Increased serum matrix metalloproteinase-9 in neuromyelitis optica: Implication of disruption of blood–brain barrier

Matrix metalloproteinase-9 (MMP-9) plays an important role in some neuroinflammatory diseases through the blood–brain barrier (BBB) disruption. To investigate the pathogenicity of MMP-9 in neuromyelitis optica (NMO), serum and CSF MMP-9 concentrations were measured in 13 NMO and 15 multiple sclerosis (MS) patients and 14 healthy controls, and correlated with clinical and laboratorial parameters. Serum MMP-9 concentrations were significantly higher in NMO than MS and controls, and correlated with EDSS score, CSF/serum albumin ratio, and CSF IL-8 concentrations. Our results indicate that MMP-9, promoted by elevated IL-8 activation, plays a crucial role in the pathogenesis of NMO through the BBB disruption.