New techniques that analyze cartilage by layers may one day help scientists predict which patients are most likely to have progressive cases of osteoarthritis (OA), a painful and potentially debilitating disease that occurs when cartilage, which normally cushions the bones, breaks down. Perhaps more importantly, these techniques may aid in the development of new treatments for the disease, say NIAMS-supported scientists, whose research was published in the journal Magnetic Resonance in Medicine.
Hypothesizing that the layers of cartilage surrounding the knee joint become disorganized as osteoarthritis develops and progresses, Sharmila Majumdar, Ph.D., and her colleagues wanted to determine if quantitative analysis of magnetic resonance imaging (MRI) data could show whether these changes are associated with progression of the disease.
Using MRI data from the Osteoarthritis Initiative (OAI), the researchers derived quantitative numbers reflecting the orientation of collagen, the chief component of joint cartilage, in MRI images taken over a two-year period. These numbers were represented as maps that allowed the researchers to see how collagen varies within the cartilage and changes as a result of degeneration.
The researchers used the maps to analyze cartilage as a whole, as well as by layer closest to the bone and layer closest to the joint surface to determine which was most sensitive in predicting change in cartilage breakdown.
Their research acknowledges that OA is not a uniform disease. There is a lot of variability—not just between the estimated 27 million people in the U.S. who have it, but also within a single area of cartilage in an individual. Their suspicion is that nonuniformity of changes—that is, changes in the deep layers compared to the superficial layers, or vice versa—might be more prognostic of OA progression than the change in cartilage as a whole.
Their preliminary results, based on one- and two-year follow-up data from 13 patients, show that quantitative analyses using these strategies can detect subtle changes that indicate disruption of the integrity of the materials that make up cartilage. However, longer term studies with MRIs from larger groups of people—which are already being collected as part of the OAI—are needed to confirm these findings and to determine whether changes in a particular layer are more predictive of severe, progressive disease.
Majumdar suspects future research will show that OA progresses faster in people with changes in a particular cartilage layer—and that finding factors that predispose to these changes will enable doctors to identify them earlier and monitor them noninvasively. Also, because cartilage and bone interact, she believes that understanding the changes in the cartilage layer closest to the bone may lead to the discovery of therapeutic options to treat both cartilage and bone diseases.
The Osteoarthritis Initiative (OAI) is a public-private partnership between the NIH and private industry that seeks to improve diagnosis and monitoring of the progression of OA and foster development of new treatments. Nearly 5,000 people who have knee OA or are at risk of OA are participating in the OAI at four centers in the United States. In addition to X-ray and MRI scans, participants provide biological specimens (blood, urine, and DNA) and clinical data such as dietary intake, medication use, and pain, function, and general health assessments. Participants in the Knee Pain Map study were all participants in the larger OAI.
The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the U.S. Department of Health and Human Services' National Institutes of Health, is to support research into the causes, treatment, and prevention of arthritis and musculoskeletal and skin diseases, the training of basic and clinical scientists to carry out this research, and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at (301) 495-4484 or (877) 22-NIAMS (free call) or visit the NIAMS Web site at http://www.niams.nih.gov.
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Carballido-Gamio J, Blumenkrantz G, Lynch JA, Link TM, Majumdar S. Longitudinal analysis of MRI T(2) knee cartilage laminar organization in a subset of patients from the osteoarthritis initiative. Magn Reson Med. 2010 Feb;63(2):465-72.