Previous studies have shown that the increased MMP2 and MMP9 concentration in cerebrospinal fluid degrades junctional complex proteins between brain capillary endothelial cells, which further causes the disruption of BBB functions and ultimately promotes the formation of CNS-related diseases, such as ischemic stroke, multiple sclerosis, and glioblastoma18. The gene discussed is MMP2; the disease is multiple sclerosis.