013 – Muscular Involvement in Lewis Rats with Experimental Neuromyelitis Optica
Magdalini Nigritinou (1) – Monika Bradl (1)
Center of Brain Research, Neuroimmunology Department, Medical University of Vienna, Vienna, Austria (1)
Neuromyelitis Optica (NMO) is an inflammatory disease of the central nervous system (CNS) characterized by the presence of autoantibodies against the water channel Aquaporin-4 (AQP4). Recent reports suggest that NMO patients also show extra-CNS muscle-related pathology. On the other hand, Myasthenia Gravis (MG) is a neuromuscular disease characterized by autoantibodies against Acetylcholine receptors (AChR) located on muscles. Both diseases are rare and interestingly, they have been described by numerous studies to coincide with a much higher probability than expected by chance. Those studies report disease conversion from NMO to MG and vice versa, but the underlying mechanisms are largely unknown. Our preliminary immunohistochemical analyses reveal that extraocular muscles (EOM) are much more susceptible than skeletal muscles in the context of experimental NMO (ENMO), and show prominent inflammation and EOM tissue destruction. Specifically, Hematoxylin-Eosin staining evidences massive infiltration of granulocytes and eosinophils. Abundant ED1+ macrophages, responsible for tissue damage and antigen presentation, are also shown to invade EOM fibers. Concomitantly, considerable numbers of CD3+ T cells are recruited in the EOM tissue and additional C9neo staining reveals the deposition of membrane attack complexes, which are known to perforate the cellular membranes. In most skeletal muscles however, only the connective tissue compartment contains T cells, macrophages and neutrophils, while the muscle fibers themselves are spared from destruction. Since EOM are also predominantly affected in MG patients, our preliminary data suggest that EOM could play a major role in antigen spreading mechanism from AQP4 to AChR and vice versa, which may further lead to the development of additional autoimmune disease in affected patients. This work is supported by FWF (DOC-Funds: DOC – 33 – B27).