A Single-cell Lung Atlas of Human Pulmonary Arterial Hypertension

Abstract Introduction: Pulmonary arterial hypertension (PAH) is a disaster disease characterized by obliterative vascular remodeling and persistent increase of vascular resistance, leading to right heart failure and premature death. Understanding the cellular and molecular mechanisms will help develop novel therapeutic approaches for PAH patients. Hypothesis: Single-cell RNA sequencing (scRNA-seq) analysis fosters better understanding of the cellular and molecular mechanisms that drive the initiation and progression of PAH. Methods: Flash-frozen lung tissues from 10 healthy donors, 10 idiopathic PAH, 10 drug and toxin induced PAH, 10 systemic and pulmonary shunting induced PAH patients of varying sexes, ethnicities and ages, were obtained from Pulmonary Hypertension Breakthrough Initiative (PHBI). Lung tissue specimens were processed for fixed scRNA-seq. The cell proportion change, gene expression, and pathway analysis were evaluated between different disease subclasses, sexes, ages in different cell types. Results: Our analysis reveals 317,414 cells, 33 clusters and 9 major cell types, including endothelial cell (EC), alveolar cell, fibroblast, smooth muscle cell (SMC), pericyte, myeloid cell, lymphocyte, airway epithelial cell, platelet. Cell proportion analysis demonstrated an increase in the proportion of venous ECs, adventitial fibroblasts and myofibroblasts, alveolar macrophages, B cells, plasma cells and a decrease in capillary ECs 2 and pericytes in PAH lungs. KEGG Pathway analysis showed that upregulated pathways related to Herpes simplex virus 1 infection, ECM-receptor interaction, Complement and coagulation cascades, Hedgehog signaling and TGF-beta signaling pathway, while downregulated pathways enriched in IL-17 signaling, TNF signaling, MAPK signaling pathway in PAH patients. Female PAH patients exhibited an increased proportion of myofibroblasts, and platelets compared to male PAH patients. MsigDB Hallmark Pathway analysis showed that p53 pathway was upregulated, whereas inflammatory response, hypoxia, epithelial mesenchymal transition signaling pathways were downregulated in female PAH patients. PAH patients older than 21 years exhibited an increase in the cell proportion of platelets, SMCs, arterial ECs and venous ECs, and alveolar macrophages and a reduction of B cells and plasma cells. Conclusions: Our integrated analysis of human PAH lung atlas dataset provides a comprehensive illustration of lung cell populations and molecular signature in PAH patients within different sexes, ages and subclasses.