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

点击翻译按钮获取中文摘要

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.