Axonal sprouting from adjacent dorsal root ganglia following cervical dorsal root avulsion in mice

Brachial plexus injury is a neurological injury caused by trauma, and effective treatments remain limited. Understanding its pathology is necessary to develop new therapeutic strategies. In this study, we used a dorsal root avulsion mouse model to determine whether injury-induced alterations in feedback circuitry from the dorsal root ganglion (DRG) to motor neurons contribute to functional recovery. We visualized axons originating from DRG neurons by directly injecting adeno-associated virus encoding green fluorescent protein (AAV-GFP) into the DRG adjacent to the injury site and analyzed the total length of axons on the lateral side of the ventral horn in the spinal cord. Following injury, the fine motor function of the affected forepaw was immediately impaired and then gradually recovered. In parallel, axons originating from an adjacent, uninjured DRG extended into the deafferented spinal segments, possibly contributing to the reinnervation of motor neurons that had lost their original sensory input. Indeed, after spontaneous motor recovery, when we performed an additional dorsal root avulsion originating from the adjacent DRG, functional impairment of the forepaw re-emerged. Our results demonstrate that the plasticity of the adjacent DRG may facilitate the recovery of fine motor function after dorsal root injury.