Time-Dependent Expression of Bone Sialoprotein Fragments in Osteogenesis Induced by Bone Morphogenetic Protein

Bone sialoprotein is unique to bone and dentin, but its precise role in these tissues is still unknown, although several hypotheses have been presented. We chose ectopic chondro- and osteogenesis induced by bone morphogenetic protein (BMP) as a model system to examine the role of this protein.Partia...

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Published in:Journal of biochemistry (Tokyo) 1996-03, Vol.119 (3), p.475-481
Main Authors: Kobayashi, Daiji, Takita, Hiroko, Mizuno, Morimichi, Toteuka, Yasunori, Kuboki, Yoshlnori
Format: Article
Language:English
Subjects:
Aging - physiology
Alkaline Phosphatase - analysis
Animals
Bone and Bones - cytology
Bone and Bones - enzymology
bone morphogenetic protein
Bone Morphogenetic Proteins
bone remodeling
Bone Remodeling - physiology
bone sialoprotein
Calcium - analysis
Cartilage - cytology
Cartilage - enzymology
Cattle
fragmentation
Gene Expression Regulation
immunolocalization
Immunosorbent Techniques
Integrin-Binding Sialoprotein
Male
Osteocalcin - analysis
Osteogenesis - physiology
Proteins - physiology
Rats
Rats, Wistar
Sialoglycoproteins - biosynthesis
Sialoglycoproteins - genetics
Sialoglycoproteins - physiology
Space life sciences
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Summary:Bone sialoprotein is unique to bone and dentin, but its precise role in these tissues is still unknown, although several hypotheses have been presented. We chose ectopic chondro- and osteogenesis induced by bone morphogenetic protein (BMP) as a model system to examine the role of this protein.Partially purified bovine BMP obtained by a three-step chromato-graphic procedure contained all the active BMPs (natural BMP cocktail). It was combined with insoluble bone matrix and subcutaneously implanted into rats. Expression of bone sialoprotein (BSP) in the implants was followed by using a monoclonal antibody as previously reported. Immunostaining studies showed BSP in the osteoblasts lining the new bone surface at 5 weeks. Western blotting showed 53 and 30 kDa bands, instead of the 57 kDa band normally found in rat femur. These two fragments were metabolically labeled with [3H]proline. The total amount of the fragments rapidly increased after 3 weeks, and at 5 weeks was 3 times as high as that at 2 weeks and still increasing. This time-dependent change was almost parallel to that of osteocalcin. The amount of bone estimated in terms of calcium content increased until 3 weeks and was remained at a plateau thereafter. Alkaline phosphatase activity was prominent only in the first 3 weeks. It was concluded that the 53 and 30 kDa BSP fragments might contribute to maintenance or remodeling in BMP-induced ectopic bone formation.
ISSN:0021-924X
DOI:10.1093/oxfordjournals.jbchem.a021266