PROJECT SUMMARY/ABSTRACT The goal of this research project is to develop optical redox imaging (ORI)-based medical instruments to guide surgical and therapeutic approaches in early cartilage damage. Osteoarthritis (OA), for which cartilage pathology is a central aspect, remains a challenging clinical problem without disease-modifying therapeutic strategies. This challenge is exacerbated by the inability of current diagnostic methods to accurately classify cartilage damage early in the OA disease process. Redox imbalance occurs in the OA disease process. Mitochondrial dysfunction is of particular importance, occurring in OA and after traumatic injury. Therapeutic strategies that target mitochondrial dysfunction and metabolic imbalance to treat OA show potential for modifying the disease trajectory. Therefore, measuring cartilage metabolic imbalance has strong potential for early OA diagnosis and for evaluating therapeutic strategies. This research program will use ORI as a diagnostic and evaluative tool for OA. ORI is a label-free, real-time method that captures the autofluorescence of electron donors and an electron acceptor, thereby providing insight into the metabolic balance of a tissue. ORI has been used in the cancer field to identify organoid responses to treatments and distinguish cell subgroups, thus suggesting its utility as a diagnostic and screening tool. Our preliminary data demonstrate that ORI metrics in cartilage are mechanoresponsive, oxygen sensitive, and are correlated with pathology. We will extend our preliminary data to further develop ORI as a tool to diagnose metabolic imbalances associated with pathology and evaluate emerging therapeutic strategies in cartilage. This proposal includes three aims. In Aim 1, we will develop a stress test that can be used to diagnose cartilage disease based on changes in ORI metrics following a mechanical stimulus. In Aim 2, we will develop an ex vivo test platform to rapidly evaluation emergent therapeutic strategies. In Aim 3, we will develop a medical instrument that captures ORI for staging cartilage disease. At the conclusion of this research, we will have developed ORI as an instrument to diagnose cartilage pathology, investigated ORI as a platform to test interventions, and generated a preliminary arthroscopy medical instrument ready for clinical translation.