Role of stem cells-based in facial nerve reanimation: A meta-analysis of histological and neurophysiological outcomes

BACKGROUND Treatments involving stem cell (SC) usage represent novel and potentially interesting alternatives in facial nerve reanimation. Current literature includes the use of SC in animal model studies to promote graft survival by enhancing nerve fiber growth, spreading, myelinization, in addition to limiting fibrotic degeneration after surgery. However, the effectiveness of the clinical use of SC in facial nerve reanimation has not been clarified yet. AIM To investigate the histological, neurophysiological, and functional outcomes in facial reanimation using SC, compared to autograft. METHODS Our study is a systematic review of the literature, consistently conducted according to the preferred reporting items for systematic reviews and meta-analyses statement guidelines. The review question was: In facial nerve reanimation on rats, has the use of stem cells revealed as effective when compared to autograft, in terms of histological, neurophysiological, and functional outcomes? Random-effect meta-analysis was conducted on histological and neurophysiological data from the included comparative studies. RESULTS After screening 148 manuscript, five papers were included in our study. 43 subjects were included in the SC group, while 40 in the autograft group. The meta-analysis showed no significative differences between the two groups in terms of myelin thickness [CI: -0.10 (-0.20, 0.00); I 2 = 29%; P= 0.06], nerve fibers diameter [CI: 0.72 (-0.93, 3.36); I 2 = 72%; P= 0.6], compound muscle action potential amplitude [CI: 1.59 (0.59, 3.77); I 2 = 89%; P= 0.15] and latency [CI: 0.66 (-1.01, 2.32); I 2 = 67%; P= 0.44]. The mean axonal diameter was higher in the autograft group [CI: 0.94 (0.60, 1.27); I 2 = 0%; P≤ 0.001]. CONCLUSION The role of stem cells in facial reanimation is still relatively poorly studied, in animal models, and available results should not discourage their use in future studies on human subjects.