Photobiomodulation Therapy in Burn Wound Healing: Systematic Review and Meta-Analysis of Preclinical Studies

Photobiomodulation Treatment for Second-Degree Burn Treatment-A Double-Blinded Controlled Pilot Trial

Background: Photobiomodulation (PBM) is a technology that has gained much attention in recent years regarding its potential application for stimulating wound healing, alleviating pain, reducing inflammation, and aiding in the restoration of function. Due to a scarcity of evidence in the literature regarding PBM for the treatment of burns, our objective of this study was to test whether treatment with PBM in hospitalized patients with second-degree burns accelerated recovery. Methods: A double-blind controlled study was conducted on nine patients with up to 15% second-degree burns who were hospitalized at Hadassah-Hebrew University Medical Center, Ein Kerem Campus, Jerusalem Israel, between July 2022 and November 2022. Each patient recruited for the study received PBM treatment on part of the burn area (approximately 10%-20% of the burn area), while the control group was the burn area of the same patient treated only with the usual non-PBM. Treatment parameters were light emitting diode surface including continuous and/or pulsed red (660 nm) and near-infrared (840 nm), 5-16 mW/cm2, 2.4-7.7 J/cm2 per treatment session. Results: Patients received three to five treatments with a mean epithelization time of 16 days (±2.89 standard deviation [SD]) in the control area, while only 7.56 (±2.29 SD) in the treatment area. The mean percent reduction in healing time was 46.22% (±4.24 SD), which was found to be statistically significant (p = 0.004). Conclusion: Our study demonstrated a statistically significant acceleration of healing in second-degree burns following treatment with PBM for the treatment of burns in patients. However, further studies are needed to determine if these results translate to a reduction in hospitalization time and medical care costs.

Effect of photobiomodulation in an experimental in vitro model of asthma-Copd overlap

The objective of the study was to evaluate the effect of photobiomodulation (PBM) with laser on the inflammatory process in an experimental in vitro model of ACO. The groups were: (1) human bronchial epithelial cells (BEAS-2B); (2) BEAS-2B cells treated with dexamethasone; (3) BEAS-2B cells irradiated with laser; (4) BEAS-2B cells stimulated with cigarette smoke extract (CSE) + House Dust Mite (HDM); (5) BEAS-2B cells stimulated with CSE + HDM and treated with dexamethasone; (6) BEAS-2B cells incubated with CSE + HDM and irradiated with laser. After 24 h, cytokines were quantified. There was a reduction in TNF-α, IL-1β, IL-6, IL-4, IL-5, IL-13, IL-17, IL-21, IL-23, and an increase in IL-10 and IFN-γ in cells from the laser-irradiated ACO group compared to only ACO group. With these results, we can suggest that photobiomodulation acts in the modulation of inflammation observed in ACO, and may be a treatment option.

Effects of photobiomodulation with blue Light Emitting Diode (LED) on the healing of skin burns

The management of skin burns is still challenging. Among the therapeutic methods used, there are topical treatments with pharmacological and herbal agents, low-intensity therapeutic ultrasound, use of biomaterials, reconstructive techniques and photobiomodulation therapy. The aim of this study was to evaluate the effects of photobiomodulation with blue Light Emitting Diode (LED) on burn healing. Fifty Wistar rats were divided into control (CTRL) (n = 25) and blue LED (LED) (n = 25), with subgroups (n = 5) for each time of euthanasia (7, 14, 21, 28 and 32 days). Treated animals were daily irradiated (470 nm, 1W, 0.44 W/cm2, 50 J/cm2). Clinical evaluations were performed and the Wound Retraction Index (WRI) was determined. Histological sections were submitted to hematoxylin-eosin, toluidine blue and the immunohistochemical technique, with anti-α-SMA and anti-TGF-β1 antibodies. All data were directly collected by previously calibrated evaluators in a blind manner. The values were included in a statistical program. For all statistical tests used, 5% significance level (p < 0.05) was considered. No statistically significant differences in WRI between groups were observed (p > 0.05). Re-epithelialization was higher using LED at 7 and 14 days (p < 0.05) and greater amount of inflammatory cells was observed at 7 days (p = 0.01). With LED at 21 and 32 days, greater number of mast cells were observed (p < 0.05), as well as smaller number of myofibroblasts at 14, 21, 28 and 32 days (p < 0.05) and lower percentage of TGF-β1 positive cells in the conjunctiva at 7, 14 and 21 days (p < 0.05). Negative correlations were observed in LED between the percentage of TGF-β1 in the epithelium and the mean number of inflammatory cells and number of myofibroblasts (p < 0.05). The results suggest that, depending on the period, blue LED can modulate the healing processes of third-degree skin burns, such as re-epithelialization, inflammatory response, mast cell concentration, myofibroblast differentiation and TGF-β1 immunoexpression. Despite these effects, this therapy does not seem to have significant influence on the retraction of these wounds. Future studies, using different protocols, should be carried out to expand the knowledge about the photobiomodulatory mechanisms of this type of light in the healing process.

Inhibition of annexin A7 suppresses senescence-associated heterochromatin foci formation and senescence through the AMPK/mTOR pathway in human dermal fibroblasts

Senescence-associated heterochromatin foci (SAHF) is often used as a biological marker for senescent cells, but the regulation of its formation process is unclear. To find a new modulator of SAHF, we screened our chemical small molecules and found 7-amino-2,3,4,5-tetrahedrobenzo[b][1,4] oxazepin-3-ol (ABO) that was identified as an inhibitor of annexin A7 GTPase (ANXA7) dramatically suppressed the aggregation of heterochromatin protein (HP1γ), an indicator of SAHF. To understand its action mechanism, we first observed the changes in the karyoplasmic ratio of ANXA7 because HP1γ mainly located in the nucleus. The results showed that ABO elevated the protein level of ANXA7 in the nucleus. Therefore, we raised a hypothesis that ANXA7 interacted with HP1γ and regulated its phosphorylation, which is closely related to the formation of SAHF. The co-immunoprecipitation and Western blot experiment results showed that ANXA7 had no direct interaction with HP1γ, however, the phosphorylation of HP1γ was increased by ABO, which suggested that ANXA7 indirectly regulated HP1γ phosphorylation. Then, based on our previous discovery of ANXA7 interacting with AMP-activated protein kinase (AMPK), we investigated the effect of the AMPK/mammalian target of rapamycin (mTOR) signaling pathway on ABO-increased phosphorylation of HP1γ. We found that ABO decreased AMPK phosphorylation and increased the phosphorylation level and activity of mTOR. In the presence of an AMPK activator or mTOR inhibitor, ABO could not increase HP1γ phosphorylation. As a result, ABO inhibited the senescence of human dermal fibroblasts (HDFs). In this study, we found that ANXA7 was a new regulator of SAHF, it could regulate the formation of SAHF through the AMPK/mTOR pathway. The data suggested that ABO could be used as a powerful tool to inhibit the replicative senescence of HDFs.

Photobiomodulation at molecular, cellular, and systemic levels

Since the reporting of Endre Mester's results, researchers have investigated the biological effects induced by non-ionizing radiation emitted from low-power lasers. Recently, owing to the use of light-emitting diodes (LEDs), the term photobiomodulation (PBM) has been used. However, the molecular, cellular, and systemic effects involved in PBM are still under investigation, and a better understanding of these effects could improve clinical safety and efficacy. Our aim was to review the molecular, cellular, and systemic effects involved in PBM to elucidate the levels of biological complexity. PBM occurs as a consequence of photon-photoacceptor interactions, which lead to the production of trigger molecules capable of inducing signaling, effector molecules, and transcription factors, which feature it at the molecular level. These molecules and factors are responsible for cellular effects, such as cell proliferation, migration, differentiation, and apoptosis, which feature PBM at the cellular level. Finally, molecular and cellular effects are responsible for systemic effects, such as modulation of the inflammatory process, promotion of tissue repair and wound healing, reduction of edema and pain, and improvement of muscle performance, which features PBM at the systemic level.

Wound contraction rate in excised and unexcised burn wounds with laser photobiomodulation: Systematic review and meta-analysis of preclinical studies

INTRODUCTION

Laser photobiomodulation (laser PBM) is an effective means of accelerating burn wound contraction, however it is still unclear whether laser PBM produces greater benefit when applied directly to excised and unexcised burn wounds . The aim of this systematic review of preclinical studies was to determine the effectiveness of laser PBM in the wound contraction rate in excised and unexcised burn wounds.

MATERIALS AND METHODS

A systematic search was conducted in the EMBASE, MEDLINE and LILACS databases. Preclinical studies were included that analysed the effectiveness of laser PBM in burn wound contraction, and assessed wound closure. The SYRCLE risk of bias tool was used. Random effects models were used to estimate the pooled effect.

RESULTS

Thirteen studies were included in the qualitative analysis and six in the quantitative analysis. Two weeks after the lesion, laser PBM favoured the wound contraction percentage, increasing the closure rate in excised burn wounds (SMD= 1.34, CI 95% 0.41 to 2.27, 0.41-2.27, I²=0%, =0%, low certainty of evidence. In unexcised burns, it was uncertain whether laser PBM increased or diminished the wound contraction rate (SMD=1.22(SMD=1.22 CI 95% -0.05 to 2.49, I²=68%; =68%; very low certainty of evidence).

CONCLUSIONS

In the animal model, laser PBM is effective in increasing the wound contraction rate in excised burns. However, due to the low certainty of the evidence, uncertainty remains about the true magnitude of the effect of laser on wound contraction in animals; our results should therefore be interpreted with caution.