Relay strategies combined with axon regeneration: a promising approach to restore spinal cord injury

For decades, research on spinal cord injury (SCI) has focused on regenerating axons to restore function. However, this approach has had limited success, suggesting that axon regeneration alone is not enough. An alternative strategy involves neuronal relays, where new neurons are introduced to relay signals past the injury site. These relays can occur spontaneously or be introduced through cell-based implantations. These relays can be formed by host interneurons or grafted neurons. Grafted neurons, especially early-stage neurons or stem cells, can differentiate, extend axons, and improve functional recovery.

• 1
  Locomotor recovery after spinal cord injury can be mediated by remodeling of bulbospinal and propriospinal connections, where new propriospinal relay circuits bypass the lesion site.
• 2
  Grafting early-stage neurons or stem cells into the injured spinal cord can lead to the formation of electrophysiologically active relays across the lesion, with differentiated neurons extending axons and forming synapses with host neurons.
• 3
  Re-established disynaptic propriospinal projections can mediate dexterous finger movements in rhesus monkeys with complete corticospinal tract transection, indicating that relayed neuronal pathways can enable functional recovery in higher mammals.