Decoding the fibroblast-endothelial dialogue in pulmonary hypertension assiociated with cardiometabolic HFpEF

Abstract Background Pulmonary hypertension (PH) is a frequent complication of heart failure with preserved ejection fraction (HFpEF), associated with greater symptom burden and worse outcomes than HFpEF alone. Beyond hemodynamic stress, growing evidence indicates that alterations in the lung microenvironment, driven by dysfunctional cellular populations, contribute to pulmonary microvascular damage and PH progression. Epigenetic mechanisms have emerged as potential therapeutic targets in cardiometabolic disease, with selective epigenetic drugs capable of restoring vascular homeostasis and preventing PH development in cardiometabolic HFpEF (HFpEF-PH). Purpose To characterise lung microenvironmental alterations in HFpEF-PH and evaluate the therapeutic potential of the BET inhibitor Apabetalone (APA, RVX-208) in preventing PH development. Methods Male C57BL/6J mice were fed either a control diet (CD) or a high-fat diet (HFD) combined with L-NAME for 21 weeks to induce HFpEF-PH. A subgroup of HFpEF-PH mice received APA for 21 days. Cardiac function and pulmonary hemodynamics were assessed by high-resolution echocardiography(Vevo 3100, VisualSonics). Lung tissue was analysed by single-nucleus RNA sequencing (snRNA-seq). Primary pulmonary endothelial cells (mECs) and fibroblasts (mFBs) were isolated for molecular, metabolic, and autophagic profiling. Paracrine signalling was evaluated using conditioned-media co-culture assays. Autophagic flux was assessed by transmission electron microscopy and protein analysis, and pharmacological modulation with APA was tested in vitro for 48 hours. Results HFpEF mice developed PH, as indicated by increased pulmonary artery pressure, resistance, and right ventricular hypertrophy, together with reduced pulmonary artery acceleration time. snRNA-seq identified fibroblasts and endothelial cells as the most transcriptionally dysregulated populations, with expansion of two activated myofibroblast subsets and upregulation of AP1 complex genes (c-Fos, c-Jun, JunD). Isolated mFBs exhibited a myofibroblastic and metabolically reprogrammed phenotype, while mECs displayed inflammatory activation, oxidative stress, and impaired autophagy, confirmed by accumulation of immature autophagosomes. Interactome analyses revealed mFBs as the main source of intercellular signals in HFpEF-PH lungs. Exposure of CD-mECs to conditioned media from HFpEF-PH fibroblasts reproduced endothelial dysfunction, supporting a paracrine, AP1-mediated mechanism of injury. In vitro APA treatment rescued mEC and mFB transcriptional alterations and functional defects, while in vivo APA administration prevented PH development in HFpEF mice.Conclusions: Lung microenvironmental remodelling in HFpEF-PH—driven by fibroblast–endothelial crosstalk and autophagy impairment—promotes pulmonary vascular dysfunction. Epigenetic modulation with Apabetalone restores cellular homeostasis and prevents PH onset, identifying a novel therapeutic strategy for cardiometabolic HFpEF-PH.For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.