title: Differences in distribution and regulation of astrocytic aquaporin-4 in human and rat hydrocephalic brain.
abstract: OBJECTIVE
  Aquaporin-4 (AQP4) is the most abundant cellular water channel in brain and could be a molecular basis for a cerebrospinal fluid absorption route additional to the arachnoid villi. In the search for 'alternative' cerebrospinal fluid absorption pathways it is important to compare experimental findings with human pathophysiology. This study compares expression of AQP4 in hydrocephalic human brain with human controls and hydrocephalic rat brain.
  
  
  METHODS
  Cortical biopsies from patients with chronic hydrocephalus (n = 29) were sampled secondary to planned surgical intervention. AQP4 in human hydrocephalic cortex relative to controls was quantified by Western blotting (n = 28). A second biopsy (n = 13) was processed for immunohistochemistry [glial fibrillary acidic protein (GFAP), CD68, CD34 and AQP4] and double immunofluorescence (AQP4 + GFAP and AQP4 + CD34). Brain tissue from human controls and kaolin-induced hydrocephalic rats was processed in parallel. Immunohistochemistry and immunofluorescence were assessed qualitatively.
  
  
  RESULTS
  Western blotting showed that AQP4 abundance was significantly increased (P < 0.05) in hydrocephalic human brain compared with controls. AQP4 immunoreactivity was present in both white and grey matter. In human brain (hydrocephalic and controls) AQP4 immunoreactivity was found on the entire astrocyte membrane, unlike hydrocephalic rat brain where pronounced endfeet polarization was present. Endothelial AQP4 immunoreactivity was not observed.
  
  
  CONCLUSIONS
  This study shows a significant increase in astrocytic AQP4 in human hydrocephalic cortex compared with control. Cell type specific expression in astrocytes is conserved between rat and human, although differences of expression in specific membrane domains are seen. This study addresses direct translational aspects from rat to human, hereby emphasizing the relevance and use of models in hydrocephalus research.
authors.affiliation: University Clinic of NeurosurgeryLaboratory of Neuropathology, Copenhagen University Hospital, RigshopitaletDepartment of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: A D
authors.initials: AD
authors.lastname: Skjolding
authors.affiliation: University Clinic of NeurosurgeryLaboratory of Neuropathology, Copenhagen University Hospital, RigshopitaletDepartment of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: A V
authors.initials: AV
authors.lastname: Holst
authors.affiliation: University Clinic of NeurosurgeryLaboratory of Neuropathology, Copenhagen University Hospital, RigshopitaletDepartment of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: H
authors.initials: H
authors.lastname: Broholm
authors.affiliation: University Clinic of NeurosurgeryLaboratory of Neuropathology, Copenhagen University Hospital, RigshopitaletDepartment of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: H
authors.initials: H
authors.lastname: Laursen
authors.affiliation: University Clinic of NeurosurgeryLaboratory of Neuropathology, Copenhagen University Hospital, RigshopitaletDepartment of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Juhler
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D051401:Aquaporin 4 / Q000378:metabolism*; D001253:Astrocytes / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D006849:Hydrocephalus / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D051381:Rats; D055815:Young Adult
chemical_list: D051401:Aquaporin 4