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

Abstract

Objective: This study aimed to describe, through morphologic and cytochemical analysis, the healing process of wounds submitted (or not) to laser therapy (λ685 nm) or polarized light (λ400-2000 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 α-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 reepithelialization 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.

Effect of polarization and coherence of low-intensity optical radiation on fish embryos

“…The results obtained correspond to data suggesting a pronounced therapeutic effect from broadband polarized light [18][19][20][21][22][23][24][25][26][27][28][29]. For comparison, we note that according to [53], for simultaneous dichromatic irradiation of a cell culture under in vitro conditions by quasi-monochromatic unpolarized red light (individually having a pronounced stimulating effect) and broadband unpolarized visible light, the stimulation effect decreases or generally disappears.…”

Effects of low intensity laser irradiation during healing of skin lesions in the rat

“…However, the change in wound bioburden was not associated with improved healing as assessed by histologic parameters. In a study (685 nm light, 20 and 40 J/cm 2 ) showing accelerated healing according to histochemical parameters, wound closure rate was not reported [19]. In diabetic rats He-Ne light (4 J/cm 2 ) improved wound healing according to wound closure and histologic parameters; however, bacterial growth in wounds was not examined [20].…”

Low-Level Laser Therapy is More Effective Than Pulse Ultrasound Treatment on Wound Healing: Comperative Experimental Study

“…10 Du ring the last 40 ye ars, its ef fi cacy in wo und re pa ir was in ves ti ga ted and sup por ted with many ani mal [13][14][15][16][17] and hu man stu di es. 20,21 Today, in many co un tri es ex cept Uni ted Sta tes, LLLT is wi dely used for the tre at ment of a va ri ety con diti ons inc lu ding ne u ro lo gic, den tal and der ma to logic di sor ders.…”

“…12 Alt ho ugh se ve ral stu di es ha ve in ves ti ga ted its the ra pe u tic bene fit on pres su re ul cers, the cli ni cal use of LLLT for wo und he a ling is still un der in ves ti ga ti on be ca u se many in ves ti ga tors re port conf lic ting fin dings in ani mal and hu man stu di es. [13][14][15][16][17][18][19][20][21] In the pre sent li te ra tu re, the com pa ra ti ve data of both tre at ment mo da li ti es con cer ning wo und he a ling is very li mi ted. 22 Mo re o ver, to the best of our know led ge, the re is no da ta that com pa re the two tre at ment mo da li ti es in ex ci si o nal wo und hea ling in terms of both his to pat ho lo gic and bi oc hemi cal chan ges.…”