ABSTRACT
Multiple sclerosis (MS) is a demyelinating disease of the CNS characterized by inflammation and neurodegeneration. Animal models that enable the study of remyelination in the context of ongoing inflammation are greatly needed for the development of novel therapies that target the pathological inhibitory cues inherent to the MS plaque microenvironment. We report the development of an innovative animal model combining cuprizone-mediated demyelination with transfer of myelin-reactive CD4(+) T cells. Characterization of this model reveals both Th1 and Th17 CD4(+) T cells infiltrate the CNS of cuprizone-fed mice, with infiltration of Th17 cells being more efficient. Infiltration correlates with impaired spontaneous remyelination as evidenced by myelin protein expression, immunostaining, and ultrastructural analysis. Electron microscopic analysis further reveals that demyelinated axons are preserved but reduced in caliber. Examination of the immune response contributing to impaired remyelination highlights a role for peripheral monocytes with an M1 phenotype. This study demonstrates the development of a novel animal model that recapitulates elements of the microenvironment of the MS plaque and reveals an important role for T cells and peripheral monocytes in impairing endogenous remyelination in vivo. This model could be useful for testing putative MS therapies designed to enhance remyelination in the setting of active inflammation, and may also facilitate modeling the pathophysiology of denuded axons, which has been a challenge in rodents because they typically remyelinate very quickly.
Subject(s)
Central Nervous System/pathology , Cuprizone/toxicity , Demyelinating Diseases/therapy , Monoamine Oxidase Inhibitors/toxicity , Myelin Sheath/metabolism , Th17 Cells/physiology , Adoptive Transfer , Animals , Cell Polarity/drug effects , Cells, Cultured , Central Nervous System/ultrastructure , Demyelinating Diseases/chemically induced , Disease Models, Animal , Freund's Adjuvant/toxicity , Interleukin-17/metabolism , Leukocyte Common Antigens/genetics , Mice , Mice, Inbred C57BL , Mice, Transgenic , Monocytes/pathology , Monocytes/ultrastructure , Myelin Proteins/metabolism , Myelin-Oligodendrocyte Glycoprotein/toxicity , Neutrophil Infiltration , Peptide Fragments/toxicity , Regeneration/drug effects , Th17 Cells/ultrastructure , Time FactorsABSTRACT
IL-10-deficient mice spontaneously develop intestinal inflammation, which has many similarities to Crohn's disease. Several reports suggest that epithelial cell death may increase the severity of colitis; however, decisive evidence is lacking. In the present report, we addressed whether and how epithelial cell death plays a role in the development of chronic colitis. We first examined the morphological characteristics of intestines of IL-10-deficient mice and found two forms of epithelial cell death (typical apoptosis and necrosis-like cell death) in colitis. To elucidate the pathological roles of epithelial cell death, we crossbred IL-10-deficient knockout mice with Bcl-2 transgenic mice, in which the anti-apoptosis protein Bcl-2 was overexpressed in intestinal epithelial cells, but not in immune cells. Epithelial cell-specific Bcl-2 protected IL-10 deficiency-induced colitis and markedly reduced their symptoms. Interestingly, morphological analysis revealed that Bcl-2 suppressed apoptosis and necrosis-like cell death, and better maintained mucosal barrier in IL-10-deficient mice. From the immunological aspect, Bcl-2 did not alter the activation of T-helper cell 1 but inhibited the growth of T-helper cell 17, suggesting that mucosal integrity may control the immune responses. These results provide genetic evidence demonstrating that epithelial cell death is crucial for the development of chronic colitis.
