Abstract P012: KDR Expression Enhances Commitment Toward the Cardiac Lineage of hESC- and iPS-Derived Cd15 + Progenitors

Cell-based therapies represent exciting therapeutic options for myocardial regeneration after ischemic injury. Although many cell types have been proposed as a source of cardiac myocytes, the type of progenitor as well as the optimal conditions for their stimulation still represent major challenges. Moreover, molecular characterization of cardiac progenitors (CP) in vitro is still unsatisfactory: the identification of novel surface markers for their selective isolation is of utmost importance. In our study we employed different human ESCs and induced pluripotent stem (iPS) cells lines to set up a simple, reliable and efficient protocol to selectively induce cardiac fate in vitro. At first, we comparatively applied different methods and monitored the differentiation process by FACS analysis, RT-PCR and immunofluorescence for early and late markers. Our results show that sequential treatments with ActivinA and BMP4 or BMP2, ascorbic acid and TGFβ1 in a specific media formulation induce CD15 + cardiac progenitor population with an enhanced cell vitality compared to other methods. While we confirmed that CD15 is among the earliest markers upregulated after differentiation, the definition of other associated markers could better specify progenitors committed toward cardiomyogenesis. For this purpose, we systematically evaluated induction of other markers already shown associated with cardiac differentiation or heart development, that is PDGFRα, KDR, Sca1, CXCR4, cKIT. Our result demonstrate that a specific population expressing both KDR and CD15 surface markers is more committed toward cardiovascular lineages. The induced KDR + /CD15 + cell population exhibits higher levels of Gata4 and Isl1 expression (2-fold induction), compared to the KDR − /CD15 + counterpart and, after isolation, gives rise to 66.15% Troponin I positive cells (43 out of 65 in a single representative experiment), against the 26.5% (18 out of 68) detectable in the KDR − /CD15 + population. In conclusion, our studies, though preliminary, strongly indicate that KDR in CD15 + progenitor cells is an earlier marker of cardiomyogenesis.