Adenosine triphosphatase expression correlates with ciliary activity of respiratory epithelium in vitro

In vitro culture of respiratory epithelium is of great utility for pharmacological investigations and tissue engineering. Up to now, the degree of differentiation of respiratory cells cultured in vitro has exclusively been estimated by measuring ciliary beat frequency (CBF). Ciliary motility is dependent on the function of the motor protein dynein that is composed of at least two heavy chains, sharing attributes of adenosine triphosphatases (ATPases). CBF is further dependent on medium conditions and does not allow to draw any accurate conclusion on the proportion of fully differentiated ciliated cells in culture. For this reason we introduced the immunohistochemical detection of a 100-kD ATPase subunit as a correlation with dynein activity in human respiratory cell tissue culture. Our results show that the amount of immunohistochemically detectable ATPase-subunit-positive cells strongly correlates with ciliary motility in vitro. Cultures without ciliary activity exhibited no ATPase staining, whereas in cell cultures with excessive ciliary beat, up to 15.1% of the cells were ATPase positive. Immunohistochemical detection of ATPase in respiratory cell cultures seems to be a sensitive and reproducible complement for the characterization of cultured ciliated epithelium.