Effects of dexamethasone, vitamin A and vitamin D3 on DSP-PP mRNA expression in rat tooth organ culture

• Published in: Biochimica et biophysica acta 2004-09, Vol.1679 (3), p.263-271
• Main Authors: Ritchie, H.H., Park, H., Liu, J., Bervoets, T.J.M., Bronckers, A.L.J.J.
• Format: Article
• Language: English
• Subjects: Animals; Blotting, Northern; Cholecalciferol - pharmacology; Collagen Type I - drug effects; Collagen Type I - genetics; Dexamethasone; Dexamethasone - pharmacology; DSP-PP expression; Extracellular Matrix Proteins; Gene Expression Regulation, Developmental - drug effects; Organ Culture Techniques - methods; Osteopontin; Phosphoproteins; Protein Precursors; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - drug effects; Sialoglycoproteins - drug effects; Sialoglycoproteins - genetics; Tooth - drug effects; Tooth - physiology; Tooth Germ - drug effects; Tooth Germ - growth & development; Tooth germs; Tretinoin - pharmacology; Up-Regulation; Vitamin A; Vitamin A - pharmacology; Vitamin D3
• ISSN: 0167-4781; 0006-3002; 1879-2634
• DOI: 10.1016/j.bbaexp.2004.07.004

Vitamin A, 1,25-dihydroxyvitamin D3 and dexamethasone are well-characterized hydrophobic molecules whose biological actions are mediated via different members of the nuclear hormone receptor family. We report here their actions on tooth formation at the molecular level. We have tested the effects of these compounds on osteopontin (OPN), dentin sialoprotein (DSP-PP), and collagen type I expression in pre-mineralization and mineralization stage rat tooth organ cultures which mirror in vivo developmental patterns. These proteins are all believed to participate in the mineralization of dentin. 1,25-Dihydroxyvitamin D3 up-regulated OPN, but had no effect on DSP-PP mRNA expression. Vitamin A up-regulated DSP-PP expression as did dexamethasone. Dexamethasone also up-regulated collagen type I expression. Our results suggest that 1,25-dihydroxyvitamin D3 does not modulate dentin mineralization by directly affecting DSP-PP expression. Vitamin A likely contributes to dentin mineralization by up-regulating DSP-PP expression. Finally, the up-regulation of DSP-PP expression in tooth germ cultures treated with dexamethasone suggests that its application to patient's dental pulp might promote increased extracellular matrix synthesis and mineralization in the pulp and may explain the narrowing of the dental pulp cavity in patients undergoing long-term dexamethasone administration.