Energy-dependent transport at dural lymphatic vessels is necessary for Aβ brain clearance in Alzheimer’s disease

Abstract

AbstractViewed as an imbalance between production and clearance of toxic Aβ peptides, Alzheimer’s disease is a candidate for therapies to augment brain waste removal. Prior work has shown that Aβ accumulates in meninges with aging as a byproduct of normal brain activity, in parallel with build-up of Aβ oligomers in neurons, blood vessels, and interstitial fluid. Using the TgF344-AD rat model of Alzheimer’s disease, we now report that dural lymphatic vessels specifically accumulate neurotoxic pyroglutamate amyloid beta (pE3-Aβ) with aging. Notably, accelerated amyloidosis is observed in meninges after ligation of cervical lymphatics, together with significantly increased pE3-Aβ and Aβ42 deposition in upstream brain regions implicated in Alzheimer’s disease. Blockade of lymphatic clearance is not sufficiently compensated by other efflux pathways, suggesting a necessary role of Aβ clearance at the level of lymphatics. We further report that dural lymphatic cells actively clear Aβ via energy-dependent mechanisms, and lymphatic Aβ transport is significantly impaired both in normal aging and in Alzheimer’s disease. Dural lymphatic cells isolated from the TgF344-AD rat show ultrastructural abnormalities in mitochondria and abnormal cytoplasmic inclusions, with a distinct transcriptional profile implicating failure of energy-dependent transport. Finally, using human meninges treated with FocusDeep tissue clearing, we demonstrate using whole mount panoramic imaging that dural lymphatic vessels comprise a structurally diverse intracranial vascular network that accumulates pE3-Aβ with aging, similar to the rat model. We conclude that intracranial meningeal and extracranial cervical lymphatic vessels are targets for Alzheimer’s disease therapies focused on improving amyloid clearance.One Sentence SummaryLymphatic vessels remove Aβ from the brain via energy-dependent active transport mechanisms, and blockage of extracranial lymphatic drainage is sufficient to cause significant acceleration of intracranial Alzheimer’s Aβ pathology in both meninges and brain.