Abstract Body (Do not enter title and authors here): Introduction: Pulmonary hypertension (PH) is a fatal cardiovascular disease marked by extensive vascular remodeling. Pericytes, crucial for capillary function and typically associated with endothelial cells (ECs), are dysfunctional in PH and contribute significantly to vascular remodeling. Our research indicates that Aminopeptidase-N (APN) is overexpressed in the lungs of PH patients, contributing to pericyte proliferation, although the underlying mechanisms remain unclear. We recently discovered elevated stratifin (SFN) levels in the ECs of PH patients. SFN is known to interact with proteins like APN and activate downstream signaling pathways.

Hypothesis: We hypothesize that elevated SFN binds to pericyte APN, triggering a pathological proliferative response.

Methods: We utilized rats with the NFU1 (G208C) mutation, which develop spontaneous PH characterized by severe vascular remodeling and increased right ventricular systolic pressure (RVSP). To analyze cell phenotype shifts, we employed scRNA-seq and confocal imaging. Additionally, we used R18, a peptide that inhibits SFN activation of downstream targets, to explore if targeting SFN reverses PH.
Results: We found elevated circulating SFN levels in PH patient plasma and observed high SFN expression and secretion in isolated ECs from PH patients. NFU1 rats mirrored these findings, showing significantly elevated SFN expression and secretion in ECs. Similarly, increased APN was found in both the lungs of PH patients and the isolated pericytes of NFU1 rats. scRNA-seq followed by Cell-Chat interaction analysis revealed that NFU1 pericytes had reduced interactions with ECs. Additionally, scRNA-seq indicated a shift to a "smooth muscle cell-like" phenotype in pericytes, characterized by increased calponin-3 and SMMHC expression. Confocal imaging confirmed significant disruption of pericyte-EC connections in NFU1 rats. Treatment with R18 in NFU1 rats significantly reversed vascular remodeling and RVSP. Echocardiography showed that R18 significantly improved the ratio of pulmonary acceleration to pulmonary ejection time. Furthermore, scRNA-seq demonstrated that R18 treatment improved pericyte-EC connections and regulated the pericyte phenotype shift in NFU1 rats.

Conclusions: Endothelial stratifin induces a phenotype shift in pericytes, leading to vascular remodeling and PH. Targeting SFN signaling presents a novel strategy to combat PH.