Spatial analysis of young and old murine lungs exposed to ozone and fibrogenic stress [spatial_ozone]

Ozone (O3) is a ubiquitous pollutant known to produce acute and transient inflammation through oxidative injury and inflammation. These effects are exacerbated in susceptible populations, such as the elderly and those exhibiting genetic mutations in central nodes of pulmonary function. To comprehend the impact of these predisposing factors, the present study examines structural, mechanical, and immunological responses to single acute O3 exposure (0.8 ppm, 3h) in young (12 week old) and old (80 week old) mice. We therefore examined the impact of ozone in a surfactant competent and mutant murine line. The latter models a clinically relevant mutation in the gene encoding for the alveolar epithelial type 2 specific surfactant protein C. Ozone exposure produced focal injury localized at the terminal bronchiole-to-alveolar junctions and enlarged alveoli in aged SP-C mutant lungs. This histological feature was used to select regions of interest for spatial transcriptomics. Paraffin sections of 4 mice were prepared: a young/12wk SP-C wild type air control, a young/12wk SP-C wild type ozone (0.8 ppm, 3h), a young/12wk SP-C mutant ozone, and an old/80wk ozone. Immunofluorescence for DNA, CD45, CD68 was performed to identify macrophages (CD45+CD68+) and non-immune ("other", DNA+CD45-) cells within healthy (air control only), peri-injured and injured regions of the lung. A total of 24 regions (680um x 700um in size) were selected from CD68+ macrophages and CD45- non immune/"other" cells. RNA sequencing was then performed. Principal component and pathway analysis revealed spatial heterogeneity in response to ozone, as well as a senescence signature in the aging lungs. These results illustrate regional and age dependent heterogeneity in immune and non-immune cells of the lung during an acute exposure to air pollution.