"Hyaluronan" molecule may inhibit myelin repair.

"Hyaluronan," a mouthful of a molecule, regulates cell movement and growth. But researchers funded in part by the National MS Society have discovered that hyaluronan may pose an obstacle to the body's ability to repair myelin. Myelin insulates nerve fibers and is damaged in MS.

The study, by Larry Sherman, PhD, and colleagues at Oregon Health Sciences University (OHSU), Portland, was published in the September 2005 issue of Nature Medicine.

The discovery--and a collaboration

Dr. Sherman was studying the involvement of the molecule CD44 in nervous system tumors when he discovered that excessive amounts of CD44 led to tremors and myelin damage, similar to those seen in MS. CD44 regulates a cell's response to the hyaluronan molecule.

Dr. Sherman contacted another Society grantee, Dr. Bruce E Bebo, Jr.--a neuroimmunologist at OHSU--to collaborate with him and other researchers on this finding. The newly formed team examined areas of myelin damage in tissue from five people with progressive forms of MS and in mice with an MS-like disease. They found evidence that hyaluronan accumulates in areas of myelin damage, along with CD44. Most tellingly, they found that immature cells did not mature into myelinmaking oligodendrocyte cells in areas where hyaluronan was present.

But the effects were reversible. After treating immature cells isolated in the laboratory with hyaluronan for up to eight days, the investigators withdrew the molecule for an additional 48 hours, and cell maturation resumed.

Dr. Sherman and team reported that this suggests that hyaluronan may prevent myelin repair in people with MS, and that new therapeutic strategies for MS might emerge from studying how to control CD44 and hyaluronan.