The Expression Of Transglutaminase2in Calcium Antagonist Induced Gingival Overgrowth In Rats

BackgroundDrug-induced gingival overgrowth (DGO), which is demonstrated as a fibrotic disease, is a frequent adverse effect associated with the administration of several causative drugs, such as calcium channel blockers including nifedipine (NIF), the anticonvulsant phenytoin, and the immunosuppressant cyclosporine. The pathogenesis has not yet been fully elucidated. Transglutaminase2(TG2), which is a member of the transglutaminases (TGs) family, catalyzes protein cross-linking via transamidation of glutamine residues to lysine residues in a Ca2+-dependent manner. TG2is the only one of the nine TGs that is expressed ubiquitously and abundantly, and is implicated in a variety of cellular processes, such as differentiation, cell death, inflammation, cell migration, and wound healing. Increasing evidences suggest that TG2may be involved in tissue fibrosis that is characterized by excessive accumulation of ECM through crosslinking and stabilizing the ECM. We hypothesize that TG2might play an important role in the pathogenesis of DGO.PurposeWe use the model of DGO induced by NIF in rats to observe the expression of TG2and its TGase activity.MethodsNineteen male Wistar rats were divided into two groups (nine rats/group). The rats in the test group received NIF treatment via gastric gavage for45days procedure, and the dosage of NIF from day1-15, day16-45was125,250mg.kg-1respectively. In the control group, the rats received gastric gavage of same volume of distilled water until the end of experiment. At the beginning and end of the experiment, all the animals were extracted blood from the jugular vein to measure the calcium, phosphorus concentration, levels of alanine aminotransferase (ALT) and aspartame aminotransferase (AST) in serum. All the animals were injected5-Bromo-2’-deoxyuridine (Brdu)100mg.kg-1intraperitonealy2hours after execution.Gingival tissues were incised for histological observation. HE, Masson staining were used to observe and analyze the hyperplasia degree of gingival tissue. Immunohistochemistry of TG2and Brdu was used to detect the expression of TG2in the gingival tissue and the proliferation rate of gingival epithelial cells. Unfixed cryostat sections were prepared to detect TGase of TG2by immunofluorescence.ResultsAfter45days experiment, the concentration of calcium in both group increased. However, the increase in the test group was significantly higher than that of the control group (0.375±0.0122mmol/L vs0.1825±0.0203mmol/L)(p<0.05). In contrast to the calcium increase in both groups, the concentration of phosphate decreased in both groups. And the decrease in the test group was significantly larger than that in the control group (-0.831±0.0387mmol/L vs-0.243±0.0420mmol/L, p <0.05). The results of histological analysis showed that the thickness of epithelia and connective tissue were increased significantly than the control group (p<0.05) Immunohistochemistry and immunofluorescence demonstrated that TG2expression and TGase activity in gingival tissue of test group were significantly elevated when compared to the control group, and TGase activity was consistent with the TG2distribution. Brdu immunohistochemistry showed there was significantly more proliferating cells in the basal layer in the test group than that in the control group.ConclusionsThe results indicate that we successfully establish a DGO model through the NIF administration and TG2may play an important role in the process of DGO.