Many developmental studies have focused on the role of Ca2+ signaling in early events after fertilization. Studies performed till now in both embryos and embryonic stem (ES) cell differentiating to cardiomyocytes have uncovered the role of Ca2+ in cardiac development in mouse. The data of the present study using ES cells suggest that the biological effects of Ca2+ through p44/42 MAPK activation on cardiac cell differentiation and proliferation. It was been found that expression of cardiac transcription factors increased when 10 μM ionomycin was added to the cell culture medium and significantly inhibited by adding 50 μM BAPTA. The decrease in expression of transcription myocyte enhancer factor C2 (Mef2c), GATA4 and Nkx2.5 that initiates the program for cardiac gene expression for cardiomyocyte differentiation, resulting in an impaired cardiomyocytes differentiation and organization of myofibrils. To further investigate the relation between cytosolic [Ca2+]c and the cardiac sarcomeric genes and protein expression of ES cells were analysed by reverse transcription-polymerase chain reaction (RT-PCR) and western blot. The results showed that the cahnge of cardiac transcription factors expression accompanied with change in genes and protein expression of α-myocine havey chain (α-MHC), ß-MHC, cardiotropinin T and ventricular myosin light chain 2 (MLC2v) but not in gene and protein expression of atrial myosin light chain 2 (MLC2a). Interestingly, treatment the EBs with Ca2+ ionophore, to elicit an increase in [Ca2+]c, for 2 days after treatment the EBs for 5 days with Ca2+ chelator could partially rescue but not completely the effect of absence a Ca2+ in early time of cardiac development. In conclusion, these data suggest that signaling pathways involved in embryonic cardiomyogenesis are affected by Ca2+ concentration during the heart development.
Key words: Embryonic stem cell, Ca2+, cardiac development
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