Functional tissue engineering of the temporomandibular joint disc
Johns, Deirdre Ellen
Athanasiou, Kyriacos A.
Doctor of Philosophy thesis
Temporomandibular joint (TMJ) disorders arise from disease or trauma and may result in degeneration of the soft tissues. Tissue engineering may provide a solution to disorders of the TMJ without the side effects seen with artificial materials, such as improper incorporation with the surrounding tissues or immunological rejection of the artificial replacement. Several experiments were completed toward the goal of creating a functional TMJ disc replacement using a cell-based approach; the cell types that were primarily examined in this work were TMJ disc cells and costal chondrocytes. Attempts were made to improve the properties of scaffolds seeded with TMJ disc cells, and while proliferation was increased for the monolayer expansion phase of the approach, improvements were not seen in the properties of the three-dimensional constructs by adding L-proline to the culture. Due to the limited success of the TMJ disc cell constructs and the donor scarcity of this cell type, alternative cell sources were investigated in a scaffoldless tissue engineering method to improve the functionality and translatability of the engineered constructs. Chief among the cell types investigated, costal chondrocytes (CCs) consistently produced constructs with considerable amounts of extracellular matrix that were relevant to regenerating TMJ disc fibrocartilage. From this initial success, other aspects in using CCs for TMJ disc tissue engineering were investigated, specifically, passaging the CCs and adding exogenous stimuli. Examining passaged costal and articular chondrocytes showed that while the process of passaging and expanding chondrocytes caused an increase in collagen type I over type II, constructs made from passaged chondrocytes had higher collagen content and tensile properties than primary chondrocyte constructs. The observation that passaged cells were just as, if not more, capable of producing functional constructs also enhanced the translatability of this method by addressing the issue of donor tissue scarcity. Therefore, CCs at a variety of passages were examined in construct culture. Passaged CC constructs consistently produced more glycosaminoglycans per wet weight than primary cell constructs. Passaged CC constructs were then examined in the presence of exogenous stimuli to further improve their properties. At the regimens examined, hydrostatic pressure did not affect the constructs. In contrast, insulin-like growth factor-I improved construct properties over the no growth factor control. Overall, this thesis presents considerable support for the use of passaged costal chondrocytes for the purposes of improving functionality and clinical translatability of constructs for TMJ disc tissue engineering.