Multiple sclerosis (MS) is an autoimmune, neurodegenerative disease with inflammation, demyelination,
axonal damage, glial activation and synaptic loss. There are relapses and permanent disabilities. Despite
success of treatments targeting cells in the immune system, there is an unmet need for treatments targeting cells
in central nervous system (CNS) to repair disabilities. Four observations provide rationale for a new approach to
neurodegeneration in MS: 1) MS patients are heterogenous in their disabilities, and distinct disabilities (walking,
vision, cognition, coordination) are served by different CNS regions, 2) Even in healthy brain, a given CNS cell
type differs in gene expression from one brain region to another, 3) Being female versus male impacts disability
worsening, and 4) Aging aligns with disability progression. Here, we will use a cell-specific, region-specific, and
sex-specific approach to discover optimal treatment targets for distinct disabilities in MS women and men.
Bedside to Bench to Bedside in MS: Clinical observations of sex differences are investigated at the
preclinical level then translated back to the clinic as trials designed for each sex. Preclinical use of female and
male mice with experimental autoimmune encephalomyelitis (EAE) entails in vivo MRI for region-specific
atrophy, neuropathology of each region, RNA-sequencing of distinct CNS cells in each region,
immunohistochemistry validation of top genes in highly differentially expressed pathways, cell-specific
conditional knockout (CKO) of target genes to reverse phenotype, and knockdown of target genes with
pharmacologic treatment to reverse phenotype. The effect of genetic (CKO vs WT) and/or pharmacologic
(treatment vs placebo) interventions on reversal of gene expression is determined in each sex. Human MS data
guide preclinical research at three checkpoints: i) MRI in females and males with MS revealing sex differences
in substructure atrophy prioritize regions in EAE with atrophy, ii) Single nuclei RNA-seq analyses in females and
males with MS revealing gene pathways of interest prioritize gene pathways in EAE, iii) immunohistochemistry
in females and males using MS postmortem tissues validate immunohistochemistry in EAE. Substitution of use
of female versus male mice (as above) with use of gonadectomized versus gonadally intact mice will reveal
activational effects of sex hormones. Use of Four Core Genotype mice will reveal sex chromosome effects versus
developmental hormone effects. Use of young versus old mice will reveal the effect of aging.
This R35 proposal will: 1) Extend our cell-specific and region-specific transcriptomics in astrocytes
and oligodendrocytes to microglia and neurons, with cell:cell interactions revealed in mice double-labelled to
show gene expression changes in two distinct cell types in the same region in the same mouse, and 2) Determine
if there are effects of sex and/or age on the most differentially expressed cell-specific and region-specific
pathways. In summary, this R35 proposal takes our research to the next level: Identifying sex by age interactions
in cell-specific and region-specific transcriptomics, neuropathology, and substructure atrophy on MRI.
