D14-05 Immune-endothelial Transcriptomic Signatures Differentiate Oxygenation Severity in Pediatric Acute Respiratory Distress Syndrome

Abstract Rationale Traditional stratification of acute respiratory distress syndrome (ARDS) by hypoxemia severity describes clinical status but does not provide mechanistic insight into oxygenation differences. Among patients with comparable systemic illness severity yet varying oxygenation deficit, the drivers of lung-specific injury and inflammation remain unclear. Characterizing the transcriptomic landscape of pediatric ARDS may uncover molecular pathways contributing to oxygen impairment. We compared gene expression profiles across oxygenation index (OI) strata to identify differentially expressed genes (DEGs) and enriched biological pathways associated with oxygenation severity. Methods We analyzed whole-blood gene expression across OI-defined oxygenation severity in patients receiving invasive mechanical ventilation from CAF-PINT, a multi-institutional trial of children with heart or lung failure. RNA was extracted at baseline (day 0) and sequenced on the NovaSeq S4 platform (2 × 150 bp, ∼50M reads/sample). Patients were stratified into mild (OI 4) and severe (OI 16) groups (N = 49 each). Propensity score matching adjusted for age, PRISM score, hypotension, and sex. DEGs were identified using negative binomial models (EdgeR) with FDR 0.05 and |log2FC| ≥ 0.5. Gene Ontology (GO) and KEGG pathway enrichment were performed using the Database for Annotation, Visualization, and Integrated Discovery (DAVID). Top significantly enriched pathways were ranked by p-value and fold enrichment. Functional annotation results from DAVID were cross-referenced with NCBI Gene entries to validate gene functions and assess biological relevance to ARDS. Results Visualization of 683 DEGs by oxygenation group revealed distinct transcriptomic profiles between severe and mild ARDS. In the severe group, LHX4 (transcription factor implicated in lung development), PCSK9 (lipid and inflammatory regulation), SCN5A (epithelial barrier function), OLFM4 (neutrophil activation), ANKRD22 (interferon-mediated immune signaling), and CCNA1 (leukocyte cell cycle regulation) were upregulated (r 0.3, |log2FC| ≥ 0.5) and may contribute to immune-metabolic dysregulation in severe respiratory dysfunction. Conversely, PLA2G7 (platelet-activating factor degradation) and ZNF683 (T-cell transcriptional regulation) were elevated (r -0.3, |log2FC| ≥ 0.5) in patients with OI 4, suggesting roles in immune homeostasis and repair. Enrichment analysis highlighted cytokine signaling, granule release, and endothelial activation pathways in severe ARDS, indicating coordinated inflammatory and endothelial remodeling with increasing oxygenation deficit. Conclusions Despite comparable systemic disease severity, patients with severe pediatric ARDS exhibit distinct immune-endothelial transcriptomic profiles. Enrichment of granule, cytokine, and endothelial signaling pathways suggests that differential immune and vascular responses underlie worsening oxygenation. These findings highlight biological mechanisms that may explain variation in ARDS severity beyond conventional clinical measures. This abstract is funded by: CAF-PINT Supported by NHLBI grants R01HL114484 and NHLBI HL114484