MS study offers theory for why repair of brain's wi...( Scientists have uncovered new eviden...)

Scientists have uncovered new evidence suggesting that damage to nerve cells in people with multiple sclerosis accumulates because the body's natural mechanism for repair of the nerve coating called "myelin" stalls out.

The study, published today, July 1, 2009, in the print edition of "Genes & Development," was conducted by scientists at the University of California, San Francisco and University of Cambridge. The research was led by co-senior investigator David Rowitch, MD, PhD, a Howard Hughes Medical Institute investigator at UCSF.

The investigation, conducted in mice and in human tissue, showed that repair of nerve fibers is hampered by biochemical signals that inhibit the development of cells known as oligodendrocytes, which function as repair workers in the brain.

Oligodendrocytes form a protective sheath, known as myelin, that insulates the fibrous cables, or axons, radiating from nerve cells. In multiple sclerosis, the immune system's T cells and B cells attack oligodendrocytes, ultimately damaging the myelin sheath to the point that the electrical signals transmitted by the axons beneath it are disrupted.

Remarkably, the brain generally is able to recruit fresh, immature oligodendrocytes to the myelin sheath to repair the damage, for a time. This explains why, in the most common form of the disease, known as relapsing remitting MS, the symptoms -- which range from tingling and numbness in the limbs to loss of vision and paralysis -- disappear or are greatly reduced, for some times months or years at a time.

Ultimately, however, the repair process falters and the disease progresses. In their study, the team set out to see if they could determine what was slowing down myelin repair. They lesioned a small region of white matter in healthy mice, then monitored the repair process, examining the tissue after five, 10, and 14 days.

To find out which genes were contributing to three key stages in
'/>"/>