Abstract Rationale Pulmonary hypertension (PH) associated with chronic lung disease (COPD-PH) is the second most common cause of PH and carries high morbidity and mortality. Patients with COPD-PH exhibit disproportionate right ventricular dysfunction and poor outcomes compared with other PH groups. While endothelial dysfunction is central to PH pathobiology, prior studies have been limited to end-stage tissues. There remains a critical need to characterize pulmonary artery endothelial cells (PAECs) from patients with early-stage PH to uncover mechanistic differences between COPD-PH and pulmonary arterial hypertension (PAH). Methods PAECs were prospectively isolated from right heart catheterization (RHC) tips of patients with PAH and COPD-PH (n = 4 total; 2 per group) using a recently validated technique. Control subjects were those referred for RHC but who did not meet criteria for a PH diagnosis. Endothelial identity was confirmed by immunofluorescence for CD31, VE-cadherin, and von Willebrand factor (vWF). Functional assays assessed angiogenesis, proliferation, and apoptosis. Single-cell RNA sequencing (scRNA-seq) was performed on 22,000 pre-passaged PAECs, and unsupervised clustering was used to define transcriptional subpopulations. Results PAECs demonstrated typical endothelial morphology and marker expression. Functional assays suggested a hypoproliferative and pro-apoptotic phenotype in COPD-PH compared with control. ScRNA-seq identified 14 transcriptionally distinct PAEC clusters, all expressing canonical endothelial genes (PECAM1, VWF, KDR, CDH5). Both PAH and COPD-PH contained all clusters, but cluster composition differed by disease, with clusters 4 and 12 enriched in COPD-PH. These clusters were characterized by upregulation of cell adhesion and apoptosis pathways. In contrast, PAH PAECs demonstrated enrichment of genes related to angiogenesis and metabolic activity. Expression of circulating or progenitor EC markers (PROM1, THY1, CXCR4, ETV2) was low, supporting pulmonary arterial origin. Conclusions This study establishes a reproducible method to isolate PAECs from RHC samples, enabling investigation of early-stage endothelial phenotypes in PH. Preliminary findings suggest that COPD-PH PAECs exhibit a distinct, pro-apoptotic, adhesion-enriched transcriptomic profile compared to PAH, consistent with endothelial loss and vascular rarefaction observed in COPD-associated vascular remodeling. Ongoing studies are expanding scRNA-seq and transcriptomic analyses of both PAECs and blood outgrowth endothelial cells to define circulating-endothelial interplay in PH pathogenesis. This abstract is funded by: Borstein Family Foundation, Reuben M. Cherniack Fellowship, Colorado Pulmonary Vascular Disease Award, NIH 7R01HL144727, VA Merit Review Award 2 I01 BX00204
Massad et al. (Fri,) studied this question.