DEVELOPMENT OF PORCINE TISSUE ENGINEERED CARTILAGE FOR PRE-CLINICAL STUDIES

Abstract

Damage to the hyaline articular cartilage that cushions joints is exceedingly common worldwide, whether caused by traumatic injuries or degenerative pathologies that can lead to the onset of osteoarthritis. Clinically, cartilage lesions are treated with surgical procedures that attempt to restore the architecture of the hyaline tissue. Unfortunately, the current treatment options often result in the undesired formation of fibrocartilage, a type of cartilage with mechanical properties that are inferior to those of hyaline cartilage. The ability to withstand constant mechanical load is the primary function of articular cartilage, and therefore, critical to restore. The field of cartilage tissue engineering aims to address the limitations of current treatment options by generating restorative tissue with cartilaginous protein composition and concomitant mechanical competency of native hyaline cartilage. Efforts to recapitulate functional cartilage often include approaches that start with cells seeded on a scaffold. Scaffolds are employed to provide the mechanical structure while cells execute the formation of the extracellular matrix. Furthermore, adult mesenchymal stem cells (MSCs) are used in combination with chondrocytes, the single cell type of cartilage, to enhance chondrogenic composition. Given the possible adult MSC sources, such as bone marrow, adipose tissue or the synovial membrane, it is important to select the source that will yield maximum cartilage differentiation. However, the multi-lineage differentiation capacity of MSCs is also their intrinsic limitation. Stem cells undergoing differentiation to cartilage formation can transition into bone, a process known as hypertrophy, which yields changes in chondrocyte function and subsequent undesired deposition of mineralized matrix instead of a normal chondral matrix. The overarching hypothesis of this thesis is that using cartilage-specific MSCs from the synovial membrane, a tissue adjacent to the articular surface, will generate cartilage with superior properties when compared to tissue derived from other cell sources. This hypothesis was tested in the following four aims: First, to assess the in vivo response of tissue engineered cartilage generated from gold standard bone marrow-derived MSCs in a preclinical minipig model; second, to compare the chondrogenic capacity of synovial MSCs and bone marrow MSCs in scaffold-free and scaffold-based engineered cartilage; third, to challenge scaffold-based engineered cartilage with a hypertrophic environment and evaluate the response; and fourth, to explore the use of a hypoxia-simulating agent for the enhancement of chondrogenic differentiation. Together these studies contribute to the identification of an optimal cell source for cartilage tissue engineering to be used in translational preclinical models.