Background: Chronic severe persistent asthma is associated with damaged epithelial cells with discontinuous tight junctions that contribute to dysregulated fibroblast and endothelial cell (mesenchymal) growth. Dermatophagoides species-derived proteases have been shown to cause damage to epithelial cell tight junctions.
Objective: To determine whether Dermatophagoides species can stimulate confluent A549 (cA549), a cell type with discontinuous tight junctions that approximate differentiated type II cells, to undergo altered growth and secrete putative soluble factors that affect the growth of human lung fibroblasts and microvascular endothelial cells.
Methods: Dialyzed Dermatophagoides pteronyssinus or Dermatophagoides farinae extracts (0, 300, 600, and 1000 AU/mL) were cultured with and without cA549 in serum-free media for 24 hours. After changes in cA549 growth were recorded, conditioned media from extracts with cA549 (CM) and without cA549 (control media [CTLM]) were transferred to fibroblasts and endothelial cells for 24 hours. Fibroblast and endothelial cell growth responses to CM and CTLM were observed and measured.
Results: All conditions showed greater than 95% cell viability. Confluent A549 showed dose-dependent growth changes characterized by increased aggregation when incubated with 300, 600, and 1000 AU/mL of D pteronyssinus in serum-free media relative to control. The CM, but not the CTLM, induced dose-dependent aggregation by fibroblasts and endothelial cells. Fibroblasts also showed decreased adhesion when incubated with CM. Dermatophagoides farinae-treated cA549 showed similar but weaker results. The use of serum, boiled CM, or boiled extract inhibited these findings.
Conclusions: Dialyzed Dermatophagoides species extracts altered cA549 growth and stimulated the secretion of factors that dysregulate mesenchymal cell growth in vitro.