Mechanical ventilation is the most widely used therapy in intensive care units and the cornerstone treatment for patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) 1. Although essential for successful management of respiratory failure, mechanical ventilation can also exacerbate or even directly injure the lungs 2, 3. This damage, commonly referred to as ventilator-induced lung injury (VILI), is characterised by increased permeability of the alveolar epithelium to fluids and macromolecules 4. Mechanisms leading to such increase include direct mechanical damage caused by excessive stretch of the lungs (barotrauma and volutrauma) or by repetitive opening and closing of recruitable alveolar units (atelectrauma) 3. In addition, mechanical stretch alone can trigger mechanotransduction pathways that may lead to local 5 and systemic inflammatory responses (biotrauma) 6.
To understand each of these mechanisms and their relative contribution to the pathogenesis of VILI, several in vitro strategies have been adopted. One of these strategies is to subject cells cultured on deformable substrates to stretch patterns mimicking those experienced by lung cells during mechanical ventilation 7–9. This approach has provided a wealth of knowledge regarding the biological consequences of overstretching lung cells. It is well known, for instance, that large stretches induce: apoptosis, the release of inflammatory cytokines, structural changes in tight junctions, and plasma membrane breaks 3, 8–10. A major drawback of in vitro stretch systems, however, is that the final readout is generally limited to biochemical markers. Stretch-induced synthesis, secretion and (de)phosphorylation of proteins as well as levels of mRNA production have become routinely available, but a quantitative analysis of microstructural changes in the epithelium and their influence on epithelial permeability has remained virtually inaccessible.
To overcome this limitation, Cavanaugh et al. 11 recently developed a technique …