OBJECTIVEIn order to understand the effects of cardiac microenvironment on the differentiation of bone marrow mesenchymal stem cells (MSCs) into myocardial-like cells, we simulated the cardiac microenvironment in vitro by adding myocardial cell lysate into the culture system of MSCs, and compared the differentiation promoting effect of myocardial cell lysate with that of well-established inducer 5-azacytidine (5-aza).

METHODSMyocardial cells isolated from newly born rats were lysed by repeat freezing and defrosting. MSCs isolated from adult rat were cultured in four different systems. Medium A: medium with myocardial cell lysate; medium B: medium with 5-aza; medium C: medium with 5-aza and myocardial cell lysate; and control medium: ordinary medium without any addition reagent. The dynamic changes of MSCs morphology in different media were observed within 7 days after introduction of MSCs. Immunohistochemical staining against alpha-actin, cTnT, Connexin43 and CD31 were performed at the end of cultivation.

RESULTSMSCs in both medium A and B were differentiated into myocardial-like cells expressing alpha-actin and cTnT after 7-day cultivation. Cells in medium A developed more myofilaments than those in medium B, and expressed CD31, whereas cells in medium B did not. MSCs in control medium only expressed alpha-actin.

CONCLUSIONSMyocardial cell lysate is an ideal inducer to differentiate MSCs into myocardial-like cells in vitro. The differentiation promoting effect of myocardial cell lysate is more predominant than that of 5-aza.