Abstract 14422: CXCR4 Identifies Heart Field-specific Cardiac Progenitor Cells

Introduction: Congenital heart disease is the most common birth defect (1% of live born infants) and most children, who survive to adulthood, will develop severe heart failure. At present, heart transplantation is the only definite treatment for advanced heart failure patients. Heart development involves an early assignment of two distinct cellular populations, called cardiac progenitor cells (CPCs), which generate the first and the second heart field and subsequently the left and right ventricular heart chamber, respectively. Nevertheless, a comprehensive understanding of CPCs for the study of cardiogenesis and the mechanisms of congenital heart defects as well as the development of regenerative cell therapies for heart disease are currently missing. Study Aim: We decided to characterize the second heart field population and develop a method for the isolation of chamber-specific CPCs. Results: With a candidate approach based on gene expression patterns and lineage trace analysis, we found that CPCs positive for CXC chemokine receptor 4 (CXCR4) are specified in the second heart field and contribute to the right ventricle and outflow tract development. Similarly, we found two distinct populations of CXCR4 positive and negative cells specified in differentiating human and mouse pluripotent stem cell cultures. Gene expression analysis revealed that CXCR+ CPCs express markers of the second heart field (Tbx1, Fgf10 and Fgf8), whereas CXCR4- CPCs express first heart field genes (Tbx5, HCN4 and Nkx2.5). In addition, by single cell analysis we discovered that CXCR4+ CPCs are more proliferative, multipotent and differentiate into all major cardiac lineages (endothelial cells, fibroblasts, cardiomyocytes and smooth muscle cells), whereas CXCR4- CPCs give rise primarily to cardiomyocytes. Finally, using both in vitro and ex vivo migration assays we identified that the CXCR4 ligand SDF1, is necessary for the proper migration of CPCs towards the right ventricle and outflow tract. Conclusions: Collectively, our results provide fundamental insights into the development of the second heart field and demonstrate for the first time the isolation of chamber-specific CPCs using pluripotent stem cells for disease modeling and cell replacement therapies.