Photobiomodulation of human adipose-derived stem cells using 810nm and 980nm lasers operates via different mechanisms of action

Photobiomodulation: a novel approach to promote trans-differentiation of adipose-derived stem cells into neuronal-like cells

JOURNAL/nrgr/04.03/01300535-202502000-00035/figure1/v/2024-05-28T214302Z/r/image-tiff Photobiomodulation, originally used red and near-infrared lasers, can alter cellular metabolism. It has been demonstrated that the visible spectrum at 451-540 nm does not necessarily increase cell proliferation, near-infrared light promotes adipose stem cell proliferation and affects adipose stem cell migration, which is necessary for the cells homing to the site of injury. In this in vitro study, we explored the potential of adipose-derived stem cells to differentiate into neurons for future translational regenerative treatments in neurodegenerative disorders and brain injuries. We investigated the effects of various biological and chemical inducers on trans-differentiation and evaluated the impact of photobiomodulation using 825 nm near-infrared and 525 nm green laser light at 5 J/cm2. As adipose-derived stem cells can be used in autologous grafting and photobiomodulation has been shown to have biostimulatory effects. Our findings reveal that adipose-derived stem cells can indeed trans-differentiate into neuronal cells when exposed to inducers, with pre-induced cells exhibiting higher rates of proliferation and trans-differentiation compared with the control group. Interestingly, green laser light stimulation led to notable morphological changes indicative of enhanced trans-differentiation, while near-infrared photobiomodulation notably increased the expression of neuronal markers. Through biochemical analysis and enzyme-linked immunosorbent assays, we observed marked improvements in viability, proliferation, membrane permeability, and mitochondrial membrane potential, as well as increased protein levels of neuron-specific enolase and ciliary neurotrophic factor. Overall, our results demonstrate the efficacy of photobiomodulation in enhancing the trans-differentiation ability of adipose-derived stem cells, offering promising prospects for their use in regenerative medicine for neurodegenerative disorders and brain injuries.

Exploring the biphasic dose-response effects of photobiomodulation on the viability, migration, and extracellular vesicle secretion of human adipose mesenchymal stem cells

Photobiomodulation (PBM) is a well-established medical technology that employs diverse light sources like lasers or light-emitting diodes to generate diverse photochemical and photophysical reactions in cells, thereby producing beneficial clinical outcomes. In this study, we introduced an 830 nm near-infrared (NIR) laser irradiation system combined with a microscope objective to precisely and controllably investigate the impact of PBM on the migration and viability of human adipose mesenchymal stem cells (hADSCs). We observed a biphasic dose-response in hADSCs' viability and migration after PBM exposure (0-10 J/cm2), with the 5 J/cm2 group showing significantly higher cell viability and migration ability than other groups. Additionally, at the optimal dose of 5 J/cm2, we used nanoparticle tracking analysis (NTA) and found a 6.25-fold increase in the concentration of extracellular vesicles (EVs) derived from hADSCs (PBM/ADSC-EVs) compared to untreated cells (ADSC-EVs). Both PBM/ADSC-EVs and ADSC-EVs remained the same size, with an average diameter of 56 nm measured by the ExoView R200 system, which falls within the typical size range for exosomes. These findings demonstrate that PBM not only improves the viability and migration of hADSCs but also significantly increases the EV yield.

The role of photobiomodulation in accelerating bone repair

Bone repair is faced with obstacles such as slow repair rates and limited bone regeneration capacity. Delayed healing even nonunion could occur in bone defects, influencing the life quality of patients severely. Photobiomodulation (PBM) utilizes different light sources to derive beneficial therapeutic effects with the advantage of being non-invasive and painless, providing a promising strategy for accelerating bone repair. In this review, we summarize the parameters, mechanisms, and effects of PBM regulating bone repair, and further conclude the current clinical application of PBM devices in bone repair. The wavelength of 635-980 nm, the output power of 40-100 mW, and the energy density of less than 100 J/cm2 are the most commonly used parameters. New technologies, including needle systems and biocompatible and implantable optical fibers, offer references to realize an efficient and safe strategy for bone repair. Further research is required to establish the reliability of outcomes from in vivo and in vitro studies and to standardize clinical trial protocols.

Combined Light and Thermal Stimulation of Bone Marrow Stem Cells

Introduction: The purpose of this study is to achieve a significant increase in the proliferative activity of mesenchymal stem cells (MSCs) of the bone marrow (BM) at early passages after laser exposure to a suspension of these cells and to estimate the effect of light and heat components of laser radiation on the proliferation of BM MSCs. Methods: The studies were performed on rats BM MSCs. MSC suspension was placed into the wells and heated by using laser radiation (980 nm wavelength) or a water bath at 70 °C providing similar temperature dynamics. The studies were carried out in 3 comparison groups: (1) control suspension of MSCs, which was not subjected to heating in a water bath or laser exposure; (2) MSC suspension, which was heated for in a water bath; and (3) suspension of MSCs, which was subjected to laser exposure. The exposure times for the 2nd and 3rd experimental groups were 10- 50 seconds. Results: Under optimal parameters of laser action on the suspension of BM MSCs, a six-fold increase in the number of BM MSCs colonies was registered compared to the control. The role of the light and heat components of laser exposure to MSCs was determined by comparable heating of a suspension of BM MSCs in a water bath, at which only a twofold increase in the number of colonies was maximally obtained. Conclusion: The increase in the MSC proliferation activity occurs due to their Thermo-Photobiomodulation. The result obtained is important for practical use in cell transplantation in the treatment of traumatic injuries of bone, cartilage, and tendon tissues when a rapid and multiple increase in the initial number of autologous BM MSCs is required.

Neutrophil response to Porphyromonas gingivalis is modulated by low-level laser application

OBJECTIVES

Neutrophil response is critical in inflammatory regulation and immune response to bacterial infections. During periodontal disease, pathogenic bacteria lead to exaggerated neutrophil responses. We hypothesized that low-level laser application (LLLT), therapeutic strategy for dampening inflammatory processes, will regulate neutrophil activity in response to periodontopathogens.

MATERIALS AND METHODS

The impact of LLLT on neutrophil responses was measured by light delivered at wavelength of 850 nm. The direct effect of LLLT on P. gingivalis A7436 was determined by flow cytometry using LIVE/DEADTM Cell Vitality kit. The phagocytosis of P. gingivalis A7436 by human neutrophils was measured using flow cytometry. Superoxide generation was measured by cytochrome-C-reduction in the presence of N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP; 1 mM). Cytokine release by neutrophils was measured by multiplex immunoassay.

RESULTS

The phagocytosis of P. gingivalis by primary human neutrophils was significantly reduced in response to LLLT (p < 0.05). While LLLT led to increased superoxide production in neutrophils that were not challenged by P. gingivalis, it dampened the increased superoxide and IL-6 release by the neutrophils in response to P. gingivalis. LLLT did not directly affect the viability of P. gingivalis.

CONCLUSION

These results suggested that LLLT can provide therapeutic strategy in periodontal disease, regulating the neutrophil response to P. gingivalis.

Fibroblast function recovery through rejuvenation effect of nanovesicles extracted from human adipose-derived stem cells irradiated with red light

Fibroblasts (hDFs) are widely employed for skin regeneration and the treatment of various skin disorders, yet research were rarely investigated about restoration of diminished therapeutic efficacy due to cell senescence. The application of stem cell and stem cell-derived materials, exosomes, were drawn attention for the restoration functionality of fibroblasts, but still have limitation for unintended side effect or low yield. To advance, stem cell-derived nanovesicle (NV) have developed for effective therapeutic reagents with high yield and low risk. In this study, we have developed a method using red light irradiated human adipose-derived stem cells (hADSCs) derived NV (R-NVs) for enhancing the therapeutic efficacy and rejuvenating hDFs. Through red light irradiation, we were able to significantly increase the content of stemness factors and angiogenic biomolecules in R-NVs. Treatment with these R-NVs was found to enhance the migration ability and leading to rejuvenation of old hDFs to levels similar to those of young hDFs. In subsequent in vivo experiments, the treatment of old hDFs with R-NVs demonstrated a superior skin wound healing effect, surpassing that of young hDFs. In summary, this study successfully induced rejuvenation and leading to increased therapeutic efficacy to R-NVs treated old hDFs previously considered as biowaste.

Traumatic Brain Injury Recovery with Photobiomodulation: Cellular Mechanisms, Clinical Evidence, and Future Potential

Traumatic Brain Injury (TBI) remains a significant global health challenge, lacking effective pharmacological treatments. This shortcoming is attributed to TBI's heterogeneous and complex pathophysiology, which includes axonal damage, mitochondrial dysfunction, oxidative stress, and persistent neuroinflammation. The objective of this study is to analyze transcranial photobiomodulation (PBM), which employs specific red to near-infrared light wavelengths to modulate brain functions, as a promising therapy to address TBI's complex pathophysiology in a single intervention. This study reviews the feasibility of this therapy, firstly by synthesizing PBM's cellular mechanisms with each identified TBI's pathophysiological aspect. The outcomes in human clinical studies are then reviewed. The findings support PBM's potential for treating TBI, notwithstanding variations in parameters such as wavelength, power density, dose, light source positioning, and pulse frequencies. Emerging data indicate that each of these parameters plays a role in the outcomes. Additionally, new research into PBM's effects on the electrical properties and polymerization dynamics of neuronal microstructures, like microtubules and tubulins, provides insights for future parameter optimization. In summary, transcranial PBM represents a multifaceted therapeutic intervention for TBI with vast potential which may be fulfilled by optimizing the parameters. Future research should investigate optimizing these parameters, which is possible by incorporating artificial intelligence.

Photobiomodulation therapy's impact on angiogenesis and osteogenesis in orthodontic tooth movement: in vitro and in vivo study

BACKGROUND

This study explores the effectiveness of Photobiomodulation Therapy (PBMT) in enhancing orthodontic tooth movement (OTM), osteogenesis, and angiogenesis through a comprehensive series of in vitro and in vivo investigations. The in vitro experiments involved co-culturing MC3T3-E1 and HUVEC cells to assess PBMT's impact on cell proliferation, osteogenesis, angiogenesis, and associated gene expression. Simultaneously, an in vivo experiment utilized an OTM rat model subjected to laser irradiation at specific energy densities.

METHODS

In vitro experiments involved co-culturing MC3T3-E1 and HUVEC cells treated with PBMT, enabling a comprehensive assessment of cell proliferation, osteogenesis, angiogenesis, and gene expression. In vivo, an OTM rat model was subjected to laser irradiation at specified energy densities. Statistical analyses were performed to evaluate the significance of observed differences.

RESULTS

The results revealed a significant increase in blood vessel formation and new bone generation within the PBMT-treated group compared to the control group. In vitro, PBMT demonstrated positive effects on cell proliferation, osteogenesis, angiogenesis, and gene expression in the co-culture model. In vivo, laser irradiation at specific energy densities significantly enhanced OTM, angiogenesis, and osteogenesis.

CONCLUSIONS

This study highlights the substantial potential of PBMT in improving post-orthodontic bone quality. The observed enhancements in angiogenesis and osteogenesis suggest a pivotal role for PBMT in optimizing treatment outcomes in orthodontic practices. The findings position PBMT as a promising therapeutic intervention that could be seamlessly integrated into orthodontic protocols, offering a novel dimension to enhance overall treatment efficacy. Beyond the laboratory, these results suggest practical significance for PBMT in clinical scenarios, emphasizing its potential to contribute to the advancement of orthodontic treatments. Further exploration of PBMT in orthodontic practices is warranted to unlock its full therapeutic potential.

A comprehensive review on therapeutic potentials of photobiomodulation for neurodegenerative disorders

A series of experimental trials over the past two centuries has put forth Photobiomodulation (PBM) as a treatment modality that utilizes colored lights for various conditions. While in its cradle, PBM was used for treating simple conditions such as burns and wounds, advancements in recent years have extended the use of PBM for treating complex neurodegenerative diseases (NDDs). PBM has exhibited the potential to curb several symptoms and signs associated with NDDs. While several of the currently used therapeutics cause adverse side effects alongside being highly invasive, PBM on the contrary, seems to be broad-acting, less toxic, and non-invasive. Despite being projected as an ideal therapeutic for NDDs, PBM still isn't considered a mainstream treatment modality due to some of the challenges and knowledge gaps associated with it. Here, we review the advantages of PBM summarized above with an emphasis on the common mechanisms that underlie major NDDs and how PBM helps tackle them. We also discuss important questions such as whether PBM should be considered a mainstay treatment modality for these conditions and if PBM's properties can be harnessed to develop prophylactic therapies for high-risk individuals and also highlight important animal studies that underscore the importance of PBM and the challenges associated with it. Overall, this review is intended to bring the major advances made in the field to the spotlight alongside addressing the practicalities and caveats to develop PBM as a major therapeutic for NDDs.

Recent advances in light energy biotherapeutic strategies with photobiomodulation on central nervous system disorders

Transcranial photobiomodulation refers to irradiation of the brain through the skull using low-intensity red or near-infrared light, which is the most commonly studied method of light energy biotherapy for central nervous system disorders. The absorption of photons by specific chromophores within the cell elevates ATP synthesis, reduces oxidative stress damage, alleviates inflammation or mediates the activation of transcription factors and signaling mediators through secondary mediators, which in turn trigger downstream signaling pathways to cause a series of photobiological effects including upregulation of neurotrophic factors. Multiple mechanisms are simultaneously involved in the pathological process of central nervous system disorders. The pleiotropic treatment of transcranial photobiomodulation towards multiple targets plays a beneficial role in improving hemodynamics, neural repair and improving behaviors in central nervous system disorders such as ischemic stroke, traumatic brain injury, neurodegenerative diseases, epilepsy and depression. This review mainly introduces the mechanism and recent preclinical and clinical advances of transcranial photobiomodulation for central nervous system disorders, which will provide a reference for clinicians to understand and engage in related studies, and calls for more and larger studies to validate and develop a wider application of transcranial photobiomodulation in central nervous system.

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 Effects on Periodontal Ligament Stem Cells: A Systematic Review of In Vitro Studies

BACKGROUND

Stem cell therapy has been considered to play a paramount role in the treatment modalities available for regenerative dentistry. The established beneficial effects of photobiomodulation (PBM) at the cellular level have led to the combined use of these two factors (PBM and stem cells). The main goal of this study was firstly to critically appraise the effects of PBM on periodontal ligament stem cells (PDLSCs), and secondly to explore the most effective PBM protocols applied.

METHODS

Pubmed, Cochrane, Scopus, Science Direct, and Google Scholar search engines were used to identify experimental in vitro studies in which PBM was applied to cultured PDLSCs. After applying specific keywords, additional filters, and inclusion/exclusion criteria, a preliminary number of 245 articles were narrowed down to 11 in which lasers and LEDs were used within the 630 - 1064 nm wavelength range. Selected articles were further assessed by three independent reviewers for strict compliance with PRISMA guidelines, and a modified Cochrane risk of bias to determine eligibility.

STATISTICAL ANALYSIS

The dataset analysed was extracted from the studies with sufficient and clearly presented PBM protocols. Simple univariate regression analysis was performed to explore the significance of contributions of potential quantitative predictor variables toward study outcomes, and a one-way ANOVA model was employed for testing differences between the laser or LED sources of the treatments. The significance level for testing was set at α = 0.05.

RESULTS

The proliferation rate, osteogenic differentiation, and expression of different indicative genes for osteogenesis and inflammation suppression were found to be positively affected by the application of various types of lasers and LEDs. With regard to the PBM protocol, only the wavelength variable appeared to affect the treatment outcome; indeed, the 940 nm wavelength parameter was found not to exert a favourable effect.

CONCLUSIONS

Photobiomodulation can enhance the stemness and differentiation capacities of periodontal ligament stem cells. Therefore, for PBM protocols, there remains no consensus amongst the scientific community. Statistical analyses performed here indicated that the employment of a near-infrared (NIR) wavelength of 940 nm may not yield a significant favourable outcome, although those within the 630 - 830 nm range did so. Concerning the fluence, it should not exceed 8 J/cm2 when therapy is applied by LED devices, and 4 J/cm2 when applied by lasers, respectively.

In Vitro Effect of Photobiomodulation Therapy with 980 nm Diode Laser on Gene Expression of Key Regulators of Bone Remodeling by Human Periodontal Ligament Cells under Mild Orthodontic Forces

This study investigated the effect of photobiomodulation (PBM) with 980 nm diode laser as monotherapy and in combination with compressive and tensile orthodontic forces on expression of osteoprotegerin (OPG), receptor activator of nuclear factor-κB ligand (RANKL), sclerostin (SOST) and periostin (POSTN), by human periodontal ligament cells. Isolated cells were cultured and subjected to either tensile (10% elongation) or compressive forces (25 g cm-2 ) for 24 and 48 h. Subsequently, the cells received PBM (100 mW power, 3 or 6 J cm-2 energy density) immediately after load cycle. RT-PCR was applied to assess the genes expression. Data were analyzed by one-way ANOVA, followed by post hoc Tukey test (P ≤ 0.05). We found that PBM in combination with orthodontic forces led to upregulation of bone resorption genes (RANKL and SOST) at the pressure side and their downregulation at the tension side. The expression of osteogenic genes (OPG and POSTN) increased at the tension side and decreased at the pressure side. PBM alone did not affect gene expression. In conclusion, these findings suggest that this PBM protocol may be effective in enhancement of the gene expression in favor of bone remodeling acceleration that should be confirmed in future animal and human studies.

Glucose Improves the Efficacy of Photobiomodulation in Changing ATP and ROS Levels in Mouse Fibroblast Cell Cultures

In this study, we tested the idea that photobiomodulation-the application of red to near infrared light (~λ = 600-1300 nm) to body tissues-is more effective in influencing cell metabolism when glucose is readily available. To this end, we used a mouse fibroblast (L-929) cell culture model and had two sets of conditions: non-stressed (10% FBS (foetal bovine serum)) and stressed (1% FBS), both either with or without glucose. We treated (or not) cells with photobiomodulation using an 810 nm laser at 15 mW/cm2 (~7.2 J/cm2). Our results showed that photobiomodulation was neither cytotoxic nor effective in enhancing measures of cell viability and proliferation, together with protein levels in any of the cell cultures. Photobiomodulation was, however, effective in increasing adenosine triphosphate (ATP) and decreasing reactive oxygen species (ROS) levels and this was-most importantly-only in conditions where glucose was present; corresponding cultures that did not contain glucose did not show these changes. In summary, we found that the benefits of photobiomodulation, in particular in changing ATP and ROS levels, were induced only when there was glucose available. Our findings lay a template for further explorations into the mechanisms of photobiomodulation, together with having considerable experimental and clinical implications.

Wavelength-tunable broadband lasers based on nanomaterials

Nanomaterials are widely used in the fields of sensors, optoelectronics, biophotonics and ultrafast photonics due to their excellent mechanical, thermal, optical, electrical and magnetic properties. Particularly, owing to their nonlinear optical properties, fast response time and broadband operation, nanomaterials are ideal saturable absorption materials in ultrafast photonics, which contribute to the improvement of laser performance. Therefore, nanomaterials are of great importance to applications in wavelength-tunable broadband pulsed lasers. Herein, we review the integration and applications of nanomaterials in wavelength-tunable broadband ultrafast photonics. Firstly, the two integration methods, which are direct coupling and evanescent field coupling, and their characteristics are introduced. Secondly, the applications of nanomaterials in wavelength-tunable broadband lasers are summarized. Finally, the development of nanomaterials and broadband tunable lasers is reviewed and discussed.

Dual-NIR wavelength (pulsed 810 nm and superpulsed 904 nm lasers) photobiomodulation therapy synergistically augments full-thickness burn wound healing: A non-invasive approach

A thermal burn is the most frequent, distressing form of trauma. Globally, there is a critical necessity to explore novel therapeutic strategies for burn wound care. Combination therapy has marked therapeutic efficacy in positively regulating various phases of wound repair. Photobiomodulation (PBM) is a biophysical, non-thermal therapeutic healing modality to treat chronic non-healing wounds. It hypothesized that PBM using combined NIR wavelengths may absorb through different cellular photoacceptors with varying degrees of tissue penetration, which can potentially regulate the pace of healing. Therefore, the current study investigates the efficacy of dual-NIR wavelength treatment employing pulsed 810 nm and superpulsed 904 nm lasers PBM on transdermal burn repair in rats and unveils the associated molecular mechanistic insights. Rats were randomized into five groups: uninjured skin, burn control (sham-exposed), standalone treatment with pulsed 810 nm laser, superpulsed 904 nm laser, and dual combination groups. The present findings revealed that PBM with dual-NIR wavelength synergistically augmented burn wound healing compared to control and standalone treatments. The efficacy of combined treatment was exhibited by significantly enhanced wound area contraction (α-smooth muscle actin), proliferation (PCNA, cytokeratin-14, TGF-β2), angiogenesis (HIF-1α, CD31), ECM accumulation/ organization (collagen type 3, fibronectin), dermal hydration (AQP3), calcium homeostasis (TRPV3, calmodulin), and bioenergetics activation (CCO, AMPK-α, ATP). Collectively, PBM with dual-NIR wavelength (pulsed/ superpulsed-mode) treatment accelerates full-thickness burn wound healing, which could be used as a non-invasive translational approach in clinical significance in conjunction with existing burn wound care management.

Use of either transcranial or whole-body photobiomodulation treatments improves COVID-19 brain fog

There is increasing recognition of post-COVID-19 sequelae involving chronic fatigue and brain fog, for which photobiomodulation (PBM) therapy has been utilized. This open-label, pilot, human clinical study examined the efficacy of two PBM devices, for example, a helmet (1070 nm) for transcranial (tPBM) and a light bed (660 and 850 nm) for whole body (wbPBM), over a 4-week period, with 12 treatments for two separate groups (n = 7 per group). Subjects were evaluated with a neuropsychological test battery, including the Montreal Cognitive Assessment (MoCA), the digit symbol substitution test (DSST), the trail-making tests A and B, the physical reaction time (PRT), and a quantitative electroencephalography system (WAVi), both pre- and post- the treatment series. Each device for PBM delivery was associated with significant improvements in cognitive tests (p < 0.05 and beyond). Changes in WAVi supported the findings. This study outlines the benefits of utilizing PBM therapy (transcranial or whole-body) to help treat long-COVID brain fog.

Attenuation Aβ1-42-induced neurotoxicity in neuronal cell by 660nm and 810nm LED light irradiation

Oligomeric amyloid-β 1-42 (Aβ1-42) has a close correlation with neurodegenerative disorder especially Alzheimer's disease (AD). It induces oxidative stress and mitochondrial damage in neurons. Therefore, it is used to generate AD-like in vitro model for studying neurotoxicity and neuroprotection against amyloid-β. A low-level light therapy (LLLT) is a non-invasive method that has been used to treat several neurodegenerative disorders. In this study, the red wavelength (660nm) and near infrared wavelength (810nm) at energy densities of 1, 3, and 5 J/cm2 were used to modulate biochemical processes in the neural cells. The exposure of Aβ1-42 resulted in cell death, increased intracellular reactive oxygen species (ROS), and retracted neurite outgrowth. We showed that both of LLLT wavelengths could protect neurons form Aβ1-42-induced neurotoxicity in a biphasic manner. The treatment of LLLT at 3 J/cm2 potentially alleviated cell death and recovered neurite outgrowth. In addition, the treatment of LLLT following Aβ1-42 exposure could attenuate the intracellular ROS generation and Ca2+ influx. Interestingly, both wavelengths could induce minimal level of ROS generation. However, they did not affect cell viability. In addition, LLLT also stimulated Ca2+ influx, but not altered mitochondrial membrane potential. This finding indicated LLLT may protect neurons through the stimulation of secondary signaling messengers such as ROS and Ca2+. The increase of these secondary messengers was in a functional level and did not harmful to the cells. These results suggested the use of LLLT as a tool to modulate the neuronal toxicity following Aβ1-42 accumulation in AD's brain.

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.

Recent Mechanisms of Neurodegeneration and Photobiomodulation in the Context of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease and the world's primary cause of dementia, a condition characterized by significant progressive declines in memory and intellectual capacities. While dementia is the main symptom of Alzheimer's, the disease presents with many other debilitating symptoms, and currently, there is no known treatment exists to stop its irreversible progression or cure the disease. Photobiomodulation has emerged as a very promising treatment for improving brain function, using light in the range from red to the near-infrared spectrum depending on the application, tissue penetration, and density of the target area. The goal of this comprehensive review is to discuss the most recent achievements in and mechanisms of AD pathogenesis with respect to neurodegeneration. It also provides an overview of the mechanisms of photobiomodulation associated with AD pathology and the benefits of transcranial near-infrared light treatment as a potential therapeutic solution. This review also discusses the older reports and hypotheses associated with the development of AD, as well as some other approved AD drugs.

Mitochondrial Dysfunction and Parkinson's Disease: Pathogenesis and Therapeutic Strategies

Parkinson's disease (PD) is a common age-related neurodegenerative disorder whose pathogenesis is not completely understood. Mitochondrial dysfunction and increased oxidative stress have been considered as major causes and central events responsible for the progressive degeneration of dopaminergic (DA) neurons in PD. Therefore, investigating mitochondrial disorders plays a role in understanding the pathogenesis of PD and can be an important therapeutic target for this disease. This study discusses the effect of environmental, genetic and biological factors on mitochondrial dysfunction and also focuses on the mitochondrial molecular mechanisms underlying neurodegeneration, and its possible therapeutic targets in PD, including reactive oxygen species generation, calcium overload, inflammasome activation, apoptosis, mitophagy, mitochondrial biogenesis, and mitochondrial dynamics. Other potential therapeutic strategies such as mitochondrial transfer/transplantation, targeting microRNAs, using stem cells, photobiomodulation, diet, and exercise were also discussed in this review, which may provide valuable insights into clinical aspects. A better understanding of the roles of mitochondria in the pathophysiology of PD may provide a rationale for designing novel therapeutic interventions in our fight against PD.

Laser Thermo-Photobiomodulation of Bone Marrow Mesenchymal Stem Cells

We studied the effect of laser radiation of moderate intensity with a wavelength of 970 nm on the efficiency of colony formation of rat bone marrow mesenchymal stem cells (MSC) in vitro. In this case, photobimodulation and thermal heating of MSC occur simultaneously. This combined laser treatment allows increasing the number of colonies by 6 times in comparison with the control and by more than 3 times in comparison with thermal heating alone. The mechanism of such an increase is associated with combined thermal and light effects of laser radiation of moderate intensity, which stimulates cell proliferation. This phenomenon can be used as the basis for solving the most important task of cell transplantation, associated with the expansion of autologous stem cells and activation of their proliferative potential.

Photobiomodulation in Acute Traumatic Brain Injury: A Systematic Review and Meta-Analysis

Photobiomodulation (PBM) is a therapeutic modality that has gained increasing interest in neuroscience applications, including acute traumatic brain injury (TBI). Its proposed mechanisms for therapeutic effect when delivered to the injured brain include antiapoptotic and anti-inflammatory effects. This systematic review summarizes the available evidence for the value of PBM in improving outcomes in acute TBI and presents a meta-analysis of the pre-clinical evidence for neurological severity score (NSS) and lesion size in animal models of TBI. A systematic review of the literature was performed, with searches and data extraction performed independently in duplicate by two authors. Eighteen published articles were identified for inclusion: seventeen pre-clinical studies of in vivo animal models and one clinical study in human patients. The available human study supports safety and feasibility of PBM in acute moderate TBI. For pre-clinical studies, meta-analysis for NSS and lesion size were found to favor intervention versus control. Subgroup analysis based on PBM parameter variables for these outcomes was performed. Favorable parameters were identified as: wavelengths in the region of 665 nm and 810 nm; time to first administration of PBM ≤4 h; total number of daily treatments ≤3. No differences were identified between pulsed and continuous wave modes or energy delivery. Mechanistic substudies within included in vivo studies are presented and were found to support hypotheses of antiapoptotic, anti-inflammatory, and pro-proliferative effects, and a modulation of cellular metabolism. This systematic review provides substantial meta-analysis evidence of the benefits of PBM on functional and histological outcomes of TBI in in vivo mammalian models. Study design and PBM parameters should be closely considered for future human clinical studies.

Effects of photobiomodulation on mitochondrial function in diabetic adipose-derived stem cells in vitro

Herein are reported the effects of photobiomodulation (PBM) on adenosine triphosphate (ATP) and reactive oxygen species (ROS) quantification and mitochondria membrane potential (MMP) of the mitochondria of diabetic adipose-derived stem cells (ADSCs) in vitro. Additionally, the expression of PTEN-induced kinase 1 (PINK1) and RBR E3 ubiquitin-protein ligase (PARKIN) genes, which are involved in mitochondrial quality, were quantified. First, type one diabetes was induced in 10 rats. The rats were then kept for 1 month, after which fat tissue was excised from subcutaneous regions, and stem cells were selected from the fat, characterized as ADSC, and cultivated and increased in elevated sugar conditions in vitro; these samples were considered diabetic-ADSC. Two groups were formed, namely, diabetic-control-ADSC and PBM-diabetic-ADSC. ATP, ROS quantification, and MMP of mitochondria of diabetic ADSCs in vitro were measured, and the expression of PINK1 and Parkin genes was quantified in vitro. The results revealed that PBM significantly increased ATP quantification (p = 0.05) and MMP activity (p = 0.000) in diabetic-ADSCs in vitro compared to the control diabetic-ADSCs; however, it significantly decreased ROS quantification (p = 0.002) and PINK1(p = 0.003) and PARKIN gene expression (p = 0.046) in diabetic-ADSCs. The current findings indicate for the first time that PBM has the potential to maintain the function and quality of mitochondrial diabetic-ADSCs by significantly increasing ATP quantification and MMP activity in diabetic-ADSCs in vitro while significantly decreasing ROS quantification and PINK1 and PARKIN gene expression, making PBM an attractive candidate for use in improving the efficacy of autologous stem cell remedies for diabetic patients with infected diabetic foot ulcers.

Photobiomodulation therapy at red and near-infrared wavelengths for osteogenic differentiation in the scaffold-free microtissues

One of the novel strategies for bone tissue regeneration is photobiomodulation (PBM) which depends on the red and near-infrared light absorption by mitochondria and may trigger bone tissue regeneration via the production of intracellular ROS and ATP, NO release, etc. It is also important to identify the changes in those signal molecule levels in an in vivo mimicking platform such as 3-Dimensional (3D) Scaffold Free Microtissues (SFMs) that may serve more natural osteogenic differentiation responses to PBM. Herein, we aimed to increase the osteogenic differentiation capability of the co-culture of Human Bone Marrow Stem Cells (hBMSC) and Human Umbilical Vein Endothelial Cells (HUVECs) on 3D SFMs by triple light treatment at 655 and 808-nm of wavelengths with the energy densities of 1, 3, and 5 J/cm². We performed the analysis of cell viability, diameter measurements of SFMs, intracellular ROS production, NO release, ATP activity, temperature measurements, DNA content, ALPase activity, calcium content, and relative gene expressions of ALP, Collagen, and Osteopontin by qRT-PCR. It was found that both wavelengths were effective in terms of the viability of SFMs. 1 and 5 J/cm² energy densities of both wavelengths increased the SFM diameter with significant changes in intracellular ROS, ATP, and NO levels compared to the control group. We concluded that PBM therapy was successful to induce osteogenesis. 1 J/cm² at 655 nm of wavelength and 5 J/cm² at 808 nm of wavelength were the most effective energy densities for osteogenic differentiation on SFMs with triple light treatment.

NIR irradiation of human buccal fat pad adipose stem cells and its effect on TRP ion channels

The effect of near infrared (NIR) laser irradiation on proliferation and osteogenic differentiation of buccal fat pad-derived stem cells and the role of transient receptor potential (TRP) channels was investigated in the current research. After stem cell isolation, a 940 nm laser with 0.1 W, 3 J/cm² was used in pulsed and continuous mode for irradiation in 3 sessions once every 48 h. The cells were cultured in the following groups: non-osteogenic differentiation medium/primary medium (PM) and osteogenic medium (OM) groups with laser-irradiated (L +), without irradiation (L -), laser treated + Capsazepine inhibitor (L + Cap), and laser treated + Skf96365 inhibitor (L + Skf). Alizarin Red staining and RT-PCR were used to assess osteogenic differentiation and evaluate RUNX2, Osterix, and ALP gene expression levels. The pulsed setting showed the best viability results (P < 0.05) and was used for osteogenic differentiation evaluations. The results of Alizarin red staining were not statistically different between the four groups. Osterix and ALP expression increased in the (L +) group. This upregulation abrogated in the presence of Capsazepine, TRPV1 inhibitor (L + Cap); however, no significant effect was observed with Skf96365 (L + Skf).

Anti-hyperalgesic effects of photobiomodulation therapy (904 nm) on streptozotocin-induced diabetic neuropathy imply MAPK pathway and calcium dynamics modulation

Several recent studies have established the efficacy of photobiomodulation therapy (PBMT) in painful clinical conditions. Diabetic neuropathy (DN) can be related to activating mitogen-activated protein kinases (MAPK), such as p38, in the peripheral nerve. MAPK pathway is activated in response to extracellular stimuli, including interleukins TNF-α and IL-1β. We verified the pain relief potential of PBMT in streptozotocin (STZ)-induced diabetic neuropathic rats and its influence on the MAPK pathway regulation and calcium (Ca²⁺) dynamics. We then observed that PBMT applied to the L4-L5 dorsal root ganglion (DRG) region reduced the intensity of hyperalgesia, decreased TNF-α and IL-1β levels, and p38-MAPK mRNA expression in DRG of diabetic neuropathic rats. DN induced the activation of phosphorylated p38 (p-38) MAPK co-localized with TRPV1⁺ neurons; PBMT partially prevented p-38 activation. DN was related to an increase of p38-MAPK expression due to proinflammatory interleukins, and the PBMT (904 nm) treatment counteracted this condition. Also, the sensitization of DRG neurons by the hyperglycemic condition demonstrated during the Ca²⁺ dynamics was reduced by PBMT, contributing to its anti-hyperalgesic effects.

Promoting Immortalized Adipose-Derived Stem Cell Transdifferentiation and Proliferation into Neuronal-Like Cells through Consecutive 525 nm and 825 nm Photobiomodulation

Neuronal cells can be generated from adipose-derived stem cells (ADSCs) through biological or chemical inducers. Research has shown that this process may be optimized by the introduction of laser irradiation in the form of photobiomodulation (PBM) to cells. This in vitro study is aimed at generating neuronal-like cells with inducers, chemical or biological, and at furthermore treating these transdifferentiating cells with consecutive PBM of a 525 nm green (G) laser and 825 nm near-infrared (NIR) laser light with a fluence of 10 J/cm². Cells were exposed to induction type 1 (IT1): 3-isobutyl-1-methylxanthine (IBMX) (0.5 mM)+indomethacin (200 μM)+insulin (5 μg/ml) for 14 days, preinduced with β-mercaptoethanol (BME) (1 mM) for two days, and then incubated with IT2: β-hydroxyanisole (BHA) (100 μM)+retinoic acid (RA) (10-6 M)+epidermal growth factor (EGF) (10 ng/ml)+basic fibroblast growth factor (bFGF) (10 ng/ml) for 14 days and preinduced with β-mercaptoethanol (BME) (1 mM) for two days and then incubated with indomethacin (200 μM)+RA (1 μM)+forskolin (10 μM) for 14 days. The results were evaluated through morphological observations, viability, proliferation, and migration studies, 24 h, 48 h, and 7 days post-PBM. The protein detection of an early neuronal marker, neuron-specific enolase (NSE), and late, ciliary neurotrophic factor (CNTF), was determined with enzyme-linked immunosorbent assays (ELISAs). The genetic expression was also explored through real-time PCR. Results indicated differentiation in all experimental groups; however, cells that were preinduced showed higher proliferation and a higher differentiation rate than the group that was not preinduced. Within the preinduced groups, results indicated that cells treated with IT2 and consecutive PBM upregulated differentiation the most morphologically and physiologically.

Stimulatory effects of wavelength-dependent photobiomodulation on proliferation and angiogenesis of colorectal cancer

In recent decades, the laser treatment of cancer has been introduced as a promising treatment option. Because of the maldistribution of optical energy and an ambiguous boundary between the normal and tumor tissues, laser irradiation can stimulate residual cancer cells, leading to a cancer regrowth. As photobiomodulation (PBM) is involved in an extensive range of cellular responses, profound comprehension of photo-stimulated mechanisms against the cancer cells is required to establish a safety margin for PBM. Therefore, we aimed to identify the stimulant effects of PBM at various wavelengths against the tumor cells to establish a safety margin for the laser treatment. CT26 murine colon cancer cells were exposed to either 405 (BL), 635 (VIS), or 808 (NIR) nm laser lights at the fluences of 0, 10, 30, and 50 J/cm². In addition, CT26 tumor-bearing mice were irradiated with BL, VIS, or NIR at a fluence of 30 J/cm². Both the proliferation and angiogenesis potential of the CT26 cells and tumors were evaluated using the MTT assay, western blot, and immunohistochemistry (IHC) staining analyses. Although cell viability was not statistically significant, BL significantly induced p-ERK upregulation in the CT26 cells, indicating that PBM with BL can stimulate proliferation. In vivo tests showed that the NIR group exhibited the maximum relative tumor volume, and BL yielded a slight increase compared to the control. In the IHC staining and western blot analyses, both BL and NIR increased the expression of EGFR, VEGF, MMP-9, and HIF-1α, which are related to the proliferation and angiogenesis-related factors. Further investigations will be pursued to clarify the molecular pathways that depend on the cancer cell types and laser wavelengths for the establishment of safety guidelines in clinical environments.

Photobiomodulation therapy for osteoarthritis: Mechanisms of action

Photobiomodulation (PBM) is a non-invasive therapeutic modality with demonstrated effects in many fields related to regenerative medicine. In the field of orthopedics, in particular, PBM at various wavelengths has demonstrated the capacity to trigger multiple biological effects associated with protective mechanisms in musculoskeletal tissues. The articles cited in this review show that devices operating close to or within the near infrared range at low intensities can provoke responses which favor the shift in the predominant catabolic microenvironment typically seen in degenerative joint diseases, especially osteoarthritis (OA). These responses include proliferation, differentiation and expression of proteins associated with stable cell cycles. Additionally, PBM can also modulate oxidative stress, inflammation and pain by exerting regulatory effects on immune cells and blocking the transmission of pain through sensory neuron fibers, without adverse events. Collectively, these effects are essential in order to control the progression of OA, which is in part attributed to exacerbated inflammation and degradative enzymatic reactions which gradually contribute to the destruction of joint tissues. PBM may offer medical experts ease of application, financial viability, efficacy and lack of serious adverse events. Therefore, it may prove to be a suitable ally in the management of mild to moderate degrees of OA. This review explores and discusses the principal biological mechanisms of PBM and how the produced effects may contribute to the amelioration of osteoarthritic progression. Literature was reviewed using PubMed and Google Scholar in order to find studies describing the mechanisms of PBM. The investigation included a combination of nomenclature such as: “photobiomodulation”, “phototherapy”, “laser therapy”, “PBM”, “osteoarthritis”, low level light therapy”, “inflammation” and “cartilage”. We considered only articles written in English, with access to the full text.

The 1064-nm Nd: YAG Photobiomodulation vs. 20% Benzocaine Topical Gel in Inducing Mucosal Anesthetic Effect: A Double-Blind Randomized Clinical Trial

The periapical local anesthetic injection may be associated with fear of needles and pain administration. Dental topical anesthetic agents can help to reduce pain perception; however, adverse events can occur. To investigate the efficacy of 1064-nm photobiomodualtion (PBM) in inducing mucosal anesthesia delivered with a flat-top hand-piece compared to 20% Benzocaine topical anesthetic gel, sixty healthy patients were randomly allocated (1:1) to either 20% benzocaine topical gel + placebo laser (T group) or PBM + placebo gel (L group). The 1064-nm Nd:YAG laser was employed and is associated with a novel flat-top hand piece. The applied operational parameters were 0.5 W, 10 Hz, 100 µs pulse width, and 30 J/cm2 for one-minute single application time. The enrolled subjects were asked to assess pain intensity at the time of anesthetic injection with a Visual Analog Scale. Taking into consideration taste, undesirable numbness, and overall satisfaction, the patients were asked to rate their experiences according to a verbal rating scale. Statistical analysis showed no statistically significant difference between the T and L Groups for pain ratings (p = 0.0596). The L Group displayed significantly higher ratings than T Group for taste, undesirable numbness, and overall satisfaction (p < 0.001). The 1064-nm PBM delivered by flat-top hand piece is effective in inducing mucosal anesthesia, eliminating the adverse side-effects of the conventional topical anesthetic gel.

Can Photobiomodulation Support the Management of Temporomandibular Joint Pain? Molecular Mechanisms and a Systematic Review of Human Clinical Trials

This study aims to point out the correlation between photobiomodulation (PBM) targets and effects and management of temporomandibular disorders (TMDs) pain using diode lasers with infrared wavelengths ranging from 780 up to 980 nanometers (nm). A systematic search of multiple electronic databases was done to identify the clinical trials published between 1st January 2010 and 18th December 2021. The included studies were limited to human subjects who had TMD pain, involving two genders with age > 18 years, and were treated with PBM using a diode laser (780–980 nm) as a non-pharmacological therapy to decrease the intensity of the pain associated to TMDs. The risk of bias for included studies was assessed using the Cochrane RoB tool (for randomized studies). The methodologic quality was rated using the Delphi list. The findings suggest that PBM is an effective tool in alleviating TMDs’ pain and increasing the range of movement in patients with Axis 1 of TMDs. However, TMDs’ pain related to underlying pathology cannot be solely treated by PBM. The causative factors must be treated first. Studies displaying the highest quality Delphi score may represent a suggested PBM therapy protocol to follow for TMDs pain management.

Thermodynamic basis for comparative photobiomodulation dosing with multiple wavelengths to direct odontoblast differentiation

Multiple wavelength devices are now available for photobiomodulation (PBM) treatments, but their dosimetry for individual or combinatorial use remains unclear. The present work investigated the effects of 447, 532, 658, 810, 980 and 1064 nm wavelengths on odontoblast differentiation at 10 mW/cm² using either equal treatment time for conventional fluence (300 seconds for 3 J/cm² ) or varying times to adjust for individual wavelength photon fluence (4.6 p.J/cm² ). Both 447 and 810 nm significantly increased alkaline phosphatase (ALP) activity, while 1064 nm showed reduced ALP activity at 3 J/cm² . However, ALP induction was significantly improved when equivalent photon fluence dosing was used. Other wavelengths did not show significant changes compared to untreated controls. The data suggest that accounting for wavelength-specific photon energy transfer during PBM dosing could improve clinical safety and efficacy.

Neuronal differentiation potential of primary and immortalized adipose stem cells by photobiomodulation

Adipose Stem Cells (ASCs) are capable of neuronal differentiation, which makes them an ideal choice for therapies in nerve injuries. Principally, the differentiation of autologous ASCs to neurons offers solutions for the replacement therapies of nervous system with patient's own genetic background. On the contrary, the use of genetically modified (immortalized) ASCs has the benefit of accessibility by surpassing ethical concerns and ease for propagation as a continuous cell culture. Photobiomodulation (PBM) is a therapeutic modality with laser or light, which is widely been used for modulating stem cell bioprocesses viz. proliferation and differentiation. A comparative analysis was performed to evaluate the neuronal differentiation potential of primary ASCs isolated from a healthy human subject with commercially obtained immortalized ASCs with PBM. The outcome of this analysis will help us to know either primary or immortalized ASCs are most suitable for biomedical applications. Both primary and immortalized ASCs were characterized using their surface protein markers CD44/90/133/166 and induced to differentiate into neuronal cells using Fibroblast Growth Factor, basic (bFGF) and forskolin following PBM using Near Infra-Red (NIR) lasers. Based on the expression of nestin, an early neuronal marker an exposure to 5, 10 and 15 J/cm² of NIR and growth inducers for 14 days the primary ASCs demonstrated a higher neuronal differentiation potential compared to the immortalized ASCs. However, newly differentiated cells from either of these ASCs did not reveal βIII-tubulin, an intermediate neuronal marker even by 21 days of differentiation. This study gives an indication that immortalized ASCs have a phenotype and differentiation potential slightly less but comparable to the freshly isolated ASCs. We suggest that PBM along with growth inducers offer a better solution of differentiating ASCs to neurons.

Low-level light pre-conditioning promotes C2C12 myoblast differentiation under hypoxic conditions

Exercise, especially anaerobic one, can gradually increase muscle mass over time as a result of adaptive responses of muscle cells to ensure metabolic homeostasis in the tissue. Low-level light therapy (LLLT) or photobiomodulation exhibits beneficial effects on promoting muscular functions, regeneration, and recovery from exhausting exercise, although the underlying cellular mechanisms remain poorly understood. We found that hypoxia, a condition following anaerobic exercise, significantly impeded myotube differentiation from myoblasts. However, this adverse effect was blunted greatly by pre-exposure of myoblast cells to a 980 nm laser at 0.1 J/cm² , resulting in almost nearly normal myotube differentiation. LLL pre-treatment enhanced myotube formation by 80%, with a tubular diameter of 4.28 ± 0.11 μm on average, representative of a 53.4% increase over sham light treatment. The normalized myoblast differentiation concurred with 68% more mitochondrial mass and myogenin expression over controls. Moreover, LLL pre-treatment appeared to enhance glucose uptake, prevent energy metabolic switch from oxidative phosphorylation to glycolysis, and diminish lactate production under hypoxic conditions. The observation provides valuable guidance with respect to the timing of LLLT and its potential effects on muscle strengths in concert with anaerobic exercise.

Effect of Photobiomodulation Therapy on Differentiation of Mesenchymal Stem Cells Derived from Impacted Third Molar Tooth into Neuron-like Cells

Peripheral nerve damages are among the most important consequences of dental and maxillofacial procedures. Tissue engineering using mesenchymal stem cells (MSCs) is a promising method to manage such injuries. Moreover, photobiomodulation therapy (PBMT) can enhance this treatment. The present study aimed to investigate the effect of PBMT on differentiation of MSCs derived from dental follicle (DF) into neurons. MSCs were isolated from an impacted tooth follicle by digestion method. The stem cells were cultured, and differentiated into neurons. The cells received two sessions of PBMT with 810 or 980nm diode laser (100 mW, 4 J/cm² ) in either DMEM or neural inductive medium . Phenotypic characterization of the cells was determined using Flow cytometry. In addition, β-tubulin and MAP2 genes expression level changes were analyzed using RT-PCR and western blot technique. After 14 days, Flow cytometry analysis confirmed the mesenchymal nature of cells. RT-PCR and western blot affirmed the expression of β-tubulin and MAP2 genes and proteins, respectively. PBMT with both wavelengths significantly increased β-tubulin and MAP2 expression in neural inductive medium with highest expression mean in 980-nm group. PBMT with 810 and 980-nm lasers could be a promising adjunctive method in differentiation of DF-originated MSCs into neural cells.

A Narrative Review on Oral and Periodontal Bacteria Microbiota Photobiomodulation, through Visible and Near-Infrared Light: From the Origins to Modern Therapies

Photobiomodulation (PBM) consists of a photon energy transfer to the cell, employing non-ionizing light sources belonging to the visible and infrared spectrum. PBM acts on some intrinsic properties of molecules, energizing them through specific light wavelengths. During the evolution of life, semiconducting minerals were energized by sun radiation. The molecules that followed became photoacceptors and were expressed into the first proto-cells and prokaryote membranes. Afterward, the components of the mitochondria electron transport chain influenced the eukaryotic cell physiology. Therefore, although many organisms have not utilized light as an energy source, many of the molecules involved in their physiology have retained their primordial photoacceptive properties. Thus, in this review, we discuss how PBM can affect the oral microbiota through photo-energization and the non-thermal effect of light on photoacceptors (i.e., cytochromes, flavins, and iron-proteins). Sometimes, the interaction of photons with pigments of an endogenous nature is followed by thermal or photodynamic-like effects. However, the preliminary data do not allow determining reliable therapies but stress the need for further knowledge on light-bacteria interactions and microbiota management in the health and illness of patients through PBM.

Repeated irradiation by light-emitting diodes may impede the spontaneous progression of experimental periodontitis: a preclinical study

PURPOSE

We investigated whether repeated irradiation with light-emitting diodes (LEDs) at a combination of 470 nm and 525 nm could suppress the progression of experimental periodontitis.

METHODS

A experimental periodontitis model was established in the second, third, and fourth premolars of the mandible in beagle dogs for 2 months. The spontaneous progression of periodontitis was monitored under the specified treatment regimen for 3 months. During this period, the animals were subjected to treatments of either plaque control only (control) or plaque control with LED application (test) at 2-week intervals. The clinical parameters included the probing pocket depth (PPD), gingival recession (GR), and the clinical attachment level (CAL). Histomorphometric analysis was performed using measurements of the length of the junctional epithelium, connective tissue (CT) zone, and total soft tissue (ST).

RESULTS

There were significant differences in PPD between the control and test groups at baseline and 12 weeks. When the change in PPD was stratified based on time intervals, it was shown that greater differences occurred in the test group, with statistical significance for baseline to 12 weeks, 6 to 12 weeks, and baseline to 6 weeks. There was no significant difference in GR between the control and test groups at any time points. Likewise, no statistically significant differences were found in GR at any time intervals. CAL showed a statistically significant difference between the control and test groups at baseline only, although significant differences in CAL were observed between baseline and 12 weeks and between 6 and 12 weeks. The proportion of CT to ST was smaller for both buccal and lingual areas in the control group than in the test group.

CONCLUSIONS

Repeated LED irradiation with a combination of 470-nm and 525-nm wavelengths may help suppress the progression of periodontal disease.

Steering the multipotent mesenchymal cells towards an anti-inflammatory and osteogenic bias via photobiomodulation therapy: How to kill two birds with one stone

The bone marrow-derived multipotent mesenchymal cells (MSCs) have captured scientific interest due to their multi-purpose features and clinical applications. The operational dimension of MSCs is not limited to the bone marrow reservoir, which exerts bone-building and niche anabolic tasks; they also meet the needs of quenching inflammation and restoring inflamed tissues. Thus, the range of MSC activities extends to conditions such as neurodegenerative diseases, immune disorders and various forms of osteopenia. Steering these cells towards becoming an effective therapeutic tool has become mandatory. Many laboratories have employed distinct strategies to improve the plasticity and secretome of MSCs. We aimed to present how photobiomodulation therapy (PBM-t) can manipulate MSCs to render them an extraordinary anti-inflammatory and osteogenic instrument. Moreover, we discuss the outcomes of different PBM-t protocols on MSCs, concluding with some perplexities and complexities of PBM-t in vivo but encouraging and feasible in vitro solutions.

Effects of Photobiomodulation Therapy with Various Laser Wavelengths on Proliferation of Human Periodontal Ligament Mesenchymal Stem Cells

Several methods have been proposed to enhance the regeneration and healing time in periodontal therapy. Photobiomodulation therapy (PBMT) is a recently suggested novel technique for this purpose. This study aimed to compare the efficacy of PBMT with various laser wavelengths and energy densities on proliferation of human periodontal ligament mesenchymal stem cells (PDLMSCs). The wells containing PDLMSCs were subjected to laser irradiation at 635, 660, 808, and 980 nm wavelengths with 1, 1.5, 2.5 and 4 J/cm² energy densities. Cell proliferation and viability were evaluated after 1, 3, and 5 days with the methyl thiazolyl tetrazolium (MTT) assay and 4,6-diamidino-2-phenylindole (DAPI) staining. No significant difference was observed among the experimental and the control groups on day 1 (P>0.05). On day 3, 808 nm laser at 4 J/cm² energy density and 980 nm laser at all densities had significant differences with control group. On day 5, the control group had significant differences in cell proliferation with 808 nm laser at 2.5 and 4 J/cm² energy densities, and 980 nm laser at all densities. PBMT with 635, 660, 808, and 980 nm wavelengths increased the proliferation of PDLMSCs but the maximum cell viability was prominent after irradiation by 980 nm laser with energy density of 4 J/cm² on day 3.

Plasmon-Triggered Upconversion Emissions and Hot Carrier Injection for Combinatorial Photothermal and Photodynamic Cancer Therapy

Despite the unique ability of lanthanide-doped upconversion nanoparticles (UCNPs) to convert near-infrared (NIR) light to high-energy UV-vis radiation, low quantum efficiency has rendered their application unpractical in biomedical fields. Here, we report anatase titania-coated plasmonic gold nanorods decorated with UCNPs (Au NR@aTiO₂@UCNPs) for combinational photothermal and photodynamic therapy to treat cancer. Our novel architecture employs the incorporation of an anatase titanium dioxide (aTiO₂) photosensitizer as a spacer and exploits the localized surface plasmon resonance (LSPR) properties of the Au core. The LSPR-derived near-field enhancement induces a threefold boost of upconversion emissions, which are re-absorbed by neighboring aTiO₂ and Au nanocomponents. Photocatalytic experiments strongly infer that LSPR-induced hot electrons are injected into the conduction band of aTiO₂, generating reactive oxygen species. As phototherapeutic agents, our hybrid nanostructures show remarkable in vitro anticancer effect under NIR light [28.0% cancer cell viability against Au NR@aTiO₂ (77.3%) and UCNP@aTiO₂ (98.8%)] ascribed to the efficient radical formation and LSPR-induced heat generation, with cancer cell death primarily following an apoptotic pathway. In vivo animal studies further confirm the tumor suppression ability of Au NR@aTiO₂@UCNPs through combinatorial photothermal and photodynamic effect. Our hybrid nanomaterials emerge as excellent multifunctional phototherapy agents, providing a valuable addition to light-triggered cancer treatments in deep tissue.

Hair Growth Promoting Effects of 650 nm Red Light Stimulation on Human Hair Follicles and Study of Its Mechanisms via RNA Sequencing Transcriptome Analysis

Background

Androgenetic alopecia (AGA) leads to thinning of scalp hair and affects 60%~70% of the adult population worldwide. Developing more effective treatments and studying its mechanism are of great significance. Previous clinical studies have revealed that hair growth is stimulated by 650-nm red light.

Objective

This study aimed to explore the effect and mechanism of 650-nm red light on the treatment of AGA by using ex vivo hair follicle culture.

Methods

Human hair follicles were obtained from hair transplant patients with AGA. Hair follicles were cultured in Williams E medium and treated with or without 650-nm red light. Real-time RT-PCR and immunofluorescence staining were used to detect the expression level of genes and proteins in hair follicles, respectively. RNA-sequencing analysis was carried out to reveal the distinct gene signatures upon 650 nm treatment.

Results

Low-level 650 nm red light promoted the proliferation of human hair follicles in the experimental cultured-tissue model. Consistently, 650 nm red light significantly delayed the transition of hair cycle from anagen to catagen in vitro. RNA-seq analysis and gene clustering for the differentially expressed genes suggests that leukocyte transendothelial migration, metabolism, adherens junction and other biological process maybe involved in stimulation of hair follicles by 650-nm red light treatment.

Conclusion

The effect of 650-nm red light on ex vivo hair follicles and the transcriptome set which implicates the role of red light in promoting hair growth and reversing of miniaturization process of AGA were identified.

Photobiomodulation at a wavelength of 633 nm leads to faster functional recovery than 804 nm after facial nerve injury

We analyzed the effects of photobiomodulation (PBM) of various wavelengths on regeneration of the facial nerve using in vitro and in vivo experimental models. We assessed the antioxidative effect of PBM in geniculate ganglion neurons irradiated with a diode laser at 633 nm, 780 nm and 804 nm. Wavelengths of 633 and 780 nm but not 804 nm inhibited cell death by oxidative stress. We assessed the effects of PBM on functional and morphologic recovery in rats divided into control, facial nerve damage (FND) and FND irradiated with a 633 nm or 804 nm lasers. Injured rats treated with 633-nm light had better facial palsy scores, larger axon diameter and higher expression of Schwann cells compared with the FND group. No positive results were observed in rats irradiated at 804-nm light. These findings indicate that 633-nm PBM promotes accelerated nerve regeneration and improved functional recovery in an injured facial nerve.

An Effective and Safe Novel Treatment of Opioid Use Disorder: Unilateral Transcranial Photobiomodulation

Background: The opioid epidemic is a global tragedy even with current treatments, and a novel, safe, and effective treatment would be welcomed. We report here our findings from our second randomized controlled trial to evaluate unilateral transcranial photobiomodulation as a treatment for opioid use disorder. Methods: We enrolled 39 participants with active opioid cravings at 2 sites, 19 received the active treatment which consisted of a 4-min twice weekly (every 3 or 4 days) application of a light-emitting diode at 810 nm with an irradiance of 250 mW/cm2 and a fluence of 60 J/cm2 to the forehead over either the left or right dorsolateral prefrontal cortex with a fluence to the brain of 2.1 J/cm2. Twenty participants received a sham treatment with the same device with foil over the bulb. The side of the treatment was based on Dual-Brain Psychology, which posits that one hemisphere is more affected by past maltreatments and is more prone to anxiety and drug cravings that the other hemisphere. We treated the hemisphere with the more positive hemispheric emotional valence (HEV) by 2 tests for HEV. Results: Our primary outcome was changes in pre-treatment opioid craving scale (OCS) minus baseline, and we found using a mixed model that the active group had a highly significant treatment * time benefit over the sham group, p < 0.0001, effect size at the last follow-up of 1.5. The active treatment benefited those not on buprenorphine as well as those not on it. The TimeLine Follow Back measure of opioid use was significantly better in the actively treated group, p = 0.0001, with an effect size of 0.45. We observed no adverse effects. Conclusion: Active unilateral transcranial photobiomodulation to the brain hemisphere with the better HEV was better than sham in the reduction of opioid cravings and opioid use to a very significant degree in a RCT of 39 participants at 2 independent sites. In the active group those on buprenorphine and those not on it both had improvements in cravings over the study. No adverse responses were reported in either group. ClinicalTrials.gov Identifier: NCT04340622.

Hormesis and adult adipose-derived stem cells

This paper provides a detailed assessment of the occurrence of hormetic dose responses in adipose-derived stem cells (ADSCs) of animal models and humans. While a broad range of endpoints has been considered, the predominant research focus in the literature has involved cell proliferation and differentiation. Hormetic dose responses have been commonly reported for ADSCs, encompassing a broad range of chemicals, including pharmaceuticals, dietary supplements and endogenous agents as well as a broad range of physical stressors such as low frequency vibrations, electromagnetic frequency (EMF), heat and sound waves. Numerous agents upregulate key functions such as cell proliferation and differentiation in ADSCs, following the quantitative features of the hormesis dose response model. The paper also assesses the capacity of agents to selectively and dose-dependently activate cell proliferation and/or differentiation, their underlying mechanistic foundations and potential clinical implications. These findings indicate that hormetic dose responses are a prominent feature of ADSC biology and may have a determinant role in their potential clinical applications.

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.