| Periodontitis is a chronic infection of the supporting structures of teeth resulted from the accumulation of microorganism in dental plaque biofilm. Periodontitis is characterized by the inflammation of the supporting tissue of teeth and the alveolar absorption. Epidemiology studies demonstrated that periodontitis was the most common reason for teeth loss of the old. The role of systemic factors in the initiation and progression of periodontitis has been recognized. Considerable evidence has accumulated that postmenopausal osteoporosis (PMO) is a systemic contributor to periodontitis. The mechanism of the correlation between these two diseases still remains uncertain. In addition, the prevention and therapies of these disorders are the focuses of recent researches.Experiment One: Expression of cytokines in periodontal tissues in ovariectomized rats with experimental periodontitisObjective: To investigate the mechanism of PMO in the initiation and progression of periodontitis. Material and Methods: Twenty-four Sprague-Dawley (SD) female rats were randomly divided into 4 equal groups: Group I: Sham-operated (SHAM); Group II: ovariectomy (OVX); Group III: SHAM+experimental periodontitis (EP); Group IV: OVX+EP. Ten weeks after the surgery, the EPs were induced by placing silk ligatures around the cervix of the left upper second molars in Group III and IV. Two weeks after the ligation, the rats were sacrificed and the body weight, serum biomechanical marker, bone density, absorption of alveolar bone and the numbers of cytokine-positive cells in the periodontal ligament were measured to detect the effects of PMO on periodontal tissues. Results: Ovariectomy resulted in the loss of alveolar bone, upregrulated the expressions of IL-6, OPG, and RANKL and downregurated the expressions of IL-10 in the periodontal tissues of furcation. Conclusion: Ovariectomy resulted in the loss of alveolar bone could be mediated by the changed expressions of cytokines.Experiment Two: Effect of the hIL-10 gene transfered by hydrodynamic tail vein injection on experimental periodontitis in ovariectomized ratsObjective: To investigate the effect of the hIL-10 gene transfered by hydrodynamic tail vein injection on bone metabolism, absorption of alveolar bone, and expressions of cytokines in periodontal tissues in ovariectomized rats. Material and Methods: Ninety-six SD female rats were randomly divided into 4 equal groups: Group I: SHAM+hIL-10; Group II: SHAM+Control vector (VECTOR); Group III: OVX+hIL-10; Group IV: OVX+VECTOR. Twelve weeks after surgery, the rats were transferred with hIL-10 or vector plasmids by hydrodynamic tail vein injection weekly. Seven days after the second, fourth and eighth injection, 8 rats were sacrificed from each group. Two weeks before being sacrificed, the left upper second molars were assigned to receive silk ligatures to induced experimental periodontitis. The body weight, serum biomechanical marker, bone density, absorption of alveolar bone and the numbers of cytokine-positive cells in the furcation were measured to detect the effects of hIL-10 gene therapy on bone metabolism, absorption of alveolar bone and the effect on the expression profile of cytokines in the periodontal tissue. Results: It was demonstrated that the expressed hIL-10 protein in serum after gene transfer downregulated the serum expression levels of TNF-αand TRAP 5b in ovariectomized rats (P<0.05). Although the difference of IL-10 positive cells in the furcation between transfer and vector groups was not significant statistically, the numbers of IL-1βand TNF-αpositive cells in the furcation decreased significantly (P<0.05). Conclusion: Although the numbers of IL-1βand TNF-αpositive cells in the furcation of ovariectomized rats were decreased, hIL-10 gene transferred by hydrodynamic tail vein injection had no significant effect on the absorption of alveolar bone. Experiment Three: Effect of local hIL-10 gene transfer on experimental periodontitis in ovariectomized ratsObjective: To investigate the effect of local hIL-10 gene transfer on bone metabolism, absorption of alveolar bone, and expressions of cytokines in periodontal tissue in ovariectomized rats. Material and Methods: Twenty-four SD female rats were randomly divided into four groups. Group I: SHAM+hIL-10; Group II: SHAM+VECTOR; Group III: OVX+hIL-10; Group IV: OVX+VECTOR. Twelve weeks after SHAM or OVX operation, the experimental periodontitis were induced by placing 4-0 silk ligatures around the cervix of the left upper second molars. At the same time, the complex of 5μg hIL-10 plasmid with 5μl liposome for Group I and III or 5μg vector plasmid with 5μl liposome for Group II and IV were injected into the palatal gingiva of the upper second molars on left sides one time every two days. However, the palatal gingiva of the upper second molars on the right sides were also injected with the same complex as the left for Group I and Group II. Twenty hours after the seventh injection, the rats were sacrificed and the body weight, serum biomechanical marker, bone density, absorption of alveolar bone and the numbers of cytokine-positive cells in the furcation were measured to detect the effects of hIL-10 gene therapy on bone metabolism, absorption of alveolar bone and the expression of cytokines in the periodontal tissue. Results: It was demonstrated that significantly increased hIL-10 exporession was detected in the periodontal tissues after local gene delivery. It was also noted that after hIL-10 gene local delivery, the expression levels of IL-1β, IL-6, TNF-α, RANKL and MMP-8 were significantly downregulated in the furcation of ligatured teeth and the alveolar bone absorption was significantly decreased (P<0.05). Conclusion: The hIL-10 gene transferred by local injection had significant effect on the absorption of alveolar bone and the expression of cytokines including IL-1β, IL-6, TNF-α, RANKL and MMP-8 in periodontal tissues of experimental periodontitis in ovariectomized rats.
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