Faidel, D. | Search bioRxiv

bioRxiv2026

Lung microvascular rarefaction impairs pulmonary gas exchange and exacerbates heart failure with preserved ejection fraction

BackgroundDyspnea and exercise intolerance are the primary clinical symptoms of heart failure. Heart failure patients experience frequent hypoxemic episodes, yet underlying mechanisms and relevance remain poorly understood. In a cohort of heart failure patients and multiple animal models, we identify pulmonary capillary rarefaction driven by excessive autophagy in endothelial cells as a novel mechanism of hypoxemia and cardiac disease progression. MethodsA cohort of heart failure with preserved ejection fraction (HFpEF) patients was analyzed for parameters of left ventricular (LV) dysfunction and pulmonary gas exchange. Morphological and cellular mechanisms of impaired pulmonary oxygenation were assessed in three animal models of heart failure, namely two HFpEF models, SU5416-treated ZSF1 obese rats and high fat diet/L-NAME treated mice, and in rats subjected to aortic banding. Lung microvascular rarefaction was quantified by micro-computed tomography, stereology, flow cytometry and dye efflux. Cellular mechanisms of capillary loss were analyzed by single-cell transcriptomics, electron microscopy and immunofluorescence, and in mice with endothelial-specific deletion of the autophagy gene Atg7 (Atg7EN-KO). ResultsIn 234 HFpEF patients, advancing NYHA class was associated with progressive worsening of arterial oxygen saturation at rest and during exercise and a reduced lung diffusing capacity. Impaired gas diffusion correlated with indices of LV diastolic dysfunction. Impaired oxygenation and reduced exercise capacity were similarly evident in animal models of left heart disease, which showed a distinct loss of pulmonary microvessels and capillaries. Lung microvascular endothelial cells in HFpEF showed characteristics of increased autophagic flux and apoptosis. Relative to their wild type HFpEF controls, Atg7EN-KO mice had less capillary loss, restored normoxemia, improved exercise tolerance, and mitigated LV diastolic dysfunction. Additional studies in HFpEF mice corroborated the functional relevance of impaired gas exchange for the progression of left heart disease by demonstrating that additional hypoxia aggravated, whereas moderate hyperoxia improved LV function. ConclusionOur findings identify pulmonary microvascular rarefaction as a novel pathomechanism in heart failure that i) contributes to dyspnea and exercise intolerance, ii) impairs pulmonary gas exchange and iii) accelerates LV disease progression. Strategies targeting this axis such as moderate oxygen therapy may mitigate cardiopulmonary morbidity in heart failure. Clinical Trial RegistrationRegistered in the DRKS (Deutsches Register fur klinische Studien) as trial# DRKS00032974 at https://drks.de/search/en/trial/DRKS00032974.

physiology↗

bioRxiv2025

Myeloid cell recruitment propels right ventricular dysfunction in HFpEF via sterile inflammation.

BackgroundIn contrast to what has already been shown in HFpEF associated left ventricular (LV) diastolic dysfunction, leukocytes role in frequently occurring right ventricular dysfunction (RVD) secondary to HFpEF are so far missing, partially due to the lack of suitable small animal models. Here, we follow a translational research approach by establishing a murine HFpEF model developing manifest RVD and analyzed human HFpEF cohorts to study the mechanistic link between leukocytes and RVD in HFpEF. Methods8-week-old male and female C57BL/6J or Cx3cr1CreER/+R26tdTomato/+ mice were divided into four experimental groups: i) chow, ii) HFpEF (N[{omega}]-nitro-l-arginine methyl ester (L-NAME), 60% high-fat diet), iii) chronic hypoxia (10% O2) and iv) HFpEF and hypoxia (RV-HFpEF) to assess bi-ventricular function and myeloid cell dynamics. To test whether myeloid cells are causally involved in the development of RV remodeling in HFpEF, we additionally treated RV-HFpEF mice with the colony stimulating factor 1 receptor inhibitor PLX-5622 (PLX) to deplete myeloid cells. After 12 weeks, all experimental groups were subjected to transthoracic echocardiography, invasive hemodynamics or flow cytometry. ResultsRV-HFpEF resulted in LV diastolic dysfunction indicated by increased E/E ratio, reduced global longitudinal peak strain, smaller end-diastolic diameters and increased isovolumetric relaxation time compared to chow. RV-HFpEF animals developed RV hypertrophy and RVD evident as increased Fultons index and collagen content as well as elevated RV systolic pressures (RVSPs) and reduced tricuspid annular plane systolic excursion, respectively. Flow cytometric analyses revealed elevated total leukocyte, monocyte, and macrophage counts in RV tissue of RV-HFpEF compared to chow or LV tissue from RV-HFpEF animals. These data were confirmed by unbiased proteomic analyses of RV tissue from RV-HFpEF mice, demonstrating increased abundance of proteins involved in activation of the innate immune system, macrophage chemotaxis, cell adhesion and extracellular matrix organization when compared to LV tissue or other experimental groups. Fate mapping experiments revealed that recruited monocyte-derived macrophages became the main source of total cardiac macrophages in RV tissue from RV-HFpEF mice. Depletion of myeloid cells was associated with rescued RVSP profiles compared to RV-HFpEF control mice. In HFpEF patients, RV dilation was associated with an increased percentage of circulating monocytes. In RV biopsies from HFpEF patients, we found increased expression of adhesion molecules, fibrotic markers and inflammatory transcripts. ConclusionWe demonstrate that dysregulated myeloid cell dynamics are associated with, and directly contribute to, the pathogenesis of HFpEF-associated RVD in humans and mice. Clinical PerspectiveWhat is new: O_LIWe explore myeloid cell dynamics in a novel three-hit experimental HFpEF mouse model with RV hypertrophy, RV end-systolic pressure and RV dysfunction. C_LIO_LIIn this model, RV dysfunction was associated with macrophage expansion, monocyte recruitment and extracellular matrix deposition, whilst macrophage depletion partly reversed these changes and rescued RV hemodynamics. C_LIO_LIHFpEF patients with RV dilation or RV dysfunction exhibit unique leukocyte dynamics and inflammatory profiles when compared to HFpEF patients with normal RV function or diameters. C_LI Clinical implications: O_LIThere exists a major clinical discrepancy between high incidence of RV dysfunction associated to HFpEF and a lack of targeted treatment strategies. C_LIO_LIOur novel three-hit mouse model recapitulates many features of the clinical scenario of HFpEF patients with RV dysfunction, therefore representing an important step towards systematic testing and development of targeted treatment options. C_LIO_LISterile inflammation and dysregulation of innate immune cells may be suitable targets for therapeutic interventions against RV dysfunction in HFpEF. C_LI

physiology↗