Influence of photobiomodulation upon tissue during wound healing

The modulation of collagen fibers during experimental skin wound healing was studied in 112 Wistar rats submitted to laser photobiomodulation treatment. A standardized 8 mm-diameter wound was made on the dorsal skin of all animals. In half of them, 0.2 ml of a silica suspension was injected along the border of the wound in order to enhance collagen deposition and facilitate observation. The others received saline as vehicle. The treatment was carried out by means of laser rays from an aluminum–gallium arsenide diode semiconductor with 9 mW applied every other day (total dose = 4 J/cm2) on the borders of the wound. Tissue sections obtained from four experimental groups representing sham-irradiated animals, laser, silica and the association of both, were studied after 3, 7, 10, 15, 20, 30 and 60 days from the laser application. The wounded skin area was surgically removed and submitted to histological, immunohistochemical, ultrastructural, and immunofluorescent studies. Besides the degree and arrangement of collagen fibers and of their isotypes, the degree of edema, the presence of several cell types especially pericytes and myofibroblasts, were described and measured.