Researchers report a drug – an estrogen receptor ligand called indazole chloride – has the potential to improve vision in patients with multiple sclerosis. The study, performed on mice induced with a model of MS, is the first to investigate IndCl's effect on the pathology and function of the complete afferent visual pathway. The afferent visual pathway includes the eyes, optic nerve, and all brain structures responsible for receiving, transmitting, and processing visual information.

Approximately 50 percent of patients with MS experience optic neuritis prior to showing initial symptoms. Almost all MS patients have impaired vision at some point during disease progression. Symptoms can include eye pain, blurred vision, and progressive vision loss that can lead to blindness, among other visual impairments.

The researchers at the University of California, Riverside, used IndCl to assess its effect on demyelinating visual pathway axons. The treatment induced remyelination and mitigated some damage to the axons that resulted in partial functional improvement in vision.

The visual pathway in mice is similar to that in humans. In the lab, the research group first induced the mouse model of MS. They let the disease progress for about 60 days and when the disease reached a peak between 15 and 21 days, they administered IndCl to half the mice. At the end of the experiment, they performed functional assay to measure the visual electrical signal; and immunohistochemistry to examine the visual pathway. The mice that received the drug showed improvement in myelination, with visual function improving by about 50 percent.

For researchers, the next question is how IndCl treatment induces functional remyelination in the visual pathway. They are now investigating new drugs that are analogues of IndCl. Currently approved MS drugs reduce inflammation but do not prevent neurodegeneration or initiate remyelination. Further, they only partially prevent the onset of permanent disability in patients with MS.

Results of mouse model studies sometimes do not translate to humans and may be years away from being a marketable treatment. Researchers stressed that although additional studies are required, the new findings show the dynamics of visual pathway dysfunction and disability in MS mice, along with the importance of early treatment to mitigate axon damage.

The study was published in Brain Pathology.