Digital Spatial Profiling Identifies Distinct Molecular Signatures of Vascular Lesions in Pulmonary Arterial Hypertension

Vascular EC-SOD limits the accumulation, proinflammatory profibrotic reprogramming, and hyaluronan binding of interstitial macrophages in hypoxia

Dysregulated redox signaling contributes to pulmonary hypertension (PH) and vascular depletion of the redox enzyme extracellular superoxide dismutase (EC-SOD) from smooth muscle cells [EC-SOD SMC knockout (KO)] worsens chronic hypoxic PH. Given the important role of macrophages in PH, this study aimed to determine if interstitial macrophages (IMs) and their interactions with hyaluronan (HA), a component of extracellular matrix (ECM), are modulated by vascular EC-SOD. Floxed wild-type, EC-SOD SMC KO, and SOD mimetic- or vehicle-treated mice were exposed to hypobaric hypoxia [∼10% fraction of inspired oxygen ([Formula: see text])], for 4, 14, or 21 days. Using flow cytometry, we demonstrated that the transient increase in IMs at day 4 was exacerbated in EC-SOD SMC KO mice and prevented with SOD mimetic pretreatment. Highlighting the importance of targeting vascular oxidative stress in the early response to hypoxia, pretreatment with a single dose of EC-SOD mimetic decreased right ventricular systolic pressure, right ventricular hypertrophy, and small vessel muscularization at day 21. To assess IM phenotypic reprogramming in hypoxia, RNA-seq was performed on flow-sorted IMs revealing baseline proinflammatory activation and enhanced activation of vascular and ECM remodeling pathways in response to hypoxia in EC-SOD SMC KO IMs compared with controls. To further investigate the ECM remodeling response, we quantified IMs expressing the lymphatic vessel endothelial hyaluronan receptor 1 (Lyve1), and IM-hyaluronan binding. Lyve1+ IMs and Lyve1+ HA+ IMs were increased in response to hypoxia in EC-SOD SMC KO mice and accumulated in the perivascular space of the lung. In conclusion, vascular EC-SOD limits IM accumulation and proinflammatory profibrotic IM signaling, including perivascular accumulation of Lyve1+ IMs and their binding to hyaluronan.NEW & NOTEWORTHY Expression of the redox enzyme EC-SOD limits PH severity. Using vascular-selective EC-SOD depletion and SOD mimetic treatment in chronic hypoxic PH, we demonstrated that EC-SOD limits the hypoxia-induced accumulation of IMs. IMs from mice with low vascular EC-SOD were proinflammatory at baseline and enhanced ECM remodeling pathway activation in response to hypoxia. We identified Lyve1+ IMs as a perivascular, ECM-interacting subset that accumulate in hypoxia and could contribute to vascular remodeling in PH.

Lung endothelial cell heterogeneity in health and pulmonary vascular disease

Lung endothelial cells (ECs) are essential for maintaining organ function and homeostasis. Despite sharing some common features with ECs from organ systems, lung ECs exhibit significant heterogeneity in morphology, function, and gene expression. This heterogeneity is increasingly recognized as a key contributor to the development of pulmonary diseases like pulmonary hypertension (PH). In this mini-review, we explore the evolving understanding of lung EC heterogeneity, particularly through the lens of single-cell RNA sequencing (scRNA-seq) technologies. These advances have provided unprecedented insights into the diverse EC subpopulations, their specific roles, and the disturbances in their homeostatic functions that contribute to PH pathogenesis. In particular, these studies identified novel and functionally distinct cell types such as aerocytes and general capillary ECs that are critical for maintaining lung function in health and disease. In addition, multiple novel pathways and mechanisms have been identified that contribute to aberrant pulmonary vascular remodeling in PH. Emerging techniques like single-nucleus RNA sequencing and spatial transcriptomics have further pushed the field forward by discovering novel disease mediators. As research continues to leverage these advanced techniques, the field is poised to uncover novel EC subtypes and disease mechanisms, paving the way for new therapeutic targets in PH and other lung diseases.

Nbeal2 knockout mice are not protected against hypoxia-induced pulmonary vascular remodeling and pulmonary hypertension

ABSTRACT

Inflammation drives the initiation and progression of pulmonary hypertension (PH). Platelets, increasingly recognized as immune cells, are activated and increased in the lungs of patients with PH. Platelet activation leads to the release of α-granule chemokines, many of which are implicated in PH. We hypothesized that hypoxia-induced secretion of platelet α-granule-stored proteins and PH would be prevented in Neurobeachin-like 2 knockout (Nbeal2-/-) α-granule-deficient mice. Wild-type (WT) and Nbeal2-/- mice were maintained in normoxia or exposed to 10% hypobaric hypoxia for 3, 14, 21, or 35 days. We observed macrothrombocytopenia, increased circulating neutrophils and monocytes, and increased lung interstitial macrophages (IMs) in Nbeal2-/- mice at baseline. Hypoxia-induced platelet activation was attenuated, and hypoxia-induced increase in lung platelet factor 4 (PF4) and platelets was delayed in Nbeal2-/- mice compared with in WT mice. Finally, although pulmonary vascular remodeling (PVR) and PH were attenuated at day 21, Nbeal2-/- mice were not protected against hypoxia-induced PVR and PH at day 35. Although this mutation also affected circulating monocytes, neutrophils, and lung IMs, all of which are critical in the development of experimental PH, we gained further support for the role of platelets and α-granule proteins, such as PF4, in PH progression and pathogenesis and made several observations that expand our understanding of α-granule-deficient mice in chronic hypoxia.

An intracellular complement system drives metabolic and proinflammatory reprogramming of vascular fibroblasts in pulmonary hypertension

The complement system is central to the innate immune response, playing a critical role in proinflammatory and autoimmune diseases such as pulmonary hypertension (PH). Recent discoveries highlight the emerging role of intracellular complement, or the "complosome," in regulating cellular processes such as glycolysis, mitochondrial dynamics, and inflammatory gene expression. This study investigated the hypothesis that intracellular complement proteins C3, CFB, and CFD are upregulated in PH fibroblasts (PH-Fibs) and drive their metabolic and inflammatory states, contributing to PH progression. Our results revealed a pronounced upregulation of CFD, CFB, and C3 in PH-Fibs from human samples and bovine models, both in vivo and in vitro. The finding of elevated levels of C3 activation fragments, including C3b, C3d, and C3a, emphasized enhanced C3 activity. PH-Fibs exhibited notable metabolic reprogramming and increased levels of proinflammatory mediators such as MCP1, SDF1, IL-6, IL-13, and IL-33. Silencing CFD via shRNA reduced CFB activation and C3a production, while normalizing glycolysis, tricarboxylic acid (TCA) cycle activity, and fatty acid metabolism. Metabolomic and gene expression analyses of CFD-knockdown PH-Fibs revealed restored metabolic and inflammatory profiles, underscoring CFD's crucial role in these changes. This study emphasizes the crucial role of intracellular complement in PH pathogenesis, highlighting the potential for complement-targeted therapies in PH.

Precision Medicine for Pulmonary Vascular Disease: The Future Is Now (2023 Grover Conference Series)

Pulmonary vascular disease is not a single condition; rather it can accompany a variety of pathologies that impact the pulmonary vasculature. Applying precision medicine strategies to better phenotype, diagnose, monitor, and treat pulmonary vascular disease is increasingly possible with the growing accessibility of powerful clinical and research tools. Nevertheless, challenges exist in implementing these tools to optimal effect. The 2023 Grover Conference Series reviewed the research landscape to summarize the current state of the art and provide a better understanding of the application of precision medicine to managing pulmonary vascular disease. In particular, the following aspects were discussed: (1) Clinical phenotypes, (2) genetics, (3) epigenetics, (4) biomarker discovery, (5) application of precision biology to clinical trials, (6) the right ventricle (RV), and (7) integrating precision medicine to clinical care. The present review summarizes the content of these discussions and the prospects for the future.

Interplay of Transcriptomic Regulation, Microbiota, and Signaling Pathways in Lung and Gut Inflammation-Induced Tumorigenesis

Inflammation can positively and negatively affect tumorigenesis based on the duration, scope, and sequence of related events through the regulation of signaling pathways. A transcriptomic analysis of five pulmonary arterial hypertension, twelve Crohn's disease, and twelve ulcerative colitis high throughput sequencing datasets using R language specialized libraries and gene enrichment analyses identified a regulatory network in each inflammatory disease. IRF9 and LINC01089 in pulmonary arterial hypertension are related to the regulation of signaling pathways like MAPK, NOTCH, human papillomavirus, and hepatitis c infection. ZNF91 and TP53TG1 in Crohn's disease are related to the regulation of PPAR, MAPK, and metabolic signaling pathways. ZNF91, VDR, DLEU1, SATB2-AS1, and TP53TG1 in ulcerative colitis are related to the regulation of PPAR, AMPK, and metabolic signaling pathways. The activation of the transcriptomic network and signaling pathways might be related to the interaction of the characteristic microbiota of the inflammatory disease, with the lung and gut cell receptors present in membrane rafts and complexes. The transcriptomic analysis highlights the impact of several coding and non-coding RNAs, suggesting their relationship with the unlocking of cell phenotypic plasticity for the acquisition of the hallmarks of cancer during lung and gut cell adaptation to inflammatory phenotypes.

Pathology and pathobiology of pulmonary hypertension: current insights and future directions

In recent years, major advances have been made in the understanding of the cellular and molecular mechanisms driving pulmonary vascular remodelling in various forms of pulmonary hypertension, including pulmonary arterial hypertension, pulmonary hypertension associated with left heart disease, pulmonary hypertension associated with chronic lung disease and hypoxia, and chronic thromboembolic pulmonary hypertension. However, the survival rates for these different forms of pulmonary hypertension remain unsatisfactory, underscoring the crucial need to more effectively translate innovative scientific knowledge into healthcare interventions. In these proceedings of the 7th World Symposium on Pulmonary Hypertension, we delve into recent developments in the field of pathology and pathophysiology, prioritising them while questioning their relevance to different subsets of pulmonary hypertension. In addition, we explore how the latest omics and other technological advances can help us better and more rapidly understand the myriad basic mechanisms contributing to the initiation and progression of pulmonary vascular remodelling. Finally, we discuss strategies aimed at improving patient care, optimising drug development, and providing essential support to advance research in this field.

Classical dendritic cells contribute to hypoxia-induced pulmonary hypertension

Pulmonary hypertension (PH) is a chronic and progressive disease with significant morbidity and mortality. It is characterized by remodeled pulmonary vessels associated with perivascular and intravascular accumulation of inflammatory cells. Although there is compelling evidence that bone marrow-derived cells, such as macrophages and T cells, cluster in the vicinity of pulmonary vascular lesions in humans and contribute to PH development in different animal models, the role of dendritic cells in PH is less clear. Dendritic cells' involvement in PH is likely since they are responsible for coordinating innate and adaptive immune responses. We hypothesized that dendritic cells drive hypoxic PH. We demonstrate that a classical dendritic cell (cDC) subset (cDC2) is increased and activated in wild-type mouse lungs after hypoxia exposure. We observe significant protection after the depletion of cDCs in ZBTB46 DTR chimera mice before hypoxia exposure and after established hypoxic PH. In addition, we find that cDC depletion is associated with a reduced number of two macrophage subsets in the lung (FolR2+ MHCII+ CCR2+ and FolR2+ MHCII+ CCR2-). We found that depleting cDC2s, but not cDC1s, was protective against hypoxic PH. Finally, proof-of-concept studies in human lungs show increased perivascular cDC2s in patients with Idiopathic Pulmonary Arterial Hypertension (IPAH). Our data points to an essential role of cDCs, particularly cDC2s, in the pathophysiology of experimental PH.

Deciphering the Complexities of Pulmonary Hypertension: The Emergent Role of Single-Cell Omics

Expanding upon the critical advancements brought forth by single-cell omics in pulmonary hypertension (PH) research, this review delves deep into how these technologies have been piloted in a new era of understanding this complex disease. By leveraging the power of single cell transcriptomics (scRNA-seq), researchers can now dissect the complicated cellular ecosystem of the lungs, examining the key players such as endothelial cells, smooth muscle cells, pericytes, and immune cells, and their unique roles in the pathogenesis of PH. This more granular view is beyond the limitations of traditional bulk analysis, allowing for the identification of novel therapeutic targets previously obscured in the aggregated data. Connectome analysis based on single-cell omics of the cells involved in pathological changes can reveal a clearer picture of the cellular interactions and transitions in the cellular subtypes. Furthermore, the review acknowledges the challenges that lie ahead, including the need for enhancing the resolution of scRNA-seq to capture even finer details of cellular changes, overcoming logistical barriers in processing human tissue samples, and the necessity of integrating diverse omics approaches to fully comprehend the molecular underpinnings of PH. The promise of these single-cell technologies is immense, offering the potential for targeted drug development and the discovery of biomarkers for early diagnosis and disease monitoring. Through these advancements, the field moves closer to realizing the goal of precision medicine for patients with PH.