Cytokines and growth factors which regulate bone cell function.
Everybody knows that growth factors are most important in making bone. Hormones enhance bone formation from a long distance. Growth factors promote bone formation as an autocrine or paracrine factor in nearby bone. BMP-2 through BMP-8 are in the TGF-beta family.  BMP makes bone by enchondral ossification.  In bone, IGF-II is most abundant, second, TGF-beta, and third IGF-I.  TGF-beta enhances bone formation mainly by intramembranous ossification in vivo.  TGF-beta affects both cell proliferation and differentiation, however, TGF-beta mainly enhances bone formation by intramembranous ossification.  Interestingly, TGF-beta is increased by estrogen(E2), androgen, vitamin D, TGF-beta and FGF.  IGF-I and IGF-II also enhance bone formation.  At present it remains unclear why IGF-I is more active in bone formation than IGF-II, although IGF-II is more abundant in bone compared to IGF-I.  However, if only type I receptor signal transduction promotes bone formation, the strong activity of IGF-I in bone formation is understandable.  GH, PTH and E2 promotes IGF-I production.  Recent data suggest that hormones containing vitamin D or E2 enhance bone formation through growth factors.  Therefore, growth factors are the key to clarifying the mechanism of bone formation.
Seino
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Department of Pediatrics, Okayama University Medical School, Japan.
D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism / Q000502:physiology*; D001842:Bone and Bones / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D002356:Cartilage / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism* / Q000502:physiology; D018969:Insulin-Like Growth Factor Binding Proteins / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000502:physiology; D007335:Insulin-Like Growth Factor II / Q000502:physiology; D008297:Male; D010011:Osteocytes / Q000378:metabolism* / Q000502:physiology; D010012:Osteogenesis / Q000502:physiology*; D051381:Rats; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000502:physiology; D014807:Vitamin D / Q000502:physiology; D014810:Vitamin E / Q000502:physiology
D019485:Bone Morphogenetic Proteins; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D016212:Transforming Growth Factor beta; D014807:Vitamin D; D014810:Vitamin E; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II