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Effect of IL‐1β‐induced macromolecular depletion on residual quadrupolar interaction in articular cartilage
Author(s) -
Borthakur Arijitt,
Shapiro Erik M.,
Beers Jennifer,
Kudchodkar Sagar,
Kneeland J. Bruce,
Reddy Ravinder
Publication year - 2002
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.10074
Subject(s) - cartilage , nuclear magnetic resonance , chemistry , osteoarthritis , analytical chemistry (journal) , materials science , anatomy , chromatography , physics , pathology , medicine , alternative medicine
Purpose Sodium multiple‐quantum filtered (MQF) NMR spectroscopy may potentially be used to measure proteoglycan (PG) depletion in cartilage caused by osteoarthritis (OA). The purpose of this work was to quantify the effect of interleukin‐1 (IL‐1β)‐induced macromolecule depletion on the residual quadrupolar interaction (RQI) of sodium in bovine cartilage plugs. Materials and Methods Fifteen 8‐mm‐diameter cartilage plug specimens were cored from the articular surface of fresh bovine patellae. All plugs were kept in culture media and nine of the plugs were subjected to interleukin‐1 (IL‐1β)‐induced degeneration of cartilage for 4, 6, and 7 days. Sodium NMR spectra were obtained from each sample with a 1‐cm‐diameter solenoid coil in a 2T whole‐body magnet interfaced to a custom‐built spectrometer. We employed a previously described theoretical model to analyze triple‐quantum filtered (TQF) and double‐quantum filtered magic angle (DQFMA) spectra obtained from normal cartilage and cartilage treated with IL‐1β. The model assumes a static Gaussian distribution of the RQI frequency, ω Q , in the sample. TQF and DQFMA spectra from each sample were fitted with the appropriate signal expressions to determine σ (the root mean square (RMS) ω Q ), T 2f , and T 2s . An inversion‐recovery sequence was used to determine T 1 of each plug. A spectrophotometric assay was used to determine the amount of PG depleted from each plug. Histology was performed to visualize the PG loss in cartilage plugs. We defined σ as the measure of changes in macroscopic order in the tissue. Results Simulated spectra from the theoretical model were in excellent agreement with the experimental data. We were able to determine the relaxation times as well as σ of each specimen from their corresponding fits. T 2f ranged between 2.26–3.50 msec, decreasing with increased PG loss. Over the range of PG depletion investigated, T 2s increased from 12.3 msec to 14.9 msec, and T 1 increased from 16 msec to 21 msec, while σ decreased from 180 Hz to 120 Hz. The order of macromolecules in the cartilage tissue decreased substantially with PG loss. Histology sections clearly showed qualitative visualization of the PG loss in cartilage following treatment with IL‐1β. Conclusion We demonstrated that IL‐β‐induced macromolecule depletion in cartilage not only changes the relaxation characteristics of sodium but also changes RQI of the tissue. Using MQF sodium spectroscopy we quantified the changes in σ and showed that loss of macromolecules reduces the degree of order in the tissue. J. Magn. Reson. Imaging 2002;15:315–323. © 2002 Wiley‐Liss, Inc.