Microvesicles containing microRNA-216a secreted by tubular epithelial cells participate in renal interstitial fibrosis through activating PTEN/AKT pathway.

OBJECTIVE: The aim of this study was to elucidate the role of microRNA-216a in microvesicles (MVs) during the process of renal interstitial fibrosis and to investigate its underlying mechanism. MATERIALS AND METHODS: Unilateral ureteral occlusion (UUO) model was first established in mice, and kidney tissues and urine in the obscured kidney were collected. NRK-52E cells were induced with 5 ng/mL transforming growth factor-β1 (TGF-β1) for constructing the renal interstitial fibrosis model in vitro. Subsequently, the expression levels of E-cadherin, α-smooth muscle actin (α-SMA) and fibronectin (FN) in NRK-52E cells induced with or without TGF-β1 were determined, respectively. The culture medium was collected from NRK-52E cells of the control group (without TGF-β1 induction) and the TGF-β1 group (TGF-β1 induction), and MVs were observed. Afterward, NRK-52E cells were treated with MVs isolated from the control group or the TGF-β1 group, followed by detecting the expressions of E-cadherin, α-SMA and FN. Meanwhile, the expression levels of CD63, microRNA-216a, PTEN and p-AKT were determined as well. The microRNA-216 level in kidney tissues and urine of UUO mice were determined. Furthermore, the expressions of PTEN and p-AKT in mouse kidney tissues were accessed by Western blot and quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). RESULTS: TGF-β1 induction in NRK-52E cells gradually downregulated E-cadherin, whereas upregulated α-SMA and FN with the prolongation of induction time. MVs isolated from the culture medium of the TGF-β1 group downregulated E-cadherin, and upregulated FN and α-SMA. The expression levels of CD63 and microRNA-216a were markedly higher in the TGF-β1 group compared with the control group. Downregulated PTEN and upregulated p-AKT were observed in TGF-β1-induced cells at both mRNA and protein levels. Besides, microRNA-216a expression in mouse kidney tissues and urine from obscured kidney was remarkably increased with the prolongation of UUO. Consistent with those in NRK-52E cells, the protein level of PTEN was significantly decreased, whereas p-AKT was markedly increased with the prolongation of UUO. CONCLUSIONS: MVs containing microRNA-216a secreted by injured proximal tubular epithelial cells participate in renal interstitial fibrosis by activating the PTEN/AKT pathway.