Neurite growth acceleration of adult Dorsal Root Ganglion neurons illuminated by low-level Light Emitting Diode light at 645 nm

Neurite growth induced by red light-caused intracellular reactive oxygen species production through cytochrome c oxidase activation

The applications of red-light photobiomodulation (PBM) to enhance neurite growth have been proposed for many years. However, the detailed mechanisms require further studies. In the present work we used a focused red-light spot to illuminate the junction of the longest neurite and the soma of a neuroblastoma cell (N2a), and demonstrated enhanced neurite growth at 620 nm and 760 nm with adequate illumination energy fluences. In contrast, 680 nm light showed no effect on neurite growth. The neurite growth was accompanied with the increase of intracellular reactive oxygen species (ROS). Using Trolox to reduce the ROS level, this red light-induced neurite growth was hindered. Suppressing the activities of cytochrome c oxidase (CCO) by using either a small-molecule inhibitor or siRNA abrogated the red light-induced neurite growth. These results suggest that red light-induced ROS production through the activation of CCO could be beneficial for neurite growth.

Effects of Photobiomodulation Therapy (LED 630 nm) on Muscle and Nerve Histomorphometry after Axonotmesis

Peripheral injuries constitute a substantial clinical problem with unsatisfactory treatment. The study's objective was to analyze the effects of photobiomodulation therapy (PBMT) on median nerve regeneration and muscle recovery after axonotmesis. Twenty-four rats were randomized into three groups: control (CG), injury (IG), and LED therapy (LEDG). A 630 ± 20 nm (300-mW) LED was placed in contact with the skin. One point over the injury site was irradiated for 30 s, delivering 9 J (9 J cm-2 ). PBMT irradiation was performed once daily for 5 days followed by two-day interval and then more five consecutive days of treatment. Proximal and distal segments of the nerve and flexors muscles were removed for histomorphometric analysis using H&E staining for muscles and osmium tetroxide for nerves. The myelinated fiber and axon diameter and the myelin sheath thickness were greater in the proximal and distal nerve segments in the LEDG compared to the IG (P ≤ 0.05). The number of myelinated fibers was greater in the distal segment of the LEDG (P ≤ 0.05). The area, circumference, and diameter of the muscle fibers were larger in the LEDG than in the IG (P ≤ 0.05). The PBMT protocol used favored axonal regeneration and muscle recovery.

Efficacy and Tolerability of Phototherapy With Light-Emitting Diodes for Sensitive Skin: A Pilot Study

Sensitive skin (SS) syndrome is defined by the occurrence of unpleasant sensations in response to stimuli that should normally not induce such sensations. It affects ~50% of women and 40% of men and can impact the quality of life. There is no consensus on therapeutic management. Phototherapy by light-emitting diodes (LEDs) is increasingly being used in dermatology for various inflammatory skin disorders with significant reduction in SS-10 and good tolerability. A Korean study suggested its efficacy in alleviating SS symptoms associated with other facial diseases. Our objective is to obtain preliminary data on the efficacy of phototherapy with LEDs for alleviating SS symptoms and increasing tolerance in subjects with SS that is not associated with other facial skin disorders. This monocentric pilot study included 30 subjects with SS who had a Sensitive Scale-10 score ≥40. The treatment consisted of red LED light exposure twice a week until significant reduction in SS-10 with a maximal treatment length of 8 weeks. The primary outcome was defined by a 60% decrease in the SS-10 score compared to the baseline.

Results: Thirty subjects were included; 83% were women, and the mean age was 28.9 years. Two participants were considered lost to follow-up. The cheeks (90%) and the nose (70%) were the most frequently involved parts of the face. Cold, heat, temperature variation, water and sun were the most frequent triggering factors. Twenty-eight subjects (93.3%, 95% CI 77.9 to 99.2%) achieved the primary outcome. Significant reduction in SS-10 was achieved in 77% of subjects in six sessions or fewer. The mean (SD) SS-10 scores were 54.7 (12.1) at inclusion, 14.4 (6.0) at the last session and 13.9 (7.5) 2 months after the last session, suggesting that the benefits persist for a few weeks. Two side effects were reported: both were allergic reactions to the nickel contained in the protective goggles. This pilot study had a small sample size and no control group. LEDs were effective in treating SS in all 28 subjects who completed the study in accordance with the protocol, and the benefits persisted for 2 months after the last LED therapy session.

Neurite regrowth stimulation by a red-light spot focused on the neuronal cell soma following blue light-induced retraction

The interaction of light with biological tissues has been considered for various therapeutic applications. Light-induced neurite growth has the potential to be a clinically useful technique for neuron repair. However, most previous studies used either a large illumination area to accelerate overall neurite growth or employed a light spot to guide a growing neurite. It is not clear if optical stimulation can induce the regrowth of a retracted neurite. In the present work, we used blue light (wavelength: 473 nm) to cause neurite retraction, and we proved that using a red-light (wavelength: 650 nm) spot to illuminate the soma near the junction of the retracted neurite could induce neurite regrowth. As a comparison, we found that green light (wavelength 550 nm) had a 62% probability of inducing neurite regrowth, while red light had a 75% probability of inducing neurite regrowth at the same power level. Furthermore, the neurite regrowth length induced by red light was increased by the pre-treatment with inhibitors of myosin functions. We also observed actin propagation from the soma to the tip of the re-growing neurite following red-light stimulation of the soma. The red light-induced extension and regrowth were abrogated in the calcium-free medium. These results suggest that illumination with a red-light spot on the soma may trigger the regrowth of a neurite after the retraction caused by blue-light illumination.

Photobiomodulation Improved the First Stages of Wound Healing Process After Abdominoplasty: An Experimental, Double-Blinded, Non-randomized Clinical Trial

BACKGROUND

Photobiomodulation is widely studied for its potential benefits in the wound healing process. Numerous scientific studies have highlighted its effect on various phases of wound repair, but clinical validations are few. This comparative trial aims to evaluate the influence of photobiomodulation on the post-abdominoplasty healing process.

METHODS

Seventeen Caucasian women (aged 18-55) who underwent an abdominoplasty were enrolled in this double-blinded, controlled clinical trial. The postoperative scars were divided into two areas; the right side of the scars was treated with ten sessions of photobiomodulation (consisting in three types of wavelengths). The other part of the scars was used as control and did not receive any additional treatment. Clinical assessments of both parts of the scars were scheduled at 1, 6 and 12 months postoperative.

RESULTS

Within six months following surgery, significantly improved quality of the scars on the treated side compared with the untreated side was reported by patients and experienced professionals according to Vancouver Scar Scale, Patient and Observer Scar Assessment Scale (p < 0.05) and standardized photographs (p < 0.05). At 1 year of follow-up, patients observed no differences between the treated and untreated sides of the scars. This suggests that photobiomodulation appears to play an early role in the wound healing process, accelerating the first stages of cicatrization.

CONCLUSION

This study statistically validates the positive impact of photobiomodulation treatment on the first stages of the postoperative healing process. Carried out on Caucasians participants only, this study should, however, be performed on a more heterogeneous population to definitively confirm these effects on an international population.

CLINICAL TRIAL REGISTRY

Registro Brasileiro de ensaios clínicos: http://www.ensaiosclinicos.gov.br , Trial RBR-49PK78.

LEVEL OF EVIDENCE II

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Photobiomodulation with red light-emitting diodes accelerates hepatocyte proliferation through reactive oxygen species/extracellular signal-regulated kinase pathway

AIM

Cell-based transplantation is an alternate method of liver transplantation to delay the onset of end-stage liver diseases. For successful treatment, cells need to be expended in vitro expeditiously. However, autogenetic hepatocytes as the ideal cell source for therapy remain in quiescence so proliferation is rare. Photobiomodulation therapy has been used to stimulate some kinds of cell proliferation, but is unknown whether red light-emitting diode (LED) irradiation can promote primary hepatocyte proliferation. The aim of this study was to evaluate the effect of red LED irradiation on hepatocytes in vitro.

METHODS

Mouse primary hepatocytes were isolated and received red LED treatment. The cell viability, reactive oxygen species (ROS) levels, phosphorylated extracellular signal-regulated kinase1/2 (pERK1/2) and some cell cycle-related proteins were observed. Additionally, ROS inhibition and pERK1/2 inhibition were carried out to determine the effect of ROS and ERK1/2 in red LED irradiation.

RESULTS

The red LED irradiation increased hepatocyte proliferation, elevated intracellular ROS levels, and stimulated ERK1/2 activation and cell cycle-related gene expression. The mitosis promoting effect of red LED irradiation could be disturbed by ROS or pERK inhibition. The red LED irradiation promoted hepatocyte proliferation through the ROS/pERK1/2 pathway.

CONCLUSIONS

Red LED irradiation could accelerate hepatocyte proliferation through the ROS/pERK1/2 pathway. Red LED irradiation might be a potential method to increase hepatocyte cell numbers in vitro and support cell-based transplantation in clinical work.

Millisecond infrared laser pulses depolarize and elicit action potentials on in-vitro dorsal root ganglion neurons

This work focuses on the optical stimulation of dorsal root ganglion (DRG) neurons through infrared laser light stimulation. We show that a few millisecond laser pulse at 1875 nm induces a membrane depolarization, which was observed by the patch-clamp technique. This stimulation led to action potentials firing on a minority of neurons beyond an energy threshold. A depolarization without action potential was observed for the majority of DRG neurons, even beyond the action potential energy threshold. The use of ruthenium red, a thermal channel blocker, stops the action potential generation, but has no effects on membrane depolarization. Local temperature measurements reveal that the depolarization amplitude is sensitive to the amplitude of the temperature rise as well as to the time rate of change of temperature, but in a way which may not fully follow a photothermal capacitive mechanism, suggesting that more complex mechanisms are involved.

Modern trends in biophotonics for clinical diagnosis and therapy to solve unmet clinical needs

This contribution covers recent original research papers in the biophotonics field. The content is organized into main techniques such as multiphoton microscopy, Raman spectroscopy, infrared spectroscopy, optical coherence tomography and photoacoustic tomography, and their applications in the context of fluid, cell, tissue and skin diagnostics. Special attention is paid to vascular and blood flow diagnostics, photothermal and photodynamic therapy, tissue therapy, cell characterization, and biosensors for biomarker detection.

The dark art of light measurement: accurate radiometry for low-level light therapy

Lasers and light-emitting diodes are used for a range of biomedical applications with many studies reporting their beneficial effects. However, three main concerns exist regarding much of the low-level light therapy (LLLT) or photobiomodulation literature; (1) incomplete, inaccurate and unverified irradiation parameters, (2) miscalculation of ‘dose,’ and (3) the misuse of appropriate light property terminology. The aim of this systematic review was to assess where, and to what extent, these inadequacies exist and to provide an overview of ‘best practice’ in light measurement methods and importance of correct light measurement. A review of recent relevant literature was performed in PubMed using the terms LLLT and photobiomodulation (March 2014–March 2015) to investigate the contemporary information available in LLLT and photobiomodulation literature in terms of reporting light properties and irradiation parameters. A total of 74 articles formed the basis of this systematic review. Although most articles reported beneficial effects following LLLT, the majority contained no information in terms of how light was measured (73 %) and relied on manufacturer-stated values. For all papers reviewed, missing information for specific light parameters included wavelength (3 %), light source type (8 %), power (41 %), pulse frequency (52 %), beam area (40 %), irradiance (43 %), exposure time (16 %), radiant energy (74 %) and fluence (16 %). Frequent use of incorrect terminology was also observed within the reviewed literature. A poor understanding of photophysics is evident as a significant number of papers neglected to report or misreported important radiometric data. These errors affect repeatability and reliability of studies shared between scientists, manufacturers and clinicians and could degrade efficacy of patient treatments. Researchers need a physicist or appropriately skilled engineer on the team, and manuscript reviewers should reject papers that do not report beam measurement methods and all ten key parameters: wavelength, power, irradiation time, beam area (at the skin or culture surface; this is not necessarily the same size as the aperture), radiant energy, radiant exposure, pulse parameters, number of treatments, interval between treatments and anatomical location. Inclusion of these parameters will improve the information available to compare and contrast study outcomes and improve repeatability, reliability of studies.

Photobiomodulation in promoting wound healing: a review

Despite diverse methods being applied to induce wound healing, many wounds remain recalcitrant to all treatments. Photobiomodulation involves inducing wound healing by illuminating wounds with light emitting diodes or lasers. While used on different animal models, in vitro, and clinically, wound healing is induced by many different wavelengths and powers with no optimal set of parameters yet being identified. While data suggest that simultaneous multiple wavelength illumination is more efficacious than single wavelengths, the optimal single and multiple wavelengths must be better defined to induce more reliable and extensive healing of different wound types. This review focuses on studies in which specific wavelengths induce wound healing and on their mechanisms of action.

Restorative effect and mechanism of mecobalamin on sciatic nerve crush injury in mice

Mecobalamin, a form of vitamin B₁₂ containing a central metal element (cobalt), is one of the most important mediators of nervous system function. In the clinic, it is often used to accelerate recovery of peripheral nerves, but its molecular mechanism remains unclear. In the present study, we performed sciatic nerve crush injury in mice, followed by daily intraperitoneal administration of mecobalamin (65 μg/kg or 130 μg/kg) or saline (negative control). Walking track analysis, histomorphological examination, and quantitative real-time PCR showed that mecobalamin significantly improved functional recovery of the sciatic nerve, thickened the myelin sheath in myelinated nerve fibers, and increased the cross-sectional area of target muscle cells. Furthermore, mecobalamin upregulated mRNA expression of growth associated protein 43 in nerve tissue ipsilateral to the injury, and of neurotrophic factors (nerve growth factor, brain-derived nerve growth factor and ciliary neurotrophic factor) in the L_4–6 dorsal root ganglia. Our findings indicate that the molecular mechanism underlying the therapeutic effect of mecobalamin after sciatic nerve injury involves the upregulation of multiple neurotrophic factor genes.