A study for role of small GTPases in mechanical stress response of chondocytes

软骨是对机械刺激做出反应的主要骨骼元素之一，它不仅支持颞下颌关节的功能，而且还支持身体、气管、耳朵和鼻中隔的关节。所有这些软骨都在骨骼的生长和抵抗体内的机械负荷方面发挥着重要作用。阐明软骨细胞如何分化以及软骨细胞如何产生其特定的大分子并将其降解，对于阐明面部关节疾病的生长和发展机制是极其重要的。特别是，验证调控软骨细胞增殖、分化和代谢的机制和因素对正畸领域的发展至关重要。在我们以前的研究中，我们发现共享应力和/或张应力抑制了胚胎干细胞来源的软骨细胞的分化和次级软骨细胞的成熟，如下颌骨髁突软骨和…。腭中缝合软骨较多。同时，张应力也诱导软骨细胞去分化。相反，压力促进了软骨细胞的分化。本研究从细胞外信号调节激酶(ERK)-1/2的磷酸化和小分子GTP酶Rho的激活两个方面验证了其细胞酪氨酸激酶通路在软骨细胞机械应激反应中的作用。本研究以大鼠胚胎肢芽来源的间充质细胞为实验材料。利用Flexer细胞板的微团培养系统和机械应力加载系统，对ERK-1/2和Rho的激活和基因表达进行定量研究。力负荷后即刻(30min内)，Rho即被激活，60min达高峰，基因表达上调。同时，ERK-1/2在力负荷后60min被磷酸化，而基因表达不受刺激，这种机械刺激抑制了软骨的形成。因此，这些分子在分化软骨细胞的机械应力中起着关键作用。较少

Cartilage is one of the major skeletal elements responding to mechanical stimulations that support not only temporomandibular joint function but also joints in the body, trachea, ear and nasal septurn. All these cartilages play major roles in the growth of skeletons as well as resisting to mechanical loading in the body. It is extremely important to clarify the mechanisms how chondrocytes differentiate and how chondrocytes produce their specific macromolecules and degrade them to clarify the mechanisms of facial growth and development of joint diseases. Especially, verifying the mechanisms and factors that regulates chondrocyte proliferation, differentiation and metabolismis critical for the development of the field of orthodontics. In our previous studies, we discovered that the sharing stress and/or tensile stress inhibited differentiation of chondrocytes derived from embryonic stem cells and maturation of chondrocytes in secondary cartilages such as mandibular condylar cartilages an … More d midpalatal suture cartilages. At the same time, tensile stress induced de-differentiation of chondrocytes as well. Contrary, compressive force enhanced the differentiation of chondrocytes. These revealed that the quantitative and qualitative difference of mechanical stress loaded on chondrocytes induces different responses of chondrogenic mesenchymal cells.In the present study, we verified the role of itnracellular tyrosine kinase pathway in mechanical stress response of chondrocytes focusing on the phospholyration of extracellular signal-regulated kinase (ERK)-1/2 and activation of small GTPase, Rho. Mesenchymal cells derived from embryonic rat limb bud was used for the present study. By using micromass culture system and mechanical stress loading system utilizing Flexcer Cell plate, activation and gene expression of ERK-1/2 and Rho was quatitated. Immediately after force loading (in 30 min), Rho was activated and peaked at 60min with up-regulation of gene expression. At the same time, ERK-1/2 was phospholyrated in 60 min after force loading while gene expression was not stimulated This mechanical stimulation resulted in the inhibition of chondrogenesis. Thus, these molecules play pivotal roles in the mechanical stress of differentiating chondrocytes. Less