Delay in Apoptosome Formation Attenuates Apoptosis in Mouse Embryonic Stem Cell Differentiation

• Published in: The Journal of biological chemistry 2014-06, Vol.289 (24), p.16905-16913
• Main Authors: Akbari-Birgani, Shiva, Hosseinkhani, Saman, Mollamohamadi, Sepideh, Baharvand, Hossein
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Animals; Apoptosis; Apoptosomes - metabolism; ATP; Bioluminescence; Caspase; Caspases - genetics; Caspases - metabolism; Cell Biology; Cell Death; Cell Differentiation; Cell Line; Cytochromes c - genetics; Cytochromes c - metabolism; Embryonic Stem Cells - cytology; Embryonic Stem Cells - metabolism; Mice; Mice, Inbred C57BL; Mitochondrial Apoptosis; Myocytes, Cardiac - cytology; Myocytes, Cardiac - metabolism; Time Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.536730

Differentiation is an inseparable process of development in multicellular organisms. Mouse embryonic stem cells (mESCs) represent a valuable research tool to conduct in vitro studies of cell differentiation. Apoptosis as a well known cell death mechanism shows some common features with cell differentiation, which has caused a number of ambiguities in the field. The research question here is how cells could differentiate these two processes from each other. We have investigated the role of the mitochondrial apoptotic pathway and cell energy level during differentiation of mESCs into the cardiomyocytes and their apoptosis. p53 expression, cytochrome c release, apoptosome formation, and caspase-3/7 activation are observed upon induction of both apoptosis and differentiation. However, remarkable differences are detected in time of cytochrome c appearance, apoptosome formation, and caspase activity upon induction of both processes. In apoptosis, apoptosome formation and caspase activity were observed rapidly following the cytochrome c release. Unlike apoptosis, the release of cytochrome c upon differentiation took more time, and the maximum caspase activity was also postponed for 24 h. This delay suggests that there is a regulatory mechanism during differentiation of mESCs into cardiomyocytes. The highest ATP content of cells was observed immediately after cytochrome c release 6 h after apoptosis induction and then decreased, but it was gradually increased up to 48 h after differentiation. These observations suggest that a delay in the release of cytochrome c or delay in ATP increase attenuate apoptosome formation, and caspase activation thereby discriminates apoptosis from differentiation in mESCs. Background: The mitochondrial apoptotic pathway has a non-apoptotic role in cell differentiation. Results: Differentiation of mouse embryonic stem cells into cardiomyocytes passes through a mitochondrial pathway of apoptosis. Conclusion: The delayed mitochondrial apoptotic pathway in mouse embryonic stem cells delivers cells into differentiation, not cell death. Significance: Such a comparative study could help to clarify ambiguities about the death-centric model of differentiation.