miR−122−5p Regulates Renal Fibrosis In Vivo

The role of exogenous microRNAs (miRNAs) in renal fibrosis is poorly understood. Here, the effect of exogenous miRNAs on renal fibrosis was investigated using a renal fibrosis mouse model generated by unilateral ureteral obstruction (UUO). miRNA microarray analysis and quantitative reverse-transcription polymerase chain reaction showed that miR−122−5p was the most downregulated (0.28-fold) miRNA in the kidneys of UUO mice. The injection of an miR−122−5p mimic promoted renal fibrosis and upregulated COL1A2 and FN1, whereas an miR−122−5p inhibitor suppressed renal fibrosis and downregulated COL1A2 and FN1. The expression levels of fibrosis-related mRNAs, which were predicted targets of miR−122−5p, were evaluated. The expression level of TGFBR2, a pro-fibrotic mRNA, was upregulated by the miR−122−5p mimic, and the expression level of FOXO3, an anti−fibrotic mRNA, was upregulated by the miR−122−5p inhibitor. The protein expressions of TGFBR2 and FOXO3 were confirmed by immunohistochemistry. Additionally, the expression levels of LC3, downstream anti-fibrotic mRNAs of FOXO3, were upregulated by the miR−122−5p inhibitor. These results suggest that miR−122−5p has critical roles in renal fibrosis.