Roles of spinal V3 interneurons: Roles in controlling movement in healthy and injured conditions.

Spinal V3 interneurons are glutamatergic neurons that are distributed among the dorsal, intermediate, and ventral spinal cord. They are involved in broad neural circuit connections in the central nervous system. Functionally, they play important roles in locomotion, such as the maintenance of robust and balanced gaits during walking. More importantly, after spinal cord injury, these neurons maintain their excitability and facilitate proprioceptive sensory transmission to motor neurons, which are crucial for the initiation of complex coordinated reciprocal and rhythmic activities that resemble locomotion. Thus, spinal V3 interneurons appear to be good candidates for the restoration of locomotion after spinal cord injury. Nevertheless, therapeutic strategies targeting spinal V3 interneurons for spinal cord injury are scarce. In this review, we summarize the functional roles of spinal V3 interneurons in locomotion across uninjured and injured states and come up with possible strategies targeting them to restore locomotor function after spinal cord injury. Currently, an increasing number of studies are dedicated to identifying spinal V3 interneurons and their roles in motor, sensory, and autonomic nervous system functions. However, there are still many unclear questions regarding the molecular and functional characteristics of V3 interneurons in the spinal cord, as well as their potential therapeutic effects after spinal cord injury. Future research should prioritize the in-depth characterization of this specific neuronal subpopulation based on its sensorimotor features to further enhance spinal cord repair and functional recovery.