Fig. 4: Changes in putative SARS-CoV-2 target cell types during monkey lung aging.

a UMAP plot showing the ACE2⁺ cells in monkey lung. b UMAP plot showing the different ACE2⁺ cell types in monkey lung. EC, endothelial cell; Mes, mesenchymal cells (ciliated cells, fibroblasts, pericytes); CC, ciliated cell; IC, immune cell. c Bar plot showing the proportions of different ACE2⁺ cell types in monkey lung. The epithelial cells (AT1, AT2 and CC) are highlighted by dash lines. d Bar plots showing the proportions of ACE2⁺ cells (left) and ACE2 and TMPRSS2 double-positive cells (right) across different cell types in monkey lung. The asterisk denotes the cell type with the highest percentage of ACE2⁺ and ACE2 and TMPRSS2 double-positive cells, respectively. e Top left, pie plot showing the percentages of cells expressing genes associated with SARS-CoV-2 entry in ACE2⁺ cells of monkey lung. Top right, bar plot showing the percentages and numbers of cells expressing the indicated genes related to SARS-CoV-2 entry. Bottom, a table showing the percentages and numbers of cells expressing other membrane-bound proteases in ACE2⁺ cells. Only the five genes with the highest relative expression proportion are shown. f Box plots showing the proportion of ACE2⁺ cells and violin plot showing ACE2 expression level in young and old AT1 cells. g Top, transverse sections of lung tissues from young and old monkeys were subjected to ISH with ACE2 riboprobes. Representative ISH images are shown on the left; quantitative data are shown as means ± SEM on the right. Young, n = 8; old, n = 7 monkeys. *P < 0.05. Scale bar, 25 μm. Monkey small intestine section with ACE2 riboprobes was used as positive control, and small intestine sections with ACE2 reverse complementary riboprobes were used as negative control. The blue-purple signals were considered as ACE2-positive cells. h Immunofluorescence staining of ACE2 in young and old lung tissues from monkeys and humans, respectively. Quantitative data are shown as means ± SEM. Immunofluorescence staining of IgG and ACE2 in monkey small intestine and testis sections were used as negative and positive controls, respectively. Monkey, young, n = 8; old, n = 7 individuals. Human, young, n = 5; old, n = 10 individuals. Scale bars, 50 μm and 5 μm (zoomed-in image). *P < 0.05. i Heatmap showing DEGs across different cell types in ACE2⁺ cells of monkey lung. j Violin plots showing the expression levels of NFKB1 and DPP4 in ACE2⁺ AT2 across young and old groups.