MITOGENIC EFFECTS OF GROWTH-FACTORS ON HUMAN PERIODONTAL-LIGAMENT CELLS-INVITRO

PERIODONTAL REGENERATION IS THOUGHT to require the migration and proliferation of periodontal ligament cells. Evidence suggests that the polypeptide growth factors PDGF, IL-1, and TGF-beta are mediators of these cellular events in wound healing. The purpose of this study was to determine the effects of these growth factors on human periodontal ligament (PDL) cell mitogenesis, and to identify the regulatory influences of TGF-beta on the response to PDGF and IL-1. Confluent, quiescent human PDL cells were cultured in vitro and treated with the polypeptide growth factors PDGF-AA and -BB, IL-1beta, and TGF-beta in both a dose and time-dependent manner. Mitogenic activity, as a measure of proliferative potential, was determined by the quantitation of H-3-thymidine incorporation during DNA synthesis. The results of this study demonstrated that both PDGF-AA and -BB enhance mitogenic activity in a dose-dependent manner over a concentration range of 1.0 to 50.0 ng/ml. IL-1beta (0.01 to 1.0 pM) resulted in no mitogenic enhancement, and at high concentrations (10.0 to 100.0 pM) demonstrated an inhibitory effect. TGF-beta produced a significant increase (P <0.01) in mitogenic activity (although relatively much less than PDGF) in a delayed, bimodal, dose-dependent manner over a concentration range of 0.01 to 20.0 ng/ml, with a maximal response at a concentration of 1.0 ng/ml. Additionally, incubation with TGF-beta at 1.0 ng/ml prior to the addition of PDGF significantly enhanced (P <0.01) the mitogenic response to both PDGF-AA and PDGF-BB. In contrast, incubation with TGF-beta at a higher concentration (10.0 ng/ml) prior to PDGF addition resulted in a decreased (P <0.05) mitogenic response to PDGF-AA, while enhancing (P <.01) the response to PDGF-BB. This study demonstrates that PDGF-AA and PDGF-BB are major mitogens for human PDL cells in vitro, and supports a role for TGF-beta as a regulator of the mitogenic response to PDGF in these cells.