title: The expression of transforming growth factor-beta by cultured chick growth plate chondrocytes: differential regulation by 1,25-dihydroxyvitamin D3.
abstract: 1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) and transforming growth factor-beta (TGF-beta) are both important regulators of chondrocyte growth and differentiation. We report here that 1,25(OH)2D3 differentially regulates the expression of the genes for TGF-beta 1 to -beta 3 and the secretion of the corresponding proteins in cultured chick chondrocytes. Confluent growth plate chondrocytes were serum-deprived and cultured in varying concentrations of 1,25(OH)2D3. Cells were assayed for TGF-beta mRNA and conditioned medium was assayed for TGF-beta activity and isoform composition. Active TGF-beta was only detected in 10(-8) M 1,25(OH)2D3-treated cultures (8.37 ng active TGF-beta/mg protein). There was a significant decrease in total (latent-active) TGF-beta activity in conditioned medium of 10(-12) M (23.4%; P < 0.05) and 10(-10) M (20.7%; P < 0.05) 1,25(OH)2D3-treated cultures but 10(-8) M 1,25(OH)2D3 significantly increased (30.9%; P < 0.01) TGF-beta activity. The amounts of TGF-beta 1, -beta 2 and -beta 3 isoforms produced were similar in control, 10(-10) or 10(-12) M 1,25(OH)2D3-treated cultures but the conditioned medium of 10(-8) M 1,25(OH)2D3-treated cultures contained significantly higher amounts of all three isoforms. Quantification of TGF-beta mRNA demonstrated differential control of TGF-beta gene expression with TGF-beta 1 and -beta 3 mRNA levels reduced by all concentrations of 1,25(OH)2D3 examined (10(-8), 10(-10) and 10(-12) M) whilst TGF-beta 2 mRNA concentrations were elevated. Our results indicated that 1,25(OH)2D3 regulates chick growth plate chondrocyte TGF-beta secretion and mRNA expression in a concentration-dependent and isoform-specific manner. This interaction may be important in the regulation of chondrocyte metabolism and endochondral bone growth.
authors.affiliation: Roslin Institute, Midlothian, UK.
authors.forename: C
authors.initials: C
authors.lastname: Farquharson
authors.forename: A S
authors.initials: AS
authors.lastname: Law
authors.forename: E
authors.initials: E
authors.lastname: Seawright
authors.forename: D W
authors.initials: DW
authors.lastname: Burt
authors.forename: C C
authors.initials: CC
authors.lastname: Whitehead
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002478:Cells, Cultured; D002642:Chick Embryo; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D006132:Growth Plate / Q000166:cytology / Q000378:metabolism*; D007536:Isomerism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D002117:Calcitriol