Healing of burns after treatment with 670-nanometer low-power laser light

New approaches to second-degree burn healing: Polyvinyl alcohol membrane loaded to arnica combined to laser therapy

Second-degree burns require greater care, as the damage is more extensive and worrisome and the use of a biomaterial can help in the cell repair process, with better planning, low cost, and better accessibility. Arnica has anti-inflammatory and analgesic properties in skin lesions treatments and laser therapy is another therapeutic alternative for burns. Evaluate the effects of arnica incorporated into PVA associated or not with low intensity laser on burns in rats. PVA and PVA with arnica (PVA+A) were obtained and characterized physicochemically. Through in vivo studies, the effects of PVA and PVA+A with or without the application of laser on the lesions allowed histological and immunohistochemical analyzes. PVA+A was biocompatible and with sustained release of the active, being a promising pharmacological tool and confirmed that laser therapy was effective in accelerating the healing process, due to its potential biomodulator, improving inflammatory aspects, promoting rapid healing in skin lesions.

A novel therapeutic phosphate-based glass improves full-thickness wound healing in a rat model

Wound healing is a highly dynamic process and innovative therapeutic approaches are currently developed to address challenges of providing optimal wound care. In this study, phosphate-based glasses in the (CuO)_x ·(KPO₃ )_79.5-x ·(ZnO)₂₀ ·(Ag₂ O)_0.5 system (CuKPO₃ ZnAg), with different CuO/ KPO₃ ratios were prepared by melt-quenching technique. Constant Cu concentrations were released from the samples during immersion in Simulated Body Fluid (SBF), while Zn concentrations were slightly decreased over time. Glass surface phosphatation leading to formation of Zn crystalline salts was revealed through spectroscopic techniques. This finding was supported by SEM images that illustrated new compound formation. Subsequent cytotoxicity evaluation on HaCaT Keratinocytes using the indirect MTT cell viability assay revealed a CuO concentration-dependent cytotoxicity profile and excellent biocompatibility at low CuO concentrations, in all CuKPO₃ ZnAg glasses. Furthermore, the (CuO)₅ ·(KPO₃ )_74.5 ·(ZnO)₂₀ ·(Ag₂ O)_0.5 sample (5CuKPO₃ ZnAg)_, demonstrated superior antibacterial potency against S. aureus (ATCC 25923) strain compared to amoxicillin and ciprofloxacin. In vivo full-thickness wound healing evaluation showed a significantly higher regenerative effect of the 5CuKPO₃ ZnAg sample, in terms of angiogenesis, collagen synthesis and re-epithelialization compared to non-treated wounds. These findings advance our understanding of the therapeutic perspectives of phosphate-based glasses, showing promising potential for wound-healing applications.

Photobiomodulation Therapy in Burn Wound Healing: Systematic Review and Meta-Analysis of Preclinical Studies

Background and objective: To determine the effectiveness of photobiomodulation therapy (PBMT) in the burn wound healing compared with the control or with the use of antibiotics, in animal models. Materials and methods: A systematic search was conducted in EMBASE, MEDLINE, and LILACS databases. Preclinical studies were included that analyzed the effectiveness of PBMT in the burn wound healing, which assessed wound contraction, angiogenesis, proliferation of fibroblasts, and collagen deposition. SYRCLE risk of bias tool was used. Random effects models were used to estimate the pooled effect. Results: Thirty-eight studies were included. PBMT favored wound contraction (mean difference = -11.47, 95% confidence interval -19.87 to -3.08, I² = 0%; moderate certainty of evidence). PBMT also favored angiogenesis at doses between 11 and 20 J/cm², and increased the collagenization rate. Conclusions: In animal models, PBMT favored wound contraction, angiogenesis, and collagen deposition in second- and third-degree burn wounds.

Application of Solidago chilensis and laser improved the repair of burns in diabetic rats

Background

The repair of burns in diabetic patients is a clinical problem. It is relevant to study alternative therapies that can improve the healing process. Our aim was to investigate the effects of Solidago chilensis associated or not with laser on burns in diabetic rats.

Methods

The animals were divided in four groups (n = 30): C- without treatment; S– S. chilensis extract; L-laser irradiated; LS- laser and S. chilensis. In 7, 14 and 21 days samples were collected after the injury to structural, morphometric and molecular analysis.

Results

Our results demonstrate the association of S. chilensis and laser reduced the inflammatory infiltrate and favored the angiogenesis. In the groups treated only with laser or with the plant extract showed higher levels of VEGF. The low-level laser therapy (LLLT) promoted higher collagen I and reduction of collagen III. It was also observed higher MMP-2 activation and a decreasing of the active isoform of MMP-9 in the S, L and LS groups.

Conclusions

The treatments improved the repair of burns in diabetic rats, since it reduced the inflammatory infiltrate and favored the collagen organization presenting similar effects in the burn repair of the diabetics.

Use of a High-Power Laser for Wound Healing: A Case Report

Introduction: The use of low-level laser therapy to treat wounds and accelerate tissue healing has extensively been studied in recent years. The aim of this article is to describe a clinical case using an unfocused high-power laser instead of a low-power laser for therapy. Case Report: In the present article, we present the use of a high-power diode laser to treat an extensive knee injury that occurred after surgical treatment for total prosthesis due to border ischemia resulting from prolonged use of autostatic retractors. Conclusion: It is possible to use an unfocused high-power laser at a decreased intensity to accelerate healing as an adjuvant in the treatment of complicated wounds. This procedure results in reduced application time and cost and an excellent tissue response pattern similar to that reported in the literature with low-power lasers.

The effect of magnetic field therapy and electric stimulation on experimental burn healing

Objectives

: In this study, we aimed to compare morphological and histological differences between magnetic field and electric stimulation therapies in an experimental burn injury model in rats.

Materials and methods

Between February 2011 and July 2011, a total of 21 Sprague-Dawley female rats were used in this study. Second-degree burns were induced on the back areas of the rats. All rats were equally divided into three groups including seven in each: the first burn group was treated with antibacterial pomade (Group 1, control group); the second group was treated with both antibacterial pomade and pulsed electromagnetic field therapy (Group 2); and the third group was treated with antibacterial pomade and electric stimulation for 14 days (Group 3).

Results

Earlier re-epithelialization, wound area contraction, reduction of edema, and hyperaemia were observed on gross examination in the pulsed electromagnetic fields and electric stimulation therapy groups compared to the control group. Neovascularization, collagen density, granulation tissue formation, cell proliferation, and inflammatory cell response of the pulsed electromagnetic fields and electric stimulation group increased, compared to the control group, in the histopathological evaluation (p<0.05).

Conclusion

Our study results showed the positive healing effects of electric stimulation and pulsed electromagnetic fields on burn injury. Pulsed electromagnetic fields therapy produced more positive signs of healing than the electric stimulation group.

Effects of red laser, infrared, photodynamic therapy, and green LED on the healing process of third-degree burns: clinical and histological study in rats

The aim of this study was to evaluate the effects of red laser, infrared, photodynamic therapy, and green light-emitting diode (LED) on the healing process of skin burns through clinical and histopathologic analysis in rats. For this, 100 animals were randomly divided into five groups: G1-untreated control (CTR), G2-red laser (LVER), G3-infrared (LINF), G4-photodynamic therapy (PDT), and G5-green LED. Burn was induced on the dorsum of the rat and the treatment of the experimental groups was red light (10 J/cm(2), 10 s, 40 mW, and λ660 nm), infrared (10 J/cm(2), 10 s, 40 mW, and λ780 nm), green LED irradiation (60 J/cm(2), 10 s, λ520, and 550 nm), and photodynamic therapy (10 J/cm(2), 40 mW, and λ660 nm), the latter combined with methylene blue photosensitizer at concentration 0.5 μg/mL. Applications were performed daily until day prior to sacrifice of the animal at 3, 7, 14, and 21 days with intraperitoneal anesthetic overdose. The specimens collected were clinically examined and soon after processed and stained with hematoxylin-eosin and Picrosirius for analysis under light and polarized light microscopy, respectively. Animals treated with LVER, LINF, PDT (p < 0.001), and LED (p < 0.05) stimulated production and maturation of collagen, and increased the consumption of food and water compared to the CTR (p < 0.001). Laser λ660 nm and λ780 nm showed the largest wound reductions in all groups (p = 0.001). In conclusion, red laser, infrared, photodynamic therapy, and green LED favored the healing process of third-degree burns in rats.

Effect of extracorporeal shock wave treatment on deep partial-thickness burn injury in rats: a pilot study

Extracorporeal shock wave therapy (ESWT) enhances tissue vascularization and neoangiogenesis. Recent animal studies showed improved soft tissue regeneration using ESWT. In most cases, deep partial-thickness burns require skin grafting; the outcome is often unsatisfactory in function and aesthetic appearance. The aim of this study was to demonstrate the effect of ESWT on skin regeneration after deep partial-thickness burns. Under general anesthesia, two standardized deep partial-thickness burns were induced on the back of 30 male Wistar rats. Immediately after the burn, ESWT was given to rats of group 1 (N = 15), but not to group 2 (N = 15). On days 5, 10, and 15, five rats of each group were analyzed. Reepithelialization rate was defined, perfusion units were measured, and histological analysis was performed. Digital photography was used for visual documentation. A wound score system was used. ESWT enhanced the percentage of wound closure in group 1 as compared to group 2 (P < 0.05). The reepithelialization rate was improved significantly on day 15 (P < 0.05). The wound score showed a significant increase in the ESWT group. ESWT improves skin regeneration of deep partial-thickness burns in rats. It may be a suitable and cost effective treatment alternative in this type of burn wounds in the future.

Evaluation of the effect of thymoquinone treatment on wound healing in a rat burn model

Thymoquinone (TQ) is a plant extract that has been shown to have antimicrobial, anti-inflammatory, and antioxidant effects. Because of these activities, the authors hypothesized that TQ would reduce inflammation and oxidative stress and accelerate wound closure in a rat model of deep second-degree burns. For the purposes of this study, 40 Sprague-Dawley rats were divided into five groups of eight rats each. Group 1 was the control group, group 2 was the silver sulfadiazine group, group 3 was treated with systemic TQ, group 4 received topical TQ, and group 5 was administered topical and systemic TQ. After the deep second-degree burn damage was created, daily dressing changes and TQ administration were continued in the study groups for a period of 21 days. Systemic TQ was administered intraperitoneally at a dose of 2 mg/kg/day, whereas the topical treatment was applied using a 0.5% solution. The changes in the wound site were observed macroscopically, histopathologically, microbiologically, and biochemically in all groups. The smallest necrotic areas were observed at the end of the study in the groups that were administered a combination of systemic and topical TQ, or solely topical TQ (6.1 ± 1.6 cm and 6.7 ± 0.4 cm, respectively), whereas the largest necrotic areas were observed in the control group (11.2 ± 1.2cm). The total antioxidant state levels in the control group were significantly lower than in the other groups (P < .05), whereas the total oxidative stress levels were lower in the TQ groups compared with the control group (P < .05). The lowest bacterial counts were observed in the groups treated with both topical and systemic TQ (P < .05). TQ given systemically and/or topically reduced inflammation and oxidative stress and accelerated the rate of wound closure or reepithelialization.

The effect of hyperbaric oxygen treatment on the healing of burn wounds in nicotinized and nonnicotinized rats

The importance of oxygen in wound healing and the negative effects of cigarette smoking have been demonstrated in various studies. In this study, our aim was to investigate the effect of hyperbaric oxygen (HBO2) treatment on wound healing in nicotinized and nonnicotinized rats. The study was conducted on 32 Sprague Dawley rats. The rats were divided into four groups, with eight rats in each: group 1, nonnicotinized rats; group 2, nonnicotinized rats treated with HBO2; group 3, nicotinized rats; and group 4, nicotinized rats treated with HBO2. To prepare the nicotinized groups, the rats were given nicotine for 28 days. At the end of day 28, standard, deep, second-degree to third-degree burns were created on the rats. The HBO2-treated groups underwent HBO2 treatment once a day for 7 days after the creation of the burn damage. All rats were killed 21 days after injury, and the burns were subjected to macroscopic, histopathological, and microbiological evaluation. During this evaluation, the smallest necrotic areas and the lowest rate of fibrosis were observed in group 2. The largest necrotic areas and the highest inflammation and fibrosis rates were observed in the nicotine-treated group 3. When the nicotinized and nonnicotinized groups were compared separately, there was a significant difference in favor of the groups treated with HBO2. Bacterial growth was the highest in the nicotinized group 3, whereas no statistically significant difference was observed among the other groups. We conclude that HBO treatment accelerates the recovery of burn wounds and provides more effective healing by reducing the development of scars both in nicotinized and nonnicotinized rats.

Effect of equal daily doses achieved by different power densities of low-level laser therapy at 635 nm on open skin wound healing in normal and diabetic rats

BACKGROUND AND OBJECTIVE

Despite the fact that the molecular mechanism of low-level laser therapy (LLLT) is not yet known, the exploitation of phototherapy in clinical medicine and surgery is of great interest. The present study investigates the effects of LLLT on open skin wound healing in normal and diabetic rats.

MATERIALS AND METHODS

Four round full-thickness skin wounds on dorsum were performed in male adult nondiabetic (n = 24) and diabetic (n = 24) Sprague-Dawley rats. AlGaInP (635 nm, wavelength; 5 J/cm(2), daily dose) was used to deliver power densities of 1, 5, and 15 mW/cm(2) three times daily until euthanasia.

RESULTS

PMNL infiltration was lower in the irradiated groups (15 mW/cm(2)). The synthesis and organisation of collagen fibres were consecutively enhanced in the 5 mW/cm(2) and 15 mW/cm(2) groups compared to the others in nondiabetic rats. In the diabetic group the only significant difference was recorded in the ratio PMNL/Ma at 15 mW/cm(2). A significant difference in the number of newly formed capillaries in the irradiated group (5, 15 mW/cm(2)) was recorded on day six after injury compared to the control group.

CONCLUSION

LLLT confers a protective effect against excessive inflammatory tissue response; it stimulates neovascularization and the early formation of collagen fibres.

Anti-inflammatory effect of low-intensity laser on the healing of third-degree burn wounds in rats

Third-degree burn wounds are considered severe injuries because they destroy all the skin layers and may affect subcutaneous tissues, fasciae, muscles, and bones. To favor the healing process of the injured tissues, it is very useful to diminish the occurrence of the inflammatory process. The present study was aimed at comparing the effect of different energetic densities of AlGaInP laser on the inflammatory process and in the healing of third-degree burn wounds in Wistar rats. This study was approved by the Ethics Committee, in which 36 adult male rats were selected and suffered the induction of third-degree burn injury. These rats were divided as follows: group 1-control (treated with silver sulfadiazine), group 2-received energy density of 3 J/cm(2), and group 3-received energy density of 6 J/cm(2). All animals daily received an occlusive bandage with silver sulfadiazine and 8 % papain. The laser therapy was performed alternatively three times a week. The animals were evaluated on the 3rd, 7th, 14th, and 21st days after the initial lesion and euthanized for the macroscopic, histologic, and morphometric analysis. A higher production of collagen was observed at 7 days and a greater re-epithelialization at 21 days in group 3 (6 J/cm(2)). Furthermore, the latter when compared to the other groups presented macroscopically a better aspect of the scar at 21 days with more granulation tissue and fibrosis. We conclude that the AlGaInP laser used in dosages of 3 and 6 J/cm(2) favors the healing of third-degree burn wounds induced in rats.

Laser biomodulation of normal and neoplastic cells

This study was designed to determine the laser dose for the stimulation, zero-bioactivation, and inhibition of normal and neoplastic cells in vitro. The medical use of laser biomodulation has been occurring for decades in the area of tissue healing and inflammatory conditions. The potential to modulate the regeneration and differentiation of early cellular precursors by laser photons is a valuable endeavor searching for novel and efficient methods. A 35-mW HeNe (632.8-nm) laser and power density of 1.25 mW/cm(2) was used to irradiate tissue culture dishes seeded with 400 cells/dish of normal cells (CHO, CCL-226, 3 T3, and HSF) and neoplastic cells (EMT-6 and RIF-1). All cell lines were cultured using DMEM supplemented with 10% and 5% FBS, 2 mM glutamine and 100 U pen-strep antibiotic. Irradiation times of 16, 32, 48, 64, 80, 96, 112, 128, 144, and 160 s for three consecutive days to deliver cumulative doses of 60, 120, 180, 240, 300, 360, 420, 480, 540, and 600 mJ/cm(2) were done, respectively. Cell cultures were stained and colony-forming efficiency was determined. Data analysis was done using Student's t test, α = 0.05. A trend of stimulation, zero-bioactivation, and inhibition in all cell lines was observed except for CCL-226 which gave a pattern of inhibition, zero-bioactivation, and inhibition. The optimum biostimulatory dose was at 180 mJ/cm(2) and bioinhibitory doses were from 420-600 mJ/cm(2) cumulative doses. This study established the dose-dependency of cell growth to laser treatments, that the extent of cellular proliferation is influenced by the type of cells involved, and the risk when laser irradiation is performed on patients with undiagnosed neoplasms and during pregnancy. On the other hand, the ability of laser irradiation to regulate embryonic fibroblasts and human skin fibroblast in vitro suggests possible laser biomodulatory effects on embryonic and adult stem cells directed for tissue regeneration. Studies on the effects of light treatments exploring different laser parameters for the clonal expansion and differentiation of stem cells are recommended.

Low-level laser therapy using 80-Hz pulsed infrared diode laser accelerates third-degree burn healing in rat

OBJECTIVE

To evaluate 80-Hz pulsed infrared diode low-level laser therapy (LLLT) for third-degree burn healing in rats.

BACKGROUND DATA

Review of the literature indicates that LLLT has a biostimulatory effect on wound healing, although no clear recommendation can be made yet.

METHODS

Forty-eight male rats were divided into groups 1 and 2. On day 0, three third-degree burns were made on the dorsum of each rat using steam. In group 1, the first burn was exposed to an 80-Hz pulsed 890-nm infrared diode laser at 0.396 J/cm2 three times a week. In group 2, the first burn was exposed to the inactivated laser. In both groups, the second burns were treated with topical application of nitrofurazone 0.2%, and third burns did not receive any treatment and were considered as control burns. Burns were clinically examined. The rats were treated for 8, 12, and 20 days in both groups. On days 8, 2, and 20, microbiological samples of burns were collected and analyzed. Data were analyzed using the chi-square method.

RESULTS

The paired Student t-test showed that the wound closure rate of laser-treated burns (17.6+/-1.86 days) was significantly longer than that of the control burns (19.6+/-0.81 days) (p=0.007).The number of laser-treated burns that closed was significantly higher than controls. Chi-square tests showed that there was not significant difference between each microorganism (Staphylococcus epidermis, S. aureus and Pseudomonas aeruginosa).

CONCLUSION

LLLT using an 80-Hz pulsed infrared diode laser accelerated third-degree burn healing in rat.

The use of light photobiomodulation on the treatment of second-degree burns: a histological study of a rodent model

OBJECTIVE

The aim of this investigation was to compare, by light microscopy, the effects of the use of laser photobiomodulation (LPBM) and polarized light (PL) on second-degree burns on rodents.

BACKGROUND DATA

Burns are severe injuries that result in the loss of tissue fluids, destruction of tissues, infection, and shock. With severe and widespread third-degree burns death may occur. Several light sources have been suggested as being effective for improving wound healing.

MATERIALS AND METHODS

Forty five rats were used in this study. A second-degree burn was created on the dorsum of each animal, and the animals were divided into four groups: PL (400-2000 nm, 40 mW, 2.4 J/cm(2)/min); LPBM-1 (780 nm, 35/40 mW, theta approximately 2 mm, 4 x 5 J/cm(2)); LPBM-2 (660 nm, 35/40 mW, theta approximately 2 mm, 4 x 5 J/cm(2)); and untreated animals acted as controls. The treatment was started immediately post-burn at four points around the burned area (laser: 5 J/cm(2) per site). The illumination with PL was performed according to the manufacturer's instructions. Treatments were repeated at 24-h intervals for 7 d. The animals were sacrifice at 3, 5, and 7 d post-burn. The specimens were routinely cut and stained and analyzed by light microscopy using hematoxylin and eosin and Sirius red.

RESULTS

The analysis of the results demonstrated that the damaged tissue was able to efficiently absorb and process the light at all tested wavelengths. LPBM at 660 nm showed better results at early stages of wound healing. However, the use of 780-nm laser light had beneficial effects throughout the experimental period, with the animals growing newly-formed tissue similar to normal dermis.

CONCLUSION

Despite our findings that the use of both types of light energy improved the healing of second-degree burns at the early stages, long-term assessment is needed to verify if this improvement will influence the final results of treatment.

Effects of a single near-infrared laser treatment on cutaneous wound healing: Biometrical and histological study in rats

BACKGROUND

Low intensity laser therapy has been recommended to support the cutaneous repair; however, so far studies do not have evaluated the tissue response following a single laser treatment. This study investigated the effect of a single laser irradiation on the healing of full-thickness skin lesions in rats.

METHODS

Forty-eight male rats were randomly divided into three groups. One surgical lesion was created on the back of rats using a punch of 8mm in diameter. One group was not submitted to any treatment after surgery and it was used as control. Two energy doses from an 830-nm near-infrared diode laser were used immediately post-wounding: 1.3 J cm(-2) and 3 J cm(-2). The laser intensity 53 m W cm(-2) was kept for both groups. Biometrical and histological analyses were accomplished at days 3, 7 and 14 post-wounding.

RESULTS

Irradiated lesions presented a more advanced healing process than control group. The dose of 1.3 J cm(-2) leaded to better results. Lesions of the group irradiated with 1.3 J cm(-2) presented faster lesion contraction showing quicker re-epithelization and reformed connective tissue with more organized collagen fibers.

CONCLUSIONS

Low-intensity laser therapy may accelerate cutaneous wound healing in a rat model even if a single laser treatment is performed. This finding might broaden current treatment regimens.

The efficacy of linear polarized polychromatic light on burn wound healing: an experimental study on rats

We aimed to investigate the questionable effect of linear polarized polychromatic light on burn wound healing in rats. Two deep second-degree burn wounds on the backside of each of 21 Sprague-Dawley rats were created with a standard burning procedure by applying a heated plaque. Burned regions located right dorsolaterally and classified as group I lesions were treated with linear polarized polychromatic light + open dressing + antibacterial pomade, whereas group II lesions were located left dorsolaterally and treated with only open dressing + antibacterial pomade. Macroscopic evaluation was performed for determination of the completed wound closure rate, measurement of burn wound area, and investigation of macroscopic edema, hyperemia, and epithelialization. Histopathological evaluation included monitoring of epithelialization, vascularization, origination of granulation tissue, inflammatory cell response, and total histopathological score on days 7, 14, and 21 after burn creation. Macroscopic evaluation revealed more obvious epithelialization in group I lesions between days 6 and 15. The number of completely closed wounds was higher in group I than in group II on days 16 and 21. The average area of burn wounds was lower from day 5, hyperemia was less on days 2 to 17, and edema was less from day 4 to day 13 in group I lesions. Histopathological evaluation revealed a higher rate of epithelialization on day 7 and higher vascularization occurrence on day 21 in group I lesions. Linear polarized polychromatic light seems to be effective in the treatment of burn wounds and in the promotion of healing. This may be related to linear polarized polychromatic light stimulation of epithelialization and vascularization.

Histological Assessment of the Effect of Laser Irradiation on Skin Wound Healing in Rats

OBJECTIVE

The purpose of this study was to evaluate, from the histological point of view, the effect of diode laser irradiation on skin wound healing in Sprague-Dawley rats.

BACKGROUND DATA

Various biological effects have been described in different studies after low-level laser therapy (LLLT).

METHODS

Two parallel full-thickness skin incisions were performed on the back of each rat (n = 49) and immediately sutured. After surgery, one wound of each rat was exposed to laser irradiation (continuous mode, 670 nm, daily dose 30 J/cm2), whereas the parallel wound was not irradiated and served as control. Both wounds were removed 24, 48, 72, 96, 120, 144, and 168 h after surgery and routinely fixed and embedded in paraffin sections, stained with hematoxylin and eosin, van Gieson, periodic acid Schiff + periodic acid Schiff diastase, Mallory's phosphotungstic hematoxylin, and azur and eosin, and histopathologically evaluated.

RESULTS

As compared to nonirradiated control wounds, laser stimulation shortened the inflammatory phase as well as accelerated the proliferative and maturation phase, and positively stimulated the regeneration of injured epidermis and the reparation of injured striated muscle.

CONCLUSION

LLLT at 670 nm positively influences all phases of rat skin wound healing.

Low-Level Laser Therapy for Wound Healing: Mechanism and Efficacy

BACKGROUND

Given the recent interest in light-emitting diode (LED) photomodulation and minimally invasive nonablative laser therapies, it is timely to investigate reports that low-level laser therapy (LLLT) may have utility in wound healing.

OBJECTIVES

To critically evaluate reported in vitro models and in vivo animal and human studies and to assess the qualitative and quantitative sufficiency of evidence for the efficacy of LLLT in promoting wound healing.

METHOD

Literature review, 1965 to 2003.

RESULTS

In examining the effects of LLLT on cell cultures in vitro, some articles report an increase in cell proliferation and collagen production using specific and somewhat arbitrary laser settings with the helium neon (HeNe) and gallium arsenide lasers, but none of the available studies address the mechanism, whether photothermal, photochemical, or photomechanical, whereby LLLT may be exerting its effect. Some studies, especially those using HeNe lasers, report improvements in surgical wound healing in a rodent model; however, these results have not been duplicated in animals such as pigs, which have skin that more closely resembles that of humans. In humans, beneficial effects on superficial wound healing found in small case series have not been replicated in larger studies.

CONCLUSION

To better understand the utility of LLLT in cutaneous wound healing, good clinical studies that correlate cellular effects and biologic processes are needed. Future studies should be well-controlled investigations with rational selection of lasers and treatment parameters. In the absence of such studies, the literature does not appear to support widespread use of LLLT in wound healing at this time. Although applications of high-energy (10-100 W) lasers are well established with significant supportive literature and widespread use, conflicting studies in the literature have limited low-level laser therapy (LLLT) use in the United States to investigational use only. Yet LLLT is used clinically in many other areas, including Canada, Europe, and Asia, for the treatment of various neurologic, chiropractic, dental, and dermatologic disorders. To understand this discrepancy, it is useful to review the studies on LLLT that have, to date, precluded Food and Drug Administration approval of many such technologies in the United States. The fundamental question is whether there is sufficient evidence to support the use of LLLT.

Effect of low-level helium-neon laser therapy on the healing of third-degree burns in rats

This paper presents the results of a study on the effects of low-level helium-neon laser therapy (LL He-Ne LT) on the healing of burns. Seventy-eight adult male rats, having been subjected to third-degree burns, were randomly divided into four groups: two laser treated groups (n=20, each), one control group (n=19) and one nitrofurazone treated group (n=19). In the two laser treated groups, the burns were treated on a daily basis with LL He-Ne LT with an energy density of 1.2 and 2.4 J/cm(2), respectively. The response to treatment was assessed histologically at 7, 16 and 30 days after burning, and microbiologically at day 15. Analysis of variance showed that the mean of blood vessel sections in the 1.2J/cm(2) laser group was significantly higher than those in the other groups and the mean of the depth of new epidermis in the 2.4 J/cm(2) laser group on day 16 was significantly lower than in the nitrofurazone treated group (P=0.025, P=0.047, respectively). When Staphylococcus aureus and Pseudomonas aeruginosa grew in more than 50% of samples obtained from control group, there were no S. aureus and P. aeruginosa in the samples of 2.4 J/cm(2) laser group. It is concluded that LL He-Ne LT induced the destruction of S. aureus and P. aeruginosa in third-degree burns of rats, yet at the same time our histological findings showed that LL He-Ne LT caused a significant increase in the mean of blood vessel sections on day 7 after third degree burns and a decrease in the mean of the depth of new epidermis on day 16 after the same burns in rats.

Polarized Light (400–2000 nm) and Non-ablative Laser (685 nm): A Description of the Wound Healing Process Using Immunohistochemical Analysis

OBJECTIVE

This study aimed to describe, through morphologic and cytochemical analysis, the healing process of wounds submitted (or not) to laser therapy (lambda685 nm) or polarized light (lambda400-2000 nm).

BACKGROUND DATA

There are many reports on different effects of several types of phototherapies on the treatment of distinct conditions, amongst them, on wound healing. Laser therapy and the use of polarized light are still controversial despite successive reports on their positive effects on several biological processes.

METHODS

Thirty male Wistar rats, approximately 4 months old, were used, and standardized excisional wounds were created on their dorsum. The wounds were irradiated in four equidistant points with laser light or illuminated with polarized light, both with doses of 20 or 40 J/cm2. Group 1 acted as untreated controls. Animals were irradiated every 48 h during 7 days, starting immediately after surgery, and were humanely killed on the 8th post-operative day. Specimens were taken and routinely processed and stained with H&E, and for descriptive analysis of myofibroblasts and collagen fibers, the specimens were imunnomarked by smooth muscle alpha-actin and picrosirius stain.

RESULTS

Control specimens showed the presence of ulceration, hyperemia, discrete edema, intense, and diffuse inflammation, collagen deposition was irregular, and myofibroblasts were seen parallel to the wound margins. Wounds treated by laser therapy with a dose of 20 J/cm2 showed mild hyperemia, inflammation varied from moderate to intense, the number of fibroblasts was large, and the distribution of collagen fibers was more regular. Increasing the dose to 40 J/cm2 evidenced exuberant neovascularization, severe hyperemia, moderate to severe inflammation, large collagen deposition, and fewer myofibroblasts. On subjects illuminated with polarized light with a dose of 20 J/cm2, mild to moderate hyperemia was detectable, and collagen matrix was expressive and unevenly distributed; a larger number of myofibroblasts was present and no re-epithelialization was seen. Increasing the dose resulted in mild to moderate hyperemia, no re-epithelialization was seen, edema was discrete, and inflammation was moderate.

CONCLUSION

The use of 685-nm laser light or polarized light with a dose of 20 J/cm2 resulted in increased collagen deposition and better organization on healing wounds, and the number of myofibroblast was increased when polarized light is used.

Burn healing with a diode laser: 670 nm at different doses as compared to a placebo group

OBJECTIVE

A study on burn healing in rats was initiated using a diode laser at varied doses for determination of optimum dosimetry and treatment schedule.

MATERIALS AND METHODS

A number of male Sprague-Dawley rats were randomly assigned to several groups. Anesthesia (a mixture of ketamine HCl and Xylocaine) was administered intraperitoneally. Burn on both flanks was created using a preheated metal probe and measured daily using a caliper. The right side of the treated rats was irradiated five times and three times per week. Slopes from the actual burn areas were obtained and compared against the control with the healing rate calculated and expressed in percent.

RESULTS

In reference to the control group, no significant difference in healing was observed. In comparing both treatment schedules, there was likewise no significant difference at any day in both age-groups. Notably in younger rats, accelerated healing was observed with the highest rate in the lower range of doses (1 and 5 J/cm2), 12.4% and 11.6%, respectively.

CONCLUSION

This experiment affirms that the beneficial effect on burn healing in rats is indeed affected by an interplay of several factors.

Effect of low-level laser therapy on the healing of second-degree burns in rats: a histological and microbiological study

This paper presents the results of a study on the effects of two different doses of low-level laser therapy on healing of deep second-degree burns. Sixty rats were randomly allocated to one of four groups. A deep second-degree burn was inflicted in each rat. In the control group burns remained untreated; in two laser treated groups the burns were irradiated daily with low-level helium-neon laser with energy densities of 1.2 and 2.4 J/cm2, respectively. In the fourth group the burns were treated topically with 0.2% nitrofurazone cream every day. The response to treatments was assessed histologically at 7, 16 and 30 days after burning, and microbiologically at Day 15. The number of macrophages at day 16, and the depth of new epidermis at day 30, was significantly less in the laser treated groups in comparison with control and nitrofurazone treated groups (P=0.000). Staphylococcus epidermidis was found in the 70% of rat wounds in the laser treated groups in comparison with 100% of rats in the control group. S. aureus was found in the 40% rat wounds in the nitrofurazone treated group, but there was not found in the wounds of laser treated, and control groups. It is concluded that low-level laser therapy of deep second-degree burn caused significant decrease in the number of macrophage and depth of new epidermis. In addition, it decreased incidence of S. epidermidis and S. aureus.

Clinical trial of a novel non-thermal LED array for reversal of photoaging: Clinical, histologic, and surface profilometric results

BACKGROUND AND OBJECTIVES

Photomodulation has been described as a process which modifies cell activity using light sources without thermal effect. The objective of this study was to investigate the use of a non-thermal low dose light emitting diode (LED) array for improving the appearance of photoaged subjects.

STUDY DESIGN/MATERIALS AND METHODS

This prospective study investigated a random cohort of patients (N = 90) with a wide range of photoaged skin treated by LED photomodulation using a full panel 590 nm non-thermal full face LED array delivering 0.1 J/cm(2) with a specific sequence of pulsing. Subjects were evaluated at 4, 8, 12, 18 weeks and 6 and 12 months after a series of 8 treatments delivered over 4 weeks. Data collected included stereotactic digital imaging, computerized optical digital profilometry, and peri-ocular biopsy histologic evaluations for standard stains and well as collagen synthetic and degradative pathway immunofluorescent staining.

RESULTS

Digital imaging data showed a reduction of signs of photoaging in 90% of subjects with smoother texture, reduction of peri-orbital rhytids, and reduction of erythema and pigmentation. Optical profilometry showed a 10% improvement by surface topographical measurements. Histologic data showed markedly increased collagen in the papillary dermis of 100% of post-treatment specimens (N = 10). Staining with anti-collagen I antibodies demonstrated a 28% (range: 10%-70%) average increase in density while staining with anti-matrixmetalloproteinase (MMP)-1 showed an average reduction of 4% (range: 2%-40%). No side effects or pain were noted.

CONCLUSIONS

Photomodulation to reverse photoaging is possible with a specific array of LEDs with a specific fluence using a precise pulsing or "code" sequence. Skin textural improvement by digital imaging and surface profilometry is accompanied by increased collagen I deposition with reduced MMP-1 (collagenase) activity in the papillary dermis. This technique is a safe and effective non-painful non-ablative modality for improvement of photoaging.

A Preliminary Report on the Effect of Laser Therapy on the Healing of Cutaneous Surgical Wounds as a Consequence of an Inversely Proportional Relationship between Wavelength and Intensity: Histological Study in Rats

OBJECTIVE

The objective of the present investigation was to assess the histological effects of different wavelengths and intensities on the healing process of cutaneous wounds.

BACKGROUND DATA

Tissue repair is a dynamic interactive process which involves mediators, cells and extra-cellular matrix. Several reports on the use of laser therapy have shown that the healing process is positively affected when the correct parameters are used.

METHODS

Eighteen standardized wounds were surgically created on the dorsum of male and female Wistar rats, which were subsequently divided into two experimental groups according to wavelength used lambda.670 or lambda685 nm) for lasertherapy (LLLT). Each group was divided into three subgroups of three animals according to the intensity of the applied irradiation (2, 15, or 25 mW). Twelve animals were used as untreated controls and were not irradiated. The irradiation was carried out during seven consecutive days. The animals were sacrificed eight days after surgery. The specimens were removed, kept in 4% formaldehyde for 24 h, routinely prepared to wax, stained with H&E, and analyzed under light microscopy.

RESULTS

For both groups, light microscopy showed a substitution repair process; however, when LLLT was used, a positive biomodulatory effect was detectable, chiefly associated with shorter wavelength and low intensity.

CONCLUSIONS

The results of the present study indicate that LLLT improved cutaneous wound repair and that the effect is a result of an inversely proportional relationship between wavelength and intensity, with treatment more effective when combining higher intensity with short wavelength or lower intensity with higher wavelength.

The use of polarized light in aesthetic surgery

This article presents a clinical investigation of polarized light therapy after aesthetic surgery procedures. The study included patients who the authors underwent face-lifts, blepharoplasties, and various facial ancillary procedures, at center during the past 2 1/2 years. One side of the surgically treated area was managed with polarized light, whereas the other side served as a control. The results were compared using clinical examination only including signs of recovery such as resolution of swelling and bruises. The results in most cases showed a significant difference between the treated and untreated sides.

Low Level Laser Therapy—a conservative approach to the burn scar?

Burn scars are known to be difficult to treat because of their tendency to worsen with hypertrophy and contracture. Various experimental and clinical efforts have been made to alleviate their effects but the problem has not been solved. Since patients keep asking for Low Level Laser Therapy (LLLT) and believe in its effectiveness on burn scars, and since former studies show contradictory results of the influence of LLLT on wound healing, this prospective study was designed to objectify the effects of LLLT on burn scars. Nineteen patients with 19 burn scars were treated with a 400 mW 670 nm Softlaser twice a week over 8 weeks. In each patient a control area was defined, that was not irradiated. Parameters assessed were the Vancouver Scar Scale (VSS) for macroscopic evaluation and the Visual Analogue Scale (VAS) for pruritus and pain. Photographical and clinical assessments were recorded in all the patients. Seventeen out of 19 scars exhibited an improvement after treatment. The average rating on the VSS decreased from 7.10+/-2.13 to 4.68+/-2.05 points in the treated areas, whereas the VSS in the control areas decreased from 6.10+/-2.86 to 5.88+/-2.72. A correlation between scar duration and improvement through LLLT could be found. No negative effects of LLLT were reported. The present study shows that the 400 mW 670 nm softlaser has a positive, yet sometimes limited effect on burn scars concerning macroscopic appearance, pruritus, and pain.

Promotive effects of far-infrared ray on full-thickness skin wound healing in rats

The biological effects of far-infrared ray (FIR) on whole organisms remain poorly understood. The aim of our study was to investigate not only the hyperthermic effect of the FIR irradiation, but also the biological effects of FIR on wound healing. To evaluate the effect of FIR on a skin wound site, the speed of full-thickness skin wound healing was compared among groups with and without FIR using a rat model. We measured the skin wound area, skin blood flow, and skin temperature before and during FIR irradiation, and we performed histological inspection. Wound healing was significantly more rapid with than without FIR. Skin blood flow and skin temperature did not change significantly before or during FIR irradiation. Histological findings revealed greater collagen regeneration and infiltration of fibroblasts that expressed transforming growth factor-beta1 (TGF-beta1) in wounds in the FIR group than in the group without FIR. Stimulation of the secretion of TGF-beta1 or the activation of fibroblasts may be considered as a possible mechanisms for the promotive effect of FIR on wound healing independent of skin blood flow and skin temperature.

A conservative approach for deep dermal burn wounds using polarised-light therapy

This article reports a clinical study investigating the role of polarised-light therapy in the conservative treatment of deep dermal burn wounds. In 22 out of 67 patients with deep dermal burn wounds, clinical evaluation revealed only a very limited potential for spontaneous healing, and, despite the fact that the majority of the surgeons (four out of six) would have recommended surgery, these patients were treated conservatively with polarised-light therapy (400-2000 nm, 40 m W cm(-2), 2.4 J cm(-2)) until complete closure. Evaluation by a panel of four surgeons, all experts in burn surgery, revealed that conservative treatment of these deep dermal wounds with polarised-light irradiation resulted in a significantly shorter healing time, with almost no hypertrophic scarring, and optimal aesthetic and functional results at long-term follow-up. No extension of the hospital stay was required. Polarised-light therapy may be a valuable way of avoiding surgery in patients with deep dermal burns.

830-nm irradiation increases the wound tensile strength in a diabetic murine model

BACKGROUND AND OBJECTIVE

The purpose of this study was to investigate the effects of low-power laser irradiation on wound healing in genetic diabetes.

STUDY DESIGN/MATERIALS AND METHODS

Female C57BL/Ksj/db/db mice received 2 dorsal 1 cm full-thickness incisions and laser irradiation (830 nm, 79 mW/cm(2), 5.0 J/cm(2)/wound). Daily low-level laser therapy (LLLT) occurred over 0-4 days, 3-7 days, or nonirradiated. On sacrifice at 11 or 23 days, wounds were excised, and tensile strengths were measured and standardized.

RESULTS

Nontreated diabetic wound tensile strength was 0.77 +/- 0.22 g/mm(2) and 1.51 +/- 0.13 g/mm(2) at 11 and 23 days. After LLLT, over 0-4 days tensile strength was 1.15 +/- 0.14 g/mm(2) and 2.45 +/- 0.29 g/mm(2) (P = 0.0019). Higher tensile strength at 23 days occurred in the 3- to 7-day group (2.72 +/- 0.56 g/mm(2) LLLT vs. 1.51 +/- 0.13 g/mm(2) nontreated; P < or = 0.01).

CONCLUSION

Low-power laser irradiation at 830 nm significantly enhances cutaneous wound tensile strength in a murine diabetic model. Further investigation of the mechanism of LLLT in primary wound healing is warranted.