Early disruption of glial communication via connexin gap junction in multiple sclerosis, Baló's disease and neuromyelitis optica.

Multiple sclerosis (MS), neuromyelitis optica (NMO), and Baló's disease (BD) are inflammatory demyelinating diseases of the CNS. We previously reported anti-aquaporin-4 (anti-AQP4) antibody-dependent AQP4 loss occurs in some NMO patients, while antibody-independent AQP4 astrocytopathy can occur in heterogeneous demyelinating conditions, including MS, NMO and BD. To investigate the relationship between astrocytopathy and demyelination, we focused on connexins (Cxs), which form gap junctions (GJs) between astrocytes and oligodendrocytes and maintain homeostasis in the CNS. We evaluated expression of astrocytic Cx43/Cx30 and oligodendrocytic Cx47/Cx32 in autopsied materials from MS, NMO and BD patients. Astrocytic Cx43 and oligodendrocytic Cx32/Cx47 expressions were significantly diminished in both demyelinated and preserved myelin layers in all BD samples. In the leading edge of BD lesions, Cx43 and AQP4 loss preceded Cx32/Cx47 loss. Half of the NMO and MS samples showed preferential loss of astrocytic Cx43 expression in actively demyelinating and chronic active lesions, where heterotypic Cx43/Cx47 astrocyte-oligodendrocyte GJs were lost. Cases with Cx43 loss were significantly associated with rapid disease progression, regardless of the disease phenotype. Pathologically, Cx43 loss was frequently accompanied by distal oligodendrogliopathy. Our findings suggest that Cx43 astrocytopathy can occur in MS, BD and NMO. Moreover, astrocytic Cx43 loss may be associated with disease aggressiveness and distal oligodendrogliopathy in demyelinating conditions. Early disruption of glial communications via GJs may cause loss of glia syncytium, thereby inducing oligodendroglial damage and myelin loss. Inhibition of Cx hemichannels and restoration of GJs may be a possible therapeutic target for demyelinating disorders.