Efficacy of stem cell therapy in animal models of intracerebral hemorrhage: an updated meta-analysis

Abstract Background Multiple studies have reported that stem cell therapy has beneficial effects in animal models of intracerebral hemorrhage (ICH). However, this finding remains inconclusive. This study was performed to systematically determine the effect size of stem cell therapy in ICH animal models by pooling and analyzing data from newly published studies. Methods A literature search identified studies of stem cells in animal models of ICH. We searched mainstream databases from inception to November, 2021. And pooled effect size of stem cells was determined for diversified neurobehavioral scales and structural endpoints using random effects models. Results The median quality score of 62 included studies was 5.32. Our results revealed an overall positive effect of stem cell therapy. More specifically, the SMD was − 2.27 for mNSS, − 2.14 for rotarod test, − 2.06 for MLPT, − 1.33 for cylinder test, − 1.95 for corner turn test, − 1.42 for tissue loss, and − 1.86 for brain water content. For mNSS, classifying comparisons by quality score showed significant differences in estimates of effect size (p = 0.013), and high-quality comparisons showed a better outcome (SMD = − 2.57) compared with low-quality comparisons (SMD = − 1.59). Besides, different delivery routes also showed a significant difference in the estimates of effect size for mNSS (p = 0.002), and the intraperitoneal route showed the best outcome (SMD = − 4.63). For tissue loss, the autologous blood-induced ICH model showed a better outcome (SMD = − 1.84) compared with the collagenase-induced ICH model (SMD = − 0.94, p = 0.035). Additionally, stem cell therapy initiated within 8 h post-ICH showed the greatest efficacy on tissue loss reduction, followed by initiated with 24 h post-ICH. Finally, stem cells with different sources and types showed similar beneficial effects for mNSS as well as tissue loss. Conclusions Our results suggested that stem cell therapy had remarkable benefits on ICH animals on both the functional and structural outcomes in animal models of ICH, with very large effect size. These findings support the utility of further studies to translate stem cells in the treatment of ICH in humans. Moreover, the results should be interpreted in the light of the limitations in experimental design and the methodological quality of the studies included in the meta-analysis.