Reframing TDP-43 in Alzheimer's disease: From co-pathology to neurovascular culprit.

Alzheimer's disease (AD) is widely recognized as a multifactorial disorder involving neurovascular and glial dysfunction beyond amyloid-β and tau pathology. In this Perspective, we synthesize recent evidence to propose a conceptual framework linking transactive response (TAR) DNA-binding protein 43 kDa (TDP-43) to neurovascular unit (NVU) disruption in AD. Traditionally considered a neuronal co-pathology, TDP-43 also aggregates in astrocytes and endothelial cells, impairing blood-brain barrier (BBB) integrity, glymphatic clearance, and metabolic homeostasis. Endothelial TDP-43 loss disrupts β-catenin signaling and fibronectin, triggering vascular breakdown and neuroinflammation. Astrocytic perivascular aggregates correlate with reduced aquaporin-4 (AQP4) and CD146, further compromising clearance pathways. These vascular-glial mechanisms may accelerate AD progression and help explain clinical heterogeneity and limited therapeutic response in TDP-43-positive patients. We argue for the reclassification of TDP-43 as a potential upstream driver of disease progression. Such a shift would support the development of integrative biomarkers and precision treatment strategies targeting NVU dysfunction. HIGHLIGHTS: Transactive response (TAR) DNA-binding protein 43 kDa (TDP-43) may act as a driver of neurovascular dysfunction in Alzheimer's disease (AD). We propose reclassifying TDP-43 from co-pathology to upstream contributor. TDP-43 affects endothelial cells and astrocytes, disrupting blood-brain barrier (BBB) and clearance. Neurovascular unit (NVU) dysfunction links TDP-43 to inflammation, hypoperfusion, and cognitive decline. A vascular-glial model of AD opens new therapeutic and biomarker opportunities.