Mesenchymal stem cell treatment promotes the proliferation of parenchymal cells and attenuates CD68+cell infiltration and TUNEL-positive cells, but conditioned medium administration has no beneficial effect. (a) Images of the immunofluorescent staining of KI67+ cells (yellow arrows) in the injured kidneys of mice on day 3 after ischemia–reperfusion (I/R) injury in the mesenchymal stem cell (MSC) group, vehicle group, conditioned medium (CM) group and Dulbecco’s modified Eagle’s medium (DMEM) group. (A) Number of KI67+ cells in the four groups on days 3, 5 and 7 after I/R injury. (b) Representative confocal images of the immunofluorescent staining of CD68+ cells (yellow arrow) in the injured kidneys of mice on day 3 after I/R injury in the MSC group, vehicle group, CM group and DMEM group. (A) Number of CD68+ cells in the four groups on days 3, 5 and 7 after I/R injury. (c) Effect of different treatments on I/R-induced tubular apoptosis on day 3 after injury. Kidneys from mice treated with MSCs, vehicle, CM and DMEM were stained using the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. (A) Number of TUNEL+ cells in the four groups at different time points. Data presented as mean ± standard deviation. *P < 0.05 versus the vehicle group, #P < 0.01 versus the vehicle group (bars, 250 μm).