Fig. 6. TrkB is a marker of activated capillary ECs in response to bleomycin challenge.

A t-SNE displaying different capillary EC subpopulations in sham (Blue, n = 1346 cells), injured lungs after 14 days (B14D, Red, n = 1067 cells), and injured lungs after 35 days (B35D, Orange, n = 1399 cells) post bleomycin-induced lung injury. B, C t-SNE and violin plots showing that the expression of Ntrk2 gene is enriched in capillary ECs at 14 days after injury and returned to baseline at day 35 post bleomycin challenge. Sham (n = 1346 cells), B14D (n = 1067 cells), B35D (n = 1399 cells). D, E t-SNE and violin plots showing the expression of EGFP gene following injury. gCap ECs (sham (n = 964 cells), B14D (n = 800 cells), B35D (n = 1002 cells)) aCap ECs (sham (n = 382 cells), B14D (n = 267 cells), B35D (n = 397 cells)). F Immunofluorescence staining using antibodies against GFP and CAR4 in young lungs of uninjured sham and 28 days after bleomycin injury. G Quantification of immunofluorescence staining at 28 days after bleomycin injury showing the retention of EGFP expression by gCap ECs at different time points and the absence of EGFP expression in aCap ECs (n = 3). Values are summarized as mean ± SEM, P values were generated using one-way ANOVA with Tukey’s post hoc test for comparison. H Immunofluorescence images showing the expression of TrkB in gCap ECs after bleomycin challenge. gCap ECs were lineage labeled in Aplnr-CreER(T)-mTmG mice 15 days prior to bleomycin administration (Day 0). Sham and bleomycin-injured lungs were harvested 28 days post bleomycin delivery followed by immunofluorescence analysis. An antibody against TrkB was used to detect injured gCap ECs (Red). gCap ECs co-expressing EGFP and TrkB (yellow) only emerged in injured lungs. Each box plot displays the median value as the center line, the upper and lower box boundaries at the first and third quartiles (25th and 75th percentiles), and the whiskers depict the minimum and maximum values. Source data are provided as a Source Data file.