Signal transduction mechanisms of the chondrocyte

关节软骨是一种覆盖在滑膜关节内骨表面的软组织。软骨在关节运动中被压缩和放松，导致渗透应力的变化，因为液体被挤出，然后被富含蛋白多糖的基质吸收。软骨细胞作为软骨中唯一的细胞，在维持细胞外基质方面起着至关重要的作用。软骨细胞对其所在地的力学和化学变化很敏感，并与各种生物反应相互作用。我的研究计划的长期目标是识别和表征软骨细胞对软骨中的机械和化学变化做出生物反应的信号转导机制。这一知识的进步适用于软骨组织工程师在生物反应器系统的设计中。例如，利用渗透应激对软骨细胞生物学的影响是可以低成本扩展的(添加蔗糖或水)。原生纤毛是非运动性的，轴丝由9 0双排列的微管组成。纤毛虽然不活动，但可以通过调节微管的组装、拆卸和鞭毛内的双向运输来改变其长度。软骨细胞纤毛长1-2微米，轴丝上有许多受体和信号分子，包括主要的软骨细胞渗透感受器，瞬时受体电位Vanilloid 4。在渗透胁迫下，软骨细胞纤毛变短，肌动蛋白细胞骨架发生重组，后者需要明胶蛋白的激活。此外，去纤毛的软骨细胞对渗透刺激没有反应，缺乏明胶的细胞显示纤毛生成减少。综上所述，这些数据表明，初级纤毛及其缩短在软骨细胞渗透压力的转导以及与肌动蛋白细胞骨架的相互作用中起着关键作用。我的研究计划的短期目标是研究初级纤毛及其缩短在渗透压力的软骨细胞转导中的作用。我们将研究纤毛缩短是否是软骨细胞渗透转导所必需的，和/或纤毛长度是否调节软骨细胞对渗透压的敏感性。此外，我们将研究肌动蛋白动力学在纤毛长度变化中的作用。最后，我们将操作新软骨构造中的渗透应力和纤毛长度，并测量其对软骨形成的影响。因此，这项建议将为细胞生物学和组织工程领域至关重要的自然科学和工程学提供重要的知识进步。几乎所有的哺乳动物细胞都只有一个初级纤毛，许多细胞都暴露在渗透胁迫下，因此我们的发现将适用于许多细胞系统。

Articular cartilage is a soft tissue covering the surfaces of bones within synovial joints. Cartilage is compressed and relaxed during joint motion leading to changes in osmotic stress as fluid is extruded and then imbibed by the proteoglycan rich matrix. As the only cells of cartilage, chondrocytes play a critical role in maintaining the extracellular matrix. Chondrocytes are sensitive to mechanical and chemical changes in their locale and reciprocate with a variety of biological responses.******The long term objective of my research program is to identify and characterize signal transduction mechanisms through which chondrocytes respond biologically to mechanical and chemical changes in cartilage. This advance in knowledge is applicable for cartilage tissue engineers in the design of bioreactor systems. Harnessing the effects of osmotic stress on chondrocyte biology, for example, is scalable at low cost (adding sucrose or water).******Primary cilia are non-motile with an axoneme consisting of a 9+0 doublet arrangement of tubulin tubules. Although immotile, the cilium can alter its length by regulating microtubule assembly, disassembly and bidirectional intraflagellar transport. Chondrocyte cilia are 1-2 µm long and host numerous receptors and signaling molecules along their axoneme including the primary chondrocyte osmosensor, transient receptor potential vanilloid 4. In response to osmotic stress, chondrocyte cilia shorten and reorganization of the actin cytoskeleton occurs, the latter requiring the activation of gelsolin. Furthermore, deciliated chondrocytes do not respond to osmotic stimuli and cells lacking gelsolin show a reduction in ciliogenesis. Together these data suggest a critical role for primary cilia and their shortening in chondrocyte transduction of osmotic stress and interplay with the actin cytoskeleton in this transduction. ******The short term objective of my research program is to investigate the role of the primary cilium and its shortening in chondrocyte transduction of osmotic stress. We will examine if cilia shortening is necessary for chondrocyte osmotransduction and/or if cilia length regulates chondrocyte sensitivity to osmotic stress. Further we will investigate the role of actin dynamics in changes to cilial length. Finally we will manipulate osmotic stress and cilial length in neo-cartilage constructs and measure the effects on chondrogenesis.******As such this proposal will provide significant advances in knowledge to the natural sciences and engineering that are critical to the fields of cell biology and tissue engineering. Almost all mammalian cells possess a single primary cilium and many are exposed to osmotic stress, thus our findings will be applicable to numerous cell systems.