Co-cultivation of H9c2 cells with MSCs decreased cell death. (A) Experimental layouts after in vitro ischemia. (B) The ratio of dead H9c2 cells was significantly smaller when MSCs were added after OGD (0.85 ± 0.086 vs. 0.16 ± 0.035, n = 5), but MSCs added in cell culture inserts did not decrease significantly the ratio of dead H9c2 cells (0.90 ± 0.055, n = 5). Data represent mean ± SEM. *p < 0.05 C+MSC vs. C and C+MSC vs. C+MSC ins. (C: H9c2 cells only; C+MSC: H9c2 cells and MSCs; C+MSC ins: H9c2 cells and MSCs in cell culture inserts) (C) Absolute number of live H9c2 cells before and after OGD shows that before OGD the H9c2 cells were close to confluence (63,120 ± 7,694) and there was little increase in cell numbers during the next 24 hours if the cells were left to grow without OGD (76,116 ± 3,396). 24 hours after OGD the number of viable cells was very low when cultured alone or with MSCs in cell insert (1,757 ± 1,081 and 990 ± 608 respectively), which was significantly increased (15,174 ± 3,975) if MSCs added directly. (D) MSCs labeled with Vybrant DiD were growing on cell culture inserts in the same manner as under normal culture conditions after 24 hours of cultivation. Scale bar represents 100 μm.