Characterization and cytoprotective effects against anoxia of MK-transduced mesenchymal stem cells. (A) Flow cytometry analysis of the efficiency of lentivirus affection. Black: MSCs, green: MSCs-GFP, blue: MSCs-MK two generations after lentivirus infection, red: MSCs-MK four generations after lentivirus infection. (B) Quantitative real-time polymerase chain reaction of MK expression. (C) Western blot of MK protein levels. (D) ELISA of MK protein levels in the culture supernatants of MSCs, MSCs-GFP and MSCs-MK. (E) Flow cytometry analysis of cell apoptosis in all groups. MSC, mesenchymal stem cell; MSCs-MK, MSCs overexpressing midkine. The data are shown as the means ± SEM of three independent experiments. ***p< 0.01 versus control. MSCs-GFP, Mesenchymal stem cells-green fluorescent protein; MSCs-MK, Mesenchymal stem cells-midkine.