Abstract
Tubular epithelial cell apoptosis contributes to tubulointerstitial fibrosis but its regulation remains unclear. Here, in fibrotic kidney induced by unilateral ureteral obstruction (UUO), we demonstrate that miR-34a is markedly upregulated in tubulointerstitial spaces and microvesicles isolated from obstructed kidney. However, miR-34a is not de novo synthesized by proximal tubular epithelial cells but by fibroblasts after incubation with TGF-β1. miR-34a is markedly upregulated in microvesicles isolated from the cell culture medium of TGF-β1-treated fibroblasts. These microvesicles act as a vector for delivery of upregulated miR-34a from fibroblasts to tubular cells. The fibroblast-derived miR-34a-containing microvesicles induce the apoptosis of tubular cells. The exogenous miR-34a regulates tubular apoptosis by modulating the expression of the anti-apoptotic protein Bcl-2. Moreover, injection of exogenous miR-34a-containing microvesicles enhances tubular cell apoptosis in mice. This study suggests that secreted fibroblast miR-34a transported by microvesicles induces tubular cell apoptosis in obstructed kidney. This study reveals a new mechanism whereby microvesicle-mediated communication of miRNA between fibroblasts and tubular cells is involved in regulating tubular cell apoptosis, which might provide new therapeutic targets for renal tubulointerstitial fibrosis.