Low-level laser irradiation, cyclooxygenase-2 (COX-2) expression and necrosis of random skin flaps in rats

Abstract

Skin flaps are still a matter of concern among surgeons, as failures can occur leading to flap necrosis. However, low-level laser irradiation has been reported as an effective tool to improve the viability of ischemic flaps, yet its mechanisms of action remain unclear. We investigated the effect of low-level laser irradiation on the viability of random skin flaps in rats and determined COX-2 expression in the flap pedicle. The study animals comprised 24 EPM-1 Wistar rats which were randomly allocated into three equal groups. A cranially based dorsal random skin flap measuring 10 × 4cm was created in all the animals. In one group, laser irradiation was simulated (sham group), and in the other two groups the animals were irradiated at 12 points with 0.29J at 20mW (energy density 10.36J/cm(2), irradiance 0.71W/cm(2)), or with 7.3J at 100mW (energy density 260.7J/cm(2), irradiance 3.57W/cm(2)). These procedures were applied to the cranial half of the flap immediately after surgery and were repeated on days 2 and 5 after surgery. The percentage necrotic area was determined on day 7 after surgery by the paper template method. The immunohistochemical expression of COX-2 in the samples was given scores from 0 to 3. The necrotic area was smaller in group irradiated at 7.3J compared to sham-treated group and to the group irradiated at 0.29J (P < 0.05); there was no difference between the sham-treated group and group irradiated at 0.29J. COX-2 expression was lower in the group irradiated at 7.3J than in the sham-treated group and the group irradiated at 0.29J (P < 0.001). Low-level laser therapy was effective in decreasing random skin flap necrosis in rats using a laser energy of 7.30J per point. Laser irradiation also decreased the expression of COX-2 in the flap pedicle.