Astrogliosis inhibition attenuates hydrocephalus by increasing cerebrospinal fluid reabsorption through the glymphatic system after germinal matrix hemorrhage

Abstract

Germinal matrix hemorrhage (GMH) results from the rupture of the immature thin-walled blood vessels and consequent bleeding into the subependymal germinal matrix and possible lateral ventricles. The purpose of this study is to investigate how astrogliosis impacts the glymphatic-meningeal lymphatic system in cerebrospinal fluid (CSF) reabsorption after GMH and how the anti-scarring agent olomoucine attenuates post-hemorrhagic hydrocephalus. GMH was induced by stereotaxic collagenase infusion into P7 Sprague-Dawley rats of both sexes. Western blot and immunofluorescence were used to assess astrogliosis and how astrogliosis affects glymphatic function by measuring Aquaporin-4 expression. Intracisternal injection of fluorescence tracer was used to measure CSF diffusion throughout the brain, its dispersion in the paravascular area and CSF drainage into the deep cervical lymph nodes at 28 days after GMH. Both short-term and long-term behavioral tests were used to assess the neurological outcomes. Nissl staining was used to assess the morphological changes at 28 days after hemorrhage. GMH elicited astrogliotic scarring and reduced the exchange between CSF and interstitial fluid, as well as CSF reabsorption through the meningeal lymphatic vessels. This might be associated with redistribution of Aquaporin-4. Olomoucine ameliorated scar tissue formation and attenuated post-hemorrhagic hydrocephalus. These findings of this study suggested that the glymphatic system might play a role in CSF reabsorption in neonates following GMH. Scar tissue formation impairs this CSF clearance route, and therefore astrogliosis inhibition might be a potential therapeutic strategy for neonatal post-hemorrhagic hydrocephalus.

Keywords: Aquaporin-4; Astrogliosis; Germinal matrix hemorrhage; Glymphatic system; Post-hemorrhagic hydrocephalus.