Detection and analysis of cartilage degeneration by spatially resolved streaming potentials

Cartilage molecular changes in osteoarthritis are most commonly related to the degradation and loss of proteoglycan and collagen fibrils of the extracellular matrix, which directly influence tissue stiffness and compression-generated streaming potentials. In this study, we evaluated the potential of a new technique, spatially resolved mapping of streaming potentials, to non-destructively indicate cartilage health or degeneration. Matched pairs of bovine cartilage/bone explant disks were cultured for 11 days in a serum free medium with and without interleukin-lalpha (IL-1alpha). The electromechanical properties (static stiffness, dynamic stiffness and streaming potentials) of cartilage disks were measured during unconfined compression using a mechanical tester coupled with a linear array of eight 50 microm diameter platinum-iridium microelectrodes. After 11 days of culture, the proteoglycan content of IL-1alpha treated disks was significantly reduced and the denatured and cleaved collagen content was increased compared to control disks. These biochemical alterations were concomitant with the reductions in the amplitudes of the static stiffness, the dynamic stiffness and the streaming potential profile as well as changes in the shape of the streaming potential profile. We found that spatial mapping of streaming potentials presents several advantages for the development of a clinical instrument to evaluate the degeneration of articular cartilage.