Microfracture-based Repair for Temporomandibular Joint Osteoarthritis - SUMMARY Temporomandibular joint (TMJ) osteoarthritis (OA) is characterized by degeneration of the condylar cartilage. No effective therapies exist for restoring the damaged cartilage to accommodate pediatric patients' craniomaxillofacial growth. Regenerative therapies are needed to repair TMJ cartilage. Microfracture is a technique where perforations are created through the subchondral bone to allow for bone marrow mesenchymal stem cell (MSC) infiltration to create fibrocartilaginous repair tissue. However, MSCs are difficult to localize to the damaged area without a scaffold, and their phenotype is prone to calcification. Matrix-autologous chondrocyte implantation (MACI) is the most effective knee repair approach, where autologous knee chondrocytes are seeded on a collagen scaffold and then implanted in the defect. However, MACI is costly, requires two invasive procedures, and may not be applicable to the narrow TMJ for chondrocyte extraction. Additionally, the collagenous scaffolds that are used for knee repairs do not recapitulate the native TMJ extracellular matrix environment. The objectives of this F32 training grant are to develop regenerative approaches to heal damaged TMJ cartilage for pediatric patients and train me in these approaches to complement my tissue engineering background. Using fibro-elastic cartilage of porcine meniscus, we will use our Meniscal Decellularized (MEND) scaffold to help localize and inform progenitor cells, such as ear cartilage progenitor cells (eCPCs) or MSCs. We hypothesize that regenerative therapy adapting microfracture and MACI/matrix-induced chondrogenesis can be used to repair the damaged TMJ condylar cartilage. We will first compare the in vitro chondrogenic potential and phenotypic stability of eCPCs and MSCs in MEND. Outcomes will include biochemical assays, mechanical testing, immunohistochemistry, histology, and gene expression. Then, to assess in vivo phenotypic stability of the constructs, we will subcutaneously implant cell-seeded MEND in immunocompromised mice and analyze outcomes via biochemical assays, immunohistochemistry, histology, and gene expression. Next, we will compare the repair of adapted microfracture (simulated by an MSC injection) and MACI (simulated by empty or eCPC MEND) for porcine and human TMJ condylar cartilage regeneration in vivo using the semi-orthotopic mouse model and analyze outcomes via biochemical assays, immunohistochemistry, histology, and gene expression. These studies will uncover whether microfracture regenerates TMJ condylar cartilage and if a scaffold, potentially cellular, is needed to improve condylar regeneration. Results will inform development of regenerative therapies for degenerated TMJ condylar cartilage and produce preliminary data for a K99 application to support my training as an independent researcher in the TMJ oral and craniofacial research field.
