Osteocalcin is angiogenic in vivo.

The exact function of osteocalcin (OC), a protein synthesized by osteoblasts during the matrix mineralization phase, is still unknown. In this study we investigated the capacity of OC to promote vasoproliferation in chick embryo chorioallantoic membrane (CAM), a well established in vivo assay for angiogenesis and anti-angiogenesis. The results showed that OC stimulates angiogenesis and that the response is similar to that obtained with FGF-2, a well-known angiogenic cytokine. It has previously been demonstrated that OC is involved in bone repair, so the angiogenic activity reported here might also play a crucial role in bone formation.