Single-Cell and Spatial Transcriptomics Identified Fatty Acid–Binding Proteins Controlling Endothelial Glycolytic and Arterial Programming in Pulmonary Hypertension

Rationale: Pulmonary arterial hypertension (PAH) is a devastating 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. Objectives: To determine whether upregulation of fatty-acid binding protein 4 and 5 (FABP4/5) is critical in pathogenesis of PAH. Methods: FABP4/5 expression was examined in pulmonary arterial endothelial cells (PAECs) and lung tissues from patients with idiopathic PAH and pulmonary hypertension (PH) rat models. Plasma proteome analysis was performed in human PAH samples. Echocardiography, hemodynamics, histology, and immunostaining were performed to evaluate the lung and heart PH phenotypes in Egln1Tie2Cre (CKO) mice and Egln1Tie2Cre/Fabp4-5-/- (TKO) mice. Measurement and Main Results: Both FABP4 and FABP5 were highly induced in ECs of CKO mice and PAECs from IPAH patients, and in whole lungs of PH rats. Plasma levels of FABP4/5 were upregulated in IPAH patients and directly correlated with severity of hemodynamics and biochemical parameters. Genetic deletion of both Fabp4 and 5 in CKO mice caused a reduction of right ventricular systolic pressure (RVSP) and RV hypertrophy, attenuated pulmonary vascular remodeling and prevented the right heart failure. Fabp4/5 deletion also normalized EC glycolysis, reduced ROS and HIF-2a expression, and decreased aberrant EC proliferation in CKO lungs. Conclusions: PH causes aberrant expression of FABP4/5 in pulmonary ECs which leads to enhanced EC glycolysis and hyperproliferation, contributing to the accumulation of arterial ECs and vascular remodeling and exacerbating the disease. Total RNA was isolated from lung tissue from WT, CKO (Egln1Tie2Cre) and TKO (Egln1Tie2Cre/Fabp4-5-/-) mice with Zymo Research Quick-RNA Miniprep Kits with DNase I digestion. RNA sequencing was carried out at the Novogene Corporation Inc. All samples were sequenced with an Illumina Novaseq 6000 platform with a pair end 150-bp read length.