Abstract 21276: Human Embryonic Stem-cell derived Cardiomyocytes Engulf Apoptotic Cardiomyocytes while Retaining Contractile Function
Apoptosis plays a role in multiple diseases including in myocardial infarction and heart failure. Apoptosis is important in embryogenesis, and may be exaggerated in tissues undergoing extensive remodeling such as the fetal cardiac conduction system. Absence of apoptotic cell clearance by neighboring cardiac cells leads to an inflammatory response and is thought to underlie diseases such as congenital heart block due to transplacental passage of maternal anti Ro/La antibodies. We assessed the hypothesis that human embryonic stem cells derived cardiomyocytes (hESC-CMs) are capable of engulfment of apoptotic cells and may therefore serve as a unique model to study such disease processes. Apoptosis was induced in hESC-CMs by 1μM Staurosporine for 4-12 hours and was verified by typical morphologic changes and TUNEL confocal staining. The apoptotic cells were then labeled by DiO and added to healthy hESC-CMs for 18-24 hours. Engulfment was continuously assessed by time lapse microscopy. Multiple cardiomyocytes were found to contain DiO positive particles. hESC-CMs contractility and beating frequency were not affected by the engulfment of the apoptotic cells when compared to baseline recordings. FACS analysis of the cocultured healthy and apoptotic hESC-CMs revealed that 15-21% of the hESC-CMs were positive for DiO fluorescence, indicating engulfment of at least one apoptotic body. Staining with TUNEL, α-actinin antibodies and DAPI, revealed that several hESC-CMs displayed positive cytoplasmatic staining for TUNEL, indicating the engulfment of apoptotic cells (Figure). We conclude that healthy differentiating cardiomyocytes can function as physiologic scavengers and engulf apoptotic myocytes with preservation of their contractility. The capability of hESC-CMs to clear apoptotic cells may enable them to serve as an attractive model to study the role of this process in normal cardiac development and in various pathologies, such as congenital heart block.
- © 2010 by American Heart Association, Inc.