GSBS Dissertations and Theses

Approval Date

5-15-2007

Document Type

Doctoral Dissertation

Department

Graduate School of Biomedical Sciences

Subjects

Tissue Engineering; Cartilage; Meniere's Disease; Guanidines; Academic Dissertations

Abstract

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.

The 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.

We 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.

We 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.

`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.

In 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.

We 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.

We 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.

Rights and Permissions

Copyright is held by the author, with all rights reserved.

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.