Participation of endogenous IGF-I and TGF-β1 with enamel matrix derivative-stimulated cell growth in human periodontal ligament cells

Previous studies have provided the biological basis for the therapeutic use of enamel matrix derivative (EMD) at sites of periodontal regeneration. A purpose of this study is to determine effects of EMD on cell growth, ostcoblastic differentiation and insulin-like growth factor-I (IGF-I) and transforming growth factor-beta1 (TGF-beta1) production in human periodontal ligament cells (HPLC). We also examined participation of endogenous IGF-I and TGF-beta1 with EMD-stimulated cell growth in these cells. HPLCs used in this study were treated with EMD alone or in combination with antihuman IGF-I antibody (anti-hIGF-I) or anti-hTGF-beta1, recombinant human bone morphogenetic protein-2 (rhBMP-2), 1,25-dihydroxyvitamin D-3[1,25(OH)(2)D-3], rhTGF-beta1 or rhIGF-I. After each treatment, cell growth, the production of IGF-I and TGF-beta1 and the expression of osteoblastic phenotypes were evaluated. EMD stimulated cell growth in dose-dependent and time-dependent manners. EMD was also stimulated to express IGF-I and TGF-beta1 at protein and mRNA levels. The EMD-stimulated cell growth was partially suppressed by cotreatment with anti-hIGF-I or anti-hTGF-beta1, and cell growth was also stimulated by treatment with rhIGF-I or rhTGF-beta1. rhBMP-2 stimulated alkaline phosphatase (ALPase) activity and ALPase mRNA expression, and 1,25(OH)(2)D-3 stimulated ALPase and osteocalcin mRNA expression. However, EMD showed no effect on the osteoblastic phenotypes expression. These results demonstrated that EMD has no appreciable effect on osteoblastic differentiation, however it stimulates cell growth and IGF-I and TGF-beta1 production in HPLC, and that these endogenous growth factors partially relate to the EMD-stimulated cell growth in HPLC.