Viscoelastic Properties of Normal and OA Chondrons

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PROJECT SUMMARY / ABSTRACT Osteoarthritis (OA) is a highly prevalent, disabling degenerative disease of the joints that is characterized by progressive deleterious changes in the articular cartilage, subchondral bone, and other joint tissues. This project will exploit emerging evidence from exome sequencing in a unique selection of (early onset) familial OA cases that resulted in the identification of high impact mutations in COL6A3 likely causal to OA. The mechanism by which such a mutation increases the risk for OA is unclear, partly because there is substantial genetic variation among the population and lifestyle differences that can affect the development of OA. We propose to develop a novel in vitro system for studying the functional effect of identified OA causal variants on the biochemical and mechanical properties of articular cartilage using genome editing of COL6A3 in induced pluripotent stem cells (iPSCs) and cartilage tissue engineering. Type VI collagen plays a critical role in the function of the chondron – the chondrocyte and its surrounding pericellular matrix – which has been shown the regulate the biological and biomechanical environment of chondrocytes in articular cartilage. We will use a combined experimental and theoretical modeling approach to determine how changes in the physicochemical properties of the PCM with COL6A3 mutation influence the mechanical interactions between the chondrocyte and ECM in chondrogenically differentiated iPSCs. We will examine the early signaling events as well as the long-term influence of COL6A3 knockout or mutation on chondrocyte response to loading. Finally, we will examine the effect of the COL6A3 knockout or mutation on the epigenetically controlled changes of the transcriptome of chondrocytes in response to loading. A detailed understanding of these mechanisms will provide critical insight into the development of new pharmacologic, regenerative, or physical therapies for OA.