Human nasal polyps from non-CF and AF 508 homozygous CF patients were used to compare the expression of CFTR and markers of epithelial differentiation, such as cytokeratins (CK) and desmoplakins (DP), at the transcriptional and translational levels. mRNA expression was assessed by semiquantitative RT/PCR kinetic assays while the expression and distribution of proteins were evaluated by immunofluorescence analysis. In parallel, for each nasal tissue specimen, the importance of surface epithelium remodeling and inflammation was estimated after histological observations. Our results show that the steady-state levels of CFTR, CK13, CK18, CK14, or DP 1 mRNA transcripts in AF 508 CF nasal polyps were not significantly different from those of non-CF tissues. A variability in the CFTR mRNA transcript level and in the pattern of CFTR immunolabeling has been observed between the different tissue samples. However, no relationship was found between the level of CFTR mRNA transcripts and the CFTR protein expression and distribution, either in the non-CF or in the CF group. The histological observations of non-CF and CF nasal polyp tissue indicated that the huge variations in the expression and distribution of the CFTR protein were associated with the variations in the degree of surface epithelium remodeling and inflammation in the lamina propria. A surface epithelium, showing a slight basal cell hyperplasia phenotype associated with diffuse inflammation, was mainly characterized by a CFTR protein distribution at the apex of ciliated cells in both non-CF and CF specimens. In contrast, in a remodeled surface epithelium associated with severe inflammation, CFTR protein presented either a diffuse distribution in the cytoplasm of ciliated cells, or was absent. These results suggest that abnormal expression and distribution of the CFTR protein in CF airways is not only caused by CFTR mutations. Airway surface epithelium remodeling and inflammation could play a critical role in the posttranscriptional and/ or the posttranslational regulation of the CFIR protein expression in non-CF and CF airways. (J. Clin. Invest. 1995Invest. . 95:1601Invest. -1611

In cystic fibrosis (CF), whether cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction leads to decreased mucociliary clearance and mucus hypersecretion, before bacterial infection, remains an open question. To answer this question, we quantified in a blind trial the mucociliary transport velocity, the histological state, and the degree of inflammation of the tracheal mucosa in 23 cftr(m1HGU/cftr(m1HGU) transgenic mice (Dorin, J. R., P. Dickinson, E. W. F. W. Alton, S. N. Smith, D. M. Geddes, B. J. Stevenson, W. L. Kimber, S. Fleming, A. R. Clark, M. L. Hooper, L. Anderson, R. S. P. Beddington, and D. J. Porteous. Nature Lond. 359: 211-215, 1992) and in 30 control littermates housed in pathogen-free conditions. The nasal and tracheal transepithelial potential difference (PD) measured in basal conditions was significantly more negative in the cftr(m1HGU) mutant mice as compared with the control mice (nasal PD: -7.1 +/- 0.6 and -4.6 +/- 0.5 mV, respectively, P < 0.01; tracheal PD: -30.8 +/- 2.1 and -21.4 +/- 1.8 mV, respectively, P < 0.04). In the cftr(m1HGU)/cftr(m1HGU) mice, the mucociliary transport velocity was significantly lower (14.2 +/- 4.4 microm/mm, P < 0.04) compared with the control mice (30.6 +/- 5.9 microm/mm). The number of inflammatory cells in the lamina propria was significantly higher in the cftr(m1HGU)/cftr(m1HGU) mice (1048.7 +/- 124.7 cells/mm2, P < 0.03) compared with the control mice (640.5 +/- 58.2 cells/mm2). These results suggest that in CF, decreased airway mucociliary clearance and airway submucosal inflammation represent early alterations, before any airway infection.

We investigated the implication of asialo GM1 as an epithelial receptor in the increased Pseudomonas aeruginosa affinity for regenerating respiratory epithelial cells from cystic fibrosis (CF) and non-CF patients. Human respiratory epithelial cells were obtained from nasal polyps of non-CF subjects and of CF patients homozygous for the ⌬F 508 transmembrane conductance regulator protein (CFTR) mutation and cultured according to the explant-outgrowth model. At the periphery of the outgrowth, regenerating respiratory epithelial cells spreading over the collagen I matrix with lamellipodia were observed, characteristic of respiratory epithelial wound repair after injury. P. aeruginosa adherence to regenerating respiratory epithelial cells was found to be significantly greater in the ⌬F 508 homozygous CF group than in the non-CF group (P < 0.001). In vitro competitive binding inhibition assays performed with rabbit polyclonal antibody against asialo GM1 demonstrated that blocking asialo GM1 reduces P. aeruginosa adherence to regenerating respiratory epithelial cells in ⌬F 508 homozygous CF cultures (P < 0.001) as well as in non-CF cultures (P < 0.001). Blocking of asialo GM1 was significantly more efficient in CF patients than in non-CF subjects (P < 0.05). Distribution of asialo GM1 as determined by preembedding labelling and immunoelectron microscopy clearly demonstrated the specific apical membrane expression of asialo GM1 by regenerating respiratory epithelial cells, whereas other cell phenotypes did not apically express asialo GM1. These results demonstrate that (i) asialo GM1 is an apical membrane receptor for P. aeruginosa expressed at the surface of CF and non-CF regenerating respiratory epithelial cells and (ii) asialo GM1 is specifically recovered in regenerating respiratory epithelium. These results suggest that in CF, epithelial repair represents the major event which exposes asialo GM1 for P. aeruginosa adherence.

This study was designed to investigate the molecular mechanisms of Staphylococcus aureus adherence to human airway epithelium. Using a humanized bronchial xenograft model in the nude mouse and primary cultures of human airway epithelial cells (HAEC), we showed that S. aureus adhered mainly to undifferentiated HAEC whereas weak adherence (11- to 20-fold lower) to differentiated HAEC was observed (P < 0.01). A fibronectin (FN)-binding protein (FnBP)-deficient strain of S. aureus had a fivefold-lower adherence level to undifferentiated HAEC than did the parental strain (P < 0.005), suggesting that S. aureus FN-binding capacity is involved in the adherence to HAEC. We also showed that 97% of 32 S. aureus clinical strains, isolated from the airway secretions of cystic fibrosis patients (n = 18) and patients with nosocomial pneumonia (n = 14), possessed the two fnb genes. The strains from pneumonia patients had a significantly (P < 0.05) higher FN-binding capacity than did the strains from CF patients. This result was confirmed by the expression of FnBPs, investigated by Western ligand affinity blotting. Our results suggest a major role of FnBPs in the colonization of the airways by S. aureus and point to the importance of the adhesin regulatory pathways in the staphylococcal infectious process.