Int J Biol Sci 2011; 7(5):588-599. doi:10.7150/ijbs.7.588

Research Paper

Alveolar Type II Cells Escape Stress Failure Caused by Tonic Stretch through Transient Focal Adhesion Disassembly

Xiao-Yang Liu1,2, Xiao-Fei Chen3, Yan-Hong Ren1,2, Qing-Yuan Zhan1,2, Chen Wang1,2 ✉, Chun Yang3 ✉

1. Beijing Chao-Yang Hospital, Capital Medical University, China
2. Beijing Institute of Respiratory Medicine, China
3. Institute of Biomechanics and Medical Engineering, School of Aerospace, Tsinghua University, China

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Liu XY, Chen XF, Ren YH, Zhan QY, Wang C, Yang C. Alveolar Type II Cells Escape Stress Failure Caused by Tonic Stretch through Transient Focal Adhesion Disassembly. Int J Biol Sci 2011; 7(5):588-599. doi:10.7150/ijbs.7.588. Available from

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Mechanical ventilation-induced excessive stretch of alveoli is reported to induce cellular stress failure and subsequent lung injury, and is therefore an injurious factor to the lung. Avoiding cellular stress failure is crucial to ventilator-induced lung injury (VILI) treatment. In the present study, primary rat alveolar type II (ATII) cells were isolated to evaluate their viability and the mechanism of their survival under tonic stretch. By the annexin V/ PI staining and flow cytometry assay, we demonstrated that tonic stretch-induced cell death is an immediate injury of mechanical stress. In addition, immunofluorescence and immunoblots assay showed that the cells experienced an expansion-contraction-reexpansion process, accompanied by partial focal adhesion (FA) disassembly during contraction. Manipulation of integrin adherent affinity by altering bivalent cation levels in the culture medium and applying an integrin neutralizing antibody showed that facilitated adhesion affinity promoted cell death under tonic stretch, while lower level of adhesion protected the cells from stretch-induced stress failure. Finally, a simplified numerical model was established to reveal that adequate disassembly of FAs reduced the forces transmitting throughout the cell. Taken together, these results indicate that ATII cells escape stress failure caused by tonic stretch via active cell morphological remodeling, during which cells transiently disassemble FAs to unload mechanical forces.

Keywords: focal adhesion disassembly, cellular stress failure, cell morphologic remodeling, cell culture, tonic stretch