A team of researchers at New York University and Tel Aviv University has created a non-invasive imaging method that can be used to diagnose and monitor a number of diseases, including osteoarthritis and inter-vertebral disc degeneration, in their initial stages.
The researchers studied glycosaminogycans (GAGs), which are molecules that serve as the building blocks of cartilage and are involved in numerous vital functions in the human body.
Measuring GAG concentration in vivo, or in a living organism, is useful for the diagnosis and monitoring of a number of diseases.
It is also important in determining the effectiveness of drug therapies. For instance, GAG loss in cartilage typically marks the onset of osteoarthritis and inter-vertebral disc degeneration.
However, the current techniques for GAG monitoring, based on traditional magnetic resonance imaging (MRI), have drawbacks: they cannot directly map GAG concentrations or they require the administration of contrast agents.
In the current study, the researchers sought a more direct measurement of GAGs. They employed the exchangeable protons of GAG to directly measure GAG concentration in vivo.
Knowing that GAG molecules have proton groups that are not tethered tightly, the team analysed whether proton exchange in GAGs could allow concentrations of the molecule to be measured by the MRI.
By dividing the GAG protons from those of water, they can be used as a sort of inherent contrast agent.
The researchers tested the idea in tissue samples and found that the available GAG protons provided an effective type of contrast enhancement, allowing them to readily monitor GAGs through a clinical MRI scanner.
The vivo application of this method showed that this technique could be readily implemented in a clinical setting.
The findings therefore showed that this chemical exchange saturation method (gagCEST) not only could 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, which is responsible for lower back pain, and defects in heart valves and, potentially, the cornea.
The study is published in the latest issue of the journal Proceedings of the National Academy of Sciences (PNAS).