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A3810 - The Role of Hypoxia Inducible Factors in Maintenance of Airway Epithelial Health
Author Block: S. Pasupneti1, A. Tian2, X. Jiang2, M. R. Nicolls3; 1Pulmonary and Critical Care Medicine, Stanford University Medical Center, Palo Alto, CA, United States, 2Stanford University, Palo Alto, CA, United States, 3VA Palo Alto Health Care System, Palo Alto, CA, United States.
Purpose: Vascular endothelial cells (EC) can affect neighboring cell populations through release of “angiocrine factors”, which are growth factors that can alter cell phenotype and function. The hypoxia inducible factors (HIF) regulate signaling cascades that govern cell metabolism, proliferation, and angiogenesis. HIFs have also been clearly implicated in epithelial biology, though most studies have evaluated autocrine effects. Our group has shown that in a transgenic mouse model, endothelial cell specific deletion of HIF-2α results in disruption of the overlying airway epithelial barrier integrity and flattening of ciliated cells (unpublished). The purpose of this study, therefore, was to determine if crosstalk between airway endothelial and epithelial cells, due to angiocrine factors, can mediate adjacent epithelial changes. Methods: A transwell co-culture system was used to study the interaction between airway epithelial cells and vascular ECs. Pulmonary arterial ECs (PAECs) were seeded in the basal chamber. Transfection with adenoviral vectors expressing HIF-1α or HIF-2α resulted in upregulation of PAEC HIF-1α and/or HIF-2α. Similarly, treatment with a lentiviral construct expressing HIF-1α or HIF-2α caused downregulation of PAEC HIF-1α and/or HIF-2α. Concurrently, a heterogenous airway epithelial cell population (H292 cells) was seeded in the apical chamber and cultured separately. 72 hours after viral treatment, the media in the basal chamber was replaced and the apical chamber (with H292 cells) was added to the transwell system. 72 hours after co-culture, H292 cells were collected to evaluate relative mRNA expression of certain genes by RT-qPCR. Results: Upregulation of PAEC HIF-1α or HIF-2α resulted in increased expression of SCGB1A1, a club cell marker. Conversely, downregulation of PAEC HIF-1α or HIF-2α resulted in decreased SCGB1A1 mRNA expression. Similarly, upregulation of HIF-1α or HIF-2α resulted in decreased expression of CK19, an epithelial filament protein, and downregulation of HIF-2α led to increased CK19. Conclusion: Overall, these results suggest that endothelial-epithelial crosstalk may modulate epithelial phenotype and cell structure. While airway epithelial cells are a heterogenous population, certain cell types may be protective in certain disease states, such as club cells in chronic lung allograft dysfunction. Given these results, it is possible that manipulation of endothelial origin HIF may be therapeutic in certain disease states due to endothelial-epithelial cell cross talk.