Exosomes Secreted by Normoxic and Hypoxic Cardiosphere-derived Cells Have Anti-apoptotic Effect

Cardiosphere-derived cells (CDCs) have emerged as one of the most promising stem cell types for cardiac protection and repair. Exosomes are required for the regenerative effects of human CDCs and mimic the cardioprotective benefits of CDCs such as anti-apoptotic effect in animal myocardial infarction (MI) models. Here we aimed to investigate the anti-apoptotic effect of the hypoxic and normoxic human CDCs-derived exosomes on induced apoptosis in human embryonic stem cell-derived cardiomyocytes (hESC-CMs). In this study, CDCs were cultured under normoxic (18% O2) and hypoxic (1% O2) conditions and CDC-exosomes were isolated from conditioned media by differential ultracentrifugation. Cobalt chloride as hypoxia-mimetic agents at a high concentration was used to induce apoptosis in hESC-CMs. The caspase-3/7 activity was determined in apoptosis-induced hESC-CMs. The results indicated that the caspase-positive hESC-CMs were significantly decreased from 30.63 ± 1.44% (normalized against untreated cardiomyocytes) to 1.65 ± 0.1 and 1.1 ± 1.09 in the presence of normoxic exosomes (N-exo) at concentration of 25 and 50 μg/mL, respectively. Furthermore, hypoxic exosomes (H-exo) at concentration of 25 and 50 μg/mL led to 8.75 and 12.86 % reduction in caspase-positive cells, respectively. The anti-apoptotic activity of N-exo at the concentrations of 25 and 50 μg/mL was significantly higher than H-exo. These results could provide insights into optimal preparation of CDCs which would greatly influence the anti-apoptotic effect of CDC-exosomes. Totally, CDC-secreted exosomes have the potential to increase the survival of cardiomyocytes by inhibiting apoptosis. Therefore, CDC-exosomes can be developed as therapeutic strategy in ischemic cardiac disease.