| Periodontal disease is a common illness initiated from periodontal tissues in populations in different countries of the world. The incidence rate of this disease in adults is as high as approximately 73% in China. Periodontitis is the most common in different kinds of periodontal diseases. Periodontal pocket formation and alveolar bone resorption are considered to be the main clinical symptoms and pathological changes in periodontitis. As to the alveolar bone resorption is the causing regent of teeth loose even loss in periodontitis patients, how to suppress the resorption and biological repair of alveolar bone is a key subject in current study for therapy of periodontitis.It is well known that the osteoblast is the major functional cell in the process of bone formation. A large number of published data indicated that nitric oxide (NO) acts as an important signal molecule participating in cell proliferation and differentiation and mediating the stimulating effects caused by cytokines, mechanical stretch and hormones in bone cells. In addition, NO is involved in bone remodeling in vivo and in vitro. NO at low concentrations may promote bone formation whereas at high concentrations show cytotoxicity inhibiting bone remodeling. It was reported that local NO levels in periodontal lesions were significantly increased, which resulting in the resorption and hindering the remodeling of alveolar bone. Therefore,it will be helpful to improve the therapy of periodontitis through decreasing NO level in periodontal tissue and inhibiting cytotoxicity of NO.Insulin-like growth factors (IGFs), secreted from multiple types of cells, are growth factors belonging to polypeptides. IGFs can be divided into two types: IGF-I and IGF-II. It was recently reported that IGFs possesses multiple complex bioactivities such as promoting the proliferation and differentiation and prolonging the survival of cells. IGF-II can regulate NO levels with cell-specific, that is, the effect on regulating NO levels in different cells is quite distinct and even contrary. For example, IGF-II in rat L6E9 myoblasts increased the expression of inducible nitric oxide synthase (iNOS) which resulting in enhancement of NO levels. Whereas in rat vascular smooth muscle cells and mouse islets, IGF-II inhibited iNOS expression and following decreased NO levels, exhibiting the roles resistant to the cytotoxicity of NO and the prevention of cell apoptosis.So far, no literatures at home and abroad about the effect of IGF-II regulating NO levels and its possible mechanism in osteoblast-like cells have been reported yet. In this study, the effects of IGF-II on the cell proliferation and NO level regulation in mouse osteoblast-like line MC3T3-E1 were demonstrated for providing scientific evidences to apply the cytokine blocking and repairing the resorption of alveolar bone.Objects To determine the actions of cell proliferation, cell survival, NO level regulation, iNOS and eNOS mRNA transcription of IGF-II on mouse osteoblast for primarily understanding the molecular mechanism of cell proliferation-promoted effect of IGF-II.Metheds Mouse calvaria-derived osteoblast line MC3T3-E1 was selected as cell model for examining the activities of IGF-II. After the cells at the different concentrations of IGF-II and different treatment intervals of time, MTT colorimetry was used for demonstrating the effects of cell proliferation and cytoactivity, zymochemistric method was applied for detecting the NO concentrations insupernatants of cell cultures and semi-quantitative RT-PCR was employed for determining the levels of iNOS and eNOS mRNAs.Results1. Dosage and time effects of IGF-II on MC3T3-E1 cell proliferationMTT colorimetry can be used to determine the levels of cell proliferation through detecting the absorbent value at OD490 because there is a well positive linear correlation between the OD490 value and cell numbers.There were no statistically significant differences among the OD490 values of the control group and each of the groups wit... |
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