Monolayers of human alveolar epithelial cells in primary culture for pulmonary absorption and transport studies

Purpose. To develop a cell culture model of human alveolar epithelial cells in primary culture for the in vitro study of pulmonary absorption and tran sport. Methods. Type II pneumocytes isolated from normal human distal lung tissue by enzyme treatment and subsequent purification were plated on fibronectin/ collagen coated polyester filter inserts, and cultured using a low-serum gr owth medium. Characterization of the cell culture was achieved by bioelectr ic measurements, cell-specific lectin binding, immunohistochemical detectio n of cell junctions, and by assessment of transepithelial transport of dext rans of varying molecular weights. Results. In culture, the isolated cells spread into confluent monolayers, e xhibiting peak transepithelial resistance of 2,180 +/- 62 Omega x cm(2) and potential difference of 13.5 +/- 1.0 mV (n = 30-48), and developing tight junctions as well as desmosomes. As assessed by lectin-binding, the cell mo nolayers consisted of mainly type I cells with some interspersed type II ce lls, thus well mimicking the situation in vivo. The permeability of hydroph ilic macromolecular FITC-dextrans across the cell monolayer was found to be inversely related to their molecular size, with P-app values ranging from 1.7 to 0.2 x 10(-8) cm/sec. Conclusions. A primary cell culture model of human alveolar epithelial cell s has been established, which appears to be a valuable in vitro model for p ulmonary drug delivery and transport studies.