THE EFFECT OF ANTIBIOTIC-INDUCED DYSBIOSIS ON PERIPHERAL NERVE REPAIR

Human gut microbiota is the dynamic and complex population of microorganisms (bacteria, fungi, protozoa and viruses), which contributes to tissue homeostasis through a series of physiological functions. The gut microbiota influences not only the gastrointestinal tract, but also a growing list of other organs, impacting on function such as barrier integrity, metabolism, hematopoiesis and inflammation, leading to its consideration as a ‘vital organ’. Recently, our laboratory identified a connection between the gut microbiota and the peripheral nervous system (PNS). To study the impact of microbiota composition on peripheral nerve regeneration, we administered a cocktail of antibiotics (vancomycin 0.25 mg/mL, ampicillin 0.5 mg/mL, metronidazole 0.5 mg/mL) to mice via drinking water. Animals were divided into four groups: Group 1 (Treated with antibiotics before and after the surgery), Group 2 (Treated with antibiotics before the surgery), Group 3 (Treated with antibiotics after the surgery) and Group 4 (Not treated with antibiotics). Mice were subjected to peripheral nerve injury (transection or crush) and, after 2, 7 or 28 days different tissues/organs were harvested for the analysis: median and ulnar nerve, flexor digitorum superficialis and flexor digitorum profundus, spleen, lymphnodes, serum, fecal pellet, DRGs, and forepaw. To assess functional recovery, we performed the grasping test. Antibiotic treatment did not cause weight loss or evident behavioral alterations. Microbiota analysis revealed distinct patterns across groups/treatments and timepoints. Overall, antibiotic treatment induced dysbiosis, with the extent and nature of the disruption varying according to treatment duration. The rescue group (treated only before surgery) demonstrated partial recovery of the microbiota, particularly at later timepoints. The grasping test revealed that mice treated 10 days before median nerve injury showed reduced strength in the injured forelimb compared to untreated animals until day 10 post-injury. This difference progressively diminished, with similar performance among groups by day 28. Additional analyses are ongoing. Our findings indicate that microbiota depletion leads to functional alterations in the PNS. Further analyses are ongoing to elucidate mechanisms underlying these effects.