Project description:Objective: Connexins are known to compose gap junctions by a pair of hemichannels connected in a head to head configuration. Each hemichannel is composed by hexameric cluster of connexins. There are 20 members of connexins known as connexin family in mice, and are expressed on each cell surface in different fashion. Connexin 30 (Cx30) is mainly expressed on the surface of oligodendroglia and astrocyte in central nervous system (CNS), but little is known about the functional relevance in neuroinflammatory diseases. To elucidate the role of Cx30 in the pathogenesis of neuroinflammatory disease, we induced experimental autoimmune encephalomyelitis (EAE) on Cx30 knock-out (Cx30-KO) mice and analyzed the clinical and neuropathological findings with wild-type control. Methods: C57BL/6J and Cx30-KO mice > 12 weeks of age were used in this study (N > 3 in each group). EAE was induced by immunization of mice with MOG35-55 peptide emulsified in CFA at a dose of 200 μg per mouse, followed by the administration of pertussis toxin (500 ng per mouse) on days 0 and 2. Mice were sacrificed and brain, spinal cord, spleen, and optic nerve were harvested for immunohistochemical analyses at the acute and chronic phases of EAE. Mice with EAE were scored as follows: 0, no disease; 1, limp tail; 2, abnormal gait and hind limb weakness (shaking); 2.5, paralysis of one hind limb; 3, paralysis of two hind limb; 3.5, ascending paralysis (able to move around); 4, tetraplegia; and 5, moribund (death). At the onset and chronic stage of EAE, mononuclear cells were isolated and analyzed by flow cytometry to check the distinct characteristics of cellular populations in inflamed CNS lesions. Results: Initial screening of immunohistological difference revealed basic activation of microglial cells in naïve Cx30-KO mice without any behavioral phenotype. Clinical signs of EAE were ameliorated in the Cx30-KO mice than in the control group mainly during the chronic phase of disease course. Immunohistochemical analyses of the fourth lumbar segment, brain and optic nerve revealed increased number of microglia in the Cx30-KO mice. Flow cytometric analysis also confirmed the findings. In contrast, there were no significant change in astroglial or oligodendroglial phenotype. Conclusion: Microglial activation appears to be the key factor in the Cx30-KO mice EAE with alleviation of chronic disease scores. Unexpectedly, microglia were already activated in naïve CNS, indicating protective phenotypic change of microglia in Cx30-KO mice.

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A novel animal model for secondary progressive multiple sclerosis by oligodendroglia-specific conditional connexin 47 knockout [Agilent]

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