Entrapment of embryonic stem cells-derived cardiomyocytes in macroporous biodegradable microspheres: preparation and characterization.

Embryonic Stem (ES) cells-derived cardiomyocytes can possibly be applied for cell therapy of diseases such as heart failure. Biodegradable scaffolds will significantly improve the expansion of sufficient functional ES cell-derived cardiomyocytes and may also increase the survival rate of cardiomyocytes after their transplantation. In the present study, we cultivated cardiomyocytes isolated from a transgenic a-myosin heavy chain (alpha-MHC) ES cell lineage expressing both puromycin resistance and enhanced green fluorescent protein (EGFP) under the control of the alpha-MHC promoter in macroporous gelatine microspheres using small-scale bioreactors and proved that cardiomyocytes function after their cultivation in micropsperes. The average number of cultivated cells per microsphere was optimised once the most suitable agitation conditions and the optimal timeframe of cultivation were identified. Our study shows that 72% of CultiSpher-S beads were colonised by cardiomyocytes under optimal conditions. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) showed that colonization of the beads was not limited to the surface, but that cells also invaded the inner surfaces of the microspheres. Electrophysiological experiments demonstrated that the action potentials (APs) of alpha-MHC(+) cardiomyocytes entrapped in microspheres were identical to action potentials of control cells. This attractive approach for cultivation and expansion of functional cardiomyocytes in biodegradable macroporous may offer a perspective for higher transplantation efficiencies of ES cell-derived cardiomyocytes.