The Effects of Photobiomodulation of 808 nm Diode Laser Therapy at Higher Fluence on the in Vitro Osteogenic Differentiation of Bone Marrow Stromal Cells

Photobiomodulation therapy at 650 nm enhances osteogenic differentiation of osteoporotic bone marrow mesenchymal stem cells through modulating autophagy

BACKGROUND

Photobiomodulatiom therapy (PBMT) has biostimulatory effects on bone marrow mesenchymal stem cells (BMSCs), which takes a pivotal role in maintaining bone mass and avoiding osteoporosis (OP). Autophagy is an important regulator for cell survival and homeostasis. Previous researchers found that BMSCs derived from osteoporotic rats (OP-BMSCs) were with the feature of reduced osteogenic differentiation and autophagy dysfunction. However, the potential regulation of PBMT in osteogenic differentiation of OP-BMSCs and its underling relationship with autophagy remain unclear.

METHODS

650 nm red light-emitting diode (LED) was selected to initiate PBMT effects. The isolation and culture of OP-BMSCs were implemented after the establishment of the OP rat model. Firstly, the optimal dose of LED was screened on OP-BMSCs by CCK-8. Meanwhile, the osteogenic and mineralization activities were studied through the detection of Alkaline phosphatase (ALP) and alizarin red S (ARS). Then, the levels of osteogenesis and autophagy were investigated via western blot and immunofluorescence staining. Finally, the autophagy inhibitor 3-MA was applied to illustrate the underlying mechanism of the osteogenic effect of PBMT on OP-BMSCs.

RESULTS

Firstly, the optimal dose of 6 J/cm2 LED was selected in the subsequent experiments according to CCK-8. Then, the ALP activity and the mineralization ability of OP-BMSCs were obviously increased by PBMT. Meanwhile, Runx-2, OCN and OPN were significantly upregulated in LED group. Furthermore, the expressions of autophagic proteins increased significantly in LED group by immunofluorescence staining and western blot assay. At last, the promoted effects of PBMT on osteogenic differentiation in OP-BMSCs were distinctly reversed via inhibiting autophagy.

CONCLUSION

Our research illustrated that 650 nm LED could improve osteogenic differentiation of OP-BMSCs, suggesting a potential correlation between PBMT-mediated activation of autophagy and promotion of osteogenic differentiation.

Effect of 980 nm photobiomodulation delivered by a handpiece with Gaussian vs. Flat-Top profiles on proliferation and differentiation of buccal fat pad stem cells

The aim of this study was to compare the effectiveness of the Gaussian and Flat-Top profiles in proliferation and differentiation of mesenchymal stem cell of buccal fat pad. Based on the timing schedule and type of laser handpieces, the cells were assigned to a control group with no radiation, and two irradiation test groups (980 nm) with Flat-Top (F) (power of 1.1 W, beam area of 1 cm2) and standard Gaussian (G) (power of 0.7 W, beam area of 0.5 cm2) handpieces. Each test group was divided into three subgroups, receiving one time (60 J/cm2), two times (120 J/cm2), and three times (180 J/cm2) irradiation. 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and Annexin V tests were performed. The Alizarin Red staining and polymerase chain reaction tests were done both at the beginning and the end of the first and second weeks. The degree of mineralization and expression of osteogenic markers, RUNX2, OCN, and OPN were evaluated. Based on the MTT and Annexin V test results, both test groups outperformed the control group in degrees of cell proliferation during the first day of laser irradiation (p < 0.05). After one and two times irradiation, the expression of osteogenic markers in the test groups was significantly higher than the control group. PBM with Flat-Top and Gaussian handpieces can enhance ossification and cell differentiation regardless of the type of handpieces.

Effect of 660-nm LED photobiomodulation on the proliferation and chondrogenesis of meniscus-derived stem cells (MeSCs)

Meniscus-derived stem cells (MeSCs), a unique type of MSC, have outstanding advantages in meniscal cytotherapy and tissue engineering, but the effects and molecular mechanisms of PBM on MeSCs are still unclear. We used 660-nm LED light with different energy densities to irradiate six human MeSC samples and tested their proliferation rate via cell counting, chondrogenic differentiation capacity via the DMMB assay, mitochondrial activity via the MTT assay, and gene expression via qPCR. The proliferation ability, chondrogenic capacity and mitochondrial activity of the 18 J/cm2 group were greater than those of the 4 J/cm2 and control groups. The mRNA expression levels of Akt, PI3K, TGF-β3, Ki67 and Notch-1 in the 18 J/cm2 group were greater than those in the other groups in most samples. After chondrogenic induction, the expression of Col2A1, Sox9 and Aggrecan in the 18 J/cm2 group was significantly greater than that in the 4 J/cm2 and control groups in most of the samples. The variation in the MTT values and Src, PI3K, Akt, mTOR and GSK3β levels decreased with time. The results showed that 660-nm LED red light promoted proliferation and chondrogenic differentiation and affected the gene expression of MeSCs, and the effects on gene expression and mitochondrial activity decreased with time.

Pulsed Photothermal Therapy of Solid Tumors as a Precondition for Immunotherapy

Photothermal therapy (PTT) refers to the use of plasmonic nanoparticles to convert electromagnetic radiation in the near infrared region to heat and kill tumor cells. Continuous wave lasers have been used clinically to induce PTT, but the treatment is associated with heat-induced tissue damage that limits usability. Here, the engineering and validation of a novel long-pulsed laser device able to induce selective and localized mild hyperthermia in tumors while reducing the heat affected zone and unwanted damage to surrounding tissue are reported. Long-pulsed PTT induces acute necrotic cell death in heat affected areas and the release of tumor associated antigens. This antigen release triggers maturation and stimulation of CD80/CD86 in dendritic cells in vivo that primes a cytotoxic T cell response. Accordingly, long-pulsed PTT enhances the therapeutic effects of immune checkpoint inhibition and increases survival of mice with bladder cancer. Combined, the data promote long-pulsed PTT as a safe and effective strategy for enhancing therapeutic responses to immune checkpoint inhibitors while minimizing unwanted tissue damage.

Photobiomodulation effects on fibroblasts and keratinocytes after ionizing radiation and bacterial stimulus

OBJECTIVE

Photobiomodulation therapy (PBMT) has proven to reduce inflammation and pain and increase wound healing. Thus, the aim of this study was to analyze the effects of PBMT parameters on migration, proliferation, and gene expression after ionizing radiation and bacterial-induced stress in an in vitro study.

DESIGN

Keratinocytes (HaCaT) and Fibroblasts (HGFs) were grown in DMEM with 10 % fetal bovine serum until stressful condition induction with lipopolysaccharide (LPS) of Escherichia coli (1 µg/mL), Porphyromonas gingivalis protein extract (5 µg/mL) and ionizing radiation (8 Gy). Low-laser irradiation (660 nm, 30 mW) was carried out in four sessions, with 6 h intervals, and energy density of 2, 3, 4, and 5 J/cm². Scratch assays, immunofluorescence, and RT-qPCR were performed.

RESULTS

Treated fibroblasts and keratinocytes showed significant response in proliferation and migration after scratch assays (p < 0.05). Higher expressions of α-SMA in fibroblasts and F-actin in keratinocytes were observed in cells subjected to 3 J/cm². PI3K-pathway genes expression tended to enhance in fibroblasts, presenting a higher relative expression when compared to keratinocytes. In keratinocytes, PBMT groups demonstrated deregulated expression for all inflammatory cytokines' genes tested while fibroblasts presented a tendency to enhance those genes expression in a dose dependent way.

CONCLUSIONS

The present study showed that delivering 660 nm, 30 mW was effective to stimulate cell migration, proliferation and to accelerate wound healing. PBMT can modulate cytokines and pathways involved in wound repair. The different energy densities delivering distinct responses in vitro highlights that understanding laser parameters is fundamental to improve treatment strategies.

The effect of photobiomodulation therapy in common maxillofacial injuries: Current status

The use of photobiomodulation therapy (PBMT) may be used for treating trauma to the maxillofacial region. The effects of PBMT on maxillofacial injuries were discussed in this review article. The electronic databases Pubmed, Scopus, and Web of Science were thoroughly searched. This review included in vitro, in vivo, and clinical studies describing how PBMT can be used in maxillofacial tissue engineering and regenerative medicine. Some studies suggest that PBMT may offer a promising therapy for traumatic maxillofacial injuries because it can stimulate the differentiation and proliferation of various cells, including dental pulp cells and mesenchymal stem cells, enhancing bone regeneration and osseointegration. PBMT reduces pain and swelling after oral surgery and tooth extraction in human and animal models of maxillofacial injuries. Patients with temporomandibular disorders also benefit from PBMT in terms of reduced inflammation and symptoms. PBMT still has some limitations, such as the need for standardizing parameters. PBMT must also be evaluated further in randomized controlled trials in various maxillofacial injuries. As a result, PBMT offers a safe and noninvasive treatment option for patients suffering from traumatic maxillofacial injuries. PBMT still requires further research to establish its efficacy in clinical practice and determine the optimal parameters.

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.

Enhancing osteogenic differentiation in adipose-derived mesenchymal stem cells with Near Infra-Red and Green Photobiomodulation

Worldwide, osteoporosis is the utmost predominant degenerative bone condition. Stem cell regenerative therapy using adipose-derived mesenchymal stem cells (ADMSCs) is a promising therapeutic route for osteoporosis. Photobiomodulation (PBM) has sparked considerable international appeal due to its' ability to augment stem cell proliferation and differentiation properties. Furthermore, the differentiation of ADMSCs into osteoblast cells and cellular proliferation effects have been established using a combination of osteogenic differentiation inducers and PBM. This in vitro study applied dexamethasone, β-glycerophosphate disodium, and ascorbic acid as differentiation inducers for osteogenic induction differentiation media. In addition, PBM at a near-infrared (NIR) wavelength of 825 nm, a green (G) wavelength of 525 nm, and the novel combination of both these wavelengths using a single fluence of 5 J/cm2 had been applied to stimulate proliferation and differentiation effectivity of immortalised ADMSCs into early osteoblasts. Flow cytometry and ELISA were used to identify osteoblast antigens using early and late osteoblast protein markers. Alizarin red Stain was employed to identify calcium-rich deposits by cells within culture. The morphology of the cells was examined, and biochemical assays such as an EdU proliferation assay, MTT proliferation and viability assay, Mitochondrial Membrane Potential assay, and Reactive Oxygen Species assay were performed. The Central Scratch Test determined the cells' motility potential. The investigative outcomes revealed that a combination of PBM treatment and osteogenic differentiation inducers stimulated promising early osteogenic differentiation of immortalised ADMSCs. The NIR-Green PBM combination did appear to offer great potential for immortalised ADMSC differentiation into early osteoblasts amongst selected assays, however, further investigations will be required to establish the effectivity of this novel wavelength combination. This research contributes to the body of knowledge and assists in the establishment of a standard for osteogenic differentiation in vitro utilising PBM.

Multipotent Mesenchymal Cells Homing and Differentiation on Poly(ε-caprolactone) Blended with 20% Tricalcium Phosphate and Polylactic Acid Incorporating 10% Hydroxyapatite 3D-Printed Scaffolds via a Commercial Fused Deposition Modeling 3D Device

As highlighted by the 'Global Burden of Disease Study 2019' conducted by the World Health Organization, ensuring fair access to medical care through affordable and targeted treatments remains crucial for an ethical global healthcare system. Given the escalating demand for advanced and urgently needed solutions in regenerative bone procedures, the critical role of biopolymers emerges as a paramount necessity, offering a groundbreaking avenue to address pressing medical needs and revolutionize the landscape of bone regeneration therapies. Polymers emerge as excellent solutions due to their versatility, making them reliable materials for 3D printing. The development and widespread adoption of this technology would impact production costs and enhance access to related healthcare services. For instance, in dentistry, the use of commercial polymers blended with β-tricalcium phosphate (TCP) is driven by the need to print a standardized product with osteoconductive features. However, modernization is required to bridge the gap between biomaterial innovation and the ability to print them through commercial printing devices. Here we showed, for the first time, the metabolic behavior and the lineage commitment of bone marrow-derived multipotent mesenchymal cells (MSCs) on the 3D-printed substrates poly(e-caprolactone) combined with 20% tricalcium phosphate (PCL + 20% β-TCP) and L-polylactic acid (PLLA) combined with 10% hydroxyapatite (PLLA + 10% HA). Although there are limitations in printing additive-enriched polymers with a predictable and short half-life, the tested 3D-printed biomaterials were highly efficient in supporting osteoinductivity. Indeed, considering different temporal sequences, both 3D-printed biomaterials resulted as optimal scaffolds for MSCs' commitment toward mature bone cells. Of interest, PLLA + 10% HA substrates hold the confirmation as the finest material for osteoinduction of MSCs.

Investigation of the optimal light parameters for photobiomodulation to induce osteogenic differentiation of the human bone marrow stem cell and human umbilical vein endothelial cell co-culture

Bones have an important role in the human body with their complex nature. Mesenchymal stem cells and endothelial cells together support their unique and complex nature. Photobiomodulation (PBM) is a promising method that provides cell proliferation, osteogenic differentiation, and bone regeneration. However, there are still unknowns in the mechanism of osteogenic differentiation induced by PBM. The main aim of the study is to understand the molecular mechanism of PBM at 655 and 808 nm of wavelengths and identify the most effective energy densities of both wavelengths for osteogenic differentiation. The effect of PBM on osteogenic differentiation of Human Bone Marrow Stem Cell (hBMSC) and Human Umbilical Vein Endothelial Cell (HUVEC) co-culture was examined at 1, 3, and 5 J/cm2 energy densities of red and near-infrared light through different analysis such as cell viability, scratch assay, intracellular reactive oxygen species production, and ATP synthesis, nitric oxide release, temperature monitoring, and osteogenic differentiation analyses. Even though all PBM-treated groups exhibited better results compared to the control group, 5 J/cm2 energy density induced faster cell proliferation and migration at both wavelengths. The increases in ATP and NO levels as signaling molecules, and the increases in DNA, ALPase, and calcium contents as osteogenic markers were higher in the groups treated with 5 J/cm2 energy density at both wavelengths. Only a slight change was obtained in the level of intracellular ROS after any light applications. It can be concluded that NO release has a very important role together with ATP production in PBM therapy to trigger DNA synthesis, ALPase activity, and mineralization for osteogenic differentiation of the hBMSC and HUVEC co-culture at 655 and 808 nm of wavelengths.

Nerve Injury and Photobiomodulation, a Promising Opportunity: A Scoping Review on Laser Assisted Protocols for Lesions in the Oral Region

The currently available therapeutic options for restoring function and sensitivity in long-term nervous injuries pose challenges. Microsurgery interventions for direct nerve repair often lead to serious complications and limited success. Non-surgical methods, although somewhat effective, have limited benefits. These methods involve drug administration, such as with analgesics or corticosteroids. Photobiomodulation therapy (PBMT) has emerged as a promising approach based on clinical and laboratory studies. PBMT stimulates the migration and proliferation of neuronal fiber cellular aggregates, as reported in the literature. Experimental studies on animal models with peripheral nerve compression injuries have shown that PBMT can enhance the functionality of damaged nerves, preserving their activity and preventing scar tissue formation. The mechanism of action depends on the wavelength, which can positively or negatively affect photo acceptor resonances, influencing their conformation and activities. These findings suggest that photobiomodulation may accelerate and improve nerve regeneration. This review explores various methodologies used in photobiomodulation for regenerating nerve sensitivity after surgical trauma involving nerve structures, in the oral and peri-oral region. Research was conducted to evaluate which laser-assisted therapeutic protocols are used to improve the recovery of nervous sensitivity, using the JBI methodology for scoping reviews and following the PRISMA methodology.

A randomised trial of the bone formation after maxillary sinus floor augmentation with bovine hydroxyapatite (Cerabone®) and Photobiomodulation: histomorphometric and immunohistochemical analysis

Background

The use of non-autogenous biomaterial to increase bone height in the maxillary sinus has been shown to be effective, but the results are still inconclusive.

Material and Methods

Eight participants were selected and included in the research. After surgical access with osteotomy on the lateral wall of both maxillary sinuses, these were filled with Cerabone®. Then, by blind randomization, they received one of the following treatments: Filling with Cerabone® (Control group); treatment with Photobiomodulation (PBM), filling with Cerabone® and treatment with low-power laser (PBM group). Biopsies were obtained 30 days after the surgery, using a 2.8 mm internal diameter trephine bur. Qualitative and quantitative histological analyzes were performed and immunohistochemical analyzes of osteocalcin (OCN) and tartrate-resistant acid phosphatase (TRAP) were performed with scores for each of the biological events.

Results

The Cerabone® biomaterial demonstrated a high degree of biocompatibility. New bone formation was observed in both groups. In the PBM group, there was greater bone formation and newly formed tissue in an advanced state of bone maturation. The immunostaining of OCN was greater at 30 days in the PBM group than in the control. There was no significant difference in TRAP immunostaining at 30 days between the groups.

Conclusions

Low-power laser-mediated by PBM promoted greater bone formation; the newly formed tissue showed a more advanced state of bone maturation in maxillary sinuses filled with Cerabone® biomaterial and treatment with PBM, within the 30-day evaluation period. Key words:Sinus floor augmentation, dental implants, bone and bones, low-level light therapy.

Synergistic effects of integrin binding peptide (RGD) and photobiomodulation therapies on bone-like microtissues to enhance osteogenic differentiation

Bone tissue engineering aims to diversify and enhance the strategies for bone regeneration to overcome bone-related health problems. Bone mimetic peptides such as Gly-Arg-Gly-Asp-Ser (RGD) are useful tools for osteogenic differentiation. Similarly, photobiomodulation (PBM) at 600-800 nm of wavelength range improves bone tissue healing via the production of intracellular reactive oxygen species (ROS), ATP synthesis, and nitric oxide (NO) release. Besides, traditional monolayer cell culture models have limited conditions to exhibit the details of a mechanism such as a peptide or PBM therapy. However, scaffold-free microtissues (SFMs) can mimic a tissue more properly and be an efficient way to understand the mechanism of therapy via cell-cell interaction. Thus, the synergistic effects of RGD peptide (1 mM) and PBM applications (1 J/cm² energy density at 655 nm of wavelength and 5 J/cm² energy density at 808 nm of wavelength) were evaluated on SFMs formed with the co-culture of Human Bone Marrow Stem Cells (hBMSC) and Human Umbilical Vein Endothelial Cells (HUVEC) for osteogenic differentiation. Cell viability assays, mechanistic analysis, and the evaluation of osteogenic differentiation markers were performed. Combined therapies of RGD and PBM were more successful to induce osteogenic differentiation than single therapies. Especially, RGD + PBM at 655 nm group exhibited a higher capability of osteogenic differentiation via ROS production, ATP synthesis, and NO release. It can be concluded that the concomitant use of RGD and PBM may enhance bone regeneration and become a promising therapeutic tool to heal bone-related problems in clinics.

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.

Near-Infrared 810 nm Light Affects Porifera Chondrosia reniformis (Nardo, 1847) Regeneration: Molecular Implications and Evolutionary Considerations of Photobiomodulation-Animal Cell Interaction

Chemotrophic choice as a metabolic source of energy has characterised animal cell evolution. However, light interactions with animal cell photoacceptors that are able to increase energetic metabolism (photo-biomodulation (PBM)) have been previously described. In the present study, we cut three specimens of Chondrosia reniformis into four equal parts (12 fragments), and we irradiated the regenerating edge of six fragments with the previously characterised 810 nm near-infrared light, delivered at 1 W, 60 J/cm², 1 W/cm², and 60 J in a continuous-wave mode for 60 s through a flat-top hand-piece with a rounded spot-size area of 1 cm². Six fragments were irradiated with 0 W for 60 s as the controls. We performed irradiation at the time 0 h and every 24 h for a total of five administrations. We monitored the regeneration process for five days (120 h) in aquaria by examining the macroscopic and histological changes. We analysed the gene expression profile of the inflammatory processes, apoptosis, heat stress, growth factors, and collagen production and determined oxidative stress enzyme activity and the total prokaryotic symbiont content. PBM sped up C. reniformis regeneration when compared to the controls. Particularly, transforming growth factor TGF3 and TGF6 upregulation during the early phase of regeneration and TGF5 upregulation 120 h postinjury in the irradiated samples supports the positive effect of PBM in sponge tissue recovery. Conversely, the expression of TGF4, a sponge fibroblast growth factor homologue, was not affected by irradiation, indicating that multiple, independent pathways regulate the TGF genes. The results are consistent with our previous data on a wide range of organisms and humans, suggesting that PBM interaction with primary and secondary cell targets has been conserved through the evolution of life forms.

Low-level laser therapy with different irradiation methods modulated the response of bone marrow mesenchymal stem cells in vitro

Low-level laser therapy (LLLT) also known as photobiomodulation is a treatment to change cellular biological activity. The exact effects of LLLT remain unclear due to the different irradiation protocols. The purpose of this study was to investigate the effects of LLLT by three different irradiation methods on the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in vitro. BMSCs were inoculated in 24-well plates and then irradiated or not (control) with a laser using three different irradiation methods. The irradiation methods were spot irradiation, covering irradiation, and scanning irradiation according to different spot areas (0.07 cm² or 1.96 cm²) and irradiation areas (0.35 cm² or 1.96 cm²), respectively. The laser was applied three times at energy densities of 4 J/cm². The cell proliferation by CCK-8. ALP activity assay, alizarin red, and quantitative real-time polymerase chain reaction (RT-PCR) were performed to assess osteogenic differentiation and mineralization. Increases in cell proliferation was obvious following irradiation, especially for covering irradiation. The ALP activity was significantly increased in irradiated groups compared with non-irradiated control. The level of mineralization was obviously improved following irradiation, particularly for covering irradiation. RT-PCR detected significantly higher expression of ALP, OPN, OCN, and RUNX-2 in the group covering than in the others, and control is the lowest. The presented results indicate that the biostimulative effects of LLLT on BMSCs was influenced by t he irradiation method, and the covering irradiation is more favorable method to promote the proliferation and osteogenic differentiation of BMSCs.

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.

Photobiomodulation Therapy through a Novel Flat-Top Hand-Piece Prototype Improves Tissue Regeneration in Amphioxus (Branchiostoma lanceolatum): Proposal of an Ethical Model for Preclinical Screening

Despite the literature providing compelling evidence for the medical efficacy of photobiomodulation (PBM) therapy, its consistency in terms of accuracy and standardization needs improving. Identification of new technology and reliable and ethical biological models is, therefore, a challenge for researchers working on PBM. We tested the reliability of PBM irradiation through a novel delivery probe with a flat-top beam profile on the regenerating amphioxus Branchiostoma lanceolatum. The caudalmost 9 ± 1 myotomes, posterior to the anus, were excised using a sterile lancet. Animals were randomly split into three experimental groups. In the control group, the beam area was bounded with the 635-nm red-light pointer (negligible power, <0.5 mW) and the laser device was coded to irradiate 810 nm and 0 W. In Group laser-1, the beam area was bounded with the same 635-nm red-light pointer and irradiated at 810 nm, 1 W in CW for 60 s, spot-size 1 cm2, 1 W/cm2, 60 J/cm2, and 60 J; irradiation was performed every day for two weeks. In Group laser-2, the beam area was bounded with the same 635-nm red-light pointer and irradiated at 810 nm, 1 W in CW for 60 s, spot-size 1 cm2, 1 W/cm2, 60 J/cm2, and 60 J; irradiation was performed on alternate days for four weeks. We observed that PBM improved the natural wound-healing and regeneration process. The effect was particularly evident for the notochord. Daily irradiation better supported the regenerative process.

Response of osteoblastic cells to low-level laser treatment: a systematic review

Low-level laser therapy (LLLT)-induced photobiomodulation (PBM) stimulates bone tissue regeneration by inducing osteoblast differentiation and mitochondrial activation. However, the role of reactive oxygen species (ROS) in this process remains controversial. The aim of this systematic review was to collect and analyze the available literature on the cellular and molecular effects of LLLT on osteoblasts and the role of ROS in this process. A search was conducted in PubMed, ScienceDirect, Scopus, and Web of Science. Studies published in English over the past 15 years were selected. Fourteen articles were included with moderate (n = 9) and low risk of bias (n = 5). Thirteen studies reported the use of diode lasers with wavelengths (λ) between 635 and 980 nm. One study used an Nd:YAG laser (λ1064 nm). The most commonly used λ values were 808 and 635 nm. The energy densities ranged from 0.378 to 78.75 J/cm², and irradiation times from 1.5 to 300 s. Most studies found increases in proliferation, ATP synthesis, mitochondrial activity, and osteoblastic differentiation related to moderate and dose-dependent increases in intracellular ROS levels. Only two studies reported no significant changes. The data presented heterogeneity owing to the variety of LLLT protocols. Although several studies have shown a positive role of ROS in the induction of proliferation, migration, and differentiation of different cell types, further research is required to determine the specific role of ROS in the osteoblastic cell response and the molecular mechanisms involved in triggering previously reported cellular events.

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.

Effects of a Biocomplex Formed by Two Scaffold Biomaterials, Hydroxyapatite/Tricalcium Phosphate Ceramic and Fibrin Biopolymer, with Photobiomodulation, on Bone Repair

There are several treatment methods available for bone repair, although the effectiveness becomes limited in cases of large defects. The objective of this pre-clinical protocol was to evaluate the grafting of hydroxyapatite/tricalcium phosphate (BCP) ceramic biomaterial (B; QualyBone BCP^®, QualyLive, Amadora, Portugal) together with the heterologous fibrin biopolymer (FB; CEVAP/UNESP Botucatu, Brazil) and with photobiomodulation (PBM; Laserpulse^®, Ibramed, Amparo, Brazil) in the repair process of bone defects. Fifty-six rats were randomly divided into four groups of seven animals each: the biomaterial group (G1/B), the biomaterial plus FB group (G2/BFB); the biomaterial plus PBM group (G3/B + PBM), and the biomaterial plus FB plus PBM group (G4/BFB + PBM). After anesthesia, a critical defect was performed in the center of the rats’ parietal bones, then filled and treated according to their respective groups. The rats were euthanized at 14 and 42 postoperative days. Histomorphologically, at 42 days, the G4/BFB + PBM group showed a more advanced maturation transition, with more organized and mature bone areas forming concentric lamellae. A birefringence analysis of collagen fibers also showed a more advanced degree of maturation for the G4/BFB + PBM group. In the comparison between the groups, in the two experimental periods (14 and 42 days), in relation to the percentage of formation of new bone tissue, a significant difference was found between all groups (G1/B (5.42 ± 1.12; 21.49 ± 4.74), G2/BFB (5.00 ± 0.94; 21.77 ± 2.83), G3/B + PBM (12.65 ± 1.78; 29.29 ± 2.93), and G4/BFB + PBM (12.65 ± 2.32; 31.38 ± 2.89)). It was concluded that the use of PBM with low-level laser therapy (LLLT) positively interfered in the repair process of bone defects previously filled with the biocomplex formed by the heterologous fibrin biopolymer associated with the synthetic ceramic of hydroxyapatite and tricalcium phosphate.

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.

808-nm Photobiomodulation Affects the Viability of a Head and Neck Squamous Carcinoma Cellular Model, Acting on Energy Metabolism and Oxidative Stress Production

Photobiomodulation (PBM) is a form of low-dose light therapy that acts through energy delivery from non-ionizing sources. During the recent two decades, there has been tremendous progress with PBM acceptance in medicine. However, PBM effects on potential stimulation of existing malignant or pre-malignant cells remain unknown. Thus, the primary endpoint was to assess the safety of PBM treatment parameters on head and neck squamous cell carcinoma (HNSCC) proliferation or survival. The secondary endpoint was to assess any putative anti-cancer effects of PBM treatments. Cell viability, energy metabolism, oxidative stress, and pro- and anti-apoptotic markers expression were investigated on a Human Head and Neck Squamous Cell Carcinoma cellular model (OHSU-974 FAcorr cell line). PBM therapy was administered through the 810 nm diode laser (GaAlAs) device (Garda Laser, 7024 Negrar, Verona, Italy) at the powers of 0, 0.25, 0.50, 0.75, 1.00, or 1.25 W in continuous wave (CW) mode for an exposure time of 60 s with a spot-size of 1 cm² and with a distance of 1.86 cm from the cells. Results showed that 810-nm PBM affected oxidative phosphorylation in OHSU-971 FAcorr, causing a metabolic switch to anaerobic glycolysis. In addition, PBM reduced the catalase activity, determining an unbalance between oxidative stress production and the antioxidant defenses, which could stimulate the pro-apoptotic cellular pathways. Our data, at the parameters investigated, suggest the safeness of PBM as a supportive cancer therapy. Pre-clinical and clinical studies are necessary to confirm the in vitro evidence.

Photobiomodulation With Blue Laser Inhibits Bladder Cancer Progression

Blue lasers are becoming more widely used in the diagnosis and treatment of bladder cancer; however, their photobiomodulation effects on bladder cancer cells remains unclear. The purpose of the current study was to explore the photobiomodulation effect of blue laser irradiation on bladder cancer progression and the associated mechanisms. The human uroepithelial cell line SV-HUC-1 and human bladder cancer cell lines T24 and EJ were exposed to blue laser irradiation (450 nm) at various energy densities, and cell proliferation, migration, invasion, epithelial-mesenchymal transition (EMT), and the levels of the proteins associated with the MAPK pathway proteins were determined. A significant decrease in cell viability was observed in a density-dependent manner after blue laser irradiation at > 4 J/cm² in both bladder cancer cell lines. However, the blue laser did not reduce cell viability in SV-HUC-1 cells until the energy density exceeded 16 J/cm². Meanwhile, Ki67 levels, reflecting cell proliferation and senescence, were also significantly decreased after blue laser irradiation at 4 J/cm² and 8 J/cm² in the absence of cell cycle arrest. Moreover, blue laser irradiation at 4 J/cm² and 8 J/cm² caused a reduction in cell migration and invasion and also reduced the expression levels of MMP-2, MMP-9, Snail, N-cadherin, phospho-MEK and phospho-ERK, and elevated the expression levels of E-cadherin. Meanwhile ERK activator(tBHQ) significantly reversed the irradiation-induced suppression of proliferation, migration and invasion in T24 and EJ cell lines. The present study showed that blue laser irradiation inhibited bladder cancer proliferation in a density-dependent manner and inhibited bladder cancer progression by suppressing migration, invasion, and the EMT process in T24 and EJ cell lines. This inhibition was possibly mediated via suppression of the MAPK/MEK/ERK pathway. Thus, the use of a low-energy blue laser in the diagnosis and treatment of bladder cancer is possibly safe and may have an anti-tumor effect.

Role of Photobiomodulation Therapy in Neurological Primary Burning Mouth Syndrome. A Systematic Review and Meta-Analysis of Human Randomised Controlled Clinical Trials

Mitochondrial homeostasis is crucial for energy production and neuronal survival in neurological primary burning mouth syndrome (npBMS). Photobiomodulation therapy (PBMT) has been utilised in npBMS management, however, its role of intervention remains controversial. The aim of this systematic review and meta-analysis of CRD 42020198921 PROSPERO registration reference was to oversee and determine the efficacy of PBMT in patients with npBMS, identifying the gaps and bridge them by proposing recommendations for future studies purposes. PRISMA guidelines and Cochrane Collaboration recommendations followed. Various search engines employed to analyse a total of 351 studies of which 12 were included. A wide range of utilised PBM wavelengths was between 635-980 nm and the power output ranged between 30 mW and 4000 mW. A high risk of bias (RoB) was noted in 7 out of 12 included studies (58.3%), as results of qualitative analysis. Meta-analysis findings of 4 out of 12 studies showed statistically significant intergroup differences (SSID) for visual analogue scale (VAS) values (MD = -1.47; 95% CI = -2.40 to -0.53; Z = 3.07 (p = 0.002) whereas meta-analysis on 5 out of 12 studies revealed SSID for anxiety/depression and quality of life (MD = -1.47; 95% CI = -2.40 to -0.53; Z = 3.07 (p = 0.002), favouring PBMT group to the control treatment strategies. Despite the inconsistency and diversity in PBM parameters (wavelength, power, light source, spot size, emission mode, energy per point, total energy) and treatment protocols (exposure time, number of sessions, time interval between sessions, treatment duration)-majority of the included studies showed positive PBM results. The high RoB and meta-analytical heterogeneity in the eligible studies warrant the necessity to perform well-designed and robust RCTs after acknowledging the drawbacks of the available scientific literature and addressing our suggested recommendations highlighted in our review.

Effect of Photobiomodulation on Periodontal Ligament Cells Under Inflamed and Nutrient-Deficient Conditions Simulating Damaged Cells of Avulsed Teeth: An In Vitro Study

Background: The prognosis of replanted teeth is depended on the vitality of periodontal ligament cells residual on the root surface. Photobiomodulation has photobiological effects that can promote cell vitality. The study aimed to explore the effect of photobiomodulation on the periodontal ligament cells under inflamed or starved conditions mimicking clinically damaged periodontal ligament cells of avulsed teeth and provide the adjuvant procedure for tooth replantation. Materials and methods: Normal, starved, or inflamed periodontal ligament cells were irradiated with an 808 nm laser at densities of 0, 1, 3, 5, or 10 J/cm². The cell counting kit-8 (CCK-8) assay and scratch test were applied to determine the effects on the proliferation and migration of cells. Anti-inflammatory effects were assessed according to the mRNA expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) measured by reverse-transcription polymerase chain reaction. Osteogenic capacity was evaluated by alkaline phosphatase (ALP) staining, ALP activity assay, Alizarin Red S staining, and ALP and osteocalcin (OCN) mRNA expression. Results: The CCK-8 assay and scratch test demonstrated that the 808 nm laser significantly promoted proliferation and migration of normal condition periodontal ligament cells at a density of 3 J/cm² versus 5 J/cm² under the starved and inflamed conditions. Moreover, the 808 nm laser had anti-inflammatory effects and promoted osteogenesis of periodontal ligament cells at 3 J/cm² under normal conditions, while photobiomodulation at 5 J/cm² upregulated the osteogenesis of periodontal ligament cells under starved and inflamed conditions. Conclusions: The photobiomodulation of 808 nm laser reduced inflammation and improved the proliferation, migration, and osteogenesis of normal, starved, and inflamed periodontal ligament cells. These effects required a higher energy density under starved or inflamed conditions compared with normal conditions. The photobiomodulation of 808 nm has a potential application in root surface treatment for replanted teeth.

Recovery from Idiopathic Facial Paralysis (Bell’s Palsy) Using Photobiomodulation in Patients Non-Responsive to Standard Treatment: A Case Series Study

Diminished facial movement and marked facial asymmetry can lead to a consistent psychological burden. Bell′s palsy (BP) is one of the most common causes of facial nerve illness, which comes with unilateral acute facial paresis. Nowadays, no clear guidelines for treating BP are available. We carried out a case series study to test the efficacy of photobiomodulation (PBM) therapy in patients with BP non-responsive to standard treatment. The study was experimentally performed at the Department of Surgical and Diagnostic Sciences, University of Genoa (Genoa, Italy), in accordance with case report guidelines. Patients were referred to our department by colleagues for evaluation to be included in the case series because no consistent improvement was observed at least 3 months from the diagnosis of BP. All the patients interrupted their pharmacological therapy before the initiation of PBM therapy. PBM therapy (808 nm, 1 W irradiated in continuous-wave for 60 s on spot-size 1 cm2; 1 W/cm2; 60 J/cm2; and 60 J) was administered every 2 days until complete resolution. Evaluation of the House-Brackmann scale was performed before and after treatments. Fourteen patients were screened as eligible for the study. Patients were Caucasians (36% females and 64% males) with a mean age ± standard deviation of 56.07 ± 15.21 years. Eleven patients out of 14, who experienced BP a maximum of 6 months, completely recovered through PBM. The three patients that did not show improvement were those who had experienced BP for years. PBM could be a supportive therapy for the management of BP in patients non-responsive to standard treatment. However, randomized controlled trials are necessary to sustain our encouraging results, exclude bias, and better explain the boundary between the time from diagnosis and the recovery of BP through PBM therapy.

Photobiomodulation by Near-Infrared 980-nm Wavelengths Regulates Pre-Osteoblast Proliferation and Viability through the PI3K/Akt/Bcl-2 Pathway

BACKGROUND

bone tissue regeneration remains a current challenge. A growing body of evidence shows that mitochondrial dysfunction impairs osteogenesis and that this organelle may be the target for new therapeutic options. Current literature illustrates that red and near-infrared light can affect the key cellular pathways of all life forms through interactions with photoacceptors within the cells' mitochondria. The current study aims to provide an understanding of the mechanisms by which photobiomodulation (PBM) by 900-nm wavelengths can induce in vitro molecular changes in pre-osteoblasts.

METHODS

The PubMed, Scopus, Cochrane, and Scholar databases were used. The manuscripts included in the narrative review were selected according to inclusion and exclusion criteria. The new experimental set-up was based on irradiation with a 980-nm laser and a hand-piece with a standard Gaussian and flat-top beam profile. MC3T3-E1 pre-osteoblasts were irradiated at 0.75, 0.45, and 0.20 W in continuous-wave emission mode for 60 s (spot-size 1 cm²) and allowed to generate a power density of 0.75, 0.45, and 0.20 W/cm² and a fluence of 45, 27, and 12 J/cm², respectively. The frequency of irradiation was once, three times (alternate days), or five times (every day) per week for two consecutive weeks. Differentiation, proliferation, and cell viability and their markers were investigated by immunoblotting, immunolabelling, fluorescein-FragELTM-DNA, Hoechst staining, and metabolic activity assays.

RESULTS AND CONCLUSIONS

The 980-nm wavelength can photobiomodulate the pre-osteoblasts, regulating their metabolic schedule. The cellular signal activated by 45 J/cm², 0.75 W and 0.75 W/cm² consist of the PI3K/Akt/Bcl-2 pathway; differentiation markers were not affected, nor do other parameters seem to stimulate the cells. Our previous and present data consistently support the window effect of 980 nm, which has also been described in extracted mitochondria, through activation of signalling PI3K/Akt/Bcl-2 and cyclin family, while the Wnt and Smads 2/3-β-catenin pathway was induced by 55 J/cm², 0.9 W and 0.9 W/cm².

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.

Terahertz pulses induce segment renewal via cell proliferation and differentiation overriding the endogenous regeneration program of the earthworm Eisenia andrei

Terahertz (THz) irradiation of excised Eisenia andrei earthworms is shown to cause overriding of the genetically determined, endogenously mediated segment renewing capacity of the model animal. Single-cycle THz pulses of 5 µJ energy, 0.30 THz mean frequency, 293 kV/cm peak electric field, and 1 kHz repetition rate stimulated the cell proliferation (indicated by the high number of mitotic cells) and both histogenesis and organogenesis, producing a significantly higher number of regenerated segments. The most conspicuous alteration in THz-treated animals was the more intense development of the new central nervous system and blood vessels. These results clearly demonstrate that THz pulses are capable to efficiently trigger biological processes and suggest potential applications in medicine.

Understanding COVID-19 Pandemic: Molecular Mechanisms and Potential Therapeutic Strategies. An Evidence-Based Review

Initially, the SARS-CoV-2 virus was considered as a pneumonia virus; however, a series of peer reviewed medical papers published in the last eight months suggest that this virus attacks the brain, heart, intestine, nervous and vascular systems, as well the blood stream. Although many facts remain unknown, an objective appraisal of the current scientific literature addressing the latest progress on COVID-19 is required. The aim of the present study was to conduct a critical review of the literature, focusing on the current molecular structure of SARS-CoV-2 and prospective treatment modalities of COVID-19. The main objectives were to collect, scrutinize and objectively evaluate the current scientific evidence-based information, as well to provide an updated overview of the topic that is ongoing. The authors underlined potential prospective therapies, including vaccine and phototherapy, as a monotherapy or combined with current treatment modalities. The authors concluded that this review has produced high quality evidence, which can be utilized by the clinical scientific community for future reference, as the knowledge and understanding of the SARS-CoV-2 virus are evolving, in terms of its epidemiological, pathogenicity, and clinical manifestations, which ultimately map the strategic path, towards an effective and safe treatment and production of a reliable and potent vaccine.

Effects of photobiomodulation on bone defects grafted with bone substitutes: A systematic review of in vivo animal studies

A present, photobiomodulation therapy (PBMT) effectiveness in enhancing bone regeneration in bone defects grafted with or without biomaterials is unclear. This systematic review (PROSPERO, ref. CRD 42019148959) aimed to critically appraise animal in vivo published data and present the efficacy of PBMT and its potential synergistic effects on grafted bone defects. MEDLINE, CCCT, Scopus, Science Direct, Google Scholar, EMBASE, EBSCO were searched, utilizing the following keywords: bone repair; low-level laser therapy; LLLT; light emitting diode; LEDs; photobiomodulation therapy; in vivo animal studies, bone substitutes, to identify studies between 1994 and 2019. After applying the eligibility criteria, 38 papers included where the results reported according to "PRISMA." The results revealed insufficient and incomplete PBM parameters, however, the outcomes with or without biomaterials have positive effects on bone healing. In conclusion, in vivo animal studies with a standardized protocol to elucidate the effects of PBMT on biomaterials are required initially prior to clinical studies.

In Vitro Cytological Responses against Laser Photobiomodulation for Periodontal Regeneration

Periodontal disease is a chronic inflammatory disease caused by periodontal bacteria. Recently, periodontal phototherapy, treatment using various types of lasers, has attracted attention. Photobiomodulation, the biological effect of low-power laser irradiation, has been widely studied. Although many types of lasers are applied in periodontal phototherapy, molecular biological effects of laser irradiation on cells in periodontal tissues are unclear. Here, we have summarized the molecular biological effects of diode, Nd:YAG, Er:YAG, Er,Cr:YSGG, and CO₂ lasers irradiation on cells in periodontal tissues. Photobiomodulation by laser irradiation enhanced cell proliferation and calcification in osteoblasts with altering gene expression. Positive effects were observed in fibroblasts on the proliferation, migration, and secretion of chemokines/cytokines. Laser irradiation suppressed gene expression related to inflammation in osteoblasts, fibroblasts, human periodontal ligament cells (hPDLCs), and endothelial cells. Furthermore, recent studies have revealed that laser irradiation affects cell differentiation in hPDLCs and stem cells. Additionally, some studies have also investigated the effects of laser irradiation on endothelial cells, cementoblasts, epithelial cells, osteoclasts, and osteocytes. The appropriate irradiation power was different for each laser apparatus and targeted cells. Thus, through this review, we tried to shed light on basic research that would ultimately lead to clinical application of periodontal phototherapy in the future.

The effects of 808-nm near-infrared laser light irradiation on actin cytoskeleton reorganization in bone marrow mesenchymal stem cells

Tailoring the cell organelles and thus changing cell homeostatic behavior has permitted the discovery of fascinating metabolic features enabling enhanced viability, differentiation, or quenching inflammation. Recently, photobiomodulation (PBM) has been accredited as an effective cell manipulation technique with promising therapeutic potential. In this prospective, in vitro results revealed that 808-nm laser light emitted by a hand-piece with a flat-top profile at an irradiation set up of 60 J/cm2 (1 W, 1 W/cm²; 60 s, continuous wave) regulates bone marrow stromal cell (BMSC) differentiation toward osteogenesis. Considering the importance of actin cytoskeleton reorganization, which controls a range of cell metabolic activities, comprising shape change, proliferation and differentiation, the aim of the current work is to assess whether PBM therapy, using a flat-top hand-piece at higher-fluence irradiation on BMSCs, is able to switch photon signals into the stimulation of biochemical/differentiating pathways involving key activators that regulate de novo actin polymerization. Namely, for the first time, we unearthed the role of the flat-top hand-piece at higher-fluence irradiation on cytoskeletal characteristics of BMSCs. These novel findings meet the needs of novel therapeutically protocols provided by laser treatment and the manipulation of BMSCs as anti-inflammatory, osteo-inductive platforms.

Photobiomodulation effects on osteogenic differentiation of adipose-derived stem cells

Increasing interest has been observed in the use of photobiomodulation (PBM) to enhance the proliferation of stem cells and induce their differentiation. The effects of PBM at two different wavelengths (635 and 809 nm) with three different energy densities (0.5, 1 and 2 J/cm²) on the osteogenic differentiation of adipose-derived stem cells (ADSC) were investigated. Cell viability and proliferation were evaluated by MTT and Alamar Blue assays. Osteoblast differentiation were assessed by alkaline phosphatase (ALP) activity, Alizarin red staining and reverse-transcription polymerase chain reaction (RT-PCR) for the expression of collagen type I (COL1A), ALP and osteocalcin. 635 nm and 809 nm laser irradiation had no effect on the cell viability on days 7 and 14, except for 0.5 J/cm² group at 14th day after 635 nm irradiation (p < 0.05). Cell proliferation was not changed significantly. Mineralization was increased significantly in 809 nm laser groups but no enhancement was detected in the osteogenic differentiation by ALP activity and gene expression results. In 0.5 and 1 J/cm² groups, ALP and COL1A expressions were down regulated at day 7 after 809 nm laser exposure. These results suggest that PBM may alter osteogenic differentiation of ADSC and increase mineralization but further investigation is needed to define adequate parameters.

The Effect of Photobiomodulation Therapy on the Differentiation, Proliferation, and Migration of the Mesenchymal Stem Cell: A Review

Introduction: The purpose of this study is to investigate the effect of a low-power laser on the proliferation, migration, differentiation of different types of mesenchymal stem cells (MSCs) in different studies. Methods: The relevant articles that were published from 2004 to 2019 were collected from the sources of PubMed, Scopus, and only the articles specifically examining the effect of a lowpower laser on the proliferation, differentiation, and migration of the MSCs were investigated. Results: After reviewing the literature, only 42 articles were found relevant. Generally, most of the studies demonstrated that different laser parameters increased the proliferation, migration, and differentiation of the MSCs, except the results of two studies which were contradictory. In fact, changing the parameters of a low-power laser would affect the results. On the other hand, the source of the stem cells was reported as a key factor. In addition, the combination of lasers with other therapeutic approaches was found to be more effective. Conclusion: The different parameters of lasers has been found to be effective in the proliferation, differentiation, and migration of the MSCs and in general, a low-power laser has a positive effect on the MSCs, helping to improve different disease models.

The 808 nm and 980 nm infrared laser irradiation affects spore germination and stored calcium homeostasis: A comparative study using delivery hand-pieces with standard (Gaussian) or flat-top profile

Photobiomodulation relies on the transfer of energy from incident photons to a cell photoacceptor. For many years the concept of photobiomodulation and its outcome has been based upon a belief that the sole receptor within the cell was the mitochondrion. Recently, it has become apparent that there are other photoacceptors operating in different regions of the electromagnetic spectrum. Alternative photoacceptors would appear to be water and mechanisms regulating calcium homeostasis, despite a direct effect of laser photonic energy on intracellular calcium concentration outwith mitochondrial activity or influence, have not been clearly demonstrated. Therefore, to increase the knowledge of intracellular‑calcium and laser photon interaction, as well as to demonstrate differences in irradiation profiles with modern hand-pieces, we tested and compared the photobiomodulatory effect of 808 nm and 980 nm diode laser light by low- and higher-energy (60s, 100 mW/cm², 100 mW/cm², 500 mW/cm², 1000 mW/cm², 1500 mW/cm², 2000 mW/cm²) irradiated with a "standard" (Gaussian fluence distribution) hand-piece or with a "flat-top" (uniform fluence) hand-piece. For this purpose, we used the eukaryote unicellular-model Dictyostelium discoideum. The 808 nm and 980 nm infrared laser light, at the energy tested directly affect the stored Ca²⁺ homeostasis, independent of the mitochondrial respiratory chain activities. From an organism perspective, the effect on Ca²⁺-dependent signal transduction as the regulator of spore germination in Dictyostelium, demonstrates how a cell can respond quickly to the correct laser photonic stimulus through a different cellular pathway than the known light-chromophore(mitochondria) interaction. Additionally, both hand-piece designs tested were able to photobiomodulate the D. discoideum cell; however, the hand-piece with a flat-top profile, through uniform fluence levels allows more effective and reproducible effects.

A Comparative Study Between the Effectiveness of 980 nm Photobiomodulation Delivered by Hand-Piece With Gaussian vs. Flat-Top Profiles on Osteoblasts Maturation

Photobiomodulation (PBM) is a clinically accepted tool in regenerative medicine and dentistry to improve tissue healing and repair and to restore the functional disability. The current in vitro study aimed to investigate the photobiomodulatory effects of 980 nm wavelength (the real energy at the target: ~0.9 W, ~0.9 W/cm2, 60 s, ~55 J/cm2 and a single energy ~55 J in CW) on MC3T3-E1 pre-osteoblast, delivered with flattop profile in comparison to the standard profile. The laser groupings and their associated energies were: Group 1 - once per week (total energy 110 J); Group 2 - three times per week (alternate day) (total energy 330 J); Group 3 - five times per week (total energy 550 J). The metabolic activity and the osteoblasts maturation were analyzed by alkaline phosphatase assay, alizarin red S histological staining, immunoblot and/or double immunolabeling analysis for Bcl2, Bax, Runx-2, Osx, Dlx5, osteocalcin, and collagen Type 1. Our data, for the first time, prove that laser irradiation of 980 nm wavelength with flat-top beam profile delivery system, compared to standard-Gaussian profile, has improved photobiomodulatory efficacy on pre-osteoblastic cells differentiation. Mechanistically, the irradiation enhances the pre-osteoblast differentiation through activation of Wnt signaling and activation of Smads 2/3-βcatenin pathway.

Near-infrared laser photons induce glutamate release from cerebrocortical nerve terminals

Although photons have been repeatedly shown to affect the functioning of the nervous system, their effects on neurotransmitter release have never been investigated. We exploited in vitro models that allow effects involving neuron-astrocyte network functioning to be detected (mouse cerebrocortical slices) and dissected these effects at cerebrocortical nerve endings and astrocyte processes. Infrared light proved able to induce glutamate release by stimulating glutamatergic nerve endings.

Role of photobiomodulation on the activation of the Smad pathway via TGF-β in wound healing

Wound healing is an essential process in which the separated or destroyed tissue attempts to restore itself into its normal state. In some instances, healing is prolonged and remains stagnant in the inflammatory phase, and is referred to as a chronic wound. At a cellular and molecular level, many factors are required during the process of successful wound healing, such as cytokines, polypeptide growth factors and components of the extracellular matrix (ECM). Transforming growth factor-beta (TGF-β) is considered as one of the essential growth factors in wound healing. Working through the Smad pathway, it is the main inducer of fibroblast differentiation which is essential for wound healing. Photobiomodulation (PBM) shows significant advantages in wound healing, and may stimulate cellular processes and tissue regeneration that results in an increase in growth factors and a decrease in inflammatory cytokines. Moreover, it leads to enhanced cell proliferation, migration, angiogenesis, and increased adenosine triphosphate (ATP) and cytochrome C oxidase (CCO) activity. In this review paper, we discuss the effects of PBM and its role on the activation of the TGF-β/Smad pathway in the process of wound healing.

Red (635 nm), Near-Infrared (808 nm) and Violet-Blue (405 nm) Photobiomodulation Potentiality on Human Osteoblasts and Mesenchymal Stromal Cells: A Morphological and Molecular In Vitro Study

Photobiomodulation (PBM) has been used for bone regenerative purposes in different fields of medicine and dentistry, but contradictory results demand a skeptical look for its potential benefits. This in vitro study compared PBM potentiality by red (635 ± 5 nm) or near-infrared (NIR, 808 ± 10 nm) diode lasers and violet-blue (405 ± 5 nm) light-emitting diode operating in a continuous wave with a 0.4 J/cm² energy density, on human osteoblast and mesenchymal stromal cell (hMSC) viability, proliferation, adhesion and osteogenic differentiation. PBM treatments did not alter viability (PI/Syto16 and MTS assays). Confocal immunofluorescence and RT-PCR analyses indicated that red PBM (i) on both cell types increased vinculin-rich clusters, osteogenic markers expression (Runx-2, alkaline phosphatase, osteopontin) and mineralized bone-like nodule structure deposition and (ii) on hMSCs induced stress fiber formation and upregulated the expression of proliferation marker Ki67. Interestingly, osteoblast responses to red light were mediated by Akt signaling activation, which seems to positively modulate reactive oxygen species levels. Violet-blue light-irradiated cells behaved essentially as untreated ones and NIR irradiated ones displayed modifications of cytoskeleton assembly, Runx-2 expression and mineralization pattern. Although within the limitations of an in vitro experimentation, this study may suggest PBM with 635 nm laser as potential effective option for promoting/improving bone regeneration.

Does Low-Level Laser Therapy Affect Recovery of Lingual and Inferior Alveolar Nerve Injuries?

PURPOSE

Iatrogenic damage to the inferior alveolar nerve (IAN) and lingual nerve (LN) may occur during routine oral and maxillofacial surgery procedures. The primary aim of this study was to determine, using a prospective, double-blind, randomized controlled clinical trial, whether the proportion of nerve-injured patients with postoperative neurosensory improvement over a 3-month period differed significantly between a control group and a low-level laser therapy (LLLT) group.

PATIENTS AND METHODS

The study sample consisted of 35 patients with iatrogenic nerve injury due to third molar odontectomy, dental implant placement, or local anesthetic injection. The investigators used a randomized, double-blind laser delivery system to administer either placebo or LLLT to patients who met the inclusion criteria. The outcome variable of neurosensory improvement was defined as a minimum 1-unit increase from baseline in visual analog scale rating and was based on standard objective clinical neurosensory testing. Study variables included the affected nerve (IAN or LN) and time from injury to treatment (3 to 12 months or >12 months). Univariate statistical analysis (χ² test) was performed to determine significance between the groups.

RESULTS

Neurosensory improvement was observed in 46.7% of the LLLT patients, who showed at least a 1-unit improvement at 3 months, compared with 38.5% improvement for controls (P = .66), regardless of the specific nerve involved (IAN or LN). In addition, no observed difference was noted between the study groups based on time from injury to treatment.

CONCLUSIONS

This study failed to provide sufficient evidence to conclude that a difference in neurosensory improvement exists between the LLLT and placebo groups with IAN or LN injuries. However, this study is unique in the prospective double-blind study design and comprehensive neurosensory testing protocols. There is a continued need for further clinical studies on LLLT in oral and maxillofacial surgery nerve injuries.