Effect of low-level laser therapy on mesenchymal stem cell proliferation: a systematic review

A comparative evaluation of the effects of 635 nm laser on cell proliferation and osteogenic differentiation of buccal fat pad mesenchymal stem cells

The purpose of this study was to evaluate the effects of 635 nm diode laser with different powers on undifferentiated mesenchymal stem cells obtained from buccal fat pad. Human buccal fat stem cells were cultured in DMEM containing 10% FBS, penicillin, and streptomycin under 5% CO2 and 95% humidity. Cells were cultured in 96-well plate and 24 h later, laser irradiation with 635 nm diode laser was performed in four groups of 200, 300, 400, and 500 mW powers in addition to the control group with the same energy density of 4 J/cm2. MTT and flow cytometry assay was performed to evaluate cell proliferation and viability on 2 and 4 days after irradiation. Alizarin red assay and real-time PCR (OPN, OCN, ALP, and RUNX-2 genes) was performed to evaluate osteogenic differentiation. According to the MTT assay, none of the mentioned powers of 635 nm diode laser had significant effect on cell proliferation. Cells irradiated with power of 400 mW and 500 mW significantly showed a greater number of necrotic cells compared to the control group in Day 4. Cells irradiated with 300 mW power significantly exhibited a greater amount of nodule formation compared to all groups. Results of this study indicated that 635 nm diode laser with energy density of 4 J/cm2 has a positive effect inducing osteogenic differentiation when applying with a power of 300 mW in buccal fat pad mesenchymal stem cells.

Light assisted modulation of stem cell function and secretome production: a systematic review on current status and new avenues for regenerative medicine

Stem cells (SC) based therapies are proving to be the mainstay of regenerative medicine. Despite the significant potential, direct grafting or implantation of SCs for regenerative therapy encounters various translational roadblocks such as paucity of implantable cells, decreased potency, cell death post-implantation, cell damage caused by the pre-existing inflammation and immune rejection. Hence, an emerging avenue is cell-free approach; use of SC secretome. Although priming approaches based on pharmacological molecules/chemicals, cytokines and growth factors are being explored to elicit enhanced secretome production, the potential concerns include the need for continuous replenishment and potential chemical contamination during secretome isolation. To alleviate these concerns, various non-pharmacological approaches for invigorating SCs are also being investigated and among these, use of photobiomodulation (PBM) has garnered considerable interest. Notwithstanding the positive outcomes, standardized parameters are yet to be established for reproducible results. Moreover, the mechanisms of PBM based SC stimulation and secretome production are poorly elucidated and significant knowledge gaps exist on influence of cell type, culture conditions on PBM. This review aims to provide insight into the current status of this emerging field emphasizing on novel avenues and potential challenges for clinical translation. We also summarize the studies on PBM based proliferation, differentiation and secretome production according to SC cell type and culture conditions. Further, as a fixed PBM based protocol for SC proliferation, differentiation and secretome is lacking, the knowledge on functional targets and pathways in PBM based SC stimulation needs upgradation. Consequently, putative mechanisms for PBM based SC secretome have been proposed.

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.

Photobiomodulation of alveolar bone healing in rats with low-level laser and light emitting diode therapy

The present study investigates the potential contribution of Photobiomodulation (PBM) to the regeneration of the bone following the extraction of the first mandibular molar in rats. The study evaluates the efficacy of PBM, using both Low-Level Laser Therapy (LLLT) and Light-Emitting Diode Therapy (LEDT), as promotors of osteoblastic activity and the formation of new bone. Study design, setting, and sample: 45 male Wistar rats were divided randomly into three groups of 15 individuals - (i) control group (left lower molar removed only), (ii) the LLL group (molar removed, followed by LLLT), and (iii) the LED group (molar removed, followed by LEDT). Each of these groups was divided into three subgroups of five rats, which were monitored for 7, 14 or 28 days following the extraction of the tooth. For analysis, the bone of the right mandibular hemiarch was extracted and the specimens were stained with Hematoxylin and Eosin. Microscopic morphological analysis revealed that the LED therapy had promoted greater bone remodeling activity at 7 and 14 days post-extraction, whereas the LLLT promoted the generation of more mature bone tissue, but more slowly overall. The quantitative analysis revealed a significant increase in the area of bone activity and the osteoblast count in both PBM groups in comparison with the control. Photobiomodulation, using either low-level laser or LED therapy, is effective for both bone regeneration and osteoblast activity following dental injury in rats. While the LED therapy initially presented higher levels of remodeling activity, the laser produced more mature bone tissue over time. These findings indicate that PBM is a promising therapeutic alternative for healing bone, with the potential for the improvement of postoperative outcomes in dental practise.

Effect of nutritional stress and photobiomodulation protocol on in vitro viability and proliferation of murine preosteoblast cells

This study aimed to assess the impact of nutritional conditions and irradiation parameters on the viability and proliferation of murine preosteoblasts. MC3T3-E1 cells were maintained under standard culture conditions (αMEM supplemented with 10% fetal bovine serum) or nutritional deficit conditions (αMEM without serum) and irradiated or not (control) with an InGaAlP diode laser at wavelengths of 660 nm (red) or 790 nm (infrared), with doses of 1, 4, or 6 J/cm², in a single dose in continuous mode. Cell viability and proliferation were assessed 24, 48, and 72 h after irradiation using the Alamar blue reduction assay. The cell cycle and events related to cell death were evaluated via propidium iodide (PI) staining and Annexin V/PI assays, respectively, through flow cytometry. The data revealed that in cells cultured with normal nutrition (10% FBS), there was no significant difference (p > 0.05) in cell viability or proliferation among the different irradiation protocols. In contrast, in the experiments conducted under nutritional deficiency, the infrared laser at a dose of 6 J/cm² significantly increased (p < 0.05) cell viability and proliferation compared with those of the control group at 72 h. The data were confirmed by cell cycle and cell death events (Annexin V/PI) assays. These results suggest that in vitro PBM yields more consistent biostimulatory effects on pre-osteoblasts subjected to nutritional deficiency, highlighting the need for attention to simulate these conditions in studies with laser therapy in in vitro bone disease models and in in vitro experiments using PBM for bone tissue engineering.

The proliferation and viability of human periodontal ligament stem cells cultured on polymeric scaffolds can be improved by low-level laser irradiation

This study assessed the impact of low-level laser irradiation on the viability and proliferation of human periodontal ligament stem cells (hPDLSCs) cultivated on polylactic acid (PLA) scaffolds. hPDLSCs were obtained, characterized, and grown on the surface of PLA films produced via the solvent casting technique. The study involved two groups: the control group, which was not exposed to radiation, and the laser group, which was irradiated with a diode laser (InGaAIP) with a power of 30 mW, a wavelength of 660 nm, and a single dose of 1 J/cm² emitted continuously. Cell viability was assessed 24 and 48 hours after irradiation using the Alamar blue and Live/Dead assays. Flow cytometry was used to assess cell cycle events, and scanning electron microscopy (SEM) was used to evaluate the interaction between cells and the biomaterial. The results revealed a statistically significant increase in cell metabolic activity in the laser group compared with the control group at 24 hours (p <0.05) and 48 hours (p <0.001), as indicated by the Alamar blue assay. The Live/Dead assay also revealed a greater density of viable cells in the laser group. The cell cycle analysis revealed a significant increase in the number of cells in the proliferative phase (G2/M) in the laser group compared with the control group (p <0.001). The SEM images demonstrated that the irradiated group had a greater concentration of cells while still maintaining their cell shape and projections. This study demonstrated that photobiomodulation can increase the viability and proliferation of periodontal stem cells cultured on PLA scaffolds, suggesting the potential of this protocol for future studies on periodontal tissue engineering.

Photobiomodulation effects on neuronal transdifferentiation of immortalized adipose-derived mesenchymal stem cells

Adipose-derived mesenchymal stem cells (ADMSCs) possess the ability to transform into various cell types, including neurons. It has been proposed that the optimization of this transformation can be achieved by using photobiomodulation (PBM). The objective of this laboratory-based investigation was to induce the transformation of immortalized ADMSCs (iADMSCs) into neurons with chemical triggers and then evaluate the supportive effects of PBM at two different wavelengths, 525 nm and 825 nm, each administered at a dose of 5 J/cm2, as well as the combined application of these wavelengths. The results revealed that the treated cells retained their stem cell characteristics, although the cells exposed to the green laser exhibited a reduction in the CD44 marker. Furthermore, early, and late neuronal markers were identified using flow cytometry analysis. The biochemical analysis included the assessment of cell morphology, viability, cell proliferation, potential cytotoxicity, and the generation of reactive oxygen species (ROS). The findings of this study indicate that PBM does not harm the differentiation process and may even enhance it, but it necessitates a longer incubation period in the induction medium. These research findings contribute to the validation of stem cell technology for potential applications in in vivo, pre-clinical, and clinical research environments.

Effect of photobiomodulation therapy with 660 and 980 nm diode lasers on differentiation of periodontal ligament mesenchymal stem cells

This study aimed to compare the effects of photobiomodulation therapy (PBMT) with 660 and 980 nm diode lasers on differentiation of periodontal ligament mesenchymal stem cells (PDLMSCs). In this in vitro, experimental study, PDLMSCs were obtained from the Iranian Genetic Bank and cultured in osteogenic medium. They were then subjected to irradiation of 660 and 980 nm diode lasers, and their viability was assessed after one, two, and three irradiation cycles using the methyl thiazolyl tetrazolium (MTT) assay. The cells also underwent DAPI staining, cell apoptosis assay by using the Annexin V/PI, Alizarin Red staining, and real-time polymerase chain reaction (PCR) for assessment of the expression of osteogenic genes. Data were analyzed by two-way ANOVA. The two laser groups had no significant difference in cell apoptosis according to the results of DAPI staining. Both laser groups showed higher cell viability in the MTT assay at 4 and 6 days compared with the control group. Annexin V/PI results showed higher cell viability in both laser groups at 4 days compared with the control group. Rate of early and late apoptosis was lower in both laser groups than the control group at 4 days. Necrosis had a lower frequency in 980 nm laser group than the control group on day 6. Alizarin Red staining showed higher cell differentiation in both laser groups after 3 irradiation cycles than the control group. The highest expression of osteopontin (OPN), osteocalcin (OCN), and Runt-related transcription factor 2 (RUNX2) was noted in 660 nm laser group with 3 irradiation cycles at 14 days, compared with the control group. PBMT with 660 and 980 nm diode lasers decreased apoptosis and significantly increased PDLMSC differentiation after 3 irradiation cycles.

Physical modulation of mesenchymal stem cell exosomes: A new perspective for regenerative medicine

Mesenchymal stem cell-derived exosomes (MSC-Exo) offer promising therapeutic potential for various refractory diseases, presenting a novel therapeutic strategy. However, their clinical application encounters several obstacles, including low natural secretion, uncontrolled biological functions and inherent heterogeneity. On the one hand, physical stimuli can mimic the microenvironment dynamics where MSC-Exo reside. These factors influence not only their secretion but also, significantly, their biological efficacy. Moreover, physical factors can also serve as techniques for engineering exosomes. Therefore, the realm of physical factors assumes a crucial role in modifying MSC-Exo, ultimately facilitating their clinical translation. This review focuses on the research progress in applying physical factors to MSC-Exo, encompassing ultrasound, electrical stimulation, light irradiation, intrinsic physical properties, ionizing radiation, magnetic field, mechanical forces and temperature. We also discuss the current status and potential of physical stimuli-affected MSC-Exo in clinical applications. Furthermore, we address the limitations of recent studies in this field. Based on this, this review provides novel insights to advance the refinement of MSC-Exo as a therapeutic approach in regenerative medicine.

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.

Effect of Low-Level Diode Laser and Red Light-Emitting Diode on Survival and Osteogenic/Odontogenic Differentiation of Human Dental Pulp Stem Cells

Background: This investigation set out to compare the impacts of low-level diode laser (LLDL) and red light-emitting diode (LED) on the survival of human dental pulp stem cells (hDPSCs) and osteogenic/odontogenic differentiation. Methods and materials: In this ex vivo experimental study, the experimental groups underwent the irradiation of LLDL (4 J/cm2 energy density) and red LED in the osteogenic medium. Survival of hDPSCs was assessed after 24 and 48 h (n = 9) using the methyl thiazolyl tetrazolium (MTT) assay. The assessment of osteogenic/odontogenic differentiation was conducted using alizarin red staining (ARS; three repetitions). The investigation of osteogenic and odontogenic gene expression was performed at two time points, specifically 24 and 48 h (n = 12). This analysis was performed utilizing real-time reverse-transcription polymerase chain reaction (RT-PCR). The groups were compared at each time point using SPSS version 24. To analyze the data, the Mann-Whitney U test, analysis of variance, Tukey's test, and t-test were utilized. Results: The MTT assay showed that LLDL significantly decreased the survival of hDPSCs after 48 h, compared with other groups (p < 0.05). The qualitative results of ARS revealed that LLDL and red LED increased the osteogenic differentiation of hDPSCs. LLDL and red LED both upregulated the expression of osteogenic/odontogenic genes, including bone sialoprotein (BSP), alkaline phosphatase (ALP), dentin matrix protein 1 (DMP1), and dentin sialophosphoprotein (DSPP), in hDPSCs. The LLDL group exhibited a higher level of gene upregulation (p < 0.0001). Conclusions: The cell survival of hDPSCs was reduced, despite an increase in osteogenic/odontogenic activity. Clinical relevance: Introduction of noninvasive methods in regenerative endodontic treatments.

Osteogenic potential of apical papilla stem cells mediated by platelet-rich fibrin and low-level laser

To evaluate the osteogenic potential of platelet-rich fibrin (PRF) and low-level laser therapy (LLLT) on human stem cells from the apical papilla (SCAP) we isolated, characterized, and then cultured in an osteogenic medium cells with PRF and/or LLLT (660 nm, 6 J/m2-irradiation). Osteogenic differentiation was assessed by bone nodule formation and expression of bone morphogenetic proteins (BMP-2 and BMP-4), whereas the molecular mechanisms were achieved by qRT-PCR and RNA-seq analysis. Statistical analysis was performed by ANOVA and Tukey's post hoc tests (p < 0.05* and p < 0.01**). Although PRF and LLLT increased bone nodule formation after 7 days and peaked at 21 days, the combination of PRF + LLLT led to the uppermost nodule formation. This was supported by increased levels of BMP-2 and -4 osteogenic proteins (p < 0.005). Furthermore, the PRF + LLLT relative expression of specific genes involved in osteogenesis, such as osteocalcin, was 2.4- (p = 0.03) and 28.3- (p = 0.001) fold higher compared to the PRF and LLLT groups, and osteopontin was 22.9- and 1.23-fold higher, respectively (p < 0.05), after 7 days of interaction. The transcriptomic profile revealed that the combination of PRF + LLLT induces MSX1, TGFB1, and SMAD1 expression, after 21 days of osteogenic differentiation conditions exposition. More studies are required to understand the complete cellular and molecular mechanisms of PRF plus LLLT on stem cells. Overall, we demonstrated for the first time that the combination of PRF and LLLT would be an excellent therapeutic tool that can be employed for dental, oral, and craniofacial repair and other tissue engineering applications.

Influence of Different Photobiomodulation Parameters on Multi-Potent Adipose Tissue Mesenchymal Cells In Vitro

Objective: Investigating the effect of different parameters of photobiomodulation (PBM) with low-power laser on multi-potent mesenchymal stem cells (MSCs) derived from adipose tissue in terms of proliferation and cell death. Methods: MSCs were submitted to PBM applications with combinations of the following physical parameters: control group (no intervention), wavelengths of 660 and 830 nm; energy of 0.5, 2, and 4 J; and power of 40 and 100 mW. MSC analysis was performed using MetaXpress® software at 24, 48, and 72 h. Results: Irradiation promoted a significant increase in cell proliferation (p < 0.05), with 830 nm laser, 100 mW, with energy of 0.5, 2, and 4 J in relation to the control group at all times. PBM with 660 nm, power of 40 mW, and energy of 0.5, 2, and 4 J produced greater cell death at 24 h compared with the control group. At the time of 72 h, there was no significant difference concerning cell death. Conclusions: According to the results found, we can conclude that both wavelengths were effective; however, the 830 nm laser was more effective in terms of cell proliferation compared with the 660 nm laser. The 660 nm wavelength showed a significant increase in cell death when compared with the 830 nm laser.

Effect of photobiomodulation therapy on the morphology, intracellular calcium concentration, free radical generation, apoptosis and necrosis of human mesenchymal stem cells-an in vitro study

The aim of the study was to investigate the impact of multiwave locked system (MLS M1) emitting synchronized laser radiation at 2 wavelength simultaneous (λ = 808 nm, λ = 905 nm) on the mesenchymal stem cells (MSCs). Human MSCs were exposed to MLS M1 system laser radiation with the power density 195-318 mW/cm2 and doses of energy 3-20 J, in continuous wave emission (CW) or pulsed emission (PE). After irradiation exposure in doses of energy 3 J, 10 J (CW, ƒ = 1000 Hz), and 20 J (ƒ = 2000 Hz), increased proliferation of MSCs was observed. Significant reduction of Fluo-4 Direct™ Ca2+ indicator fluorescence over controls after CW and PE with 3 J, 10 J, and 20 J was noticed. A decrease in fluorescence intensity after the application of radiation with a frequency of 2000 Hz in doses of 3 J, 10 J, and 20 J was observed. In contrary, an increase in DCF fluorescence intensity after irradiation with laser radiation of 3 J, 10 J, and 20 J (CW, ƒ = 1000 Hz and ƒ = 2000 Hz) was also shown. Laser irradiation at a dose of 20 J, emitted at 1000 Hz and 2000 Hz, and 3 J emitted at a frequency of 2000 Hz caused a statistically significant loss of MSC viability. The applied photobiomodulation therapy induced a strong pro-apoptotic effect dependent on the laser irradiation exposure time, while the application of a sufficiently high-energy dose and frequency with a sufficiently long exposure time significantly increased intracellular calcium ion concentration and free radical production by MSCs.

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.

Nd:YAG-photobiomodulation enhanced ADSCs multilineage differentiation and immunomodulation potentials

To investigate the effects of Nd: YAG (1064 nm) photobiomodulation on multilineage differentiation and immunomodulation potentials of adipose tissue-derived stem cells (ADSCs) in vitro and in vivo. For in vitro experiments, cells were divided into the control group (non-irradiated control ADSCs) and photobiomodulation groups. 0.5 J/cm2, 1 J/cm2, 2 J/cm2, and 4 J/cm2 were used for proliferation assays; for ADSCs adipogenic differentiation assays, 0.5 J/cm2, 1 J/cm2 were applied; 1 J/cm2 was used for migration and immunomodulation assays. The differentiation abilities were assessed by qPCR, Oil Red O staining, and Alizarin Red staining. The immunomodulation potential was assessed by qPCR and human cytokine array. DSS-induced colitis model. was used to test the effect of photobiomodulation on ADSCs immunomodulation potentials in vivo. Nd:YAG-based photobiomodulation dose-dependently promoted ADSCs proliferation and migration; 1 J/cm2 showed the best promotion effect on proliferation. Moreover, Nd:YAG photobiomodulation promoted ADSCs osteogenic differentiation and brown adipose adipogenic differentiation. The potential immunomodulation assays showed Nd:YAG photobiomodulation improved Anti-inflammation capacity of ADSCs and photobiomodulation irradiated ADSCs effectively alleviated DSS-induced colitis severity in vivo. Our study suggests Nd:YAG photobiomodulation might enhance the ADSCs multilineage differentiation and immunomodulation potentials. These results might help to enhance ADSCs therapeutic effects for clinical application. However, further studies are needed to explore the mechanisms of Nd:YAG photobiomodulation promoting multilineage differentiation and immunomodulation potentials of ADSCs.

Regenerative Medicine and Rehabilitation Therapy in the Canine

Regenerative medicine is used in the canine to optimize tissue healing and treat osteoarthritis and soft tissue injuries. Rehabilitation therapy is also often implemented in the treatment and management of musculoskeletal conditions in the canine. Initial experimental studies have shown that regenerative medicine and rehabilitation therapy may work safely and synergistically to enhance tissue healing. Although additional study is required to define optional rehabilitation therapy protocols after regenerative medicine therapy in the canine, certain fundamental principles of rehabilitation therapy still apply to patients treated with regenerative medicine.

Efficacy of autologous mesenchymal stromal cell treatment for chronic degenerative musculoskeletal conditions in dogs: A retrospective study

Introduction

The objective of this study was to retrospectively analyze clinical data from a referral regenerative medicine practice, to investigate the efficacy of autologous mesenchymal stromal cells (MSC) in 245 dogs deemed unresponsive to conventional treatment by their referring vet.

Methods

Diagnostic imaging [radiology and musculoskeletal ultrasound (MSK-US)] identified musculoskeletal pathology holistically. MSCs, produced according to current guidelines, were initially administered with PRP by targeted injection to joints and/or tendons, with a second MSC monotherapy administered 12 weeks later to dogs with severe pathology and/or previous elbow arthroscopic interventions. Dogs with lumbosacral disease received epidural MSCs with additional intravenous MSCs administered to dogs with spondylosis of the cervical, thoracic and lumbar spine. All dogs received laser therapy at 10 J/cm2 at the time of treatment and for 5 sessions thereafter. Objective outcome measures (stance analysis, range of joint motion, pressure algometry) and validated subjective outcome measures (owner reported VetMetrica HRQL™ and veterinary pain and quality of life impact scores) were used to investigate short and long-term (6-104 weeks) efficacy. Outcome data were collected at predetermined time windows (0-6, 7-12, 13-18, 19-24, 25-48, 49-78, 79-104) weeks after initial treatment.

Results

There were statistically significant improvements in post compared with pre-treatment measures at all time windows in stance analysis, shoulder and hip range of motion, lumbosacral pressure algometry, and to 49-78 weeks in carpus and elbow range of motion. Improvements in 4 domains of quality of life as measured by VetMetricaTM were statistically significant, as were scores in vet-assessed pain and quality of life impact. In dogs receiving one initial treatment the mean time before a second treatment was required to maintain improvements in objective measures was 451 days. Diagnostic imaging confirmed the regenerative effects of MSCs in tendinopathies by demonstrating resolution of abnormal mineralization and restoration of normal fiber patterns.

Discussion

This represents the first study using "real-world" data to show that cell-based therapies, injected into multiple areas of musculoskeletal pathology in a targeted holistic approach, resulted in rapid and profound positive effects on the patient's pain state and quality of life which was maintained with repeat treatment for up to 2 years.

Effect of diode low level laser and red light emitting diode irradiation on cell proliferation and osteogenic/odontogenic differentiation of stem cells from the apical papilla

BACKGROUND

This experimental study aimed to assess the effect of irradiation of red light-emitting diode (LED) and Diode low-level laser (LLL) on osteogenic/odontogenic differentiation of stem cells from the apical papilla (SCAPs).

MATERIALS AND METHODS

SCAPs were isolated from the human tooth root. The experimental groups were subjected to 4 J/cm² diode low level laser and red LED irradiation in osteogenic medium. The control group did not receive any irradiation. Cell viability/proliferation of SCAPs was assessed by the methyl thiazolyl tetrazolium (MTT) assay on days 1 and 2 (n = 9). Osteogenic differentiation was evaluated by alizarin red staining (ARS) (n = 3), and expression of osteogenic genes by real-time polymerase chain reaction (RT-PCR) (n = 12) on days 1 and 2. SPSS version 18 was used for data evaluation. The Kruskal-Wallis and Mann-Whitney tests were used to compare the groups at each time point.

RESULTS

The MTT assay showed no significant difference in cell viability/proliferation of SCAPs in the low level laser, red LED, and control groups at 24 or 48 h (P < 0.001). The ARS assessment showed that low level laser and red LED irradiation enhanced osteogenic differentiation of SCAPs. low level laser and red LED irradiation both induced over-expression of osteogenic/dentinogenic genes including alkaline phosphatase (ALP), dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP-1), and bone sialoprotein (BSP) in SCAPs. Up-regulation of genes was significantly greater in low level laser irradiation group than red LED group (P < 0.001).

CONCLUSION

Diode low level laser irradiation with 4 J/cm² energy density and red LED irradiation enhanced osteogenic differentiation of SCAPs without adversely affecting cell viability.

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.

Low-Level Laser Therapy in the Treatment of Autoimmune Thyroiditis

Introduction: Autoimmune thyroiditis (AIT) is an autoimmune disorder that is characterized by thyroid gland dysfunction. Low-level laser therapy (LLLT), as a safe and non-invasive intervention, has gained much attention in many clinical applications including pain relief, regenerative medicine, and autoimmune. Methods: In this review, we discuss the effect of LLLT on cellular responses and its application in the treatment of AIT. Such keywords as "low-level laser therapy", "photobiomodulation" and "autoimmune thyroiditis" were used to find studies related to laser therapy in AIT in Google Scholar, PubMed and Medline databases. Results: LLLT reduced thyroid gland inflammation and inhibited immune cell trafficking. LLLT modulated inflammatory responses and improved thyroid gland regeneration. Conclusion: Investigations indicated that besides current treatment strategies, LLLT could be a promising therapeutic approach for the treatment of AIT.

A comparison of human dental pulp stem cell activity cultured on sandblasted titanium discs decontaminated with Er:YAG laser and air-powder abrasion: an in vitro study

Decontamination of implant surfaces is important to the treatment of peri-implantitis. Er:YAG laser and air-powder abrasion system are regarded as the most effective means of decontamination of implant surfaces. The aim of this in vitro study was to compare the activity of human dental pulp stem cells (hDPSCs) cultured on decontaminated sandblasted titanium discs using Er:YAG laser irradiation and air-powder abrasion. Forty-five titanium discs were contaminated with Escherichia coli (E. coli) bacteria and fifteen titanium discs served as sterile control groups. Thirty contaminated titanium discs were decontaminated with Er:YAG laser or air-powder abrasion system and fifteen contaminated discs were used as contaminated control group. Afterwards, hDPSCs were seeded on all sixty experimental titanium discs. The effects of two decontamination tools on hDPSCs viability were evaluated by MTT assay. Alkaline phosphatase (ALP) activity assay, quantitative real-time PCR analysis and alizarin red staining method were performed to assess hDPSCs osteogenic differentiation. Scanning microscope electron (SEM) was also used to evaluate the effects of two different decontaminated methods on cellular morphology. Our study showed that decontamination using Er:YAG laser caused maximum cell viability. However, the ALP activity was not different in laser and air-abrasion groups. The significant expression of an osteoblastic marker and stronger Alizarin red staining were observed in laser irradiation groups. In addition, SEM observation indicated that grown cells were more stretched and more filopodia in Er:YAG-treated discs. In the present study, Er:YAG laser and air-powder abrasion improved the activity of the cells cultured on the decontaminated titanium discs. However, in comparison with air-powder abrasion, Er:YAG laser was more effective.

Effects of Two Protocols of Low-Level Laser Therapy on the Proliferation and Differentiation of Human Dental Pulp Stem Cells on Sandblasted Titanium Discs: An In Vitro Study

Introduction: Stem cell activities have different effects on tissue response and its outcomes. Low-level laser therapy (LLLT) can be considered a trigger to modify stem cell activities. The objective of the present experimental investigation was to study the effects of two protocols of LLLT on the proliferation and differentiation of human dental pulp stem cells (hDPSCs) cultured on sandblasted titanium discs. Methods: Cells obtained from human dental pulp were seeded/cultured on titanium discs and were set in 2 main groups: (i) Radiated cells using the gallium-aluminium-arsenide (GaAlAs) diode laser at a continuous wavelength of 808 nm at 3 J/cm² for 12 sec or 5 J/cm² for 20 seconds, and (ii) Non-irradiated cells serving as control groups. The impact of LLLTs on hDPSC-proliferation and viability was investigated using the MTT assay after 24, 72 and 96 hours. The alkaline phosphatase activity was studied with p-nitrophenylphosphate after 14 and 28 days. The ability of hDPSCs to express osteocalcin was investigated using real-time polymerase chain reaction after 28 days, while their attachment was observed under a scanning electron microscope (SEM) after 14 and 28 days. Results: Our study showed that LLLTs caused maximum cell proliferation in 96 hours (P<0.001) with 3 J/cm² resulting in a higher proliferation rate. The highest activity of alkaline phosphatase and osteocalcin expression was observed in the laser radiation groups after 28 days. Conclusion: The outcomes of the current study showed that cultured hDPSCs on sandblasted titanium discs had a tendency towards increased cellular activity in response to LLLTs. Thus, LLLTs could regulate the activities of hDPSCs on bone repair surrounding the sandblasted titanium discs.

Enhancing therapeutic efficacy of human adipose-derived stem cells by modulating photoreceptor expression for advanced wound healing

Background

Human adipose-derived stem cells (hADSCs) have been widely used for regenerative medicine because of their therapeutic efficacy and differentiation capacity. However, there are still limitations to use them intactly due to some difficulties such as poor cell engraftment and viability after cell transplantation. Therefore, techniques such as photobiomodulation (PBM) are required to overcome these limitations. This study probed improved preclinical efficacy of irradiated hADSCs and its underlying molecular mechanism.

Methods

hADSCs were irradiated with green organic light-emitting diodes (OLEDs). Treated cells were analyzed for mechanism identification and tissue regeneration ability verification. Expression levels of genes and proteins associated with photoreceptor, cell proliferation, migration, adhesion, and wound healing were evaluated by performing multiple assays and immunostaining. Excision wound models were employed to test in vivo therapeutic effects.

Results

In vitro assessments showed that Opsin3 (OPN3) and OPN4 are both expressed in hADSCs. However, only OPN4 was stimulated by green OLED irradiation. Cell proliferation, migration, adhesion, and growth factor expression in treated hADSCs were enhanced compared to control group. Conditioned medium containing paracrine factors secreted from irradiated hADSCs increased proliferation of human dermal fibroblasts and normal human epidermal keratinocytes. Irradiated hADSCs exerted better wound healing efficacy in vivo than hADSCs without OLED irradiation.

Conclusions

Our study introduces an intracellular mechanism of PBM in hADSCs. Our results revealed that photoreceptor OPN4 known to activate G_q-protein and consequently lead to reactive oxygen species production responded to OLED irradiation with a wavelength peak of 532 nm. In conclusion, green OLED irradiation can promote wound healing capability of hADSCs, suggesting that green OLED has potential preclinical applications.

Single and consecutive application of near-infrared and green irradiation modulates adipose derived stem cell proliferation and affect differentiation factors

Regenerative medicine uses undifferentiated adipose-derived mesenchymal stem cells (ADMSCs) to differentiate into multiple cell types. Photobiomodulation (PBM) is a rapidly growing treatment for pain and inflammation reduction, as well as tissue healing. PBM's efficacy is dependent on wavelength and energy dosage. Red (600-700 nm) and near-infrared (780-1100 nm) wavelengths have been shown to promote cell proliferation. Light wavelengths such as green (495 nm-570 nm) have been found to influence ADMSC differentiation. The initiation of ADMSC proliferation and differentiation requires physiologically relevant levels of reactive oxygen species (ROS), while increased levels inhibit self-renewal. Stem cell differentiation is guided by mitochondrial metabolism, where an increased mitochondrial membrane potential (MMP) is associated with higher in vitro differentiation capacity. ADMSCs must home to and accumulate at the sites of injury in regenerative medicine, so cell homing is critical. The aim of this in vitro study was to compare consecutive NIR (825 nm) and green (525 nm) applications on ADMSC morphology and physiology with the possibility that multiple wavelengths could lead to a combination of the two effects. The results showed that concurrent use of NIR-green irradiation significantly stimulated ADMSC proliferation, increasing population density and cellular ATP. Furthermore, NIR-green showed a time dependent increase in ROS production and was significantly higher at 7 days. Consecutive NIR-green irradiation significantly increased MMP and was most effective at facilitating ADMSC migration over time. Findings suggest that with consecutive NIR and green irradiation, the ADMSCs can rapidly proliferate, but can also be modulated for regenerative purposes.

Laser Photobiomodulation 808 nm: Effects on Gene Expression in Inflammatory and Osteogenic Biomarkers in Human Dental Pulp Stem Cells

The tissue engineering of dental oral tissue is tackling significant advances and the use of stem cells promises to boost the therapeutical approaches of regenerative dentistry. Despite advances in this field, the literature is still scarce regarding the modulatory effect of laser photobiomodulation (PBM) on genes related to inflammation and osteogenesis in Postnatal Human Dental Pulp Stem cells (DPSCs). This study pointedly investigated the effect of PBM treatment in proliferation, growth and differentiation factors, mineralization, and extracellular matrix remodeling genes in DPSCs. Freshly extracted human third molars were used as a source for DPSCs isolation. The isolated DPSCs were stimulated to an inflammatory state, using a lipopolysaccharide (LPS) model, and then subjected or not to laser PBM. Each experiment was statistically evaluated according to the sample distribution. A total of 85 genes related to inflammation and osteogenesis were evaluated regarding their expression by RT-PCR. Laser PBM therapy has shown to modulate several genes expression in DPSCs. PBM suppressed the expression of inflammatory gene TNF and RANKL and downregulated the gene expression for VDR and proteolytic enzymes cathepsin K, MMP-8 and MMP-9. Modulation of gene expression for proteinase-activated receptors (PARs) following PBM varied among different PARs. As expected, PBM blocked the odontoblastic differentiation of DPSCs when subjected to LPS model. Conversely, PBM has preserved the odontogenic potential of DPSCs by increasing the expression of TWIST-1/RUNEX-2/ALP signaling axis. PBM therapy notably played a role in the DPSCs genes expression that mediate inflammation process and tissue mineralization. The present data opens a new perspective for PBM therapy in mineralized dental tissue physiology.

Low-Level Laser Irradiation Promotes Proliferation and Differentiation on Apical Papilla Stem Cells

Introduction: Low-level laser therapy (LLLT) has been reported to improve cell proliferation and differentiation. The stem cells derived from dental apical papilla (SCAPs) are a promising therapy because they are easily obtained from immature human teeth. The effect of LLLT over SCAPs is still unknown. This study aimed to evaluate the proliferation and osteogenic potential of the SCAPs stimulated with LLLT. Methods: SCAPs were isolated from the third molars of a healthy donor and characterized according to the minimum established criteria. SCAPs were cultured for 24 hours before being exposed to LLLT. Cells were exposed to different doses, energy, and wavelengths for selecting the irradiation parameters. SCAPs proliferation was evaluated with the MTT assay at 24 hours and 7-day post-laser exposure. VEGF and TGFβ2 expression were assessed with a specific enzyme-linked immunosorbent assay (ELISA). The osteogenic differentiation potential was analyzed with alizarin red staining, and the nodule quantification was performed by the relative optical density (ROD) analysis using ImageJ software. Results: The cells isolated from the apical papilla showed phenotype and stem cell properties. SCAPs irradiated with one dose at 6 J/m2 and 650 nm exhibited significantly higher proliferation (P>0.05) than the controls nonirradiated. LLLT stimulated SCAPs' expression of factors VEGF and TGFβ2. Also, SCAPs irradiated showed higher osteogenic activity (P<0.05). Conclusion: LLLT promotes proliferation, osteogenic differentiation, and VEGF and TGFβ2 expression on SCAPs. LLLT is a practical approach for the preconditioning of SCAPs in vitro for future regenerative therapies. More studies are needed to determine the underlying molecular processes that determine the mechanism of the LLLT.

Increased Anti-Allergic Effects of Secretome of Low-Level Light Treated Tonsil-Derived Mesenchymal Stem Cells in Allergic Rhinitis Mouse Model

BACKGROUND

Low-level light therapy (LLLT) is widely used for the photobiomodulation of cell behavior. Recent studies have shown that LLLT affects the proliferation and migration of various types of mesenchymal stem cells (MSCs). However, there is a lack of studies investigating the effect of LLT on enhancing the immunomodulatory properties of tonsil-derived MSCs (T-MSCs).

OBJECTIVE

The aim of this study was to investigate the immunomodulatory effects of conditioned media from T-MSCs (T-MSCs-CM) treated with LLLT in allergic inflammation.

METHODS

We isolated T-MSCs from human palatine tonsils and evaluated the ingredients of T-MSCs-CM. The effect of T-MSCs-CM treated with LLLT was evaluated in a mouse model of allergic rhinitis (AR). We randomly divided the mice into four groups (negative control, positive control, T-MSCs-CM alone, and T-MSCs-CM treated with LLLT). To elucidate the therapeutic effect, we assessed rhinitis symptoms, serum immunoglobulin (Ig), the number of inflammatory cells, and cytokine expression.

RESULTS

We identified increased expression of immunomodulatory factors, such as HGF, TGF-β, and PGE, in T-MSCs-CM treated with LLLT, compared to T-MSCs-CM without LLLT. Our animal study demonstrated reduced allergic symptoms and lower expression of total IgE and OVA-specific IgE in the LLLT-treated T-MSCs-CM group compared to the AR group and T-MSCs-CM alone. Moreover, we found that T-MSCs-CM treated with LLLT showed significantly decreased infiltration of eosinophils, neutrophils, and IL-17 cells in the nasal mucosa and reduced IL-4, IL-17, and IFN-γ expression in OVA-incubated splenocytes compared to the AR group.

CONCLUSIONS

The present study suggests that T-MSCs-CM treated with LLLT may provide an improved therapeutic effect against nasal allergic inflammation than T-MSCs-CM alone.

Dosage Effects of an 810 nm Diode Laser on the Proliferation and Growth Factor Expression of Human Gingival Fibroblasts

Introduction: A substantial amount of evidence supports the positive effect of photobiomodulation on the proliferation and differentiation of various cell types. Several laser wavelengths have been used for wound healing improvement, and their actual outcome depends on the settings utilized during irradiation. However, the heterogeneous wavelengths and laser settings applied in the existing literature make it difficult to draw solid conclusions and comparison of different studies. The aim of the present study is to evaluate and compare the effects of various doses of laser energy, provided by an 810 nm diode, on human gingival fibroblasts in terms of proliferation and expression of growth factors with a pivotal role in wound healing. Methods: Human gingival fibroblasts were cultured on plastic tissue culture and irradiated with 2, 4, 6 or 12 J/cm². The effects of the low-level laser therapy (LLLT) using an 810 nm diode laser on growth factor expression (EGF, TGF and VEGF) were evaluated by qPCR at 72 hours and 7 days after irradiation. Cell proliferation was evaluated at 24, 48 and 72 hours after LLLT using MTT assay. Results: Energy density of 12 J/cm² provoked irradiated gingival fibroblasts to demonstrate significantly higher proliferation as well as higher gene expression of Col1, VEGF and EGF. LLLT positive effects were obvious up to 7 days post-irradiation. Conclusion: LLLT with 810 nm presents beneficial effects on proliferation, collagen production and growth factor expression in human gingival fibroblast cells. The application of 12 J/cm² can be suggested as the optimal energy density for the enhancement of the wound healing process.

Optical and thermal fields induced in the bone marrow by external laser irradiation

In regenerative medicine, the problem of growing mesenchymal stem cells from the bone marrow often arises. In such cases is important that the number of initial cells was large enough and their proliferative activity was high. We believe that this problem can be solved by short-term heating of local areas of the bone marrow in vivo with laser radiation. In this regard, it is of interest to study the optical and temperature fields induced inside the tubular bone under external laser irradiation. In this work, we obtained experimental data on the spatial distribution of temperature in the bone marrow of the rat femur in vitro under external exposure to laser radiation with wavelengths of 970 and 1940 nm. Radiation delivery was carried out using an optical fiber which tip contacted the surface of the femur bone. A thin thermocouple was used to measure the temperature in a local area of the bone marrow. By moving the optical fiber tip discretely along the longitudinal axis of the bone, and the thermocouple in the perpendicular direction, the spatial temperature distributions in dynamics were measured. Similarly, the spatial distributions of the laser radiation intensity were measured by replacing thermocouple with optical fiber probe. A thermal camera was used to control the temperature of the bone surface near the tip of the fiber. It was shown that the marrow could be heated from the outside by about 5-10 °C during 10 s without significant overheating of the bone tissue. The data obtained make it possible to estimate the volume of the bone marrow heated by the laser to a predetermined temperature and to make a reasonable choice of laser exposure modes to stimulate the proliferative activity of bone marrow mesenchymal stem cells in vivo.

Effects of photobiomodulation on the redox state of healthy and cancer cells

Photobiomodulation therapy (PBMT) uses light to stimulate cells. The molecular basis of the effects of PBMT is being unveiled, but it is stated that the cytochrome-c oxidase enzyme in mitochondria, a photon acceptor of PBMT, contributes to an increase in ATP production and modulates the reduction and oxidation of electron carriers NADH and FAD. Since its effects are not fully understood, PBMT is not used on tumors. Thus, it is interesting to investigate if its effects correlate to mitochondrial metabolism and if so, how it could be linked to the optical redox ratio (ORR), defined as the ratio of FAD/(NADH + FAD) fluorescences. To that end, fibroblasts (HDFn cell line) and oral squamous cell carcinoma (SCC-25 cell line) were irradiated with a light source of 780 nm and a total dose of 5 J/cm2, and imaged by optical microscopy. PBMT down-regulated the SCC-25 ORR by 10%. Furthermore, PBMT led to an increase in ROS and ATP production in carcinoma cells after 4 h, while fibroblasts only had a modest ATP increase 6 h after irradiation. Cell lines did not show distinct cell cycle profiles, as both had an increase in G2/M cells. This study indicates that PBMT decreases the redox state of oral cancer by possibly increasing glycolysis and affects normal and tumor cells through distinct pathways. To our knowledge, this is the first study that investigated the effects of PBMT on mitochondrial metabolism from the initiation of the cascade to DNA replication. This is an essential step in the investigation of the mechanism of action of PBMT in an effort to avoid misinterpretations of a variety of combined protocols.

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.

Photobiomodulation Effect of Different Diode Wavelengths on the Proliferation of Human Gingival Fibroblast Cells

This study is focused on comparing the effect of various energy densities and wavelengths of diode lasers on the proliferation of human gingival fibroblast (HGF) cells in vitro. In this study, 204 sample cells were examined in 4 test groups (laser radiation) and 1 control group (non-laser radiation). The proliferation rate of radiated cells with wavelengths of 635, 660, 808 and 980 nm and the densities of 1, 1.5, 2.5 and 4 J cm^-2 was measured after 1, 3 and 5 days using the MTT assay. The proliferation rate of human gingival fibroblast (HGF) cells in test groups was increased on day 1 at wavelengths of 635, 808 and 980 nm and on day 3 at the wavelength of 980 nm compared with the control group. Our findings denoted that the photobiomodulation therapy increased the proliferation rate of HGF. The most desirable laser radiation setting, which led to the highest proliferation rate of the cells, included 980 nm wavelength with 1, 1.5 and 4 J cm^-2 energy densities and 635 nm wavelength with 4 J cm^-2 energy density.

Biological Responses of Stem Cells to Photobiomodulation Therapy

BACKGROUND

Stem cells have attracted the researchers interest, due to their applications in regenerative medicine. Their self-renewal capacity for multipotent differentiation, and immunomodulatory properties make them unique to significantly contribute to tissue repair and regeneration applications. Recently, stem cells have shown increased proliferation when irradiated with low-level laser therapy or Photobiomodulation Therapy (PBMT), which induces the activation of intracellular and extracellular chromophores and the initiation of cellular signaling. The purpose of this study was to evaluate this phenomenon in the literature.

METHODS

The literature investigated the articles written in English in four electronic databases of PubMed, Scopus, Google Scholar and Cochrane up to April 2019. Stem cell was searched by combining the search keyword of "low-level laser therapy" OR "low power laser therapy" OR "low-intensity laser therapy" OR "photobiomodulation therapy" OR "photo biostimulation therapy" OR "LED". In total, 46 articles were eligible for evaluation.

RESULTS

Studies demonstrated that red to near-infrared light is absorbed by the mitochondrial respiratory chain. Mitochondria are significant sources of reactive oxygen species (ROS). Mitochondria play an important role in metabolism, energy generation, and are also involved in mediating the effects induced by PBMT. PBMT may result in the increased production of (ROS), nitric oxide (NO), adenosine triphosphate (ATP), and cyclic adenosine monophosphate (cAMP). These changes, in turn, initiate cell proliferation and induce the signal cascade effect.

CONCLUSION

The findings of this review suggest that PBMT-based regenerative medicine could be a useful tool for future advances in tissue engineering and cell therapy.

Photobiomodulation of mineralisation in mesenchymal stem cells

Mesenchymal stem cells (MSCs) and photobiomodulation (PBM) both offer significant therapeutic potential in regenerative medicine. MSCs have the ability to self-renew and differentiate; giving rise to multiple cellular and tissue lineages that are utilised in repair and regeneration of damaged tissues. PBM utilises light energy delivered at a range of wavelengths to promote wound healing. The positive effects of light on MSC proliferation are well documented; and recently, several studies have determined the outcomes of PBM on mineralised tissue differentiation in MSC populations. As PBM effects are biphasic, it is important to understand the underlying cellular regulatory mechanisms, as well as, provide accurate details of the irradiation conditions, to optimise and standardise outcomes. This review article focuses on the use of red, near-infra-red (R/NIR) and blue wavelengths to promote the mineralisation potential of MSCs; and also reports on the possible molecular mechanisms which underpin transduction of these effects. A variety of potential photon absorbers have been identified which are reported to mediate the signalling mechanisms, including respiratory chain enzymes, flavins, and cryptochromes. Studies report that R/NIR and blue light stimulate MSC differentiation by enhancing respiratory chain activity and increasing reactive oxygen species levels; however, currently, there are considerable variations between irradiation parameters reported. We conclude that due to its non-invasive properties, PBM may, following optimisation, provide an efficient therapeutic approach to clinically support MSC-mediated hard tissue repair. However, to optimise application, further studies are required to identify appropriate light delivery parameters, as well as elucidate the photo-signalling mechanisms involved.

The effect of LED photobiomodulation on the proliferation and osteoblastic differentiation of periodontal ligament stem cells: in vitro

BACKGROUND

The aim of this study was to investigate the influence of three different light-emitting diode (LED) wavelengths on the proliferation and osteoblastic differentiation of periodontal ligament stem cells (PDLSCs) in vitro.

METHODS

PDLSCs seeded on 96- and 24-well plates, for proliferation and osteoblastic differentiation, respectively, were irradiated daily by LED light with peak emission wavelengths of 630, 680, and 830 nm at constant energy densities of 3.5 J/cm². Cultures were grown for 8 days for the proliferation assay, 10 days for the alkaline phosphatase (ALP) assay, and 28 days for Alizarin red staining. Mitochondrial activity, ALP enzyme level, and the ability to form calcium phosphate deposits were measured and compared across cultures.

RESULTS

Results obtained from statistical analysis of the experimental data indicated that the rate of proliferation (P < 0.05) in 830-nm irradiated cultures were significantly higher than the control samples at day 6 and 8; whereas, for the 630- and 680-nm groups, test results showed lower proliferation rates at day 8. For osteoblastic differentiation, significantly greater mineralization than the control samples was detected in the red-light groups (630 and 680 nm) during the late differentiation period (P < 0.001), which was supported by a higher ALP activity of the 630- and 680-nm groups in the early stage (P < 0.01).

CONCLUSION

The results of this study demonstrate that the PDLSCs responded differently to specific LED wavelengths. For enhancing cellular proliferation, 830-nm LED irradiation was more effective. On the other hand, the wavelengths of 630 and 680 nm were better for stimulating osteoblastic differentiation.

Efficacy of Photobiomodulation and Metformin on Diabetic Cell Line of Human Periodontal Ligament Stem Cells through Keap1/Nrf2/Ho-1 Pathway

BACKGROUND

Diabetes mellitus (DM) is a metabolic disorder resulting from hyperglycemia. Hyperglycemia contributes to oxidative stress, and the release of advanced glycation end products (AGEs) further promotes disease pathogenesis. Uncontrolled diabetes reflects great oral complications and affects human oral health. So, the present study aimed to assess the effects of photobiomodulation therapy (PBMT) and Metformin on proliferation and viability of human periodontal ligament stem cells (HPDLSCs) cultured in high glucose medium.

METHODS

HPDLSCs were collected, isolated, and characterized and then divided into eight groups. Addition of extra glucose to diabetic groups 24 hours before cell irradiations. Metformin was added to half of the diabetic groups. Cells were irradiated with 808 nm diode laser 24, 48 hours. Cell viability was analyzed with MTT assay 24 hours post-irradiation to detect cell viability in each group. Real-time (PCR) was used to evaluate gene expression of Nrf2, Keap1, PIK3, and HO-1 and the effect of PBMT on Keap1/Nrf2/Ho-1 Pathway. ELISA reader was used to evaluating cell viability through (ROS, TNF-α, IL-10) protein levels after cell irradiation.

RESULTS

Photobiomodulation at 1, 2, and 3 J/cm2 combined with metformin significantly promoted diabetic cell lines of HPDLSCs viability (in MTT assay and ELISA reader of ROS, TNF-α, IL-10 results) and gene expression of Nrf2, Keap1, PIK3, and HO-1 levels (p< 0.05).

CONCLUSION

photobiomodulation with 3 J/cm2 combined with metformin enhanced proliferation and viability of diabetic cell lines of HPDLSCs and thus could improve differentiation and function of diabetic cell lines of HPDLSCs with minimum side effects.

Could the photobiomodulation therapy induce angiogenic growth factors expression from dental pulp cells?

This study aimed to evaluate the effect of different photobiomodulation (PBM) radiant exposures on the viability, proliferation, and gene expression of pulp fibroblasts from human primary teeth (HPF) involved in the pulp tissue repair. HPF were irradiated with Laser InGaAlP (Twin Flex Evolution, MMOptics®) at 660-nm wavelength (red); single time, continuous mode, 0.04-cm² laser tip area, and 0.225-cm laser tip diameter, keeping the distance of 1 mm between the laser beam and the cell culture. The doses used were between 1.2 and 6.2 J/cm² and were evaluated at the 6 h, 12 h, and 24 h after PBM. MTT and crystal violet assays evaluated the cell viability and proliferation. RT-PCR verified VEGF and FGF-2 mRNA expression. A blinded examiner analyzed the data through two-way ANOVA followed by Tukey test (p < 0.05). The groups with higher powers (10 mW, 15 mW, 20 mW, and 25 mW), shortest application periods (10 s), and radiant exposures between 2.5 and 6.2 J/cm² exhibited statistically higher viability than that of the groups with small power (5 mW), longer application period (50 s), and radiant exposure of 6.2 J/cm² (p < 0.05). VEGF and FGF-2 mRNA expression were observed at the three evaluated periods (6 h, 12 h, and 24 h) and the highest expression was in the shortest period (p < 0.05). All radiant exposures maintained HPF viable. The period of 6 h after irradiation showed statistically greater gene expression for both growth factors than other periods. VEGF mRNA had no differences among the dosimetries studied. The best radiant exposures for FGF-2 gene expression were 2.5 J/cm² and 3.7 J/cm².

Photobiomodulation therapy increases collagen II after tendon experimental injury

A tendon is a mechanosensitive tissue that transmits muscle-derived forces to bones. Photobiomodulation (PBM), also known as low-level laser therapy (LLLT), has been used in therapeutic approaches in tendon lesions, but uncertainties regarding its mechanisms of action have prevented its widespread use. We investigated the response of PBM therapy in experimental lesions of the Achilles tendon in rats. Thirty adult male Wistar rats weighing 250 to 300 g were surgically submitted to bilateral partial transverse section of the Achilles tendon. The right tendon was treated with PBM, whereas the left tendon served as a control. On the third postoperative day, the rats were divided into three experimental groups consisting of ten rats each, which were treated with PBM (Konf, Aculas - HB 750), 780 nm and 80 mW for 20 seconds, three times/week for 7, 14 and 28 days. The rats were sacrificed at the end of the therapeutic time period. The Sca-1 was examined by immunohistochemistry and histomorphometry, and COLA1, COLA2 and COLA3 gene expression was examined by qRT-PCR. COLA2 gene expression was higher in PBM treated tendons than in the control group. The histomorphometric analysis coincided with increased number of mesenchymal cells, characterized by Sca-1 expression in the lesion region (p<0.001). PBM effectively interferes in tendon tissue repair after injury by stimulating mesenchymal cell proliferation and the synthesis of collagen type II, which is suggested to provide structural support to the interstitial tissues during the healing process of the Achilles tendon. Further studies are needed to confirm the role of PBM in tendon healing.

Near-infrared 940-nm diode laser photobiomodulation of inflamed periodontal ligament stem cells

Photobiomodulation (PBM) is an acceptable method of stimulating stem cells through its non-invasive absorption by the cell photoreceptors and the induction of cellular response. The current research was aimed at evaluating the effect of near-infrared PBM on proliferation and osteogenic differentiation in inflamed periodontal ligament stem cells (I-PDLSCs). I-PDLSCs were isolated and characterized. Third passage cells were irradiated with 940-nm laser at an output power of 100 mW in a continuous wave. A fluence of 4 J/cm² in three sessions at 48-h intervals was applied and compared with non-irradiated controls. Cell viability and proliferation were evaluated by MTT assay. Alkaline phosphatase activity, quantitative Alizarin red staining test, and q-RT-PCR were used to evaluate the osteogenic properties of the I-PDLSCs in four groups of (a) osteogenic differentiation medium + laser (ODM + L), (b) osteogenic differentiation medium without laser (ODM), (c) non-osteogenic differentiation medium + laser (L), and (d) non-osteogenic differentiation medium (control). There was a non-significant increase in the viability of cells at 48- and 72-h post last laser irradiation. Alizarin red staining revealed no significant stimulatory effect of PBM at 14 and 21 days. However, alkaline phosphatase activity was significantly higher in the L + ODM group. Expression of osteogenic-related genes had a statistically significant increase at 21-day post irradiation. The irradiation used in the present study showed no significant increase in the proliferation of I-PDLSCs by PBM. However, expression levels of osteogenic-related genes and alkaline phosphatase activity were significantly increased in irradiated groups.

Bone substitutes and photobiomodulation in bone regeneration: A systematic review in animal experimental studies

In general, bone fractures are able of healing by itself. However, in critical situations such as large bone defects, poor blood supply or even infections, the biological capacity of repair can be impaired, resulting in a delay of the consolidation process or even in non-union fractures. Thus, technologies able of improving the process of bone regeneration are of high demand. In this context, ceramic biomaterials-based bone substitutes and photobiomodulation (PBM) have been emerging as promising alternatives. Thus, the present study performed a systematic review targeting to analyze studies in the literature which investigated the effects of the association of ceramic based bone substitutes and PBM in the process of bone healing using animal models of bone defects. The search was conducted from March and April of 2019 in PubMed, Web of Science and Scopus databases. After the eligibility analyses, 16 studies were included in this review. The results showed that the most common material used was hydroxyapatite (HA) followed by Biosilicate associated with infrared PBM. Furthermore, 75% of the studies demonstrated positive effects to stimulate bone regeneration from association of ceramic biomaterials and PBM. All studies used low-level laser therapy (LLLT) device and the most studies used LLLT infrared. The evidence synthesis was moderate for all experimental studies for the variable histological analysis demonstrating the efficacy of techniques on the process of bone repair stimulation. In conclusion, this review demonstrates that the association of ceramic biomaterials and PBM presented positive effects for bone repair in experimental models of bone defects.

The effects of laser stimulation at acupoint ST36 on anxiety-like behaviors and anterior cingulate cortex c-Fos expression in a rat post-traumatic stress disorder model

Post-traumatic stress disorder (PTSD) is a mental disorder that is linked with the onset of multiple anxiety-like behaviors. This study was designed to assess how these behaviors and anterior cingulate cortex (ACC) c-Fos expression were impacted by 10.6-μm laser stimulation at acupoint ST36 a rat model of PTSD. A rat model of PTSD was prepared via prolonged exposure of animals to a stressor, followed by a 7-day period during which animals were allowed to rest undisturbed in their cages. Rats were randomized into four experimental groups (n = 12/group): the control, PTSD, LS, and sham LS groups. Control group animals were not subjected to SPS procedures prior to behavioral testing. LS and sham LS animals were administered LS treatment at bilateral ST36 acupoints or non-acupoints, respectively, for a 7-day period. Animals were then assessed for performance in elevated plus maze (EPM) tests and open-field tests (OFT), and their plasma corticosterone levels were measured. In addition, c-Fos-positive nuclei in the ACC were detected via immunohistochemical staining. Relative to sham LS treatment and PTSD model control rats, LS was associated with increased time spent in both open EPM test arms and in the central area in the OFT (P < 0.05). The PTSD model group exhibited a significant reduction in ACC c-Fox expression, while LS treatment significantly increased this expression (P < 0.001). In addition, a correlation was detected between anxiety-like behaviors and altered ACC neuronal activation. The results of this study indicate that LS at acupoint ST36 can have a previously unreported effect on anxiety-like behaviors in the context of PTSD, with ACC neuronal activation potentially being implicated as a driver of this effect.

Enhancement of Wound Healing by Conditioned Medium of Adipose-Derived Stromal Cell with Photobiomodulation in Skin Wound

Background and Objectives

The objective of this study was to investigate whether conditioned medium from photobiomodulation (PBM) irradiated adipose-derived stromal cell (ASC) spheroids prior to implanting could stimulate angiogenesis and tissue regeneration to improve functional recovery of skin tissue in an animal skin wound model.

Methods and Results

ASC were split and seeded on chitosan-coated 24 well plate at a density of 7.5×10⁴ cells/cm², and allowed to adhere at 37℃. Within 3 days of culture, ASC formed spheroids by PBM irradiation. Conditioned medium (CM) fractions were collected from the PBM-ASC to yield nor adipose-derived stromal cell spheroid (spheroid) and PBM-spheroid, respectively, centrifuged at 13,000 g at 4℃ for 10 min, and stored prior to use for ELISA, protein assay, or in vivo wound-healing assays. Phosphate-buffered saline, cultured CM from ASCs, PBM irradiation prior to implanting conditioned medium from ASC, cultured CM from ASC spheroid, and PBM–spheroid-CM (PSC) were transplanted into a wound bed in athymic mice to evaluate therapeutic effects of PSC in vivo. PSC enhanced wound closure in a skin injury model compared to PBS, CM, PBM–CM, and spheroid-CM. The density of vascular formations increased as a result of angiogenic factors released by the wound bed and enhanced tissue regeneration at the lesion site.

Conclusions

These results indicate that implant of PSC can significantly improve functional recovery compared to PBS, CM, PBM–CM, or spheroid-CM treatment. Implant of PSC may be an effective form of paracrine mediated therapy for treating a wound bed.

Enhancing the Therapeutic Potential of Mesenchymal Stem Cells with Light-Emitting Diode: Implications and Molecular Mechanisms

This study evaluated the effects of light-emitting diode (LED) on mesenchymal stem cells (MSCs). An electronic search was conducted in PubMed/MEDLINE, Scopus, and Web of Science database for articles published from 1980 to February 2020. Ten articles met the search criteria and were included in this review. The risk of bias was evaluated to report quality, safety, and environmental standards. MSCs were derived from adipose tissue, bone marrow, dental pulp, gingiva, and umbilical cord. Protocols for cellular irradiation used red and blue light spectrum with variations of the parameters. The LED has been shown to induce greater cellular viability, proliferation, differentiation, and secretion of growth factors. The set of information available leads to proposing a complex signaling cascade for the action of photobiomodulation, including angiogenic factors, singlet oxygen, mitogen-activated protein kinase/extracellular signal-regulated protein kinase, Janus kinase/signal transducer, and reactive oxygen species. In conclusion, although our results suggest that LED can boost MSCs, a nonuniformity in the experimental protocol, bias, and the limited number of studies reduces the power of systematic review. Further research is essential to find the optimal LED irradiation parameters to boost MSCs function and evaluate its impact in the clinical setting.

The red-light emitting diode irradiation increases proliferation of human bone marrow mesenchymal stem cells preserving their immunophenotype

PURPOSE

For effective clinical application of human bone marrow mesenchymal stem cells (hBM-MSCs), the enhancement of their proliferation in vitro together with maintaining the expression of their crucial surface antigens and differentiation potential is necessary. The present study aimed to investigate the effect of light-emitting diode (LED) irradiation on hBM-MSCs proliferation after two, five, or nine days post-irradiation.

MATERIALS AND METHODS

The hBM-MSCs were exposed to the LED light at 630 nm, 4 J/cm2, and power densities of 7, 17, or 30 mW/cm2. To assess the cell proliferation rate in the sham-irradiated and irradiated samples the cells metabolic activity and DNA content were determined. The number of apoptotic and necrotic cells in the samples was also evaluated. The expression of the crucial surface antigens of the hBM-MSCs up to nine days after irradiation at 4 J/cm2 and 17 mW/cm2 was monitored with flow cytometry. Additionally, the potential of hBM-MSCs for induced differentiation was measured.

RESULTS

When the metabolic activity was assayed, the significant increase in the cell proliferation rate by 31 and 50% after the irradiation with 4 J/cm2 and 17 mW/cm2, respectively, was observed at day five and nine when compared to the sham-irradiated cells (p < .05). Similarly, DNA content within the irradiated hBM-MSCs increased by 31 and 41% at day five and nine after the irradiation with 4 J/cm2 and 17 mW/cm2 in comparison to the sham-irradiated cells. LED irradiation did not change the expression of the crucial surface antigens of the hBM-MSCs up to nine days after irradiation at 4 J/cm2 and 17 mW/cm2. At the same experimental conditions, the hBM-MSCs maintain in vitro their capability for multipotential differentiation into osteoblasts, adipocytes, and chondrocytes.

CONCLUSION

Therefore, LED irradiation at a wavelength of 630 nm, energy density 4 J/cm2, and power density 17 mW/cm2 can effectively increase the number of viable hBM-MSCs in vitro.