We previously demonstrated an essential role of Th17 cells in excessive mucous secretion and airway smooth muscle proliferation in a prolonged OVA-challenged C57BL/6 mouse model. However, the impact of Th17 cells in vascular remodeling, another characteristic feature of airway remodeling in asthma, remains elusive. This issue was further investigated in this study. The time-course experiments showed that progressively increasing levels of Th17 cells and IL-17A (not IL-17F) in the lungs of prolonged allergen-challenged mice were positively correlated with microvessel density in peribronchial tissues. In addition, exaggerated airway vascular remodeling in this mouse model was exacerbated by airway administration of IL-17A or adoptive transfer of Th17 cells. This effect was dramatically alleviated by the administration of anti-IL-17A Ab, but not anti-IL-17F Ab. Boyden chamber assays indicated that IL-17A accelerates endothelial progenitor cell (EPC) migration. Furthermore, EPC accumulation in the airways of allergen-exposed mice after adoptive transfer of Th17 cells was eliminated by blockade of IL-17A. We found that IL-17A promoted tubule-like formation rather than proliferation of pulmonary microvascular endothelia cells (PMVECs) in vitro. In addition, IL-17A induced PMVEC tube formation via the PI3K/AKT1 pathway, and suppression of the PI3K pathway markedly reduced the formation of tubule-like structures. Collectively, our results indicate that Th17 cells contribute to the airway vascular remodeling in asthma by mediating EPC chemotaxis, as well as PMVEC tube formation, via IL-17A rather than IL-17F.
Copyright © 2015 by The American Association of Immunologists, Inc.