Abstract. Introduction. Skeletal muscle wasting is an important clinical issue following acute traumatic injury, and can delay recovery and cause permanent functional disability particularly in the elderly. However, the fundamental mechanisms involved in trauma-induced muscle wasting remain poorly defined and therapeutic interventions are limited. Objectives. To characterise local and systemic mediators of skeletal muscle wasting in elderly patients following acute trauma. Methods. Experiments were approved by a local NHS Research Ethics Committee and all participants provided written informed consent. Vastus lateralis biopsies and serum samples were taken from human male and female patients shortly after acute trauma injury in lower limbs (n=6; mean age 78.7±4.4 y) and compared to age-matched controls (n=6; mean age 72.6±6.3 y). Atrogenes and upstream regulators (MuRF1; MAFbx; IL6, TNFα, PGC-1α) mRNA expression was assessed in muscle samples via RT-qPCR. Serum profiling of inflammatory markers (e.g. IL6, TNFα, IL1β) was further performed via multiplex assays. To determine whether systemic factors induced by trauma directly affect muscle phenotype, differentiated primary human myotubes were treated in vitro with serum from controls or trauma patients (pooled; n=3 each) in the final 24 hours of differentiation. Cells were then fixed, stained for myogenin and imaged to determine minimum ferret diameter. Statistical significance was determined at P<0.05. Results. There was an increase in skeletal muscle mRNA expression for E3 ligase MAFbx and inflammatory cytokine IL-6 (4.6 and 21.5-fold respectively; P<0.05) in trauma patients compared to controls. Expression of myogenic determination factor MyoD and regulator of mitochondrial biogenesis PGC-1α was lower in
Pulsed Electromagnetic Fields (PEMFs) promote joint tissue anabolic activities, particularly in cartilage and bone. Here we investigated the effect of selected PEMFs (75Hz, 1.5mT, 1.3msec) in a differentiating model of murine myoblasts (C2C12) in vitro. C2C12 were seeded at 5×10. 3. cells/cm. 2. in 4 well plates and left to adhere for 24h. Subsequently, cells were either maintained in growth medium (GM) or induced towards myogenic differentiation in low-serum conditions, with and without PEMF exposure, for 4 days. Morphological analysis, myotube formation and fusion index (FI) were assessed with fluorescence microscopy techniques. Metabolic activity was determined by MTT; moreover, a multiplex cytokine array (RayBiotech) allowed cell supernatant molecule quantification. Cells exposed to PEMFs in GM acquired a distinctive elongated morphology, with increased bi-nuclear figures (3.2-fold FI increase over PEMF-unexposed cells) and displayed a significantly higher metabolic activity (+31%, p<0.05 over PEMF-unexposed cells). PEMF exposure increased metabolic activity also under myogenic differentiation (+15% over PEMF-unexposed differentiating cells, p<0.05), with the formation of long, thick polynuclear myotubes, suggesting a role of PEMFs in enhancing myogenesis (7.7-fold FI increase over PEMF-unexposed cells). 4-day culture supernatants revealed the presence of several myokines (KC/CXCL1, LIX, MCP-1, TIMP-1). Preliminary analysis showed a 1.16-fold increase (n=2) of LIX and, notably, a 1.91-fold increase (n=2) of TNF-RI, in cell supernatants of PEMF-exposed over PEMF-unexposed cells. Collectively, these results suggest that PEMF may successfully be applied in models of
The nervous system is known to be involved in inflammation and repair. We aimed to determine the effect of physical activity on the healing of a muscle injury and to examine the pattern of innervation. Using a drop-ball technique, a contusion was produced in the gastrocnemius in 20 rats. In ten the limb was immobilised in a plaster cast and the remaining ten had mobilisation on a running wheel. The muscle and the corresponding dorsal-root ganglia were studied by histological and immunohistochemical methods. In the mobilisation group, there was a significant reduction in lymphocytes (p = 0.016), macrophages (p = 0.008) and myotubules (p = 0.008) between three and 21 days. The formation of myotubules and the density of nerve fibres was significantly higher (both p = 0.016) compared with those in the immobilisation group at three days, while the density of CGRP-positive fibres was significantly lower (p = 0.016) after 21 days. Mobilisation after contusional injury to the muscle resulted in early and increased formation of myotubules, early nerve regeneration and progressive reduction in inflammation, suggesting that it promoted a better healing response.
Our aim was to compare the biomechanical properties of suturing methods to determine a better method for the repair of lacerated skeletal muscle. We tested Kessler stitches and the combination of Mason-Allen and perimeter stitches. Individual stitches were placed in the muscle belly of quadriceps femoris from a pig cadaver and were tensioned mechanically. The maximum loads and strains were measured and failure modes recorded. The mean load and strain for the Kessler stitches were significantly less than those for combination stitches. All five Kessler stitches tore out longitudinally from the muscle. All five combination stitches did not fail but successfully elongated. Our study has shown that the better method of repair for suturing muscle is the use of combination stitches.
