Abstract
We have developed a novel, non-invasive nano-pulsed laser therapy (NPLT) system that combines the benefits of near-infrared laser light (808 nm) and ultrasound (optoacoustic) waves, which are generated with each short laser pulse within the tissue. We tested NPLT in a rat model of blast-induced neurotrauma (BINT) to determine whether transcranial application of NPLT provides neuroprotective effects. The laser pulses were applied on the intact rat head 1 h after injury using a specially developed fiber-optic system. Vestibulomotor function was assessed on post-injury days (PIDs) 1–3 on the beam balance and beam walking tasks. Cognitive function was assessed on PIDs 6–10 using a working memory Morris water maze (MWM) test. BDNF and caspase-3 messenger RNA (mRNA) expression was measured by quantitative real-time PCR (qRT-PCR) in laser-captured cortical neurons. Microglia activation and neuronal injury were assessed in brain sections by immunofluorescence using specific antibodies against CD68 and active caspase-3, respectively. In the vestibulomotor and cognitive (MWM) tests, NPLT-treated animals performed significantly better than the untreated blast group and similarly to sham animals. NPLT upregulated mRNA encoding BDNF and downregulated the pro-apoptotic protein caspase-3 in cortical neurons. Immunofluorescence demonstrated that NPLT inhibited microglia activation and reduced the number of cortical neurons expressing activated caspase-3. NPLT also increased expression of BDNF in the hippocampus and the number of proliferating progenitor cells in the dentate gyrus. Our data demonstrate a neuroprotective effect of NPLT and prompt further studies aimed to develop NPLT as a therapeutic intervention after traumatic brain injury (TBI).
Highlights
On the Morris water maze (MWM), untreated, injured rats (Blast) took significantly longer on post-injury days (PIDs) 7, Trials 2, to find the platform compared with the Blast+nano-pulsed laser therapy (NPLT) ( p < 0.05) and sham rats ( p < 0.01; Fig. 3C)
To determine whether NPLT can reduce neuronal injury in the early days after the blast insult, we used quantitative real-time PCR (qRT-PCR) and Laser capture microdissection (LCM) to measure the expression of select messenger RNA (mRNA) known to be involved in neuronal injury and survival
We found that in FJCneg cortical neurons isolated on PID 3 from blast-injured rats, the mRNA levels for BAX, CASPASE-3, and STAT3 were significantly greater compared with both sham and Blast+NPLT rats, whereas the levels of BDNF were significantly lower (Fig. 4A)
Summary
Transcranial low-level laser therapy (LLLT) has gained recognition as an alternative to existing TBI treatments.[8,9,10] LLLT uses near-infrared light (600–1000 nm) to stimulate, repair, regenerate, and protect injured tissue. Initial studies of LLLT focused on stimulation of wound healing and reduction of pain and inflammation in various orthopedic conditions.[11] Recently, several reports demonstrated beneficial effects of LLLT in reducing neuroinflammation, brain lesion volume, and edema in animal models of TBI.[12] they showed a significant neuroprotective effect of transcranial LLLT generated by LED or laser sources (both continuous and pulsed) using controlled cortical impact and closed-head-injury rodent models of TBI. Some clinical case reports tested the therapeutic effect of LLLT for the treatment of chronic TBI patients and showed small but significant improvements in cognitive and motor functions[13,14,15]; as of today, no studies have tested LLLT on animal models of BINT
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