The cerebrovascular basement membrane: role in the clearance of β-amyloid and cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA), the accumulation of beta-amyloid (A beta) peptides in the walls of cerebral blood vessels, is observed in the majority of Alzheimer's disease (AD) brains and is thought to be due to a failure of the aging brain to clear A beta. Perivascular drainage of A beta along cerebrovascular basement membranes (CVBMs) is one of the mechanisms by which A beta is removed from the brain. CVBMs are specialized sheets of extracellular matrix that provide structural and functional support for cerebral blood vessels. Changes in CVBM composition and structure are observed in the aged and AD brain and may contribute to the development and progression of CAA. This review summarizes the properties of the CVBM, its role in mediating clearance of interstitial fluids and solutes from the brain, and evidence supporting a role for CVBM in the etiology of CAA.