D16-05 Single-Cell Resolution Spatial Transcriptomics Reveals Dysregulation of Fibroblasts and Arterial Endothelial Cells in Human Pulmonary Arterial Hypertension

Abstract Rationale Idiopathic pulmonary arterial hypertension (IPAH) is a progressive and life-threatening disease characterized by elevated pulmonary arterial pressure and vascular resistance without an identifiable cause. Some studies have associated fibroblasts and arterial endothelial cells (AECs) with pulmonary vascular remodeling in IPAH. However, the interactions between these cells and other cells have not been profiled in the spatial context of IPAH lung tissue. This study aims to delineate single-cell resolution spatial transcriptomic profiles of human IPAH lungs to uncover dysregulated cellular and molecular pathways in IPAH. Methods Lung tissues from 10 healthy donors and 10 patients with idiopathic pulmonary arterial hypertension (IPAH) were obtained through the Pulmonary Hypertension Breakthrough Initiative (PHBI). Spatial transcriptomic profiling was performed using the 10x Genomics Xenium platform with a 5K gene panel. Cell types were annotated by integrating matched single-cell RNA-seq data from the same patient cohort using Seurat v5. The abundance and transcriptional profiles of alveolar epithelial cells (AECs) and fibroblasts were compared between IPAH and healthy control samples. Results A total of 702,159 cells were identified across 20 samples (10 controls, 10 IPAH patients). Twenty-five distinct cell types were annotated (Figure A), with spatial localization consistent with typical structure of lung (Figure B). Fibrotic regions surrounding the arteries were observed (Figure B). Arterial endothelial cells and fibroblasts were significantly increased in IPAH lungs (Figure C). Expression of ENPP2, ESM1, and POSTN were elevated in AECs from IPAH lungs (Table D). Additionally, expression of ZFAND5, IRS2, and HIF1A were elevated in fibroblasts from IPAH lungs (Table E). Conclusion This study presents the first spatial transcriptomic atlas of human PAH lungs at single-cell resolution. We identified increased abundance and transcriptional alterations in arterial endothelial cells and fibroblasts, underscoring their key roles in vascular remodeling. These findings demonstrate the power of high-resolution spatial transcriptomics to reveal novel pathogenic mechanisms and uncover potential therapeutic targets in PAH. This abstract is funded by: NHLBI