The antibody rHIgM22 facilitates hippocampal remyelination and ameliorates memory deficits in the cuprizone mouse model of demyelination.

Multiple sclerosis (MS) is a chronic, inflammatory demyelinating disease of the CNS. In addition to motor, sensory and visual deficits, MS is also characterized by hippocampal demyelination and memory impairment. We recently demonstrated that a recombinant human-derived monoclonal IgM antibody, which is designated rHIgM22 and currently in clinical development for people with MS, accelerates remyelination of the corpus callosum in the brains of cuprizone-treated mice. Here, we investigated the effects of rHIgM22 in the hippocampus and on hippocampal-dependent learning and memory in the same mouse model of cuprizone-induced demyelination and spontaneous remyelination. The degree of hippocampal myelination of cuprizone-fed mice treated with a single dose of rHIgM22 (10 mg/kg of body weight) was examined immediately after the end of the cuprizone diet as well as at different time points during the recovery period with regular food, and compared with that of cuprizone-fed animals treated with either vehicle or human IgM isotype control antibody. Mice fed only regular food were used as controls. Four or five mice per treatment group were examined for each time point. We demonstrate that treatment with rHIgM22 accelerated remyelination of the demyelinated hippocampus. Using two additional cohorts of mice and eight animals per treatment group for each cohort, we also demonstrate that the enhancing effects of rHIgM22 on hippocampal remyelination were accompanied by improved performance in the Morris water maze and amelioration of the memory deficits induced by cuprizone. These results further confirm the remyelination-promoting capabilities of rHIgM22 and support additional investigation of its therapeutic potential in MS.

rHIgM22 enhances remyelination in the brain of the cuprizone mouse model of demyelination.

Failure of oligodendrocyte precursor cells (OPCs) to differentiate and remyelinate axons is thought to be a major cause of the limited ability of the central nervous system to repair plaques of immune-mediated demyelination in multiple sclerosis (MS). Current therapies for MS aim to lessen the immune response in order to reduce the frequency and severity of attacks, but these existing therapies do not target remyelination or stimulate repair of the damaged tissue. Thus, the promotion of OPC differentiation and remyelination is potentially an important therapeutic goal. Previous studies have shown that a recombinant human-derived monoclonal IgM antibody, designated rHIgM22, promotes remyelination, particularly of the spinal cord in rodent models of demyelination. Here, we examined the effects of rHIgM22 in remyelination in the brain using the mouse model of cuprizone-induced demyelination, which is characterized by spontaneous remyelination. The myelination state of the corpus callosum of cuprizone-fed mice treated with rHIgM22 was examined immediately after the end of the cuprizone diet as well as at different time points during the recovery period with regular food, and compared with that of cuprizone-fed animals treated with either vehicle or human IgM isotype control antibody. Mice fed only regular food were used as controls. We demonstrate that treatment with rHIgM22 accelerated remyelination of the demyelinated corpus callosum. The remyelination-enhancing effects of rHIgM22 were found across different, anatomically distinct regions of the corpus callosum, and followed a spatiotemporal pattern that was similar to that of the spontaneous remyelination process. These enhancing effects were also accompanied by increased differentiation of OPCs into mature oligodendrocytes. Our data indicate strong remyelination-promoting capabilities of rHIgM22 and further support its therapeutic potential in MS.