Human umbilical cord mesenchymal stem cell (hucMSC) exosomes attenuated tubular oxidative damage in cisplatin-induced acute kidney injury (AKI) rats. (A) Immunohistochemistry was used to detect the oxidative stress marker 8-hydroxy-2′-deoxyguanosine (8-OHdG). The number of 8-OHdG-positive cells decreased in hucMSC-ex-treated rats compared to untreated rats. Original magnification, × 200, Scale bars: 100 μm. (B) Quantitative analysis of 8-OHdG-positive cells indicated that hucMSC-ex reduced cisplatin-induced kidney oxidative damage. Analysis of variance (ANOVA) was performed with the Student-Newman-Keuls multicomparison test. ***P <0.001. (C) Glutathione (GSH) and malondialdehyde (MDA) levels were examined in kidney tissue homogenates with the respective detection kits (see Methods). GSH expression was reduced, while MDA content increased in the phosphate-buffered saline (PBS) and human lung fibroblast secreted exosomes (HFL-1-ex) groups, but this phenomenon was reversed in the hucMSC-ex group. ANOVA was performed with the Student-Newman-Keuls multicomparison test. **P <0.01, ***P <0.001. (D) Western blot analysis showed that the expression of p-p38 and caspase 3 was higher in the PBS and HFL-1-ex group, while it was suppressed by hucMSC-ex. It indicated that hucMSC-ex inhibited activation of p38 mitogen-activated protein kinase (p38MAPK) by cisplatin-induced oxidative stress and suppressed p38MAPK induced caspase 3 expression, thereby decreasing cell apoptosis.