Expression of matrix metalloproteinases-8 and -9 and their tissue inhibitor in the condyles of diabetic rats with mandibular advancement

The present study aimed to evaluate the effects of type 1 diabetes mellitus on the condylar response during treatment with a functional appliance. Sprague-Dawley rats were divided into 3 groups, normal (NG), diabetes (DG) and diabetes with insulin-treatment (TG). Bite-jumping appliances were fitted to the rats in the experimental groups. At 7, 14, 21 and 28 days following fitting, animals were sacrificed and condyles were excised and processed using routine histological techniques. The expression of matrix metalloproteinase (MMP)-8, MMP-9 and tissue inhibitor of metalloproteinase-1 (TIMP-1) was detected using immunohistochemical analysis. Mandibular advancement increased the expression levels of MMP-8 (peaked on day 28), MMP-9 (peaked on day 21), TIMP-1 (peaked on days 21 and 28) and the ratio of MMP-8 to TIMP-1 and MMP-9 to TIMP-1. In the DG, diabetes decreased the expression levels of MMP-8 and MMP-9 induced by mandibular advancement and increased the expression levels of TIMP-1 compared with that of the NG. The ratio of MMP-8 to TIMP-1 and MMP-9 to TIMP-1 also showed a significant decrease in the DG compared with that of the NG. A recovery of these parameters was observed in the TG. Diabetes significantly altered the condylar response, which was triggered by mandibular advancement, and weakened subsequent bone deposition. The results from the TG were not significantly different from that of the NG.