Transforming growth factor β1-induced changes in cell migration, proliferation, and angiogenesis in the chicken chorioallantoic membrane

Abstract

Application of TGFβ1 (10-100 ng) to the chicken chorioallantoic membrane (CAM) for 72 h resulted in a dose-dependent, gross angiogenic response. The vascular effects induced by TGFβ1 were qualitatively different than those induced by maximal doses of basic FGF (bFGF) (500 ng). While TGFβ1 induced the formation of large blood vessels by 72 h, bFGF induced primarily small blood vessels. Histologic analysis revealed that TGFβ1 stimulated pleiotropic cellular responses in the CAM. Increases in fibroblast and epithelial cell density in the area of TGFβ1 delivery were observed as early as 4 h after TGFβ1 treatment. By 8 h, these cell types also demonstrated altered morphology and marked inhibition of proliferation as evidenced by 3H-thymidine labeling. Thus, the TGFβ1-stimulated accumulation of these cell types was the result of cellular chemotaxis from peripheral areas into the area of TGFβ1 delivery. Microscopic angiogenesis in the form of capillary sprouts and increased endothelial cell density first became evident at 16 h. By 24 h, capillary cords appeared within the mesenchyme of the CAM, extending towards the point of TGFβ1 delivery. 3H-thymidine labeling revealed that the growth of these capillary cords was due to endothelial cell proliferation. Finally, perivascular mononuclear inflammation did not become evident until 48 h of treatment, and its presence correlated spatially and temporally with the gross and histological remodelling of newly formed capillary cords into larger blood vessels. In summary, these data suggest that, in the chicken CAM, TGFβ1 initiates a sequence of cellular responses that results in growth inhibition, cellular accumulation through migration, and microvascular angiogenesis.