Sex-Related Differences in Circular RNA Expression in Multiple Sclerosis: A Pilot Study

Multiple Sclerosis (MS) is an inflammatory autoimmune disease of the central nervous system (CNS), with a female-to-male ratio of up to 3:1. Sex differences in immune responses and neurodegeneration influence disease susceptibility and progression. Circular RNAs (circRNAs) are emerging regulators of CNS and immune cell functions; however, the mechanisms underlying their regulation and dysregulation in MS remain poorly understood. Given the relevant role of sex-related differences in MS, in this pilot study we re-analyzed a previously published dataset by performing a sex-stratified analysis. Specifically, we focused on identifying circRNAs that are differentially expressed in female MS patients compared to male MS patients. We identified 33 differentially expressed circRNAs in peripheral blood mononuclear cells: 27 were more expressed and 6 were less expressed in female MS patients as compared to male MS patients. The discovery dataset was validated in an independent cohort of 8 female and 8 male relapsing-remitting (RR) MS patients confirming sex-dependent differences in the expression of five circRNAs. Among these, hsa_circ_0140253 was significantly elevated, while hsa_circ_0029426, hsa_circ_0005354, and hsa_circ_0002082 were significantly reduced. Notably, hsa_circ_0140253 expression was markedly increased in patients with a higher level of disability and in progressive forms of MS, and across various disease-modifying therapies used in MS treatment. This exploratory study provides preliminary evidence of sex-related differences in circRNA expression in MS and their association with disease severity and DMT exposure. Our findings suggest that circRNA expression is influenced by multiple factors, underscoring the importance of considering sex and clinical variables in future studies. Further validation in larger cohorts is needed to confirm these observations and clarify the role of circRNAs in MS pathogenesis.Graphical AbstractA sex-stratified analysis of PBMC samples from multiple sclerosis (MS) patients identifies distinct circRNA expression patterns between females and males. Sex-related circRNA differences are associated with disease severity and exposure to disease-modifying therapies. We identified 33 circRNAs differentially expressed between female and male MS patients, highlighting the increased levels in female of hsa_circ_0140253 and the reduction of hsa_circ_0029426, hsa_circ_0005354, and hsa_circ_0002082. These preliminary findings support the need for larger, sex-stratified and functional studies to better define the contribution of circRNAs to MS pathogenesis.