title: IL-31 does not induce normal human ciliated epithelial cells to differentiate into a phenotype consistent with the pathophysiology of asthma.
abstract: BACKGROUND
  IL-31 is a novel cytokine that has been implicated in allergic diseases such as atopic dermatitis and more recently asthma. While IL-31 has been well studied in skin conditions such as atopic dermatitis, little is known about the role IL-31 plays in asthma and specifically the differentiation process of the bronchial epithelium, which is central to the pathogenesis of allergic asthma.
  
  
  METHODS
  We examined the effects of IL-13 (20 ng/ml), IL-31 (20 ng/ml) and an IL-13/IL-31 combination stimulation (20 ng/ml each) on the in vitro mucociliary differentiation of paediatric bronchial epithelial cells (PBECs) from healthy patients (n=6). IL-31 receptor (IL-31-RA) expression, markers of differentiation (goblet and ciliated cells), transepithelial electrical resistance (TEER), quantification of goblet and ciliated cells, real time PCR for MUC5AC, ELISA for VEGF, EGF and MCP-1 (CCL-2) and ELISA for MUC5AC were assessed.
  
  
  RESULTS
  We found that well-differentiated PBECs expressed IL-31-RA however it's expression did not increase upon stimulation with IL-31 or either of the other treatments. TEER indicated good formation of tight junctions which was found to be similar across all treatment groups (p=0.9). We found that IL-13 alone significantly reduced the number of ciliated cells compared with unstimulated (IL-13 stimuation: mean=4.8% (SD=2.5); unstimulated: mean=15.9%, (SD=7.4), p<0.01). IL-31 stimulation alone had no effect on ciliated cells whereas the IL-13/IL-31 combination stimulation significantly reduced the number of ciliated cells compared with control (IL-13/IL-31 combination: mean=5.1% (SD=4.6); unstimulated: mean=15.9%, (SD=7.4), p<0.01). We did not find that the combination of IL-13 and IL-31 had any additional effects to that of IL-13 alone. MUC5AC mRNA and secreted mucin was found in similar levels between unstimulated and all treatments, however IL-13 increased levels of MUC5AC mRNA by a factor of 2.84, albeit not significantly, compared with unstimulated cultures (IL-13 stimulation: mean=2.84 (SD=3.79); unstimulated: mean=1.0).
  
  
  CONCLUSIONS
  IL-31RA receptor is present on well-differentiated paediatric bronchial epithelial cells. IL-31 does not exhibit any detrimental effects on mucociliary differentiation. IL-31 does not appear to have a synergistic effect when combined in culture with IL-13, in the differentiation process.
authors.affiliation: Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, United Kingdom.
authors.forename: Jeremy C
authors.initials: JC
authors.lastname: Parker
authors.affiliation: Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, United Kingdom.
authors.forename: Surendran
authors.initials: S
authors.lastname: Thavagnanam
authors.affiliation: Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, United Kingdom.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Skibinski
authors.affiliation: Department of Anaesthetics, Belfast Health and Social Care Trust, Royal Victoria Hospital, Belfast BT12 6BE, Northern Ireland, United Kingdom.
authors.forename: Michael
authors.initials: M
authors.lastname: McBrien
authors.affiliation: Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, United Kingdom.
authors.forename: Liam G
authors.initials: LG
authors.lastname: Heaney
authors.affiliation: Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, United Kingdom ; Department of Child Health, Royal Belfast Hospital for Sick Children, Belfast Health and Social Care Trust, Royal Victoria Hospital, Belfast BT12 6BE, Northern Ireland, United Kingdom.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Shields
keywords: ALI, Air Liquid Interface; Bronchial epithelial cells; Ciliated cells; Differentiation; Goblet cells; IL-31; PBEC, Paediatric Bronchial Epithelial Cells; TEER, Transepithelial Electrical Resistance; WD-PBEC, Well-differentiated Paediatric Bronchial Epithelial Cells