Introduction: The prevalence of renal fibrosis is higher in older than in younger individuals. Through paracrine activity, bone marrow mesenchymal stem cell-derived microvesicles (BM-MSC-MVs) influence the process of renal fibrosis. Differences in microRNA (miRNA) expression of BM-MSC-MVs that correlate with the age of the subjects and the correlation between miRNA expression and the process of renal fibrosis have not been established. The present study aimed to analyze differences in miRNA expression of BM-MSC-MVs between young or older rats and its influence on tumor growth factor-beta 1 (TGF-β1)-mediated epithelial-mesenchymal transition (EMT) of HK2 cells to explore the causes of renal fibrosis in aged tissues.
Methods: miRCURY LNA Array (version 18.0) was used to identify differentially expressed miRNAs in BM-MSC-MVs of 3- and 24-month-old Fisher344 rats. Reverse transcription-polymerase chain reaction was used to verify miRNA levels in BM-MSC-MVs and in the serum of rats. A TGF-β1-mediated EMT model was used to study the effects of BM-MSC-MVs and differentially expressed miRNAs on EMT.
Results: BM-MSCs from older rats showed more severe aging phenotypes compared with those of young rats. In addition, the growth rate and cell migration of BM-MSCs derived from older rats were significantly reduced. In secreted BM-MSC-MVs, the expression of miR-344a, miR-133b-3p, miR-294, miR-423-3p, and miR-872-3p was significantly downregulated in older rats than in younger rats (P < 0.05), and the serum level of these miRNAs exhibited the same patterns. Intervention using BM-MSC-MVs resulted in the weakening of TGF-β1-mediated EMT in the aged rats. MiR-344a, miR-133b-3p, and miR-294 affected TGF-β1-mediated EMT in HK2 cells. Among these, miR-133b-3p and miR-294 significantly inhibited TGF-β1-mediated EMT in HK2 cells (P < 0.05).
Conclusions: In older rats, the inhibitory effect of BM-MSC-MVs on TGF-β1-mediated HK2 cell EMT was weaker than that observed in younger rats. In addition, miR-133b-3p and miR-294, which were downregulated in BM-MSC-MVs of older rats, remarkably inhibited TGF-β1-mediated EMT in HK2 cells, suggesting that these may play a role in the fibrosis of aging renal tissues.