(A) SC apical release in ALI-AE from Smo and COPD patients is decreased as compared with NS, from short-term ALI-AE up to long-term ALI-AE. $, £, and § highlight significant decreases in Smo, COPD1-2, and COPD3-4 patients, respectively, as compared with NS. (B) SC decreased release in the COPD AE moderately correlates with the disease severity, witnessed by the FEV1. Correlation graphs include only Smo and COPD samples to specifically assess the correlation with the disease severity. (C)
PIGR mRNA abundance is not significantly decreased in (very) severe COPD ALI-AE at separate time-points (left panel), but longitudinal analysis shows a significant decrease in PIGR expression in (very) severe COPD AE as compared with NS, Smo, and mild-to-moderate COPD (right panel). (D) pIgR acquisition is delayed during the differentiation of the AE in COPD as compared with NS, as shown in the representative blots from NS and very severe COPD ALI-AE and summarized in the middle panel. The gap was maximal at 2 wk ALI culture (right panel) and catches it up only after 4 wk. (E) TSA immunofluorescence staining for pIgR, showing reduced positive surface in situ (i.e., in bronchial sections) in the COPD AE as compared with that of NS. *, **, *** indicate P-values of less than 0.05, 0.01, and 0.001, respectively (analyzed using the Kruskal-Wallis test followed by Dunn’s post-hoc test, except for longitudinal analysis in (B, C), mixed model). Bars indicate mean ± SD (A, C [left], D [right], E), dots indicate mean (C [right], D [left]). AE, airway epithelium; ALI, air-liquid interface; COPD, chronic obstructive pulmonary disease; FEV1, forced expired volume in 1 s; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HKG, housekeeping genes; NS, non-smokers; ns, not significant; pIgR, polymeric immunoglobulin receptor; PV, predicted values; SC, secretory component; SD, standard deviation; Smo, smokers; w, weeks.