Effects of Enamel Matrix Derivative and Transforming Growth Factor-β1 on Connective Tissue Growth Factor in Human Periodontal Ligament Fibroblasts

Background: Enamel matrix derivative (EMD) is suggested to stimulate transforming growth factor-beta (TGF-beta) production. Connective tissue growth factor (CTGF) is a downstream mediator of TGF-beta. This study explores the effects of EMD and TGF-beta 1 on CTGF in periodontal ligament (PDL) fibroblasts and their interactions in PDL proliferation and development. Methods: Human PDL cells were stimulated with EMD. To explore the effects of EMD and TGF-beta 1 on CTGF expression, cells were treated with and without TGF-beta inhibitor, and CTGF protein levels were assayed by Western blot analysis. To study the role of CTGF in PDL development, cells were treated with CTGF inhibitor. DNA synthesis was analyzed by bromodeoxyuridine enzyme-linked immunosorbent assay. Reverse-transcription polymerase chain reaction was performed to examine messenger RNA expression of PDL osteoblastic differentiation markers: type I collagen, alkaline phosphatase, and osteocalcin. Results: EMD induced a concentration-dependent increase of CTGF protein expression in PDL cells. EMD- and TGF-beta 1-stimulated CTGF expression was significantly reduced in the presence of TGF-beta inhibitor. CTGF inhibition downregulated both EMD- and TGF-beta 1-induced DNA synthesis. The effect of CTGF and EMD on osteoblastic mRNA expression in PDL cells is not obvious. Conclusions: EMD stimulates CTGF expression in human PDL cells, a process modulated by the TGF-beta pathway. CTGF can affect EMD- and TGF-beta 1-induced PDL cell proliferation, but its effects on PDL with regard to osteoblastic differentiation remain inconclusive. The results provide novel insights into EMD-CTGF interaction in PDL cells.