Abstract
In real life, humans are exposed to whole pollen grains at the air epithelial barrier. We developed a system for in vitro dosing of whole pollen grains at the Air-Liquid Interface (ALI) and studied their effect on the immortalized human bronchial epithelial cell line BEAS-2B. Pollen are sticky and large particles. Dosing pollen needs resuspension of single particles rather than clusters, and subsequent transportation to the cells with little loss to the walls of the instrumentation i.e. in a straight line. To avoid high speed impacting insults to cells we chose sedimentation by gravity as a delivery step. Pollen was resuspended into single particles by pressured air. A pollen dispersion unit including PTFE coating of the walls and reduced air pressure limited impaction loss to the walls. The loss of pollen to the system was still about 40%. A linear dose effect curve resulted in 327-2834 pollen/cm2 (± 6.1%), the latter concentration being calculated as the amount deposited on epithelial cells on high pollen days. After whole pollen exposure, the largest differential gene expression at the transcriptomic level was late, about 7 hours after exposure. Inflammatory and response to stimulus related genes were up-regulated. We developed a whole pollen exposure air-liquid interface system (Pollen-ALI), in which cells can be gently and reliably dosed.
Highlights
A rise in allergic diseases like asthma, hay fever and food allergies has been reported since the 1960s, which is referred to as the allergy epidemic of the 20th century [1]
We propose that the same should be done for pollen exposure as pollen grains are dosed at the air-liquid interface in real life
We developed methods that allowed resuspension of pollen as single particles, developed an assay to study the adhesion of a pollen grain to different surfaces, and created a chamber that allows a reproducible and even distribution of the whole pollen
Summary
A rise in allergic diseases like asthma, hay fever and food allergies has been reported since the 1960s, which is referred to as the allergy epidemic of the 20th century [1]. Airborne allergens like pollen are one of the main causes of allergy and may cause rhinoconjuctivitis, eosinophilic bronchitis or allergic asthma. Humans are exposed to whole pollen grains. These grains are larger than most epithelial cells (21 μm for birch, 45 μm for grass pollen) [3,4,5]. The aeroallergens reside inside the pollen [6] and are released within minutes after being hydrated [7], i.e. upon contact with (humid) epithelial cells.
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