Changes in intracellular nicotinamide adenine dinucleotide (NAD⁺) levels have been observed in various disease states. A decrease in NAD⁺ levels has been noted following spinal cord injury (SCI). Nicotinamide riboside (NR) serves as the precursor of NAD⁺. Previous research has demonstrated the anti-inflammatory and apoptosis-reducing effects of NR supplements. However, it remains unclear whether NR exerts a similar role in mice after SCI. The objective of this study was to investigate the impact of NR on these changes in a mouse model of SCI. Four groups were considered: (1) non-SCI without NR (Sham), (2) non-SCI with NR (Sham +NR), (3) SCI without NR (SCI), and (4) SCI with NR (SCI + NR). Female C57BL/6J mice aged 6–8 weeks were intraperitoneally administered with 500 mg/kg/day NR for a duration of one week. The supplementation of NR resulted in a significant elevation of NAD⁺ levels in the spinal cord tissue of mice after SCI. In comparison to the SCI group, NR supplementation exhibited regulatory effects on the chemotaxis/recruitment of leukocytes, leading to reduced levels of inflammatory factors such as IL-1β, TNF-α, and IL-22 in the injured area. Moreover, NR supplementation notably enhanced the survival of neurons and synapses within the injured area, ultimately resulting in improved motor functions after SCI. Therefore, our research findings demonstrated that NR supplementation had inhibitory effects on leukocyte chemotaxis, anti-inflammatory effects, and could significantly improve the immune micro-environment after SCI, thereby promoting neuronal survival and ultimately enhancing the recovery of motor functions after SCI. NR supplementation showed promise as a potential clinical treatment strategy for SCI.

Traumatic spinal cord injury (SCI) is a common disabling condition characterized by a disrupted immune microenvironment that significantly hinders neural regeneration. In recent years, CD3⁺CD4^-CD8^- double-negative T cells (DNT cells) have garnered considerable attention due to their multifaceted roles in immune regulation. Flow cytometry data indicate a significant increase in the proportion of DNT cells following SCI. Single-cell sequencing further demonstrates the heterogeneity of DNT cells, with CD3⁺TCRαβ⁺CD4^-CD8^-NK1.1^- T cells (DNTαβ) potentially playing an immune regulatory role. Accordingly, we hypothesize that the transplantation of DNTαβ cells could improve the immune microenvironment in the spinal cord. To test this hypothesis, we obtained DNTαβ cells for SCI treatment through flow cytometric sorting. Behavioral assessments indicated that both in situ injection and tail vein injection of DNTαβ cells significantly promoted the recovery of motor function in mice with SCI. Immunohistochemical analysis further revealed that DNTαβ cells can inhibit glial proliferation and promote neuronal survival and myelination. Transcriptomic sequencing data also supported the role of DNTαβ cell transplantation in modulating immune responses through the Gzmb and IFN pathways, to promote early repair and neuroprotection following SCI. Our findings suggest that exogenous supplementation of DNTαβ cells can regulate the immune microenvironment to enhance neural regeneration after SCI, providing new therapeutic strategies and data support for cellular therapies following SCI.