B18-01 Ror2 Dysregulation Drives Pericyte Dysfunction and Microvascular Instability in Pulmonary Arterial Hypertension via Disruption of Wnt Signaling Activity

Rationale Pulmonary arterial hypertension (PAH) is a progressive vasculopathy characterized by loss and aberrant regeneration of pulmonary microvessels, ultimately leading to elevated pulmonary arterial pressures and right heart failure. We and others have shown that disrupted endothelial-pericyte (EC-PC) communication is a key driver of microvascular rarefaction and maladaptive vascular remodeling in PAH, in part due to impaired Wnt ligand release by pulmonary microvascular endothelial cells. However, the identity of the Wnt receptor that integrates endothelial cues to regulate pericyte activation and stabilize EC-PC interactions remain unknown. The receptor tyrosine kinase-like orphan receptor2 (ROR2) modulates the balance between canonical Wnt/β-catenin and non-canonical Wnt/planar cell polarity (PCP) pathways, thereby regulating proliferation, cytoskeletal dynamics, and cell motility. Although ROR2 dysregulation is implicated in cancer and congenital cardiovascular malformations, its role in PAH and pericyte-driven microvascular regulation has not been defined. We hypothesized that ROR2 dysregulation in PAH pericytes disrupts Wnt signaling balance, destabilizes EC-PC interactions, and promotes microvascular loss and vascular remodeling. Methods Primary human lung pericytes from donor and PAH lungs were used to define how ROR2 regulates canonical and non-canonical Wnt pathways. Pericytes were transfected with wild-type or domain-specific ROR2 constructs to dissect functional contributions to β-catenin and PCP signaling. To assess ROR2 function in vivo, we generated a pericyte-specific conditional ROR2-overexpressing mouse model (ROR2^PCOE) and exposed mice to chronic hypoxia to induce pulmonary hypertension. Pulmonary hemodynamics, right ventricular hypertrophy, microvascular architecture, and EC-PC contacts were quantified by invasive measurements, confocal microscopy, and morphometric analyses. Results PAH pericytes exhibited marked upregulation and hyperphosphorylation of ROR2, associated with increased β-catenin accumulation and reduced phosphorylation of PCP mediators JNK and CaMKII, indicating a shift toward canonical Wnt/β-catenin signaling and suppression of Wnt/PCP activity. These changes promoted pericyte hyperproliferation, enhanced contractility, and impaired motility. In vivo, ROR2 PCOE mice developed exacerbated pulmonary hypertension, right ventricular dysfunction, and increased pulmonary vascular remodeling following hypoxia, accompanied by significantly reduced distal pericyte coverage. Importantly, restoring ROR2 activity to physiological levels using siRNA or a ROR2-specific monoclonal antibody reversed PAH pericyte dysfunction and rescued stable EC-PC interactions. Conclusions These findings identify ROR2 as a central regulator of Wnt signaling balance in pulmonary pericytes and a key orchestrator of EC-PC communication. ROR2 overactivation drives pericyte phenotypic switching, destabilizes microvascular integrity, and promotes vascular remodeling in PAH. Genetic and pharmacologic correction of aberrant ROR2 signaling restores pericyte function, supporting ROR2 as a promising therapeutic target to preserve microvascular homeostasis and attenuate PAH progression. This abstract is funded by: NIH