Rapid Communication: The Effect of Low-Power He-Ne and He-Cd Laser Therapy on Wound Healing of Rats

Low-Level Laser Therapy Enhances Wound Healing in Diabetic Rats: A Comparison of Different Lasers

OBJECTIVE

The effects of wound healing acceleration on diabetic rats were determined and compared using different laser wavelengths and incident doses.

BACKGROUND DATA

Many studies have demonstrated that low-level laser therapy (LLLT) can promote the wound healing on non-diabetic animals.

METHODS

Male Sprague-Dawley rats were used. Streptozotocin (70 mg/kg) was applied for diabetes induction. An oval full-thickness skin wound was created aseptically with a scalpel in 51 diabetic rats and six non-diabetic rats on the shaved back of the animals. The study was performed using 532, 633, 810, and 980 nm diode lasers. Incident doses of 5, 10, 20, and 30 J/cm(2) and treatment schedule of 3 times/week were used in the experiments. The area of wound on all rats was measured and plotted on a slope chart. The slope values (mm(2)/day), the percentage of relative wound healing, and the percentage of wound healing acceleration were computed in the study.

RESULTS

Mean slope values were 6.0871 in non-diabetic control and 3.636 in diabetic control rats (p > 0.005). The percentages of wound healing acceleration were 15.23, 18.06, 19.54, and 20.39 with 532-nm laser, 33.53, 38.44, 32.05, and 16.45 with 633-nm laser, 15.72, 14.94, 9.62, and 7.76 with 810-nm laser, and 12.80, 16.32, 13.79, and 7.74 with 980-nm laser, using incident doses of 5, 10, 20, and 30 J/cm(2), respectively. There were significant differences (p > 0.001) in the mean slope value of wound healing on diabetic rats between control groups and treatment groups in 532, 633, 810, and 980 nm lasers.

CONCLUSION

The wound healing on control rats with diabetes was slower than on control rats without diabetes. LLLT at appropriate treatment parameters can enhance the wound healing on diabetic rats. The optimum wavelength was 633 nm, and the optimum incident dose was 10 J/cm(2) in our study.

Photobiological Basis and Clinical Role of Low-Intensity Lasers in Biology and Medicine

The purpose of this article is to provide a comprehensive review on the clinical role of low intensity laser therapy (laser photostimulation) in biology and medicine. Studies on wound healing and pain relief are highlighted to show the clinical efficacy of laser therapy. Controversies about the use of low intensity laser as a therapeutic modality for wound healing and pain relief are presented and a brief explanation is provided to overcome these controversies. The importance of standard parameters is emphasized for the applications of low intensity lasers in biology and medicine. A justification has been made to warrant further research on the use of low intensity laser as a therapeutic modality. Although the therapeutic applications of low intensity laser are imminent, the heterogeneity in treatment protocols and study design calls for a vigilant interpretation of the findings.

The Comparison of Effects between Pulsed and CW Lasers on Wound Healing

OBJECTIVE

In order to evaluate the effects of pulsed continuous wave (CW) laser and detect the role of wound healing in rats using both pulsed and CW 635-nm low-level laser therapy (LLLT), a pilot study was undertaken.

BACKGROUND DATA

Some acceleration effects of wound healing on animals were found after treatment using various lasers with CW. There are other reports, however, using pulsed CW laser to evaluate the effects of wound healing in rats.

MATERIALS AND METHODS

An elliptic wound was created aseptically with a scalpel on the shaved back of the rats after anesthesia. The rats treated were restrained in a Plexiglas cage without anesthesia during the laser irradiation period. An Erchonia pulse laser (635 nm) was used in the experiment. The laser beam was delivered through an expander. The percentage of relative wound healing was calculated.

RESULTS

The percentage of relative wound healing was 4.32 in 100 Hz, 3.21 in 200 Hz, 3.83 in 300 Hz, 2.22 in 400 Hz, 1.73 in 500 Hz and 4.81 in CW.

CONCLUSION

LLLT using pulsed, CW laser at the appropriate dosimetry and frequency can provide acceleration in wound healing in rats. The 100-Hz frequency had a better effect than other pulse frequencies used in the study. The effects of treatment using CW laser was higher than pulse frequency. The frequency of pulsed CW laser was not found to increase wound healing in rats compared with normal CW laser, as reported in our previous studies.

Comparison of the photostimulatory effects of visible He-Ne and infrared Ga-As lasers on healing impaired diabetic rat wounds

BACKGROUND AND OBJECTIVES

In this study, the ability of photostimulation to promote healing of impaired wounds was investigated using a Ga-As laser in rats with experimental diabetes and the results were compared with previously reported findings of the effects of a He-Ne laser on the repair of healing-impaired diabetic rat wounds 1.

STUDY DESIGN/MATERIALS AND METHODS

Diabetes was induced in male rats by streptozotocin injection following which two full thickness punch wounds of 6-mm diameter were created in the skin, one on either side of the spine of each animal. The left wound of each animal was treated with infrared radiation at 904 nm produced by a Ga-As laser at an energy density of 1.0 J/cm(2). The right wound of each animal served as the control. The wounds were treated with a laser 5 days a week for 3 weeks. Following animal sacrifice, the strips of skin containing the wound sites were collected and analyzed.

RESULTS

The results from the biomechanical analysis indicated that the Ga-As laser used in this study significantly increased wound tensile strain and toughness compared to the control wounds. Marginal increases in wound tensile strength (9%) and stress (7%) were observed in the Ga-As laser-treated wounds compared to the controls. No significant changes were found in Young's modulus and energy absorption capacity between the control and laser-treated wounds. Analysis of wound collagen revealed a significant increases in total collagen (14%), salt soluble collagen (31%), acid soluble (14%), and insoluble collagen (50%) with simultaneous decrease in pepsin soluble collagen (19%) in the Ga-As laser-treated wounds compared to controls. Comparisons of these results with the earlier findings revealed that the He-Ne laser appears to be superior to the Ga-As laser, at the parameters of treatment tested, in promoting the wound healing in diabetic rats.

CONCLUSIONS

The differences in stimulatory effects noted between the He-Ne and Ga-As lasers suggest that the photochemical response the cells for each laser may depend on the wavelength and coherent properties of the electromagnetic radiation.

Photodynamic modulation of wound healing with BPD-MA and CASP

BACKGROUND AND OBJECTIVE

Wound healing is an intricate process requiring the orchestration of cells, growth factors, cytokines, and the extracellular matrix. Cytokines, specifically TGF-beta, are believed to be instrumental in sustaining the fibrotic process, which leads to scarring. Photodynamic therapy (PDT) uses potent photosensitizers, which induce a wide range of effects on cells and the extracellular matrix. The influences of PDT on wound healing are not well known.

STUDY DESIGN/MATERIALS AND METHODS

Seven full-thickness incisional wounds were placed on each of 24 hairless Sprague Dawly rats, three wounds on one flank serving as dark controls and four on the contralateral side treated with PDT. Wounds were created two days before, one hour before, or one hour after red light exposure with an argon ion pumped dye laser. Twelve rats were injected with 0.25 mg/kg or 0.5 mg/kg of the PDT drug, BPD-MA, and the other 12 with 5 mg/kg or 10 mg/kg of the PDT drug, CASP, 3 and 24 hours prior to irradiation of light, respectively. At low doses of both photosensitizers, animals were irradiated with 1, 5, 10, and 20 J/cm2. At higher doses of BPD-MA and CASP animals were treated with 10, 20, 50, and 100 J/cm2 of light. Wounds were examined each day for 14 days and noted for edema, erythema, inflammation, necrosis, and quality of scarring. Wounds were also photographed at day 0, 2, 5, 8, and 14 post-irradiation. All animals were sacrificed 14 days after irradiation and the wounds were evaluated by light microscopy.

RESULTS

Grossly, animals treated with 0.25 mg/kg BPD-MA showed no effect with PDT. Animals treated with 0.5 mg/kg BPD, and 5 and 10 mg/kg CASP showed responses that varied with both light and drug dose. Erythema, edema, inflammation, and necrosis attributed to PDT were all observed, but there was no apparent influence of PDT on either the rate or final appearance of wound healing. Histologically, there were no apparent differences between treated and untreated sites, regardless of the drug, dose of light, or time of irradiation.

CONCLUSION

A single PDT treatment given before or after skin wounds does not apparently alter wound healing even when PDT caused brisk inflammatory reactions. PDT may have effects that were not detected. We conclude that PDT does not greatly influence incisional skin wound healing in the rat model.