Low-Level Laser Therapy for Protection Against Skeletal Muscle Damage After Ischemia-Reperfusion Injury in Rat Hindlimbs

Background and Objective: Despite numerous hypotheses regarding the action of laser light, the use of low-level laser therapy (LLLT) in ischemic reperfusion (I/R) injury is still being verified. The present study investigates the effects of low-level laser irradiation (LLLI) on I/R injury of the musculus gracilis in rats. Materials and Methods: I/R injury of the musculus gracilis flap was induced in male adult Sprague-Dawley rats (n = 84). Rats were subdivided depending on treatment into four subgroups: (1) healthy group, (2) I/R injury without irradiation, (3) R group irradiated only during reperfusion after injury, and (4) IR group irradiated during ischemia and reperfusion injury. LLLT (AlGaInP; lambda = 670 nm; 4 J/cm(2); 40 mW/cm(2)) was applied to the injured muscle four times daily until euthanasia. Results: Lactate dehydrogenase (LD) levels were significantly lower (P<0.05) in the irradiated groups during the first 12-120 hours, while the lower creatine kinase (CK) level reached statistical significance only at 24 hours in the irradiated group when compared to the control group. The number of polymorphonuclear leukocytes in the gracilis muscle was significantly lower in the treated group only on the second day (P<0.0001). The lowered percentage of necrosis in the muscle tissue was statistically significant after 6 and 10 days of treatment (P<0.0001), while lower atrophy and higher neovascularization were observed at 614 days of irradiation (P<0.05). There was no statistically significant difference between the group irradiated only during reperfusion and that irradiated during ischemia and reperfusion. Conclusion: LLLT confers a protective effect against early inflammatory tissue response, further atrophy, and necrosis of the muscle and it stimulates neovascularization after I/R injury. Lasers Surg. Med. 42:665-672, 2010. (C) 2010 Wiley-Liss, Inc.