Differences in distribution and regulation of astrocytic aquaporin-4 in human and rat hydrocephalic brain

A. D. Skjolding, A. V. Holst, H. Broholm, H. Laursen and M. Juhler (2013) Neuropathology and Applied Neurobiology39, 179–191 Differences in distribution and regulation of astrocytic aquaporin‐4 in human and rat hydrocephalic brain Aims: 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