Morphology and viability of H9c2 cells 24 hours after OGD. (A) DiO-labeled H9c2 cells without MSCs observed 24 hours after OGD were predominantly rounded up and stained with ethidium homodimer indicating cell death in progress. (B) Flow cytometry analysis of control and ischemic H9c2 cells cultured for 24 hours after OGD labeled with ethidium homodimer (ex/em 528/617 nm) showed that the number of dead H9c2 cells was elevated compared to the control group (median fluorescence from 19 to 65 units). (C) Co-cultivation of DiO-labeled H9c2 (ex/em 488/501 nm) cells and DiD-labeled MSCs (ex/em 633/665 nm) for 24 hours after OGD showed that the morphology of ischemically damaged cells were normal after 24 hours. (D) Flow cytometry analysis revealed that after co-cultivation of cells the number of dead H9c2 cells remained on the control level (median fluorescence 24 versus 23 units).