The distribution and time-dependent expression of MAGL during skeletal muscle wound healing in rats

Monoacylglycerol lipase (MAGL) is widely distributed in mammals and largely responsible for metabolizing 2-arachidonoylglycerol (2-AG). Little is known about its expression in skeletal muscles after trauma. A preliminary study on time-dependent expression and distribution of MAGL was performed by immunohistochemical staining, Western blotting and quantitative real-time PCR (qPCR) during skeletal muscle wound healing in rats. An animal model of skeletal muscle contusion was established in 40 Sprague-Dawley male rats. Samples were taken at 1, 3, 5, 7, 9, 13, 17 and 21 days after contusion, respectively (5 rats in each posttraumatic interval). 5 rats were employed as control. Weak immunoreactivity of MAGL was observed in the sarcoplasm of myofibers in control rats. Intensive immunoreactivities of MAGL were observed in polymorphonuclear cells (PMNs), round-shaped mononuclear cells (MNCs), spindle-shaped fibroblastic cells (FBCs) and regenerated multinucleated myotubes in the injured tissue. Subsequently, neutrophils, macrophages and myofibroblasts were identified as MAGL-positive cells by double immunofluorescent procedure. MAGL expression was remarkably up-regulated after contusion by qPCR and Western blot analysis. The results demonstrate that the expression of MAGL is distributed in certain cell types and time-dependently expressed in skeletal muscles after trauma, suggesting that MAGL may be involved in inflammatory response, fibrogenesis and muscle regeneration during skeletal muscle wound healing.