Regeneration was evaluated at these times by in vivo measurement of muscle contraction forces after fast-twitch and tetanic stimulation (groups 1W, 4W, 8W; 6 per group)

Regeneration was evaluated at these times by in vivo measurement of muscle contraction forces after fast-twitch and tetanic stimulation (groups 1W, 4W, 8W; 6 per group). increased continuously, starting at 23% (SD 4) of the control side (p < 0.001) 1 week after trauma and recovering to 55% (SD 23) after 8 weeks. Fibrotic tissue occupied 40% (SD 4) of the GNF 5837 traumatized muscles after the first week, decreased to approximately 25% after 4 weeks, and remained at this value until 8 weeks. == Interpretation == At both the functional level and the morphological level, skeletal muscle regeneration follows a distinct time course. Our trauma model allows investigation of muscle regeneration after a standardized injury to muscle fibers. Injuries of skeletal muscle tissue cause deficiencies in local muscle function that can also affect bone healing (Duda et al. 2003,Schaser et al. 2003,Utvag et al. 2003,Harry et al. 2008) or the long-term success of a prosthesis (Kleemann et al 2003,Perka et al. 2005). Despite the fact that there have GNF 5837 been several experimental approaches, no methods for the treatment of the main causes of these deficienciesi.e. the loss of contractile muscle substance and the formation of fibrosishave been GNF 5837 taken into routine clinical use. One reason is that the results of putative therapies are often only described mono-dimensionally, in most cases histologically, and rarely functionally or with in vivo diagnostic methods. Animal models of muscle contusion injuries should closely mimic the clinical situation. Among them, open crush injuries allow standardized evaluation of regeneration in a selected muscle (Schultz et al. 1985,Rushton et al. 1997). For the execution of the trauma, either forceps (McGeachie and Grounds 1987,Kurek et al. 1997,Fink et al. 2003) or custom-made devices have been used (Jarvinen and Sorvari 1975,Rushton et al. 1997,Bunn et al. 2004). Previous muscle-crush models have had the disadvantage of either affecting only part of the muscle or of impairing the organ innervation and blood supply. Two types can be found in the GNF 5837 literature: the segmental crush (Schmalbruch 1976) and the complete crush, where only 46% of the muscle fibers remain intact (Fink et al. 2003). In the latter, myoneuronal junctions are damaged, which triggers not only regeneration of muscle material but also initial innervation deficits. These deficits usually lead to impaired healing (Saunders and Sissons 1953,Koishi et al. 1995,Dedkov et al. 2001,Pereira et al. 2006). Histological analysis of the regenerative process after crush injury has been done by a number of authors, describing the initial phase of inflammation followed by satellite cell activation, myotube regeneration, and Sox18 fibrosis of the muscle (Jarvinen and Sorvari 1975,Schmalbruch 1976,Sorokin et al. 2000,Bunn et al. 2004). It has been shown that this development of fibrotic tissue is one of the key factors for regenerative deficits of muscle function after trauma (Anderson et al. 1999,Nozaki et al. 2008). The development of intramuscular fibrosis over time after crush trauma has not, however, been quantitatively described. Magnetic resonance imaging (MRI) can be used in the clinical evaluation of skeletal muscle injuries. Not only are T1- and T2- weighted spin echo sequences highly sensitive for detection of edema and bleeding in anatomical relation to the structures affected (Elsayes et al. 2006), but MR scans also allow the determination of intra-individual time courses after trauma. The evaluation of muscle regeneration by contraction pressure measurements provides information about the functional outcome of therapeutic approaches (Sato et al. 2003,Negishi et al. 2005,Winkler et al. 2009). The description of a muscle trauma model should therefore not solely include morphological but also mechanical data. One aim of our study was to establish a standardized model of selective trauma of the muscle substance of a single muscle, leaving the blood and nerve supply undamaged. This was achieved by developing a global crush injury of the rat soleus muscle with respect to the topographic arrangement of the.