APOE4 Triggers Brain Blood Vessel Scarring — and TGF-β Inhibition May Reverse It

Cerebrovascular disease — the deterioration of blood vessels supplying the brain — is a major but underappreciated feature of Alzheimer's disease (AD). Understanding why it occurs has been elusive, especially in relation to APOE4, the gene variant carried by roughly 25% of people and responsible for a two- to fourfold increase in AD risk.

Researchers at the Icahn School of Medicine at Mount Sinai constructed a single-cell transcriptomic atlas of human brain vasculature, comparing APOE4 carriers to non-carriers. They found that APOE4 brains had significantly fewer pericytes — specialized cells that wrap around capillaries, regulate blood flow, and maintain the blood-brain barrier. In their place appeared a population of myofibroblast-like cells co-expressing genes for contraction and extracellular matrix production, a pattern confirmed via immunostaining in both human and mouse APOE4 brains.

The team demonstrated that APOE4 pericytes actively transition into these myofibroblasts, which then secrete fibronectin. This fibronectin accumulation promotes vascular amyloid deposition — a hallmark of cerebrovascular AD pathology. Computational and experimental analyses pinpointed elevated transforming growth factor beta (TGF-β) signaling as the molecular driver of this pericyte-to-myofibroblast transition.

Most striking was the therapeutic finding: inhibiting TGF-β signaling restored normal pericyte coverage and reduced vascular fibrosis and amyloid burden to levels comparable to APOE3 (non-risk) carriers. This positions TGF-β as a targetable mechanism — not merely a correlate — of APOE4-driven cerebrovascular pathology.

For clinicians and researchers, this work reframes APOE4's vascular damage as a reversible cellular process rather than an inevitable genetic fate. Caveats include reliance on the abstract alone; full methodology, sample sizes, and mouse model specifics await publication review.