Differentiated structure and function of cultures from human tracheal epithelium

Here we describe the conditions which allow cultured human tracheal epithelial cells to retain the ion transport properties and ultrastructure of the original tissue. The order of potency of growth supports and media additives in elevating baseline short-circuit current (I(sc)) and responses to mediators were vitrogen gel (VIT) > extracellular matrix from bovine corneal endothelial cells (ECM) > human placental collagen (HPC), and 2% Ultroser G serum substitute (USG) > 5% fetal calf serum (FCS) > defined growth factors (GF). For all combinations of medium and growth supports, an air interface (AIR) gave better electrical properties than immersion feeding (IMM). As opposed to our earlier conditions (HPC/FCS/IMM), the best new combination (VIT/USG/AIR) produced higher baseline I(sc) (58.0 ± 10.6 vs. 5.1 ± 1.0 μA/cm²) and increased I(sc) responses to isoproterenol (6.1 ± 1.5 vs. 0.8 ± 0.3 μA/cm²) and bradykinin (9.6 ± 2.0 vs. 1.0 ± 0.2 μA/cm²), while retaining high transepithelial resistance (227 ± 5 Ω · cm²). VIT/USG/AIR led to the appearance of cilia, an increase in the depth of the cell sheets (50 vs. 10 μm), longer and more frequent apical microvilli, and increased interdigitations of the basolateral membrane. Protein and DNA content were also significantly increased. Secretory granules were present which stained with antibody to goblet cells, but not to serous or mucous gland cells. CF cells grown in VIT/USG/AIR showed high baseline I(sc) (69 ± 18 μA/cm²) and a proportionately larger inhibition of I(sc) by amiloride (70 ± 10 vs. 34 ± 3%). I(sc) did not respond to isoproterenol, and the response to bradykinin was 22% normal.