Human umbilical cord mesenchymal stem cell (hucMSC) exosomes suppressed renal cell apoptosis and promoted renal cell proliferation in cisplatin-induced acute kidney injury (AKI) rats. (A) Representative images of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL)-positive cells notably increased in the phosphate-buffered saline (PBS) and human lung fibroblast secreted exosomes (HFL-1-ex) groups compared to the hucMSC-ex group, while proliferating cell nuclear antigen (PCNA)-positive cells were clearly more numerous in the hucMSCs-ex group than the PBS and HFL-1-ex groups. Original magnification, × 200, Scale bars: 100 μm. (B) Western blot analysis of B cell lymphoma 2 (Bcl-2) protein and Bcl-2-associated X protein levels in the kidney tissues showed that Bax expression increased while the expression of Bcl-2 was reduced in the PBS and HFL-1-ex groups. This phenomenon was reversed in hucMSC-ex-treated group.