Interestingly, an in vitro study demonstrated that AQP4–IgG binding to astrocytes alters AQP4 polarized expression leading to increased permeability of the astrocyte/endothelial barrier, reversed by application of an anti-VEGF-A blocking antibody, suggesting the potential role of VEGF-A in NMO pathology (98). Here, AQP4 is linked to neuromyelitis optica.