A hormone produced during pregnancy helps to push multiple sclerosis into remission in mice, Canadian researchers have found.

Scientists have long known that MS tends to ease during pregnancy. The finding prompted Samuel Weiss of the Hotchkiss Brain Institute at the University of Calgary and his team to look at whether prolactin reverses damage from MS in mice.

The hormone prolactin leads to the regeneration of protective nerve coatings, Dr. Samuel Weiss says.
(CBC)

The results appear in Wednesday's issue of the Journal of Neuroscience.

Multiple sclerosis causes the body's immune system to attack the protective coating around nerve cells called myelin, leading to damage that cannot be repaired. Reduction in myelin leads to progressive loss of sensation and movement in MS. 

Prolactin stimulates breast development and milk production and has been tested in humans for other reasons.

"It's early to be confident that prolactin will definitely work with people," said Weiss. "But prolactin represents the first example of any molecule, in this case a naturally occurring molecule, that can actually boost the repair of myelin."

New direction for research

While current MS treatments are designed to prevent new damage in patients in earlier stages of the disease, there is nothing to repair myelin that has already been destroyed. 

"This may give us some ways to now focus on protecting the brain, as opposed to giving therapies that just reduce the attacks," said Dr. Jock Murray, a professor of medicine at Dalhousie University and founding director of its multiple sclerosis research unit.

The Calgary team compared pregnant and virgin female mice of the same age to count the number of myelin-producing cells. They found pregnant mice had:

• Twice as many of the cells.
• 50 per cent more myelin coating their nerve cells after giving birth.
• Twice as much new myelin after it was chemically destroyed.

Prolactin may help promote growth of myelin, although trials for MS treatments based on the findings remain about five years away.

Prolactin may also be beneficial for other diseases in which myelin is involved, such as spinal cord injuries and stroke, said Fred Gage of the Salk Institute, who did not participate in the research.

Multiple sclerosis affects about 75,000 Canadians.

The study was funded by the Canadian Institutes of Health Research and the Multiple Sclerosis Society of Canada.