The application's long-term objective is to use a comprehensive tissue reconstruction approach to successfully address regeneration of the temporomandibular joint (TMJ) disc. There is a clear need to regenerate the TMJ disc to alleviate the need for discectomy in severe cases of disc displacement. Seventy percent of patients with temporomandibular disorders suffer from disc displacement, which can result in disc degeneration and/or perforation and can be manifested in jaw clicking, locking and severe pain. The chief hypothesis of our study is that we can regenerate a TMJ disc construct comparable to the native disc by the use of a peptide-modified, biodegradable scaffold with the appropriate combination of growth factors, cells and mechanical stimuli with enhanced diffusion. To test this hypothesis, we propose the following specific aims: 1) To characterize the TMJ disc at the tissue level, 2) to describe the TMJ disc at the cellular level and 3) to engineer the TMJ disc in vitro. This comprehensive study will lay the groundwork for future in vivo studies to replace damaged TMJ discs where implants have failed. Furthermore, since the TMJ disc is a poorly understood tissue, collectively the proposed studies will provide broad and detailed knowledge of structure-function properties of the normal TMJ disc. This vital information will allow the definition of design and validation criteria to engineer disc constructs. To characterize the disc at the tissue level, native porcine TMJ discs will be examined to determine ultrastructure, biomechanical properties under tension and compression, and biochemical content and organization. To describe the disc at the cellular level, cellular topography will be elucidated, subpopulations will be identified, and cells will be cultured on two dimensional poly(propylene fumarate-co-ethylene glycol)-GRGD surfaces where proliferation and biosynthesis will be measured with varied growth factors present. Once the native disc is characterized, an engineered disc will be created using the optimal growth factors incorporated within the scaffold in the shape of a native disc, using a combination of a rotating bioreactor, intermittent hydrostatic pressure and direct compression/tension. At various time points, properties of the engineered constructs will be compared to the determined native disc properties. The proposed research represents a novel approach to regenerate the TMJ disc in that we intend to first perform the necessary characterization studies and then use cell-seeded scaffolds, bioactive factors, mechanical signals and enhanced diffusion to facilitate disc regeneration.
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