COMPARATIVE-ANALYSIS OF TGF-BETA-S, BMPS, IGF1, MSXS, FIBRONECTIN, OSTEONECTIN AND BONE SIALOPROTEIN GENE-EXPRESSION DURING NORMAL AND IN VITRO-INDUCED ODONTOBLAST DIFFERENTIATION

Immobilized TGF beta 1 and BMP2 are able to promote the differentiatio n of odontoblast-like cells in isolated mouse dental papillae cultured in vitro. These cells polarize and accumulate predentin-like matrix a t their apical pole. Immobilized IGF1 mainly promoted polarization wit h disturbed matrix accumulation, in situ hybridization demonstrated th at TGF beta 1 combined with heparin mirrored the physiological process es of odontoblast differentiation. Normal odontoblast and in vitro ind uced odontoblast-like cells expressed transcripts encoding for TGF bet a 1 and 3, BMP2 and 4, bone sialoprotein and osteonectin whereas eithe r ubiquitous expression or no expression could be detected for TGF bet a 2, IGF1 or fibronectin mRNAs. Odontoblast-like cells obtained in the presence of IGF1 combined with heparin did not express TGF beta 1 tra nscripts and expressed weakly TGF beta 3 transcripts. Our results sugg est that in vivo an epithelial-derived member of the TGF beta family t rapped by basement membrane-associated components interacts with compe tent preodontoblasts and promotes the polarization by triggering the t ranscription of growth factor gene(s) like TGF beta itself and/or sele ctor gene(s) like msx2.