Articular cartilage is critical to the normal function of human diarthrodial joints. Cartilage has unique mechanical and tribological properties that allows for locomotion by providing a nearly frictionless and wear-resistant load bearing joint surface. Osteoarthritis is the most common rheumatic disease and is associated with various degrees of cartilage degradation and altered joint mechanics (i.e. deformation in response to applied loads). Efforts to repair and regenerate cartilage tissue effected by osteoarthritis and other degenerative processes has been the focus of the recently emerging field of tissue engineering, which is the science of design and manufacture of new tissues for the functional restoration of impaired or diseased organs. Basic science studies in tissue engineering aimed at the successful functional restoration of cartilage ultimately depend on inductive signals, responding stem cells, and extracellular matrix scaffolding. The research proposed here will (1) develop a novel noninvasive method to measure heterogeneous three dimensional (3D) deformations throughout the volume of normal and tissue-engineered cartilage constructs and (2) to evaluate the efficacy of defect repairs in bovine articular cartilage explants. Within the past decade, significant advances in magnetic resonance imaging (MRI) techniques, or pulse sequences, have proven highly effective at measuring deformation by tracking the motion of specific tissue regions in 3D space. Further, the initial development of an MRI-based method to determine 3D deformations in cartilage was developed by the applicant to complete his graduate research. This method quantified heterogeneous mechanical deformations throughout the volume of bovine articular cartilage explants using a custom MRI pulse sequence, loading apparatus, and image processing algorithm. In the proposed research, cartilage tissue regions will be tracked as they deform with the use of the MRI pulse sequences DANTE (delays alternating with nutations for tailored excitation) and FS-FSE (fat-suppressed fast spin echo). The deformation measurements will be used to approximate the 3D finite strain tensor field throughout normal and tissue engineered cartilage.
