Current state of stem cell-mediated therapies for facial nerve injury

Purpose of review Interest in the application of stem cell therapy to nerve injury has grown exponentially in recent years, as the armamentarium of potential stem cell sources has increased. This article reviews literature on the recent developments in the application of stem cell therapy for facial nerve injury. Recent findings Current stem cell therapy for the treatment of peripheral nerve injury can be generalized into those that either enhance native neural regeneration via an anti-inflammatory effect or growth factor secretion, replace Schwann cells, or replace motor neurons. Animal studies have shown that nerve conduits seeded with stem cells (either undifferentiated or differentiated into Schwann-like cells) in sciatic and facial nerve injury models can promote nerve regeneration with similar efficacy to autologous nerve autografts. In-vivo studies have also shown that induced pluripotent stem cell-derived motor neurons, when transplanted into transected mouse tibial nerves, can form functional neuromuscular junctions with the denervated mouse triceps surae. Summary The authors believe that induced pluripotent stem cells have significant therapeutic potential. This source of human stem cells can be harvested with little morbidity, is isogenic to the donor, and has fewer ethical concerns compared with embryonic cellular sources. Further research is required to determine stem cell efficacy and safety. Questions of stem cell fate unpredictability and possible tumorigenesis must be addressed prior to human trials.