Endocardial chamber differentiation: Cell proliferation.

VERÓNICA A. LOMBARDO; ANN-CHRISTIN DIETRICH; SALIM ABDELILAH-SEYFRIED

Madrid

Congreso; Weinstein Cardiovascular Conference; 2014

During vertebrate embryonic development, the primitive heart tube is comprised of cardiomyocytes and of endocardium, a specialized population of endothelial cells that line the interior of the primitive heart tube. The onset of a heartbeat and blood flow coincides with an enlargement, S-shaping and an incongruent ballooning of the atrial and ventricular cardiac chambers. We use zebrafish as a vertebrate model to analyze the molecular mechanism(s) underlying the process of endocardial cell growth during chamber development. We have combined functional manipulations, fate mapping studies, and high-resolution imaging in zebrafish to show that in striking contrast to the growth of the myocardium, which is mainly due to the addition of cells derived from the secondary heart field, endocardial growth occurs without an influx of external cells. Our functional studies reveal that endocardial cell numbers during chamber ballooning stages are regulated by blood flow in a manner independent of Vegf-dependent angiogenesis signaling. These findings establish the endocardium as the flow-sensitive tissue in the heart with a key role in adapting chamber growth in response to the mechanical stimulus of blood flow.