Compression-induced damage in a muscle cell model in vitro

Abstract

Soft tissue breakdown can be initiated at the muscle layer associated with bony prominences, leading to the development of pressure ulcers. Both the magnitude and duration of pressure are important factors in this breakdown process. The present study utilizes a physical model, incorporating C2C12 mouse myoblasts in a homogeneous agarose gel, to examine the damaging effects of prolonged applied pressure. Identical cylindrical cores cut from the agarose/cell suspension were subjected to two separate compressive strains, of 10 and 20 per cent. The strain was applied for time periods ranging from 0.5 to 12 hours, using a specially designed loading apparatus. After each compression period, sections taken from the central horizontal plane of the individual constructs were stained using either haematoxylin and eosin or with the fluorescent probes, Calcein AM and ethidium homodimer-1, and assessed for cell damage. It was found that constructs subjected to the higher strain values demonstrated significantly higher values of non-viable cells for equivalent time points compared to the unstrained constructs. Further analysis on sections using the DNA nick-translation method suggested that this increase was primarily due to apoptosis. These findings imply a relationship between the duration of applied compression and damage to muscle cells seeded in the gel, which was particularly apparent at the strain level of 20 per cent, equivalent to a clinically relevant pressure of 32 mmHg (4.3 kPa). Such an approach might be useful in establishing damage threshold levels at a cellular level.

The Relative Contributions of Compression and Hypoxia to Development of Muscle Tissue Damage: An In Vitro Study

“…13,18,20,29 A previous cell-model study examining relative values of apoptotic and necrotic cell death revealed an increase in the apoptotic percentage of total cell death from 61% to 67% (10% increase) and 71% (16% increase) after 8 and 12 h of 10% compression, respectively. 35 In the present study, the apoptotic contribution was comparable, as summarized in Table 3. Thus after 22 h the percentages had increased to approximately 25% for uncompressed samples (both normoxic and hypoxic), whereas compressed samples incorporated 40-45% of apoptotic cell death.…”

“…A few studies have utilized in vitro model systems with a controlled experimental input. 8,35 In the present study, such an in vitro model was applied to study the relative contributions of hypoxia and compression to the progression of cell death in engineered skeletal muscle tissue. Hypoxia was considered to be the most important effect of ischemia in development of tissue damage.…”

“…In related studies by the authors, muscle cells were suspended in a gel matrix and compressed while development of cell necrosis and apoptosis was monitored with time. 5,8,35 However, none of these studies incorporate the effect of oxygen deprivation.…”

Distribution of Internal Strains Around Bony Prominences in Pigs

“…Single cell studies 54,56,75 showed that under excessive compressive strains, cell membranes initially form blebs followed by complete failure and rupture. In vivo testing in rats 6 showed that after prolonged loading, loss of muscle fiber cross-striation is encountered as well as infiltration of inflammatory cells as necrosis ensues.…”

Biomechanical analysis of structural deformation in living cells

“…The model system has demonstrated that a prolonged compression period will increase the proportion of damaged muscle cells [84]. It is tempting to extrapolate this cell deformation data to the clinical setting, where tissue breakdown, in the form of pressure ulcers, may be induced within relatively short periods of continuous loading.…”