Researchers led by Daan van der Vliet, working with teams from the Netherlands Institute for Neuroscience, Leiden University, and Utrecht University, have identified a biological process that may help explain why multiple sclerosis (MS) becomes especially severe in some patients. Examining brain tissue from people with rapidly progressing MS, they found large numbers of unusual immune cells packed with fat droplets. The findings could point to new treatment strategies and future biomarkers that help predict how quickly the disease will worsen.
MS damages myelin, the fatty protective coating that surrounds nerve fibers in the brain and spinal cord. As this insulation breaks down, patients can develop neurological problems such as difficulty walking or vision impairment.
The disease does not follow the same path in everyone. Some individuals experience relatively mild symptoms for many years, while others develop serious disability and paralysis at a young age. Understanding why these outcomes differ has been a longstanding goal for researchers.
To investigate, the team focused on microglia, specialized immune cells in the brain that remove debris and support tissue repair. In patients with MS, however, these cells can undergo dramatic changes. They become filled with fat droplets, giving them a distinctive foamy appearance. Scientists refer to them as "foamy microglia."
"We found that patients with large numbers of these foamy microglia had a more severe disease course more frequently," says researcher Daan van der Vliet.
When Brain Cleanup Cells Become Overloaded
Normally, microglia help maintain brain health by clearing away damaged material. In MS, researchers believe that these cells may take in so much damaged myelin that they eventually exceed their capacity to process it.
"These cells are probably trying to do something good: clearing up damage," Van der Vliet explains. "But they become overloaded, so to speak. As a result, they can no longer effectively contribute to repair."
The study also revealed important molecular differences between MS lesions containing foamy microglia and those without them. Areas containing these cells were enriched with specific fats linked to long lasting inflammatory activity.
A More Complex View of Multiple Sclerosis
Inflammation has long been considered a major force driving MS progression. However, the new findings suggest the disease may involve a more complicated chain of events.
"It does not appear to be simply about the inflammatory response alone," says Van der Vliet. "These cells are probably attempting to clear damage and promote repair, but that process fails, worsens inflammation, and counteracts recovery."
According to the researchers, the results highlight how a mechanism that initially aims to protect the brain may eventually contribute to ongoing damage when it stops functioning properly.
Source: ScienceDaily
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