ABSTRACT
Stem cell biology has been the subject of much recent discussion. Embryonic stem [ES] cells, derived from the inner cell mass of the blastocyst stage of early mammalian embryos are expected to become a powerful tool in future regenerative medicine and developmental biology due to their capacity of selfrenewal and pluripotency. In the present study, the ultrastructural development of mouse ES cell derived cardiomyocytes was compared with invivo cardiomyocytes.. Cardiomyocytes were derived from mouse ES line [Royan B1] which developed spontaneously. The cultured cardiomyocytes were processed 3, 7, 14 and 21days after plating [day 7] for immuno histochemistry and transmission electron microscopy [TEM]. The in vivo cardiomyocytes were derived from16 days old fetuses and 2 and 8 days old pups. The beating cells expressed alpha-actinin. The maturation of the ultrastructure of cardiomyocytes depended on enhancement of development and expressed as myofibrillar bundle organization and exhibited intercalated discs, Z-disc, A, I, and H-bands, and M-line. While 7+21 days old cardiomyocytes showed all sarcomeric components such as A, I, and H-bands, Z-disc, and also M-line, T-tubule, sarcoplasmic reticulum and intercalated discs, early stage [7+3d, 7+7d and 7+14d] cardiomyocytes had few primary characteristics of subcellular structure. In fetal and 2-days old pups, the M-line was not visible. M-line was present in 8-days old pups frequently. Based on our data, mature cardiomyocytes can be produced from ES cells, and ES cell provide a good model for cardiomyocyte development. The cells can be used for cell therapy in future