MicroRNA-196a/b mitigate renal fibrosis by targeting TGF-β receptor 2

Abstract

Organ-specificmicroRNAs have essential roles in maintaining normal organ function. However, the micro-RNA profile of the kidney and the role of microRNAs in modulating renal function remain undefined. We performed an unbiased assessment of the genome-wide microRNA expression profile in 14 mouse organs using Solexa deep sequencing and found that microRNA-196a (miR-196a) and miR-196b are selectively expressed in kidney, with 74.37% of mouse total miR-196a and 73.19% of mouse total miR-196b distributed in the kidneys.We confirmed the predominant expression ofmiR-196a/b inmouse and human kidney, particularly in the glomeruli and tubular epithelium, by quantitative RT-PCR and in situ hybridization assays. During unilateral ureteral obstruction (UUO)-inducedmouse renal fibrosis, renalmiR-196a/b levels rapidly decreased. Elevation of renal miR-196a/b expression by hydrodynamic-based delivery of a miR-196a/b-expressing plasmid before or shortly after UUO significantly downregulated profibrotic proteins, including collagen 1 and a-smooth muscle actin, and mitigated UUO-induced renal fibrosis. In contrast, depletion of renal miR-196a/b by miR-196a/b antagomirs substantially aggravated UUO-induced renal fibrosis. Mechanistic studies further identified transforming growth factor beta receptor II (TGFbR2) as a common target of miR-196a and miR-196b. Decreasing miR-196a/b expression in human HK2 cells strongly activated TGF-b-Smad signaling and cell fibrosis; whereas increasingmiR-196a/b levels inmouse primary cultured tubular epithelial cells inhibited TGF-b-Smad signaling. In the UUO model, miR-196a/b silenced TGF-b-Smad signaling, decreased the expression of collagen 1 and a-smooth muscle actin, and attenuated renal fibrosis. Our findings suggest that elevating renal miR-196a/b levels may be a novel therapeutic strategy for treating renal fibrosis.