Effects of transforming growth factor β on bone nodule formation and expression of bone morphogenetic protein 2, osteocalcin, osteopontin, alkaline phosphatase, and type I collagen mRNA in long-term cultures of fetal rat calvarial osteoblasts

S. E. Harris, Lynda Bonewald, M. A. Harris, M. Sabatini, S. Dallas, J. Q. Feng, N. Ghosh-Choudhury, J. Wozney, G. R. Mundy

Research output: Contribution to journalArticle

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Abstract

Transforming growth factor β (TGF-β) is one of the most abundant of the known growth regulatory factors stored within the bone matrix. When bone is resorbed, TGF-β is released in an active form and is a powerful bone growth stimulant. When injected into the subcutaneous tissue over the calvarial surface of rodents, it rapidly causes proliferation of the periosteal layer and accumulation of new woven bone. In this report, we describe the effects of TGF-β1 on first subcultures of fetal rat osteoblasts obtained from calvarial bones and cultured from confluence with ascorbic acid and β-glycerophosphate. Under these conditions, nodules with characteristics of normal bone appear by day 8. Similar to experiments described by Antosz et al., TGF-β added to confluent cultures inhibited the formation of bone nodules. Both the number and total area of the nodules were quantitated and shown to be completely inhibited by 2 ng/ml of TGF-β1. TGF-β also impaired the expression of genes associated with bone formation, including type I collagen, alkaline phosphatase, osteopontin, and osteocalcin. TGF-β also inhibited the expression of mRNA for the bone morphogenetic protein 2 (BMP-2). These results, showing suppression of markers representative of osteoblast differentiation, suggest that the effects of TGF-β to stimulate bone formation in vivo are not likely a result of effects on differentiated mineralizing osteoblasts but, as suggested by previous studies, more likely are caused by effects on osteoblast precursors. These results also suggest that endogenous BMP-2 expression in fetal rat calvaria cells is important for bone cell differentiation.

Original languageEnglish (US)
Pages (from-to)855-863
Number of pages9
JournalJournal of Bone and Mineral Research
Volume9
Issue number6
StatePublished - Jun 1994
Externally publishedYes

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Bone Morphogenetic Protein 2
Osteopontin
Osteocalcin
Transforming Growth Factors
Collagen Type I
Osteoblasts
Osteogenesis
Alkaline Phosphatase
Messenger RNA
Bone and Bones
Glycerophosphates
Bone Matrix
Bone Development
Subcutaneous Tissue
Skull
Ascorbic Acid
Cell Differentiation
Rodentia
Intercellular Signaling Peptides and Proteins
Gene Expression

ASJC Scopus subject areas

  • Surgery

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Effects of transforming growth factor β on bone nodule formation and expression of bone morphogenetic protein 2, osteocalcin, osteopontin, alkaline phosphatase, and type I collagen mRNA in long-term cultures of fetal rat calvarial osteoblasts. / Harris, S. E.; Bonewald, Lynda; Harris, M. A.; Sabatini, M.; Dallas, S.; Feng, J. Q.; Ghosh-Choudhury, N.; Wozney, J.; Mundy, G. R.

In: Journal of Bone and Mineral Research, Vol. 9, No. 6, 06.1994, p. 855-863.

Research output: Contribution to journalArticle

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abstract = "Transforming growth factor β (TGF-β) is one of the most abundant of the known growth regulatory factors stored within the bone matrix. When bone is resorbed, TGF-β is released in an active form and is a powerful bone growth stimulant. When injected into the subcutaneous tissue over the calvarial surface of rodents, it rapidly causes proliferation of the periosteal layer and accumulation of new woven bone. In this report, we describe the effects of TGF-β1 on first subcultures of fetal rat osteoblasts obtained from calvarial bones and cultured from confluence with ascorbic acid and β-glycerophosphate. Under these conditions, nodules with characteristics of normal bone appear by day 8. Similar to experiments described by Antosz et al., TGF-β added to confluent cultures inhibited the formation of bone nodules. Both the number and total area of the nodules were quantitated and shown to be completely inhibited by 2 ng/ml of TGF-β1. TGF-β also impaired the expression of genes associated with bone formation, including type I collagen, alkaline phosphatase, osteopontin, and osteocalcin. TGF-β also inhibited the expression of mRNA for the bone morphogenetic protein 2 (BMP-2). These results, showing suppression of markers representative of osteoblast differentiation, suggest that the effects of TGF-β to stimulate bone formation in vivo are not likely a result of effects on differentiated mineralizing osteoblasts but, as suggested by previous studies, more likely are caused by effects on osteoblast precursors. These results also suggest that endogenous BMP-2 expression in fetal rat calvaria cells is important for bone cell differentiation.",
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