Imaging clarifies domains’ role in MS

UC SANTA BARBARA (US) — Nanoscale imaging could lead to early detection, diagnosis, and possible treatments for multiple sclerosis.

Different parts of the central nervous system, including the brain, communicate with each other throughout the body via the transmission of electric impulses, or signals, along fibrous myelin sheaths, that act like electric cables or transmission lines, but are compromised in MS patients.

“Myelin membranes are a class of biological membranes that are only two molecules thick, less than one millionth of a millimeter,” says Jacob Israelachvili, professor of chemical engineering and of materials at University of California, Santa Barbara and a senior author of a new study. “The membranes wrap around the nerve axons to form the myelin sheath.

“Defects in the molecular or structural organization of myelin membranes lead to reduced transmission efficiency,” he says. “This results in various sensory and motor disorders or disabilities, and neurological diseases such as multiple sclerosis.”

Details are published in the journal Proceedings of the National Academy of Sciences.

At the microscopic level and the macroscopic level, which is visible to the eye, MS is characterized by the appearance of lesions or vacuoles in the myelin, and eventually results in the complete disintegration (or demyelination) of the myelin sheath.

The researchers focused on what happens at the molecular level, commonly referred to as the nanoscopic level by using fluorescence imaging and other measurements of domains, which are small heterogeneous clusters of lipid molecules—the main constituents of myelin membranes––that are likely to be responsible for the formation of lesions.

Using model molecular layers in compositions that mimic both healthy and diseased myelin membranes, the researchers observed differences in the appearance, size, and sensitivity to pressure, of domains in the healthy and diseased monolayers.

Next, they developed a theoretical model, in terms of certain molecular properties, that appears to account quantitatively for their observations.

“The discovery and characterization of micron-sized domains that are different in healthy and diseased lipid assemblies have important implications for the way these membranes interact with each other,” says Israelachvili. “And this leads to new understanding of demyelination at the molecular level.”

The myelin sheath (enlarged portion) is compromised in patients with multiple sclerosis and other similar diseases. (Credit: Dottie McLaren)

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