Erythropoietin attenuates neurological and histological consequences of toxic demyelination in mice

Erythropoietin (EPO) reduces symptoms of experimental autoimmune encephalomyelitis (EAE) in rodents and shows neuroregenerative effects in chronic progressive multiple sclerosis. EPO's mechanisms of action in these conditions with shared immunological etiology are still unclear. Therefore, we employed a model of toxic demyelination allowing exclusion of T-cell mediated inflammation. In a 'double-blind' (for food/injections), placebo-controlled, longitudinal 4-arm design, 8-week old C57BL/6 mice (n=26/group) were assigned to cuprizone-containing (0.2%) or regular food (ground chow) for 6 weeks. After 3 weeks, mice were injected every other day with placebo or EPO (5,000IU/kg intraperitoneally) until end of cuprizone feeding. Half of the mice were exposed to behavioral testing, magnetic resonance imaging (MRI) and histology immediately after treatment cessation, whereas the other half were allowed a 3-week treatment-free recovery. Immediately after termination of cuprizone feeding, all toxin-exposed mice were compromised regarding vestibulomotor function/coordination, with EPO treated animals performing better than placebo. Likewise, ventricular enlargement after cuprizone as documented by MRI was less pronounced upon EPO. After 3-week recovery, remarkable spontaneous improvement was observed in all mice with no measurable further benefit in the EPO group ('ceiling effect'). Histological analysis of the corpus callosum revealed attenuation by EPO of the cuprizone-induced increase in microglial numbers and amyloid precursor protein accumulations as readout of inflammation and axonal degeneration. To conclude, EPO ameliorates neurological symptoms in the cuprizone model of demyelination possibly by reduction of inflammation-associated axonal degeneration in white matter tracts. These findings underscore the value of future therapeutic strategies for multiple sclerosis based on EPO/EPO variants.