Fig. 4. BMP enhances formation of the ectopic joint induced by inhibition of 5ß1 integrin. Forelimbs of E14.5 mouse embryos cultured for 4 days in the presence of 1 µg/ml BMP7 were injected at the wrist with 10 µg of an irrelevant IgG (A,B,C,H,J,L,N) or with 10 µg of an anti-5 integrin mAb (D,E,F,I,K,M,O). (A,D) Complete limb stained with Alcian Blue/Alizarin Red to show skeletal elements. (B,E) Histological sections stained with Safranin O and Fast Green to show cartilage in red. (C,F) In-situ hybridization for Wnt14. (G) Histological sections of limbs injected with 2 µg RGD peptide stained with Safranin O and Fast Green to show cartilage in red. (H,I) TUNEL assay for apoptosis. (J,K) Immunofluorescence staining for type II collagen (green). (L,M) Immunofluorescence staining for type I collagen (green). (N,O) Immunofluorescence staining for Indian hedgehog (green). In all cases cell nuclei are stained with propidium iodide (red).