A new study found that treating a mouse model of multiple sclerosis with the pregnancy hormone estriol reversed the breakdown of myelin in the brain’s cortex, a key region affected in MS.

In MS, inflammation spurs the immune system to strip away the protective myelin coating around nerve fibers in the brain’s cortex, hampering electrical signals sent and received by the brain. Atrophy of the cortex in MS patients is linked to permanent worsening of disability, such as cognitive decline, visual impairment, weakness, and sensory loss.

Currently, no available treatments for MS can repair damage to myelin. Instead, these treatments target inflammation to reduce symptoms from flare-ups and new nerve tissue scarring. Previous University of California - Los Angeles Health Sciences-led research found that estriol, a type of estrogen hormone produced in pregnancy, reduced brain atrophy and improved cognitive function in MS patients.

In the new study, researchers treated a mouse model of MS with estriol and found that it prevented brain atrophy and induced remyelination in the cortex, indicating the treatment can repair damage caused by MS, rather than just slow the destruction of myelin.

Results of animal model studies sometimes do not translate to humans and may be years away from being a marketable treatment. However, this is the first study to identify a treatment that could repair myelin in the cortex, undoing some of the damage caused by MS.

The findings were published in the journal Laboratory Investigation.