[Cellular interplay of bone cells and vascular endothelial cells in bone]

During endochondral bone development, the longitudinal vascular invasion into cartilage primordium initially takes place, by which mineralized cartilage matrix would be exposed into bone. Thereafter, osteogenic cells differentiate into mature osteoblasts to deposit new bone onto the exposed mineralized cartilage. New bone formation at the chondro-osseous junction appears to be achieved by the process of modeling, but not by bone remodeling based on cellular coupling between osteoclasts and osteoblasts. Recently, a specific vessel subtype in bone was reported:Vascular endothelial cells close to the chondro-oseous junction showed intense CD31/Endomucin(CD31(hi)Emcn(hi), type H), while the endothelial cells of sinusoidal vessels in diaphysis revealed only weak CD31/Endomucin(CD31(lo)Emcnlo, type L). It is suggested crucial roles of endothelial HIF in controlling bone angiogenesis, type H vessel abundance, endothelial growth factor expression and osteogenesis.