The novel use of the human nasal epithelial cell line RPMI 2650 as an in vitro model to study the influence of allergens and cytokines on transforming growth factor‐β gene expression and protein release

Summary Background The epithelial accumulation of mast cells is a feature of allergic rhinitis and this has been linked to the expression of the known mast cell chemoattractant transforming growth factor‐β (TGF‐β) at this site. Little is known concerning the regulation of TGF‐β gene expression or protein release by nasal epithelial cells. To address this we have utilized the RPMI 2650 human nasal epithelial cell line, which has some features that closely resemble normal nasal epithelium and has been reported to secrete a TGF‐β‐like molecule. Objectives To investigate the regulation of TGF‐β gene expression and protein secretion in RPMI 2650 nasal epithelial cells following exposure to allergens (house dust mite (HDM) and grass pollen) and mast cell associated T‐helper type 2 (Th2) cytokines (IL‐4, IL‐13, and TNF‐α). Methods Light and scanning electron microscopy was used to evaluate the morphology of RPMI 2650 cells in culture, enzyme‐linked immunosorbent assay was used to investigate their TGF‐β secretory capacity and the identification of the TGF‐β isotype(s) involved, flow cytometry was used to demonstrate the presence of TGF‐β receptors on the RPMI 2650 cells, and the quantitative real‐time TaqMan PCR was used to measure TGF‐β gene expression. Results TGF‐β 2 was identified as the main isotype secreted by the RPMI 2650 cells. HDM allergens and TNF‐α increased both TGF‐β gene expression and protein release from these cells, whereas grass pollen, IL‐4, and IL‐13 were without effect. Conclusions The RPMI 2650 nasal epithelial cell line represents a valid in vitro model to evaluate the regulation of TGF‐β biology. In this system HDM allergens have stimulatory activity that is fundamentally different from that of grass pollen allergens, and the Th2 cytokines IL‐4 and IL‐13 are without effect. The ability of TNF‐α to up‐regulate both TGF‐β gene expression and protein release indicates that mast cell–epithelial interactions concerning TGF‐β are bi‐directional and this may be fundamental to epithelial immunoregulation. The availability of a model system, such as the RPMI 2650 cells, will enable the early evaluation of future novel and targeted interventions directed toward the aberrant responses of upper airway structural cells.