Cell-Matrix Regulation of Fibrochondrocytes In TMJ OA

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ABSTRACT Cell-matrix regulation of fibrochondrocytes in TMJ OA Disorders of the temporomandibular joint (TMJ) affect between 3-7% of the population and osteoarthritis (OA) is the most common pathology associated with TMJ dysfunction. TMJ OA is a disease of cartilage degeneration and chondrocyte apoptosis. One of the key factors leading to chondrocyte apoptosis is the suppression of the cytoprotective process of autophagy. Autophagy is one of the earliest cellular responses to TMJ OA and has been shown to be a viable therapeutic target for attenuating the progression of cartilage degeneration. A major gap in knowledge is how mechanical and inflammatory stress leads to the eventual suppression of autophagy, apoptosis, and cartilage degeneration. To address this gap, my lab has developed expertise in a preclinical, surgical induction mouse model of TMJ OA that closely corresponds to the human condition and identified a three-step pathogenesis model linking mechanical damage to ECM changes and chondrocyte apoptosis that includes 1) the depletion of Collagen VI (Col VI) following surgically-induced TMJ OA 2) the proteolysis of a Col VI chondrocyte receptor, Neuron/Glial antigen 2 (NG2) and 3) the reduction of autophagy. The overall goal of our study is to test the hypothesis that injury-induced Col VI degeneration activates an NG2-dependent pathway that accelerates TMJ cartilage degeneration by suppressing autophagy. Based on the preliminary data included in this application, we have designed a research plan to mechanistically define how NG2 binding with Col VI is necessary for the maintenance of autophagy and how NG2 monoclonal antibody therapy can attenuate the progression TMJ cartilage degradation by protecting autophagy. The proposed work is innovative because it focuses on a novel molecular mechanism of chondrocyte function that contextually links matrix dysfunction with loss of a cytoprotective cellular mechanism implicated in the progression of TMJ OA. The significance of this research lies in the potential application to the clinical problems of TMJ OA and represents a leap forward in our knowledge of TMJ OA pathophysiology. We anticipate that the outcomes of our study will inform new therapeutic approaches that attenuate the progression of TMJ OA and restore TMJ health in patients that would otherwise require alloplastic total joint replacement.