Abstract Osteoarthritis (OA) is the most prevalent degenerative disease in older adults with the incidence rising rapidly after age 50 and leveling off after age 70. OA is also one of the common causes of chronic pain and the leading cause of physical disability in older adults. Currently, there is an unmet need for therapeutic strategies to improve the outcome for patients with OA. Our latest work identifies a list of microRNAs (miRNAs) in human cartilage and demonstrates a strong association with a robust anabolic effect. This effect is joint-specific and follows a distal-proximal axis gradient (high in ankle and low in hip). Studies show that a joint's identity is maintained by synovial cells and that there is a distinct miRNA profile in different joints. Together, this suggests that the miRNAs we identified in cartilage may originate from synovium and be involved in maintaining joint homeostasis. In Aim 1, I will determine the synovial cell types that express these regenerative miRNAs within human joints and the effects of age on the expression of these miRNAs. In Aim 2, I will determine the signaling pathways responsible for the miRNA-mediated anabolic effects in cartilage and the effects of age on these pathways. I will conduct gene set enrichment analysis to determine miRNA-mediated pathways and then use proteomics to validate these pathways. Through this project, I will determine the miRNA-mediated mechanisms by which synovial cells promote endogenous anabolic effects in the human joint. The key career enhancement of this award will be the training in computational bioinformatics to analyze the complex datasets generated by the project, and further training in aging biology to understand how aging impacts the regeneration process. To facilitate progress toward independence, the training plan will include the coursework/workshops in computational bioinformatics and aging biology, extensive internal and external scientific meetings, and career professional development activities and mentorship. The research and career development plan detailed in this proposal will be conducted with a team of outstanding mentors. Dr. Yi-Ju Li, a professor of Biostatistics & Bioinformatics and an expert in statistics and bioinformatics, will serve as the primary mentor and focus on the training in bioinformatics, statistics, and professional skill development. Drs. Cathleen Colón -Emeric, Virginia Kraus (Duke), and Patrik Önnerfjord (Lund University, Sweden) will serve as co-mentors; they will facilitate training in translational aging research, OA research, and proteomics, respectively. The environment at the Duke University and Duke Molecular Physiology Institute, where the main research activities are located, are ideal for the research and training activities outlined in this proposal. This award will enable me to elucidate the novel contributions of miRNAs to joint tissue homeostasis. Advancements in this area of research have the potential to develop as new therapeutic strategies aimed at improving the quality of life for patients with OA.

Project Narrative We discovered a robust anabolic response in human cartilage that follows a distal-proximal axis gradient (high in the ankle joint and low in the hip joint); this response was modulated by the same master regulators that regulate limb regeneration in animals capable of limb regeneration. This project investigates the origins of these master regulators in synovial cells, the mechanisms involved, and how aging effects these mechanisms in human joint tissue.