Repetitive Trans-spinal magnetic stimulation Promotes Repair in Inflammatory Spinal Cord Injury Through Sex-Dependent Immune Modulation

Abstract

Spinal cord injuries (SCI), whether traumatic or inflammatory such as transverse myelitis (TM), are characterized by severe neuroinflammation, demyelination, and long-term disabilities. Current treatments remain limited, highlighting the need for novel non-invasive therapeutic approaches. Repetitive magnetic stimulation (RMS) has emerged as a promising strategy, but its mechanisms and efficacy in inflammatory contexts remain poorly described. Here, we investigated the effects of RMS applied as trans-spinal RMS (rTSMS) in a mouse model of focal spinal cord demyelination induced by lysophosphatidylcholine (LPC). When applied one day after LPC injection, rTSMS reduced inflammation, demyelination, and fibroglial scar formation, while promoting early locomotor recovery in both sexes. In contrast, when treatment was initiated three days after LPC injection, corresponding to the peak of motor deficits, rTSMS conferred tissue protection and functional benefits only in female mice. RNA sequencing analyses revealed sex-dependent immune modulation: in females, rTSMS primarily regulated adaptive T cell-related pathways, whereas in males, it mainly targeted innate immune responses such as neutrophil activity and phagocytosis. Complementary in vitro experiments using microglial and macrophage cultures further demonstrated that RMS modulates transcriptomic responses differently depending on cell type and inflammatory state. Specifically, RMS attenuated IL-1-induced pro-inflammatory signaling in macrophages and completely abolished these effects in microglia. Altogether, our findings establish rTSMS as a non-invasive therapy capable of reducing neuroinflammation and demyelination in inflammatory SCI, with pronounced sex-dependent effects. By uncovering distinct immune pathways engaged in male and female mice, this study provides mechanistic insights into rTSMS action and opens perspectives for its translational use in neuroinflammatory diseases.