Osteoarthritis (OA), or degenerative joint disease, burdens approximately 40 million people in the US and is one of the most disabling conditions in developed nations. Recent studies have shown that surgical interventions such as autologous chondrocyte implantation and osteochondral cylinder transplantation (mosaicplasty) have been successful in reducing the pain caused by OA; however, with autologus chondrocyte implantation the defect ultimately is filled with fibrocartilage rather than the native hyaline articulating cartilage. Furthermore, with mosaicplasty, a number of patients often complain of painful disturbances at the graft site due to the donor site morbidity associated with larger defects (Horas et al 2003, Hangody et al 2003). The potential use of an engineered articular cartilage grown in cell culture to resurface the defect caused by OA is the ideal treatment when compared with filling the defect with a mechanically unfit form of cartilage or causing damage to an otherwise healthy donor site. As better techniques to stratify and orient engineered cartilaginous tissue layers become available it will be valuable to use a high resolution, nondestructive imaging technique to monitor growth and therapeutic effectiveness of the engineered construct. Optical coherence tomography (OCT) has shown potential as a method of high resolution (4-15 μm), non-invasive intraarticular cartilage imaging (Drexler et al 2001, Herrmann et al 1999). OCT is analogous to ultrasound in that it measures the intensity of back-reflected light rather than sound waves. We used OCT to characterize the femoral articulating cartilage of canines obtained post-limb amputation. After OCT imaging, the articulating surfaces were sectioned and stained for a histological evaluation. The OCT images were then compared to their corresponding histology, using non-polarized and polarized light microscopy, in order to evaluate the usefulness and structural clarity of the images. In the OCT images we were able to identify the superficial layer of the articular cartilage, the cartilage-bone interface, and the cartilage thickness. We conclude that OCT does in fact provide enough structural information to monitor growth and therapeutic effectiveness of an engineered cartilage model. In the future we hope to use polarization sensitive OCT to further characterize articular cartilage and identify the middle and deep layers. Once characterization of native cartilage is complete this technique will be implemented on engineered cartilaginous cells and tissue grown in culture to determine whether layer formation occurs.
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