Fig. 2

The glymphatic and meningeal lymphatic pathways for brain waste clearance in different health conditions. In healthy adult rodents (left panel), CSF glymphatic influx is facilitated by polarized AQP4 richly expressed at the astrocyte endfeet, while the flow of CSF-ISF along the glymphatic pathway clears the parenchyma solute (including Aβ), which is then drained into the cervical lymph nodes by the extensive meningeal lymphatic vasculature on the dorsal and basal regions of the brain. On the other hand, aging, sleep deprivation, and vascular injury (right panel) are associated with impairments in the glymphatic function, resulting in reduced CSF glymphatic influx and ISF solute clearance. Moreover, aging is also associated with morphological and functional alterations in the meningeal lymphatics that result in reduced lymphatic drainage into the deep cervical lymph nodes (CSF, cerebrospinal fluid; AQP4, aquaporin 4; ISF, interstitial fluid; Aβ, amyloid beta; dcLN, deep cervical lymph nodes)