Protective effects of pregnancy during MS have led to clinical trials of estriol, the pregnancy estrogen, in MS. Since estriol binds to estrogen receptor (ER) beta, ER beta ligand could represent a "next generation estriol" treatment. Here, ER beta ligand treatment was protective in EAE in both sexes and across genetic backgrounds. Neuroprotection was shown in spinal cord, sparing myelin and axons, and in brain, sparing neurons and synapses. Longitudinal in vivo MRIs showed decreased brain atrophy in cerebral cortex gray matter and cerebellum during EAE. Investigation of ER beta ligand as a neuroprotective treatment for MS is warranted.

Gray matter atrophy has been shown to be a strong correlate to clinical disability in multiple sclerosis (MS) and its most commonly used animal model, experimental autoimmune encephalomyelitis (EAE). However, the relationship between gray mater atrophy and the spinal cord pathology often observed in EAE has never been established. Here EAE was induced in Thy1.1-YFP mice and their brains imaged using in vivo magnetic resonance imaging (MRI). The brains and spinal cords were subsequently optically cleared using Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging-compatible Tissue-hYdrogel (CLARITY). Axons were followed 5mm longitudinally in three dimensions in intact spinal cords revealing that 61% of the axons exhibited a mean of 22 axonal ovoids and 8% of the axons terminating in axonal end bulbs. In the cerebral cortex, we observed a decrease in the mean number of layer V pyramidal neurons and a decrease in the mean length of the apical dendrites of the remaining neurons, compared to healthy controls. MRI analysis demonstrated decreased cortical volumes in EAE. Cross-modality correlations revealed a direct relationship between cortical volume loss and axonal end bulb number in the spinal cord, but not ovoid number. This is the first report of the use of CLARITY in an animal model of disease and the first report of the use of both CLARITY and MRI.