Baseline expression and effect of TGF-beta 1 on type I and III collagen mRNA and protein synthesis in human odontoblasts and pulp cells in vitro

Since growth factors have been suggested to regulate dentin collagen format ion in response to external irritation, we investigated the effect of TGF-b eta1 on pro alpha 1(I) collagen mRNA expression in cultured mature human od ontoblasts and pulpal fibroblasts. as well as cultured human pulp tissue, u sing quantitative PCR. Cultured gingival fibroblasts (GF) and osteoblasts ( OB) served as controls. Also, type I collagen synthesis in cultured odontob lasts and pulp tissue. as well as type III collagen synthesis in odontoblas ts, were studied by measuring respective procollagen (PINP and PIIINP) secr etion into culture media with radioimmunoassay (RIA). Odontoblasts expresse d significantly higher basic level of type I collagen mRNA than pulp tissue or pulp fibroblasts in culture, but markedly lower level than GF and OB ce lls. TGF-beta1 (10 ng/ml) had negligible effects on type I collagen mRNA ex pression or PINP synthesis in cultured odontoblasts and pulp tissue, and PI IINP synthesis in the odontoblasts. In PF cells. the effect of TGF-beta1 de pended on culturing conditions: a 6-fold increase in mRNA expression was ob served using serum-free medium but no effect was seen in the cells cultured with 10% FBS. In contrast, GF cells serving as controls were not markedly affected by the culture conditions, with 2-3-fold increase in mRNA expressi on by TGF-beta1. These experiments demonstrate that mature human odontoblas ts are capable of synthesizing type III collagen protein, and that TGF-PI h as negligible effect on mature human odontoblast and pulp tissue collagen e xpression.