Cartilage tissue engineering: uses of injection molding and computer aided design for the fabrication of complex geometries with high dimensional tolerances: a dissertation

Cartilage Tissue Engineering. Joint pain and functional impairment due to cartilage damage from osteoarthritis and other means is a major source of disability for adults the world over. Cartilage is an avascular tissue with a very limited capacity for self repair. Current medical and surgical approaches to cartilage repair also have limited efficacy, and in all cases fail to completely restore a normal, healthy cartilage phenotype. Tissue engineering is a relatively new approach to cartilage repair that seeks to fabricate a replacement tissue, indistinguishable from healthy, native tissue.\nThe basic idea of the tissue engineering approach is to seed tissue synthesizing cells into a shapeable, biocompatible/bioabsorbable scaffold that serves as a temporary extracellular matrix with a localized source of bioactive molecules to direct the development of new tissue. The challenge of tissue engineering is to identify cells, scaffolds, and growth conditions that will be optimal for tissue regeneration. The goal of the current studies was to evaluate one aspect of all three of the major components of cartilage tissue engineering: cell source, scaffolding material and preparation, and controlled growth factor delivery.\nWe evaluated the chondrogenic potential of human nasal chondrocytes grown in calcium alginate in an in vivo culture system, the potential of computer-aided design and injection molding with calcium alginate to reliably reproduce complex geometries with high dimensional tolerances, and the potential for the controlled release of TGF-β1 from calcium alginate modified by the covalent addition of a recently discovered TGF-β binding peptide.\nWe found that adult human nasal chondrocytes show significant chondrogenic potential when grown within an alginate scaffold. We also found that alginate is readily amenable to an injection molding process that utilizes precision made molds from computer-aided design and solid free form fabrication, allowing for the fabrication of tissue engineered constructs with very precise shape fidelity. Additionally, we found that calcium alginate could be reliably modified by the covalent addition of peptides, and that the addition of a newly discovered TGF-β binding peptide delayed the release of pre-loaded TGF-β1. Together these results show some of the encouraging prospects for cartilage tissue engineering.\n`Menière’s Syndrome.Menière’s syndrome is an inner ear disorder characterized by idiopathic endolymphatic hydrops with associated periodic tinnitus, vertigo, and progressive sensorineural hearing loss. It affects approximately 0.2% of the population, for whom it can be quite devastating. In addition to progressive hearing loss people with Menière’s syndrome are prone to sudden attacks of vertigo and tinnitus that are severe enough that they can lead to falls and potentially serious injury. People subject to frequent attacks are unable to drive, with obvious consequences on standard of living.\nIn the current studies we evaluated the standard animal model of Menière’s syndrome by comparing cochlear turn specific hearing thresholds and the degree of hydrops in that turn. A positive correlation between these had previously been established in the study of human temporal bones from people with Menière’s syndrome, but had not been reported in the animal model.\nWe also evaluated the potential of aminoguanidine, a relatively specific inhibitor of the inducible isoform of nitric oxide synthase, as a neuroprotective therapeutic agent for preservation of hearing in animals with surgically induced endolymphatic hydrops.\nWe found, for the first time, a partial correlation between cochlear turn specific hydrops and hearing thresholds in the most commonly used animal model of Menière’s syndrome, helping to validate the utility of this animal model for future studies. We also found that aminoguanidine did indeed partially preserve hearing in animals with surgically induced Menière’s syndrome. This encouraging result appears to be the first report of a medical intervention protective against hearing loss in an animal model of Menière’s syndrome, and may help us to understand the etiology pathology seen in Menière’s syndrome.