Scarred blood vessels linked to APOE4 gene’s heightened Alzheimer’s risk

NEW YORK, 13 OCTOBER 2026 —

The APOE4 gene variant, identified as the strongest common genetic risk factor for Alzheimer’s disease, has been linked to a specific mechanism of vascular damage that may explain its role in the disease’s progression.

This process appears to contribute to the accumulation of amyloid-beta, a protein widely considered one of the earliest signs of Alzheimer’s pathology in the brain.

For years, the precise mechanism by which APOE4 increases vulnerability to dementia has remained a significant mystery for researchers. APOE4 is an allele, one of three common forms of the APOE gene, which produces a protein responsible for transporting fats in the bloodstream. While the variant is prevalent among those diagnosed with Alzheimer’s, it does not guarantee the disease.

Joel Blanchard, a neuroscientist at the Icahn School of Medicine at Mount Sinai in New York City, illustrated this prevalence by noting that in a room of ten people with Alzheimer’s disease, six would carry the APOE4 allele. However, many individuals who possess the variant never develop the condition, prompting scientists to investigate what specific biological changes the gene induces to make the brain susceptible.

A critical clue emerged from the study of individuals who exhibited unusual resilience to the genetic risk. In 2024, researchers analyzed more than 3,500 people, including those carrying two copies of APOE4 who had not developed Alzheimer’s. Genetic analysis of these resilient individuals revealed a mutation resulting in significantly lower levels of fibronectin in their blood vessels. Fibronectin is a protein that acts as a cellular superglue to assist in wound healing.

The earlier study suggested that excessive fibronectin could impede the brain’s ability to clear amyloid-beta, leading to the plaque buildup that characterizes the disease.

This finding prompted Blanchard and his colleagues to reverse the prevailing assumption in the field. While it was generally thought that Alzheimer’s disease causes blood vessels to break down, the team sought to determine if vascular damage might actually precede the disease. To investigate, they constructed a detailed atlas mapping gene expression across the human brain vasculature at a cellular level.

By integrating data from three existing brainwide maps, the atlas represented 66,000 cells from 220 people, allowing the team to compare gene activity in individuals with two copies of APOE4 against those with less harmful variants.

The analysis revealed distinct cellular differences in APOE4 carriers. These individuals had fewer pericytes, which are starfish-shaped cells that wrap around and stabilize blood vessels. Conversely, they exhibited higher numbers of myofibroblasts, cells typically formed during tissue injury that produce fibronectin. While the atlas provided a static snapshot of these differences, it could not confirm whether pericytes were transforming into myofibroblasts.

To test this hypothesis, the researchers utilized 3-D models of human brain tissue grown from stem cells. In models carrying two copies of APOE4, pericytes began adopting the characteristics of scar-producing myofibroblasts. This transformation offered a mechanistic explanation for the findings in resilient carriers, as myofibroblasts generate large amounts of fibronectin. When the researchers inhibited fibronectin production in these models, amyloid accumulation decreased.

The team also identified a potential trigger for this cellular shift. In the APOE4 models, signaling through the immune molecule TGF-beta drove pericytes toward the scar-producing state. Blocking this signaling pathway in both cell models and aged mice restored the proportion of blood vessels stabilized by pericytes.

Abdel Ali Belaidi, a neuroscientist at the Florey Institute of Neuroscience and Mental Health in Parkville, Australia, described the TGF-beta data as particularly interesting because inhibiting the protein reversed some of APOE4’s effects on pericytes. However, he noted that TGF-beta performs numerous functions throughout the body, making it a challenging target for safe drug development.

The damage to the brain’s blood vessels is only one of several pathways through which APOE4 is linked to Alzheimer’s disease. Other studies have demonstrated that the gene variant alters inflammation and interacts with tau, another protein associated with the disease. The complex interplay of these changes remains a greater mystery than a single study can resolve.

As Blanchard stated, the field is progressing toward a comprehensive answer, with this new understanding of vascular scarring providing a crucial piece of the puzzle regarding how APOE4 compromises brain health.