Fidelity of Sensory Reinnervation in Peroneal and Sural Nerves to Lumbar Dorsal Root Ganglia 4 and 5 After Segmental Injury to the Sciatic Nerve

TL;DR

This study examines how sensory nerves regenerate after injury, finding that mixed nerves regenerate more faithfully than sensory-only nerves.

Contribution

The study introduces a novel assessment of sensory axon regeneration fidelity after sciatic nerve injury using retrograde labeling.

Findings

Sensory axon regeneration fidelity was higher in the peroneal nerve compared to the sural nerve.

Fidelity of regeneration varied by graft type and nerve branch.

Anatomically matching branched grafts may improve regeneration of segmental nerve injuries.

Abstract

Recovery after axotomy of a peripheral nerve is dependent on regrowth of axons from the point of injury to distal sensorimotor tissues and can be complicated by nerve branching. Little is known about regeneration of sensory axons that encounter branch points distal to injuries. The experiments reported here focused on this question and sought to assess the fidelity of sensory axon regeneration, where fidelity is defined as an axon that originally innervated a distal branch of the sciatic nerve regenerated into that same distal branch after injury, with serial retrograde labeling. Rats with segmental sciatic nerve injuries were treated with linear or branched grafts, with retrograde labels injected into the peroneal and sural branches of the sciatic nerve prior to injury and 12 weeks after. Lumbar dorsal root ganglia 4 and 5 were collected after 12 weeks and were imaged to determine the fidelity of sensory axon regeneration. Results show that the fidelity of sensory regeneration into these two branches differed by the branch and the graft type. Interestingly, the fidelity of sensory axon reinnervation was greater into the peroneal nerve, which is a mixed sensorimotor nerve, compared to the sural nerve, which is a sensory nerve. This occurred in both graft types and suggests that the fidelity of sensory regeneration is improved into mixed branches distal to the PNI compared to sensory branches and supports why regeneration of segmental branched defects may be superior using anatomically matching branched grafts.

Fidelity of sensory axon reinnervation was greater into the peroneal nerve, which is a mixed sensorimotor nerve, compared to the sural nerve, which is a sensory nerve. This finding suggests sensory regeneration of segmental branched defects may be improved using anatomically matching branched grafts.

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