AQP4 and brain edema: In particular, AQP4 facilitates clinically important water movement into and out of the brain in the development and resolution of brain edema and modulation of AQP4 expression or function is also predicted to modulate glial scar formation, which may be of clinical utility in traumatic injury, tumour and infection; moreover, recent data suggest increase extracellular space volume in AQP4 deficiency and impaired K+ reuptake by AQP4-null astrocytes, which may be related to functional significant AQP4-K+ channel interactions [12].