Advancing Peripheral Nerve Graft Transplantation for Incomplete Spinal Cord Injury Repair

Frontiers in Cellular Neuroscience, 2022 · DOI: 10.3389/fncel.2022.885245 · Published: April 28, 2022

Spinal Cord Injury Regenerative Medicine

Simple Explanation

Peripheral nerves possess the ability to regrow axons, unlike the central nervous system. Transplanting a section of peripheral nerve into the spinal cord can encourage CNS axons to grow across injury sites. This method offers a way to bridge long distances in incomplete spinal cord injuries, potentially restoring long neural pathways. After an incomplete SCI, shorter sprouting, plasticity and compensation occurs in propriospinal and supraspinal circuitry. New intraspinal relay circuits provide spontaneous recovery and spared axons may sprout new collaterals connecting to adjacent circuitry. Peripheral nerve grafts (PNGs) promote axon growth in the central nervous system by acting as a bridge to bypass damaged long tracts. They provide myelination and can be surgically directed toward specific sites of the spinal cord.

Study Duration

Not specified

Participants

Not specified

Evidence Level

Not specified

Key Findings

1
PNG transplantation has shown potential for improved recovery, even for incomplete injuries, due to its unique ability to bypass damaged long tracts, provide myelination, and be surgically directed toward specific sites in the spinal cord.
2
Spontaneous recovery after incomplete SCI is limited but can be enhanced through rehabilitation programs and electrical stimulation, which depend on intact long circuitry in the spinal cord.
3
Long circuitry reconstruction after SCI has only been achieved experimentally with PNG transplantation because CNS axons can grow great lengths in a peripheral nerve.

Research Summary

Peripheral nerve grafts (PNGs) have shown promise as a therapeutic treatment for spinal cord injuries (SCI), particularly incomplete injuries, by promoting axon regeneration and bridging damaged tracts. The review emphasizes the advantages of PNGs, including their ability to promote long-distance axon growth, provide myelination, and be surgically directed to specific sites in the spinal cord. Addressing conceptual questions and developing appropriate surgical techniques are crucial for advancing PNG implementation and maximizing its potential benefits for individuals with SCI.

Practical Implications

Surgical Planning

Surgeons can use functional data (neurophysiological evaluation in combination with MRI) to precisely determine the upper and lower level of an injury, enabling more targeted surgical interventions.

Therapeutic Development

The potential of PNGs combined with other therapies like growth-prone relay circuits derived from transplanted neural stem cells or electrical stimulation could enhance functional outcomes, especially in chronic SCI.

Clinical Translation

Implementing PNGs in the chronic state, when spontaneous recovery has ended and scarring has matured, would be more practical and reasonable, requiring careful assessment of the injury-outcome, potential benefits, and risks.

Study Limitations

1
The small injuries to the spinal cord associated to the transplantation may be considered a draw back and an unavoidable potential risk.
2
Several details regarding the new circuitry formation and function, outcome as a result of various surgical placements, and application at a chronic stage remain undetermined.
3
It remains to be demonstrated that PNG can restore sensory function in an incomplete SCI.

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