Towards real life exposure: nasal epithelial cell stimulation with pollen particle aerosols

Currently, most researchers apply pollen extracts or -suspensions to assess the effects of pollen exposure on airway epithelia. How respiratory epithelia respond to pollen aerosols is not well studied because standardised methods to aerosolize pollen were not available until recently.

To develop and test a near-natural exposure model for pollen grains based on differentiated human nasal epithelial cells and a novel particle aerosoliser.

Primary human nasal epithelial cells were differentiated at the air-liquid interface and exposed to birch, timothy grass and ragweed pollen, either as aqueous extract, suspension, or particle aerosol generated with the VitroCell PowderX device. Morphology, physical barrier function, and cytokine responses were compared.

The cells responded to pollen aerosol exposure with strong mucus production and coordinated ciliary beating in attempt to clear the pollen grains. Pollen aerosols did not affect the transepithelial electrical resistance (TEER), whereas grass pollen extracts led to a significant TEER decrease. Extract exposure resulted in apical and basolateral cytokine release; aerosol exposure led to a directed, predominantly basolateral dose-dependent cytokine response. Cytokine responses to birch, grass and ragweed pollen differed, with birch pollen inducing lower levels of inflammatory cytokines, while timothy and ragweed pollen induced high levels of inflammatory cytokines and alarmins.

We were able to establish and characterize a biologically relevant pollen aerosol exposure system characterized by a directed cytokine response. The differences in response patterns to different pollen types likely reflect differential sensitisation mechanisms, warranting further research.