Fig. 7. BMP-9 blocks endothelial network formation. Metatarsals of 17-day-old mouse foetuses were prepared, transferred to cell culture plates and allowed to adhere for 4 days. Medium was refreshed and bones were stimulated for 7 days with BMP-9 (100 ng/ml), VEGF (50 ng/ml) or both. Cultures were fixed and vessel-like structures were visualised by anti-CD31 staining. BMP-9 inhibits baseline formation of the endothelial network. Incubation with VEGF strongly stimulated the formation of vessel-like structures, which was completely abrogated by co-stimulation with BMP-9. Six bones were stimulated per experimental group and one representative picture of each group is shown.