BS31 A snapshot of coronary development: human endocardium-derived angiogenesis

Introduction The heart's limited angiogenic potential hinders recovery post-injury, necessitating exploration of factors that enhance cardiac angiogenic capacity for heart disease treatment. Despite its clinical relevance, understanding of human coronary vasculature (hCV) development is limited. This study aims to shed light on early events in hCV formation, focusing on the differentiation of endocardium to coronary specific endothelial cells, forming a vital coronary network. Methods We employed a novel human embryonic stem cell (hESC)-derived endocardium (EndoC) differentiation protocol and utilised vascular endothelial growth factor A (VEGF-A), a known signalling reagent in endocardial-derived angiogenesis. HESC-EndoCs were differentiated into hESC-coronary endothelial cells (cECs) through 7-day exposure to VEGF-A (50 ng/ml) (termed- 'transitioning'). RT-qPCR analysis gauged hESC-cEC-specific marker expression pre- and post-transition. Functional assays evaluated the angiogenic capacity of transitioned hESC-cECs. Results High VEGF-A doses prompted significantly elevated gene expression of cEC-specific markers like Apelin and A2M compared to control. When plated in tube formation assays, post-transition cells formed more tubes than pre-transition cells, which tended to cluster into colonies. Post-transition hESC-EndoC spheroids, unlike pre-transitioned ones, sprouted in response to pro-angiogenic cues when embedded in a collagen/methylcellulose hydrogel. Transitioning in hypoxic conditions intensified sprouting network complexity. Conclusion Our study shows high VEGF-A doses promoted transition of hESC-EndoCs into hESC-cECs with improved coronary marker expression and angiogenic potential. However, a lower proportion of cells exhibited sprouting potential compared to HUVECs, suggesting incomplete transitioning. Future research will explore alternative signalling pathways that may work synergistically with VEGF-A to improve transitioning efficiency and thereby enhance our understanding of early endocardial-derived angiogenesis. Conflict of Interest None