Protective effect of miRNA-containing extracellular vesicles derived from mesenchymal stromal cells of old rats on renal function in chronic kidney disease

INTRODUCTION: Mesenchymal stromal cells (MSCs) play an important role in the prevention of cell and tissue fibrosis. Senescence may decrease the function of MSCs during recovery from tissue and organ damage. Extracellular vesicles (EVs) released from MSCs contribute to the repair of kidney injury. We explored the influence of senescence on EVs derived from MSCs (MSC-EVs) and detected the protective effects of MSC-EVs expressing low levels of miR-294/miR-133 derived from old rats against chronic kidney disease (CKD). METHODS: The effects of MSC-EVs derived from 3-month-old and 18-month-old male Fisher 344 rats on renal fibrosis were explored in a unilateral ureteral obstruction (UUO) model. pLV-miR-294/pLV-miR-133 mimic/inhibitor were injected into young and old rats before UUO to detect the effects of miR-294/miR-133, which were decreased in MSC-EVs and sera from old rats, on renal function in CKD. Transforming growth factor-β1 (TGF-β1)-induced human renal proximal tubular epithelial (HK2) cells were used to imitate the pathological process of renal fibrosis in vitro. Western blotting was used to assess the expression of epithelial/mesenchymal markers and phosphorylation of proteins in HK2 cells. RESULTS: The inhibition of UUO-induced CKD by MSC-EVs was weaker in old rats than in young rats. Downregulation of miRNAs (miR-294 and miR-133) in both MSC-EVs and sera from old rats obviously attenuated UUO-induced renal injury in old rats. miR-294 and miR-133 overexpression mitigated TGF-β1-mediated epithelial-mesenchymal transition (EMT) in HK2 cells, and the obvious increase in the phosphorylation of both SMAD2/3 and ERK1/2 induced by TGF-β1 was prevented in miR-294- and miR-133-overexpressing HK2 cells. CONCLUSIONS: The ability of MSC-EVs to inhibit renal fibrosis decreased with age. miR-294/miR-133 in MSC-EVs and sera had an important effect on renal fibrosis in old rats and on EMT in HK2 cells. Furthermore, miR-294/miR-133 overexpression prevented SMAD2/3 and ERK1/2 phosphorylation in HK2 cells during TGF-β1-mediated EMT. These findings show that miR-294/miR-133 may be therapeutic in renal fibrosis and related renal dysfunction in elderly individuals.