Human umbilical cord mesenchymal stem cell (hucMSC) exosomes depressed cisplatin-induced NRK-52E cell oxidative damage in vitro . (A) Immunohistochemistry was used to measure levels of the oxidative stress marker 8-hydroxy-2′-deoxyguanosine (8-OHdG). The number of 8-OHdG-positive cells was raised in the cisplatin and human lung fibroblast secreted exosomes (HFL-1-ex) groups compared to the control group, which was reduced by hucMSCs-ex. Original magnification, × 200, Scale bars: 100 μm. (B) Quantitative analysis of 8-OHdG-positive cells indicated that hucMSC-ex inhibited cisplatin-induced NRK-52E cell 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 cell homogenates. GSH levels decreased and MDA levels increased in the cisplatin and HFL-1-ex groups; this was reversed in hucMSC-ex. ANOVA was performed with the Student-Newman-Keuls multicomparison test. **P < 0.01, ***P < 0.001. (D) Western blot results showed that p-p38 and caspase 3 expression were lower in the hucMSC-ex group than in the cisplatin and HFL-1-ex groups, which demonstrated that hucMSC-ex suppressed activation of p38 mitogen-activated protein kinase (p38MAPK) by cisplatin-induced oxidative stress and depressed the expression of caspase 3, which is increased by p38MAPK.