Study On The Effect Of Endogenous Parathyroid Hormone On Periodontitis-associated Bone Absorption And Mandibular Defect Healing In Mice

Parathyroid hormone is synthetized and secreted by chief cells of the parathyroid glands,as one of the most important endocrine regulators of calcium and phosphorus concentration and metabolism in extracellular fluid. Recent studies have shown that,PTH has a role in both bone formation and bone resorption,suggesting its importance in the process of bone remodeling and restoration. The effects of enhancing bone mass and improving bone quality have been confirmed by many animal experiments and clinical studies,therefore,recombinant human parathyroid hormone (1-34) have been approved to treat the post-menopause female osteoporosis and primarily osteoporosis clinically by the American FDA in 2002. In the current study, standard periodontitis-associated bone absorption and mandibular defects models were built respectively to clarify the effects of endogenous PTH on periodontitis-associated bone absorption and mandibular defect healing in PTH-null mice,and to explore the mechanisms of endogenous PTH modulation on frontal resorption and mandibular remodeling. PartⅠ: Endogenous parathyroid hormone leads to the inhibitory effects on periodontitis-associated bone absorption in miceObjective: To study the effect of parathyroid hormone on periodontitis-associated bone absorption in mice.Methods: In this protocol,20 wild-type mice and 20 parathyroid hormone gene knockout mice were selected to study. The mice were used to induce periodontitis-associated bone absorption by injection of the bacterial endotoxin lipopolysaccharide(LPS) into the maxillary gingiva of the first molar.The differences between the wild-type and parathyroid hormone gene knockout mice were assessed by histomorphology,total collogen staining,tartrate-resistant acid phosphatase staining.Results : The PBL,the N.Oc/B.Pm and Oc.S/B.S were increased significantly,but the BV/TV of the alveolar bone were reduced in parathyroid hormone gene knockout mice compared to those in the wild-type littermates.Conclusion:These studies suggest that endogenous parathyroid hormone has no effect on the development of the alveolar,and has obvious effect on the inhibition of periodontitis-associatied bone absorption in mice. PartⅡ:The effect of Endogenous parathyroid hormone on mandibular defect healing in miceObjective: To study the effect of parathyroid hormone on impacting mandibular defect healing in mice models.Methods: In this protocol,sixty adult mice were divided into two groups-the parathyroid hormone gene knoctout mice group and the wild-type group.Mice standard mandibular defects were built in the left side.Animals were sacrificed at day5,7,10,14,21 after surgery and taken out of the left mandible.The differences between the wild-type and parathyroid hormone gene knockout mice were assessed by X-ray examination and histomorphology.Results : Compared to the wild-type mice, the average gray scales of the wound area were reduced at the same time point, and the formation of the fibrous callus and osteoarthritis callus of the defect area were significantly delayed in parathyroid hormone gene knockout mice.Conclusion:These studies suggest that endogenous parathyroid hormone has obvious promoting effect on the healing of mandibular defect in mice.