Osteoblast signaling (Homo sapiens)

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Vitamin D is a regulator of bone metabolism and functions by stimulating the production of bone matrix proteins (for example, collagen, osteopontin, osteocalcin, matrix Gla protein) and activity of alkaline phosphatase activity involved in mineralization. The osteoblasts guarantee the close coupling between bone formation and resorption in healthy bone remodeling, by producing the soluble osteoclast stimulating factor RANK ligand which upon binding to its receptor (RANK) induces differentiation of osteoclast progenitors and fusion of mononuclear cells into multinucleated osteoclasts. Bone sialoprotein is largely specific for mineralized tissues and is highly expressed during the initial formation of bone and cementum. The expression of bone sialoprotein is suppressed by vitamin D treatment in rat calvaria. FGF signaling controls bone formation by regulating the expression of various genes involved in osteoprogenitor cell replication, osteoblast differentiation and apoptosis. Mature osteoclasts control osteoblast chemotaxis via PDGF-BB/PDGFR-B signaling in vitro.