THE BEHAVIOR AND PROLIFERATION OF HUMAN DENTAL-PULP CELL STRAINS IN-VITRO, AND THEIR RESPONSE TO THE APPLICATION OF PLATELET-DERIVED GROWTHFACTOR-BB AND INSULIN-LIKE GROWTH-FACTOR-I

Human dental pulp fibroblast strains were established from explants of dental pulps using identical culture techniques. To determine prolife rative activity, a H-3-thymidine uptake and a crystal violet dye-bindi ng assay were performed at passage numbers seven and eight. Assays wer e performed in the presence of either 0% fetal calf serum (FCS), 0.2% FCS or 10% FCS. Considerable variation in the overall proliferative ac tivity of the different pulp cell strains (when averaged over all othe r variables) was noted. All dental pulp cell strains demonstrated sign ificantly different proliferative activity from each other. In additio n, the level of proliferative response and 3H-thymidine incorporation decreased as the passage number of the cells increased. This was in ac cordance with the findings of Tardieu-Moreau et al. (1992). It is prop osed that the differences in proliferative activity are most likely at tributable to inherent variability within the established pulp cell st rains. Platelet derived growth factor-BB (PDGF-BB) and insulin-like gr owth factor-1 (IGF-1) were added to the human pulp cells both separate ly and in combination. All of the pulp cells exhibited increased proli ferative activity in the presence of the growth factors with the combi nation of PDGF-BB/IGF-1 having the greatest mitogenic effect. There wa s also significant variability in the level of response of all pulp ce ll strains to the different growth factors. This study identified sign ificant variability in the responsiveness to the growth factors betwee n the pulp cell strains when the results of the 3H-thymidine and dye b inding assays were compared. These findings reinforce the thesis that different assay procedures may also influence the findings of biologic al investigations involving the human dental pulp. The results of this study confirm that when comparing the findings of different in vitro studies involving human pulp cells, variations in experimental data ca n be strongly influenced by the pulp cell strain used and the culture technique employed. Indeed, studies of human pulp cell proliferation u sing pulp cells which are not of the same transfer number may not be r elevant.