Low-energy laser irradiation promotes the survival and cell cycle entry of skeletal muscle satellite cells

Photobiomodulation therapy moderates cancer cachexia-associated muscle wasting through activating PI3K/AKT/FoxO3a pathway

Cancer cachexia-associated muscle wasting as a multifactorial wasting syndrome, is an important factor affecting the long-term survival rate of tumor patients. Photobiomodulation therapy (PBMT) has emerged as a promising tool to cure and prevent many diseases. However, the effect of PBMT on skeletal muscle atrophy during cancer progression has not been fully demonstrated yet. Here, we found PBMT alleviated the atrophy of myotube diameter induced by cancer cells in vitro, and prevented cancer-associated muscle atrophy in mice bearing tumor. Mechanistically, the alleviation of muscle wasting by PBMT was found to be involved in inhibiting E3 ubiquitin ligases MAFbx and MuRF-1. In addition, transcriptomic analysis using RNA-seq and GSEA revealed that PI3K/AKT pathway might be involved in PBMT-prevented muscle cachexia. Next, we showed the protective effect of PBMT against muscle cachexia was totally blocked by AKT inhibitor in vitro and in vivo. Moreover, PBMT-activated AKT promoted FoxO3a phosphorylation and thus inhibiting the nucleus entry of FoxO3a. Lastly, in cisplatin-treated muscle cachexia model, PBMT had also been shown to ameliorate muscle atrophy through enhancing PI3K/AKT pathway to suppress MAFbx and MuRF-1 expression. These novel findings revealed that PBMT could be a promising therapeutic approach in treating muscle cachexia induced by cancer.

Laser light: Illuminating the path to enhanced periodontal care

The utilisation of laser technology in the realm of periodontal care represents a significant advancement in clinical practice. This article delves into the historical context of laser therapy in medicine, from its inception in 1960 to its evolution into low-level laser therapy (LLLT). LLLT, often referred to as photobiomodulation (PBM), has garnered attention due to its potential to enhance periodontal treatment outcomes. The article thoroughly examines the mechanisms of action of photobiomodulation therapy PBM(T), covering its impact on cellular and tissue levels. The authors explore the evidence-based recommendations for the use of PBM(T) in periodontal care, shedding light on its potential to improve periodontal conditions, especially when applied as an adjunct to conventional treatments. They investigate the role of PBM(T) in individuals and its possible contribution to periodontal health. Additionally, the article delves into its application in periodontal regenerative procedures and its ability to expedite soft tissue wound healing and the effects of PBM(T) in reducing periodontal inflammation and mitigating post-periodontal surgery discomfort. In conclusion, the article calls for enhanced clinical research to streamline laser procedures, develop antimicrobial photodynamic therapy, and conduct well-designed randomised controlled trials (RCTs). It also emphasises the importance of understanding the impact of laser therapy on therapeutic and biological goals, the potential to reduce invasive procedures, and the necessity of adequate research funding.

Photobiomodulation for Neurodegenerative Diseases: A Scoping Review

Neurodegenerative diseases involve the progressive dysfunction and loss of neurons in the central nervous system and thus present a significant challenge due to the absence of effective therapies for halting or reversing their progression. Based on the characteristics of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD), which have prolonged incubation periods and protracted courses, exploring non-invasive physical therapy methods is essential for alleviating such diseases and ensuring that patients have an improved quality of life. Photobiomodulation (PBM) uses red and infrared light for therapeutic benefits and functions by stimulating, healing, regenerating, and protecting organizations at risk of injury, degradation, or death. Over the last two decades, PBM has gained widespread recognition as a non-invasive physical therapy method, showing efficacy in pain relief, anti-inflammatory responses, and tissue regeneration. Its application has expanded into the fields of neurology and psychiatry, where extensive research has been conducted. This paper presents a review and evaluation of studies investigating PBM in neurodegenerative diseases, with a specific emphasis on recent applications in AD and PD treatment for both animal and human subjects. Molecular mechanisms related to neuron damage and cognitive impairment are scrutinized, offering valuable insights into PBM's potential as a non-invasive therapeutic strategy.

Pulsed Red and Blue Photobiomodulation for the Treatment of Thigh Contusions and Soft Tissue Injury: A Randomized Controlled Trial

CONTEXT

Contusion and soft tissue injuries are common in sports. Photobiomodultion, light and laser therapy, is an effective aid to increase healing rates and improve function after various injury mechanisms. However, it is unclear how well photobiomodulation improves function after a contusion soft tissue injury. This study aimed to determine the effects of a pulsed red and blue photobiomodulation light patch on muscle function following a human thigh contusion injury.

DESIGN

Single-blinded randomized control trial design.

METHODS

We enrolled 46 healthy participants. Participants completed 5 visits on consecutive days. On the first visit, participants completed a baseline isokinetic quadriceps strength testing protocol at 60°/s and 180°/s. On the second visit, participants were struck in the rectus femoris of the anterior thigh with a tennis ball from a serving machine. Immediately following, participants were treated for 30 minutes with an active or placebo photobiomodulation patch (CareWear light patch system, CareWear Corp). Following the treatment, participants completed the same isokinetic quadriceps strength testing protocol. Participants completed the treatment and isokinetic quadriceps strength test during the following daily visits. We normalized the data by calculating the percent change from baseline. We used a mixed model analysis of covariance, with sex as a covariate, to determine the difference between treatment groups throughout the acute recovery process.

RESULTS

We found the active photobiomodulation treatment significantly increased over the placebo group, quadriceps peak torque during the 180°/s test (P = .030), and average power during both the 60°/s (P = .041) and 180°/s (P ≤ .001) assessments. The mean peak torque and average power of 180°/s, at day 4, exceeded the baseline levels by 8.9% and 16.8%, respectively.

CONCLUSIONS

The red and blue photobiomodulation light patch improved muscle strength and power during the acute healing phase of a human thigh contusion injury model.

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

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

Efficacy of Low-Level Laser Therapy in a Rabbit Model of Rhinosinusitis

Little is known about alternative treatment options for rhinosinusitis (RS). We aimed to evaluate the efficacy of low-level laser therapy (LLLT) for RS in experimentally induced rabbit models of RS. A total of 18 rabbits were divided into four groups: a negative control group (n = 3), an RS group without treatment (n = 5, positive control group), an RS group with natural recovery (n = 5, natural recovery group), and an RS group with laser irradiation (n = 5, laser-treated group). Computed tomography and histopathological staining were performed for each group. mRNA and protein expression levels of local cytokines (IFN-γ, IL-17, and IL-5) were also measured. Tissue inflammation revealed a significant improvement in the laser-treated group compared with the RS and natural recovery groups (p < 0.01). In addition, sinus opacification in the CT scans and cytokine expression was reduced in the laser-treated group, though without statistical significance. LLLT could be an effective option for the management of RS concerning radiological, histological, and molecular parameters.

Anti-inflammatory effect of green photobiomodulation in human adipose-derived mesenchymal stem cells

Photo biomodulation (PBM) as a non-invasive and safe treatment has been demonstrated the anti-inflammatory potential in a variety of cell types, including stem cells. However, further investigations using different laser parameters combined with more accurate methods such as quantitative measurement of inflammatory gene expression at the mRNA level are still necessary. The aim of this study was to evaluate the effect of 532 nm green laser on cell proliferation as well as expression of inflammatory genes in human adipose-derived mesenchymal stem cells (hADMSCs) using RNA sequencing (RNA-seq) technique and confirmatory RT-PCR. hADMSCs were cultured in DMEM low glocuse medium with 10% fetal bovine serum until the fourth passage. Cultured cells were divided in two groups: control group (no laser irradiation) and laser group, irradiated with 532 nm laser at 44 m J/cm² with an output power of 50 mW and a density of 6 mW/cm², every other day, 7 s each time. The cell viability was assessed using MTT assay 24 h after each irradiation on days 3, 5, and 7 after cell seeding, followed by performing RNA-seq and RT-PCR. The MTT assay showed that PBM increased cell proliferation on day 5 after irradiation compared to day 3 and decreased on day 7 compared to day 5. In addition, gene expression analysis in hADMSCs using RNA-seq revealed down-regulation of inflammatory genes including CSF2, CXCL2, 3, 5, 6, 8, and CCL2, 7. These results indicate that 532 nm PBM with the parameters used in this study has a time-dependent effect on hADMSCs proliferation as well as anti-inflammatory potential.

Enhancing health span: muscle stem cells and hormesis

Sarcopenia is a significant public health and medical concern confronting the elderly. Considerable research is being directed to identify ways in which the onset and severity of sarcopenia may be delayed/minimized. This paper provides a detailed identification and assessment of hormetic dose responses in animal model muscle stem cells, with particular emphasis on cell proliferation, differentiation, and enhancing resilience to inflammatory stresses and how this information may be useful in preventing sarcopenia. Hormetic dose responses were observed following administration of a broad range of agents, including dietary supplements (e.g., resveratrol), pharmaceuticals (e.g., dexamethasone), endogenous ligands (e.g., tumor necrosis factor α), environmental contaminants (e.g., cadmium) and physical agents (e.g., low level laser). The paper assesses both putative mechanisms of hormetic responses in muscle stem cells, and potential therapeutic implications and application(s) of hormetic frameworks for slowing muscle loss and reduced functionality during the aging process.

Total mRNA and primary human myoblasts' in vitro cell cycle progression distinguishes between clones

Satellite cells are generally quiescent in vivo. Once activated, progression through the cell cycle begins. Immortalised myoblasts from a single cell line are fairly homogenous in culture, but primary human myoblasts (PHMs) demonstrate heterogeneity. This phenomenon is poorly understood however may impact on PHM expansion. This study aimed to evaluate cell cycle transition from growth to synthesis phases of the cell cycle (G1 to S phase) and total mRNA relevant to this transition in PHM clones derived from 2 donor biopsies. Proportions of cells transitioning from G1 to S phase were evaluated at 2-hourly intervals for 24 h (n = 3 for each) and total mRNA quantified. Both PHM clones revealed an exponential transition from G1 to S phase over time, with a significantly slower rate for PHMs from S9.1 compared to S6.3, which had a higher proportion of PHMs in S phase for most time-points (p < 0.05). After 24 h the proportion of PHMs in S phase was ∼13% (S6.3) compared to ∼22% (S9.1). Gene transcription increased as cells progressed from G1 to S phase. Although total RNA increased with similar linearity in both clones, S6.3 PHMs had consistently (10 out of 12 time points) significantly higher concentrations. Validating the 2-hourly assessment over 24 h, a 4-hourly assessment from 8 to 32 h revealed similar differences but included the beginning of a plateau. This study demonstrates that PHMs from different donors differ in both cell cycle progression and overall transcriptome revealing new aspects in the heterogeneity of isolated satellite cells in vitro.

Combined application of chondroitinase ABC and photobiomodulation with low-intensity laser on the anal sphincter repair in rabbit

Background

Photobiomodulation with low-intensity laser (LIL) and chondroitinase ABC (ChABC) can repair damaged muscle tissue, so the aim of this study was to investigate the effect of co-administration of these two factors on anal sphincter repair in rabbits.

Methods

Male rabbits were studied in 5 groups (n = 7): Control (intact), sphincterotomy, laser, ChABC and laser + ChABC. 90 days after intervention were evaluated resting and maximum squeeze pressures, number of motor units, collagen amount, markers of muscle regeneration and angiogenesis.

Results

Resting pressure in the Laser + ChABC group was higher than the sphincterotomy, laser and ChABC groups (p < 0.0001). Maximum squeeze pressure in the all study groups was higher than sphincterotomy group (p < 0.0001). In the laser + ChABC and ChABC groups, motor unit numbers were more than the sphincterotomy group (p < 0.0001). Collagen content was significantly decreased in the laser (p < 0.0001) and laser + ChABC groups. ACTA1 (p = 0.001) and MHC (p < 0.0001) gene expression in the Laser + ChABC group were more than the laser or ChABC alone. VEGFA (p = 0.009) and Ki67 mRNA expression (p = 0.01) in the Laser + ChABC group were more than the laser group, But vimentin mRNA expression (p < 0.0001) was less than the laser group.

Conclusion

Co-administration of ChABCs and photobiomodulation with LIL appears to improve the tissue structure and function of the anal sphincter in rabbits more than when used alone.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-021-02047-2.

The Effects of Photobiomodulation on Bone Defect Repairing in a Diabetic Rat Model

The purpose of this study is to examine the prospective therapeutic effects of photobiomodulation on the healing of bone defects in diabetic mellitus (DM) using rat models to provide basic knowledge of photobiomodulation therapy (PBMT) during bone defect repair. For in vitro study, an Alizzarin red stain assay was used to evaluate the effect of PBMT on osteogenic differentiation. For in vivo study, micro-computed tomography (microCT) scan, H&E and IHC stain analysis were used to investigate the effect of PBMT on the healing of the experimental calvarial defect (3 mm in diameter) of a diabetic rat model. For in vitro study, the high glucose groups showed lower osteogenic differentiation in both irradiated and non-irradiated with PBMT when compared to the control groups. With the PBMT, all groups (control, osmotic control and high glucose) showed higher osteogenic differentiation when compared to the non-irradiated groups. For in vivo study, the hyperglycemic group showed significantly lower bone regeneration when compared to the control group. With the PBMT, the volume of bone regeneration was increasing and back to the similar level of the control group. The treatment of PBMT in 660 nm could improve the bone defect healing on a diabetic rat calvarial defect model.

Transcranial Laser Photobiomodulation Improves Intracellular Signaling Linked to Cell Survival, Memory and Glucose Metabolism in the Aged Brain: A Preliminary Study

Aging is often accompanied by exacerbated activation of cell death-related signaling pathways and decreased energy metabolism. We hypothesized that transcranial near-infrared laser may increase intracellular signaling pathways beneficial to aging brains, such as those that regulate brain cell proliferation, apoptosis, and energy metabolism. To test this hypothesis, we investigated the expression and activation of intracellular signaling proteins in the cerebral cortex and hippocampus of aged rats (20 months old) treated with the transcranial near-infrared laser for 58 consecutive days. As compared to sham controls, transcranial laser treatment increased intracellular signaling proteins related to cell proliferation and cell survival, such as signal transducer and activator of transcription 3 (STAT3), extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), p70 ribosomal protein S6 kinase (p70S6K) and protein kinase B (PKB), also known as Akt that is linked to glucose metabolism. In addition, ERK is linked to memory, while ERK and JNK signaling pathways regulate glucose metabolism. Specifically, the laser treatment caused the activation of STAT3, ERK, and JNK signaling proteins in the cerebral cortex. In the hippocampus, the laser treatment increased the expression of p70S6K and STAT3 and the activation of Akt. Taken together, the data support the hypothesis that transcranial laser photobiomodulation improves intracellular signaling pathways linked to cell survival, memory, and glucose metabolism in the brain of aged rats.

Photobiomodulation therapy for thrombocytopenia by upregulating thrombopoietin expression via the ROS-dependent Src/ERK/STAT3 signaling pathway

BACKGROUND

Chemotherapy-induced thrombocytopenia (CIT) can increase the risk of bleeding, which may delay or prevent the administration of anticancer treatment schedules. Photobiomodulation therapy (PBMT), a non-invasive physical treatment, has been proposed to improve thrombocytopenia; however, its underlying regulatory mechanism is not fully understood.

OBJECTIVE

To further investigate the mechanism of thrombopoietin (TPO) in megakaryocytopoiesis and thrombopoiesis.

METHODS

Multiple approaches such as western blotting, cell transfection, flow cytometry, and animal studies were utilized to explore the effect and mechanism of PBMT on thrombopoiesis.

RESULTS

PBMT prevented a severe drop in platelet count by increasing platelet production, and then ameliorated CIT. Mechanistically, PBMT significantly upregulated hepatic TPO expression in a thrombocytopenic mouse model, which promoted megakaryocytopoiesis and thrombopoiesis. The levels of TPO mRNA and protein increased by PBMT via the Src/ERK/STAT3 signaling pathway in hepatic cells. Furthermore, the generation of the reactive oxygen species was responsible for PBMT-induced activation of Src and its downstream target effects.

CONCLUSIONS

Our research suggests that PBMT is a promising therapeutic strategy for the treatment of CIT.

Effects of Photobiomodulation/Laser Therapy Combined With Resistance Training on Quadriceps Hypertrophy and Strength, and Postural Balance in Older Women: A Randomized, Triple-Blinded, Placebo-Controlled Study

BACKGROUND AND PURPOSE

Physical and therapeutic strategies to maintain and rehabilitate skeletal muscle mass, strength, and postural balance are clinically relevant to improve the health, well-being, and quality of life of older adults. The purpose of this study was to investigate the effects of photobiomodulation (PBM)/laser therapy combined with a resistance training (RT) program on quadriceps hypertrophy and strength, and postural balance in older women.

METHODS

In a randomized, triple-blinded, placebo-controlled design, twenty-two older women (age 66.6 ± 5.2 years) were engaged in a supervised 10-wk RT program (2 times per week) involving unilateral leg extension exercise, in which each leg of the same participant was randomly assigned to receive active (λ = 808 nm, optical output = 100 mW, total energy = 42 J) or placebo laser PBM immediately before the RT sessions. Maximal dynamic strength by unilateral knee extension 1-repetition maximum (1RM), muscle hypertrophy by vastus lateralis muscle thickness, and postural balance by one-legged stance test on a force platform were assessed before and after the training program.

RESULTS

Significance statistical analysis revealed a similar improvement (time P = .003) from pre- to posttraining for muscle hypertrophy and strength, and postural balance between active and placebo laser conditions. However, clinical interpretation for muscle hypertrophy showed a moderate effect (effect size [ES] = 0.58) for the active laser and a small effect (ES = 0.38) for the placebo laser. Clinical difference was not noticed between conditions for other analyzed variables.

CONCLUSIONS

These findings indicate that RT alone can be clinically important for counteracting the deleterious effects of aging on muscle size, strength, and balance, and that applying laser PBM therapy before the RT sessions may further improve gains in muscle hypertrophy.

Exploring the ability of low-level laser irradiation to reduce myonecrosis and increase Myogenin transcription after Bothrops jararacussu envenomation

Envenoming caused by snakebites is a very important neglected tropical disease worldwide. The myotoxic phospholipases present in the bothropic venom disrupt the sarcolemma and compromise the mechanisms of energy production, leading to myonecrosis. Photobiomodulation therapy (PBMT) has been used as an effective tool to treat diverse cases of injuries, such as snake venom-induced myonecrosis. Based on that, the aim of this study was to analyze the effects of PBMT through low-level laser irradiation (904 nm) on the muscle regeneration after the myonecrosis induced by Bothrops jararacussu snake venom (Bjssu) injection, focusing on myogenic regulatory factors expression, such as Pax7, MyoD, and Myogenin (MyoG). Male Swiss mice (Mus musculus), 6-8-week-old, weighing 22 ± 3 g were used. Single sub-lethal Bjssu dose or saline was injected into the right mice gastrocnemius muscle. At 3, 24, 48, and 72 h after injections, mice were submitted to PBMT treatment. When finished the periods of 48 and 72 h, mice were euthanized and the right gastrocnemius were collected for analyses. We observed extensive inflammatory infiltrate in all the groups submitted to Bjssu injections. PBMT was able to reduce the myonecrotic area at 48 and 72 h after envenomation. There was a significant increase of MyoG mRNA expression at 72 h after venom injection. The data suggest that beyond the protective effect promoted by PBMT against Bjssu-induced myonecrosis, the low-level laser irradiation was able to stimulate the satellite cells, thus enhancing the muscle repair by improving myogenic differentiation.

Effect of Photobiomodulation on Restoration of Ionization Radiation-Induced Thyroid Dysfunction Through p53 and Retinoblastoma Signaling

Objective: This study aimed to investigate whether photobiomodulation (PBM) restores normal thyroid follicular cells affected by ionizing radiation, and to determine the mechanism of PBM on thyroid function. Background: Despite diverse applications of PBM to medical therapy, there has been no evidence of its involvement with thyroid function. Methods: A light emission diode (850 nm) array was used at 2, 5, and 10 J/cm² for in vitro analysis in human thyroid N-Thy-3.1 cells, and at 120 J/cm² for in vivo analysis in C58BL6 mice. Cell survival and proliferation were evaluated through clonogenic and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide] assays. Cell cycle was measured using flow cytometry. Cell cycle markers, such as p53, retinoblastoma (Rb), and E2F1, were investigated by western blot analysis. In vitro levels of cyclic adenosine monophosphate (cAMP) and thyroglobulin (TG) and in vivo levels of cAMP, TG, thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) were measured using enzyme-linked immunosorbent assay. Results: A lethal dose for N-Thy-3.1 cells was 6 Gy. PBM at 2 J/cm² was the most effective for causing cell cycle arrest by ionizing radiation. PBM regulated p53, Rb, and cAMP expression levels in vitro. PBM restored proliferation by regulating Rb and p53 in ionizing radiated thyroid follicular tissues. PBM also recovered cAMP, TG, and thyroid function marker expression (TSH, T3, and T4) by ionizing radiation in vivo. Conclusions: PBM restored ionizing radiation-induced thyroid follicular cell dysfunction by increasing cAMP proliferation and expression. PBM is effective for ionizing radiation-induced hypothyroidism by complementing cell proliferation and cAMP, presenting a novel method for clinical application.

A transient protective effect of low-level laser irradiation against disuse-induced atrophy of rats

Satellite cells, a population of skeletal muscular stem cells, are generally recognized as the main and, possibly, the sole source of postnatal muscle regeneration. Previous studies have revealed the potential of low-level laser (LLL) irradiation in promoting satellite cell proliferation, which, thereby, boosts the recovery of skeletal muscle from atrophy. The purpose of this study is to investigate the beneficial effect of LLL on disuse-induced atrophy. The optimal irradiation condition of LLL (808 nm) enhancing the proliferation of Pax7^+ve cells, isolated from tibialis anterior (TA) muscle, was examined and applied on TA muscle of disuse-induced atrophy model of the rats accordingly. Healthy rats were used as the control. On one hand, transiently, LLL was able to postpone the progression of atrophy for 1 week through a reduction of apoptosis in Pax7^-veMyoD^+ve (myocyte) population. Simultaneously, a significant enhancement was observed in Pax7^+veMyoD^+ve population; however, most of the increased cells underwent apoptosis since the second week, which suggested an impaired maturation of the population. On the other hand, in normal control rats with LLL irradiation, a significant increase in Pax7^+veMyoD^+ve cells and a significant decrease of apoptosis were observed. As a result, a strengthened muscle contraction was observed. Our data showed the capability of LLL in postponing the progression of disuse-induced atrophy for the first time. Furthermore, the result of normal rats with LLL irradiation showed the effectiveness of LLL to strengthen muscle contraction in healthy control.

Photobiomodulation by Led Does Not Alter Muscle Recovery Indicators and Presents Similar Outcomes to Cold-Water Immersion and Active Recovery

Purpose: The aim of the present study was to investigate the effectiveness of photobiomodulation therapy (PBMT) on muscle recovery based on inflammation (interleukin-10 [IL-10]; tumor necrosis factor-α [TNFα]), muscle damage markers (creatine kinase [CK]; lactate dehydrogenase [LDH]), delay onset muscle soreness (DOMS), and countermovement jump performance (CMJ) after two sprint interval training (SIT) sessions compared with a placebo condition (part-I), as well as to compare the effectiveness of PBMT with active recovery (AR) and cold-water immersion (CWI) (part-II). Methods: Part-I was conducted as a double-blind, randomized and placebo-controlled study and part-II as a parallel-group study. Thirty-six men participated in the studies (12 participants in part-I and 36 participants in part-II). Volunteers performed two SITs interspaced by 24-h (SIT₁ and SIT₂) to mimic the effect of accumulating 2 consecutive days of SIT. In part-I, only after SIT₂, PBMT [Total energy: 600J (300J per leg in 5 spots); wavelength: 660-850 nm] or placebo interventions were performed, while in part-II PBMT (part-I data), AR (15-min; 50% of the maximal aerobic power), or CWI (10-min; 10°C) were carried out, also after SIT₂. Blood samples were collected before (i.e., baseline), and 0.5, 1, 24, 48, and 72-h after SIT₂, while CMJ and DOMS were measured before, 24, 48, and 72-h after SIT₂. Results: In part-I, there were no interactions between PBMT and placebo conditions for any blood markers (P ≥ 0.313), DOMS (P = 0.052), and CMJ (P = 0.295). However, an effect of time was found with increases in LDH, CK, and IL-10 (P ≤ 0.043) as well as a decrease in DOMS at 72-h compared with 24-h (P = 0.012). In part-II, there were no interactions between the PBMT, AR, and CWI groups for any markers at the same moments (P ≥ 0.189) and for the peak and integral values (P ≥ 0.193), for DOMS (P = 0.314) and CMJ (P = 0.264). However, an effect of time was found with an increase in CK and IL-10 (P = 0.003), while DOMS decreased at 48 and 72-h compared with 24-h (P = 0.001). Conclusion: In summary, PBMT had no effect on inflammation, muscle damage, CMJ performance, or DOMS after two consecutive sprint interval training sessions compared to placebo, CWI, and AR strategies.

Low-level laser irradiation induces a transcriptional myotube-like profile in C2C12 myoblasts

Low-level laser irradiation (LLLI) has been used as a non-invasive method to improve muscular regeneration capability. However, the molecular mechanisms by which LLLI exerts these effects remain largely unknown. Here, we described global gene expression profiling analysis in C2C12 myoblasts after LLLI that identified 514 differentially expressed genes (DEG). Gene ontology and pathway analysis of the DEG revealed transcripts among categories related to cell cycle, ribosome biogenesis, response to stress, cell migration, and cell proliferation. We further intersected the DEG in C2C12 myoblasts after LLLI with publicly available transcriptomes data from myogenic differentiation studies (myoblasts vs myotube) to identify transcripts with potential effects on myogenesis. This analysis revealed 42 DEG between myoblasts and myotube that intersect with altered genes in myoblasts after LLLI. Next, we performed a hierarchical cluster analysis with this set of shared transcripts that showed that LLLI myoblasts have a myotube-like profile, clustering away from the myoblast profile. The myotube-like transcriptional profile of LLLI myoblasts was further confirmed globally considering all the transcripts detected in C2C12 myoblasts after LLLI, by bi-dimensional clustering with myotubes transcriptional profiles, and by the comparison with 154 gene sets derived from previous published in vitro omics data. In conclusion, we demonstrate for the first time that LLLI regulates a set of mRNAs that control myoblast proliferation and differentiation into myotubes. Importantly, this set of mRNAs revealed a myotube-like transcriptional profile in LLLI myoblasts and provide new insights to the understanding of the molecular mechanisms underlying the effects of LLLI on skeletal muscle cells.

Combination Therapy Versus Exercise and Orthotic Support in the Management of Pain in Plantar Fasciitis: A Randomized Controlled Trial

BACKGROUND

This study aimed at estimating the effectiveness of two commonly used modalities-extracorporeal shock wave therapy (ESWT) and low-level laser therapy (LLLT)-each combined with usual care (exercises and orthotic supports) in comparison to only usual care to relieve pain in patients with plantar fasciitis (PF).

METHODS

Participants with PF were randomly allocated into 3 groups: ESWT (n = 25), LLLT (n = 24), and control (n = 17). All participants received a home exercise program with orthotic support. The ESWT group received 2000 shock waves with 0.02 mJ/mm² for 3 sessions, once a week; LLLT group received gallium-aluminum-arsenide laser with 850 nm wavelength for 10 sessions, 3 times a week. Pain was measured by Foot Function Index-pain subscale (FFI-p) and Numerical Rating Scale for pain (NRS-p). The scores were recorded at baseline, third week, and third month after the treatment. Analysis was performed using repeated measures ANOVA.

RESULTS

There was a significant improvement in pain over the 3 months in all groups on both FFI-p ( P < .001) and NRS-p ( P < .001). In NRS-p, LLLT group had significantly lower pain than ESWT ( P = .002) at the third week and control ( P = .043) and ESWT ( P = .003) at third month. In FFI-p total score, ESWT group had higher pain than LLLT ( P = .003) and control ( P = .035) groups at third week and LLLT ( P = .010) group at third month.

CONCLUSION

When LLLT and ESWT were combined with usual care, LLLT was found to be more effective than ESWT in reducing pain in PF at short-term follow-up.

LEVEL OF EVIDENCE

Level II, comparative study.

Brain Photobiomodulation Therapy: a Narrative Review

Brain photobiomodulation (PBM) therapy using red to near-infrared (NIR) light is an innovative treatment for a wide range of neurological and psychological conditions. Red/NIR light is able to stimulate complex IV of the mitochondrial respiratory chain (cytochrome c oxidase) and increase ATP synthesis. Moreover, light absorption by ion channels results in release of Ca²⁺ and leads to activation of transcription factors and gene expression. Brain PBM therapy enhances the metabolic capacity of neurons and stimulates anti-inflammatory, anti-apoptotic, and antioxidant responses, as well as neurogenesis and synaptogenesis. Its therapeutic role in disorders such as dementia and Parkinson's disease, as well as to treat stroke, brain trauma, and depression has gained increasing interest. In the transcranial PBM approach, delivering a sufficient dose to achieve optimal stimulation is challenging due to exponential attenuation of light penetration in tissue. Alternative approaches such as intracranial and intranasal light delivery methods have been suggested to overcome this limitation. This article reviews the state-of-the-art preclinical and clinical evidence regarding the efficacy of brain PBM therapy.

Pulse frequency dependency of photobiomodulation on the bioenergetic functions of human dental pulp stem cells

Photobiomodulation (PBM) therapy contributes to pain relief, wound healing, and tissue regeneration. The pulsed wave (PW) mode has been reported to be more effective than the continuous wave (CW) mode when applying PBM to many biological systems. However, the reason for the higher effectiveness of PW-PBM is poorly understood. Herein, we suggest using delayed luminescence (DL) as a reporter of mitochondrial activity after PBM treatment. DL originates mainly from mitochondrial electron transport chain systems, which produce reactive oxygen species (ROS) and adenosine triphosphate (ATP). The decay time of DL depends on the pulse frequencies of applied light, which correlate with the biological responses of human dental pulp stem cells (hDPSCs). Using a low-power light whose wavelength is 810 nm and energy density is 38 mJ/cm², we find that a 300-Hz pulse frequency prolonged the DL pattern and enhanced alkaline phosphatase activity. In addition, we analyze mitochondrial morphological changes and their volume density and find evidence supporting mitochondrial physiological changes from PBM treatment. Our data suggest a new methodology for determining the effectiveness of PBM and the specific pulse frequency dependency of PBM in the differentiation of hDPSCs.

Histomorphologic and ultrastructural recovery of myopathy in rats treated with low-level laser therapy

The purpose of the present work was to study the effect of low-level laser therapy (LLLT): helium-neon (He-Ne) and gallium arsenide (Ga-As) laser on the histomorphology of muscle and mitochondria in experimental myopathy in rats. Thirty Suquía strain female rats were distributed in groups: (A) control (intact), (B) injured, (C) injured and treated with He-Ne laser, (D) injured and treated with Ga-As laser, (E) irradiated with He-Ne laser on the non-injured muscle, and (F) irradiated with Ga-As laser on the non-injured muscle. Myopathy was induced by injecting 0.05 mg/rat/day of adrenaline in the left gastrocnemius muscle at the same point on five consecutive days, in groups B, C, and D. LLLT was applied with 9.5 J cm^-2 daily for seven consecutive days in groups C, D, E, and F. The muscles were examined with optic and electronic microscopy. The inflammation was classified as absent, mild, and intense and the degree of mitochondrial alteration was graded I, II, III, and IV. Categorical data were statistically analyzed by Chi-square and the Fisher-Irwin Bilateral test, setting significant difference at p < 0.05. The damage found in muscle and mitochondria histomorphology in animals with induced myopathy (B) was intense or severe inflammation with grade III or IV of mitochondrial alteration. They underwent significant regression (p < 0.001) compared with the groups treated with He-Ne (C) and Ga-As (D) laser, in which mild or moderate inflammation was seen and mitochondrial alteration grades I and II, recovering normal myofibrillar architecture. No differences were found between the effects caused by the two lasers, or between groups A, E, and F. Group A was found to be different from B, C, and D (p < 0.001). LLLT in experimental myopathy caused significant muscular and mitochondrial morphologic recovery.

Rehabilitation of hamstring muscle injuries: a literature review

Hamstring injuries are among the most frequent in sports. The high relapse rate is a challenge for sports medicine and has a great impact on athletes and sport teams. The treatment goal is to provide the athlete the same functional level as before the injury. Thus, functional rehabilitation is very important to the success of the treatment. Currently, several physical therapy modalities are used, according to the stage of the lesion, such as cryotherapy, laser therapy, therapeutic ultrasound, therapeutic exercise, and manual therapy. However, the evidence of the effectiveness of these modalities in muscle injuries is not fully established due to the little scientific research on the topic. This article presents an overview of the physiotherapy approach in the rehabilitation of hamstring muscle injuries.

Analysis of Radiomodulatory Effect of Low-Level Laser Irradiation by Clonogenic Survival Assay

OBJECTIVE

The aim of this study was to investigate the radiomoulatory effects of low-level laser irradiation (LLLI) in normal and cancer cells exposed to ionizing X-ray radiation on clonogenic survival assay.

BACKGROUND DATA

LLLI does have radioprotective effects on normal tissue. LLLI can reduce the incidence of mucocutaneous complications of ionizing radiation. Few in vitro studies reported adaptive responses for LLLI to ionizing radiation in normal and cancer cells, particularly with respect to clonogenic cell survival assay.

METHODS

Normal NIH 3T3 cells and cancer HeLa cells were irradiated with 685 and 830 nm LLLI at different energy densities prior to ionizing X-ray radiation. The survival fraction was determined after ionizing radiation (0, 2, 4, and 6 Gy). The values of the linear (α) and quadratic (β) parameters were calculated based on the clonogenic survival curves.

RESULTS

Clonogenic radiation survival assay showed that the application of LLLI at 685 nm prior to ionizing radiation could significantly inhibit clonogenic growth of HeLa cells compared with unirradiated HeLa cells. LLLI could also significantly increase the α parameter of the linear quadratic (LQ) model. In contrast, application of LLLI at 830 nm could significantly protect NIH 3T3 cells against radiation and decreased α parameter.

CONCLUSIONS

This study suggests that various physical parameters of LLLI can be diverse adaptive responses to ionizing radiation on normal and cancer cells.

Isolation, Culture, and Immunostaining of Skeletal Muscle Myofibers from Wildtype and Nestin-GFP Mice as a Means to Analyze Satellite Cell

Multinucleated myofibers, the functional contractile units of adult skeletal muscle, harbor mononuclear Pax7+ myogenic progenitors on their surface between the myofiber basal lamina and plasmalemma. These progenitors, known as satellite cells, are the primary myogenic stem cells in adult muscle. This chapter describes our laboratory protocols for isolating, culturing, and immunostaining intact myofibers from mouse skeletal muscle as a means for studying satellite cell dynamics. The first protocol discusses myofiber isolation from the flexor digitorum brevis (FDB) muscle. These short myofibers are plated in dishes coated with PureCol collagen (formerly known as Vitrogen) and maintained in a mitogen-poor medium (± supplemental growth factors). Employing such conditions, satellite cells remain at the surface of the parent myofiber while synchronously undergoing a limited number of proliferative cycles and rapidly differentiate. The second protocol discusses the isolation of longer myofibers from the extensor digitorum longus (EDL) muscle. These EDL myofibers are routinely plated individually as adherent myofibers in wells coated with Matrigel and maintained in a mitogen-rich medium, conditions in which satellite cells migrate away from the parent myofiber, proliferate extensively, and generate numerous differentiating progeny. Alternatively, these EDL myofibers can be plated as non-adherent myofibers in uncoated wells and maintained in a mitogen-poor medium (± supplemental growth factors), conditions that retain satellite cell progeny at the myofiber niche similar to the FDB myofiber cultures. However, the adherent myofiber format is our preferred choice for monitoring satellite cells in freshly isolated (Time 0) myofibers. We conclude this chapter by promoting the Nestin-GFP transgenic mouse as an efficient tool for direct analysis of satellite cells in isolated myofibers. While satellite cells have been often detected by their expression of the Pax7 protein or the Myf5nLacZ knockin reporter (approaches that are also detailed herein), the Nestin-GFP reporter distinctively permits quantification of satellite cells in live myofibers, which enables linking initial Time 0 numbers and subsequent performance upon culturing. We additionally point out to the implementation of the Nestin-GFP transgene for monitoring other selective cell lineages as illustrated by GFP expression in capillaries, endothelial tubes and neuronal cells. Myofibers from other types of muscles, such as diaphragm, masseter, and extraocular, can also be isolated and analyzed using protocols described herein. Collectively, this chapter provides essential tools for studying satellite cells in their native position and their interplay with the parent myofiber.

Low-Level Laser Therapy (904 nm) Counteracts Motor Deficit of Mice Hind Limb following Skeletal Muscle Injury Caused by Snakebite-Mimicking Intramuscular Venom Injection

Myotoxins present in Bothrops venom disrupt the sarcolemma of muscle fibers leading to the release of sarcoplasmic proteins and loss of muscle homeostasis. Myonecrosis and tissue anoxia induced by vascularization impairment can lead to amputation or motor functional deficit. The objective of this study was to investigate the dynamic behavior of motor function in mice subjected to injection of Bothrops jararacussu venom (Bjssu) and exposed to low-level laser therapy (LLLT). Male Swiss mice received Bjssu injection (830 μg/kg) into the medial portion of the right gastrocnemius muscle. Three hours later the injected region was irradiated with diode semiconductor Gallium Arsenide (GaAs- 904 nm, 4 J/cm²) laser following by irradiation at 24, 48 and 72 hours. Saline injection (0.9% NaCl) was used as control. Gait analysis was performed 24 hours before Bjssu injection and at every period post-Bjssu using CatWalk method. Data from spatiotemporal parameters Stand, Maximum Intensity, Swing, Swing Speed, Stride Length and Step Cycle were considered. The period of 3 hours post venom-induced injury was considered critical for all parameters evaluated in the right hindlimb. Differences (p<0.05) were concentrated in venom and venom + placebo laser groups during the 3 hours post-injury period, in which the values of stand of most animals were null. After this period, the gait characteristics were re-established for all parameters. The venom + laser group kept the values at 3 hours post-Bjssu equal to that at 24 hours before Bjssu injection indicating that the GaAs laser therapy improved spatially and temporally gait parameters at the critical injury period caused by Bjssu. This is the first study to analyze with cutting edge technology the gait functional deficits caused by snake envenoming and gait gains produced by GaAs laser irradiation. In this sense, the study fills a gap on the field of motor function after laser treatment following snake envenoming.

Low-level infrared laser modulates muscle repair and chromosome stabilization genes in myoblasts

Infrared laser therapy is used for skeletal muscle repair based on its biostimulative effect on satellite cells. However, shortening of telomere length limits regenerative potential in satellite cells, which occurs after each cell division cycle. Also, laser therapy could be more effective on non-physiologic tissues. This study evaluated low-level infrared laser exposure effects on mRNA expression from muscle injury repair and telomere stabilization genes in myoblasts in normal and stressful conditions. Laser fluences were those used in clinical protocols. C2C12 myoblast cultures were exposed to low-level infrared laser (10, 35, and 70 J/cm(2)) in standard or normal (10 %) and reduced (2 %) fetal bovine serum concentrations; total RNA was extracted for mRNA expression evaluation from muscle injury repair (MyoD and Pax7) and chromosome stabilization (TRF1 and TRF2) genes by real time quantitative polymerization chain reaction. Data show that low-level infrared laser increases the expression of MyoD and Pax7 in 10 J/cm(2) fluence, TRF1 expression in all fluences, and TRF2 expression in 70 J/cm(2) fluence in both 10 and 2 % fetal bovine serum. Low-level infrared laser increases mRNA expression from genes related to muscle repair and telomere stabilization in myoblasts in standard or normal and stressful conditions.

Effects of Low-Level Laser Therapy Applied Before Treadmill Training on Recovery of Injured Skeletal Muscle in Wistar Rats

OBJECTIVE

The aim of this study was to analyze the effects of low-level laser therapy (LLLT) when associated with treadmill training on the recovery of skeletal muscle, during two periods of rest after muscle injury in rats.

BACKGROUND DATA

Because of photostimulation, LLLT has been presented as an alternative for accelerating the tissue healing process.

MATERIALS AND METHODS

Forty rats were divided into two groups (A and B) containing four subgroups each: GC (Control Group)-cryolesion untreated; EG (Exercise Group)-cryolesion treated with physical exercise; LG (Laser Group)-cryolesion treated with laser; ELG (Exercise and Laser Group)-cryolesion treated with laser and physical exercise. The right tibialis anterior (TA) of the middle belly was injured by a cooling iron bar (cryoinjury). Group A remained at rest for 3 days, whereas Group B remained at rest for 7 days. The laser parameters utilized were 780 nm with 15 mW average optical power and spot size of 0.04 cm(2) applied during 10 sec, leading to 0.152 J and 3.8 J/cm(2). Treadmill training with and without laser application was performed during 5 days, with each session lasting for 12 min at a velocity of 17 m/min. Subsequently, the TA muscle was removed for a histological and morphometric analysis.

RESULTS

The damaged area was significantly smaller for the ELG at both periods of rest, 3 and 7 days, respectively (4.4 ± 0.42% and 3.5 ± 0.14%, p < 0.05), when compared with the LG (18.6 ± 0.64% and 7.5 ± 0.13%), the EG (21 ± 0.26% and 8.7 ± 0.32%), and the CG (23.9 ± 0.37% and 21.4 ± 0.38%). In addition, the number of blood vessels were significantly higher for the ELG at both periods of rest, 3 and 7 days, respectively (71.2 ± 13.51 and 104.5 ± 11.78, p < 0.05), when compared with the LG (60.6 ± 11.25 and 93.5 ± 16.87), the EG (51.6 ± 7.3 and 93.8 ± 15.1) and the CG (34.4 ± 2.54 and 65.7 ± 14.1).

CONCLUSIONS

The LLLT applied before the physical exercise on the treadmill stimulated the angiogenesis and accelerated the process of muscle recovery.

Cell viability, reactive oxygen species, apoptosis, and necrosis in myoblast cultures exposed to low-level infrared laser

Low-level infrared laser is considered safe and effective for treatment of muscle injuries. However, the mechanism involved on beneficial effects of laser therapy are not understood. The aim was to evaluate cell viability, reactive oxygen species, apoptosis, and necrosis in myoblast cultures exposed to low-level infrared laser at therapeutic fluences. C2C12 myoblast cultures at different (2 and 10 %) fetal bovine serum (FBS) concentrations were exposed to low-level infrared laser (808 nm, 100 mW) at different fluences (10, 35, and 70 J/cm(2)) and evaluated after 24, 48, and 72 h. Cell viability was evaluated by WST-1 assay; reactive oxygen species (ROS), apoptosis, and necrosis were evaluated by flow cytometry. Cell viability was decreased atthe lowest FBS concentration. Laser exposure increased the cell viability in myoblast cultures at 2 % FBS after 48 and 72 h, but no significant increase in ROS was observed. Apoptosis was decreased at the higher fluence and necrosis was increased at lower fluence in myoblast cultures after 24 h of laser exposure at 2 % FBS. No laser-induced alterations were obtained at 10 % FBS. Results show that level of reactive oxygen species is not altered, at least to those evaluated in this study, but low-level infrared laser exposure affects cell viability, apoptosis, and necrosis in myoblast cultures depending on laser fluence and physiologic conditions of cells.

Effect of 830-nm laser phototherapy on olfactory neuronal ensheathing cells grown in vitro on novel bioscaffolds

BACKGROUND

The purpose of this study was to analyze olfactory ensheathing cell (OEC) proliferation and growth on Biosilicate and collagen bioscaffolds, and to determine whether the application of laser phototherapy would result in increased OEC proliferation on the scaffolds. The use of bioscaffolds is considered a promising strategy in a number of clinical applications where tissue healing is suboptimal. As in vitro OEC growth is a slow process, laser phototherapy could be useful to stimulate proliferation on bioscaffolds.

METHODS

OEC cells were seeded on the Biosilicate and collagen scaffolds. Seeded scaffolds were irradiated with a single exposure of 830-nm laser. Nonirradiated seeded scaffolds acted as negative controls. Cell proliferation was assessed 7 days after irradiation.

RESULTS

OECs were successfully grown on discs composed of a glass-ceramic and collagen composite. Laser irradiation produced a 32.7% decrease and a 13.2% increase in OEC proliferation on glass-ceramic discs and on collagen scaffolds, respectively, compared with controls. Laser phototherapy resulted in a reduction in cell growth on the Biosilicate scaffolds and an increase in cell proliferation on collagen scaffolds.

CONCLUSIONS

These results were probably due to the nature of the materials. Future research combining laser phototherapy and glass-ceramic scaffolds should take into account possible interactions of the laser with matrix compounds.

Halofuginone promotes satellite cell activation and survival in muscular dystrophies

Halofuginone is a leading agent in preventing fibrosis and inflammation in various muscular dystrophies. We hypothesized that in addition to these actions, halofuginone directly promotes the cell-cycle events of satellite cells in the mdx and dysf(-/-) mouse models of early-onset Duchenne muscular dystrophy and late-onset dysferlinopathy, respectively. In both models, addition of halofuginone to freshly prepared single gastrocnemius myofibers derived from 6-week-old mice increased BrdU incorporation at as early as 18h of incubation, as well as phospho-histone H3 (PHH3) and MyoD protein expression in the attached satellite cells, while having no apparent effect on myofibers derived from wild-type mice. BrdU incorporation was abolished by an inhibitor of mitogen-activated protein kinase/extracellular signal-regulated protein kinase, suggesting involvement of this pathway in mediating halofuginone's effects on cell-cycle events. In cultures of myofibers and myoblasts isolated from dysf(-/-) mice, halofuginone reduced Bax and induced Bcl2 expression levels and induced Akt phosphorylation in a time-dependent manner. Addition of an inhibitor of the phosphinositide-3-kinase/Akt pathway reversed the halofuginone-induced cell survival, suggesting this pathway's involvement in mediating halofuginone's effects on survival. Thus, in addition to its known role in inhibiting fibrosis and inflammation, halofuginone plays a direct role in satellite cell activity and survival in muscular dystrophies, regardless of the mutation. These actions are of the utmost importance for improving muscle pathology and function in muscular dystrophies.

Near infrared radiation protects against oxygen-glucose deprivation-induced neurotoxicity by down-regulating neuronal nitric oxide synthase (nNOS) activity in vitro

Near infrared radiation (NIR) has been shown to be neuroprotective against neurological diseases including stroke and brain trauma, but the underlying mechanisms remain poorly understood. In the current study we aimed to investigate the hypothesis that NIR may protect neurons by attenuating oxygen-glucose deprivation (OGD)-induced nitric oxide (NO) production and modulating cell survival/death signaling. Primary mouse cortical neurons were subjected to 4 h OGD and NIR was applied at 2 h reoxygenation. OGD significantly increased NO level in primary neurons compared to normal control, which was significantly ameliorated by NIR at 5 and 30 min post-NIR. Neither OGD nor NIR significantly changed neuronal nitric oxide synthase (nNOS) mRNA or total protein levels compared to control groups. However, OGD significantly increased nNOS activity compared to normal control, and this effect was significantly diminished by NIR. Moreover, NIR significantly ameliorated the neuronal death induced by S-Nitroso-N-acetyl-DL-penicillamine (SNAP), a NO donor. Finally, NIR significantly rescued OGD-induced suppression of p-Akt and Bcl-2 expression, and attenuated OGD-induced upregulation of Bax, BAD and caspase-3 activation. These results suggest NIR may protect against OGD at least partially through reducing NO production by down-regulating nNOS activity, and modulating cell survival/death signaling.

[The application of stem cells, visible and infrared light in regenerative medicine. Part 1]

OBJECTIVE

The present article was designed to overview the experimental studies of visible and infrared light irradiation of human and animal stem cells (SC) in vitro and in vivo for the evaluation of its photobiomodulatory effects. The results will be used to elaborate substantiation for the choice of the parameters of SC light irradiation and to develop recommendations for the application of this method in regenerative medicine (RM).

BACKGROUND

The clinical application of light irradiation is a matter of contrsy, in the first place due to the difficulties encountered in the rational choice of irradiation parameters. The theoretical substantiation of such choice remains a stumbling block too despite the long history of photoghromotherapy. There is thus far no reliable theoretical basis for the adequate choice of such irradiation parameters as power density, radiation dose, and exposure time. The experiences with the light application for the purpose of regenerative medicine have never been summarized.

RESULTS

The present review encompasses 78 articles selected for the basic analysis that report the studies with the use of a variety of SC types. The analysis has demonstrated that clinical investigations into the influence of light on the stem cells are still in their infancy. It was shown that the irradiation parameters need to be chosen taking into consideration the type of the stem cells. Different authors report the achievement of the maximum SC proliferation and differentiation rates at energy densities as high as 50 mW/sq.cm, small radiation doses (around 1 J/sq.cm) and exposure time (on the order of seconds).

CONCLUSION

The general conclusion for Parts 1 and II of this communication will be presented in the next issue of this journal (number 2, 2015).

Low-Level Laser Therapy at 635 nm for Treatment of Chronic Plantar Fasciitis: A Placebo-Controlled, Randomized Study

Plantar fasciitis affects nearly 1 million persons in the United States at any one time. Conservative therapies have been reported to successfully treat 90% of plantar fasciitis cases; however, for the remaining cases, only invasive therapeutic solutions remain. This investigation studied newly emerging technology, low-level laser therapy. From September 2011 to June 2013, 69 subjects were enrolled in a placebo-controlled, randomized, double-blind, multicenter study that evaluated the clinical utility of low-level laser therapy for the treatment of unilateral chronic fasciitis. The volunteer participants were treated twice a week for 3 weeks for a total of 6 treatments and were evaluated at 5 separate time points: before the procedure and at weeks 1, 2, 3, 6, and 8. The pain rating was recorded using a visual analog scale, with 0 representing "no pain" and 100 representing "worst pain." Additionally, Doppler ultrasonography was performed on the plantar fascia to measure the fascial thickness before and after treatment. Study participants also completed the Foot Function Index. At the final follow-up visit, the group participants demonstrated a mean improvement in heel pain with a visual analog scale score of 29.6 ± 24.9 compared with the placebo subjects, who reported a mean improvement of 5.4 ± 16.0, a statistically significant difference (p < .001). Although additional studies are warranted, these data have demonstrated that low-level laser therapy is a promising treatment of plantar fasciitis.

Photomodulation of proliferation and differentiation of stem cells by the visible and infrared light

OBJECTIVE

The aim of this article is to review experimental studies of visible and infrared light irradiation of human and animal stem cells (SCs) in vitro and in vivo to assess photobiomodulation effects on their proliferation and differentiation.

BACKGROUND DATA

The clinical application of light irradiation remains controversial, primarily because of the complexity of the rational choice of irradiation parameters. In laboratories, the theoretical justification underlying the choice of irradiation parameters also remains a challenge.

METHODS

A systematic review was completed of original research articles that investigated the effects of light irradiation on human and animal SCs in vitro and in vivo (to June 2014). Relevant articles were sourced from PubMed and MEDLINE(®). The search terms were laser (light) therapy (irradiation), stem cells, and phototherapy, stem cells.

RESULTS

The analysis revealed the importance of cell type when choosing the cell irradiation parameters. The influence of wavelength on the SC proliferation rate seemed to be nonsignificant. The high values of increased proliferation or differentiation were obtained using high power density, low energy density, and short exposure time. SC exposure to light without inducers did not lead to their differentiation. The maximum differentiation was achieved using irradiation parameters different from the ones needed to achieve the maximum proliferation of the same cells.

CONCLUSIONS

Increased power density and reduced energy density were needed to increase the SC response. Based on the analysis, we have presented a graph of the cell response to generalized photostimulus, and introduced the concepts of "photostress" and "photoshock" to describe the stages of this response.

Pre-conditioning with low-level laser (light) therapy: light before the storm

Pre-conditioning by ischemia, hyperthermia, hypothermia, hyperbaric oxygen (and numerous other modalities) is a rapidly growing area of investigation that is used in pathological conditions where tissue damage may be expected. The damage caused by surgery, heart attack, or stroke can be mitigated by pre-treating the local or distant tissue with low levels of a stress-inducing stimulus, that can induce a protective response against subsequent major damage. Low-level laser (light) therapy (LLLT) has been used for nearly 50 years to enhance tissue healing and to relieve pain, inflammation and swelling. The photons are absorbed in cytochrome(c) oxidase (unit four in the mitochondrial respiratory chain), and this enzyme activation increases electron transport, respiration, oxygen consumption and ATP production. A complex signaling cascade is initiated leading to activation of transcription factors and up- and down-regulation of numerous genes. Recently it has become apparent that LLLT can also be effective if delivered to normal cells or tissue before the actual insult or trauma, in a pre-conditioning mode. Muscles are protected, nerves feel less pain, and LLLT can protect against a subsequent heart attack. These examples point the way to wider use of LLLT as a pre-conditioning modality to prevent pain and increase healing after surgical/medical procedures and possibly to increase athletic performance.

Low-level laser therapy ameliorates disease progression in a mouse model of Alzheimer's disease

Low-level laser therapy (LLLT) has been used to treat inflammation, tissue healing, and repair processes. We recently reported that LLLT to the bone marrow (BM) led to proliferation of mesenchymal stem cells (MSCs) and their homing in the ischemic heart suggesting its role in regenerative medicine. The aim of the present study was to investigate the ability of LLLT to stimulate MSCs of autologous BM in order to affect neurological behavior and β-amyloid burden in progressive stages of Alzheimer's disease (AD) mouse model. MSCs from wild-type mice stimulated with LLLT showed to increase their ability to maturate towards a monocyte lineage and to increase phagocytosis activity towards soluble amyloid beta (Aβ). Furthermore, weekly LLLT to BM of AD mice for 2 months, starting at 4 months of age (progressive stage of AD), improved cognitive capacity and spatial learning, as compared to sham-treated AD mice. Histology revealed a significant reduction in Aβ brain burden. Our results suggest the use of LLLT as a therapeutic application in progressive stages of AD and imply its role in mediating MSC therapy in brain amyloidogenic diseases.

Low level laser therapy on experimental myopathy

PURPOSE

The aim of the present work was to study the effect of Helium-Neon (HeNe) and Gallium Arsenide (GaAs) laser upon nitric oxide (NO) plasma levels, an inflammatory biomarker associated with oxidative stress, in rats with experimental myopathy. These were evaluated through histological assessment.

MATERIALS AND METHODS

The groups studied were: (A) control (intact rats that received LLLT sham exposures), (B) rats with myopathy and sacrificed at 24 h later, (C) rats with myopathy and sacrificed 8 days later, (D) rats with myopathy and treated with HeNe laser, (E) rats with myopathy and treated with GaAs laser, (F) intact rats treated with HeNe laser and (G) intact rats treated with GaAs laser. Myopathy was induced by injecting 50μl of 1% carrageenan λ (type IV) in the left gastrocnemius muscle. Low Level Laser Therapy (LLLT) was applied with 9.5 J.cm(-2) daily for 10 consecutive days with each laser. The determination of the NO was made by spectrophotometry. The muscles were stained with Hematoxylin-Eosin and examined by optic microscopy. Quantitative variables were statistically analyzed by the Fisher test, and categorical by applying Pearson's Chi Squared test at p <0.05 for all cases.

RESULTS

In groups B and C, NO was significantly increased compared to groups A, D, E, F and G (p<0.05). In group C, the percentage of area with inflammatory infiltration was significantly increased compared to the other groups (p<0.001).

CONCLUSIONS

LLLT decreased plasma levels of NO in rats with experimental myopathies and significant muscle recovery.

Low-level laser therapy (LLLT) reduces oxidative stress in primary cortical neurons in vitro

Low-level laser (light) therapy (LLLT) involves absorption of photons being in the mitochondria of cells leading to improvement in electron transport, increased mitochondrial membrane potential (MMP), and greater ATP production. Low levels of reactive oxygen species (ROS) are produced by LLLT in normal cells that are beneficial. We exposed primary cultured murine cortical neurons to oxidative stressors: hydrogen peroxide, cobalt chloride and rotenone in the presence or absence of LLLT (3 J/cm², CW, 810 nm wavelength laser, 20 mW/cm²). Cell viability was determined by Prestoblue™ assay. ROS in mitochondria was detected using Mito-sox, while ROS in cytoplasm was detected with CellRox™. MMP was measured with tetramethylrhodamine. In normal neurons LLLT elevated MMP and increased ROS. In oxidatively-stressed cells LLLT increased MMP but reduced high ROS levels and protected cultured cortical neurons from death. Although LLLT increases ROS in normal neurons, it reduces ROS in oxidatively-stressed neurons. In both cases MMP is increased. These data may explain how LLLT can reduce clinical oxidative stress in various lesions while increasing ROS in cells in vitro.

532 nm low-power laser irradiation recovers γ-secretase inhibitor-mediated cell growth suppression and promotes cell proliferation via Akt signaling

Background and Objective

The γ-secretase inhibitor (GSI) has been shown to inhibit expression of amyloid beta (Aβ), but GSI also has a side effect of reducing cell survival. Since low-power laser irradiation (LLI) has been known to promote cell survival, we examined whether 532 nm LLI can rescue the GSI side effect or not.

Study Design/Materials and Methods

The human-derived glioblastoma cells (A-172) were cultured in 35 mm culture dishes or 96-well plate. The center of dish or selected wells was irradiated with 532 nm laser (Nd:YVO4, CW, 60 mW) for 20, 40 and 60 min, respectively. The irradiated cells were photographed at immediately after, 24 and 48 h later and counted. GSI was supplemented in medium 3 h before LLI. The MTT assay was also used to estimate viable cells at 48 h after irradiation. The expression of phosphorylated Akt (p-Akt) or phosphorylated PTEN (p-PTEN) was examined by immunofluorescent staining and measured by fluorescence intensity using the software (BZ-9000, KEYENCE, Japan).

Results

GSI application depressed cell proliferation as well as cell survival compared to control. GSI down-regulated Aβ but up-regulated p-PTEN and suppressed p-Akt. Application of 532 nm LLI in the presence of GSI significantly recovered the GSI-mediated effects, i.e., LLI could decrease elevated p-PTEN, while increased p-Akt expression with keeping Aβ suppression. The LLI effects had a dose-dependency.

Conclusion

We confirmed that GSI potently suppressed intracellular Aβ and decreased cell survival. We conclude that a combination of GSI application and 532 nm LLI can increase cell proliferation via Akt activation while keeping PTEN and Aβ suppressed.