June 11, 2020

Scientists have made one more step toward the treatment and cure of multiple sclerosis (MS) by developing a compound that successfully promotes the regeneration of the protective myelin sheath around nerve cells.

In a recent study, scientists at the Oregon National Primate Research Center (ONPRC) at Oregon Health & Science University (OHSU) described successfully testing the compound in mice, and they have already started to apply it to a rare population of macaque monkeys who develop a disease that is similar to MS in humans.

“I think we’ll know in about a year if this is the exact right drug to try in human clinical trials,” said senior author Larry Sherman, PhD, an OHSU professor in the Division of Neuroscience at the primate center. “If it’s not, we know from the mouse studies that this approach can work. The question is, can this drug be adapted to bigger human brains?” 

The discovery arrives after more than a decade of research following a 2005 breakthrough by Sherman’s lab. In that study, scientists discovered that a molecule called hyaluronic acid (HA), accumulates in the brains of patients with MS. The researchers then linked this accumulation of HA to the failure of cells called oligodendrocytes (which generate myelin) to mature. 

Myelin forms a protective sheath covering each nerve cell’s axon—the threadlike portion of a cell that transmits electrical signals between cells. Damage to myelin is associated with MS, stroke, brain injuries and certain forms of dementia like Alzheimer’s disease. Delay in myelination can also affect infants born prematurely, leading to brain damage or cerebral palsy. 

Other studies led by the Sherman lab have shown that HA is broken down into small fragments in multiple sclerosis lesions by enzymes called hyaluronidases, and these fragments send a signal to immature oligodendrocytes to not turn on their myelin genes. 

There is currently no cure for MS, but an international team of researchers led by OHSU has been working to develop a compound that neutralizes the hyaluronidase in the brains of patients with MS and other neurodegenerative diseases. This will ideally revive the ability of progenitor cells (descendants of stem cells that differentiate, or change, into specific cell types) to mature into myelin-producing oligodendrocytes and regenerate myelin sheath. 

The ONPRC macaque study describes a modified flavonoid—a class of chemicals found in fruits and vegetables—that does just that. The compound, called S3, reverses the effect of HA and promotes functional remyelination in mice. 

“It’s not only showing that the myelin is coming back, but it’s causing the axons to fire at a much higher speed,” Sherman said. “That’s exactly what you want functionally.”

The next phase of research involves testing, and possibly refining, the compound in macaque monkeys who carry a naturally occurring version of MS called Japanese macaque encephalomyelitis. The condition, which causes clinical symptoms similar to multiple sclerosis in people, is the only spontaneously occurring MS-like disease in nonhuman primates in the world. 

Researchers at the ONPRC and other NPRC locations are consistently making breakthrough discoveries to help treat and eradicate MS and other neurological diseases. Learn more about the latest findings here.

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