MRI CONTRAST-ENHANCED STUDY OF CARTILAGE PROTEOGLYCAN DEGRADATION IN THE RABBIT KNEE

Early degeneration of cartilage is accompanied by a loss of proteoglyc ans and consequent changes in the content of water. Conventional magne tic resonance imaging (MRI) cannot reliably detect this change, since the relaxation properties of the cartilage are dominated by its collag en content. The applicability of a positively charged nitroxide as an MRI contrast agent in detection of the content of the negatively charg ed proteoglycans within the cartilage was investigated. The results fr om both MRI and electron paramagnetic resonance (EPR) spectroscopy ind icate that the accumulation of the contrast agent reflects the amount of proteoglycans within the cartilage, presumably due to the electrost atic interactions between the negatively charged proteoglycans and the positively charged nitroxide, Such a contrast agent could be useful i n the detection and study of early stages of the degeneration of joint s.