Proteoglycan depletion and magnetic resonance parameters of articular cartilage

Calcium ions and various amounts of proteoglycans were removed from porcine articular cartilage explants using ethylcnediaminetetraacetic acid or guan idinium chloride solutions. The water proton magnetic parameters such as T- 1 and T-2 relaxation times, diffusion (D), and magnetization transfer (M-S/ M-0) were then measured by 1D MR microscopy on native specimens, after incu bation in the extracting solutions and after final reconditioning in a phys iological saline. While the replacement of the interstitial fluid by the tr eating solutions strongly affected the various MR parameters, calcium deple tion did not show any influence on the MRI appearance of the chondral tissu e. Interestingly, only the longitudinal relaxation time T-1 and the diffusi on coefficient D were seen to be sensitive to an extensive proteoglycan dep letion of the tissue. Our results indicate that a modest proteoglycan deple tion, as it occurs in the early stage of a pathological cartilage degradati on, has little relevance to the above MR parameters. Further MRI studies on the macromolecular components of cartilage are, therefore, necessary for a better understanding of the interaction mechanisms between water and extra cellular matrix that might lead to the early diagnosis of the cartilage dam age. (C) 2001 Academic Press.