(A) Immunofluorescence images of endobronchial biopsies stained for DNA (Syto83, green), vimentin (purple), CD45 (blue), and α-SMA (yellow) showing the selected ROIs (boxed regions). Scale bars: 100 μm. (B) Pathway enrichment analysis in endothelial cell–rich regions of children with asthma and controls. n = 4–9 ROIs per group from 2 controls and 2 with asthma. P values in Supplemental Table 4. (C–F and I–K) Human MCs were sensitized overnight with anti-DNP IgE, then placed on pericytes and stimulated with an increasing concentration of DNP-BSA for 24 hours; (I–K) APC366 (tryptase inhibitor) or vehicle control was added at the time of stimulation. (C) Degranulated MC number normalized to the total number of MCs. n = 3 MC donors from 3 independent experiments. (D) Pericyte number. n = 3 pericyte donors from 3 independent experiments. (E) Pericyte volume. n = 3 pericyte donors from 3 independent experiments. (F) Avidin signal on small pericytes (<500 μm³) and large pericytes (>9,000 μm³). n = 3 pericyte donors from 3 independent experiments. (G) Flow cytometry profiles of degranulated MCs and unsupervised analysis of extracellular MC granules. t-SNE analysis performed on 3 pooled donors. Representative of 2 independent experiments. (H) Frequency of avidin⁺ granules positive for indicated markers. n = 3 MC donors from 2 independent experiments. (I) Images of pericyte/MC coculture stained for DAPI (yellow), F-actin (green), and MC granules (avidin, blue). Scale bars: 50 μm. Representative of 3 independent experiments. (J) Degranulated MC numbers normalized to the total number of MCs. n = 5 MC donors from 3 independent experiments. (K) Pericyte volume. n = 6 pericyte donors from 3 independent experiments. Data are represented as means ± SEM. *P < 0.05; **P < 0.01;***P < 0.001, 2-tailed Mann-Whitney test (B); 1-way ANOVA followed by Tukey’s post hoc test (C–E); 2-tailed Student’s t test (F); 2-way ANOVA followed by Šidák’s post hoc test (J and K).