The Effect of Bone Marrow–Derived Mesenchymal Stem Cell Transplantation on Allodynia and Hyperalgesia in Neuropathic Animals: A Systematic Review with Meta-Analysis

• Neuropathic pain is 1 of the most complicated pain conditions to diagnosis and treat.
• Current treatment strategies are efficient in less than 50% of the patients.
• Stem cell therapy is considered a therapeutic method for neuropathic pain.
• We found bone marrow mesenchymal stem cell transplantation improves allodynia.
• Bone marrow mesenchymal stem cell transplantation improves hyperalgesia if it is given during the first 4 days after injury.

Stem cell transplantation has been considered a possible therapeutic method for neuropathic pain. However, no quantitative data synthesis of stem cell therapy for neuropathic pain exists. Therefore, the present systematic review and meta-analysis assessed the efficacy of bone marrow mesenchymal stem cell (BMMSC) transplantation on alleviating pain symptoms in animal models of neuropathic pain. In the present meta-analysis, controlled animal studies assessing the effect of administrating BMMSC on neuropathic pain were included through an extensive literature search of online databases. After collecting data, effect sizes were computed and the standardized mean difference (SMD) with 95% confidence interval (CI) was entered in all analyses. Random-effects models were used for data analysis. Sensitivity and subgroup analyses were performed to investigate expected or measured heterogeneity. Finally, 14 study were included. The analyses showed that BMMSC transplantation lead to significant improvement on allodynia (SMD = 2.06; 95% CI, 1.09 to 3.03; I2 = 99.7%; P < .001). The type of neuropathy (P = .036), time between injury and intervention (P = .02), and the number of transplanted cells (P = .023) influence the improvement of allodynia after BMMSC transplantation. BMMSC transplantation has no effect on hyperalgesia (SMD = .3; 95% CI, −1.09 to 1.68; I2 = 100%; P < .001) unless it occurs during the first 4 days after injury (P = .02). The present systematic review with meta-analysis suggests that BMMSC transplantation improves allodynia but does not have any significant effect on hyperalgesia unless it is given during the first 4 days after injury.