B28-24 Persistent Hypoxia-associated Gene Expression and Inflammatory Pathways in Airway Epithelium Following Severe Primary Graft Dysfunction

Rationale Primary graft dysfunction (PGD) following lung transplant is linked with short- and long-term morbidity and mortality, but the mechanisms linking PGD with long term complications are poorly defined. We previously identified hypomethylation of hypoxia-associated genes in airways 1 year following PGD. Here we tested the hypothesis that severe PGD is associated with persistent epithelial hypoxia gene expression. Methods Through the NIH Lung Transplant Consortium, we prospectively enrolled lung transplant recipients at 3 centers with PGD grade 0-1 or grade 3 and collected airway brushes at 1-, 6-, and 12-months post-transplant. Separately, airway brushing cells were grown at air-liquid interface and subjected to hypoxia and CoCl2. Differential expression was performed on cultured cells, using DESeq2, Stouffer, and Benjamini & Hochberg methods, to determine an airway epithelial hypoxia response program. This signature was assessed as a metagene in airway brush transcriptomes after variance-stabilizing transformation using generalized estimating equation-adjusted models including PGD, time, and center. Results Hypoxia stimuli in epithelial cell cultures were associated with 951 upregulated genes and 663 downregulated genes at an FDR p-value of 0.1. Airway brushes were collected from 20 participants with severe PGD and 26 participants with PGD grade ≤1. In the multicenter cohort, severe PGD was associated with 189 upregulated and 49 downregulated genes (Figure 1A). Gene ontology analysis identified upregulation of inflammation and wound healing pathways, in addition to hypoxia (Figure 1B). The epithelial hypoxia metagene was increased at 1 month relative to other time points (0.48 standard deviations, SD, P = 0.01), but not associated with PGD (0.19 SD, P = 0.39, Figure 1C). Conclusions Hypoxia-associated gene expression persists in airways in the first month post-transplant. Transcriptional patterns of inflammation and wound healing are present in small airways in the first year following PGD. A persistence of PGD-associated gene expression may help explain the link between PGD and its long-term sequela.