Implantable and transcutaneous photobiomodulation promote neuroregeneration and recovery of lost function after spinal cord injury

Bioeng Transl Med, 2024 · DOI: 10.1002/btm2.10674 · Published: May 1, 2024

Spinal Cord Injury Regenerative Medicine Rehabilitation

Simple Explanation

Spinal cord injuries (SCI) often lead to permanent disabilities because the central nervous system struggles to repair itself. This study explores using photobiomodulation (PBM), which involves applying red or near-infrared light, as a potential treatment. The researchers tested different doses of light on nerve cells in the lab to find the best way to protect them. They also developed a way to deliver this light directly to the injured spinal cord using an implantable device, comparing it to applying light through the skin. The results showed that both methods of delivering PBM helped to regenerate nerves and improve functional recovery after SCI in rats. This suggests that PBM, especially through implantable devices, could be a promising treatment for SCI patients.

Study Duration

6 Weeks

Participants

Adult Sprague-Dawley rats (n = 50)

Evidence Level

Level 2: Experimental study - In vitro and in vivo rat model

Key Findings

1
Optimal neuroprotection in vitro was achieved with PBM between 4 and 22 mW/cm2, with 11 mW/cm2 for 1 min per day (0.66 J/cm2) increasing cell viability by 45% and neurite outgrowth by 25%.
2
Both implantable (iPBM) and transcutaneous (tcPBM) delivery methods increased activation of regeneration-associated protein GAP43 in DRGN, leading to significant improvements in locomotor and sensory function recovery at 6 weeks post-injury.
3
PBM treatment resulted in reduced lesion size and glial scar deposition in the spinal cord at 6 weeks post-injury.

Research Summary

This study investigates the efficacy of photobiomodulation (PBM) in promoting neuroregeneration and functional recovery after spinal cord injury (SCI) using both implantable (iPBM) and transcutaneous (tcPBM) delivery methods. In vitro experiments optimized PBM dose regimens, identifying 11 mW/cm2 as optimal for neuroprotection. Cadaveric modeling validated invasive and noninvasive delivery protocols, ensuring equivalent PBM doses at the SCI site. In vivo results demonstrated that both iPBM and tcPBM increased axonal regeneration, improved functional outcomes, and reduced lesion size, suggesting PBM's potential for clinical use in SCI patients.

Practical Implications

Clinical Translation

Implantable PBM devices can be developed for clinical use in SCI patients, providing a more effective method of delivering light therapy to deep anatomical structures.

Neuroprotective Strategy

PBM can be used as a neuroprotective strategy after SCI to mitigate neuroinflammation and neuronal apoptosis.

Combination Therapy

PBM could be combined with other therapeutic interventions, such as stem cell transplantation, to enhance neural repair after SCI.

Study Limitations

1
The effect of the implant itself was not studied directly, and there may have been an immune response to the presence of the indwelling probe.
2
Animal welfare concerns precluded a longer duration of study with the implant in situ, limiting the assessment of long-term effects.
3
Ex vivo cadaveric models inherently limit the accuracy of dosimetry measurements due to differences compared to in vivo conditions.

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