One Sentence Summary: In cerebral small vessel disease, endothelial dysfunction leads to white matter vulnerability which is reversible in a rat model with endothelial stabilizing drugs.Abstract: Dementia is a major social and economic problem for our ageing population. One of the commonest causes of dementia in the elderly is cerebral small vessel disease (SVD).Magnetic resonance scans of SVD patients typically show white matter abnormalities, but we do not understand the mechanistic pathological link between blood vessels and white matter myelin damage. Hypertension is suggested as the cause of sporadic SVD, but a recent alternative hypothesis invokes dysfunction of the blood brain barrier as the primary cause. Here, in a rat model of SVD, we show that endothelial cell (EC) dysfunction is the first change in development of the disease. Dysfunctional ECs secrete heat shock protein 90-alpha, which blocks oligodendroglial differentiation, contributing to impaired myelination. Treatment with ECstabilizing drugs reversed these EC and oligodendroglial pathologies in the rat model. EC and oligodendroglial dysfunction were also observed in humans with early, asymptomatic SVD pathology. We identified a loss-of-function mutation in ATPase11B which caused the EC dysfunction in the rat SVD model, and a single nucleotide polymorphism (SNP) in ATPase11B that was associated with white matter abnormalities in humans with SVD. We show that EC dysfunction is a cause of SVD white matter vulnerability and provide a therapeutic strategy to treat and reverse SVD in the rat model which may also be of relevance to human SVD.

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