Abstract

BACKGROUND: Hypoxia-inducible factors (HIFs), especially HIF-1alpha and HIF-2alpha, are key mediators of the adaptive response to hypoxic stress and play essential roles in maintaining lung homeostasis. Human and animal genetics studies confirm that abnormal HIF correlates with pulmonary vascular pathology and chronic lung diseases, but it remains unclear whether endothelial cell (EC) HIF production is essential for microvascular health. The large airway has an ideal circulatory bed for evaluating histologic changes and physiology in genetically-modified rodents.METHODS: The tracheal microvasculature of mice, with conditionally-deleted or overexpressed HIF-1alpha or HIF-2alpha, was evaluated for anatomy, perfusion, and permeability. Angiogenic signaling studies assessed vascular changes attributable to dysregulated HIF expression. An orthotopic tracheal transplantation model further evaluated the contribution of individual HIF isoforms in airway ECs.RESULTS: The genetic deletion of Hif-2alpha, but not Hif-1alpha, caused tracheal EC apoptosis, diminished pericyte coverage, reduced vascular perfusion, defective barrier function, overlying epithelial abnormalities and subepithelial fibrotic remodeling. HIF-2alpha promoted microvascular integrity in airways through endothelial angiopoietin-1/TIE2 signaling and Notch activity. In functional tracheal transplants, HIF-2alpha deficiency in airway donors accelerated graft microvascular loss, whereas HIF-2alpha or angiopoietin-1 overexpression prolonged transplant microvascular perfusion. Augmented endothelial HIF-2alpha in transplant donors promoted airway microvascular integrity and diminished alloimmune inflammation.CONCLUSIONS: Our findings reveal that the constitutive expression of endothelial HIF-2alpha is required for airway microvascular health.

View details for PubMedID 30586708