[Morphological and histopathological evaluation of temporomandibular joint osteoarthrosis induced by perforation of articular disc in rats].

To establish the animal model of temporomandibular joint osteoarthrosis (TMJOA) in rats induced by perforation of articular disc and evaluate the morphological characteristics and histopathological changes of the condyle of temporomandibular joint (TMJ). Eight male SD rats, purchased from Chongqing Medical University, were marked from No. 1 to No. 8 according to a random number table. The eight numbered rats were then arranged according to their sizes from large to small. The first four rats were divided into the one-week group, while the last four were divided into the four-week group. In order to simulate a TMJ disc perforation, an oblique incision was created along the zygomatic arch of the left side (the model side) making the TMJ superior joint space exposed. The left disc was pulled out and artificially perforated by a dental round bur with 1.5 mm diameter at the postmedian part of TMJ disc. The disc of the right side (the control side) was kept intact. The rats were randomly euthanized respectively at 1 week or 4 weeks (n=4 for each time point) for further study. Morphological observation and imaging examination were used to assess the degree of articular cartilage degradation and the loss of subchondral bone. Immunohistochemicalstaining (IHC), safranin O and fast green staining, tartrate-resistant acid phosphatase (TRAP) staining and haematoxylin staining were performed to evaluate the histopathological changes of condylar cartilage. In the morphological observation, significant redness and swelling were observed on the model side of the 1-week-group and the typical beak-like change of osteoarthropathy was observed on the model side of the 4-week-group. The heights of condylar process on the model sides in the 1-week-group and 4-week-group [(2.73±0.14) and (2.49±0.25) cm, respectively] were significantly lower than that in the control side [(3.30±0.09) and (3.30±0.12) cm, respectively] (<0.01). Imaging examination showed obvious damage in trabecular microstructure on the model side of the 4-week-group. Safranin O and fast green staining showed that the amounts of proteoglycan on the model sides of the 1-week-group and the 4-week-group were significantly lower than that on the control sides (<0.01). TRAP staining showed that the numbers of osteoclasts on the model side of the 1-week-group and the 4-week-group was significantly higher than that on the control sides (<0.01). IHC staining and Haematoxylin staining showed that the mean optical densities of collagen on the model side of the 1-week-group and the 4-week-group was significantly reduced compared with that on the control sides (P<0.01), while the mean optical densities of matrix metalloproteinase increased significantly (<0.01). After making a articular disc perforation, the condylar cartilage on the model side presented typical TMJOA pathological changes.