Depth-Resolved Detection of Electrokinetic Effects in Cartilage using Differential Phase Sensitive Optical Coherence Tomography

摘要

Osteoarthritis is a heterogeneous disease characterized by progressive loss of cartilage. The earliest biochemical features, which precede gross pathological changes, include non-uniform loss of proteoglycans associated with increase of water content in tissue and finally, fibrillation of the tissue's collagen network. Loss of proteoglycans decreases the ability of cartilage to withstand compressive loading and makes the tissue softer and more susceptible to wear and fibrillation. If the early loss of proteoglycans is detectable by a non-invasive optical technique, progression of the disease may be arrested using, for example, pharmacologic or surgical intervention. When an electric field is applied to cartilage by an electrical stimulator, the current-generated stress gradients are produced and stress deformation occurs. Since differential phase optical coherence tomography is very sensitive to subsurface stress deformation, we propose to stimulate cartilage electrically and detect stress gradients before gross signs of cartilage degeneration appear. Detection of depth-resolved electromechanical stress gradients in cartilage using differential phase optical coherence tomography may be useful to monitor non-invasively cartilage degeneration. Since the streaming potential and other electrokinetic effects in cartilage are directly proportional to proteoglycan density, application of an electric field in cartilage combined with depth-resolved phase sensitive optical measurements may provide a sensitive indicator of cartilage viability on the molecular-level.