rHuEpo stimulates angiogenesis in the chick embryo CAM. CAM of 12-day-old chick embryo incubated for 4 days with a gelatin sponge adsorbed with 10 U of rHuEpo. Note the presence of an increased number of blood vessels with a radially arranged spoked wheel pattern around the implant. (B) CAM of 12-day-old chick embryo incubated for 4 days with a sponge adsorbed with vehicle alone (PBS) used as negative control. No vascular response is detectable around the sponge. (C) Histological section of a gelatin sponge treated with 10 U of rHuEpo. Note the collagenous matrix containing numerous capillaries among the sponge trabeculae and a cellular infiltrate prevalently formed by fibroblasts. (D) Histological section of a sponge treated with PBS. No collagenous matrix, blood vessels, or fibroblasts are detectable. Bar for (A) and (B) is 25 μm and for (C) and (D) is 12.5 μm.