The modulation of
collagen fibers during experimental skin wound healing was studied in 112 Wistar rats submitted to
laser photobiomodulation treatment. A standardized 8mm-diameter
wound was made on the dorsal skin of all animals. In half of them, 0.2ml 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 9mW applied every other day (total dose=4J/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. The observation of Sirius-red stained slides under polarized microscopy revealed to be of great help during the morphological analysis of the
collagen tissue dynamic changes. It was demonstrated that
laser application was responsible for
edema regression and a diminution in the number of inflammatory cells (p<0.05). An evident increase in the number of actin-positive cells was observed in the
laser-treated
wounds.
Collagen deposition was less than expected in
silica-treated
wounds, and
laser treatment contributed to its better differentiation and modulation in all irradiated groups. Thus,
laser photobiomodulation was able to induce several modifications during the cutaneous healing process, especially in favoring newly-formed
collagen fibers to be better organized and compactedly disposed.