Abstract
In this study, we investigated the effects of insulin-like growth factor (IGF)-II on the expression and localization of EGR-1 and EGR-2 in cultured human periodontal ligament fibroblasts (PLFs). Three groups of PLF cells were first cultured for two days in serum-free Dulbecco's modified Eagle medium (DMEM), and were then stimulated with various concentrations of IGF-II. Stimulation with IGF-II increased the cell proliferation index in a dose-dependent manner, as measured by 5-bromo 2'-deoxyuridine incorporation. Expression of EGR-1 mRNA peaked after 30 min of incubation with IGF-II at a concentration of 10 ng/mL. Furthermore, dose-dependent expression of EGR-2 mRNA was observed after incubation with IGF-II. These changes correlated well with those seen at the protein level and with the expression of EGRs seen after treatment with 10 ng/mL IGF-II. Immunocytochemical analyses showed strong nuclear immunostaining for EGR-1 in cells treated with 1 ng of IGF-II and for EGR-2 in cells treated with 10 ng of IGF-II. These results suggest that the EGR genes are induced by IGF-II stimulation in human PLFs, and that they have a role in PLF growth during tissue regeneration and healing in vivo.
