Effects The Cyclic Mechanical Strain On The Prolifferation Of Human Lung Adenocarcinona Cells Line A549

The lung is a dynamic organ subjected to varying mechanical forces throughout life. These mechanical forces affect many respects of lung metabolism, function and growth. That is they have effects on the lung cells proliferation, differentiation, apoptosis, surfactant secretion, extracellular matrix synthesis and inflammatory reaction. Many researches have been done to study the biologic effects of physical forces on pulmonary epithelial cells. However, few were reported about the effects of cyclic mechanical strain with varying waveforms and duration on the pulmonary epithelial cells proliferation. To better understand the role of physical forces in the lung growth and development, radial and circumferential strain was applied using a computer-drivenFlexercell 4000 strain unit in which human lung adenocarcinoma cells line A549 were exposed to cyclic stretch of varying waveforms and duration. The cell numbers were measured by the Image-Pro software. The cells proliferation was expressed as cellular Proliferation Rate.The cellular Proliferation Rate reduced significantly (p<0.05) in square wave group compared with control group after A549 cells were subjected to 15% elongation at frequency 30 cycles/min for 2 hours. In varying strain duration experiments, A549 cells were subjected to 15% elongation at frequency 30 cycles/min for 1 hours, 2.5h and 4h respectively with square wave form. The cellular Proliferation Rate reduced when the durations were elongated (p<0.05). (3) In order to testify the accuracy of the Image-Pro-Plus software in counting the cell numbers, flow cytometry was used to measure the cell proliferation from DNA level. A549 cells were subjected to 15% elongation at frequency 30 cycles/min for 2 hours with square wave form. in the loding group cell Proliferation Index reduced significantly compared with the control one (p<0.05).Our results indicate that square waveform can inhabit theproliferation of A549 cells probably for the strain rate of the square waveform is faster, and the duration of the maximal amplitude are longer than the others. Elongation of strain duration has inhibitive effects on the proliferation of A549 cells. For the human lung adenocarcinoma cells A549 have many features consistent with alveolar type II epithelial cells, we may speculate that cyclic mechanic strain with varying waveform and elongation of strain duration will be infavorable to the repair of alveolar epithelial cells injury.