Efeito do laser As-Ga-AI de baixa potência sobre o músculo gastrocnêmio de rato submetido à lesão mecânica

Abstract

The muscle is a biological tissue that possesses plasticity, and presents a high degree of remodeling facing several stimulations. It is also frequently affected by normal-life and sports-related traumas. In this manner, this tissue’s fast recovery, maintaining its mechanic properties is of extreme importance to the individual. Several studies indicate the laser’s efficiency regarding the modulation of the inflammatory response in skin, tendon, muscle and bone tissues. The objective of this work was to evaluate the effects the As-Ga-Al laser radiation has regarding the reparation of the gastrocnemius muscle of rats after a mechanic trauma. Forty-eight rats from the Wistar lineage were utilized, from which half were sacrificed at eight days and the remaining half at 15 days from the beginning of the experiment. The animals were separated into the following groups, each containing eight animals each: two control groups, two only lesioned groups and two lesioned and treated groups. The gastrocnemius muscles of the lesioned group animals were submitted to a trauma, through an impact caused by a mechanic trauma-inducing device. The lesioned and treated group animals received laser irradiation with 10 J/cm² at day 1, 3, 5, and 7 following the lesioning. The lesioned group animals were not irradiated, but submitted to the same procedures, only with the As-Ga-Al laser device turned off. At the day of the sacrifice, the animals were given anesthetics (Rompum® and Ketalar®) using a dosage of 0,10 mL/100g of bodily mass, and were then decapitated. The gastrocnemius muscles were retrieved, fixated in formaldehyde at 10%, processed, included in paraffin, sectioned and colored with hematoxillin/eosin. Some of the slides were colored with picrosirius red and fast green in order to observe the collagen. There were no alterations in the inflammatory process regarding the number of polymorph nuclear cells, fibroblasts, macrophages and monocytes, in comparison to the control groups. The histomorphometric assessment analysis demonstrated an improvement in the collagen tissue distribution in the lesioned and treated groups and a decrease in collagen levels in the lesioned and treated groups that suffered sacrifice at 15 days. Thus, laser therapy in the models utilized in this experiment may be useful in the treatment of muscular lesions, for it promotes a decrease in collagen during the latest stage of tissue reparation, therefore inducing a more adequate rearranging of this tissue. This therapeutic resource prevents the excess of collagen and also muscular retractions, making way for a more adequate and precocious recovery of muscular activity.