Article

Temporal differences in the influence of ischemic factors and deformation on the metabolism of engineered skeletal muscle

Dept. of Biomedical Engineering, Eindhoven Univ. of Technology, Eindhoven, The Netherlands.
Journal of Applied Physiology (Impact Factor: 3.06). 08/2007; 103(2):464-73. DOI: 10.1152/japplphysiol.01374.2006
Source: PubMed

ABSTRACT

Prolonged periods of tissue compression may lead to the development of pressure ulcers, some of which may originate in, for example, skeletal muscle tissue and progress underneath intact skin, representing deep tissue injury. Their etiology is multifactorial and the interaction between individual causal factors and their relative importance remain unknown. The present study addressed the relative contributions of deformation and ischemic factors to altered metabolism and viability. Engineered muscle tissue was prepared as previously detailed (14) and subjected to a combination of factors including 0% oxygen, lactic acid concentrations resulting in pH from 5.3 to 7.4, 34% compression, and low glucose levels. Deformation had an immediate effect on tissue viability {[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay}, which increased with time. By contrast, hypoxia evoked metabolic responses (glucose and lactate levels) within 24 h, but viability was only reduced after 48 h. In addition, lactic acidification downregulated tissue metabolism up to an acid concentration ( approximately 23 mM) where metabolism was arrested and cell death enhanced. A similar tissue response was observed during glucose deprivation, which, at negligible concentration, resulted in both a cessation of metabolic activity and a reduction in cell viability. The combination of results suggests that in a short-term (<24 h) deformation, extreme acidification and glucose deprivation increased the level of cell death. By contrast, nonextreme acidification and hypoxia influenced tissue metabolism, but not the development of cell death. These data provide more insight into how compression-induced factors can lead to the onset of deep tissue injury.

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Available from: Daniel L. Bader, Oct 01, 2014
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    • "These studies revealed that strains of sufficient magnitude have the potential to cause cell death over very short periods of time (Gefen et al. 2008). Gawlitta et al. (2007) considered the differences in influence of deformation and ischaemia, using tissue engineered muscle and found that deformation per se had an immediate effect, whereas hypoxia reduced cell viability over prolonged loading periods. Furthermore, animal experiments involving 2 hours of muscle compression showed that while a complete area of muscle was ischaemic, damage occurred in specific regions where high shear strain values were observed (Stekelenburg et al. 2007). "
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    • "These studies revealed that strains of sufficient magnitude have the potential to cause cell death over very short periods of time (Gefen et al. 2008). Gawlitta et al. (2007) considered the differences in influence of deformation and ischaemia, using tissue engineered muscle and found that deformation per se had an immediate effect, whereas hypoxia reduced cell viability over prolonged loading periods. Furthermore, animal experiments involving 2 hours of muscle compression showed that while a complete area of muscle was ischaemic, damage occurred in specific regions where high shear strain values were observed (Stekelenburg et al. 2007). "
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    • "Although, in our insert-based system, induction of hypoxia is somewhat slower compared with the direct addition of the enzymes (Zitta et al., 2010b), reduction of glucose concentrations and hydrogen peroxide levels are in the range of what has been reported by others working with enzyme-driven hypoxia systems (Baumann et al., 2008; Mueller et al., 2009). It should also be mentioned that the reduction of glucose concentrations throughout the experiment and the increased levels of hydrogen peroxide (compared with normoxic conditions) ideally reflect the in vivo situation of hypoxia and ischemia-reperfusion injury, in which glucose depletion and accumulation of reactive oxygen species occur and are believed to play a central role in cell death and tissue damage (Baudry et al., 2008; Gawlitta et al., 2007; Goldberg and Choi, 1993; Guo et al., 2011). Because cerebral ischemia and brain hypoxia are clinically highly relevant conditions (Robertson and Perlman, 2006), we employed the neuronal cell line IMR-32 (Tumilowicz et al., 1970) to validate the suitability of the established system for the induction of a hypoxia-mediated cell response and investigation of the associated mechanisms. "
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