Exercise dependent increase in axon regeneration into peripheral nerve grafts by propriospinal but not sensory neurons after spinal cord injury is associated with modulation of regeneration-associated genes

Exp Neurol, 2016 · DOI: 10.1016/j.expneurol.2015.09.004 · Published: February 1, 2016

Spinal Cord Injury Regenerative Medicine Rehabilitation

Simple Explanation

This study investigates whether rhythmic sensory stimulation during cycling exercise would boost the intrinsic regenerative state of neurons to enhance axon regeneration into peripheral nerve grafts (PNGs) after spinal cord injury (SCI) in adult rats. Researchers examined how exercise affects the expression of regeneration-associated genes (RAGs) like GAP43, β-actin, and Neuritin in injured and regenerating neurons. The study found that cycling exercise improves regeneration into a PNG from lumbar interneurons but not by primary sensory neurons.

Study Duration

5 weeks

Participants

Adult (225–250g) female Sprague Dawley (SD) rats (n=5 per group)

Evidence Level

Not specified

Key Findings

1
Exercise increases regeneration into peripheral nerve grafts from propriospinal neurons but not sensory neurons after spinal cord injury.
2
The increase in regenerative response is associated with changes in levels of mRNAs encoding the regeneration associated genes (RAGs) GAP43, β-actin and Neuritin.
3
Exercise modulates the regeneration associated gene profile of axotomized and regenerating spinal cord neurons.

Research Summary

This study tested whether exercise affected axon regeneration into a peripheral nerve graft (PNG) while measuring changes in the expression of regeneration associated genes (RAGs) in injured and regenerating neurons. The majority of neurons that regenerate their axon are within 5mm of the lesion and their number increased 70% with exercise. Exercise is a non-invasive approach to modulate gene expression in injured neurons leading to an increase in regeneration.

Practical Implications

Therapeutic potential

Exercise can be a therapy to promote regeneration after SCI.

Neuroplasticity

Exercise appears to play a significant role in neuroplasticity.

Functional recovery

Exercise driven regeneration can improve functional recovery after SCI.

Study Limitations

1
The study focused specifically on injured/regenerating neurons labeled with True Blue, not non-injured neurons.
2
The absence of an effect of exercise on sensory axon growth may have some beneficial effect since aberrant sprouting of primary afferents can lead to development of neuropathic pain.
3
Future studies will examine whether delayed exercise can have a growth promoting effect on chronically injured neurons.

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