Exosomes Derived from Tanshinone IIA-Pretreated Umbilical Cord Mesenchymal Stem Cells Repair Traumatic Spinal Cord Injury by miR-223–5p/USP8/NLRP3 Axis

Spinal cord injury (SCI) lacks effective therapies, and umbilical cord mesenchymal stem cell (UCMSC)-derived exosomes show promise but require efficacy optimization. This study explored tanshinone IIA (TSA)-pretreated UCMSC exosomes (T-Exos) to enhance neuroprotection and functional recovery post-SCI. T-Exos were isolated from the TSA-treated UCMSCs. SCI mice received T-Exos, with motor function assessed behaviorally. In vitro and in vivo, microglial NLRP3 inflammasome activity, polarization (M1/M2), and cytokine release were analyzed. miRNA profiling identified key miRNAs in T-Exos; miR-223-5p's role was validated via inhibition. Mechanistic studies linked miR-223-5p to USP8/NLRP3 using Western blot, qPCR, and co-IP assays. T-Exos improved motor recovery in SCI mice by suppressing NLRP3 inflammasome activation, shifting microglia to anti-inflammatory M2 phenotypes, reducing the level of IL-1β/IL-18, and alleviating oxidative stress. miR-223-5p was highly enriched in T-Exos, and its inhibition reversed therapeutic effects. Mechanistically, miR-223-5p targeted USP8, a deubiquitinase stabilizing NLRP3. By inhibiting USP8, T-Exos reduced NLRP3 levels, dampening neuroinflammation. TSA pretreatment enhances exosomal miR-223-5p, which blocks USP8-mediated NLRP3 stabilization, driving microglial M2 polarization and neuroprotection. These findings highlight T-Exos as a targeted therapy for SCI, offering insights into the exosome-mediated modulation of inflammatory microenvironments for neural repair.