Abstract
There are considerable disagreements on the application of olfactory ensheathing cells (OEC) for spinal cord injury (SCI) rehabilitation. The present meta-analysis was designed to investigate the efficacy of OEC transplantation on motor function recovery and neuropathic pain alleviation in SCI animal models. Accordingly, all related studies were identified and included. Two independent researchers assessed the quality of the articles and summarized them by calculating standardized mean differences (SMD). OEC transplantation was shown to significantly improve functional recovery (SMD = 1.36; 95% confidence interval: 1.05–1.68; p < 0.001). The efficacy of this method was higher in thoracic injuries (SMD = 1.41; 95% confidence interval: 1.08–1.74; p < 0.001) and allogeneic transplants (SMD = 1.53; 95% confidence interval: 1.15–1.90; p < 0.001). OEC transplantation had no considerable effects on the improvement of hyperalgesia (SMD = −0.095; 95% confidence interval: −0.42–0.23; p = 0.57) but when the analyses were limited to studies with follow-up ≥8 weeks, it was associated with increased hyperalgesia (SMD = −0.66; 95% confidence interval: −1.28–0.04; p = 0.04). OEC transplantation did not affect SCI-induced allodynia (SMD = 0.54; 95% confidence interval: −0.80–1.87; p = 0.43). Our findings showed that OEC transplantation can significantly improve motor function post-SCI, but it has no effect on allodynia and might lead to relative aggravation of hyperalgesia.
Highlights
Spinal cord injury (SCI) is among the most important causes of mortality and disability in the young, with a reported global prevalence of 236 to 4178 cases per one million people, to which 180,000 cases are added every year[1]
Our findings showed that Olfactory ensheathing cells (OEC) transplantation can significantly improve motor function post-SCI, but it has no effect on allodynia and might lead to relative aggravation of hyperalgesia
The results showed that OEC transplantation significantly improved functional recovery (Pooled standardized mean differences (SMD) = 1.36; 95% confidence interval: 1.05–1.68; p < 0.001; I2 = 74.80%)
Summary
Spinal cord injury (SCI) is among the most important causes of mortality and disability in the young, with a reported global prevalence of 236 to 4178 cases per one million people, to which 180,000 cases are added every year[1]. Olfactory ensheathing cells (OEC) are viable candidates for cell therapy which can improve neuropathic pain and motor function in patients with SCI through multiple mechanisms including phagocytosis of axonal debris, immunoprotective characteristics that help axonal recovery, migration towards glial scars, and secretion of neutrotrophic factors[12] Their efficacy has been questioned by multiple surveys[13,14,15,16] and their association with aggravation of allodynia and hyperalgesia has limited application of this method[17,18]. Their study suffered publication bias and their applied keywords were not able to yield the maximum number of articles[22] In another meta-analysis conducted in 2016, OEC transplantation was shown to improve motor function of the animals with spinal cord injuries[23], but the sensory status after transplantation was not evaluated in their study. The present systematic review and meta-analysis was designed to investigate the efficacy of this treatment along with the effects of different treatment protocols applied
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