Study Of MMP-2 And MMP-3 In Periodontitis Model In Rat Exposed To Hypoxia

BackgroundPeriodontal diseases is the chronic inflammatory disease, which can damage the gum and other periodontal tissues, characterized by the collagenous fibre injury in the extracellular matrix. Periodontal diseases's initiation and progression are related not only with plaque and injury, but also with the environment. It is poor of machines, technique and health protection on the plateau, and the special environment bring out periodontal diseases incidence too. Metabolism of cells within the periodontium is infected in the hypoxia environment, which lead to pathological situation. Hypoxia and toxicant accumulation in periodontium down-regulate the defense and repairation, which is benefit for the growing of anaerobic bacterium. In addition, the environmental impact of salivary secretion by hypoxia dysfunction, leading to poor oral self-cleaning effect, prone to periodontal tissue inflammation. Matrix metalloproteinases ( MMPs ) is a kind of activity enzyme family depending on zinc and calcium, which is similarity in protein structure and homologous with collagenase family. It can degrade many substrates, such as collagen, proteoglycans and other extracellular matrix components, considered as the major invasion of periodontal tissue destruction. Recent studies focused on the changes of MMPs in periodontal diseases in the normal oxygen conditions. Therefore, it is very vital that investing periodontal diseases on the plateau.ObjectiveOur study discuss the effects of hypoxia to MMP– 2 and MMP– 3's secreting in serum, activity and expression in periodontal tissue in the model of rat exposed to hypoxia simulating high attitude, which can lead to find new methods of prevention and cure and study pathogenesy of high altitude periodontal diseases.Materials and methods1. 80 adult SD rats (half male and female, 190~210g each) were randomly divided into four groups (n=20): normal control group (N), normoxia periodontitis group (P1), hypoxia control group (H) and hypoxia periodontitis group (P2). Dental cervix ligation was used with the normoxia periodontitis group and the hypoxia periodontitis group to perform modeling. The normoxia periodontitis group and the normal control group were set in normoxia circumstance. The hypoxia periodontitis group and the hypoxia control group were set in hypobaric chamber simulating 5000– meter high altitude (23h / d). 8 weeks later, each group the destruction of periodontal tissue was compared by histopathology and clinical indexes of periodontitis to certify whether the modeling was successful.2. After established the rat model of periodontitis, the serum levels of MMP– 2 and MMP– 3 were measured by ELISA in each group.3. The modeling succeed SD rats were randomly selected in each group (n=8). The activated MMP– 2 and MMP– 3 in gingival tissue of each group were measured by gelatin zymography and casein zymography, respectively.4. The modeling succeed SD rats were randomly selected in each group (n=8). The expressions of MMP– 2 and MMP– 3 in periodontal tissue of each group were measured by immunohistochemistry.Results1. 8 weeks later, HE results showed that no pathological changes in junctional epithelium, periodontal ligament fibers arranged regularly, cells arranged in order, alveolar ridge was not absorbed and alveolar bone was not damaged in the normal control group and the hypoxia control group. In the normoxia periodontitis group and the hypoxia periodontitis group, junctional epithelium moved to root, salcular epithelium appeared erosion and profliferated to connective tissue.Neutrophils, lymphocytes and other inflammatory cells infiltrated, periodontal ligament space widened, fiber and cell arranged disorderly.Level of GI, PD and ABL were lowest in the normal control group, by turns the hypoxia control group, the normoxia periodontitis group, the hypoxia periodontitis group was highest in four groups. There were significant differences between the normal control group and the normoxia periodontitis group, the hypoxia control group and the hypoxia periodontitis group, the normal control group and the hypoxia control group, the normoxia periodontitis group and the hypoxia periodontitis group (P < 0.05). Level of PLI in the normal control group and hypoxia control group significantly lower than the normoxia periodontitis group and the hypoxia periodontitis group (P < 0.05), no significantly change between the normal control group and the hypoxia control group, the normoxia periodontitis group and the hypoxia periodontitis group (P > 0.05).After established the rat model of periodontitis, the serum levels of MMP– 2 and MMP– 3 were significantly higher in the normoxia periodontitis group and the hypoxia periodontitis group, which were significant differences compared to the normal control group and the hypoxia control group, respectively (P < 0.05). The hypoxia periodontitis group was highest in four groups, the hypoxia control group is higher than the normal control group (P < 0.05).2. The activated MMP– 2 and MMP– 3 in gingival tissue were lowest in the normal control group, by turns the hypoxia control group, the normoxia periodontitis group, the hypoxia periodontitis group. There were significant differences between the normal control group and the normoxia periodontitis group, the hypoxia control group and the hypoxia periodontitis group, the normal control group and the hypoxia control group, the normoxia periodontitis group and the hypoxia periodontitis group (P < 0.05).3. The normal control group almost did not show expressions of MMP– 2 and MMP– 3 in periodontal tissues. The expressions of MMP– 2 and MMP– 3 were similar in the hypoxia control group, gingival epithelium was not obvious but the lamina propria appeared a small amount of expressions. There was significant difference between the normal control group and the hypoxia control group (P < 0.05). MMP– 2 and MMP– 3 were both strongly positive in gingival epithelium and salcular epithelium in the normoxia periodontitis group and the hypoxia periodontitis group (P < 0.05). And inflammatory cells, fibroblasts in periodontal ligament and gingiva, periodontal ligament showed higher expressions of MMP– 2 and MMP– 3 than the normal control group and the hypoxia control group (P < 0.05). The expressions of MMP– 2 and MMP– 3 in the hypoxia periodontitis group were higher than the normoxia periodontitis group (P < 0.05).Conclusions1. The serum levels of MMP– 2 and MMP– 3 can be elevated in rats with periodontitis. In hypoxia simulating high altitude the serum levels of MMP– 2 and MMP– 3 are higher, the destruction of periodontal tissue is promoted futher. The serum level of enzyme, inflammation, attachment loss and alveolar bone absorption change unanimously, which can reflect the changes of periodontitis in hypoxic condition.2. The activity of MMP– 2 and MMP– 3 in gingival tissue are increased by hypoxia simulating high altitude. The activated MMP– 2 and MMP– 3 in gingival tissue are highest in the hypoxia periodontitis group. Excessive activation of MMP– 2 and MMP– 3 may be involved in the development of high altitude periodontal diseases.3. MMP– 2 and MMP– 3 in periodontal tissue may play an important role in development of periodontitis. In hypoxia condition, the strong expressions of MMP– 2 and MMP– 3 in periodontal tissue may be associated with migration of junctional epithelium and periodontal pocket to deepen.