MRI strategy supplies early warning of osteoarthritis

A novel MRI technique that tracks naturally occurring polymers in cartilage can lead to the diagnosis of early-stage osteoarthritis and may lead to better drug treatment and a reduction in the need for joint replacement surgeries.Researchers from the NYU School of Medicine and Tel Aviv University have found that decreased concentrations of glycosaminoglycan (GAG) reliably predict the onset of degenerative joint disease in its earliest stages, before patients become symptomatic. GAG is recognized as a biomarker for both osteoarthritis and degenerative disc disease, which causes lower back pain. "By monitoring GAG, one can intervene much earlier in the disease progression, before gross tissue defects such as ruptures become visible," research scientist Alexej Jerschow, Ph.D., of the NYU School of Medicine, told Diagnostic Imaging. "Used preventively, it can also look at patients over time to see what treatments are effective."Jerschow reported the findings jointly with Ravinder R. Regatte, Ph.D., at the 2008 American Chemical Society meeting Aug. 20. Osteoarthritis results when the cartilage that cushions the bones of the joints begins to break down, causing pain and loss of mobility. GAG contains water that gives cartilage its resilience and elasticity. A low concentration of GAG is known to coincide with the onset of cartilage disorders.Enhanced MRI can be used to detect osteoarthritis, but it does not directly assess GAG levels, Jerschow said. The research team's chemical exchange-dependent saturation transfer method, or gagCEST, separates the protons and hydrogen content in GAG to produce a type of natural contrast agent, making it possible to monitor GAG and assess joint health in a clinical setting.Osteoarthritis afflicts almost 21 million patients in the U.S. - nearly half of them over the age of 65 - and is the leading cause of joint replacement. The disease is usually not diagnosed until it has advanced to the point at which replacement surgery may be the only treatment. Osteoarthritis accounts for about seven million primary physician visits per year and 50% of nonsteroidal anti-inflammatory drug usage. As the population ages, these numbers are expected to climb.Early diagnosis with the gagCEST MR approach could help prevent or reduce permanent joint damage, especially with evidence that dietary supplements like glucosamine and chondroitin can halt further joint degeneration, Jerschow said.The new imaging technique can be implemented on many MR scanners without hardware modifications and does not require significantly more time than a typical MR scan. Testing and diagnosis can be done on the same day."As we gain more insight into osteoarthritis with this and other methods, perhaps a full explanation of the mechanism and prevention of this disease can be found," Jerschow said.

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