Comparison of BAX and Bcl-2 Expression During Human Embryonic Stem Cell Differentiation into Cardiomyocytes and Doxorubicin-induced Apoptosis

Back ground: Although the cell differentiation is an inseparable part of development in multicellular organisms, the regulating molecular pathway of it still is not fully defined. In the other hand, apoptosis is a fundamental physiological process which plays an essential role in a variety of biological events during development. Moreover, recent studies have found that apoptosis shows several common features with differentiation but that how cells distinguish apoptosis and differentiation from each other is not clear. In this study two critical members of the Bcl-2 family, BAX (an apoptosis promoter) and Bcl-2 (an apoptosis inhibitor) ratio was investigated in both apoptosis and differentiation processes. BAX/ Bcl-2 ratio is one of the important characteristics of the apoptosis process but its role during differentiation is still unknown. Materials and methods: At the present study hESC (human embryonic stem cell) line RH5 was used for induction of differentiation into the beating cardiomyocytes and also doxorubicin induced apoptosis. Samples were collected at different time points and their total RNA was extracted and RT-PCR was performed to assess the expression of genes of interest. Results: During apoptosis BAX mRNA level increased but Bcl-2 mRNA level decreased and consequently BAX /Bcl-2 ratio increased significantly (p<0.05) about 8 fold, 24 hours after apoptosis induction. But interestingly BAX /Bcl-2 ratio fluctuated during differentiation of beating cardiomyocytes. Conclusion : It seems that BAX /Bcl-2 ratio and the time of its engagement may contribute to the choice between cell death and differentiation in hESC.