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
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.


CONCLUSIONS
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.
Pinheiro
Antonio Luiz B
AL
Laser Center, School of Dentistry, Federal University of Bahia (UFBA), Bahia, Brazil. albq@ufba.br
Pozza
Daniel Humberto
DH
Oliveira
Marilia G de
MG
Weissmann
Ruben
R
Ramalho
Luciana Maria Pedreira
LM
D000818:Animals; D001707:Biopsy, Needle; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D007834:Lasers; D028022:Low-Level Light Therapy / Q000379:methods*; D008297:Male; D010784:Photomicrography; D011336:Probability; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D012680:Sensitivity and Specificity; D014945:Wound Healing / Q000502:physiology*; D014947:Wounds and Injuries / Q000473:pathology* / Q000532:radiotherapy*