Single cell transcriptomic analyses reveal diverse and dynamic changes of distinct populations of lung interstitial macrophages in hypoxia-induced pulmonary hypertension

Front Immunol. 2024 Apr 15:15:1372959. doi: 10.3389/fimmu.2024.1372959. eCollection 2024.

Abstract

Introduction: Hypoxia is a common pathological driver contributing to various forms of pulmonary vascular diseases leading to pulmonary hypertension (PH). Pulmonary interstitial macrophages (IMs) play pivotal roles in immune and vascular dysfunction, leading to inflammation, abnormal remodeling, and fibrosis in PH. However, IMs' response to hypoxia and their role in PH progression remain largely unknown. We utilized a murine model of hypoxia-induced PH to investigate the repertoire and functional profiles of IMs in response to acute and prolonged hypoxia, aiming to elucidate their contributions to PH development.

Methods: We conducted single-cell transcriptomic analyses to characterize the repertoire and functional profiles of murine pulmonary IMs following exposure to hypobaric hypoxia for varying durations (0, 1, 3, 7, and 21 days). Hallmark pathways from the mouse Molecular Signatures Database were utilized to characterize the molecular function of the IM subpopulation in response to hypoxia.

Results: Our analysis revealed an early acute inflammatory phase during acute hypoxia exposure (Days 1-3), which was resolved by Day 7, followed by a pro-remodeling phase during prolonged hypoxia (Days 7-21). These phases were marked by distinct subpopulations of IMs: MHCIIhiCCR2+EAR2+ cells characterized the acute inflammatory phase, while TLF+VCAM1hi cells dominated the pro-remodeling phase. The acute inflammatory phase exhibited enrichment in interferon-gamma, IL-2, and IL-6 pathways, while the pro-remodeling phase showed dysregulated chemokine production, hemoglobin clearance, and tissue repair profiles, along with activation of distinct complement pathways.

Discussion: Our findings demonstrate the existence of distinct populations of pulmonary interstitial macrophages corresponding to acute and prolonged hypoxia exposure, pivotal in regulating the inflammatory and remodeling phases of PH pathogenesis. This understanding offers potential avenues for targeted interventions, tailored to specific populations and distinct phases of the disease. Moreover, further identification of triggers for pro-remodeling IMs holds promise in unveiling novel therapeutic strategies for pulmonary hypertension.

Keywords: complement; hypoxia; inflammation; interstitial macrophages; pulmonary hypertension; vascular remodeling.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Disease Models, Animal
  • Gene Expression Profiling*
  • Hypertension, Pulmonary* / etiology
  • Hypertension, Pulmonary* / genetics
  • Hypertension, Pulmonary* / immunology
  • Hypoxia* / immunology
  • Hypoxia* / metabolism
  • Lung / immunology
  • Lung / metabolism
  • Lung / pathology
  • Macrophages, Alveolar / immunology
  • Macrophages, Alveolar / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Single-Cell Analysis*
  • Transcriptome*

Grants and funding

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. The authors appreciate funding support provided by the National Institutes of Health P01HL152961 (to KS and BG), K08-HL121185 (to Y-RY), R03-HL158640 (to Y-RY), and institutional support by the University of Colorado, Division of Pulmonary and Critical Care Sciences (to CM, TA, and Y-RY). Additionally, the authors acknowledge funding support from the U.S. Department of Defense, with grant numbers W81XWH1910259 and W81XWH2010249 (to KS). Furthermore, the authors acknowledge funding support from American Heart Association Grant 19CDA34730030 (to RK), ATS Foundation/Pulmonary Hypertension Association Research Fellowship (to RK), and United Therapeutics Jenesis Innovative Research Award (to RK); NIH grants R01HL135872 (to BG).