Assessment of glycosaminoglycan in progressive trypsin digested cartilage based on contrast-agent enhanced Micro-CT

The early degeneration of articular cartilage (AC) is closely related to the change in glycosaminoglycan (GAG) content. The observation of GAG is therefore an appropriate way for evaluating the degree of AC degeneration and diagnosing osteoarthritis. In this study, the method of contrast-agent enhanced Micro-CT, which has been demonstrated as a potential method for quantitatively analyzing the GAG content, was applied in trypsin digested AC. 102 specimens from fresh bovine femoral condyles were used in this study. 12 specimens were used for exploring the adaptive contrast-agent concentration, incubation time and Micro-CT imaging method. And other 90 were used for GAG degradation experiment. Incubation for 6h with the concentration of 20% contrast-agent Meglumine Diatrizoate (MD) at 37°C was selected as the experiment protocol. Based on this protocol, the relationship between degradation time and the average X-ray attenuation of the samples was obtained, which had a rising tendency within the 50 min degradation (from 1563HU to 1923HU, increased about 23.03%). The average degradation depth of the samples increased with the degradation time (from 0mm (no degradation) to 0.6mm (50 min degradation)). Moreover, the change in the average X-ray attenuation of the samples was linearly and inversely related to their GAG content (r = −0.771, p< 0.01). To conclude, contrast-agent enhanced Micro-CT can provide useful information about trypsin-induced progressive GAG depletion in AC and can reflect variations of GAG content via X-ray attenuation. The results of this study m provide a basis for quantitatively evaluating the cartilage degradation, and also offer a reference to the early diagnosis of osteoarthritis.