An in vitro model to study effects of airborne pollutants on human ciliary activity

A method to study the effects of airborne pollutants on ciliary activity of isolated human respiratory cells is presented. Human respiratory cells were scraped from nasal cavities of 25 healthy volunteers and washed in Ringer's solution. The cells were placed on polycarbonate membranes (3 microns pore size) and kept in macroplate holders swimming on Ringer's solution. Cells were thus kept humid and were supplied with nutrients through the pores of the membrane by capillary forces, while their surface was exposed to the gaseous environment. Isolated respiratory cells were exposed to SO2, NO2, and mixtures of SO2 and NO2 in various concentrations for 30 min and for 2 h. Exposure to synthetic air served as control. Ciliary beat frequency was measured using video-interference contrast microscopy, before and after exposure to the various gases. Exposure of isolated respiratory cells to a non-toxic gaseous environment resulted in a 20% reduction of ciliary beat frequency. A concentration-dependent decrease of ciliary beat frequency following exposure to SO2 in concentrations ranging between 2.5 and 12.5 ppm was found. Exposure to NO2 up to 2 h in concentrations ranging between 3 ppm and 15 ppm did not decrease ciliary beat frequency. No cumulative effect was found, if a mixture of SO2 (2.5 ppm) and NO2 (12 ppm) was applied.