Phenotypic and physiologic variability in nasal epithelium cultured from smokers and non-smokers exposed to secondhand tobacco smoke

The emergence of air-liquid interface (ALI) culturing of mammalian airway epithelium is a recent innovation for experimental modeling of airway epithelial development, function, and pathogenic mechanisms associated with infectious agent and irritant exposure. This construct provides an experimental platform for in vitro propagation, manipulation, and testing of airway epithelium in a structural and physiologic state that emulates in vivo organization. In this study, we have cultured nasal epithelial biopsies from human subjects with variable histories of tobacco smoke exposure and assessed ciliary beat frequency (CBF) after an extended interval in vitro relative to CBF determined on biopsies from the same subjects immediately upon acquisition. We observed elevated CBF in nasal epithelial biopsies as well as persistence of accelerated CBF in ALI cultures deriving from biopsies of smokers and non-smokers exposed to environmental tobacco smoke compared to CBF in cultures from biopsies of well-documented non-smokers. Moreover, cultures deriving from smokers exhibited reduced ciliation as the cultures matured. These studies document that nasal epithelium cultured in the ALI system retains physiologic and phenotypic characteristics of the epithelial layer in vivo even through rounds of proliferative expansion. These observations suggest that stable epigenetic factors affecting regulation of ciliary function and phenotype commitment may be operative.