Changes In Expression Of MMPs And TIMP-1 In Young Rat Condylar Cartilage During Functional Mandibular Advancement

The mandibular condylar cartilage(MCC) is a major growth site of the mandible and an articular cartilage, it plays an important role in determining facial morphology and in orofacial complex functions during active growth period. MCC is secondary fibrocartilage, which is composed of chondrocytes and rich extracellular matrix(ECM). Collagen is the important composition of ECM, and collagen network is the structural base for cartilage to respond to mechanical signals and maintain the chondrocyte phenotype.Functional mandibular advancement is an efficient method to treat Angle class II malocclusion in growing children. Some animal experimental studies have showed that functional mandibular advancement can enhance condylar adaptation and osteogenesis. However, its orthopedic mechanism is not clearly understood. Following mechanical loading, chemical signals control the synthesis of ECM and its degradation. Important to cartilage remodeling is an unique protease family named the matrix metalloproteinases(MMPs), TIMPs are the most effective endogenous inhibitor. Most studies relating to the expression of MMPs and TIMPs in cartilage were conducted at different stages of osteoarthrosis, their expression in condylar cartilage during functional mandibular advancement are nowhere reported.We choose SD rat as experiment model (1) to investigate the features of MCC morphology and collagen network using HE staining and picrosirius staining. (2) to investigate the changes in expression of MMPs and TIMP-1 in young rat condylar cartilage during functional mandibular advancement using immunohistochemistry and in situ hybridization, sixty male 5-week old SD rats are divided into experimental and control groups. The mimic functional appliances are used in experimental group rats. The animals are sacrificed after 1 week, 2 weeks, and 4 weeks. The results show:1. The cartilage located in the posteriosuperior region of the condyle is thickest. MCC can be divided into five layers: articular zone, proliferative zone, transitional zone, mature zone, hypertrophic zone. Type â…  collagen mainly distributes at the articular zone, type â…¡ collagen mainly at mature and hypertrophic zones.2. Following mandibular advancement, the expression of MMP-8 is significantly increased.3. In normal MCC, the immunoreactivity of MMP-2 is rather strong, the one of MMP-9 is very weak. Following mandibular advancement, the expression of MMP-9 is significantly increased, but immunoreactivity of MMP-2 has no changes.4. Following mandibular advancement, the expression of TIMP-1 is also significantly increased, but the peak is later.