Insights into the transcriptomic heterogeneity of brain endothelial cells in normal aging and Alzheimer's disease

Drug development for Alzheimer's disease is extremely challenging, as demonstrated by the repeated failures of amyloid-β-targeted therapeutics and the controversies surrounding the amyloid-β cascade hypothesis. More recently, advances in the development of Lecanemab, an anti-amyloid-β monoclonal antibody, have shown positive results in reducing brain A burden and slowing cognitive decline in patients with early-stage Alzheimer's disease in the Phase III clinical trial (Clarity Alzheimer's disease). Despite these promising results, side effects such as amyloid-related imaging abnormalities (ARIA) may limit its usage. ARIA can manifest as ARIA-E (cerebral edema or effusions) and ARIA-H (microhemorrhages or superficial siderosis) and is thought to be caused by increased vascular permeability due to inflammatory responses, leading to leakages of blood products and protein-rich fluid into brain parenchyma. Endothelial dysfunction is an early pathological feature of Alzheimer's disease, and the blood-brain barrier becomes increasingly leaky as the disease progresses. In addition, APOE4, the strongest genetic risk factor for Alzheimer's disease, is associated with higher vascular amyloid burden, increased ARIA incidence, and accelerated blood-brain barrier disruptions. These interconnected vascular abnormalities highlight the importance of vascular contributions to the pathophysiology of Alzheimer's disease. Here, we will closely examine recent research evaluating the heterogeneity of brain endothelial cells in the microvasculature of different brain regions and their relationships with Alzheimer's disease progression.