Fig. 4: The Functional role of BM degradation in the lung tissue of the elderly.

a IHC analysis of human lung tissues were subjected for MMP9. Quantification data of IHC results is shown in the right panel. b IHC analysis of Type IV collagen was performed on lung tissue obtained from elderly and young subjects. High-magnification views of the original figure are represented as “1” and “2”. c The schematic image illustrates the process of water exchange in the lung. Alveolar water absorption is regulated by the uptake of Na⁺ ions through the apical SCNN1A channel and the basolateral ATP1A pump in type II alveolar cells. d IMR90 lung fibroblasts were sub-cultured to generate mid-old cells (DT 4 days). The mRNA expression of mid-old cell markers in young and mid-old IMR90 cells is shown in the left panel. Young IMR90 cells were treated with rhSAA1 for 24 h, and the mRNA expression of IL1β and MMP9 was analyzed in the right panel. e HPAEpiC were treated with rhSAA1 (100 ng/ml) for 24 h, and the expression of SFTPD, AQP3, ATP1A1, and SCNN1A was analyzed using real-time PCR. f HPAEpiC were cultured on the Matrigel-coated membrane for 2 days, and the expression levels of ATP1A1 and SCNN1A were analyzed using real-time PCR. g IHC analysis of SCNN1A in human lung tissue is shown. Arrows indicate SCNN1A-expressing cells. Quantification data of IHC results is shown in the lower panel. h IHC analysis of SCNN1A in mouse lung tissue is shown. Arrows indicate SCNN1A-positive cells. Quantification data of IHC results is shown in the left lower panel. The mRNA expression level of SCNN1A was analyzed in the mouse lung tissue is shown (right lower panel). IHC results were presented as the percentage of positive cells in the stromal or epithelial region. The p values of (a), (d–g), and (h) are obtained from the one-tailed Mann–Whitney U test. The p value of (b) is obtained using Chi-square test. The graphs in (a) and d–h) were represented as mean ± SD.