eLife, 2021 · DOI: https://doi.org/10.7554/eLife.70058 · Published: December 2, 2021
This study investigates the role of long ascending propriospinal neurons (LAPNs) in locomotor recovery after spinal cord injury (SCI) in rats. LAPNs are spinal cord interneurons that connect the lumbar and cervical enlargements, and they are thought to play a role in coordinating limb movements during locomotion. The researchers conditionally silenced LAPNs after SCI and found that, contrary to their hypothesis, silencing LAPNs improved locomotor function. This included better paw placement order and timing, fewer dorsal steps, restored left-right hindlimb coordination, and normalized gait spatiotemporal features. These unexpected findings suggest that spared LAPNs post-SCI may interfere with hindlimb stepping and that silencing them may remove excess 'noise' within the locomotor system, allowing intrinsic lumbar circuitry to function independently.
These findings have implications for the development of neuronal- and axonal-protective therapeutic strategies, suggesting that anatomical sparing may not always result in expected benefits.
The results may influence the clinical study and implementation of neuromodulation strategies, such as epidural stimulation, by considering the potential maladaptive roles of spared pathways like LAPNs.
The study contributes to a better understanding of the complex mechanisms underlying locomotor recovery after SCI, highlighting the potential for spared neural circuits to have detrimental effects on function.