Fig. 3: Age-associated changes in alveolar microenvironment.

A Log-normalized expression of surfactant genes in young versus aged. B Cell-type proportions as a fraction of total epithelial cell counts in young versus aged. Samples with fewer than 5 AT1 cells are excluded. C UMAP representation of AT2 cells, revealing SPCˡᵒʷand SPCʰⁱᵍʰ subpopulations. D Expression levels of AT2 marker SFTPC and SPCʰⁱᵍʰ marker HHIP. E Proportion of total AT2 cells that are SPCˡᵒʷ in young versus aged. Samples with less than 5 AT1 cells were excluded (n = 29, 20Y/9A). F Proportion of cells expressing HHIP in SPCˡᵒʷ vs SPCʰⁱᵍʰ subpopulations based on scRNAseq data (n = 59, 30 high/29 low). G Representative immunohistochemistry images for dual SPC/HHIP staining. The left panel is a young subject, and the right panel is an aged subject. SPC was stained with DAB (brown), and HHIP was stained with AP Red (pink). Red arrowheads indicate SPC-positive cells and blue arrowheads indicate dual-positive, co-stained cells. H The proportion of dual-positive cells among SPC-positive cells in young versus aged subjects (n = 12, 6Y/6A). Source data are provided as a Source Data file.