Differentiation of skeletal tissues, such as bone, ligament and cartilage, is regulated by complex interaction between genetic and epigenetic factors. In the present study, we attempted to elucidate the possible role of cell-extracellular matrix (ECM) adhesion on the inhibitory regulation in chondrogenesis responding to the tension force. The midpalatal suture cartilages in rats were expanded by orthopedic force. In situ hybridization for type I and II collagens, immunohistochemical analysis for fibronectin, alpha5 and beta1 integrins, paxillin, and vinculin, and cytochemical staining for actin were used to demonstrate the phenotypic change of chondrocytes. Immunohistochemical analysis for phosphorylation and nuclear translocation of extracellular signal-regulated kinase (ERK)-1/2 was performed. The role of the cell-ECM adhesion in the response of the chondroprogenitor cells to mechanical stress and the regulation of gene expression of focal adhesion kinase (FAK) and integrins were analyzed by using an in vitro system. A fibrous suture tissue replaced the midpalatal suture cartilage by the expansive force application for 14 days. The active osteoblasts that line the surface of bone matrix in the newly formed suture tissue strongly expressed the type I collagen gene, whereas they did not express the type II collagen gene. Although the numbers of precartilaginous cells expressing alpha5 and beta1 integrin increased, the immunoreactivity of alpha5 integrin in each cell was maintained at the same level throughout the experimental period. During the early response of midpalatal suture cartilage cells to expansive stimulation, formation of stress fibers, reorganization of focal adhesion contacts immunoreactive to a vinculin-specific antibody, and phosphorylation and nuclear translocation of ERK-1/2 were observed. In vitro experiments were in agreement with the results from the in vivo study, i.e. the inhibited expression of type II collagen and upregulation in integrin expression. The arginine-glycine-aspartic acid-containing peptide completely rescued chondrogenesis from tension-mediated inhibition. Thus, we conclude that stretching activates gene expression of beta1 integrin and FAK and inhibits chondrogenesis through cell-ECM interactions of chondroprogenitor cells.

中文翻译：

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通过细胞-细胞外基质相互作用，拉伸对β1整合素和粘着斑激酶基因表达及软骨形成的影响。

遗传，表观遗传因素之间复杂的相互作用调节骨骼组织的分化，例如骨骼，韧带和软骨。在本研究中，我们试图阐明细胞-细胞外基质（ECM）粘附在软骨张力响应中的抑制调控中的可能作用。大鼠的中pal缝软骨通过骨科力量扩张。I和II型胶原蛋白的原位杂交，纤连蛋白，alpha5和beta1整合素，paxillin和vinculin的免疫组织化学分析，以及肌动蛋白的细胞化学染色被用来证明软骨细胞的表型变化。进行了免疫组织化学分析的细胞外信号调节激酶（ERK）-1/2的磷酸化和核易位。通过使用体外系统分析了细胞ECM粘附在软骨生成细胞对机械应力的反应中的作用以及对粘着斑激酶（FAK）和整联蛋白基因表达的调节。纤维缝合线组织通过施加扩张力持续14天代替了mid中缝合线软骨。在新形成的缝线组织中，排列在骨基质表面上的活性成骨细胞强烈表达I型胶原基因，而它们不表达II型胶原基因。尽管表达α5和β1整合素的软骨前细胞数量增加，但在整个实验期间，每个细胞中α5整合素的免疫反应性均保持在相同水平。在pal中缝线软骨细胞对扩张刺激的早期反应中，应力纤维的形成，粘着斑接触的重组与纽蛋白特异性抗体发生免疫反应，并观察到ERK-1 / 2的磷酸化和核易位。体外实验与体内研究的结果一致，即II型胶原蛋白的抑制表达和整联蛋白表达上调。含精氨酸-甘氨酸-天冬氨酸的肽可完全缓解张力介导的抑制软骨形成。因此，我们得出结论，拉伸可以激活软骨素生成细胞的细胞-ECM相互作用，从而激活β1整合素和FAK的基因表达并抑制软骨形成。体外实验与体内研究的结果一致，即II型胶原蛋白的抑制表达和整联蛋白表达上调。含精氨酸-甘氨酸-天冬氨酸的肽可完全缓解张力介导的抑制软骨形成。因此，我们得出结论，拉伸可以激活软骨素生成细胞的细胞-ECM相互作用，从而激活β1整合素和FAK的基因表达并抑制软骨形成。体外实验与体内研究的结果一致，即II型胶原蛋白的抑制表达和整联蛋白表达上调。含精氨酸-甘氨酸-天冬氨酸的肽可完全缓解张力介导的抑制软骨形成。因此，我们得出结论，拉伸可以激活软骨素生成细胞的细胞-ECM相互作用，从而激活β1整合素和FAK的基因表达并抑制软骨形成。