Experimental and Computational Studies of Articular Cartilage at High Resolutions

Articular cartilage is a thin layer of connective tissue covering the ends of bones in diarthrodial joints to minimize friction and distribute loads. The degradation of articular cartilage is the hallmark of osteoarthritis (OA), a complex joint disease that ranks as the number one cause of disability in the adult population. Conceptually, cartilage can be divided into three sub-tissue zones (the superficial zone SZ, the transitional zone TZ, and the radial zone RZ) across its thin thickness (depth), where each zone has a set of unique depth-dependent properties. These uneven structural and compositional variations across its thin thickness imply that any diagnostic technique should ideally have high resolution in imaging; otherwise, volume averaging within an image pixel could obscure any possibility of early disease detection.In this dissertation, we used quantitative microscopic magnetic resonance imaging (µMRI) combined with polarized light microscopy (PLM) to study the articular cartilage in rabbits and its potential use as an animal model for OA. The utilization of animals plays a vital role in OA research, which enables the examination of the degradation of OA before any procedures are used on humans in the clinic. This dissertation has six chapters. Chapters 1 and 2 contain the introduction, the background, and the literature review. Chapter 3 is an experimental MRI and PLM study of rabbit cartilage at sub-10 µm resolution, which established quantitatively the baseline characteristics of healthy rabbit cartilage between µMRI and PLM. The results, which are useful for the future investigation of OA using the rabbit model, have been published in the Journal of Orthopaedic Research (Batool & Xia, 2020). Chapter 4 is an experimental study to characterize the structural variations at different anatomical locations of femoral cartilage in young rabbits (12-14 weeks old) using µMRI and PLM. Knowledge of location-specific structural differences in the collagen network over the joint surface can improve the understanding of local mechanobiology and provide insights into tissue engineering, and degradation repairs This study has been published in the journal Cartilage (Batool & Xia, 2022). Chapter 5 presents a computational study that used a mathematical model to describe the role of collagen fibril mechanics in articular cartilage under 1D axial compression. This study is being finalized for a peer-reviewed journal. The final Chapter 6 summarizes this dissertation.