Mucus and mucus flake composition and abundance reflect inflammatory and infection status in cystic fibrosis

• Published in: Journal of cystic fibrosis 2022-11, Vol.21 (6), p.959-966
• Main Authors: Markovetz, Matthew R., Garbarine, Ian C., Morrison, Cameron B., Kissner, William J., Seim, Ian, Forest, M. Gregory, Papanikolas, Micah J., Freeman, Ronit, Ceppe, Agathe, Ghio, Andrew, Alexis, Neil E., Stick, Stephen M., Ehre, Camille, Boucher, Richard C., Esther, Charles R., Muhlebach, Marianne S., Hill, David B.
• Format: Article
• Language: English
• Subjects: Airway mucus; Biomarkers; Child; Child, Preschool; Cystic Fibrosis; DNA; Gel-forming mucins; Humans; Infection; Microrheology; Mucin 5AC; Mucus; Mucus flakes; Respiratory System; Young Adult
• ISSN: 1569-1993; 1873-5010
• DOI: 10.1016/j.jcf.2022.04.008

•Mucus flakes in CF BALF were larger and more abundant than flakes in normal BALF.•Mucin and DNA content were also elevated in CF BALF.•Insoluble CF flakes contained a greater proportion of mucins, which were mostly soluble in normal subjects.•MUC5B/MUC5AC ratio is altered in CF mucus flakes compared to normal subjects.•The biophysical properties of mucus flakes were also altered in CF flakes. Mucus hyperconcentration in cystic fibrosis (CF) lung disease is marked by increases in both mucin and DNA concentration. Additionally, it has been shown that half of the mucins present in bronchial alveolar lavage fluid (BALF) from preschool-aged CF patients are present in as non-swellable mucus flakes. This motivates us to examine the utility of mucus flakes, as well as mucin and DNA concentrations in BALF as markers of infection and inflammation in CF airway disease. In this study, we examined the mucin and DNA concentration, as well as mucus flake abundance, composition, and biophysical properties in BALF from three groups; healthy adult controls, and two CF cohorts, one preschool aged and the other school aged. BALFs were characterized via refractometry, PicoGreen, immunofluorescence microscopy, particle tracking microrheology, and fluorescence image tiling. Mucin and DNA BALF concentrations increased progressively from healthy young adult controls to preschool-aged people and school-aged people with CF. Notably, mucin concentrations were increased in bronchoalveolar lavage fluid (BALF) from preschool-aged patients with CF prior to decreased pulmonary function. Infrequent small mucus flakes were identified in normal subjects. A progressive increase in the abundance of mucus flakes in preschool and school-aged CF patients was observed. Compositionally, MUC5B dominated flakes from normal subjects, whereas an increase in MUC5AC was observed in people with CF, reflected in a reduced flaked MUC5B/MUC5AC mucin ratio. These findings suggest mucus composition and flake properties are useful markers of inflammatory and infection-based changes in CF airways.