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1.  Cystic fibrosis airway secretions exhibit mucin hyperconcentration and increased osmotic pressure 
The Journal of Clinical Investigation  2014;124(7):3047-3060.
The pathogenesis of mucoinfective lung disease in cystic fibrosis (CF) patients likely involves poor mucus clearance. A recent model of mucus clearance predicts that mucus flow depends on the relative mucin concentration of the mucus layer compared with that of the periciliary layer; however, mucin concentrations have been difficult to measure in CF secretions. Here, we have shown that the concentration of mucin in CF sputum is low when measured by immunologically based techniques, and mass spectrometric analyses of CF mucins revealed mucin cleavage at antibody recognition sites. Using physical size exclusion chromatography/differential refractometry (SEC/dRI) techniques, we determined that mucin concentrations in CF secretions were higher than those in normal secretions. Measurements of partial osmotic pressures revealed that the partial osmotic pressure of CF sputum and the retained mucus in excised CF lungs were substantially greater than the partial osmotic pressure of normal secretions. Our data reveal that mucin concentration cannot be accurately measured immunologically in proteolytically active CF secretions; mucins are hyperconcentrated in CF secretions; and CF secretion osmotic pressures predict mucus layer–dependent osmotic compression of the periciliary liquid layer in CF lungs. Consequently, mucin hypersecretion likely produces mucus stasis, which contributes to key infectious and inflammatory components of CF lung disease.
PMCID: PMC4072023  PMID: 24892808
2.  Measuring health-related quality of life in chronic obstructive pulmonary disease: properties of the EQ-5D-5L and PROMIS-43 short form 
The Patient Reported Outcomes Measurement Information System 43-item short form (PROMIS-43) and the five-level EQ-5D (EQ-5D-5L) are recently developed measures of health-related quality of life (HRQL) that have potentially broad application in evaluating treatments and capturing burden of respiratory-related diseases. The aims of this study were: (1) to examine their psychometric properties in patients with chronic obstructive pulmonary disease (COPD), and (2) to identify dimensions of HRQL that differ and do not differ by lung function.
We conducted a multi-center, cross-sectional study (“COPD Outcomes-based Network for Clinical Effectiveness & Research Translation” [CONCERT]). We analyzed patients who met spirometric criteria for COPD, and completed EQ-5D-5L and PROMIS questionnaires. Disease severity was graded based on the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification. Pulmonary function test, PROMIS-43, EQ-5D (index score and EQ-Visual Analog Scale [EQ-VAS]), six minute walk test (6MWT), and three dyspnea scales (mMRC, Borg, FACIT-Dyspnea) were administered. Validity and reliability of EQ-5D-5L and PROMIS-43 were examined, and differences in HRQL by GOLD grade were assessed.
Data from 670 patients with COPD were analyzed (mean age 68.5 years; 58% male). More severe COPD was associated with more problems with mobility, self-care and usual activities (all p-values <0.01) according to EQ-5D-5L. Related domains on EQ-5D-5L, PROMIS and clinical measures were moderately (r = 0.30-0.49) to strongly (r ≥ 0.50) correlated. A statistically significant trend of decreasing HRQL with more severe lung functions was observed for EQ-5D-5L index scores, EQ-VAS scores, and PROMIS physical function and social roles.
Results supported the validity of EQ-5D-5L and PROMIS-43 in COPD patients, and indicate that physical function and social activities decrease with level of lung function by GOLD grade, but not pain, mental health, sleep or fatigue as reported by patients.
PMCID: PMC4072614  PMID: 24934150
COPD; EQ-5D-5L; PROMIS; Psychometric properties
3.  A Biophysical Basis for Mucus Solids Concentration as a Candidate Biomarker for Airways Disease 
PLoS ONE  2014;9(2):e87681.
In human airways diseases, including cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD), host defense is compromised and airways inflammation and infection often result. Mucus clearance and trapping of inhaled pathogens constitute key elements of host defense. Clearance rates are governed by mucus viscous and elastic moduli at physiological driving frequencies, whereas transport of trapped pathogens in mucus layers is governed by diffusivity. There is a clear need for simple and effective clinical biomarkers of airways disease that correlate with these properties. We tested the hypothesis that mucus solids concentration, indexed as weight percent solids (wt%), is such a biomarker. Passive microbead rheology was employed to determine both diffusive and viscoelastic properties of mucus harvested from human bronchial epithelial (HBE) cultures. Guided by sputum from healthy (1.5–2.5 wt%) and diseased (COPD, CF; 5 wt%) subjects, mucus samples were generated in vitro to mimic in vivo physiology, including intermediate range wt% to represent disease progression. Analyses of microbead datasets showed mucus diffusive properties and viscoelastic moduli scale robustly with wt%. Importantly, prominent changes in both biophysical properties arose at ∼4 wt%, consistent with a gel transition (from a more viscous-dominated solution to a more elastic-dominated gel). These findings have significant implications for: (1) penetration of cilia into the mucus layer and effectiveness of mucus transport; and (2) diffusion vs. immobilization of micro-scale particles relevant to mucus barrier properties. These data provide compelling evidence for mucus solids concentration as a baseline clinical biomarker of mucus barrier and clearance functions.
PMCID: PMC3928107  PMID: 24558372
4.  Tracheobronchial air-liquid interface cell culture: a model for innate mucosal defense of the upper airways? 
Human tracheobronchial epithelial cells grown in air-liquid interface culture have emerged as a powerful tool for the study of airway biology. In this study, we have investigated whether this culture system produces “mucus” with a protein composition similar to that of in vivo, induced airway secretions. Previous compositional studies of mucous secretions have greatly underrepresented the contribution of mucins, which are major structural components of normal mucus. To overcome this limitation, we have used a mass spectrometry-based approach centered on prior separation of the mucins from the majority of the other proteins. Using this approach, we have compared the protein composition of apical secretions (AS) from well-differentiated primary human tracheobronchial cells grown at air-liquid interface and human tracheobronchial normal induced sputum (IS). A total of 186 proteins were identified, 134 from AS and 136 from IS; 84 proteins were common to both secretions, with host defense proteins being predominant. The epithelial mucins MUC1, MUC4, and MUC16 and the gel-forming mucins MUC5B and MUC5AC were identified in both secretions. Refractometry showed that the gel-forming mucins were the major contributors by mass to both secretions. When the composition of the IS was corrected for proteins that were most likely derived from saliva, serum, and migratory cells, there was considerable similarity between the two secretions, in particular, in the category of host defense proteins, which includes the mucins. This shows that the primary cell culture system is an important model for study of aspects of innate defense of the upper airways related specifically to mucus consisting solely of airway cell products.
PMCID: PMC2636953  PMID: 18931053
mucus; mucin; innate immunity; proteomics; human tracheobronchial epithelial cell culture

Results 1-4 (4)