Abstract 137: VCAM1 and SIRPA Cell Surface Markers of Human Cardiomyocytes

Heart disease is the leading cause of mortality and morbidity in the Western world. The human heart has a limited regenerative capacity and there is an unmet demand for improved therapies for myocardial disease. Human stem cell derived cardiomyocytes have potential to facilitate the development of both cell based and pharmaceutical treatments. To date many studies have focused on the efficient generation of cardiomyocytes from pluripotent hESCs and iPSCs. Efficient in vitro differentiation of human cardiomyocytes is becoming a standard technique and hESC derived cardiomyocytes are beginning to be used in cardiotoxicity screens. In order to capitalise on these advances in cardiomyocyte generation and ensure the transfer of this technology into biopharmaceutical and clinical settings, enriched and well defined cell populations are required. Therefore, cell surface markers that allow the facile purification of cardiac cell lineages are needed. This work investigates the potential of two novel cell surface markers, SIRPA and VCAM1, in isolating enriched populations of committed human cardiomyocytes. The NKX2-5GFP/w reporter line was used to characterise the temporal expression, gene expression profiles and functional properties of SIRPA and VCAM1 cell populations that are found during cardiac differentiation. We demonstrate that fully functional cardiomyocytes arise from an NKX2-5+SIRPA+ intermediate which up regulates VCAM1 concomitantly with commitment to the myogenic lineages of the heart (ie. smooth and cardiac muscle). Under the culture conditions used in this study, the NKX2-5+SIRPA+ population had a higher single cell clonogenic potential and displayed the capacity to give rise to both smooth muscle and cardiac clones. Furthermore, when cultured as re-aggregates the majority of NKX2-5+SIRPA+ cells progressed to a NKX2-5+SIRPA+VCAM1+ phenotype thus demonstrating lineage relationship of these two cell populations. The identification of these cell surface markers provide a means for further study of linage specification during in vitro human cardiogenesis and will facilitate the development of technologies to produce well-characterised, purified human cardiomyocytes.