Effect of collagen and IGF-I on OPN expression in PDL-cells

Objective: The purpose of this study was to determine the effect of type I collagen and Insulin-like growth factor-1 (IGF-I) on osteopontin (OPN) expression, which is one of differentiation marker in human periodontal ligament (HPDL) cells. Methods: HPDL cells were plated on uncoated or type I collagen coated plate before treated with 0, 1, 5, 10ng/ml of IGF-I. The level of OPN expression was analyzed by reverse transcription-polymerase chain reaction and western blot analysis. Result: IGF-I had no effect on OPN expression when HPDL cells were cultured on plastic coated plate whilst it obviously induced OPN expression at 5 and 10ng/ml in the presence of type I collagen. Interestingly, type I collagen showed approximately 5 folds decrease of OPN expression at mRNA level and 2.5 folds decrease at protein level. IGF-I could rescue OPN expression inhibited by type I collagen. Conclusion: This result suggests that type I collagen and IGF-I play a role in modulating OPN expression in human periodontal ligament cells. This basic knowledge will provide a better understanding of the mechanisms that contribute to the periodontal wound healing and regeneration.