There are differences between females and males in terms of susceptibility to multiple sclerosis (MS), MS activity and MS prognosis, with a certain paradox, females being more susceptible to develop the disease, but having a better long term prognosis. These differences could be related to variations in sex hormones levels. The most striking evidence comes from pregnancy data, where the increase in sex hormones impregnation is accompanied by a dramatic decrease in the risk of relapses, whereas the post-partum decrease in hormones leads to a rebound of MS activity. In the presentation, we will go through the different states in women’s life, considering natural and therapeutic hormonal changes and their relation to MS susceptibility, activity and prognosis, from a clinical and epidemiological standpoint.
Sex differences in MS susceptibility entail women having MS at a rate two to three fold higher than in men. Other autoimmune diseases also show a female preponderance. Sex differences can be due to sex hormones or sex chromosomes or both. Here, we will focus on the role of sex chromosomes. Most Y genes have been lost over evolution with conservation primarily of genes critical for reproduction, while in contrast many X genes are expressed in the immune system or brain. Thus, we focused on the X chromosome. Sex differences in disease susceptibility can be caused an X-dosage effect of X genes that escape X-inactivation or differences in parental imprinting of X genes that do not escape X-inactivation.
Investigate two possible X chromosome gene effects on CD4+ T lymphocytes: 1) an X-dosage effect of X genes that escape X-inactivation and 2) differences in parental imprinting of X genes that do not escape X-inactivation.
Selective deletion of X chromosome genes in CD4+ T lymphocytes, genome-wide transcriptome studies in CD4+ T lymphocytes to determine loss of function effects during selective gene deletion, methylome studies to determine parental imprinting effects.
Regarding X dosage, we found that Kdm6a, a histone demethylase gene that escapes X-inactivation, is expressed higher in CD4+ T lymphocytes of females (XX) than males (XY) in both mice and humans. Selective deletion of Kdm6a from CD4+ T lymphocytes reduced EAE clinical scores and CNS inflammation. The transcriptome of selective Kdm6a knock outs showed decreased neuroinflammatory pathway signaling. Together this demonstrated that Kdm6a expressed at increased dosage in females mediates increased neuroinflammation through Kdm6a’s effect on genome-wide methylation. Regarding parental imprinting of genes that do not escape X-inactivation, we showed that the XY genotype compared to XX, had increased expression of X genes in CD4+ T lymphocytes. Methylation studies revealed that the paternal X chromosome was more methylated than the maternal X chromosome and that paternal X genes had less expression than maternal X genes. Since all cells in males have their X chromosome of maternal origin (XmY), while in females half are of maternal or paternal origin (XmXp), sex differences in parental imprinting explain how X genes that do not escape X-inactivation are expressed less in females than males.
Both an X-dosage effect of X genes that escape X-inactivation and a parental imprinting effect on X genes that undergo X-inactivation occur in CD4+ T lymphocytes to underlie sex differences in autoimmunity.
Historically, disease activity diminished during pregnancy in women with relapsing-remitting MS. Today, women with high disease activity are more likely to attempt pregnancy due to the disease control that new therapies offer. But disease activity during pregnancy in the modern day remains understudied.
Describe disease activity in a modern pregnancy cohort, grouped by preconception disease-modifying therapy (DMT) class; determine the predictors of relapse during pregnancy.
Data were obtained from the MSBase Registry. Term/preterm pregnancies conceived from 2011-2019 were included. DMT were classed by low, moderate and high-efficacy. Annualized relapse rates (ARR) were calculated for each pregnancy trimester and 12 months either side. Predictors of relapse during pregnancy were determined using clustered logistic regression.
We included 1640 pregnancies from 1452 women. DMT used in the year before conception were none (n=346), low (n=845), moderate (n=207) and high-efficacy (n=242). Most common DMT in each class was interferon-beta (n=597), fingolimod (n=147) and natalizumab (n=219) for low, moderate and high-efficacy respectively. Conception EDSS ≥2 was more common in higher efficacy DMT groups (high: 41.3%; moderate 28.5%; low 22.4%; none 20.2%). For low-efficacy and no DMT groups, ARR fell through pregnancy. ARR of the moderate-efficacy group increased in the 1st pregnancy trimester (0.55 [95% CI 0.36-0.80] vs 0.14 [95% CI 0.10-0.21] on low-efficacy), then decreased to a trough in the third. Conversely, ARR steadily increased throughout pregnancy for those on high-efficacy DMT (3rd trimester: 0.42 [95% CI 0.25-0.66] vs 0.12 [95% CI 0.07-0.19] on low-efficacy). Higher efficacy DMT groups were associated with higher ARR in the early postpartum period (high: 0.84 [95% CI 0.62-1.1]; moderate: 0.90 [95% CI 0.65-1.2]; low: 0.47 [95% CI 0.38-0.58]). Preconception use of high and moderate-efficacy DMT and higher preconception ARR were predictors of relapse in pregnancy. But, continuation of high-efficacy DMT into pregnancy was protective against relapse (odds ratio 0.80 [95% CI 0.68-0.94]). Age ≥35 years was associated with reduced odds of relapse.
Women with RRMS treated with moderate or high-efficacy DMT are at greater risk of relapse during pregnancy. Careful pregnancy management, and use of long-acting high-efficacy DMT preconception, or continuing natalizumab into pregnancy, may prevent relapse in pregnancy.
Multiple sclerosis (MS) is three times more common in women, yet more severe in men, but the mechanisms underlying these sex differences remain mostly unknown. While MS is initiated by autoreactive T helper cells, CNS-infiltrating inflammatory myeloid cells are the proximal effector cells driving disease pathology. The role of CNS-resident myeloid cells, such as microglia, is less clear.
We have previously shown that genetic ablation of p38α MAP kinase (p38) using LysM-Cre broadly in the myeloid lineage is protective in the autoimmune model of MS, experimental autoimmune encephalomyelitis (EAE). Strikingly, this protection was seen in female mice and not males. Here, we sought to precisely define the mechanisms responsible.
We used multiple genetic approaches and bone marrow chimeras to ablate p38 in microglial cells, peripheral myeloid cells, or both, to study the effect on disease outcomes in EAE. Single cell and bulk transcriptional profiling, as well as flow cytometry, were used to identify molecular phenotypes of microglia.
Deletion of p38 in both peripheral myeloid cells and microglia using Cx3cr1-Cre recapitulated the previous sex difference, with reduced EAE severity in females. Unexpectedly, Cx3cr1-Cre mediated deletion of p38 restricted to the bone marrow-derived peripheral compartment was protective in both sexes. However, deletion of p38 in microglia using inducible Cx3cr1-ER-Cre exacerbated EAE in males only, revealing opposing roles of p38 in microglia vs. peripheral myeloid cells. Single cell transcriptional profiling of microglia isolated from the inflamed CNS recapitulated recently described microglial diversity, identifying 8 distinct transcriptional states during acute EAE. Deletion of p38 resulted in enhanced transition from homeostatic to disease-associated microglial states, through the loss of expression of homeostatic genes such as Atf3, Rgs1, Btg2, and Neat1, with increased expression of disease-associated genes such as Cd74, Ccl5, and Spp1.
These results reveal the presence of a p38-dependent sex-specific molecular pathway in microglia that is protective in CNS autoimmunity through the regulation of microglial transcriptional states. Further, our findings suggest that autoimmunity in males and females may be driven by distinct cellular and molecular pathways, thus informing the design of novel future sex-specific therapeutic approaches.