Desmin-positive pericytes in the chick embryo chorioallantoic membrane in response to fibroblast growth factor-2.

Pericytes stabilize vessel wall, participate in the regulation of blood flow microcirculation and influence endothelial proliferation, survival, migration and maturation. Pericytes are commonly identified by molecular markers, such as desmin. The aim of this study was to analyze the pattern of distribution of desmin in the chick embryo chorioallantoic membrane (CAM) vasculature in normal condition and in response to an angiogenic cytokine, such as fibroblast growth factor-2 (FGF-2) by using conventional immunohistochemistry and confocal laser scanning microscopy. Results indicate that, in normal condition, the desmin-positive pericytes are located around the endothelial cells of the capillary plexus and of larger vessels in the intermediate mesenchyme. In response to FGF-2 numerous desmin-positive and alpha smooth muscle actin-negative cells are located in the mesenchyme and numerous blood vessels positive to factor VIII and desmin are recognizable near to the gelatin sponge soaked with FGF-2. These data suggest that pericytes in normal condition intervene to stabilize the wall of newly formed blood vessel, while in response to FGF-2, they detach from the wall of parental vessels and migrate, as extramural fibroblast-like desmin-positive cells, in the surrounding mesenchyme, where they modulate the angiogenic response.