Future of multiple sclerosis therapy: combining antigen-specific immunotherapy with strategies to promote myelin repair

Neuroprotection in multiple sclerosis: a therapeutic approach

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system that is pathologically characterized by inflammatory demyelination and neurodegeneration. Axonal damage, along with neuronal loss, occurs from disease onset and may lead to progressive and permanent disability. In contrast with the inflammatory pathways, the molecular mechanisms leading to MS neurodegeneration remain largely elusive. With improved understanding of these mechanisms, new potential therapeutic targets for neuroprotection have emerged. We review the current understanding of neurodegenerative processes at play in MS and discuss potential outcome measures and targets for neuroprotection trials.

Paranodal myelin retraction in relapsing experimental autoimmune encephalomyelitis visualized by coherent anti-Stokes Raman scattering microscopy

How demyelination is initiated is a standing question for pathology of multiple sclerosis. By label-free coherent anti-Stokes Raman scattering (CARS) imaging of myelin lipids, we investigate myelin integrity in the lumbar spinal cord tissue isolated from naïve SJL mice, and from mice at the onset, peak acute, and remission stages of relapsing experimental autoimmune encephalomyelitis (EAE). Progressive demyelinating disease is initially characterized by the retraction of paranodal myelin both at the onset of disease and at the borders of acute demyelinating lesions. Myelin retraction is confirmed by elongated distribution of neurofascin proteins visualized by immunofluorescence. The disruption of paranodal myelin subsequently exposes Kv1.2 channels at the juxtaparanodes and lead to the displacement of Kv1.2 channels to the paranodal and nodal domains. Paranodal myelin is partially restored during disease remission, indicating spontaneous myelin regeneration. These findings suggest that paranodal domain injury precedes formation of internodal demyelinating lesions in relapsing EAE. Our results also demonstrate that CARS microscopy is an effective readout of myelin disease burden.

Endoplasmic reticulum stress response as a potential therapeutic target in multiple sclerosis

Multiple Sclerosis (MS) is an inflammatory demyelinating disorder of the central nervous system (CNS). Since current treatments are aimed at nonspecifically down-regulating inflammation and natural mechanisms of repair and remyelination within the CNS are inadequate for recovery of function, MS patients presently only have available treatments that delay symptom progression. The complex nature of this disease means that only multifaceted treatments hold the promise of a cure. Recent studies indicate that the ER stress response, a cellular pathway that allows a cell to survive and recover from a stressful event, could be elicited to help the myelin-generating and myelin-support cells of the CNS survive inflammatory insult.

Myelin repair strategies: a cellular view

PURPOSE OF REVIEW

The development of successful myelin repair strategies depends on the detailed knowledge of the cellular and molecular processes underlying demyelination and remyelination in the central nervous system of animal models and in patients with multiple sclerosis (MS). Based on the complexity of the demyelination and remyelination processes, it should be expected that effective therapeutic approaches will require a combination of strategies for immunomodulation, neuroprotection, and myelin replacement. This brief review highlights recent cellular and molecular findings and indicates that future therapeutic strategies to enhance remyelination may also require combinatorial treatment to accomplish.

RECENT FINDINGS

The relapsing-remitting course of some forms of multiple sclerosis has typically fueled hope for effective repair of multiple sclerosis lesions, if demyelinating activity could be attenuated. Recent findings support the potential of endogenous neural stem cells and progenitor cells to generate remyelinating oligodendrocytes. Importantly, interactions with viable axons and supportive astrocytic responses are required for endogenous immature cells to fulfill their potential remyelinating capacity.

SUMMARY

The research described here will help in identifying the major obstacles to effective remyelination and potential therapeutic targets to guide development of comprehensive approaches for testing in animal models and eventual treatment of patients with multiple sclerosis.