APOE4 turns brain vessel cells into scar producers in lab-grown tissue, a Cell paper reports
Joel Blanchard's Mount Sinai team reports in Cell that APOE4 pushes brain vessel cells toward a scar-producing state in lab-grown tissue. In people the evidence is a comparison of cell counts, so the link to amyloid rests on models.
The Scientist · Science desk
What happened
- The team stitched three existing brainwide gene-expression maps into one atlas of the brain's vasculature covering 66,000 cells from 220 people.
- Carriers of two APOE4 copies had fewer pericytes, the cells that wrap and stabilize vessels, and more fibronectin-producing myofibroblasts than people with less harmful variants.
- In stem-cell-grown 3-D brain tissue carrying two copies of APOE4, pericytes began taking on the traits of scar-producing myofibroblasts.
- When the researchers stopped cells in those models from making fibronectin, amyloid accumulation dropped.
- TGF-beta signaling helped drive pericytes toward the scar state, and blocking it restored the share of vessels they wrap in cell models and aged mice.
Why it matters
- contradiction Blanchard said the field's prevailing thought is that Alzheimer's is "so bad that the blood vessels break down". A vessel-first order would reverse that, and this paper tests the reversal in models without settling it in patients.
- constraint Belaidi of the Florey Institute called the TGF-beta result interesting but said the protein does many jobs across the body, which makes it difficult to target safely with a drug.
- constraint Other studies tie APOE4 to inflammation and to tau, and the source says how these changes fit together is more than one study can solve, so vessel scarring cannot be assumed to account for the whole risk.
The atlas is the human half of the evidence. Averaged over the donors, it holds about 300 cells per person [15]. The Science News account does not say how many of the 220 donors carried two copies of APOE4, so the size of the comparison group is unknown [7].
The map is a snapshot. It could not show whether the missing pericytes were turning into myofibroblasts [9]. That step, and the steps after it, were tested in models: the cell switch in lab-grown tissue [10], the amyloid drop in models where fibronectin production was blocked [11], and the TGF-beta experiment in cell models and aged mice [12]. In people, the finding is an association. The causal claim comes from the models.
Blanchard, a neuroscientist at the Icahn School of Medicine at Mount Sinai, put the clinical link in plain numbers [2]. "If you had a room of 10 people with Alzheimer's disease, and you asked how many of those people have the APOE4 allele, six of them would," he said [3]. Many carriers still never develop the disease [4].
A 2024 analysis of more than 3,500 people looked at that group. Some carried two copies of APOE4 and had not developed Alzheimer's, and they shared a DNA mutation that left their blood vessels with far lower fibronectin [5]. Myofibroblasts make large amounts of fibronectin [14]. The 2024 researchers suggested that too much of it could make amyloid-beta harder for the brain to clear [6].
A human genetic result and a fibronectin-blocking experiment in models point the same way from different directions. In our view that agreement is the strongest part of the case. Whether lowering fibronectin lowers amyloid in a living brain is still open. The amyloid drop is reported in the models, and the Science News account includes no amyloid measurement from the aged mice [11][12].
What to watch
- The Cell paper's breakdown of how many of the 220 donors carried two APOE4 copies; it sets how much weight the atlas comparison can bear.
- Amyloid measurements in living animals after fibronectin or TGF-beta is blocked, since the amyloid drop so far comes from models.
- Whether any way of dampening TGF-beta signaling in brain vessels can be made safe enough to test in people.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence55
- Adoption
- Insufficient
- Hype gap−10
- Incentives
- Insufficient
- Confidence60
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Researchers report on September 24 in Cell that APOE4 influences the production of scar tissue throughout the vascular connections carrying blood to and from the brain, and that this process may also contribute to the buildup of amyloid-beta.
- [2]
Joel Blanchard is a neuroscientist at the Icahn School of Medicine at Mount Sinai in New York City, and he and his colleagues built the atlas.
- [3]
"If you had a room of 10 people with Alzheimer's disease, and you asked how many of those people have the APOE4 allele, six of them would," Blanchard said.
- [4]
Many people who carry APOE4 never develop Alzheimer's disease.
- [5]
In 2024, researchers examined more than 3,500 people, including some who carried two copies of APOE4 but had not developed Alzheimer's; genetic analysis showed they had a mutation meaning their blood vessels had far lower levels of fibronectin.
- [6]
Fibronectin is a kind of cellular superglue that assists wound healing, and the 2024 researchers suggested that too much of it could make it harder for the brain to clear amyloid-beta.
- [7]
The team stitched together data from three existing brainwide maps into an atlas of gene expression in the human brain vasculature that represented 66,000 cells from 220 people, and compared people with two copies of APOE4 to those with less harmful variants.
- [8]
APOE4 carriers had fewer pericytes, the starfish-shaped cells that wrap around and stabilize blood vessels, and higher numbers of myofibroblasts, cells normally formed during tissue injury that pump out fibronectin.
- [9]
The map offered a snapshot but could not show whether the missing pericytes were actually transforming into myofibroblasts.
- [10]
In 3-D models of human brain tissue grown from stem cells and carrying two copies of APOE4, pericytes began taking on the characteristics of scar-producing myofibroblasts.
- [11]
When the researchers prevented cells in their models from producing fibronectin, amyloid accumulation dropped.
- [12]
In the APOE4 models, signaling through the immune molecule TGF-beta helped drive pericytes toward the scar-producing state, and blocking that signaling in cell models and aged mice restored the proportion of blood vessels wrapped by pericytes.
- [13]
Abdel Ali Belaidi, a neuroscientist at the Florey Institute of Neuroscience and Mental Health, called the TGF-beta data "particularly interesting" because inhibiting the protein reversed some of APOE4's effects on pericytes, but said TGF-beta performs many jobs throughout the body, making it a difficult molecule to target safely with a drug.
- [14]
Myofibroblasts produce large amounts of fibronectin.
- [15]
The atlas averages about 300 cells per donor (66,000 cells across 220 people).
- [16]
Blanchard said: "The prevailing thought in the field is basically that the Alzheimer's disease is so bad that the blood vessels break down," and that his team wanted to ask "Is it the other way around?"
- [17]
Damage to the brain's blood vessels is only one of many ways APOE4 has been linked to Alzheimer's; other studies have shown the variant alters inflammation and interacts with tau, and how these changes fit together is a greater mystery than one study can solve.
Sources
1 independent publisher whose own reporting we read for this story.
- sciencenews.orgScarred blood vessels may be one clue to APOE4’s Alzheimer’s risk
1 article · October 12, 2026
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