Date of Award

Spring 1-1-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical & Biochemical Engineering

First Advisor

Kristi S. Anseth

Second Advisor

Stephanie J. Bryant

Third Advisor

Virginia L. Ferguson

Fourth Advisor

John D. Kisiday

Fifth Advisor

Mark A. Randolph

Abstract

Healing joint articular cartilage is a significant clinical challenge because it lacks self-healing properties. Focal defects that do not heal properly tend to progress to debilitating osteoarthritis that affects millions of people worldwide. Tissue engineering strategies that utilize biofunctional scaffolds as chondrocyte carriers present a promising treatment option to regenerate cartilage tissue. Autologous chondrocytes are a good cell source since they regulate cartilage extracellular matrix (ECM) production in the tissue. Cells can be combined with photopolymerizable scaffolds, which permit control over network formation and can be modified to present biological cues. Current treatment options for cartilage regeneration have generally yielded unsatisfactory long-term results, thus making it necessary to engineer alternate methods that could easily stimulate chondrocyte ECM production and potentially be used to heal joint defects.

In this thesis, we present the development of biofunctional scaffolds that promote cartilage ECM deposition for potential use as cartilage implants. Initial work focused on presenting TGF-Beta1 in a local and persistent manner to encapsulated chondrocytes by tethering the growth factor into the scaffold network. Results revealed that this method of growth factor delivery enhances tissue production over 28 days; however, since the scaffold was non-degradable, the matrix was limited to the pericellular space. Subsequent work focused on the development of an enzymatically-sensitive peptide-linked scaffold that continued to provide a local growth factor signal, but was also cellularly degradable. We found that cell-mediated degradation permitted wide-spread matrix production and increased the bulk mechanical properties of constructs over 14 days. In this particular system, we needed to utilize mesenchymal stem cells (MSCs) to assist the chondrocytes in degrading the scaffold, which motivated the development of a full-length protein-linked scaffold that could locally degrade readily in response to chondrocyte-mediated enzymes. We crosslinked gelatin with a synthetic linker using a photopolymerization reaction and found that this hybrid scaffold promotes increased cellularity of chondrocytes as well as permits wide-spread cartilage ECM via cell-mediated degradation. In summary, this thesis demonstrated that a biofunctional scaffold for cartilage engineering applications should present promotive cues to encapsulated chondrocytes as well as locally degrade in response to cells to facilitate tissue generation.