Human airway barrier cells

A relatively new cell line that has not to date been characterised for its use in biopharmaceutics is based on primary airway epithelial cells infected with retroviruses expressing hTERT and HPV-16 E6/E7 (NuLi-1) [54], NuLi-1 cells were cultured on plastic up to passage 30. When grown on collagen-coated, semi-permeable membranes (Millicell-PCF), NuLi-1 TEER decreased only slightly over the 30 passages from 685 31 to 389 21 ohm.cm2. The TEER of NuLi-1 is similar to that observed with the primary bronchial cultures of 532 147 ohm.cm2. Thus, NuLi-1 cells can form an electrically tight airway epithelial barrier that mimics active and passive ion transport properties of primary human bronchial epithelial cells [54],... 

Human exposure to a combination of tobacco smoke and the house dust mites has been shown to result in allergic sensitization. It is believed that tobacco smoke impairs the barrier function of the airway epithelium, leading to increased access of allergens contained in the house dust mite. In vitro studies with human bronchial epithelial cells have confirmed this hypothesis. I42,43l In this instance it is believed that lipophiles in tobacco smoke serve to facilitate the permeation of toxic allergens. 

Therefore, it is advisable to choose a cellular model according to its representativeness only for some or at least one epithelial function rather than a model representative for the entire airway epithelium. Permanent cell lines have been used to investigate individual epithelial functions like transepithelial Na+, Cl", and water transport, barrier function, or secretory function. Those models are predictive in regard only to the tested function. However, they are quite valuable especially in approaches with a larger throughput, since a sufficient amount of cells with an appropriate and reproducible quality are relatively easy to obtain. The use of human cell lines holds the advantage that toxicants can be tested on cells of the relevant host species and that results from these experiments need not be scrutinized for interspecies compatibility. 

We used in vitro models of lung epithelial cell lines or primary cells to determine E25 permeability. Two different cell types were used to mimic the airway and alveolar epithelium of the lung to study transport. Calu-3, a human cell line derived from an airway carcinoma, when grown at an air/liquid interface, differentiate to form a secretory airway epithelium (17). Rat primary epithelial cells isolated as described by Cheek et al. (18) form a tight barrier similar in structure and function to the alveolar surface. Both cell types when grown to confluence form tight junctions and differentiate and polarize so that the apical or air surface has different characteristics than the basolateral or blood side. The typical transepithelial resistance observed was 350 or >1000 ohms-cm for Calu-3 cells or primary rat alveolar cells, respectively. Once an acceptable resistance was achieved, E25 (2 mg/mL) was placed in either the apical or the basolateral chamber. Cell monolayers were incubated at 37°C for up to 3 hours and ELISA measured the amount of E25 that translocated the epithelial layer and appeared in the receiver well. The apparent permeability (Papp) of the epithelium for E25 was calculated as ... 

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