhibition on the miR‐21‐5p target genes (TIMP3, PPARα, and PEDF). Additionally, blockade of miR‐21‐3p achieved by transfecting cells with a specific miR‐21‐3p inhibitor (50nM) did not rescue VEGF‐changes in TIMP3, PPARα, and PEDF expression. Our data demonstrated that the passenger strand, miR‐21‐3p, is co‐expressed with miR‐21‐5p in ischemic conditions, but targets different genes. Although further studies will be necessary to clarify miR‐21‐3p biological function, our studies suggest that, together with miR‐21‐5p, miR‐21‐3p may hold potential diagnostic and therapeutic value for treatment of RNV in ischemic retinopathies.Support or Funding InformationAll support for this research came from the Bartoli laboratory of the Ophthalmology Department of the Medical College of Georgia at Augusta University and the funding sources (EY0246, Knights Templar –GA Chapter).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.