The Expression Of RGMa In Experimental Autoimmune Encephalomyelitis Rats

Objective Multiple sclerosis (MS) is a kind of inflammatory demyelinating diseases in central nervous system (CNS) with high disability. In pathology, it presents as multiple inflammatory demyelinating lesions and axonal injury in white matter of CNS and the latter is the main reason of disability of MS patients. In recent years, the regeneration of CNS has been the focus of nervous rehabilitation. The axonal growth inhibitors are considered to be one of the main factors causing the difficulty of CNS regeneration. Recently, the analyses of repulsive guidance molecule (RGM) expression in the model of spinal cord injury and brain injury indicate that RGM is not only an axonal guidance molecue and also an membrane protein limitating axonal growth of CNS. RGM participates and plays an important role in the transfer of axonal growth inhibitory signal after injury of CNS . However, no study has been reported about the RGM expression in multiple sclerosis. In our study, we analyzed the expression pattern of RGM in spinal cord and brain of rats in acute and chronic model of multiple sclerosis and speculated the possible function and mechanism of RGM in the occurrence, progress and prognosis of multiple sclerosis.Methods Experimental autoimmune encephalomyelitis (EAE) was induced by a single 400-μl subcutaneous injection of the following emulsions in the footpad: guinea pig spinal cord homogenate (GPSCH) (50% w/v in saline) emulsified in an equal volume of Freund's complete adjuvant (FCA) and 0.1 ml of Bordetella pertussis in the instep (approximately 4.0×109 live bacteria). The judgment of the model was done with HE stain. The rats were divided into four groups: the control, EAE acute group, EAE chronic group with complete remission and EAE chronic group with partial remission. Neurological deficits score was used to evaluate EAE. The Immunohistochemistry and double labeling of immunofluorescence were used to analyze the RGMa expression pattern in spinal cord and brain of rats in control and EAE groups. Reverse transcriptase Polymerase Chain Reaction (RT-PCR) was done to detect the expression of RGMa mRNA in the four groups.Results In control group and EAE groups, the expression of RGMa mRNA was highest in EAE acute group and decreased in EAE chronic groups. In brain and spinal cord of control rats, RGMa immunoreactivity was detected on cortex, grey matter, white matter fibers, oligodendrocyte, choroid plexus, hippocampus and few endothelial cells. In EAE acute group, the RGMa immunopositive cells significantly elevated as compared to control and accumulated in lesions and peri-lesional areas such as inflammatory cells aroud vessels and astrocytes. In EAE chronic group, the RGMa immunopositive cells decreased as compared with EAE acute group but still higher than the control and mainly expressed in the hyperplastic astrocytes surrounding the lesions.Conclusion The RGMa mRNA and RGMa protein were increased significantly in EAE acute group and decreased in EAE chronic groups but still higher than control group. It indicated that RGMa may play an important role in the onset and development of multiple sclerosis. RGMa Protein mainly expressed in the tissue or cells such as oligodendrocytes and astrocytes which greatly express axonal growth inhibitor. It indicated that RGMa may act as an axonal growth inhibitor in multiple sclerosis patients.