Airway epithelial cells fulfil several functions that are implicated in protecting
the airways from exogenous insults. These defense functions range from the structural
integrity of mucus and the differentiation of the epithelial cell layer to the production
of inflammatory mediators.
After an explant-outgrowth culture of epithelial cells from small bronchi pure populations
of primary isolated normal human bronchial epithelial cells (NHBE) were cultured with
lung fibroblasts as bilayer on a 24-well HTS-Transwell filter plate. The cells were
grown on a collagen type I and maintained at an air-liquid interface (ALI) by feeding
basolaterally with medium. Barrier properties and morphological phenotype were compared
over 42 days. The NHBE formed confluent layers, expressing functional tight junctions
as measured by transepithelial electrical resistance (TER). Mucus production and cilia
formation reappeared in the co-culture model dependent on the individual donors after
21 to 42 days. A key function of airway epithelial cells is the production of inflammatory
mediators such as the neutrophil chemoattractant interleukin 8 (IL-8) and the cytokine
IL-6, which has both pro- as well as anti-inflammatory activities. Supernatants were
taken from the apical and basolateral side after 7, 14, 21, 28, 35 and 42 days of
the co-culture and the cytokines IL-8 and IL-6 were measured by ELISA. The levels
of IL-6 and IL-8 increased on the apical side to 5078.82±954.31pg/ml for IL-6 and
up to 12.04±1.02ng/ml for IL-8. Basolaterally the levels remained unchanged.
In summary, the co-culture of NHBE and human lung fibroblasts mimics the structure
of native polarized bronchiolar epithelium. Mucus production and the production of
inflammatory mediators such as Il-6 and IL-8 can protect the cells from exogenous
insults as it would be in the proximal airways. With this model it is hoped to understand
how the upper airway mucosa reacts to noxious substances and other pathological situations.
