Effect of dedimethyloxalylglycine preconditioning on cell death in vitro and after transplantation. (A) Hydrogen peroxide (H2O2)-induced cell death was measured in bone marrow mesenchymal stem cell (BMSC) cultures with and without dedimethyloxalylglycine (DMOG) preconditioning. After different durations of DMOG (1 mM) treatment, cell death was induced by H2O2 (100 μM) in a serum-free medium for 90 minutes. The membrane-permeable dye Trypan Blue was added 5 to 10 minutes before cell death measurement. Damaged BMSCs were identified as cells unable to exclude the blue color dye from the cytosol. n =3 independent tests in each time group. *P <0.05 compared with C-BMSC group. #P <0.05 compared with basal control group. (B) to (E) Green fluorescent protein (GFP)-positive BMSCs (green) were labeled with Hoechst 33342 (blue) before transplantation to further facilitate tracking transplanted cells. Cell death was evaluated 24 hours after transplantation using terminal deoxynucleotidyl transferase biotin-dUPT nick end labeling (TUNEL) staining (red) in heart sections. Co-labeling of GFP/Hoechst/TUNEL fluorescence was designated as transplanted dead BMSCs. (F) Summarized cell count data of GFP/Hoechst/TUNEL-positive cells against total exogenous (GFP/Hoechst-positive) cells. n =4 independent experiments in each group. *P <0.05 compared with C-BMSC group.