Dysfunctional mechanotransduction in senescent chondrocytes as a link between aging and osteoarthritis

项目总结 慢性疾病骨关节炎是最常见的关节疾病，也是致残的主要原因。 全世界。已知有多种因素会增加发生骨性关节炎的风险，包括肥胖、关节损伤和 遗传易感性，但最重要的风险因素是衰老本身。细胞衰老一直是 被描述为与衰老相关的关键表型，越来越多的证据表明， 关节衰老和损伤反应中的衰老细胞促进了骨性关节炎的发展。 与衰老相关的另一个关键表型是细胞感知变化能力的进行性功能障碍 并将其转化为生化信号，这一过程称为 机械转导。这项提案的总体目标是回答衰老如何驱动关节的问题 通过研究细胞衰老和机械转导功能障碍之间的相互作用， 以及这些因素如何在办公自动化中发挥作用。我们的初步数据显示衰老诱导性增加 老年捐赠者(与年轻捐赠者相比)的反应以及对基质硬度增加的反应。此外， 共同发起人进行的实验表明，衰老的小鼠更容易受到软骨的影响。 与年轻小鼠相比，DMM手术后的降解。因此，这项工作的中心假设是 衰老细胞的堆积导致软骨细胞的增龄性功能障碍 机械转导，衰老的细胞对分解代谢刺激表现出加剧的反应。 为了验证这一假设，我们将利用p16tdTom报告小鼠与lox-top-lox等位基因杂交来 专门标记软骨细胞，使我们的实验室能够定量分析单个- 流式细胞仪检测细胞水平。与其他小鼠模型相比，该模型具有优势，因为它允许 用于鉴定和分离衰老的软骨细胞，可用于后续分析。这个 目标1中提出的实验将评估老化的软骨如何启动软骨细胞的衰老 量化基质硬度增加和DNA损伤增加导致衰老的程度 归纳法。Aim 2将利用p16tdTom报告鼠模型来探索衰老的软骨细胞如何 对他们的机械环境做出不同的反应。最后，目标3将决定如何消除衰老 DMM手术前的软骨细胞减少了老年小鼠的骨性关节炎表型。总的来说，这些数据将定义 细胞衰老在多大程度上是机械转导和软骨功能障碍的中介 退化。这项拟议的工作将对理解衰老细胞如何应对 他们的机械环境，并找出与年龄相关的机械功能障碍的原因 软骨细胞。这些贡献将增加对生物因素的了解，这些因素在 并解释了衰老是如何导致关节功能障碍的。

PROJECT SUMMARY The chronic disease osteoarthritis (OA) is the most common joint disorder and a leading cause of disability worldwide. Multiple factors are known to increase the risk of developing OA, including obesity, joint injury, and genetic predisposition, but the most significant risk factor for OA is aging itself. Cellular senescence has been described as a key phenotype associated with aging, and there is mounting evidence that the accumulation of senescent cells in the joint during both aging and in response to injury contribute to the development of OA. Another key phenotype associated with aging is a progressive dysfunction in the ability of cells to sense changes in their extracellular environment and transduce these into biochemical signals, a process called mechanotransduction. The overall objective of this proposal is to answer the question of how aging drives joint dysfunction by investigating the interplay between cellular senescence and dysfunctional mechanotransduction, and how these play a role in OA. Our preliminary data demonstrates an increased senescence induction response in aged donors (compared to younger donors) and to increasing substrate stiffnesses. Further, experiments conducted by the Co-Sponsor have revealed that aged mice are more susceptible to cartilage degradation after DMM surgery, compared to young mice. Therefore, the central hypothesis of this work is that the accumulation of senescent cells contributes to the age-related dysfunction in chondrocyte mechanotransduction, and that senescent cells display an exacerbated response to catabolic stimuli. To test this hypothesis, we will make use of a p16tdTom reporter mouse crossed with a lox-stop-lox allele to specifically mark chondrocytes, enabling our lab to quantitatively analyze the senescence burden at the single- cell level with flow cytometry. This model is advantageous compared to other murine models because it allows for the identification and separation of senescent chondrocytes that can be used for subsequent analysis. The experiments proposed in Aim 1 will assess how aged cartilage primes chondrocytes for senescence by quantifying the extent to which increased matrix stiffness and mounting DNA damage contribute to senescence induction. Aim 2 will make use of the p16tdTom reporter mouse model to explore how senescent chondrocytes differentially respond to their mechanical environment. Lastly, Aim 3 will determine how eliminating senescent chondrocytes prior to DMM surgery reduces the OA phenotype in aged mice. Collectively, these data will define the extent to which cellular senescence is a mediator of dysfunctional mechanotransduction and cartilage degradation. This proposed work will have broad implications in understanding how senescent cells respond to their mechanical environment and identify a contributing cause of age-related mechanical dysfunction in chondrocytes. These contributions will increase knowledge of the biological factors that play a role in the pathogenesis of OA and provide an explanation for how aging drives joints dysfunction.