Fig. 5

MMP12 deficiency decreases PAS-positive mucus producing goblet cells following HDM exposures. Sub-chronic (60 days) exposures to JUUL menthol-flavored aerosol a–c caused peribronchial inflammation in Air + HDM WT mice and suppressed this response in JUUL + HDM WT mice (H&E-stained representative lung tissue images); d, e significantly increased the number of PAS-positive goblet cells in the lungs of Air + HDM WT mice compared to Air controls and JUUL + PBS WT mice (PAS-stained representative lung tissue images); f–h caused peribronchial inflammation in Air + HDM and JUUL + HDM MMP12 KO mice (H&E-stained representative lung tissue images); i, j did not induce any significant difference in the number of PAS-positive goblet cells in the lungs of all MMP12 KO mice. Data represent the mean ± SEM for n = 5–8 animals per group. One-way ANOVA followed by a Dunnet’s post-hoc test. *p < 0.05 and **p < 0.01 statistically different from Air control. Overall histopathology score for inflammation and PAS-positive cells: 0 = normal, 1 = minimal, 2 = mild, 3 = moderate, 4 = severe. Magnification: 20×. a, f * = Bronchial lumen. Dashed red encircled area = peribronchial inflammation. Solid yellow encircled area = interstitial inflammation. Air WT + PBS: there is none to minimal interstitial and peribronchial inflammation. Air WT + HDM: there is moderate interstitial and peribronchial inflammation. JUUL WT + PBS: there is minimal interstitial and peribronchial inflammation. JUUL WT + HDM: there is mild interstitial and peribronchial inflammation. Air KO + PBS: there is mild interstitial and minimal peribronchial inflammation. ​ Air KO + HDM: there is mild-to-moderate interstitial and peribronchial inflammation. JUUL KO + PBS: there is mild interstitial and peribronchial inflammation. JUUL KO + HDM: there is mild interstitial and moderate peribronchial inflammation. d, i * = Bronchial lumen. Purple arrows indicate PAS-positive cells (purple). Air WT + PBS: PAS-positive bronchial goblet cells are not present. Air WT + HDM: there are moderate numbers of PAS-positive bronchial goblet cells. JUUL WT + PBS: there are rare PAS-positive bronchial goblet cells. JUUL WT + HDM: there are low-to-moderate numbers of PAS-positive bronchial goblet cells. Air KO + PBS: there are rare PAS-positive bronchial goblet cells. Air KO + HDM: there are low-to-moderate numbers of PAS-positive bronchial goblet cells. JUUL KO + PBS: there are rare PAS-positive bronchial goblet cells. JUUL KO + HDM: there are moderate numbers of PAS-positive bronchial goblet cells. While the numbers of PAS-positive goblet bronchial cells appear to be similar between JUUL KO + HDM and Air KO + HDM, the intensity of PAS staining is higher in JUUL KO + HDM samples. ​​Scale bar = 50 µm