Figure 4.

Decreased extracellular matrix gene transcription in aged lung mesenchymal cells. (A) Heatmaps show the expression of the extracellular matrix genes in the mesenchymal cells from subjects of different age stages. (B) The Matrix gene score (the average transcription of COL1A1, COL1A2, COL3A1, COL6A1, COL6A2, FN1, and ACTA2) and transcriptions of representative collagen genes in mesenchymal cells from subjects of different age stages are visualized by violin plots. (C) Violin plots show the transcriptions of genes specific to elastic fiber components and assembly in mesenchymal cells from subjects of different age stages. (D) Immunofluorescence staining for Collagen I, Collagen VI, α-SMA (ACTA2), and ELN (Elastin) on human lung sections from young and aged donors. Boxed regions are magnified. BV = blood vessel. Scale bars, 20 μm. (E) Quantified intensity ratios for Collagen I, Collagen VI, α-SMA, and ELN staining compared with nuclear DAPI on human lung sections from young and aged donors. (n = 4–11 sections from three subjects per group). (F) The quantification of PLIN2, TCF21, and FGF7 transcriptions and FGF10- and PPARG-positive cell percentages in total lung mesenchymal cells from donors of different age stages. (G) Visualization of FGF receptor gene, FGFR2, in AT2 cells from donors of different age stages. (H–J) Representative images (H), colony formation efficiency (CFE) (I; n = 5), and colony size (J; Young, n = 130; Aged, n = 99) of human AT2s cultured with primary fibroblasts from young and aged donors. Boxed colonies are magnified, and visible colonies are indicated by arrowheads (H). Scale bars, 500 μm (H). Purple dashed lines in the violin plots indicate the mean levels of gene transcriptions. **P < 0.01, ***P < 0.001, and ****P < 0.0001.