Angiogenesis in rat aortic rings stimulated by very low concentrations of serum and plasma

Arterial ring cultures are evaluated for assay of angiogenic activity in physiological fluids. A simplified image analysis algorithm involving public domain software is used to measure microvessels sprouting from rat aortic rings embedded in fibrin. Low concentrations (<1% v/v) of serum and plasma stimulate angiogenesis primarily from the adventitia in a dose-dependent manner. Half-percent serum is more potent than optimal concentrations of some of the important known growth factors, including platelet derived growth factor, vascular endothelial growth factor and basic fibroblast growth factor. Sera and plasmas obtained from rodent, bovine, porcine or human sources have comparable angiogenic activities. The angiogenic activity is found to be heat stable, non-dialyzable and on gel chromatography is co-eluted with albumin. However, purified albumin and the essential fatty acids linoleic and linolenic acids have no effect on angiogenesis. It is concluded that rat aortic rings sprout microvessels, primarily from the adventitia, when cultured with serum or plasma in concentrations below those that support cell culture. Accordingly, the aortic ring assay is a promising system to support isolation of angiogenic factors from blood and other physiological fluids.