(A) 7-day-old control aortic ring culture; (B) culture treated with 5 ng/ml TNFα; (C) culture treated with 100 ng/ml TNFα: TNFα has concentration-dependent stimulatory or inhibitory effects on growth of microvessels (arrows). (D) Microvessel counts demonstrate >100% stimulation of angiogenesis over time by 5 ng/ml TNFα (N=4). (E) Treatment of aortic cultures with increasing doses of TNFα identifies 5 ng/ml as the optimal pro-angiogenic dose and demonstrates reduced TNFα efficacy at higher doses, with the highest dose having anti-angiogenic activity (N=4). (F, G) Over time, the proangiogenic dose of TNFα induces the formation of a dense periaortic outgrowth which forms a patch (asterisk) on the bottom of the culture dish (G); this outgrowth is less pronounced in the unstimulated control (F). (H) The TNFα-induced aortic patch is composed of a uniform population of CD68+ macrophages. (I) Studies with the thymidine analogue EDU demonstrate occasional labeled nuclei (green) in CD68+ macrophages (red) of untreated control culture. (J) Macrophages exhibit a higher rate of proliferation in TNFα-treated cultures. (K) Bar graph shows quantitative analysis of macrophage (MΦ) proliferation in CD68 stained control and TNFα-treated aortic cultures (N=10). Magnification bars = 500 µm (A, B, C, F, G), 100 µm (H, I, J). * p<0.05, ** p<0.01, *** p<0.001.