Endostatin, but not TSP-1 or IP-10, can inhibit VEGF-induced tube-formation on collagen I gels. HDMEC were seeded on collagen I gels, and following removal of non-adherent cells by washing, were stimulated with media alone (unstimulated) or media containing 50 ng/ml VEGF alone or in combination with 50 ng/ml TSP-1, 80 ng/ml IP-10 or 500 ng/ml endostatin. Cells were counted daily and media was replenished every second day. Graph is representative of the mean and standard error of the number of sprouts counted in 12 random fields of view at 100× magnification in triplicate dishes (n = 24). Statistical significance was determined at day 12 using unpaired t-tests as compared to VEGF treated cells (* = p < 0.05).