[Astrocytopathy in neuromyelitis optica, multiple sclerosis and Baló's disease]

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) while neuromyelitis optica (NMO) is an inflammatory disease of the CNS that selectively affects the optic nerves and spinal cord. An antibody for aquaporin-4 (AQP4), which is a water channel located in astrocyte foot process, is specifically positive for NMO and antibody and complement dependent astrocytic damage is thought to be a main cause of NMO. Baló's disease is characterized by alternating rings of demyelination and preserved myelin. We pathologically compared the astrocytic changes among autopsied cases with these CNS demyelinating diseases. NMO, MS and Baló's disease shared with reduced AQP4 immunoreactivity independent of antibodies and complements. The pathological finding was accompanied with a reduced immunoreactivity of connexin 43 and perivascular lymphocytic cuffing predominantly composed by T cells. The loss of astrocytic proteins such as AQP4 and connexin 43 preceded the loss of myelin proteins in some lesions. These features suggest astrocyte damages resulting in the loss of connexin 43 cause demyelination through the impairment of interaction between astrocytes and oligodendrocytes and the pathomechanism involves a T cell reaction.