Bidirectional regulatory effects of frequency-dependent splenic apex electrical stimulation on peripheral immune suppression and central neural repair after spinal cord injury

The regulatory network of the spleen, a densely innervated immune hub, undergoes pathological remodeling following spinal cord injury. Whether targeted electrical stimulation of the spleen at specific frequencies can reverse peripheral immune suppression or improve the central immune system remains unclear. The aim of this study was to elucidate the previously unexamined effects and differential regulatory mechanisms of transsplenic apex electrical stimulation (10, 50, and 100 Hz) on peripheral immune suppression and spinal cord homeostasis after spinal cord injury. A mouse model of T3 spinal cord injury was established and systematically evaluated through functional assessments, splenic/spinal cord transcriptome sequencing, weighted gene co-expression network analysis, Short Time-series Expression Miner analysis, and multiomics validation to investigate the frequency-dependent effects of stimulation. The effects of the electrical stimulation exhibited significant frequency dependence. Specifically, 100 Hz electrical stimulation effectively restored the impaired bacterial clearance capacity in the host ( P < 0.001), reversed the suppression of adaptive immune-related gene modules in the spleen, and shifted immune responses toward T helper 17 (Th17) cell-axis remodeling. This was accompanied by upregulation of the expression of key hub genes such as those encoding integrin alpha x, CC chemokine receptor 6, Fc receptor-like 5, leukocyte immunoglobulin-like receptor subfamily A member 5, and Th17 signature cytokines such as interleukin-17, interleukin-23, and transforming growth factor-beta. In the spinal cord, 100 Hz electrical stimulation suppressed pro-inflammatory pathways such as nuclear factor-kappa B and tumor necrosis factor-alpha while activating neurorepair pathways, such as glutamatergic synapses. In contrast, 10 Hz electrical stimulation failed to alleviate peripheral immune suppression and exacerbated splenic immunosuppression and central neuroinflammation. These findings demonstrate that electrical stimulation of the splenic apex exerts frequency-dependent, bidirectional modulatory effects, with 10 and 100 Hz eliciting contrasting neuroimmune responses. Specifically, 100 Hz electrical stimulation activates the splenic Th17 immune axis, offering a potential mechanism to reverse spinal cord injury-induced immunodeficiency and neurological damage. Identifying the stimulation frequency as a critical therapeutic variable provides a foundation for developing frequency-optimized integrated neuroimmunomodulatory strategies for the treatment of spinal cord injury.