Stem cell-derived exosomes for traumatic spinal cord injury: a systematic review and network meta-analysis based on a rat model

Background aims Exosome therapy for traumatic spinal cord injury (TSCI) is a current research hotspot, but its therapeutic effect and the best source of stem cells for exosomes are unclear. Methods The Web of Science, PubMed, Embase, Cochrane, and Scopus databases were searched from inception to March 28, 2023. Literature screening, data extraction and risk of bias assessment were performed independently by two investigators. Results A total of 40 studies were included for data analysis. The findings of our traditional meta-analysis indicate that exosomes derived from stem cells significantly improve the motor function of TSCI at various time points (1 week: weighted mean difference [WMD] = 1.58, 95% confidence interval [CI] 0.87–2.30] 2 weeks: WMD = 3.12, 95% CI 2.64–3.61; 3 weeks: WMD = 4.44, 95% CI 3.27–5.60; 4 weeks: WMD = 4.54, 95% CI 3.42–5.66). Four kinds of stem cell–derived exosomes have been studied: bone marrow mesenchymal stem cells, adipose mesenchymal stem cells, umbilical cord mesenchymal stem cells and neural stem cells. The results of the network meta-analysis showed that there was no significant statistical difference in the therapeutic effect among the exosomes derived from four kinds of stem cells at different treatment time points. Although exosomes derived from bone marrow mesenchymal stem cells are the current research focus, exosomes derived from neural stem cells have the most therapeutic potential and should become the focus of future attention. Conclusions The exosomes derived from stem cells can significantly improve the motor function of TSCI rats, and the exosomes derived from neural stem cells have the most therapeutic potential. However, the lower evidence quality of animal studies limits the reliability of experimental results, emphasizing the need for more high-quality, direct comparative studies to explore the therapeutic efficacy of exosomes and the best source of stem cells.