Regional Mechanical Properties and Regeneration of the Mandibular Condylar Cartilage

The temporomandibular joint (TMJ) is one of the most complex articulating joints in the body. In addition, the surface of the condyle is mandibular condylar cartilage (MCC), which consists of different populations of cells within each of its layers. Damage or displacement to the disc and other abnormalities of the jaw can lead to eventual degeneration of the MCC. If downstream degeneration of the cartilage continues to progress, the avascular nature of the joint renders the tissue unable to regenerate on its own. \nPrior studies have attempted regeneration of the mandibular condyle with limited success. Regional viscoelastic properties of the MCC are also not well characterized, making the target of regeneration therapies unclear for this tissue. This dissertation aims to elucidate the regional mechanical properties, and providing a tissue engineering alternative through the use of soft biomaterials for the MCC. \nFirst, the regional compressive properties of the porcine TMJ disc and MCC were evaluated through the use of the transversely isotropic biphasic theory. Mechanical and viscoelastic properties of the five different regions of these tissues were evaluated and compared with one another. The results demonstrated higher compressive properties in the posterior region of the disc and also estimated the moduli in different planes, the Poisson’s ratio, and permeability of the MCC. Next, the focus shifted to determining the efficacy of using various soft biomaterials for the mandibular condyle regeneration of an osteochondral defect in the goat model. Acellular polyglycol sebacate and gelatin sponge scaffolds demonstrated cartilage regeneration with presence of collagen II and glycosaminoglycans after 3 months of healing. In hopes of using a cell-laden therapy, in vitro studies with BMSCs and also native cells of the mandibular condyle were conducted. Gelatin hydrogels supported differentiation of BMSCs towards a cartilage lineage, and a gelatin hydrogel composite supported chondrogenesis, and inhibited both mineralization and chondrocyte hypertrophy. Compressive properties of the in vitro scaffolds were also comparable to the measured values of the native MCC. The results of this dissertation give rise to an understanding of the viscoelastic properties of the MCC and give insight on promising soft biomaterials.