Low-level laser therapy for wound healing: feasibility of wound dressing transillumination

External Basic Hyperthermia Devices for Preclinical Studies in Small Animals

Simple Summary

The application of mild hyperthermia can be beneficial for solid tumor treatment by induction of sublethal effects on a tissue- and cellular level. When designing a hyperthermia experiment, several factors should be taken into consideration. In this review, multiple elementary hyperthermia devices are described in detail to aid standardization of treatment design.

Abstract

Preclinical studies have shown that application of mild hyperthermia (40–43 °C) is a promising adjuvant to solid tumor treatment. To improve preclinical testing, enhance reproducibility, and allow comparison of the obtained results, it is crucial to have standardization of the available methods. Reproducibility of methods in and between research groups on the same techniques is crucial to have a better prediction of the clinical outcome and to improve new treatment strategies (for instance with heat-sensitive nanoparticles). Here we provide a preclinically oriented review on the use and applicability of basic hyperthermia systems available for solid tumor thermal treatment in small animals. The complexity of these techniques ranges from a simple, low-cost water bath approach, irradiation with light or lasers, to advanced ultrasound and capacitive heating devices.

Effects of pulsing of light on the dentinogenesis of dental pulp stem cells in vitro

Low power light (LPL) treatment has been widely used in various clinical trials, which has been known to reduce pain and inflammation and to promote wound healing. LPL was also shown to enhance differentiation of stem cells into specific lineages. However, most studies have used high power light in mW order, and there was lack of studies about the effects of very low power light in μW. In this study, we applied 810 nm LPL of 128 μW/cm² energy density in vitro. Upon this value, continuous wave (CW) irradiation did not induce any significant changes for differentiation of human dental pulp stem cells (hDPSCs). However, the membrane hyperpolarization, alkaline phosphatase activity, and intracellular oxidative stress were largely enhanced in the pulsed wave (PW) with 30% of duty cycle and 300–3000 Hz frequencies-LPL in which LED driver work in the form of square wave. After 21 days of daily LPL treatment, Western blot revealed the dentinogenesis in this condition in vitro. This study demonstrates that the very low power light at 810 nm enhanced significant differentiation of hDPSCs in the PW mode and there were duty cycle dependency as well as pulsing frequency dependency in the efficiency.

A Low-Level Carbon Dioxide Laser Promotes Fibroblast Proliferation and Migration through Activation of Akt, ERK, and JNK

BACKGROUND

Low-level laser therapy (LLLT) with various types of lasers promotes fibroblast proliferation and migration during the process of wound healing. Although LLLT with a carbon dioxide (CO2) laser was also reported to promote wound healing, the underlying mechanisms at the cellular level have not been previously described. Herein, we investigated the effect of LLLT with a CO2 laser on fibroblast proliferation and migration.

MATERIALS AND METHODS

Cultured human dermal fibroblasts were prepared. MTS and cell migration assays were performed with fibroblasts after LLLT with a CO2 laser at various doses (0.1, 0.5, 1.0, 2.0, or 5.0 J/cm2) to observe the effects of LLLT with a CO2 laser on the proliferation and migration of fibroblasts. The non-irradiated group served as the control. Moreover, western blot analysis was performed using fibroblasts after LLLT with a CO2 laser to analyze changes in the activities of Akt, extracellular signal-regulated kinase (ERK), and Jun N-terminal kinase (JNK), which are signaling molecules associated with cell proliferation and migration. Finally, the MTS assay, a cell migration assay, and western blot analysis were performed using fibroblasts treated with inhibitors of Akt, ERK, or JNK before LLLT with a CO2 laser.

RESULTS

In MTS and cell migration assays, fibroblast proliferation and migration were promoted after LLLT with a CO2 laser at 1.0 J/cm2. Western blot analysis revealed that Akt, ERK, and JNK activities were promoted in fibroblasts after LLLT with a CO2 laser at 1.0 J/cm2. Moreover, inhibition of Akt, ERK, or JNK significantly blocked fibroblast proliferation and migration.

CONCLUSIONS

These findings suggested that LLLT with a CO2 laser would accelerate wound healing by promoting the proliferation and migration of fibroblasts. Activation of Akt, ERK, and JNK was essential for CO2 laser-induced proliferation and migration of fibroblasts.

Murine Model Imitating Chronic Wound Infections for Evaluation of Antimicrobial Photodynamic Therapy Efficacy

It is generally acknowledged that the age of antibiotics could come to an end, due to their widespread, and inappropriate use. Particularly for chronic wounds alternatives are being thought. Antimicrobial Photodynamic Therapy (APDT) is a potential candidate, and while approved for some indications, such as periodontitis, chronic sinusitis and other niche indications, its use in chronic wounds is not established. To further facilitate the development of APDT in chronic wounds we present an easy to use animal model exhibiting the key hallmarks of chronic wounds, based on full-thickness skin wounds paired with an optically transparent cover. The moisture-retaining wound exhibited rapid expansion of pathogen colonies up to 8 days while not jeopardizing the host survival. Use of two bioluminescent pathogens; methicillin resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa permits real time monitoring of the pathogens. The murine model was employed to evaluate the performance of four different photosensitizers as mediators in Photodynamic Therapy. While all four photosensitizers, Rose Bengal, porphyrin TMPyP, New Methylene Blue, and TLD1411 demonstrated good to excellent antimicrobial efficacy in planktonic solutions at 1 to 50 μM concentrations, whereas in in vivo the growth delay was limited with 24–48 h delay in pathogen expansion for MRSA, and we noticed longer growth suppression of P. aeruginosa with TLD1411 mediated Photodynamic Therapy. The murine model will enable developing new strategies for enhancement of APDT for chronic wound infections.

Antimicrobial photodynamic therapy with fulleropyrrolidine: photoinactivation mechanism of Staphylococcus aureus, in vitro and in vivo studies

A family of N-methylpyrrolidinium fullerene iodide salts has been intensively studied to determine their applicability in antimicrobial photodynamic therapy (APDT). This study examined in vitro the efficacy of a C₆₀ fullerene functionalized with one methylpyrrolidinium group to kill upon irradiation with white light gram-negative and gram-positive bacteria, as well as fungal cells, and the corresponding mechanism of the fullerene bactericidal action. The in vitro studies revealed that the high antistaphylococcal efficacy of functionalized fullerene could be linked to their ability to photogenerate singlet oxygen and superoxide anion. Following Staphylococcus aureus photoinactivation, no modifications of its genomic DNA were detected. In contrast, photodamage of the cell envelope seemed to be a dominant mechanism of bactericidal action. In in vivo studies, a 2 log₁₀ reduction in the average bioluminescent radiance between treated and non-treated mice was reached. One day post APDT treatment, moist and abundant growth of bacteria could be observed on wounds of non-fulleropyrrolidine and dark control mice. APDT-treated wounds stayed visibly clear up to the third day. Moreover, cytotoxicity test on human dermal keratinocytes revealed great safety of using the sensitizer toward eukaryotic cells. These data indicate potential application of functionalized fullerene as antistaphylococcal sensitizer for superficial infections.

Effect of near-infrared light exposure on mitochondrial signaling in C2C12 muscle cells

Near-infrared (NIR) light is a complementary therapy used to treat musculoskeletal injuries but the underlying mechanisms are unclear. Acute NIR light treatment (~800-950 nm; 22.8 J/cm(2)) induced a dose-dependent increase in mitochondrial signaling (AMPK, p38 MAPK) in differentiated muscle cells. Repeated NIR light exposure (4 days) appeared to elevate oxidative stress and increase the upstream mitochondrial regulatory proteins AMPK (3.1-fold), p38 (2.8-fold), PGC-1α (19.7%), Sirt1 (26.8%), and reduced RIP140 (23.2%), but downstream mitochondrial regulation/content (Tfam, NRF-1, Sirt3, cytochrome c, ETC subunits) was unaltered. Our data indicates that NIR light alters mitochondrial biogenesis signaling and may represent a mechanistic link to the clinical benefits.

The effect of laser preexposure on seeding endothelial cells to a biomaterial surface

OBJECTIVE

In this study, the possible effect of low-level laser (LLL) on improving the adhesion of endothelial cells (ECs) to a biomaterial substrate was evaluated.

BACKGROUND DATA

Despite the numerous studies regarding the effects of LLL on biologic systems, the influence of LLL on the binding between cells and materials was rarely investigated.

MATERIALS AND METHODS

A low-power He-Ne laser apparatus with a continuous wavelength of 632.8 nm (a maximum power output of 50 mW) was used. The average irradiation energy on cells was 1.18 J/cm(2). Cell morphology and the concentrations of nitric oxide and calcium after laser exposure were measured. Biomedical grade poly(carbonate)urethane (PU) was synthesized and used to prepare microporous vascular grafts. ECs exposed to laser were harvested and seeded on the PU grafts. No further exposure was given.

RESULTS

LLL could change the morphology and increase the matrix secretion of ECs, and such effects persisted when preexposed cells were harvested and seeded to another substrate. The number of ECs attached on the biomaterial substrate was not affected. Preexposed ECs on the PU graft, however, were, on average, more resistant to flushing (i.e., greater cell retention).

CONCLUSION

ECs were pretreated with LLL before being seeded onto the PU biomaterial vascular grafts. The retention of LLL-preexposed ECs on the graft surface was enhanced, but not as significantly as that of ECs preexposed to low-intensity ultrasound.

Evaluation of mitochondrial respiratory chain activity in muscle healing by low-level laser therapy

BACKGROUND

Recent studies demonstrate that low-level laser therapy (LLLT) modulates many biochemical processes, especially the decrease of muscle injures, the increase in mitochondrial respiration and ATP synthesis for accelerating the healing process.

OBJECTIVE

In this work, we evaluated mitochondrial respiratory chain complexes I, II, III and IV and succinate dehydrogenase activities after traumatic muscular injury.

METHODS

Male Wistar rats were randomly divided into three groups (n=6): sham (uninjured muscle), muscle injury without treatment, muscle injury with LLLT (AsGa) 5J/cm(2). Gastrocnemius injury was induced by a single blunt-impact trauma. LLLT was used 2, 12, 24, 48, 72, 96, and 120 hours after muscle-trauma.

RESULTS

Our results showed that the activities of complex II and succinate dehydrogenase after 5days of muscular lesion were significantly increased when compared to the control group. Moreover, our results showed that LLLT significantly increased the activities of complexes I, II, III, IV and succinate dehydrogenase, when compared to the group of injured muscle without treatment.

CONCLUSION

These results suggest that the treatment with low-level laser may induce an increase in ATP synthesis, and that this may accelerate the muscle healing process.

Evaluation of mitochondrial respiratory chain activity in wound healing by low-level laser therapy

Laser therapy is used in many biomedical sciences to promote tissue regeneration. Many studies involving low-level laser therapy have shown that the healing process is enhanced by such therapy. In this work, we evaluated mitochondrial respiratory chain complexes II and IV and succinate dehydrogenase activities in wounds after irradiation with low-level laser. The animals were divided into two groups: group 1, the animals had no local nor systemic treatment and were considered as control wounds; group 2, the wounds were treated immediately after they were made and every day after with a low-level laser (AsGa, wavelength of 904 nm) for 10 days. The results showed that low-level laser therapy improved wound healing. Besides, our results showed that low-level laser therapy significantly increased the activities of complexes II and IV but did not affect succinate dehydrogenase activity. These findings are in accordance to other works, where cytochrome c oxidase (complex IV) seems to be activated by low-level laser therapy. Besides, we showed, for the first time, that complex II activity was also activated. More studies are being carried out in order to evaluate other mitochondrial enzymes activities after different doses and irradiation time of low-level laser.

A histologic assessment of the influence of low-intensity laser therapy on wound healing in steroid-treated animals

OBJECTIVE

The aim of the present study was to evaluate the effect of low-intensity laser therapy on the wound healing process treated with steroid.

BACKGROUND DATA

Various biological effects have been associated with low-level laser therapy (LLLT).

MATERIALS AND METHODS

Forty-eight rats were used, and after execution of a wound on the dorsal region of each animal, they were divided into 4 groups (n = 12), receiving the following treatments: G1 (control), wounds and animals received no treatment; G2, wounds were treated with LLLT; G3, animals received an intraperitoneal injection of steroid dosage (2 mg/kg of body weight); G4, animals received steroid and wounds were treated with LLLT. The laser emission device used was a GaAIAs (904 nm), in a contact mode, with 2.75 mW gated with 2.900 Hz during 120 sec (33 J/cm(2)). After the period of 3, 7, and 14 days, the animals were sacrificed and the parts sent to histological processing and dyed using hematoxylin and eosin (HE) and Masson trichromium (MT) techniques.

RESULTS

The results have shown that the wounds treated with steroid had a delay in healing, while LLLT accelerated the wound healing process. Also, wounds treated with laser in the animals treated with steroid presented a differentiated healing process with a larger collagen deposition and also a decrease in both the inflammatory infiltrated and the delay on the wound healing process.

CONCLUSION

LLLT accelerated healing, caused by the steroid, acting as a biostimulative coadjutant agent, balancing the undesirable effects of cortisone on the tissue healing process.

Effect of low-power laser irradiation on protein synthesis and ultrastructure of human gingival fibroblasts

BACKGROUND AND OBJECTIVES

Low-power lasers improve wound healing. Cell proliferation and protein secretion are important steps of this process. The aim of this study was to analyze both protein synthesis and ultrastructural morphology of human gingival fibroblasts irradiated by a low-power laser.

STUDY DESIGN/MATERIALS AND METHODS

The cell line FMM1 was grown in nutritional deficit. Laser irradiation was carried out with a gallium-aluminum-arsenate (Ga-Al-As) diode laser (904 nm, 120 mW, energy density of 3 J/cm(2)). The protein synthesis analysis and ultrastructural morphology of control (non-irradiated) and irradiated cultures were obtained.

RESULTS

There were changes in the structure of cytoplasm organelles of treated cells. The procollagen was not altered by the laser irradiation; however, there were a significant reduction of the amount of protein in the DMEM conditioned by irradiated cells.

CONCLUSIONS

Low-power laser irradiation causes ultrastructural changes in cultured fibroblasts. We suggest that these alterations may lead to disturbances in the collagen metabolism.

Investigation of the Supplementary Effect of GaAs Laser Therapy on the Rehabilitation of Human Digital Flexor Tendons

OBJECTIVE

To investigate the effect of laser photostimulation in rehabilitation of human digital flexor tendons with a placebo-controlled double-blind prospective study model.

BACKGROUND DATA

Low-energy laser therapy has been applied in several rheumatoid and soft tissue disorders with a varying rate of success and it has also been shown to have a positive effect on tendon healing in animal experiments, but no clinical study on laser photostimulation in the treatment of human tendons has been reported to date.

MATERIALS AND METHODS

This study was performed in a total of 25 patients with 41 digital flexor tendon injuries in five anatomical zones. In Group I (21 digits in 13 patients), whirlpool and infrared GaAs diode laser with a frequency of 100 Hz. was applied between the 8th and 21st days postoperatively and all patients were given the Washington rehabilitation program until the end of the 12th week. In Group II (20 digits in 12 patients), the same treatment protocol was given but the laser instrument was switched off during applications.

RESULTS

The results of the study showed a significant improvement in the laser-treated group only for the parameter of edema reduction (p < 0.01) but the difference between the two groups was non-significant for pain reduction, hand grip strength, and functional evaluation performed according to Strickland and Buck-Gramcko systems using total active motion and fingertip-to distal palmar crease distance parameters (p > 0.05).

CONCLUSIONS

Significant improvement obtained in edema reduction both immediately and 12 weeks after supplementary GaAs laser application in our study has been interpreted as an important contribution to the rehabilitation of human flexor tendon injuries because edema is known to have a detrimental effect on functional recovery during both early and late stages of tendon healing. However, our study has failed to show a significant positive effect of supplementary GaAs laser application on the other functional recovery parameters of human flexor tendon injury rehabilitation and we suggest further clinical study in this topic be done using different laser types and dosages in order to delineate the role of this promising treatment modality.

Usefulness of low-level laser for control of painful stomatitis in patients with hand-foot-and-mouth disease

OBJECTIVE

The aim of this study was to evaluate the usefulness of low-level laser therapy (LLLT) for the control of painful stomatitis in patients with hand-foot-and-mouth disease (HFMD).

BACKGROUND DATA

LLLT has been successfully applied to various painful oral mucosal diseases, although there have been few reports on LLLT for HFMD patients.

MATERIALS AND METHODS

Through a randomized double-blind placebo controlled trial, the painful period of HFMD stomatitis was compared between the LLLT group (n=11) and the placebo LLLT one (n=9), which had similar clinical backgrounds. The LLLT parameters supplied were as follows: wavelength of 830 nm, power of 30 mW, frequency of 30 Hz, and energy output of 1.1 J/cm2. Acceptability and safety of the treatment were also evaluated.

RESULTS

The painful period was shorter in the LLLT group (4.0 +/- 1.3 days) than in the placebo LLLT one (6.7 +/- 1.6 days) with a statistically significant difference (p<0.005). The treatment was judged acceptable for 90.0% (18 of 20) of patients. No adverse events were observed in any cases.

CONCLUSION

LLLT is a useful method to control HFMD stomatitis by shortening the painful period, with its high acceptability and lack of adverse events.

Investigation of the effect of GaAs laser therapy on cervical myofascial pain syndrome

Low-energy laser therapy has been applied in several rheumatoid and soft tissue disorders with varying rates of success. The objective of our study was to investigate the effect of laser therapy on cervical myofascial pain syndrome with a placebo-controlled double-blind prospective study model. It was performed with a total of 53 patients (35 females and 18 males) with cervical myofascial pain syndrome. In group 1 (n = 23), GaAs laser treatment was applied over three trigger points bilaterally and also one point in the taut bands in trapezius muscle bilaterally with a frequency of 1000 Hz for 2 min over each point once a day for 10 days during a period of 2 weeks. In group 2 (n = 25), the same treatment protocol was given, but the laser instrument was switched off during applications. All patients in both groups were instructed to perform daily isometric exercises and stretching just short of pain for 2 weeks at home. Evaluations were performed just before treatment (week 0), immediately after (week 2), and 12 weeks later (week 14). Evaluation parameters included pain, algometric measurements, and cervical lateral flexion. Statistical analysis was done on data collected from three evaluation stages. The results were evaluated in 48 patients (32 females, 16 males). Week 2 and week 14 results showed significant improvement in all parameters for both groups. However, comparison of the percentage changes both immediately and 12 weeks after treatment did not show a significant difference relative to pretreatment values. In conclusion, the results of our study have not shown the superiority of GaAs laser therapy over placebo in the treatment of cervical myofascial pain syndrome, but we suggest that further studies on this topic be done using different laser types and dosages in larger patient populations.

Effect of low-power laser irradiation on cell growth and procollagen synthesis of cultured fibroblasts

BACKGROUND AND OBJECTIVES

In dentistry, low-power lasers have been used in the treatment of dentin hypersensitivity, gingivitis, periodontitis, and different forms of oral ulcers. This in vitro study focuses on the biostimulation of NIH-3T3 fibroblasts by a low-power Ga-As-pulsed laser.

STUDY DESIGN/MATERIALS AND METHODS

We have studied cell growth and procollagen synthesis of cultured fibroblasts submitted to low-power laser irradiation with energy densities varying from 3 to 5 J/cm(2) over a period of 1-6 days. The light source was a 120 mW Ga-As diode laser (lambda = 904 nm). Growth curves and procollagen immunoprecipitation were obtained.

RESULTS

Irradiation of 3 and 4 J/cm(2) increased the cell numbers about threefold to sixfold comparing to control cultures. However, this effect was restricted to a small range of energy densities since 5 J/cm(2) had no effect on cell growth. The energy density of 3 J/cm(2) remarkably increased cell growth, with no effect on procollagen synthesis, as demonstrated by the immunoprecipitation analysis.

CONCLUSIONS

Our results showed that a particular laser irradiation stimulates fibroblast proliferation, without impairing procollagen synthesis.