New imaging technique helps understanding of multiple sclerosis

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041807-cheng-myelinPurdue University researchers have developed an imaging technique that is able to evaluate the molecular mechanisms of multiple sclerosis with hopes of achieving earlier detections and better means to treat the disease.

The imaging method gives researchers a view of how the disease interferes with proper spinal cord functioning. The technique also might yield new information about how the disease degrades the myelin sheath, which insulates nerve fibers and enables them to properly conduct impulses in the spinal cord, brain and in the peripheral nervous system throughout the body, said Ji-Xin Cheng, an assistant professor in Purdue University's Weldon School of Biomedical Engineering and Department of Chemistry.

The three imaging method combined in the technique, sum frequency generation, two-photon-excitation fluorescence and coherent anti-Stokes Raman scattering, are ordinarily used alone. However the researchers have developed a way to combine all three, promising to reveal new details about the spinal cord and myelin sheath, Cheng said.

"Combining these three methods allows us to conduct more specific and precise molecular analyses," he said. "Ultimately, this work paves the way toward studying the degradation of the myelin sheath as a result of multiple sclerosis and analyzing living tissue to study the mechanisms of disease."

"We are using a unique and powerful combination of technologies to uncover the mechanisms of multiple sclerosis," said Riyi Shi, associate professor of basic medical science in Purdue's School of Veterinary Medicine and also an associate professor of biomedical engineering. "We hope to one day establish an effective intervention to not only slow down, but even possibly reverse the development of this disease, which will potentially have profound economic and social impacts on this nation and the world."

The imaging techniques work without using dyes to help see cells and structures and can be applied to living tissues. This is an advantage over conventional microscopic imaging technologies.

For instance, the decades-old imaging technique Raman microscopy cannot be used effectively to study living tissue because of the hours it takes to yield an image. However, coherent anti-Stokes Raman scattering, or CARS, overcomes this limitation, Cheng said.

The researchers have used the imaging methods to observe living spinal tissue extracted from guinea pigs. A special technique of extracting the tissue and then keeping it alive long enough to analyze was developed in Shi's lab.

To broaden application of the imaging process, the researchers hope in the future to design a minimally invasive system for diagnosing patients in the hospital or doctor's office, Cheng said. "There are two directions of this research. One is to study the mechanisms of disease, and that should form the foundation for designing new treatments. The other is to keep pushing the technology to make it less and less invasive, which will help in the early detection of multiple sclerosis."

Findings will be detailed in a paper appearing in May in the Biophysical Journal and is currently online.

Image: The myelin sheath, in red, taken via coherent anti-Stokes Raman scattering, and astroglial filaments, in green, taken with a technique called sum frequency generation. (Source: Weldon School of Biomedical Engineering, Purdue University)