Conditioned Medium Treatment for the Improvement of Functional Recovery after Spinal Cord Injury: A Meta-Analysis Study

Background: While there is no certain treatment for spinal cord injury (SCI), stem cell-based therapy may be an attractive alternative, but the survival and differentiation of cells in the host tissue are poor. Conditioned medium (CM) has several beneficial effects on cells. Objective: In this meta-analysis study, we examined the effect of CM on SCI treatment. Methods: After searching on MEDLINE, SCOPUS, EMBASE, and Web of Science, first and secondary screening were performed based on title, abstract, and full text. The data were extracted from the included studies, and meta-analysis was performed using STATA.14 software. A standardized mean difference (SMD) with a 95% confidence interval was used to report findings. Quality control and subgroup analysis were also performed. Results: The results from 52 articles and 61 separate experiments showed that CM had a significantly strong effect on improving motor function after SCI (SMD = 2.58; 95% CI: 2.17 to 2.98; p < 0.001) and also analysis of data from 12 articles demonstrated that CM reduced the expression of GFAP marker (SMD = -4.16; p < 0.0001) compared to SCI group without any treatment. Subgroup analysis showed that treatment with CM of neural stem cells was better than CM of mesenchymal stem cells. It was more effective after a mild lesion than a moderate or severe one. The improvement was more pronounced with <4 weeks than >4 weeks follow-up. Conclusion: CM had a significant effect in improving motor function after SCI, especially in cases of mild lesions. It has been observed that if CM originates from the neural stem cells, it has a more significant effect than mesenchymal cells.