Title: Regenerative Engineering of the Temporomandibular Joint in a Porcine Model
Description: Joint disorders significantly affect quality of life and present unique challenges for tissue engineering. In the craniofacial space, and especially for the temporomandibular joint (TMJ), there is an unmet need for anatomically precise and mechanically robust cartilage and bone tissues to recapitulate native function. Current surgical reconstruction methods, whether using autologous or synthetic options, suffer from imprecision, comorbidities, complications, and frequently require subsequent operations. Furthermore, many craniofacial graft efforts have focused on improving bone without addressing cartilage, which is essential to proper TMJ function. Thus, there is a compelling need to engineer a human-sized, biologically and anatomically matched cartilage-bone TMJ replacement. This dissertation demonstrates the ability to generate such a graft with native-like properties in a human-sized large animal model by focusing on two aims: (i) establish methods to fabricate and culture anatomically specific, autologous cartilage-bone grafts (Aim 1), and (ii) show improvement of graft performance after six months implantation in vivo compared to previous methods, controls, and native tissue (Aim 2).

Using Yucatan mini-pigs as a human-sized model, the ramus-condyle unit (RCU), a geometrically intricate portion of the mandible and primary load bearing section of the TMJ, was targeted for reconstruction. Scaffolds were created using computer tomography (CT) image-guided micromilling of decellularized bone matrix, then infused with autologous adipose-derived chondrogenic and osteogenic progenitors. These biological constructs were then cultured in vitro in a novel dual-perfusion bioreactor before in vivo implantation. Similar in vitro culture of representative constructs done in parallel demonstrated cell attachment and some differentiation. After six months implantation, the dual cartilage-bone RCU grafts maintained their predefined anatomical structure and regenerated full-thickness, stratified, and mechanically robust cartilage over the underlying bone, to a significantly greater extent than either bone-only grafts or acellular scaffolds, and showed remarkable similarity to native tissue.

Furthermore, tracking of implanted cells enabled additional insights into the progression of cartilage and bone regeneration. The methods and results established in this dissertation form a promising basis for the next evolution in engineering full-sized, patient-specific, and biologically and mechanically robust TMJ replacements.