Altered Functional Loading Causes Effects On The Expression Of Bone Morphogenic Protein-2 In Condylar Cartilage In Rabbits

ObjectiveTemporomandibular disorders(TMD) occur frequently in dental clinic,Abnormal loading was a faction of TMD. The present study established the animal model of the effect of altered functional loading, To study the effect of experimentally induced altered functional loading on condylar cartilage of temporomandibular joint; immunohistochemical method was used to observe the expression and changes of BMP-2 in condylar cartilage, to discuss the effect of altered functional loading on grows factors of condylar cartilage.MethodsTwenty-four,2-month-old rabbits, were divided into two groups randomly:the experimental group and the control groups. The experimental group was altered functional loading (incisor trimming every three days, to ensure that no pulp exposed) after onset of anesthesia, for 2-8 weeks, keeping observe the occlusion. The control group, only anesthesia, do not do any other treatment, Three rabbits were sacrificed at the end of 2,4,6,8 weeks in each experimental group and control group rabbits. All the rabbits were given normal grain diet. So the altered functional loading animal model was established. Took the bilateral temporomandibular joint condyle of all animals, sections were made after fixation, decalcification and embedment. HE staining to observe the TMJ condyle's histology changes in different times; immunohistochemical method was used to detect the expression of BMP-2 in bilateral condylar cartilage each times.Results1. All animals survived the operation and were able to eat granule fodder normally with the molars, set up the rabbit animal model of altered functional loading.2. Light microscope:Normal rabbit condylar cartilage is divided into the surface layer, proliferative layer, hypertrophic layer and calcified cartilage layer.The layers of cells arranged in order, cartilage matrix and trabecular bone were in a natural extension. Condylar cartilage in the experimental group, The fiber layer could loose, The proliferative layer of cells arranged in irregular and local area occurs fracture, The volume of hypertrophic layer of cells increased and arranged in disorder.3. Immunohistochemistry:BMP-2 expressed mainly in the proliferative layer, hypertrophic layer in the rabbit condylar cartilage, especially hypertrophic layer.The expression of BMP-2 on the left and right side of the rabbit condylar cartilage was no significant difference, (P>0.05), Therefore, the bilateral combined statistics. In control group,The expression of BMP-2 increased from 2nd week to 8th week. Compared with the age- matched control group, the expression of BMP-2 in anterior part of condylar cartilage of the experimental group kept the same level at the end of 2nd,4th,6th and 8th week (P<0.05). Compared with the age-matched control group, the expression of BMP-2 in intermediate part of condylar cartilage of the experimental group increased at the end of 4th,6th and 8th week (P<0.05) Compared with the age-matched control group, the expression of BMP-2 in posterior part of condylar cartilage of the experimental group decreased at the end of 2nd week (P<0.05).But compared with the age- matched control group, the expression of BMP-2 in posterior part of condylar cartilage of the experimental group decreased at the end of 6th and 8th week (P<0.05), kept the same level at the end of 4th week (P>0.05)Conclutions1. Altered functional loading can cause adaptive remodeling of temporomandibular joint condylar cartilage, we can set up an animal model of altered functional loading and provide a theoretical basis for clinical research.2. The BMP-2 take part in the procedure of the remodeling activities of condylar cartilage in altered functional loading rabbits mode.