LAUSR

The application of microRNAs (miRNAs) in the therapy of kidney diseases is hampered by difficulties in delivering miRNAs effectively. Nano-sized microvesicles (MVs) are known as natural carriers of small RNAs. Our prior work has demonstrated that MVs isolated from mesenchymal stem cells (MSCs) attenuated kidney injuries induced by unilateral ureteral obstruction and 5/6 subtotal nephrectomy in mice. The present work aimed at evaluating the effects of miR-34a-5p (miR-34a)-modified MSC-MVs on transforming growth factor (TGF)-β1 induced fibrosis and apoptosis in vitro. Bone marrow MSCs were further modified by lentiviruses overexpressing miR-34a, and MVs were collected from these MSCs to treat HK-2 renal tubular cells exposed to TGF-β1. Alterations in epithelial-mesenchymal transition (EMT) and cell survival were further determined. We first demonstrated that MVs generated by miR-34a-modified MSCs contained more miR-34a. By analyzing the expression levels of epithelial markers (E-cadherin and Tight Junction Protein 1 (TJP1)) and mesenchymal markers (α-SMA and fibronectin), we found that the pro-fibrotic TGF-β1 induced EMT was remarkably suppressed by miR-34a-enriched MSC-MVs. Notch-1 receptor and Jagged-1 ligand, two major molecules of Notch signaling pathway, are predicted targets of miR-34a. We further found that the elevation in Notch-1 and Jagged-1 induced by TGF-β1 was inhibited by miR-34a-enriched MSC-MVs. The inhibitory effects of miR-34a-enriched MSC-MVs on EMT and Notch signaling pathway were stronger than the control MSC-MVs. In addition, TGF-β1 exposure also induced apoptosis in HK-2 cells. Although miR-34amofidied MSC-MVs could inhibit TGF-β1-triggered apoptosis in HK-2 cells, the effects were less significant than the control MSC-MVs. This phenomenon may be resulted from the pro-apoptotic effects of miR-34a. Our study demonstrates that miR-34a-overexpressing MSC-MVs inhibit EMT induced by pro-fibrotic TGF-β1 in renal tubular epithelial cells, possibly through inhibiting Jagged-1/Notch-1 pathway. Genetic modification of MSC-MVs with anti-fibrotic molecule may present a novel strategy for treatment of renal injuries.