A Age Related Vascular Senescence: Mystery of Blood-brain Barrier Dysfunction in Neurodegeneration

The pathophysiology of neurodegenerative illnesses is increasingly understood to be influenced by vascular aging, with blood-brain barrier (BBB) disruption emerging as a crucial mechanistic connection. Comprising endothelial cells, pericytes, astrocytes, and microglia, the BBB is a complex neurovascular unit (NVU) that strictly regulates molecular trafficking and shields neural tissue from circulating toxins and immune cells, therefore maintaining central nervous system homeostasis. The integrity of the BBB is compromised as people age due to structural and functional changes in the cerebrovasculature, such as endothelial senescence, pericyte loss, mitochondrial dysfunction, and persistent low-grade inflammation. These alterations speed up neuronal damage and encourage the development of classical proteinopathies like tau aggregation and amyloid-β by making it easier for neurotoxic proteins, immunological mediators, and metabolic waste to enter the brain parenchyma. BBB disruption is both an early occurrence and a factor in the development of neurodegenerative diseases including Alzheimer's disease, cerebral amyloid angiopathy, and vascular dementia. It exacerbates neuroinflammation, hinders clearance processes, and contributes to cognitive decline. Recent developments in single-cell omics, fluid biomarkers, and molecular imaging have made it possible to identify and characterize BBB failure in preclinical and clinical contexts, creating new opportunities for early diagnosis and treatment. Restoring BBB function and addressing vascular aging are two viable approaches to alter the course of neurodegenerative illnesses and enhance their prognoses. The processes, effects, and translational potential of vascular aging and BBB degradation in neurodegeneration are summarized in this review, which also identifies new treatment targets and research objectives for the future.