Light Promotes Regeneration and Functional Recovery and Alters the Immune Response After Spinal Cord Injury

Kimberly R. Byrnes, PhD,1 Ronald W. Waynant, PhD,2Ilko K. Ilev, PhD,2 Xingjia Wu, BS,1 Lauren Barna, BS,1 Kimberly Smith,1 Reed Heckert, BS,1 Heather Gerst, BS,1 and Juanita J. Anders, PhD 1

1 Department of Anatomy, Physiology & Genetics, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814
2 Center for Devices and Radiological Health, ElectroOptics Branch, Food and Drug Administration, HFZ-134, Rockville, Maryland 20857

Background and Objectives: Photobiomodulation (PBM) has been proposed as a potential therapy for spinal cord injury (SCI). We aimed to demonstrate that 810 nm light can penetrate deep into the body and promote neuronal regeneration and functional recovery.

Study Design/Materials and Methods: Adult rats underwent a T9 dorsal hemisection, followed by treatment with an 810 nm, 150mWdiode laser (dosage¼ 1,589 J/cm²). Axonal regeneration and functional recovery were assessed using single and double label tract tracing and various locomotor tasks. The immune response within the spinal cord was also assessed.

Results: PBM, with 6% power penetration to the spinal cord depth, significantly increased axonal number and distance of regrowth (P<0.001). PBM also returned aspects of function to baseline levels and significantly suppressed immune cell activation and cytokine/chemokine expression.

Conclusion: Our results demonstrate that light, delivered transcutaneously, improves recovery after injury and suggests that light will be a useful treatment for human SCI. _ 2005 Wiley-Liss, Inc.

Lasers in Surgery and Medicine 9999:1–15 (2005)