Functional consequences of abnormal fatty acid profiles in cultured airway epithelial cells

Maintenance of serum-free conditions for the culture of TE or other airway epithelial cells provides a defined environment in which to explore the regulation of cellular functions. Yet TE cells appear to be dependent on the medium for essential, if not all, polyunsaturated fatty acids. At present, some laboratories routinely use serum to support the growth of airway epithelial cells, presumably in part through recognition that cells of mammalian origin require an exogenous source of lipids. While 5% FBS can increase the linoleic and arachidonic acid content of cultured rabbit and human TE cells, it does not fully restore the fatty acid composition of cultured TE cells to that of freshly isolated cells, particularly in the case of human TE cells. Equally good, if not better, repair of membrane fatty acid composition can be achieved by addition of a defined, commercial non-serum source of lipids (Excyte III) plus exogenous arachidonic acid. Cultured TE cells maintained in serum-free medium have been shown to be deficient in prostaglandin and HETE production, both at baseline and in response to physiological stimuli compared to TE cells with greater endogenous content of arachidonic acid. Differences between lipid supplemented and unsupplemented cultured TE cells in cAMP response to PGE2 and in susceptibility to hyperoxic injury have been observed. Other cellular functions regulated by the fatty acid composition of membrane lipids may also be impaired in lipid unsupplemented cells. It is evident that the maintenance of as normal as possible membrane fatty acid content is essential to the use of cultured TE cells as experimental models of airway epithelium.