The behaviour and proliferation of human dental pulp cell strains in vitro, and their response to the application of platelet-derived growth factor-BB and insulin-like growth factor-1.

Human dental pulp fibroblast strains were established from explants of dental pulps using identical culture techniques. To determine proliferative activity, a 3H-thymidine uptake and a crystal violet dye-binding assay were performed at passage numbers seven and eight. Assays were performed in the presence of either 0% fetal calf serum (FCS), 0.2% FCS or 10% FCS. Considerable variation in the overall proliferative activity of the different pulp cell strains (when averaged over all other variables) was noted. All dental pulp cell strains demonstrated significantly different proliferative activity from each other. In addition, the level of proliferative response and 3H-thymidine incorporation decreased as the passage number of the cells increased. This was in accordance with the findings of Tardieu-Moreau et al. (1992). It is proposed that the differences in proliferative activity are most likely attributable to inherent variability within the established pulp cell strains. Platelet derived growth factor-BB (PDGF-BB) and insulin-like growth factor-1 (IGF-1) were added to the human pulp cells both separately and in combination. All of the pulp cells exhibited increased proliferative activity in the presence of the growth factors with the combination of PDGF-BB/IGF-1 having the greatest mitogenic effect. There was also significant variability in the level of response of all pulp cell strains to the different growth factors. This study identified significant variability in the responsiveness to the growth factors between the pulp cell strains when the results of the 3H-thymidine and dye binding assays were compared. These findings reinforce the thesis that different assay procedures may also influence the findings of biological 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 can be strongly influenced by the pulp cell strain used and the culture technique employed. Indeed, studies of human pulp cell proliferation using pulp cells which are not of the same transfer number may not be relevant.