Regulation of type I collagen synthesis by 1,25-dihydroxyvitamin D3 in human osteosarcoma cells.
Synthesis of type I and III collagens has been examined in MG-63 human osteosarcoma cells after treatment with the steroid hormone, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). Analysis of total [3H]proline-labeled proteins and pepsin-derived collagens revealed that 1,25-(OH)2D3 selectively stimulated synthesis of alpha 1I and alpha 2I components of type I collagen after 6-12 h. Consistent with previous reports (Franceschi, R. T., Linson, C. J., Peter, T. C., and Romano, P. R. (1987) J. Biol. Chem. 262, 4165-4171), parallel increases in fibronectin synthesis were also observed. Hormonal effects were maximal (2- to 2.5-fold versus controls) after 24 h and persisted for at least 48 h. In contrast, synthesis of the alpha 1III component of type III collagen was not appreciably affected by hormone treatment. Of several vitamin D metabolites (1,25-(OH)2D3, 25-dihydroxyvitamin D3, and 24R,25-dihydroxyvitamin D3) tested for activity in stimulating type I collagen synthesis, 1,25-(OH)2D3 was found to be the most active. Analysis of collagen mRNA abundance by Northern blot hybridization indicated that both types I and III procollagen mRNAs were increased 4-fold after a 24-h exposure to 1,25-(OH)2D3. Pro alpha 1I mRNA remained elevated through the 48-h time point while pro alpha 2I and pro alpha 1III mRNAs returned to control values. These results indicate that the regulation of collagen synthesis by 1,25-(OH)2D3 is complex and may involve changes in translational efficiency as well as mRNA abundance. 1,25-(OH)2D3 also caused at least a 20-fold increase in levels of the bone-specific calcium-binding protein, osteocalcin. These results are consistent with the hypothesis that 1,25-(OH)2D3 is stimulating partial differentiation to the osteoblast phenotype in MG-63 cells.
Franceschi
R T
RT
Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts 02115.
Romano
P R
PR
Park
K Y
KY
D015650:24,25-Dihydroxyvitamin D 3; D002117:Calcitriol / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D003094:Collagen / Q000096:biosynthesis*; D004100:Dihydroxycholecalciferols / Q000494:pharmacology; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D015675:Osteocalcin; D012516:Osteosarcoma / Q000378:metabolism*; D010641:Phenotype; D011347:Procollagen / Q000096:biosynthesis; D011392:Proline / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
D002135:Calcium-Binding Proteins; D004100:Dihydroxycholecalciferols; D005353:Fibronectins; D011347:Procollagen; D012333:RNA, Messenger; D015675:Osteocalcin; D015650:24,25-Dihydroxyvitamin D 3; D003094:Collagen; D011392:Proline; D002117:Calcitriol