Respiratory mechanics following chronic cigarette smoke exposure in the Apoe − / − mouse model

Mapping the unicellular transcriptome of the ascending thoracic aorta to changes in mechanosensing and mechanoadaptation during aging

Aortic stiffening is an inevitable manifestation of chronological aging, yet the mechano-molecular programs that orchestrate region- and layer-specific adaptations along the length and through the wall of the aorta are incompletely defined. Here, we show that the decline in passive cyclic distensibility is more pronounced in the ascending thoracic aorta (ATA) compared to distal segments of the aorta and that collagen content increases in both the medial and adventitial compartments of the ATA during aging. The single-cell RNA sequencing of aged ATA tissues reveals altered cellular senescence, remodeling, and inflammatory responses accompanied by enrichment of T-lymphocytes and rarefaction of vascular smooth muscle cells, compared to young samples. T lymphocyte clusters accumulate in the adventitia, while the activation of mechanosensitive Piezo-1 enhances vasoconstriction and contributes to the overall functional decline of ATA tissues. These results portray the immuno-mechanical aging of the ATA as a process that culminates in a stiffer conduit permissive to the accrual of multi-gerogenic signals priming to disease development.

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. WLFFs typically do not wear respiratory personal protective equipment, and if they do, it is a simple bandana, which is not effective at filtering 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 found that the signal decay time, T2*, from ultrashort echo time (UTE) images was significantly shorter in mice exposed to DFS compared to air controls. In addition, the variation in T2* was more heterogeneously distributed throughout the left lung in DFS-exposed mice, compared to air controls. As confirmed by histological analysis, shorter T2* was caused by larger parenchyma airspace sizes and not fibrotic remodeling. Destruction of the alveolar spaces was likely due to inflammation, as measured by an influx of CD68+ macrophages and destruction due to enhanced neutrophil elastase. In addition, measurements of airspace dimensions from histology were more heterogeneously distributed throughout the lung, corroborating the enhanced relative dispersion of T2*. Findings from this study suggest that the decline in lung function observed in WLFFs may be due to emphysema-like changes in the lung, which can be quantified with MRI.