Cardiac stem cell secretome protects cardiomyocytes from hypoxic injury partly via monocyte chemotactic protein-1-dependent mechanism

Cardiac stemcells (CSCs)were known to secrete diverse paracrine factors leading to functional improvement and beneficial left ventricular remodeling via activation of the endogenous pro-survival signaling pathway. However, little is known about the paracrine factors secreted by CSCs and their roles in cardiomyocyte survival during hypoxic condition mimicking the post-myocardial infarction environment. We established Sca-1+/CD31- human telomerase reverse transcriptase-immortalized CSCs (Sca-1+/CD31- CSCs^hTERT), evaluated their stem cell properties, and paracrine potential in cardiomyocyte survival during hypoxia-induced injury. Sca-1+/CD31- CSCs^hTERTsustained proliferation ability even after long-term culture exceeding 100 population doublings, and represented multi-differentiation potential into cardiomyogenic, endothelial, adipogenic, and osteogenic lineages. Dominant factors secreted from Sca-1+/CD31- CSCs^hTERT were EGF, TGF-β1, IGF-1, IGF-2, MCP-1, HGF R, and IL-6. Among these, MCP-1 was the most predominant factor in Sca-1+/CD31-CSCs^hTERT conditioned medium (CM). Sca-1+/CD31- CSCs^hTERT CM increased survival and reduced apoptosis of HL-1 cardiomyocytes during hypoxic injury. MCP-1 silencing in Sca-1+/CD31- CSCs^hTERT CM resulted in a significant reduction in cardiomyocyte apoptosis. We demonstrated that Sca-1+/CD31- CSCs^hTERT exhibited long-term proliferation capacity and multi-differentiation potential. Sca-1+/CD31- CSCs^hTERT CM protected cardiomyocytes from hypoxic injury partly via MCP-1-dependent mechanism. Thus, they are valuable sources for in vitro and in vivo studies in the cardiovascular field.