The Role of the Gut Microbiota in Functional Recovery after Peripheral Nerve Injury: A Narrative Review.

Introduction: While researchers have previously pointed to the peripheral nervous system as a method of transportation for the gut microbiota metabolites to distant organs, researchers have more recently studied the impact of gut microbiota on the peripheral nerves. The purpose of this review was to synthesize the literature on how modulation of the gut microbiota impacts functional recovery following peripheral nerve injury. Methods: Electronic searches were conducted in Ovid/Medline and PubMed to identify articles that discuss gut microbiome interventions following peripheral nerve injury in sciatic nerve chronic constriction injury or crush injury animal models and the effects on peripheral nerve regeneration and functional recovery. Results: Twelve articles met inclusion criteria; all were prospective studies in animal models. Four interventions were identified by the twelve studies, including probiotics, antibiotics, intermittent fasting, and naturopathic compounds. Probiotic treatment and dietary interventions targeted at modulating the gut microbiota improved histological, sensory, and motor outcomes following peripheral nerve injury. While antibiotic treatment negatively impacted recovery after peripheral nerve injury, co-treatment with probiotics or reconstitution of the gut microbiota through fecal microbiota transplantation was able to rescue these negative effects. Conclusion: Alterations in the gut microbiota, whether induced by antibiotics, probiotics, intermittent fasting, or dietary interventions, impact functional recovery, neuropathic pain, and inflammatory processes. However, future research should focus on identifying the specific microbial taxa responsible for neuroregenerative effects and developing standardized protocols for probiotic treatment to optimize improvement in peripheral nerve recovery after injury.