Autocrine small extracellular vesicles induce tubular phenotypic transformation in diabetic nephropathy via miR-21-5p

•High glucose-derived small extracellular vesicles influence diabetic nephropathy through miR-21-5p in cell experiments.•BTG2 is the target gene of miR-21-5p.•High glucose-induced small extracellular vesicles can promote epithelial-mesenchymal transition in diabetic nephropathy, providing a new perspective for combating the disease. Diabetic nephropathy (DN) is one of the most common and serious microvascular complications associated with diabetes. DN is the leading contributor to the majority of cases of end-stage renal disease (ESRD). Small extracellular vesicles (sEVs) can transport various genetic materials to recipient cells. The objective of this study was to explore how sEVs released from HK-2 cells when stimulated by high glucose levels influence renal tubular phenotypic transformation through miR-21-5p. Both human and cell studies were utilized to explore the crosstalk between proximal renal tubules in DN. sEVs from plasma and cells were isolated using ultracentrifugation, and the differential expression of miR-21-5p in plasma sEVs from DN patients versus healthy controls was quantified using Quantitative Real-time PCR (RT-qPCR). A DN model was constructed by stimulating HK-2 cells with glucose. The expression of epithelial-mesenchymal transition (EMT) proteins in each cell group was analyzed by Western Blot (WB), while miR-21-5p levels in both cells and their sEVs were quantified using RT-qPCR. A stable transfected HK-2 cell line was constructed. The CCK8 assay, scratch assay, and WB were employed to detect EMT proteins, aiming to explore how autocrine sEVs affect tubular phenotypic transformation in diabetic nephropathy (DN). The expression of miR-21-5p in plasma sEVs was significantly elevated in the DN group compared to the healthy control group. High glucose (HG) stimulation of HK-2 cells resulted in higher miR-21-5p expression in both cells and their sEVs, leading to enhanced proliferation, migration, and EMT capacities in these cells. Co-incubation of HK-2 cells with HG-sEVs significantly enhanced the proliferation, migration, and EMT capabilities of the recipient cells, but miR-21-5p knockdown reversed these effects. These results indicate that high glucose stimulates HK-2 cells to secrete sEVs, which promote DN proliferation, migration, and EMT through miR-21-5p, thereby offering new insights into the treatment of DN.