MicroRNA-155 Reduces Ventilator Induced Injury in Lung Epithelial Cells
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Date
2019-05
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The Ohio State University
Abstract
Acute respiratory distress syndrome (ARDS) can be caused by a multitude of inciting events including trauma, sepsis, or pneumonia. During this condition, the bifurcating airways become occluded with fluid due to disruption of the alveolar-capillary barrier [1]. Mechanical ventilation is the necessary treatment for this condition, but the mechanical forces of ventilation have been shown to further exacerbate pre-existing lung injury, as well as activate pro-inflammatory signaling. Further injury due to ventilation is known as ventilator-induced lung injury (VILI) [2]. VILI consists of barotrauma, volutrauma, and atelectrauma. Specifically, atelectrauma is due to microbubble flow in the airway caused by the cyclic closure and reopening of the small airways. Microbubble flow can further disrupt the blood-oxygen barrier at the capillary walls due to shear forces. Recent clinical trials have focused on optimizing the ventilation forces to reduce injury. Although many therapies have been explored, the cell response to these forces has not been fully explored as a therapeutic target. When subject to mechanical forces, cells respond internally through the mechanotransduction pathway which can cause various downstream changes to the cell. The regulation of microRNA levels is one of the downstream changes that has been observed. MicroRNAs are small non-coding RNAs that regulate gene-expression, and several microRNAs have been shown to be associated with the lung epithelial cell response to injurious forces during mechanical ventilation including microRNA 155. To model VILI in-vitro, A549 lung epithelial cells were cultured in a flow chamber, which was used to subject the cells to micro-bubble flow. The main advantage of this in-vitro model is that it can replicate the complex mechanical forces exerted on lung epithelial cells during atelectrauma. To test the effect of microRNA expression on cell death, microRNA 155 was overexpressed in the A549 lung epithelial cells using transfection techniques. Pre-miR-155 transfected cells, as well as cells transfected with a scramble microRNA (negative control) and non-transfected A549s (control) were cultured on separate 40mm slides until confluence was reached (>90%). Using these conditions, several experiments were carried out to test the effect of microRNA 155 overexpression on lung epithelial cells during ventilator conditions. Using a live-cell microscope, images of the cells were taken before and after to characterize detachment and cell death. The live/dead and detachment results from the control, scramble transfected, and 155 transfected cells were quantitatively compared. After exposure to five microbubbles the percent detachment did not differ significantly across the test conditions. The percent death did show a difference, with the microRNA 155 transfected samples showing significantly less death than the scramble and control samples. Based on the results of this experiment, microRNA 155 is shown to have a role in protecting A549 cells from bubble-induced stresses. These conditions have been shown to mimic the complex forces that have been observed in ventilator induced lung injury, meaning that microRNA-155 overexpression in lung cells may potentially have clinical significance. Future experiments will work to further characterize the role of miR-155 in lung epithelial cells using devices which more accurately model the in-vivo air-lung interface.
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MicroRNA-155 Reduces Ventilator Induced Lung Injury