Molecular vision! New York University and Tel Aviv University researchers have developed a non-invasive imaging method that can be used to diagnose and monitor a number of diseases, including osteoarthritis and intervertebral disc degeneration (in their early stages). The work is detailed in the latest issue of the journal Proceedings of the National Academy of Sciences (PNAS, February 12, 2008).
The international research team examined glycosaminogycans (GAGs), molecules that serve as the building blocks of cartilage and are involved in numerous functions in the human body. As noted by the researchers, GAG mapping in a living organism is helpful in the diagnosis and monitoring of a number of diseases, as well as in determining the efficacy of drug therapies. Finding limitations in the existing MRI-based techniques for GAG monitoring (they cannot directly map GAG concentrations or they require the administration of contrast agents), the researchers used a more direct measurement of GAGs. They employed the exchangeable protons of GAG to directly measure GAG concentration in vivo.
The NYU/TAU team, working from the premise that GAG molecules have proton groups that are not tethered tightly, investigated whether proton exchange in GAGs could allow concentrations of the molecule to be measured by the MRI. By separating out the GAG protons from those of water, they can be used as a sort of inherent contrast agent. Testing the idea in tissue samples, the researchers found that the available GAG protons did in fact serve as an effective type of contrast enhancement, allowing the researchers to readily monitor GAGs through a clinical MRI scanner. It became clear that this technique can be readily implemented in a clinical setting.
It is hoped that this chemical exchange saturation method could not only provide a non-invasive way to diagnose osteoarthritis in its very early stages, but could also help to indicate early interventions for degenerative disc disease.