Effect of transforming growth factor beta on cell proliferation and glycosaminoglycan synthesis by rabbit growth-plate chondrocytes in culture.
The effects of the transforming growth factor beta (TGF-beta) on the growth and glycosaminoglycan synthesis of rabbit growth plate-chondrocytes in culture were studied. In serum-free medium, TGF-beta caused dose-dependent inhibition of DNA synthesis by chondrocytes, measured as [3H]thymidine incorporation (ED50 = 0.1-0.3 ng/ml). The inhibitory effect was maximal at a dose of 1 ng/ml, and extended for a duration of 16-42 h. In contrast, TGF-beta potentiated the synthesis of DNA stimulated by fetal calf serum (FCS). Addition of TGF-beta (1 ng/ml) to cultures containing 10% FCS increased [3H]thymidine incorporation to 1.6-times that in cultures with 10% FCS alone. Consistent with this finding, TGF-beta potentiated DNA synthesis stimulated by the purified growth factors such as platelet-derived growth factor (PDGF), epidermal growth factor (EGF) and fibroblast growth factor (FGF). The maximal stimulation of DNA synthesis by FGF (0.4 ng/ml) was further potentiated dose dependently by TGF-beta (ED50 = 0.1 ng/ml, maximum at 1 ng/ml). When the cultures were treated with the optimal concentrations of TGF-beta (1 ng/ml) and FGF (0.4 ng/ml), [3H]thymidine incorporation was 3-times higher than that of cultures treated with FGF alone. This TGF-beta-induced potentiation of DNA synthesis was associated with replication of chondrocytes, as shown by a marked increase in the amount of DNA during treatment of sparse cultures of the cells with the growth factors for 5 days. In contrast, TGF-beta caused dose-dependent stimulation of glycosaminoglycan synthesis in confluent cultures of growth-plate chondrocytes (ED50 = 0.3 ng/ml, maximum at 1 ng/ml). This stimulatory effect of TGF-beta was greater than that of insulin-like growth factor I (IGF-I) or PDGF. Furthermore, TGF-beta stimulated glycosaminoglycan synthesis additively with IGF-I or PDGF. Recently, it has been suggested that bone and articular cartilage are rich sources of TGF-beta, whereas epiphyseal growth cartilage is not. Thus, the present data indicate that TGF-beta may be important in bone formation by modulating growth and phenotypic expression of chondrocytes in the growth plate, possibly via a paracrine mechanism.
Hiraki
Y
Y
Department of Biochemistry and Calcified-Tissue Metabolism, Faculty of Dentistry, Osaka University, Japan.
Inoue
H
H
Hirai
R
R
Kato
Y
Y
Suzuki
F
F
D000818:Animals; D002356:Cartilage / Q000166:cytology / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D006025:Glycosaminoglycans / Q000096:biosynthesis*; D006133:Growth Substances / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D011817:Rabbits; D015291:Transforming Growth Factors
D006025:Glycosaminoglycans; D006133:Growth Substances; D010455:Peptides; D015291:Transforming Growth Factors; D004247:DNA