Human embryonic heart (43 days), CD 34, vimentin, CD105, desmin and CD31 immune labeling.

<p>Immune labeling with CD34 (A) and vimentin (B) antibodies of a 43 days human embryonic heart, oblique-sagittal cut at ventricle level. Corresponding epicardial vascular canals are indicated (white arrrows and white arrowheads). The walls of these canals seem to acquire a CD34-positive phenotype and are vimentin-positive. In (A) an active intramyocardial process of sprouting angiogenesis is detailed (inset), being guided by tip cells (double-headed arrows). CD105 immunolabeling of the ventricular wall (C) identifies filopodia-guided processes (arrows) of endocardial sprouting. Desmin-positive reactions were exclusively found (D) in the dorsal wall of the venous sinus (arrows) and in the atrioventricular ring (arrowheads) (VS: venous sinus; RA: right atrium; RV: right ventricle; avc: atrioventricular cushion). CD31-positive endocardial (arrows) and vascular (arrowhead) endothelia were identified. α-SMA intense labeling of the venous sinus (VS) myocardium (arrow) but not of subepicardium (arrowhead).