Summary: A collaborative neurobiology study has identified a cellular mechanism linked to rapid, severe progression of multiple sclerosis (MS). Using advanced spatial and molecular methods on human post-mortem brain tissue, the multidisciplinary team found that clusters of lipid‑engorged immune cells — called “foamy microglia” — become pathologically overwhelmed after ingesting large amounts of damaged myelin. These foamy microglia lose their reparative capacity, intensify local inflammation, and appear to drive aggressive lesion expansion. The discovery highlights lipid metabolism as a therapeutic target and points to cerebrospinal fluid biomarkers that could help identify patients at high risk of rapid decline.
This work moves the clinical view of MS beyond a purely inflammatory model and provides specific, testable leads for drug development and early detection.
Key Facts
- Microglial transformation: Microglia are the brain’s resident immune cells that clear debris and support repair. In aggressively progressing MS, many microglia become filled with lipid droplets from degraded myelin and take on a foamy appearance.
- Waste-processing overload: When microglia ingest excessive myelin-derived fat, their lysosomal and metabolic systems become stressed. Overloaded microglia lose reparative functions, promote persistent inflammation, and hinder recovery.
- Distinct molecular profile: Lesions with foamy microglia show a unique molecular signature, including enrichment of oxylipins, bismonoacylglycerolphosphates, and cholesterol esters, which correlate with chronic, destructive inflammation.
- Human tissue analysis: Researchers analyzed inflammatory lesions from 28 deceased MS donors using integrated lipidomics, transcriptomics, proteomics, chemical proteomics, and histology to measure genes, proteins, and lipids at the same lesion sites.
- Potential fluid biomarkers: Specific lipid species linked to foamy microglia were detected in cerebrospinal fluid, suggesting non‑invasive markers that could predict rapid disease progression before clinical paralysis occurs.
- Therapeutic direction: The study identifies monoacylglycerol lipase (MAGL), a lipid‑metabolizing enzyme enriched in foamy lesions, as a candidate target. MAGL inhibition improved lesion recovery and reduced microgliosis in animal models, supporting ongoing drug development efforts.
Source: KNAW
Research overview
Led by Daan van der Vliet in collaboration with colleagues from the Netherlands Institute for Neuroscience, Leiden University, and Utrecht University, the research identifies a clear link between foamy microglia and severe MS progression. In brain tissue from patients who experienced rapid decline, investigators observed abundant immune cells overloaded with lipid droplets derived from myelin breakdown.
Why do outcomes vary so widely between patients?
Multiple sclerosis involves immune‑mediated damage to myelin, the fatty insulation around nerve fibers. Loss of myelin disrupts nerve signaling and leads to symptoms such as impaired mobility and visual problems. Clinical trajectories differ: some patients maintain relatively mild disability for decades, while others experience rapid, debilitating progression. Understanding the biological factors that determine these outcomes is essential for personalized care.
This study focused on microglia because these cells perform essential cleanup and repair functions. The team discovered that, in some patients, microglia ingest so much degraded myelin that lipid droplets accumulate and overwhelm cellular waste‑handling pathways. These foamy microglia are no longer effective repair agents; instead they contribute to lesion growth and chronic inflammation.
Overload and functional failure
Under normal conditions microglia remove debris and help restore tissue. But when confronted with massive myelin breakdown, the lipid load can exceed their capacity. The researchers found evidence of lysosomal stress, altered lipid metabolism, and heightened antigen‑presentation signatures in affected microglia, without the classical pro‑inflammatory profile typically expected. This distinct metabolic failure appears to perpetuate tissue damage rather than resolve it.
New perspective on MS pathology
These findings suggest that progression in MS is not driven solely by inflammation but also by metabolic dysfunction within lesion‑resident immune cells. Targeting lipid metabolism — rather than only suppressing inflammation — could therefore be a complementary strategy to prevent chronic lesion expansion and irreversible disability.
Advanced methods and human tissue strength
A major strength of the study is the use of well‑characterized human brain tissue from the Netherlands Brain Bank combined with cutting‑edge spatial multi‑omic techniques. This allowed simultaneous mapping of gene expression, protein distribution, and lipid composition within precisely defined lesion regions, revealing pathological patterns that might be missed in less detailed analyses.
Toward personalized treatment and biomarkers
The detection of specific oxylipins and other lipid markers in cerebrospinal fluid linked to foamy microglia opens the possibility of developing biomarkers for early identification of patients at risk of rapid progression. Such biomarkers could guide treatment choices and help enroll appropriate patients into clinical trials of lipid‑targeting therapies. Indeed, some candidate compounds that modulate lipid metabolism and lesion growth are already entering clinical testing.
Funding: This research was supported by the Gravitation programs Institute for Chemical Immunology (ICI) and the Institute for Chemical NeuroScience (iCNS).
Key Questions Answered
Q: Why does the brain’s own clean-up crew end up making multiple sclerosis worse?
A: When microglia ingest excessive myelin debris, their intracellular waste systems become overloaded. These cells accumulate lipid droplets, become dysfunctional as “foamy microglia,” and stop contributing to repair, instead sustaining inflammation and lesion growth.
Q: How did analysis of post-mortem tissue point to tests that could benefit living patients?
A: High-resolution mapping of preserved human lesions revealed characteristic lipid species produced in foamy microglia clusters. Because some of these lipids appear in cerebrospinal fluid, they offer candidate biomarkers detectable via lumbar puncture to identify patients at elevated risk earlier.
Q: Do current anti-inflammatory drugs miss the mark?
A: Anti-inflammatory therapies address an important part of MS pathology, but this study shows progression can involve metabolic failure within microglia. Combining anti‑inflammatory approaches with treatments that normalize lipid metabolism could better prevent chronic lesion expansion.
Editorial Notes
- Article edited by a Neuroscience News editor.
- Journal paper reviewed in full by the editorial team.
- Additional context added by staff for clarity and relevance.
About this multiple sclerosis research news
Author: Eline Feenstra
Source: KNAW
Contact: Eline Feenstra – KNAW
Image credit: Neuroscience News
Original Research: Open access. “Foamy microglia link oxylipins to disease progression in multiple sclerosis” by Daan van der Vliet et al., Nature Neuroscience. DOI: 10.1038/s41593-026-02302-3
Abstract
Foamy microglia link oxylipins to disease progression in multiple sclerosis
Multiple sclerosis (MS) is a chronic neuroinflammatory disease marked by expanding demyelinating white matter lesions that drive irreversible disability. The study identifies a distinct population of foamy GPNMB+ microglia/macrophages associated with lesion expansion in secondary progressive MS. Integrated lipidomic, transcriptomic, proteomic, chemical proteomic, and histological analyses of human postmortem MS lesions reveal disrupted lipid metabolism, lysosomal stress, and signatures of heightened phagocytosis and antigen presentation without classic pro‑inflammatory markers. Lesions with foamy microglia are enriched in oxylipins, bismonoacylglycerolphosphates, and cholesterol esters, and show increased B cell infiltration and IgG1. Monoacylglycerol lipase (MAGL), enriched in these lesions, emerged as a potential therapeutic target; MAGL inhibition promoted lesion recovery and reduced microgliosis in a mouse demyelination model. Oxylipins in cerebrospinal fluid correlate with the proportion of foamy lesions, suggesting candidate biomarkers for progression. These findings implicate disturbed lipid metabolism in chronic MS pathology and identify foamy microglia/macrophages as a promising cell type to target in progressive disease.