Effect of red and near-infrared wavelengths on low-level laser (light) therapy-induced healing of partial-thickness dermal abrasion in mice

660-808 nm simultaneous irradiation enhance keratinocyte migration and change the keratin expression: An in vitro study

This in vitro study aimed to determine if simultaneous irradiation with 660 and 808 nm wavelengths enhances keratinocyte migration and alters keratin expression. Keratinocytes were exposed to either 660 nm or 808 nm irradiation alone, as well as to both wavelengths simultaneously using a laser device with the same energy parameters (2 J, 22.22 J/cm2). Cell viability, migration, and keratin expression (K1, K10, K5, and K14) were assessed in a scratch model assay. After 24 h of PBM, the simultaneous group showed higher cell viability compared with the control and the irradiated groups with one wavelength (660 and 808 nm groups). Simultaneous irradiation also resulted in a smaller scratch area compared with the control and 660 nm groups. The frequency of cells positive for K1/K10 at the wound border was lower after dual irradiation, while cells positive for K5/K14 at the wound periphery were more frequent after simultaneous irradiation. These results suggest a potential increase in the population of less-differentiated keratinocytes following 660-808 nm dual emission. In conclusion, combined irradiation improved cell viability and migration, potentially leading to a shift in keratinocyte differentiation. This dual-wavelength effect may help stimulate the reepithelization process in the tissue repair.

Beyond ultraviolet radiation: Immune system modulation through skin exposure to visible light and infrared radiation

Sunlight profoundly affects skin health when it is exposed. After acute exposure, a robust inflammatory response is initiated locally. Moreover, chronic exposures lead to carcinogenesis and photoaging. Local and systemic immunosuppression is also triggered after skin irradiation, affecting adaptive immune responses. These effects are mainly produced by the ultraviolet radiation contained in sunlight and were extensively described and reviewed. However, using UV filters during sunbathing and outdoor activities may allow visible light (VL) wavelengths and infrared radiation (IRR) to reach skin cells. Additionally, the employment of therapeutic VL and IR-emitting lasers and LED devices is increasing for various skin conditions. This literature review aims to present current knowledge on the effects of VL and IRR modulating the skin and systemic immune system. These modulations impact healthy skin and can modify immune responses to diverse stimuli in various cell types. According to the wavelength and the dose, VL and IRR increase the production of reactive oxygen species and promote faster wound healing. Moreover, they modulate inflammatory mediators, such as several cytokines and prostaglandins. However, skin exposure to VL can also affect adaptive immune responses. The study of VL and IRR effects on immunity would promote new uses for phototherapy and may establish the need for new strategies in photoprotection.

Investigating the wound healing potential of low-power 661 nm laser light in a pigmented hairless murine model

Photobiomodulation (PBM) has emerged as a promising method for enhancing wound healing. However, a standardized therapeutic protocol has not yet been established. This study aimed to determine the optimal irradiation parameters for wound healing in pigmented hairless mice (SKH-hr2). Mice were irradiated daily with energy doses of 2 or 4 J/cm2, achieved with different power densities in each group: 20, 50, or 100 mW/cm2. Various methods were used to evaluate the therapeutic efficacy, including histopathological analysis, clinical observation, photo-documentation, assessment of biophysical skin parameters, and Fourier Transform infrared (FT-IR) spectroscopy. The results indicated that the most favorable outcomes regarding wound healing acceleration and inflammation reduction were achieved with an irradiation setting of 50 mW/cm2 and 2 J/cm2. However, the group subjected to prolonged irradiation times with a power density of 20 mW/cm2 and energy of 4 J/cm2 exhibited subcutaneous bleeding. The FT-IR spectral absorption bands of amide groups provided important molecular-level information about the secondary structure of collagen, particularly in relation to skin regeneration and the response to applied energy, in agreement with histological data. This study highlights the critical need for further investigation into the parameters of photobiomodulation to ensure its effective application to the different skin phototypes and to mitigate potential adverse effects arising from incorrect usage.

Brain photobiomodulation: a potential treatment in Alzheimer's and Parkinson's diseases

Alzheimer's Disease (AD) and Parkinson's Disease (PD) are common neurodegenerative diseases, characterized by the progressive loss of synapses and neurons, leading to cognitive and motor decline. Their pathophysiology includes cerebral lesions, oxidative stress, neuroinflammation as well as brain-gut axis microbiota dysbiosis. Preclinical investigations demonstrated that brain photobiomodulation (bPBM) reduces oxidative stress and inflammation, increases cerebral blood flow and enhance neurogenesis and synaptogenesis, which makes bPBM a promising treatment in AD and PD. This review focuses on the clinical application of bPBM in AD and PD. It aims to provide a scientific overview of the current clinical knowledge, review recent clinical studies findings, and describe future directions and upcoming clinical studies. So far, several clinical studies investigated bPBM therapy, at various parameters, both in patients with AD and related dementia, and PD. All demonstrate bPBM safety and bring valuable clinical information regarding efficacy, with particularly promising results in AD. However, their exploratory design and inconsistent quality lead to a low level of evidence, which currently does not support the widespread use of bPBM in clinical practice. Future clinical research should address two gaps: the need for robust double-blinded RCTs vs sham with a higher number of patients and a longer follow-up, and the need for research focusing on dosimetry to determine which bPBM parameters are optimal. The ongoing or unpublished clinical studies on bPBM should fill in this gap.

The wound healing effects of linearly polarized irradiation in photobiomodulation

We report the fabrication of a polarization-based photobiomodulation (PBM) system and its performance on wound healing effects. The light source for PBM was a 625 nm LED and two different linear polarizations (P-wave and S-wave) were generated using the wire grid linear polarizers. To confirm the effect of PBM on polarization, wounds were created on hairless mice, and the healing process was compared. The light source conditions for comparison were control, two linearly polarized light, and unpolarized light. The light irradiation conditions for each group were based on the energy settings (energy 18 J/cm2, power density 30 mW/cm2, exposure time 600 sec) commonly used in LED masks. After creating the wound, the light was irradiated only once. To confirm the wound healing effect over time, it was evaluated through wound surface area measurements, self-made optical coherence tomography images, and histological images. In the group irradiated with S-wave polarized light, the percentage from the initial wound size was reduced to 70.73%, and the epithelial tongue ratio reached 58.36% on day 7 after PBM, indicating the fastest recovery. In this way, the potential of a new product that can increase the effect of wound healing or skin regeneration by adjusting the polarization state without irradiating high energy was confirmed.

Oral mucosa cues for regeneration using Photobiomodulation

Photobiomodulation therapy (PBMT) is gaining recognition as an effective method for repairing damaged tissues, particularly in skin and mucosa injuries. Despite its growing use, there remains a significant gap in understanding the interaction of ectomesenchymal components during light therapy. This study explored various near-infrared light parameters on stressed skin keratinocytes (KC) cultured alone or in association with oral fibroblasts (FB) using a transwell system. Reactive oxygen species (ROS) levels were quantified, alongside observations of cell viability/proliferation, migration, and pro-resolutive gene expression in KC cultivated conventionally (at 1, 5, and 50 J/cm2; 1.4, 7 and, 70 s; 0.03, 0.14, and 1.4 J, respectively; 0.71 W/cm2; 20 mW) and co-cultured with FB (at 5 J/cm2). Murine tongue fragments were also treated at 5 J/cm2 for three days. The results revealed increased ROS levels in stressed cells. PBMT enhanced cell viability/proliferation and migration of KC in vitro, while pro-inflammatory cytokines were predominantly suppressed following irradiation. All energy densities and culture models showed upregulation of amphiregulin. In the co-culture system, PBMT notably upregulated interleukin 1 - receptor antagonist and vascular endothelial growth factor genes while downregulating transforming growth factor-β1 expression. In ex vivo tongue fragments, PBMT significantly increased lamina propria thickness and spindle-shaped cell counts compared to non-irradiated samples. Overall, near-infrared PBMT demonstrated pro-regenerative effects by modulating inflammation. The activation of pro-resolutive molecules and the dampening of cytokines may favor early tissue remodeling in the dermis counterpart.

Synergistic effects of platelet-rich fibrin and photobiomodulation on bone regeneration in MC3T3-E1 Preosteoblasts

BACKGROUND

Platelet-rich fibrin (PRF) and Photobiomodulation (PBM) are established methods for promoting bone healing. PRF enhances cell proliferation and migration due to its rich concentration of growth factors, while PBM stimulates tissue repair through mitochondrial activation. Despite their efficacies, no in-depth studies have explored the synergistic effects of combining PRF and PBM.

METHODS

PRF was prepared at 50 % and 100 % concentrations, and PBM was applied using an 830 nm near-infrared laser at a dose of 5 J/cm². Cell viability, migration, and calcium deposition were assessed over seven and fourteen days.

RESULTS

The combination of PRF and PBM significantly improved cell viability, migration, and calcium deposition, with the most notable effects observed after seven and fourteen days. However, a slight decrease in calcium deposition was noted in the 100 % PRF combined with the PBM group, suggesting a potential feedback mechanism at higher PRF concentrations.

CONCLUSIONS

This study explores the synergistic effects of PRF and PBM, offering new insights into optimizing bone tissue engineering strategies. The findings highlight the potential of this combined approach in enhancing bone regeneration, although further research is needed to refine the optimal conditions for these therapies.

A Randomized Controlled Trial Evaluating the Effect of Local Application of Sodium Alendronate Gel and Low-Level Laser Therapy (LLLT) On Peri-Implant Tissue Healing in Wistar Rats

Objective

To evaluate the effect of local application of Sodium Alendronate incorporated in Carbapol gel together with LLLT on peri-implant tissue healing in Wistar rat femurs.

Methods

Twenty-four male Wistar rats were randomly divided into 4 groups: Group 1 (the control group), Group 2 (the Sodium Alendronate group), Group 3 (the Sodium Alendronate and LLLT group), and Group 4 (the LLLT group). Mini implants were placed in right and left femur bones in all the four groups. Implants of groups 2 and 3 were coated in 1mg Carbapol gel incorporated with 1 mg Sodium alendronate. Groups 3 and 4 were exposed to LLLT (CO 2 laser, wavelength 830nm; 2.1J/cm 2) on 1 st, 7 th, 14 th and 21 st day. Animals were sacrificed on the 28th day, following which the femurs were dissected out and stored in 10% buffered formaldehyde for histopathological analysis.

Results

Groups 3 and 4 showed bony union and formation of reorganized spongiosa whereas Groups 1 and 2 showed fibrous union. The bone marrow from Group 3 had an adult-type fatty marrow, while that from Group 2 and 4 was occupied by red blood cells. Group 1 showed initial stages of bone healing in which the defect occupied more than half of the bone marrow.

Conclusion

LLLT given using CO 2 laser therapy, together with a one-time application of Sodium Alendronate in Carbapol gel at the time of implant placement optimally enhances healing of peri-implant tissues.

Visible light accelerates skin wound healing and alleviates scar formation in mice by adjusting STAT3 signaling

During the wound healing process, the activation of signal transducer and activator of transcription 3 (STAT3) is considered crucial for the migration and proliferation of epithelial cells, as well as for establishing the inflammatory environment. However, an excessive STAT3 activation aggravates scar formation. Here we show that 450 nm blue light and 630 nm red light can differentially regulate the phosphorylation of STAT3 (p-STAT3) and its downstream cytokines in keratinocytes. Further mechanistic studies reveal that red light promotes wound healing by activating the PI3 kinase p110 beta (PI3Kβ)/STAT3 signaling axis, while blue light inhibits p-STAT3 at the wound site by modulating cytochrome c-P450 (CYT-P450) activity and reactive oxygen species (ROS) generation. In a mouse scar model, skin wound healing can be significantly accelerated with red light followed by blue light to reduce scar formation. In summary, our study presents a potential strategy for regulating epithelial cell p-STAT3 through visible light to address skin scarring issues and elucidates the underlying mechanisms.

Tailoring photobiomodulation to enhance tissue regeneration

Photobiomodulation (PBM), the use of biocompatible tissue-penetrating light to interact with intracellular chromophores to modulate the fates of cells and tissues, has emerged as a promising non-invasive approach to enhancing tissue regeneration. Unlike photodynamic or photothermal therapies that require the use of photothermal agents or photosensitizers, PBM treatment does not need external agents. With its non-harmful nature, PBM has demonstrated efficacy in enhancing molecular secretions and cellular functions relevant to tissue regeneration. The utilization of low-level light from various sources in PBM targets cytochrome c oxidase, leading to increased synthesis of adenosine triphosphate, induction of growth factor secretion, activation of signaling pathways, and promotion of direct or indirect gene expression. When integrated with stem cell populations, bioactive molecules or nanoparticles, or biomaterial scaffolds, PBM proves effective in significantly improving tissue regeneration. This review consolidates findings from in vitro, in vivo, and human clinical outcomes of both PBM alone and PBM-combined therapies in tissue regeneration applications. It encompasses the background of PBM invention, optimization of PBM parameters (such as wavelength, irradiation, and exposure time), and understanding of the mechanisms for PBM to enhance tissue regeneration. The comprehensive exploration concludes with insights into future directions and perspectives for the tissue regeneration applications of PBM.

Use of low-level laser therapy as an adjuvant therapy for phlebostatic lesions

Low-intensity laser therapy (LILT) is commonly used as an adjuvant therapy for treating injuries. This integrative literature review was carried out in the MEDLINE, LILACS, CUMED, BDENF, SPORTDiscus, Dentistry & Oral Sciences Source, Academic Source and CINAHL databases. Among the inclusion criteria were: range from 2011 to 2021, in English, Portuguese and Spanish and any study, with the exception of preprints and books. The question was answered: "What is the effectiveness described in the literature of using low-intensity laser therapy (LILT) in the treatment of venous lesions?" The wavelength used in studies varied from 635 nm of red ray to 780 nm of infrared ray, generating healing improvement at any length. LBI presented itself as a low-cost and easy-to-apply adjuvant option, alleviating pain complaints and improving healing in patients with vasculogenic lesions.

Long-term effects of photobiomodulation therapy on blood pressure in obese rats induced by a high-fat diet

The main cardiovascular disease risk associated with obesity is hypertension. The therapeutic use of photobiomodulation therapy (PBM) is suggested for the treatment of wound healing, osteoarthritis, and arterial diseases. However, few studies have measured how red laser (at 660 nm) acts over hypertension, and any of those studies used experimental obesity model. The aim of the study was an attempt to evaluate the long-term effect of PBM on systolic blood pressure in an animal model of obesity, induced by a high-fat diet (HFD). Our results indicate that PBM carried out 3 days a week was able to prevent the increase in blood pressure (133.75 ± 4.82 mmHg, n = 8) induced by a high-fat diet (150.00 ± 4.57 mmHg, n = 8; p < 0.05), restore nitric oxide levels (control: 31.7 ± 5.5 μM, n = 8; HFD + PBM: 29.9 ± 3.7 μM, n = 8 > HFD: 22.2 ± 2.9 μM, n = 8, p < 0.05), decrease lipoperoxidation (control: 1.65 ± 0.25 nM, n = 8; HFD + PBM: 2.05 ± 0.55 nM, n = 8 < HFD: 3.20 ± 0.47 nM, n = 8; p < 0.05), and improve endothelial function (pD2 control: 7.39 ± 0.08, n = 8 > pD2 HFD + PBM: 7.15 ± 0.07, n = 8 > HFD: 6.94 ± 0.07, n = 8; p < 0.05). Our results indicate that PBM prevents the elevation of blood pressure in an obese animal model by a mechanism that involves improvement of endothelial function through an antioxidant effect.

Brain photobiomodulation therapy on neurological and psychological diseases

Photobiomodulation (PBM) therapy is an innovative treatment for neurological and psychological conditions. Complex IV of the mitochondrial respiratory chain can be stimulated by red light, which increases ATP synthesis. In addition, the ion channels' light absorption causes the release of Ca2+, which activates transcription factors and changes gene expression. Neuronal metabolism is improved by brain PBM therapy, which also promotes synaptogenesis and neurogenesis as well as anti-inflammatory. Its depression-treating potential is attracting attention for other conditions, including Parkinson's disease and dementia. Giving enough dosage for optimum stimulation using the transcranial PBM technique is challenging because of the rapidly increasing attenuation of light transmission in tissue. Different strategies like intranasal and intracranial light delivery systems have been proposed to overcome this restriction. The most recent preclinical and clinical data on the effectiveness of brain PBM therapy are studied in this review article.

Photobiomodulation Facilitates Rat Cutaneous Wound Healing by Promoting Epidermal Stem Cells and Hair Follicle Stem Cells Proliferation

BACKGROUND

Cutaneous wound healing represents a common fundamental phenomenon requiring the participation of cells of distinct types and a major concern for the public. Evidence has confirmed that photobiomodulation (PBM) using near-infrared (NIR) can promote wound healing, but the  cells involved and the precise molecular mechanisms remain elusive.

METHODS

Full-thickness skin defects with a diameter of 1.0 cm were made on the back of rats and randomly divided into the control group, 10 J, 15 J, and 30 J groups. The wound healing rate at days 4, 8, and 12 postoperatively was measured. HE and Masson staining was conducted to reveal the histological characteristics. Immunofluorescence staining was performed to label the epidermal stem cells (ESCs) and hair follicle stem cells (HFSCs). Western blot was performed to detect the expressions of proteins associated with ESCs and HFSCs. Cutaneous wound tissues were collected for RNA sequencing. Gene ontology and the Kyoto Encyclopedia of Genes and Genomes analysis was performed, and the hub genes were identified using CytoHubba and validated by qRT-PCR.

RESULTS

PBM can promote reepithelialization, extracellular matrix deposition, and wound healing, increase the number of KRT14+/PCNA+ ESCs and KRT15+/PCNA+ HFSCs, and upregulate the protein expression of P63, Krt14, and PCNA. Three hundred and sixty-six differentially expressed genes (DEGs) and 7 hub genes including Sox9, Krt5, Epcam, Cdh1, Cdh3, Dsp, and Pkp3 were identified. These DEGs are enriched in skin development, cell junction, and cadherin binding involved in cell-cell adhesion etc., while these hub genes are related to skin derived stem cells and cell adhesion.

CONCLUSION

PBM accelerates wound healing by enhancing reepithelialization through promoting ESCs and HFSCs proliferation and elevating the expression of genes associated with stem cells and cell adhesion. This may provide a valuable alternative strategy to promote wound healing and reepithelialization by modulating the proliferation of skin derived stem cells and regulating genes related to cell adhesion.

Comparison of three different dosages of low-level laser therapy on expression of cell proliferation and inflammatory markers following ovariohysterectomy in rats

The objective of the current study was to evaluate Low-level laser therapy (LLLT) on the healing of incisional wounds following ovariohysterectomy in rats, by means of subjective histopathological and immunohistochemical analysis. A total of 72 female Wistar rats were categorised into four treatment groups (Group I; sacrification 4 hours following only one LLLT application, Group II; sacrification 7 days following only one LLLT application, Group III; sacrification 4 hours after two LLLT applications, and Group IV; sacrification 7 days after two LLLT applications). Each group was further divided into four different doses subgroups (Group Control [C, off mode LLLT application], L1 [1 J/cm2], L3 [3 J/cm2], and L6 [6 J/cm2]), with equal representation in each subgroup. Ovariohysterectomy was employed using two 2-cm-length midline abdominal incisions in the left and right sides of line alba. The Group C was assigned to the left side incision to each rat in the study. After irradiation, the tissue was subjected to histopathological analysis to determine the extent of mononuclear cell infiltration, edoema, and epithelialization. Additionally, immunohistochemical analysis was performed to evaluate the expression of proliferating cell nuclear antigen (pCNA) and inducible nitric oxide synthase (iNOS). Group L1 and L3 significantly decreased mononuclear cell infiltration compared with Group C in all treatment groups (p < 0.05). Group L3 significantly decreased edoema compared with Group C in all groups except for treatment Group I (p < 0.05). Group L2 and L3 significantly increased epithelization in treatment Group IV (p < 0.05). Moreover, Group L2 and L3 significantly increased pCNA in all groups, while L2 and L3 significantly decreased iNOS expression in treatment Group II, III, and IV (p < 0.05). However, no statistical difference was found between subgroups of treatment Group I in iNOS expiration (p > 0.05). The results of the current examination demonstrated that LLLT can modulate mononuclear cell infiltration and edoema, and improve epithelization, as well as increase pCNA expression, whereas decrease iNOS expression during the wound healing process, therefore enhancing wound healing following ovariohysterectomy in rats.

Photosensitizing deep-seated cancer cells with photoprotein-conjugated upconversion nanoparticles

To resolve the problem of target specificity and light transmission to deep-seated tissues in photodynamic therapy (PDT), we report a cancer cell-targeted photosensitizer using photoprotein-conjugated upconversion nanoparticles (UCNPs) with high target specificity and efficient light transmission to deep tissues. Core-shell UCNPs with low internal energy back transfer were conjugated with recombinant proteins that consists of a photosensitizer (KillerRed; KR) and a cancer cell-targeted lead peptide (LP). Under near infrared (NIR)-irradiating condition, the UCNP-KR-LP generated superoxide anion radicals as reactive oxygen species via NIR-to-green light conversion and exhibited excellent specificity to target cancer cells through receptor-mediated cell adhesion. Consequently, this photosensitizing process facilitated rapid cell death in cancer cell lines (MCF-7, MDA-MB-231, and U-87MG) overexpressing integrin beta 1 (ITGB1) receptors but not in a cell line (SK-BR-3) with reduced ITGB1 expression and a non-invasive normal breast cell line (MCF-10A). In contrast to green light irradiation, NIR light irradiation exhibited significant PDT efficacy in cancer cells located beneath porcine skin tissues up to a depth of 10 mm, as well as in vivo tumor xenograft mouse models. This finding suggests that the designed nanocomposite is useful for sensing and targeting various deep-seated tumors.

Assessment of Effects of Low-Level Light Therapy on Scalp Condition and Hair Growth

Background

The appearance of the scalp and hair is very important aesthetically regardless of age or sex. Although there are many drugs and treatment methods for scalp problems and hair loss, the treatment response is still insufficient.

Aims and Objectives

To evaluate the efficacy of low-level light therapy in a helmet-like device.

Materials and Methods

This study was designed as a 24-week trial with 50 participants. All participants used a helmet-shaped device emitting 630-690, 820-880, and 910-970 nm light wavelengths, for 20 minutes, daily for 24 weeks. A phototrichogram for hair density and thickness, Global Aesthetic Improvement Scale score, erythema index, and sebum secretions of the scalp were evaluated at baseline and at 12 and 24 weeks.

Results

After 24 weeks of treatment, hair density and hair thickness were found to have significantly increased (P <.01 and P =0.013, respectively) and sebum secretion of vertex area had decreased significantly (P <.01). Of 49 participants, 73.47% of the participants showed improvement in the overall appearance of the scalp (n = 36).

Conclusion

A helmet-like low-level light therapy device can improve the appearance of the hair, with thickening and increase in the density of the hair, and can improve scalp condition by decreasing sebum secretion.

Point-of-care optical devices in clinical imaging and screening: A review on the state of the art

Integration of optical technologies in biomedical sciences permitted light manipulation at smaller time-length scales for specific detection and imaging of biological entities. Similarly, advances in consumer electronics and wireless telecommunications strengthened the development of affordable and portable point-of-care (POC) optical devices, circumventing the necessity of conventional clinical analyses by trained personnel. However, many of the POC optical technologies translated from bench to bedside require industrial support for their commercialization and dissemination to the population. This review aims to demonstrate the intriguing progress and challenges of emerging POC devices utilizing optics for clinical imaging (depth-resolved and perfusion imaging) and screening (infections, cancer, cardiac health, and haematologic disorders) with a focus on research studies over the previous 3 years. Special attention is given to POC optical devices that can be utilized in resource-constrained environments.

Influence of Three Laser Wavelengths with Different Power Densities on the Mitochondrial Activity of Human Gingival Fibroblasts in Cell Culture

Phototherapy plays a key role in wound healing and tissue regeneration. The use of lasers has the potential to become an effective and minimally invasive treatment in periodontal and peri-implant disease. The aim of this study was to evaluate the influence of three laser wavelengths with the combination of parameters such as power density and energy density on human gingival fibroblasts (hGFs) in vitro culture. Isolated cells were seeded in 96-well plates with culture medium (DMEM, Dulbecco's modified Eagle's medium) supplemented with 10% fetal bovine serum (FBS). After 24 h cells were irradiated (1064, 980 and 635 nm, various energy density value). After 24, 48 and 72 h, cells were evaluated for viability. Data were analyzed by ANOVA followed by Tukey's HSD test. We found the best outcomes for hGFs irradiated with laser 1064 nm for all combinations of power output (50/400/1000 mW) and energy dose (3/25/64 J/cm²) after 48 h and 72 h compared with control group. Cell viability increase ranged from 0.6× (3 J/cm², 50 mW) to 1.3× (64 J/cm², 1000 mW). Our findings indicate that the appropriate use of low-level laser irradiation (LLLI) can increase the proliferation rate of cultured cells. The use of LLLI can be extremely useful in tissue engineering and regenerative medicine.

The associations between diode laser (810 nm) therapy and chronic wound healing and pain relief: Light into the chronic wound patient's life

Chronic wounds have become one of the major issues in medicine today, the treatments for which include dressing changes, negative pressure wound therapy, hyperbaric oxygen, light irradiation, surgery and so forth. Nevertheless, the application of diode lasers in chronic wounds has rarely been reported. This retrospective cohort study aimed to evaluate the therapeutic effect of diode laser (810 nm) irradiation on chronic wounds. Eighty-nine patients were enrolled in the study. The control group (41 patients) received traditional dressing change therapy, while the diode laser treatment group (48 patients) were patients received additional treatment with diode laser (810 nm) irradiation for 10 min at each dressing change. Wound healing time was compared between two groups, while the pain relief index was creatively introduced to evaluate the effect of relieving wound pain, which was calculated by the difference in pain scores between the first and last dressing changes divided by the number of treatment days. The wound healing time of the diode laser treatment group was 22.71 ± 8.99 days, which was significantly shorter than that of the control group (37.44 ± 23.42 days). The pain relief index of the diode laser treatment group was 0.081 ± 0.055, which was significantly increased compared with that of the control group (0.057 ± 0.033). Our findings suggest that diode laser irradiation has the potential to promote healing in chronic wounds and relieve wound pain.

The effects of low power laser light at 661 nm on wound healing in a scratch assay fibroblast model

Wound treatment, especially for chronic and infected wounds, has been a permanent socio-economical challenge. This study aimed to investigate the ability of red light at 661 nm to accelerate wound healing an in vitro wound model using 3T3 fibroblasts. The purpose is further specified in clarifying the mechanisms of wound closure by means of intracellular ROS production, proliferation and migration of cells, and cellular orientation. Illumination effects of red light from a diode laser (661 nm) at different doses on 3T3 cell viability was assessed via MTT assay and tested in a scratch wound model. Wound closure rates were calculated by image analysis at 0, 24, and 48 h after laser treatment. ROS production was monitored and quantified immediately and 24 h after the treatment by fluorescence microscopy. Cellular orientation was quantified by image analysis. No phototoxic energy doses used and increased cell viability in most of the groups. Scratch assay revealed an energy interval of 3 - 4.5 J/cm2 that promote higher wound healing rate 24 h post treatment. An increase in ROS production was also observed 24 h post irradiation higher in the group with the highest wound healing rate. Also, cellular orientation toward the margin of the wound was observed and quantified after irradiation. Low power laser light at 661 nm activated both the migration and proliferation in the in vitro model used, providing evidence that it could also accelerate wound healing in vivo. Also, ROS production and cellular orientation seem to play an important role in wound healing process.

Considerations for the Use of Photobiomodulation in the Treatment of Retinal Diseases

Photobiomodulation (PBM) refers to the beneficial effect produced from low-energy light irradiation on target cells or tissues. Increasing evidence in the literature suggests that PBM plays a positive role in the treatment of retinal diseases. However, there is great variation in the light sources and illumination parameters used in different studies, resulting in significantly different conclusions regarding PBM's therapeutic effects. In addition, the mechanism by which PBM improves retinal function has not been fully elucidated. In this study, we conducted a narrative review of the published literature on PBM for treating retinal diseases and summarized the key illumination parameters used in PBM. Furthermore, we explored the potential molecular mechanisms of PBM at the retinal cellular level with the goal of providing evidence for the improved utilization of PBM in the treatment of retinal diseases.

Smart biomaterials and their potential applications in tissue engineering

Smart biomaterials have been rapidly advancing ever since the concept of tissue engineering was proposed. Interacting with human cells, smart biomaterials can play a key role in novel tissue morphogenesis. Various aspects of biomaterials utilized in or being sought for the goal of encouraging bone regeneration, skin graft engineering, and nerve conduits are discussed in this review. Beginning with bone, this study summarizes all the available bioceramics and materials along with their properties used singly or in conjunction with each other to create scaffolds for bone tissue engineering. A quick overview of the skin-based nanocomposite biomaterials possessing antibacterial properties for wound healing is outlined along with skin regeneration therapies using infrared radiation, electrospinning, and piezoelectricity, which aid in wound healing. Furthermore, a brief overview of bioengineered artificial skin grafts made of various natural and synthetic polymers has been presented. Finally, by examining the interactions between natural and synthetic-based biomaterials and the biological environment, their strengths and drawbacks for constructing peripheral nerve conduits are highlighted. The description of the preclinical outcome of nerve regeneration in injury healed with various natural-based conduits receives special attention. The organic and synthetic worlds collide at the interface of nanomaterials and biological systems, producing a new scientific field including nanomaterial design for tissue engineering.

[Research progress of infrared light promoting wound healing]

At present, current stimulation, ultra-sound, and light therapy have become effective methods to promote wound healing. Among them, infrared light is the most widely used method and is one of the important methods to promote wound healing. The therapeutic effect of infrared light on wounds is related to the effect of photobiomodulation on cells and molecules on the skin surface, but the mechanism by which photobiomodulation of infrared light promotes wound healing has not been fully elucidated. Therefore, it is necessary to study the action characteristics and the mechanism of photo-biomodulation of infrared light in promoting wound healing. This article reviews the effect of different types of infrared light on wound healing and the mechanism of infrared light in promoting wound healing.

Electromagnetic Waves Can Help Improve the Rate of Increase of Milk Feeds Per Day in Premature Infants With Necrotizing Enterocolitis: A Pilot Trial

Objective

To evaluate the effects of electromagnetic waves generated by a commercial medical electromagnetic instrument (trade name, TDP, the Chinese phonetic abbreviation of "Te-ding Dian-ci-bo Pu") as an adjuvant to improve the rate of increase of milk feeds per day by premature infants with necrotizing enterocolitis (NEC).

Methods

This study was a prospective randomized clinical trial. A total of 103 premature infants were diagnosed with NEC II, but there was no need for surgery. The infants were randomly divided into the TDP intervention group and the control group by a randomized method using SPSS 24.0. The patients in the TDP intervention group were treated with TDP irradiation and routine interventions; those in the control group were treated with routine interventions. The rate of increase of milk feeds per day, the time to achieve total gastrointestinal nutrition, the velocity of weight gain, and the complication incidence rate were recorded and compared.

Results

The rate of increase of milk feeds per day in the TDP intervention group was significantly greater than that in the control group [14.51 (11.58~22.11) ml/kg/d vs. 10.15 (6.15~15.87) ml/kg/d, P = 0.002]. Compared to the control group, the time to achieve total gastrointestinal nutrition (21.45 ± 1.87 d vs. 36.43 ± 2.585 d, P = 0.000) and the velocity of weight gain (19.65 ± 15.27% vs. 13.68 ± 7.15%, P = 0.013) in the TDP intervention group were substantially better than those in the control group. The complication incidence rate was not significantly different between the two groups (P > 0.05).

Conclusion

Treatment with TDP-generated electromagnetic waves improved the volume of milk consumed per day in premature infants with NEC II and were conducive to improving their clinical outcomes.

Photobiomodulation at 830 nm Stimulates Migration, Survival and Proliferation of Fibroblast Cells

PURPOSE

Photobiomodulation (PBM) promotes diabetic wound healing by favoring cell survival and proliferation. This study aimed to investigate the potential of PBM in stimulating cellular migration, viability, and proliferation using the transforming growth factor-β1 (TGF-β1)/Smad signaling pathway.

METHODS

The study explored the in vitro effects of near infrared (NIR) light on cell viability (survival) and proliferation as well as the presence of TGF-β1, phosphorylated TGF-β receptor type I (pTGF-βR1) and phosphorylated mothers against decapentaplegic-homolog (Smad)-2/3 (p-Smad2/3) in different fibroblast cell models.

RESULTS

Results show a significant increase in cellular migration in wounded models, and increased viability and proliferation in irradiated cells compared to their respective controls. An increase in the presence of TGF-β1 in the culture media, a reduction in pTGF-βR1 and a slight presence of p-Smad2/3 was observed in the cells.

CONCLUSION

These findings show that PBM at 830 nm using a fluence of 5 J/cm² could induce cell viability, migration and proliferation to favor successful healing of diabetic wounds. This study contributes to the growing body of knowledge on the molecular and cellular effect of PBM and showcases the suitability of PBM at 830 nm in managing diabetic wounds.

The Efficacy of Photobiomodulation Therapy in Improving Tissue Resilience and Healing of Radiation Skin Damage

The increased precision, efficacy, and safety of radiation brachytherapy has tremendously improved its popularity in cancer care. However, an unfortunate side effect of this therapy involves localized skin damage and breakdown that are managed palliatively currently. This study was motivated by prior reports on the efficacy of photobiomodulation (PBM) therapy in improving tissue resilience and wound healing. We evaluated the efficacy of PBM therapy on 36 athymic mice with 125I seed (0.42 mCi) implantation over 60 days. PBM treatments were performed with either red (660 nm) or near-infrared (880 nm, NIR) LEDs irradiance of 40 mW/cm2, continuous wave, fluence of 20 J/cm2 once per week. Animals were evaluated every 7 days with digital imaging, laser Doppler flowmetry, thermal imaging, µPET-CT imaging using 18F-FDG, and histology. We observed that both PBM treatments—red and NIR—demonstrated significantly less incidence and severity and improved healing with skin radionecrosis. Radiation exposed tissues had improved functional parameters such as vascular perfusion, reduced inflammation, and metabolic derangement following PBM therapy. Histological analysis confirmed these observations with minimal damage and resolution in tissues exposed to radiation. To our knowledge, this is the first report on the successful use of PBM therapy for brachytherapy. The results from this study support future mechanistic lab studies and controlled human clinical studies to utilize this innovative therapy in managing side effects from radiation cancer treatments.

Light-induced nitric oxide release in the skin beyond UVA and blue light: Red & near-infrared wavelengths

Nitric oxide (NO) is omnipresent in the body and synthesized by 3 isoenzymes (nNOS, eNOS and iNOS), all detected in human skin. NO can be stored in a pool of compounds readily converted to NO following skin irradiation by UVR and blue light. This non-enzymatic (without NOS involvement) photolytic reaction mobilizes cutaneous stores of NO derivatives to the bloodstream, lowering blood pressure. However, with the likelihood of skin deleterious effects caused by UVR/blue light, safer wavelengths in the red/near-infrared (NIR) spectrum are becoming potential contenders to release cutaneous NO, possibly via NOS temperature-dependent effects. The use of red/NIR light to mobilize NO stores from the body's largest organ (the skin) is auspicious. This review focuses on UVR, blue, red, and NIR spectra and their capacity to release NO in human skin. PubMed and Google Scholar were used as article databases to find relevant publications related to this particular field.

RNAseq analysis of treatment-dependent signaling changes during inflammation in a mouse cutaneous wound healing model

BACKGROUND

Despite proven therapeutic effects in inflammatory conditions, the specific mechanisms of phytochemical therapies are not well understood. The transcriptome effects of Traumeel (Tr14), a multicomponent natural product, and diclofenac, a non-selective cyclooxygenase (COX) inhibitor, were compared in a mouse cutaneous wound healing model to identify both known and novel pathways for the anti-inflammatory effect of plant-derived natural products.

METHODS

Skin samples from abraded mice were analyzed by single-molecule, amplification-free RNAseq transcript profiling at 7 points between 12 and 192 h after injury. Immediately after injury, the wounds were treated with either diclofenac, Tr14, or placebo control (n = 7 per group/time). RNAseq levels were compared between treatment and control at each time point using a systems biology approach.

RESULTS

At early time points (12-36 h), both control and Tr14-treated wounds showed marked increase in the inducible COX2 enzyme mRNA, while diclofenac-treated wounds did not. Tr14, in contrast, modulated lipoxygenase transcripts, especially ALOX12/15, and phospholipases involved in arachidonate metabolism. Notably, Tr14 modulated a group of cell-type specific markers, including the T cell receptor, that could be explained by an overarching effect on the type of cells that were recruited into the wound tissue.

CONCLUSIONS

Tr14 and diclofenac had very different effects on the COX/LOX synthetic pathway after cutaneous wounding. Tr14 allowed normal autoinduction of COX2 mRNA, but suppressed mRNA levels for key enzymes in the leukotriene synthetic pathway. Tr14 appeared to have a broad 'phytocellular' effect on the wound transcriptome by altering the balance of cell types present in the wound.

Photobiomodulation therapy for the prevention of acute radiation dermatitis in breast cancer patients undergoing hypofractioned whole-breast irradiation (LABRA trial)

OBJECTIVES

To evaluate the efficacy of photobiomodulation therapy in breast cancer patients post-lumpectomy undergoing hypofractionated whole-breast irradiation (HF-WBI) for the prevention and management of acute radiodermatitis (ARD).

MATERIALS AND METHODS

A randomized, multicentric clinical trial (LABRA trial, NCT03924011) was set up at the Limburg Oncology Center, including the Jessa Hospital (Hasselt, BE) and Ziekenhuis Oost-Limburg (Genk, BE). A total of 71 breast cancer patients planned to undergo HF-WBI were randomized to one of the two study arms: the control group (n = 32) or the PBM group (n = 39). The PBM group received the standard institutional skincare combined with PBM (2×/week) during the complete radiotherapy (RT) course. Patients in the control group received the standard skincare combined with placebo treatment (2x/week). Patients' skin reactions were evaluated weekly during the RT treatment by using the modified version of the Radiation Therapy Oncology Group (RTOG) criteria.

RESULTS

At week 3 of RT, one patient presented a grade 2 and one patient a grade 3 skin reaction in the control group, while in the PBM group, all patients still presented grade 1 ARD. At the final RT session 28% of the patients presenting grade 2-3 ARD, while in the PBM group 10% presented grade 2 and no grade 3 ARD. PBM reduced the incidence of severe ARD by 18%. However, the difference was not significant (p = 0.053).

CONCLUSION

Based on the LABRA trial results, PBM seems not able to reduce the incidence of severe ARD in breast cancer patients undergoing HF-WBI. Research in a larger patient population is recommended.

Role of E2F1/SPHK1 and HSP27 During Irradiation in a PMA-Induced Inflammatory Model

Background: Sphingosine kinase 1 (SPHK1) and heat shock protein 27 (HSP27) are important for antioxidant and anti-inflammatory effects after red light irradiation in an inflammatory model. Objective: The purpose of the present study was to evaluate whether SPHK1 and HSP27 work independently or are dependent on some other regulator after 625 nm light-emitting diode irradiation in the human keratinocyte (HaCaT) cell line. Methods: Differentially expressed genes (DEGs) were identified between groups with or without 625 nm photobiomodulation (PBM) in the inflammatory model. Potential transcription factors (TFs) of key DEGs were predicted using the iRegulon plugin. The mechanism was investigated by analyzing mRNA and protein expression levels, prostaglandin E2 levels, and intracellular reactive oxygen species (ROS) in phorbol 12-myristate 13-acetate (PMA)-induced HaCaT cells after 625 nm PBM. Results: A total of 6 TFs (e.g., E2F1) and 51 key DEGs (e.g., SPHK1) were identified after 625 nm PBM in PMA-stimulated HaCaT cells. E2F1 worked as a regulator of SPHK1; however, it did not affect HSP27. E2F1 knockdown drastically decreased the SPHK1 expression level and increased the intracellular ROS, as well as the expression levels of inflammation-related proteins in PMA-induced HaCaT cells. In addition, the inhibition of HSP27 decreased the anti-inflammatory effect of 625 nm PBM. Conclusions: E2F1 worked as a TF of SPHK1 and exhibited anti-inflammatory and antioxidative effects through SPHK1 in PMA-induced HaCaT cells after 625 nm PBM. HSP27 is essential for the 625 nm PBM-induced anti-inflammatory function. Therefore, E2F1/SPHK1 and HSP27 could be used as potential biomarkers for anti-inflammatory therapy with 625 nm PBM.

Efficacy of 0.2% hyaluronic acid in the healing of skin abrasions in rats

Acute injuries, such as surgical and traumatic, heal normally in an organized and rapid manner. Studies point to the healing activity of hyaluronic acid in all phases of healing. The aim was to evaluate the effectiveness of hyaluronic acid in skin abrasions on the dorsum of rats to compare to usual products on the market. Seventy-two Wistar rats were subjected to excoriation of approximately 2.0 cm2 on the back by dermabrasion. According to the treatment, 3 groups were established: saline, chlorhexidine digluconate and 0.2% hyaluronic acid for 14 days. Animals were photographed on the 2nd, 7th, 10th and 14th postinjury days, and the index of healing of the abrasions was calculated. Biochemically, myeloperoxidase measurements of skin biopsies in addition to histological studies to assess the crust and epidermal layers were performed. The group treated with hyaluronic acid showed better re-epithelialization from the other groups (p < 0.05) on the 7th and 10th days. For the thickness of the crust, the hyaluronic acid group presented thinner crust than other groups on the 10th and 14th days (p < 0.05), but in the epidermis, no difference was observed between the groups studied. All groups showed an increase in myeloperoxidase enzyme on the 2nd day, but a decreasing on the 7th day. On the 10th day, there was a difference in the hyaluronic acid group compared to the other groups (p < 0.05). The application of 0.2% hyaluronic acid significantly accelerated the re-epithelialization of skin abrasions compared to saline and chlorhexidine digluconate.

Photobiomodulation has rejuvenating effects on aged bone marrow mesenchymal stem cells

The plasticity and proliferative capacity of stem cells decrease with aging, compromising their tissue regenerative potential and therapeutic applications. This decline is directly linked to mitochondrial dysfunction. Here, we present an effective strategy to reverse aging of mouse bone marrow mesenchymal stem cells (BM-MSCs) by restoring their mitochondrial functionality using photobiomodulation (PBM) therapy. Following the characterization of young and aged MSCs, our results show that a near-infrared PBM treatment delivering 3 J/cm2 is the most effective modality for improving mitochondrial functionality and aging markers. Furthermore, our results unveil that young and aged MSCs respond differently to the same modality of PBM: whereas the beneficial effect of a single PBM treatment dissipates within 7 h in aged stem cells, it is lasting in young ones. Nevertheless, by applying three consecutive treatments at 24-h intervals, we were able to obtain a lasting rejuvenating effect on aged MSCs. Our findings are of particular significance for improving autologous stem cell transplantation in older individuals who need such therapies most.

Narrow Band Ultraviolet B Versus Red Light-Emitting Diodes in the Treatment of Facial Acne Vulgaris: A Randomized Controlled Trial

Background: One of the most common dermatological conditions affecting most teenagers is acne. Phototherapy was described as a therapeutic modality with low-side effects of acne vulgaris (AV). Hence, we examined the effects of narrow band ultraviolet B (NBUVB) versus red light-emitting diodes (LEDs) on facial AV. Methods: Forty-five subjects suffering from facial AV mild to a moderate degree were randomly assigned into three groups, 15 subjects within every group. Group A was equipped to NBUVB with 311-313 nm and an initial dose of 250 mJ/cm², thrice a week for 8 weeks, Group B was equipped red LED with wavelengths 633 ± 6 nm and power density of 80 mW/cm², thrice a week for 8 weeks, whereas group C had received the only erythromycin as a control group. Outcome measures included measurement of acne lesion count and degree of severity. Measures at three-time intervals were assessed: baseline, 4 weeks (post I), and 8 weeks (post II). Results: Acne numeral findings revealed a significant variance among groups A, B, and C in favor of group A (p < 0.001). Notable improvements were observed across all three groups (p < 0.001). The degree of adjustment effects indicated a greater increase in group A in comparison with group B (p < 0.01), whereas no statistical variance was detected between group B and group C (p > 0.05). Conclusions: Both NBUVB and red LED were effective in acne treatment; NBUVB, however, revealed a highly efficient treatment than red LED in decreasing the acne lesions count and the improved degree of AV severity as measured by the global investigator's assessment scale. Clinical Trial Registration No. NCT04254601.

Photobiomodulation Response From 660 nm is Different and More Durable Than That From 980 nm

BACKGROUND AND OBJECTIVES

Photobiomodulation (PBM) therapy uses light at various wavelengths to stimulate wound healing, grow hair, relieve pain, and more-but there is no consensus about optimal wavelengths or dosimetry. PBM therapy works through putative, wavelength-dependent mechanisms including direct stimulation of mitochondrial respiration, and/or activation of transmembrane signaling channels by changes in water activity. A common wavelength used in the visible red spectrum is ~660 nm, whereas recently ~980 nm is being explored and both have been proposed to work via different mechanisms. We aimed to gain more insight into identifying treatment parameters and the putative mechanisms involved.

STUDY DESIGN/MATERIALS AND METHODS

Fluence-response curves were measured in cultured keratinocytes and fibroblasts exposed to 660 or 980 nm from LED sources. Metabolic activity was assessed using the MTT assay for reductases. ATP production, a major event triggered by PBM therapy, was assessed using a luminescence assay. To measure the role of mitochondria, we used an ELISA to measure COX-1 and SDH-A protein levels. The respective contributions of cytochrome c oxidase and ATP synthase to the PBM effects were gauged using specific inhibitors.

RESULTS

Keratinocytes and fibroblasts responded differently to exposures at 660 nm (red) and 980 nm (NIR). Although 980 nm required much lower fluence for cell stimulation, the resulting increase in ATP levels was short-term, whereas 660 nm stimulation elevated ATP levels for at least 24 hours. COX-1 protein levels were increased following 660 nm treatment but were unaffected by 980 nm. In fibroblasts, SDH-A levels were affected by both wavelengths, whereas in keratinocytes only 660 nm light impacted SDH-A levels. Inhibition of ATP synthase nearly completely abolished the effects of both wavelengths on ATP synthesis. Interestingly, inhibiting cytochrome c oxidase did not prevent the rise in ATP levels in response to PBM treatment.

CONCLUSION

To the best of our knowledge, this is the first demonstration of differing kinetics in response to PBM therapy at red versus NIR wavelength. We also found cell-type-specific differences in PBM therapy response to the two wavelengths studied. These findings confirm that different response pathways are involved after 660 and 980 nm exposures and suggest that 660 nm causes a more durable response. © 2021 Wiley Periodicals LLC.

The Protective Effects of EMF-LTE against DNA Double-Strand Break Damage In Vitro and In Vivo

With the rapid growth of the wireless communication industry, humans are extensively exposed to electromagnetic fields (EMF) comprised of radiofrequency (RF). The skin is considered the primary target of EMFs given its outermost location. Recent evidence suggests that extremely low frequency (ELF)-EMF can improve the efficacy of DNA repair in human cell-lines. However, the effects of EMF-RF on DNA damage remain unknown. Here, we investigated the impact of EMF-long term evolution (LTE, 1.762 GHz, 8 W/kg) irradiation on DNA double-strand break (DSB) using the murine melanoma cell line B16 and the human keratinocyte cell line HaCaT. EMF-LTE exposure alone did not affect cell viability or induce apoptosis or necrosis. In addition, DNA DSB damage, as determined by the neutral comet assay, was not induced by EMF-LTE irradiation. Of note, EMF-LTE exposure can attenuate the DNA DSB damage induced by physical and chemical DNA damaging agents (such as ionizing radiation (IR, 10 Gy) in HaCaT and B16 cells and bleomycin (BLM, 3 μM) in HaCaT cells and a human melanoma cell line MNT-1), suggesting that EMF-LTE promotes the repair of DNA DSB damage. The protective effect of EMF-LTE against DNA damage was further confirmed by attenuation of the DNA damage marker γ-H2AX after exposure to EMF-LTE in HaCaT and B16 cells. Most importantly, irradiation of EMF-LTE (1.76 GHz, 6 W/kg, 8 h/day) on mice in vivo for 4 weeks reduced the γ-H2AX level in the skin tissue, further supporting the protective effects of EMF-LTE against DNA DSB damage. Furthermore, p53, the master tumor-suppressor gene, was commonly upregulated by EMF-LTE irradiation in B16 and HaCaT cells. This finding suggests that p53 plays a role in the protective effect of EMF-LTE against DNA DSBs. Collectively, these results demonstrated that EMF-LTE might have a protective effect against DNA DSB damage in the skin, although further studies are necessary to understand its impact on human health.

Oxidative stress is involved in LLLT mechanism of action on skin healing in rats

The skin injury healing process involves the main phases of homoeostasis, inflammation, proliferation, and remodeling. The present study aimed to analyze the effects of low-level laser therapy (LLLT) on hematological dynamics, oxidative stress markers, and its relation with tissue healing following skin injury. Wistar rats were divided into control, sham, skin injury, and skin injury LLLT. The biochemical and morphological analyses were performed in the inflammatory (1 and 3 days) and regenerative phases (7, 14, and 21 days) following injury. The skin injury was performed in the dorsal region, between the intrascapular lines, using a surgical punch. LLLT (Al-Ga-In-P, λ=660 nm, energy density of 20 J/cm², 30 mW power, and a time of 40 s) was applied at the area immediately after injury and on every following day according to the experimental subgroups. LLLT maintained hematocrit and hemoglobin levels until the 3rd day of treatment. Surprisingly, LLLT increased total leukocytes levels compared to control until the 3rd day. The effects of LLLT on mitochondrial activity were demonstrated by the significant increase in MTT levels in both inflammatory and regenerative phases (from the 1st to the 7th day), but only when associated with skin injury. The results indicated that LLLT modulated the inflammatory response intensity and accelerated skin tissue healing by a mechanism that involved oxidative damage reduction mostly at early stages of skin healing (inflammatory phase).

Photobiomodulation in diabetic wound healing: A review of red and near-infrared wavelength applications

The development of a painless, non-invasive, and faster way to diabetic wound healing is at the forefront of research. The complexity associated with diabetic wounds makes it a cause for concern amongst diabetic patients and the world at large. Irradiation of cells generates a photobiomodulatory response on cells and tissues, directly causing alteration of cellular processes and inducing diabetic wound repair. Photobiomodulation therapy (PBMT) using red and near-infrared (NIR) wavelengths is being considered as a promising technique for speeding up the rate of diabetic wound healing, eradication of pain and reduction of inflammation through the alteration of diverse cellular and molecular processes. This review presents the extent to which the potential of red and NIR wavelengths have been harnessed in PBMT for diabetic wound healing. Important research challenges and gaps are identified and discussed, and future directions mapped out. This review thus provides useful insights and strategies into improvement of PBMT, including its acceptance within the global medical research community.

Effects of Buprenorphine, Chlorhexidine, and Low-level Laser Therapy on Wound Healing in Mice

Systemic buprenorphine and topical antiseptics such as chlorhexidine are frequently used in research animals to aid in pain control and to reduce infection, respectively. These therapeutics are controversial, especially when used in wound healing studies, due to conflicting data suggesting that they delay wound healing. Low-level laser therapy (LLLT) has been used to aid in wound healing without exerting the systemic effects of therapies such as buprenorphine. We conducted 2 studies to investigate the effects of these common treatment modalities on the rate of wound healing in mice. The first study used models of punch biopsy and dermal abrasion to assess whether buprenorphine HCl or 0.12% chlorhexidine delayed wound healing. The second study investigated the effects of sustained-released buprenorphine, 0.05% chlorhexidine, and LLLT on excisional wound healing. The rate of wound healing was assessed by obtaining photographs on days 0, 2, 4, 7, and 9 for the punch biopsy model in study 1, days 0, 1, 2, 4, 6, 8, 11, and 13 for the dermal abrasion model in study 1, and days 0, 3, 6, and 10 for the mice in study 2. Image J software was used to analyze the photographed wounds to determine the wound area. When comparing the wound area on the above days to the original wound area, no significant differences in healing were observed for any of the treatment groups at any time period for either study. Given the results of these studies, we believe that systemic buprenorphine, topical chlorhexidine, and LLLT can be used without impairing or delaying wound healing in mice.

Comparison of photobiomodulation in the treatment of skin injury with an open wound in mice

This study aimed to investigate the effects of photobiomodulation at a wavelength of 660 and 830 nm at different numbers of application points in the healing of open wounds in mice. In total, 120 mice were divided into 10 groups. The animals were submitted to cutaneous lesion of the open wound type (1.5 × 1.5 cm). Photobiomodulation at a wavelength of 660 and 830 nm and total energy of 3.6 J were used, applied at 1, 4, 5, and 9 points, for 14 days. The animals were subjected to analysis of the lesion area, skin temperature, and histological analysis. Macroscopic analysis results showed a difference (p < 0.05) between the irradiated groups and the sham group at 14 days PO. There was no statistical difference in skin temperature. Histological analysis findings showed better results for the epidermis thickness. Regarding the number of blood vessels, a difference was found between the 1- and 5-point 830-nm photobiomodulation groups and between the 4-point 660-nm group and the naive group. A significant difference in the number of fibroblasts was observed between the 830- and 660-nm photobiomodulation groups and the naive and sham groups. When comparing photobiomodulation wavelength, the 830-nm groups were more effective, and we emphasize the groups irradiated at 5 points, which showed an improvement in macroscopic analysis and epidermis thickness, an increase in the number of vessels, and a lower number of fibroblasts on the 14th day after skin injury.

An injectable photothermally active antibacterial composite hydroxypropyl chitin hydrogel for promoting the wound healing process through photobiomodulation

Prevention of bacterial infection, acceleration of wound closure and promotion of skin regeneration are crucial in the wound healing process. In this work, the photothermal activity of an injectable thermosensitive composite hydrogel based on hydroxypropyl chitin (HPCH), tannic acid (TA) and ferric ions (Fe3+) was studied. It was found that the photothermal efficiency was enhanced when the molar ratio of Fe3+/TA increased up to 20. The composite hydrogel possessed good cytocompatibility and hemocompatibility with a low dosage of the antibacterial agent TA. In vitro and in vivo antibacterial tests showed that the HPCH/TA/Fe hydrogel possessed an effective and rapid bactericidal effect with 10 minutes of near-infrared laser irradiation. Furthermore, the combination of a low-level laser therapy with the hydrogel is conducive to the acceleration of wound closure and promotion of skin tissue repair. Thus, the injectable photothermally active antibacterial composite hydrogel has great potential for the infected skin wound regeneration in clinical applications.

Photobiomodulation invigorating collagen deposition, proliferating cell nuclear antigen and Ki67 expression during dermal wound repair in mice

The present investigation focuses on understanding the role of photobiomodulation in enhancing tissue proliferation. Circular excision wounds of diameter 1.5 cm were created on Swiss albino mice and treated immediately with 2 J/cm² and 10 J/cm² single exposures of the Helium-Neon laser along with sham-irradiated controls. During different days of healing progression (day 5, day 10, and day 15), the tissue samples upon euthanization of the animals were taken for assessing collagen deposition by Picrosirius red staining and cell proliferation (day 10) by proliferating cell nuclear antigen (PCNA) and Ki67. The positive influence of red light on collagen synthesis was found to be statistically significant on day 10 (P < 0.01) and day 15 (P < 0.05) post-wounding when compared to sham irradiation, as evident from the image analysis of collagen birefringence. Furthermore, a significant rise in PCNA (P < 0.01) and Ki67 (P < 0.05) expression was also recorded in animals exposed to 2 J/cm² when compared to sham irradiation and (P < 0.01) compared to the 10 J/cm² treated group as evidenced by the microscopy study. The findings of the current investigation have distinctly exhibited the assenting influence of red laser light on excisional wound healing in Swiss albino mice by augmenting cell proliferation and collagen deposition.

Immunomodulatory activity seen as a result of photobiomodulation therapy in stimulated primary human fibroblasts

OBJECTIVE

Oral biofilms burden host responses by induction of inflammatory mediators, exacerbating periodontal inflammation. Photobiomodulation Therapy (PBMT) has been shown to decrease levels of pro-inflammatory cytokines and chemokines. However, optimal wavelengths and exposure doses have not been established. This study investigated the effects of PBMT on human periodontal ligament fibroblasts (hPDLFs) stimulated with inflammatory mediators (LPS, TNF-α, and IL-1β).

METHODS

Cytotoxic effects of laser wavelengths 660 nm and 810 nm were assessed by measuring their effects on cellular dehydrogenase activity. The study was expanded to include 980 nm, 660 nm + 810 nm, and 810 nm + 980 nm. P.g. LPS, TNF-α, and/or IL-1β were added one hour before irradiation, then exposed to laser irradiation to determine the most appropriate stimulus. The levels of INF-γ, IL-6, IL-8, IL-17A/F, and MCP-1 production in stimulated hPDLFs were measured and analyzed.

RESULTS

P.g. LPS was a poor stimulus for hPDLFs, while TNF-α and IL-1β significantly elevated the analytes. The 660 nm laser treatment induced pro-inflammatory cytokines when stimulated, while 810 nm exhibited significant suppression. IL-1β was the stimulus of choice and the 810 nm wavelength alone exhibited anti-inflammatory effects for all analytes except IL-8, while the 810 nm in combination with 660 nm and/or 980 nm exhibited effects similar to 810 nm alone.

CONCLUSIONS

The downregulation of inflammatory mediators by the combination or individual treatment with 810 nm wavelength shows promise for the management of periodontal inflammation. PBMT may lead to the development of a novel approach in the management of periodontal disease.

Effect of different treatments on recurrent aphthous stomatitis: laser versus medication

Recurrent aphthous stomatitis (RAS) is a common disease with ulcers in oral cavity which may trigger chewing, speaking, and swallowing difficulties to patients. Treatment of RAS is primarily aimed at pain relief and the promotion of wound healing. However, few agents have been found to have definite effect in the management of RAS and most of the medicinal products may cause adverse reactions or other disadvantages, which makes their clinical usage questionable. The purpose of this randomized controlled clinical trial (RCT) was to assess the clinical effect of diode laser and traditional medication treatment on RAS. In this study, 56 patients were randomly assigned to two groups (n = 28). Laser group was treated using diode laser (810 nm, 1.0 W, CW, irradiation time 20 s for 3 applications) once daily for continuous 3 days. Medication group was treated with triamcinolone acetonide 0.1% three times a day until the lesion was healed. Spontaneous and functional pain level on the third day of treatment was significantly less in the laser group. Significant difference was observed with respect to healing time; however, the order of difference is small albeit of statistical significance. Diode laser with the chosen parameters had better effects on pain relief and no distinct advantage on wound healing comparing with medication. Trial registration number: ChiCTR2000030298; date of registration: 26 February 2020 (retrospectively registered).

Various biological effects of solar radiation on skin and their mechanisms: implications for phototherapy

The skin protects our body from various external factors, such as chemical and physical stimuli, microorganisms, and sunlight. Sunlight is a representative environmental factor that considerably influences the physiological activity of our bodies. The molecular mechanisms and detrimental effects of ultraviolet rays (UVR) on skin have been thoroughly investigated. Chronic exposure to UVR generally causes skin damage and eventually induces wrinkle formation and reduced elasticity of the skin. Several studies have shown that infrared rays (IR) also lead to the breakdown of collagen fibers in the skin. However, several reports have demonstrated that the appropriate use of UVR or IR can have beneficial effects on skin-related diseases. Additionally, it has been revealed that visible light of different wavelengths has various biological effects on the skin. Interestingly, several recent studies have reported that photoreceptors are also expressed in the skin, similar to those in the eyes.

Based on these data, I discuss the various physiological effects of sunlight on the skin and provide insights on the use of phototherapy, which uses a specific wavelength of sunlight as a non-invasive method, to improve skin-related disorders.

Photobiomodulation therapy improves the growth factor and cytokine secretory profile in human type 2 diabetic fibroblasts

Impaired wound healing is a common complication of diabetes mellitus (DM) and the underlying mechanism of this impairment is still unclear. Fibroblast, as the main reconstructing cell, secretes some critical growth factors and cytokine contributing to wound healing. It is well known that DM alters the behavior of these cells and photobiomodulation therapy (PBMT) compensates some impairments in diabetic fibroblasts. Therefore, the aim of the present study was to demonstrate the impact of diabetes and the role of PBMT through low level laser irradiation on secretory profile of human diabetic fibroblasts. Primary human dermal fibroblasts from normal (HDFs) and diabetic (DHDFs) donors were harvested. For PBMT, the DHDFs were irradiated with a Helium-Neon laser at 632.8 nm wavelength and energy density of 0.5 J/cm², as laser treated group (LT-DHDFs). Next, some cellular behaviors and secretory profiling array for 60 growth factors/cytokines were investigated in LT-DHDFs and then compared with those of controls. The data showed that the PBMT could compensate such impairments occurred in DHDFs in terms of viability, proliferation, and migration. Furthermore, considering our novel findings, out of those 20 growth factors/cytokines involved in cell proliferation, immune system regulation, and cell-cell communication pathways, which significantly decreased in DHDF as compared with HDFs, the PBMT could compensate seven in LT-DHDFs as compared with DHDFs. The seven growth factor/cytokines, which are mainly involved in cell-cell communication, positive regulation of cell proliferation, and chemokine mediated pathway included BDNF, Eotaxin-3, FGF6, FGF7, Fractalkine, fit-3ligand, and GCP-2. Therefore, it is suggested that scrutinizing these differentially secreted molecules and the impaired pathways in DHDFs, in combination with those compensated in LT-DHDFs, could raise our knowledge to manage diabetic ulcer through a feasible and cost effective intervention, specifically PBMT.

Topical sodium alendronate combined or not with photodynamic therapy as an adjunct to scaling and root planing: Histochemical and immunohistochemical study in rats

OBJECTIVE

The purpose of this study was to evaluate influence of topical sodium alendronate (ALN), photodynamic therapy (aPDT), or a combination thereof as adjuvant to scaling and root planing (SRP) in the treatment of experimental periodontitis in rats.

BACKGROUND

Therapeutic protocols to control periodontitis progression that aim to equalize bacterial action and load with tissue immune response are well addressed in current scientific research.

METHODS

Experimental periodontitis was induced in 96 rats with a ligature around the mandibular left first molar. After 7 days, ligature was removed and animals were treated according to the following experimental groups (n = 8): control-SRP plus saline solution; ALN-SRP plus ALN; aPDT-SRP plus methylene blue irrigation, followed by low-level laser therapy (LLLT); and ALN/aPDT-SRP plus ALN and methylene blue irrigation followed by LLLT. The animals were euthanized at 7, 15, and 30 days after treatments. Collagen maturation (picrosirius red staining) and immunohistochemical analyses (TRAP, RANKL and osteoprotegerin [OPG]) were performed. Data were submitted to statistical analysis (P < .05).

RESULTS

At 7 days, group ALN presented a significantly higher number of TRAP-positive cells and percentage of immature collagen fibers than group ALN/aPDT, while group ALN/aPDT presented a significantly higher percentage of mature collagen fibers than group ALN. At 30 days, group ALN presented significantly lower percentage of immature collagen fibers and higher percentage of mature collagen fibers than control.

CONCLUSION

It can be concluded that topical use of ALN coadjutant to SRP, alone or combined with aPDT, enhanced collagen maturation and reduced osteoclastogenesis during the healing of experimental periodontitis.

Healing effects of natural latex serum 1% from Hevea brasiliensis in an experimental skin abrasion wound model

Background

Dermabrasion is related with mechanical and surgical traumas on the skin; usually topical antiseptics and/or saline have been used for healing. Natural products for wound healing can also be used for abrasions, such as latex from Hevea brasiliensis.

Objective

This study aimed to evaluate the in vitro viability and migratory/proliferative effects of latex serum from H. brasiliensis and to compare with a commercially available standard antiseptic solution and saline in experimental dermabrasion on rats.

Methods

For in vitro evaluation, MTT and scratch assays were used. In vivo testing was performed in 72 rats submitted to dermabrasion, treated with saline, antiseptic, or latex serum. This study evaluated re-epithelialization, neutrophilic infiltration, and the quantification of crust and epidermis.

Results

Latex showed viability at 1% and 0.1% concentrations and migratory/proliferative activity at 0.01% concentrations. The re-epithelialization was highest in latex group on 7th day. The latex group displayed lower thickness of crusts and greater extent of epidermal layers. The latex and antiseptic groups showed increases of myeloperoxidase levels on the 2nd day and showed important reductions from the 7th day.

Study limitations

Acute superficial wound model in rats and non-use of gel-cream (medium) without latex.

Conclusion

In conclusion, non-toxic latex stimulated migration/proliferation of keratinocytes in vitro and significantly accelerated wound healing in animal excoriation models compared to chlorhexidine or saline.