Abstract Body: Introduction: Pulmonary Arterial Hypertension (PAH) is a progressive and debilitating disease with currently few treatment options. The pathological hallmark of PAH is remodeling of the pulmonary vasculature, which involves intimal and medial thickening, muscularization of distal pulmonary arteries, and the development of complex plexiform lesions. Growing evidence indicates that endothelial cell (EC) dysfunction is an early trigger in abnormal vascular remodeling, with dysregulated EC proliferation and angiogenesis playing a critical role. Poldip2 has emerged as a crucial modulator of EC homeostasis. Herein, we hypothesize that endothelial Poldip2 enhances PAH pathogenesis.
Methods: To investigate the role of EC Poldip2 in PAH pathogenesis, EC-specific Poldip2-knockout mice [Poldip2^ECKO] and littermate controls (n=7-12) were subjected to the SU5416/Chronic hypoxia (SuHx) PAH model. Right ventricular systolic pressures (RVSP) were measured using invasive hemodynamics, and vascular remodeling was quantified using IHC. Single-nucleus RNA sequencing (snRNA-seq) was performed to explore the underlying mechanisms, followed by mechanistic studies on human ECs using lentiviral shRNA targeting Poldip2.
Results: Poldip2^ECKO mice had reduced RVSP (34.2 mmHg, 95% CI: 32.0-36.5) and medial thickness (10.6 m, 95% CI: 9.1-12) compared to littermates (43.2 mmHg, 95% CI: 37.9-48.5; 14.7 m, 95% CI: 12.0-17.3) in SuHx model. Through snRNA-seq, we found arterial EC populations were reduced in Poldip2^ECKO compared to Poldip2^f/f mice. In arterial ECs, proliferative and angiogenic pathways were downregulated in Poldip2^ECKO mice. Trajectory analysis showed that EC arterialization trajectories were attenuated in Poldip2^ECKO mice. Poldip2-deficient ECs also exhibited reduced proliferation compared to wild-type ECs in vitro. Additionally, CellChat revealed reduced EC-smooth muscle cell communication pathways (e.g., PDGF) in Poldip2^ECKO mice.
Conclusions: Our results suggest endothelial Poldip2 is a critical mediator of PAH pathogenesis through enhanced EC proliferation, angiogenesis, and paracrine signaling. This work suggests endothelial Poldip2 may represent a novel therapeutic target for PAH.