Equibiaxial deformation-induced injury of alveolar epithelial cells in vitro

Abstract

Deformation of the alveolar epithelial basement membrane with lung inflation has been implicated in blood-gas barrier breakdown during the development of ventilator-induced lung injury. To determine the vulnerability of alveolar epithelial cells to deformation-induced injury, we developed a cell-stretching device that subjects cells to cyclic, equibiaxial strains. Alveolar epithelial type II cells from primary culture were tested 1 and 5 days after seeding, during which time the cells underwent major morphological and phenotypic changes. Cells were subjected to changes in surface area of 12, 24, 37, and 50%, which corresponded to lung inflation of ∼60, 80, 100, and >100% of total lung capacity. Deformation-induced injury of alveolar epithelial cells, assessed with a fluorescent cell viability assay, increased with deformation magnitude and decreased with time elapsed after seeding. In cells stretched after 1 day in culture, the percentage of dead cells after a single deformation ranged from 0.5 to 72% over the range of deformations used. In cells stretched at 5 days, the percentage of dead cells ranged from 0 to 9% when exposed to identical deformation protocols. These results suggest that morphological and phenotypic changes with time in culture fundamentally change the vulnerability of alveolar epithelial cells to deformation.

Modeling the effect of stretch and plasma membrane tension on Na+-K+-ATPase activity in alveolar epithelial cells

“…For use in proof-of-concept conditioning experiments, alveolar type 2 (AT2) cells were isolated from male, Sprague-Dawley rats (Charles River, Wilmington, MA) (55) and cultured using established, previously described methods (18,19,55). AT2 cells were then seeded for confluence at 1 ϫ 10 6 cells/cm 2 .…”

“…AT2 cells were then seeded for confluence at 1 ϫ 10 6 cells/cm 2 . To determine whether lipid trafficking during static stretch has any conditioning effect on cells, 2-day cells were tonically prestretched before being stretched cyclically in a custom-made stretching device capable of imposing uniform, equibiaxial two-dimensional strain (16,55). Preconditioning was performed by stretching cells tonically for 10 min to a prescribed change in substrate surface area (⌬SA).…”

“…INVESTIGATORS HAVE FOUND alveolar epithelial stretch magnitude to be related to cell injury in vitro (55,56) and tidal volume to be related to ventilator-induced lung injury (VILI) in animal models (12)(13)(14)(15). Studies have revealed that the frequency of epithelial stretch or ventilation can also be an important factor in cell injury (56,60).…”

Sharing signals: connecting lung epithelial cells with gap junction channels

“…Also, stress analysis of alveoli suggests that type II cells, which are localized to "corners," tend to be shielded from stress forces sensed by other alveolar cells (93). Because type II cells tend to be more sensitive to mechanical trauma than type I cells (271), it might be advantageous for type I cells to have a mechanical sensor function.…”

Live Cell Imaging during Mechanical Stretch

“…In the respiratory system, one outcome of mechanotransduction is the increase in reactive oxygen species (ROS) 8,9 and pro-inflammatory cytokines 10 in pulmonary epithelial cells in the presence of cyclic tensile strain. Strong evidence also suggests that excessive tensile strain leads to direct injury to the alveolar epithelium, in addition to the biochemical responses of cells [11][12][13][14] . Although the focus here is primarily on the response of lung cells to mechanical deformation, pathways induced by mechanotransduction play a key role in the basic function of many tissues in the human body, including the regulation of vascular tone 15 and the development of the growth plate 16 .…”