| Objectives:Mechanical changes and the effect on bone remodeling as research hotspots are concerned by domestic and oversea scholars. With the research development, we have more and more knowledge about mechanotransduction on bone tissues, and several signal transduction pathways, such as mechanical sensitivity of ion channels, protein G signaling pathways, Itegrin-cytoskeletal (Itg-CSK) and so on. In human body, as the secondary cartilage, the physiological alterations of human condylar cartilage are throughout the whole life. Meanwhile, changes of dynamic environment for its remodeling effects could not be ignored. Researchers now mainly focus on a series change of kinase, cytokines or secondary messenger caused by dynamic change. However, the research results are often different, some are even contradict completely. It’s due to the various immune responses for different mechanical stimulus, including the intensity, method, and frequency.Integrin, which is related to cell adhering and bidirectional signaling trasduction, is a group of significant cell adhesion molecules. Further more, it plays a vital role in cell migration, apoptosis, genetic expression and tumor progression. It has been discovered that Itg-CSK pathway is believed to be essential in bone remodeling and also the promoter of mechanical signal transduction in many mechanical signaling pathways. Present studies showed that the amount of integrin β1highly expressed in osteocyte and osteoblast was related to changes of mechanical environment. But reports on condylar cartilage are not only relatively lack, but most of them are cytological experiments. This study aims at investigate the effect of integrin β1in the process of the condylar adaptive remodeling by observing the condylar reconstruction and expression of integrin β1following mandibular forward positioning, so as to provide experiment basis to the regulation mechanism of mandibular condylar cartilage.Methods:After allowed to acclimate for1week,60male Sprague-Dawley (SD) rats were randomly divided into experimental group and control group (n=30). Within each group, the rats were divided into6subgroup (1,3,7,14,21,28). In experimental group, inclined bite plate was cemented (zinc phosphatecement) to the upper central incisors of rat, while the control group wearing nothing. All rats were raised in the same condition with soft food, enough water till the end of the experiment. Five rats were executed by each group after1,3,7,14,21,28days. The specimens of bilateral temporomandibular joins (TMJs) were performed by HE stain and immuno-histochemistry against Integrin β1. The data were dealt with SPSS13.0(α=0.05).Results:At the end of the experiment, anterior teeth of the rats in control group showed the normal overbite and overjet. While in experimental group, they were edge to edge, and no significant deviation was found as well.1Histology observationIn control groups, it showed the normal age-related change in the mandibular condylar cartilage. The thickness of the condylar cartilage was gradually thinning over time. And its remodeling was active in calcified zone. Trabecula bone beneath the cartilage was increased, along with medullary cavity developed well. Nevertheless, the thickness of the cartilage was increased obviously throughout the experimental period (except1st day), especially in median and posterior parts. On the7th day, the layers of chondrocyte were increased significantly, particularly in the germinal layer. On the14th day, it reached to the top, the nucleus also became larger, and it was the same with nucleolus. Meanwhile, the size of mast cell and the intercellular substance was increased. After this, the thickness maintained a steady state gradually. Osteogenesis in experimental groups was notably vigorous, along with a mass of original trabecula bone and underdeveloped medullary cavity were observed in the calcified cartilage zone. 2The expression of integrin (31in condylar cartilageResults showed that integrin β1was mainly expressed at the germinal and hypertrophic zones. At the1st day, the immunohistochemical score (IHS) of integrin β1in experimental group was3.6±0.89, while the same data were in the control group (P>0.05). In the experimental group, however, the expression of integrin β1began to increase3days later (P<0.05). After7days, IHS of the experimental group came to the top at8.4±1.34, which was significantly higher than that of the control group (3.6±0.89)(P<0.01). In addition, it maintained the high level at7.4±1.64on the14th day, while3.6±1.67of the control group. But from then on, the downward trend of integrin β1appeared, and the IHS of experimental group fell to5.2±1.09. But it exceeded the one of the control group as well. At the end of the experiment (28day), IHS of the control group was also (?) than that of the experimental group (2.8±1.09VS4.8±1.09)(P<0.05).Conclusions:1Integrin β1participates the physiogenic reconstruction of the condylar cartilage.2Integrin β1plays a vital role in reconstruction of the condylar cartilage during mandibular forward positioning.3Integrin β1is essential in the mechanobiological signal transduction of the condylar chondrocyte. |
PDF Full Text Request