Following Spinal Cord Injury Transected Reticulospinal Tract Axons Develop New Collateral Inputs to Spinal Interneurons in Parallel with Locomotor Recovery

Neural Plasticity, 2017 · DOI: https://doi.org/10.1155/2017/1932875 · Published: September 12, 2017

Spinal Cord Injury Neuroplasticity Rehabilitation

Simple Explanation

This study investigates how the reticulospinal tract (RtST), which is important for movement, adapts after a spinal cord injury (SCI). The researchers looked at how injured RtST axons form new connections with spinal interneurons, called propriospinal interneurons (PrINs), and how this relates to recovery of movement. The study used a staggered SCI model in rats, where the spinal cord is cut in two separate locations, either at the same time (cSTAG) or with a delay (dSTAG). The dSTAG group showed better locomotor recovery compared to the cSTAG group. The findings suggest that injured RtST axons can form new connections with PrINs, and this process is associated with improved movement after SCI. The timing of the injury also matters, as a delay between injuries seems to promote better recovery.

Study Duration

7 weeks

Participants

18 adult female Lewis rats

Evidence Level

Not specified

Key Findings

1
Rats with a delayed staggered SCI (dSTAG) showed significantly more RtST-PrIN contacts in the grey matter compared to those with a concomitant staggered SCI (cSTAG).
2
Enhanced locomotor recovery was observed in dSTAG animals, who significantly outperformed cSTAG animals in the BBB test.
3
dSTAG animals exhibited enhanced collateral growth of RtST axons compared to cSTAG animals, indicating more extensive collateralization in the grey matter between injury sites.

Research Summary

This study demonstrates that injured RtST axons can rewire and form new connections with PrINs after SCI, which is associated with improved locomotor performance. The timing of the SCI plays a critical role, with a delayed staggered injury model (dSTAG) leading to greater RtST-PrIN connectivity and better locomotor recovery compared to a concomitant staggered injury model (cSTAG). The study suggests that activity in neuronal networks below the first SCI may contribute to enhanced recovery, as dSTAG rats showed locomotor improvements before the second hemisection.

Practical Implications

Therapeutic Target

The reticulospinal tract (RtST) could be targeted to promote plasticity-promoting treatments.

Rehabilitation Strategies

Activity below the lesion is likely a key factor for rewiring, with therapeutic strategies that promote activity early after injury potentially leading to better outcomes.

Timing of Interventions

The timing of interventions after SCI may be critical, as a delay between injuries allows for immediate post-SCI activity, resulting in greater plasticity compared to simultaneous injuries.

Study Limitations

1
The study does not consider the number of naturally occurring RtST collaterals projecting towards PrINs in intact animals.
2
Given the limitations of anterograde tracing techniques, not all RtST axons may have been labeled, potentially resulting in spared, untraced axons in the staggered injury model.
3
A causal relation between RtST-PrIN connections and functional changes remains to be established.

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