SYNOPSIS
The early growth response (EGR) gene family is nuclear transcription factor and is implicated in regulating cell proliferation. In this study, we investigated the effect of insulin-like growth factor (IGF) -I, which relates to oral tissue reconstruction, on the expression and localization of EGR-1 and EGR-2 in cultured human periodontal ligament fibroblasts (PDLFs) using molecular biological and immunocytochemical techniques. Three PDLF cell lines were first cultured for two days in serum-free Dulbecco's modified Eagle medium (DMEM) and further stimulated with various concentrations of IGF-I (1-100 ng/mL in DMEM). Stimulation of the cells with IGF-I increased, in a dose-dependent manner, the proliferation index of the cells as measured by 5-bromo 2'-deoxyuridine incorporation. The mRNA levels of EGR-1 peaked after 45 min of incubation of the cells with IGF-I at a concentration of 10 ng/mL. Further, the expression of EGR-2 mRNA was observed subsequent to incubation with IGF-I at a concentration of 1ng/mL. These changes correlated well with those seen at the protein levels. Immunocytochemical analyses showed strong immunostaining in or around the nucleus for EGR-1 or EGR-2 in IGF-I-treated cells. These results suggest that the EGR genes induced in IGF-I-stimulated human PDLF and may involve a potential important role in PDLF growth during tissue regeneration and healing in vivo.

Key words:Human, Periodontal ligament fibroblasts, Early growth response, Transcription factor, Insulin-like growth factor-I