Piezo channel activation and mechanotransduction in chondrocytes during traumatic injury

摘要 近一半的关节损伤在5年内导致症状性创伤后骨关节炎（PTOA） 损伤关节的超生理机械负荷，如运动损伤或事故， 被认为是由驻留在关节软骨内的软骨细胞机械地感知， 分解代谢和炎症基因表达的级联以及蛋白酶和细胞因子的合成， 加速症状性PTOA中存在的软骨降解。尽管对 PTOA中存在的骨关节炎软骨细胞，软骨细胞感知过度的机制， 机械负荷以及将损伤力学与分解代谢基因表达联系起来的途径是未知的。 目前，没有疾病修饰骨关节炎药物（DMOAD）来治疗、预防或延迟骨关节炎。 损伤后软骨退化。最近发现的压电通道（Piezo1和Piezo2）是 哺乳动物中对机械刺激直接反应的第一类离子通道。我们的实验室发现 压电通道选择性地将高细胞变形转化为细胞内信号，这表明了一种新的 超生理负荷可直接启动和增殖分解代谢基因的机制 PTOA的表达。基本问题仍然围绕着压电激活在 软骨细胞对机械负荷的反应，包括：什么样的细胞变形阈值激活了软骨细胞， 压电通道以及在三维环境中如何感知这种变形？分离和 确定软骨细胞力学传导的变形模式将是我们研究的一个重大进展。 理解细胞机械传导和软骨生理学。此外，对 机械激活的压电通道的基因表达是未知的。总的来说，这一建议旨在 建立软骨细胞中压电通道机械激活的基本模式， 压电激活的下游影响。具体来说，在目标1中，我们将确定细胞变形 驱动压电激活的阈值以及如何加载仿生三维水凝胶系统 软骨细胞压电激活。目的2将确定Piezos对机械激活基因的作用 表情总之，完成这些令人兴奋的目标将通过一个协调的实验来实现。 和计算方法。这笔赠款的资助将为我提供一个多学科的经验，以促进 我在组织工程方面的计算和实验训练， 基因调控

ABSTRACT Nearly half of all joint injuries result in symptomatic post-traumatic osteoarthritis (PTOA) within 5 years of injury. Supraphysiologic mechanical loading of the joint, such as that occurring from a sports injury or accident, is believed to be mechanically perceived by the chondrocytes residing within the articular cartilage, initiating a cascade of catabolic and inflammatory gene expression and the synthesis of proteases and cytokines which accelerate the cartilage degradation present in symptomatic PTOA. Despite the extensive characterization of the osteoarthritic chondrocytes present in PTOA, the mechanisms by which chondrocytes perceive excessive mechanical loading, and the pathways linking injury mechanics to catabolic gene expression, are unknown. Currently there are no disease modifying osteoarthritis drugs (DMOADs) to treat, prevent, or delay the degradation of cartilage following injury. The recently discovered Piezo channels (Piezo1 and Piezo2) are the first class of ion channels directly responsive to mechanical stimulation in mammals. Our lab found that the Piezo channels selectively transduce high cellular deformation into intracellular signals, suggesting a novel mechanism through which supraphysiologic loading may directly initiate and propagate the catabolic gene expression of PTOA. Fundamental questions remain surrounding the role of Piezo activation in the chondrocyte’s response to mechanical loading, including: what threshold for cellular deformation activates the Piezo channels and how is this deformation is perceived in a three-dimensional environment? Isolating and identifying the deformation modes of chondrocyte mechanotransduction would be a major advance in our understanding of cellular mechanotransduction and the physiology of cartilage. Additionally, the influence on gene expression of mechanically-activated Piezo channels is unknown. Overall, this proposal seeks to establish the fundamental modes of mechanical activation of Piezo channels in chondrocytes and the downstream implications of Piezo activation. Specifically, in Aim 1 we will identify the cellular deformation thresholds driving Piezo activation and how loading a biomimetic three-dimensional hydrogel system elicits chondrocyte Piezo activation. Aim 2 will then determine the role of Piezos on mechanically-activated gene expression. Together, completing these exciting aims will be accomplished with a coordinated experimental and computational approach. Funding of this grant will provide me a multidisciplinary experience to advance my computational and experimental training in tissue engineering to that of chondrocyte mechanobiology and gene regulation.