Vision in patients with multiple sclerosis (MS) could be improved through the use of medication, a new study has found.
A mice study investigated the effect of indazole chloride (IndCl) on the pathology and function of the afferent visual pathway for the first time, which includes the eyes, optic nerve, and all brain structures responsible for receiving, transmitting, and processing visual information.
“IndCl has been previously shown in mice to reduce motor disability, increase myelination, and neuroprotection in the spinal cord and corpus callosum,” says Seema Tiwari-Woodruff, a professor of biomedical sciences at the UC Riverside School of Medicine and the study’s lead author.
“Its effects in the visual system, however, were not evaluated until now.
“Our study shows the optic nerve and optic tract, which undergo significant inflammation, demyelination, and axonal damage, are able to restore some function with IndCl treatment with successful attenuation in inflammation and an increase in remyelination.”
In MS, damage can often be caused to the optic nerve and other parts of the visual system, which results in around 50 per cent of patients with MS experiences optic neuritis – inflammatory demyelination of the optic nerve – 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 used IndCl to assess the impact 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, say researchers. In the lab, Professor Tiwari-Woodruff and her 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%.
“Measuring visual function and recovery in the presence of novel therapies can be used to screen more effective therapies that will protect axons, stimulate axon remyelination, and prevent ongoing axon damage,” says Professor Tiwari-Woodruff.
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.
“We treated the MS mice with IndCl at peak disease,” Professor Tiwari-Woodruff says.
“If the brain is highly diseased, some of the axons that could potentially restore visual function are too damaged and will not recover. There’s a point of no return.
“Our paper stresses that to acquire vision improvement, treatment must start early. Early treatment can recover 75%-80% of the original function.”
Tiwari-Woodruff stresses 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.
“There is a strong and urgent need to find a therapeutic candidate that restores neurological function in patients with MS,” Professor Tiwari-Woodruff adds.
“Therapeutics must target remyelination and prevent further axonal degeneration and neuronal loss. The good oestrogens, which have neuroprotective and immunomodulatory benefits, could be candidates for MS treatment.”