Assessment of Left Lung Remodeling with Magnetic Resonance Imaging in a Murine Model Following Exposure to Douglas Fir Smoke.

Wildland firefighters (WLFFs) experience lung function decline due to occupational exposure to fire smoke. To pinpoint the biological underpinnings of abnormal respiratory function following 3-7 years of WLFF service, we exposed mice to Douglas Fir Smoke (DFS) over 8 weeks. Following exposure, we assessed changes in lung structure through Magnetic Resonance Imaging (MRI) and histological analysis, which was supported by immunohistochemistry staining. With MRI, we assessed the signal decay time, T2*, from ultrashort echo time images and utilized this metric as a measure of airspace enlargement. T2* was found to be significantly shorter in mice exposed to DFS compared to air exposed controls. In addition, the variation in T2* was more heterogeneously distributed throughout the left lung in DFS exposed mice, compared to air controls. These observations were supported by histology, which showed destruction of the alveolar spaces likely due to inflammation, as measured by an influx of CD68+ macrophages and elevation in neutrophil elastase. In addition, measurements of airspace dimensions from histology were more heterogeneously distributed throughout the lung, corroborating the MRI data. Findings from this study suggest that decline in lung function observed in WLFFs may be due to emphysema-like changes of the lung.