Vascular response to basic fibroblast growth factor when infused onto the normal adventitia or into the injured media of the rat carotid artery

Abstract

Immunohistochemical techniques localize basic fibroblast growth factor (FGF) in endothelial and smooth muscle cells of the common carotid artery. Thus, we studied the effect in rats of basic FGF infused for 14 days onto the adventitia or into the media in vivo. In untreated rats, the adventitial layer is uniform, and few vessels are observed in cross sections (mean ± SEM is 0.351 ± 0.16 capillaries/field at a magnification of x480). Whereas saline infusion increases the mean number of vasa vasorum to 2.73 ± 0.011 capillaries/field (p < 0.01), basic FGF (1 ng/μl/hr) increases the capillary number to 13.4 ± 0.67 capillaries/field. The effects are local and restricted to the site of delivery; no cell proliferation is observed even 2 mm from the site of infusion. There is also no evidence of the infiltration of macrophages and monocytes. In an effort to determine the effect of basic FGF in the media, a small longitudinal (1-mm) incision was made in the adventitia, and saline or basic FGF (1 ng/μl/hr) was infused for 14 days into the arterial wall. Under these conditions, basic FGF is a potent inducer of smooth muscle cell proliferation in the vascular wall as well as of new capillaries. In these instances, however, the capillaries formed are thick-walled. The results support the hypothesis that basic FGF may be contributing to the growth and maintenance of the vasa vasorum and of vascular smooth muscle cells.