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

Aims:  Aqua¬porin-4 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 to human pathophysiology. This study compares expression of aquaporin-4 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. Aquaporin-4 in human hydrocephalic cortex relative to controls was quantified by western blotting (n=28). A second biopsy (n=13) was processed for immunohistochemistry (GFAP, CD68, CD34 and aquaporin-4) and double immunofluorescence (aquaporin-4+GFAP and aquaporin-4+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