Brain aquaporin expression in development and disease

Aquaporins (AQPs) are channels that participate in water homeostasis in various organs including the kidney and brain. Several classes of these including AQP1, AQP4, and AQP9 are expressed, chiefly by glial cells, in the healthy human brain in a region-specific manner. Cerebral cortical expression of aquaporins has been most widely studied and has been found to be altered in specific diseases. We undertook a comprehensive study of aquaporin expression throughout the brain in postmortem human tissue affected by various age-associated diseases and found most conspicuous alteration in AQP1 expression in most of these. Comparison of these findings with expression throughout the lifespan as determined from studies of neonatal and pediatric brain autopsies showed that expression in adult disease recapitulates patterns found in the brain in infancy and early childhood. The results suggest that one component of astrocyte reaction to the presence of injury or disease may be activation of an earlier developmental phenotype with possible effects on water homeostasis and glymphatic function.