Extracellular matrix dependence of organization of the cardiomyocyte contractile apparatus

In the process of cardiomyocyte cultivation, there occurs rearrangement of their contractile apparatus with transformation of typical myofibrils into structures of nonmuscle type and with subsequent restoration of the initial organization. The causes and mechanisms of the rearrangements described are unknown. In this study, it was shown that, at cultivation of cardiomyocytes on the individual proteins of the extracellular matrix (ECM), as well as on the matrix produced either by cardiac fibroblasts or by similar cardiomyocytes, the period in which the contractile apparatus is in a converted state is shortened, whereas soluble factors of the conditioned cultural medium do not produce any obvious effect on the above-indicated rearrangements. Using the method of extracellular matrix isolation adapted for cardiomyocytes, we have confirmed that, in the process of cultivation, cardiomyocytes themselves produce ECM that differs from ECM of cardiac fibroblasts by composition and varies with culturing time.