Journal of Oral Tissue Engineering

Effect of Insulin-like Growth Factor-I on the Expression of EGR-1 and -2 in Human Periodontal Ligament Fibroblasts

Isao TAMURA1, Aiko KAMADA1, Seiji GODA1, Eisuke DOMAE2, Yasunori SHIMOMURA3, Hiroyuki HAYASHI4 and Takashi IKEO1

1Department of Biochemistry, 2Graduate School of Dentistry (Biochemistry), 3Graduate School of Dentistry (Endodontics), 4Department of Endodontics, Osaka Dental University, Japan

J Oral Tissue Engin 2006;4(1): 1-8

Full Text. DOI

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