Single-Cell Study of Two Rat Models of Pulmonary Arterial Hypertension Reveals Connections to Human Pathobiology and Drug Repositioning

Deciphering immune cell heterogeneity in vascular diseases: Insights from single-cell sequencing

The complexity and diversity of vascular diseases highlight the urgent need to study their pathogenesis, particularly the key role of immune cell-mediated inflammatory responses in their development. While previous reviews have outlined the involvement of immune cells in vascular pathology, a comprehensive understanding of their dynamic changes, functional states, and intercellular interactions remains incomplete. Recent advances in single-cell sequencing (SCS) have provided unprecedented insights into immune cell heterogeneity, enabling the identification of novel subpopulations and their roles in disease progression.This review extends prior work by systematically summarizing the latest applications of SCS in vascular diseases, highlighting newly discovered immune cell subsets, their interactions, and their impact on vascular pathology. By addressing current gaps in the literature-such as the functional plasticity of immune cells and their temporal dynamics-this review offers new perspectives on immune-mediated mechanisms in vascular diseases and proposes novel therapeutic strategies for their prevention and treatment.

MHCIIhiLYVE1loCCR2hi Interstitial Macrophages Promote Medial Fibrosis in Pulmonary Arterioles and Contribute to Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is a lethal disease characterized in part by progressive pulmonary arteriole (PA) remodeling. Excessive PA fibrosis and macrophage infiltration are often present in PH, but the potential associations are obscure. We investigated the link between interstitial macrophage (iMΦ) infiltration and PA fibrosis in PH and idiopathic pulmonary arterial hypertension.

METHODS

Lung tissue samples from patients with idiopathic pulmonary arterial hypertension and experimental PH animals were obtained to analyze the extent of fibrosis and iMΦ infiltration in the different layers of PAs and their correlation with disease severity. Single-cell RNA sequencing, lineage tracing, histological analyses, iMΦ and PA smooth muscle cell coculture, and transgenic animal experiments were used to investigate the cell heterogeneity and origins and molecular mechanisms by which iMΦs promote PA fibrosis.

RESULTS

We found that increased collagen deposition and fibrosis in the PA media were most strongly related to the severity of PH, and medial iMΦ infiltration may be involved in these pathological processes. Single-cell transcriptomics revealed that MHCIIhiLYVE1loCCR2hi iMΦs were the major type of iMΦ that expanded upon Sugen-5416 and hypoxia plus normoxia stimulation and were responsible for PA medial fibrosis. Lineage tracing experiments suggested that these medial iMΦs were largely from recruited monocytes. Mechanistically, MHCIIhiLYVE1loCCR2hi iMΦs promoted the transition of PA smooth muscle cells to a fibroblast-like phenotype through the WNT11 (wingless member 11)/planar cell polarity (PCP) pathway. Wnt11 deletion in iMΦs from PH rats normalized the fibrotic PA smooth muscle cell phenotype and decreased PA medial fibrosis, thereby improving vascular compliance and protecting against PH. Moreover, myeloid-specific Ccr2 deficiency in PH-PAs inhibited the medial infiltration of MHCIIhiLYVE1loCCR2hi iMΦs, which also relieved PH.

CONCLUSIONS

This study demonstrates that the recruitment of MHCIIhiLYVE1loCCR2hi iMΦs leads to medial fibrosis in PH-PAs associated with PH severity and that inhibition of their pathogenicity or recruitment reverses PA medial fibrosis and PH.

Chronic intermittent hypobaric hypoxia prevents pulmonary arterial hypertension through maintaining eNOS homeostasis

AIMS

Pulmonary arterial hypertension (PAH) is a pathological condition in which pulmonary artery pressure is elevated which causes patients to die of right heart failure. Chronic intermittent hypobaric hypoxia (CIHH) represents a novel method of intermittently exposing subjects to a simulated plateau hypobaric hypoxia environment. This study investigates the potential preventive and protective effects of CIHH on PAH.

MAIN METHODS

Male Sprague-Dawley rats were randomly divided into four groups: control group (Con), chronic intermittent hypobaric hypoxia group (CIHH), pulmonary arterial hypertension group (PAH), chronic intermittent hypobaric hypoxia + pulmonary arterial hypertension group (CIHH + PAH). To evaluate the effects of CIHH on PAH, a range of techniques was employed, including pulmonary hemodynamics, vascular reactivity assay, Western blot, RNA sequencing, HE staining and co-immunoprecipitation.

KEY FINDINGS

CIHH was demonstrated to reduce pulmonary artery constriction and enhance relaxation, reducing the mean pulmonary artery pressure in PAH rats. This is achieved through attenuating the CaM/eNOS (Calmodulin,CaM)protein interaction and increasing the CaV1/eNOS (Caveolin-1,CaV1) protein interaction, thereby preventing eNOS overactivation contribution to improving NO bioavailability in PAH rats.

SIGNIFICANCE

CIHH prevents PAH by maintaining eNOS homeostasis in PAH rats.

Deficiency of Endothelial Piezo2 Impairs Pulmonary Vascular Angiogenesis and Predisposes Pulmonary Hypertension

BACKGROUND

Mechanosensitive Piezo1 (Piezo Type Mechanosensitive Ion Channel Component 1) channel plays a key role in pulmonary hypertension (PH). However, the role of Piezo2 in PH remains unclear.

METHODS

Endothelial cell (EC)-specific Piezo2 knockout (Piezo2flox/flox, Tek-Cre+; Piezo2EC-/-) rats and primarily cultured pulmonary microvascular ECs were used to determine the role of Piezo2 in PH.

RESULTS

Data analysis of publicly accessible single-cell RNA-sequencing data sets uncovered significant downregulation of Piezo2 in lung ECs from patients with idiopathic pulmonary arterial hypertension, which was verified in the lungs/ECs from PH rat models induced by hypoxia or monocrotaline. Comparing to wild-type rats, Piezo2EC-/- rats exhibited exacerbated PH in both hypoxia-induced PH and monocrotaline-induced PH, characterized by the worsened hemodynamical and histological changes. Piezo2EC-/- rats showed dramatic loss of pulmonary microvessels, in association with the decreased intracellular free calcium concentration ([Ca2+]i) and downregulation of VEGFR2 (vascular endothelial growth factor receptor 2) and phosphorylated SRF (serum response factor) in pulmonary microvascular ECs. Knockout of Piezo2 or treatment with a calcium chelator, EDTA, impaired the ability of tube formation and migration in pulmonary microvascular ECs, which was restored by supplementation of extra calcium. A safflower oil diet rich in linoleic acid, which can enhance the stability and function of Piezo2, effectively alleviated PH development in a hypoxia-induced PH rat model.

CONCLUSIONS

This study demonstrates that EC-specific knockout of Piezo2 exacerbates PH pathogenesis, at least partially, through the suppression of [Ca2+]i/phosphorylated SRF/VEGFR2 signaling axis in pulmonary vascular ECs. Targeted activation of Piezo2 could be a novel effective strategy for the treatment of PH.

New insights into the effects of PFOS exposure on rat lung development: morphological, functional, and single-cell sequencing analysis

Perfluorooctane sulfonate (PFOS), a widely persistent environmental pollutant, has been demonstrated to disrupt lung development in animal models. However, its cellular and molecular mechanisms remain insufficiently understood. This study examines the effects of prenatal PFOS exposure on lung development and function in offspring rats. Pregnant rats were exposed to PFOS at concentrations relevant to both environmental and occupational exposures, with doses of 0, 0.01, 0.1, and 1 mg/kg/day from gestational day 11-20. We primarily evaluated morphological changes, pulmonary function, bronchoalveolar lavage fluid composition, and alterations in trace element and fatty acid metabolism at postnatal days 0, 4, 14, 21, and 60. Single-cell RNA sequencing was employed to profile cellular and molecular responses in the lungs. Our results show that PFOS exposure leads to dose-dependent reductions in alveolar development, increased pulmonary injury, fibrosis, and impaired lung function. PFOS also changes lung cell composition, particularly affecting structural and immune cells, and shifts immune responses from innate to adaptive immunity. Differential gene expression analyses revealed the upregulation of Fam111a and downregulation of Stk35, implicating these genes in PFOS-induced lung injury and repair processes. In addition, pathway analyses demonstrated suppression of immune-related signaling pathways and disruption of cell adhesion and phagocytosis, which may exacerbate lung tissue injury. These findings provide novel insights into the developmental toxicity of PFOS and highlight its potential long-term health risks.

RPL39 Was Associated With Sex Differences in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a malignant cardiovascular disease with a complex etiology, in which several types of cells play important roles. Sex differences in disease susceptibility and survival have been observed in PAH patients, but few studies have analyzed the effect of changes in cell type and number on sex differences in PAH at the single-cell level. In this study, we performed a series of analyses on GSE169471 and GSE228644 datasets and found significant changes in the ratio of several types of cells in male PAH lung tissues. Surprisingly, we found that the ratio of macrophages in male PAH samples was 7 times higher than that in females. Consistently, the ratio of M1 macrophages was also significantly increased in male PAH samples. The different expression genes (DEGs) in macrophages were mainly involved in the ribosome pathway, which is closely related to cell proliferation. Inhibition of ribosomal protein L39 (RPL39), a core gene in the ribosome pathway, can inhibit macrophage proliferation and attenuate the sex differences in PAH. In conclusion, our study suggests that ribosome pathway-associated cell proliferation of macrophages might be associated with sex differences in PAH.

Network pharmacology provides new insights into the mechanism of traditional Chinese medicine and natural products used to treat pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) is a rare cardiovascular disease with high morbidity and mortality rates. It is characterized by increased pulmonary arterial pressure. Current research into relevant therapeutic drugs and targets for PH, however, is insufficient still. Traditional Chinese medicine (TCM) and natural products have a long history as therapeutics for PH. Network pharmacology is an approach that integrates drug-target interactions and signaling pathways based on biomarkers information obtained from drug and disease databases. The concept of network pharmacology shows many similarities with the TCM philosophy. Network pharmacology help elucidate the mechanisms of TCM in PH. This review presents representative applications of network pharmacology in the study of the mechanisms of TCM and natural products for the treatment of PH.

METHODS

In this review, we used ("pulmonary hypertension" OR "pulmonary arterial hypertension" OR "chronic thromboembolic pulmonary hypertension") AND ("network pharmacology" OR "systematic pharmacology") as keywords to search for reports from PubMed, Web of Science, and Google Scholar databases from ten years ago. The studies were screened and those chosen are summarized here. The TCM and natural products inPH and their corresponding targets and signaling pathways are described. Additionally, we discuss the application of network pharmacology in the study of TCM in PH to provide insights for future application strategies.

RESULTS

Network pharmacology have shown that AKT-related pathways, HIF-1 signaling pathway, MAPK signaling pathway, TGF-β-Smad pathway, cell cycle-related pathways and inflammation-related pathways are the main signaling pathways enriched in the PH targets of TCM. Reservatrol, curcumol, genistin, formononetin, wogonin, luteolin, baicalein, berberine, triptolide and tanshinone llA are active ingredients specific for PH treatment. A number of databases and tools specific for the treatment of PH are used in network pharmacology and natural product research.

CONCLUSION

Through the reasonable combination of molecular docking, omics technology and bioinformatics technology, the mechanism of multi-targets can be explained more comprehensively. Analyzing the complex mechanism of TCM from the clinical perspective may be a potential development trend of network pharmacology. Combination of predicted targets and traditional pharmacology improves efficiency of drug development.

Ferroptosis-Mediated Inflammation Promotes Pulmonary Hypertension

BACKGROUND

Mitochondrial dysfunction, characterized by impaired lipid metabolism and heightened reactive oxygen species generation, results in lipid peroxidation and ferroptosis. Ferroptosis is an inflammatory mode of cell death that promotes complement activation and macrophage recruitment. In pulmonary arterial hypertension (PAH), pulmonary arterial endothelial cells exhibit cellular phenotypes that promote ferroptosis. Moreover, there is ectopic complement deposition and inflammatory macrophage accumulation in the pulmonary vasculature. However, the effects of ferroptosis inhibition on these pathogenic mechanisms and the cellular landscape of the pulmonary vasculature are incompletely defined.

METHODS

Multiomics and physiological analyses evaluated how ferroptosis inhibition-modulated preclinical PAH. The impact of adeno-associated virus 1-mediated expression of the proferroptotic protein ACSL (acyl-CoA synthetase long-chain family member) 4 on PAH was determined, and a genetic association study in humans further probed the relationship between ferroptosis and pulmonary hypertension.

RESULTS

Ferrostatin-1, a small-molecule ferroptosis inhibitor, mitigated PAH severity in monocrotaline rats. RNA-sequencing and proteomics analyses demonstrated ferroptosis was associated with PAH severity. RNA-sequencing, proteomics, and confocal microscopy revealed complement activation and proinflammatory cytokines/chemokines were suppressed by ferrostatin-1. In addition, ferrostatin-1 combatted changes in endothelial, smooth muscle, and interstitial macrophage abundance and gene activation patterns as revealed by deconvolution RNA-sequencing. Ferroptotic pulmonary arterial endothelial cell damage-associated molecular patterns restructured the transcriptomic signature and mitochondrial morphology, promoted the proliferation of pulmonary artery smooth muscle cells, and created a proinflammatory phenotype in monocytes in vitro. Adeno-associated virus 1-Acsl4 induced an inflammatory PAH phenotype in rats. Finally, single-nucleotide polymorphisms in 6 ferroptosis genes identified a potential link between ferroptosis and pulmonary hypertension severity in the Vanderbilt BioVU repository.

CONCLUSIONS

Ferroptosis promotes PAH through metabolic and inflammatory mechanisms in the pulmonary vasculature.

Dihydromyricetin treats pulmonary hypertension by modulating CKLF1/CCR5 axis-induced pulmonary vascular cell pyroptosis

Pulmonary hypertension (PH) is a progressive cardiopulmonary disease characterized by elevated pulmonary artery pressure and vascular remodeling, resulting in poor prognosis and increased mortality rates. Chemokine-like factor 1 (CKLF1) plays a significant role in inducing inflammation and cell proliferation, both of which are critical processes in the pathogenesis of various diseases. Dihydromyricetin (DMY) has garnered attention for its potent anti-inflammatory properties. This study evaluated the protective effects of DMY against PH, demonstrating that DMY treatment can mitigate pyroptosis in pulmonary artery endothelial cells (PAECs) and pulmonary artery smooth muscle cells (PASMCs) in vivo via the CKLF1/CCR5 axis. Results indicated significant improvements in hemodynamics, inflammatory responses, fibrosis, vascular remodeling, and right ventricular hypertrophy in PH rats following DMY treatment. Furthermore, the interaction between CKLF1 and CCR5 was investigated in CKLF1-/- rats after PH induction. DMY was found to downregulate CKLF1 expression and the inflammatory response in the lungs, with its therapeutic efficacy diminished following CKLF1 knockdown. This study underscores the therapeutic potential of DMY in the management of PH and lays a foundation for future research and clinical applications.

Integrative Multiomics in the Lung Reveals a Protective Role of Asporin in Pulmonary Arterial Hypertension

BACKGROUND

Integrative multiomics can elucidate pulmonary arterial hypertension (PAH) pathobiology, but procuring human PAH lung samples is rare.

METHODS

We leveraged transcriptomic profiling and deep phenotyping of the largest multicenter PAH lung biobank to date (96 disease and 52 control) by integration with clinicopathologic data, genome-wide association studies, Bayesian regulatory networks, single-cell transcriptomics, and pharmacotranscriptomics.

RESULTS

We identified 2 potentially protective gene network modules associated with vascular cells, and we validated ASPN, coding for asporin, as a key hub gene that is upregulated as a compensatory response to counteract PAH. We found that asporin is upregulated in lungs and plasma of multiple independent PAH cohorts and correlates with reduced PAH severity. We show that asporin inhibits proliferation and transforming growth factor-β/phosphorylated SMAD2/3 signaling in pulmonary artery smooth muscle cells from PAH lungs. We demonstrate in Sugen-hypoxia rats that ASPN knockdown exacerbated PAH and recombinant asporin attenuated PAH.

CONCLUSIONS

Our integrative systems biology approach to dissect the PAH lung transcriptome uncovered asporin as a novel protective target with therapeutic potential in PAH.

MSC-derived exosomes attenuates pulmonary hypertension via inhibiting pulmonary vascular remodeling

BACKGROUND

Pulmonary hypertension (PH) is a serious cardiopulmonary disease with significant morbidity and mortality. Vascular obstruction leads to a continuous increase in pulmonary vascular resistance, vascular remodeling, and right ventricular hypertrophy and failure, which are the main pathological features of PH. Currently, the treatments for PH are very limited, so new methods are urgently needed. Msenchymal stem cells-derived exosomes have been shown to have significant therapeutic effects in PH, however, the mechanism still very blurry. Here, we investigated the possible mechanism by which umbilical cord mesenchymal stem cell-derived exosomes (hUC-MSC-EXO) inhibited monocrotaline (MCT)-induced pulmonary vascular remodeling in a rat model of PH by regulating the NF-κB/BMP signaling pathway. Our data revealed that hUC-MSC-EXO could significantly attenuate MCT-induced PH and right ventricular hypertrophy. Moreover, the protein expression level of BMPR2, BMP-4, BMP-9 and ID1 was significantly increased, but NF-κB p65, p-NF-κB-p65 and BMP antagonists Gremlin-1 was increased in vitro and vivo. Collectively, this study revealed that the mechanism of hUC-MSC-EXO attenuates pulmonary hypertension may be related to inhibition of NF-κB signaling to further activation of BMP signaling. The present study provided a promising therapeutic strategy for PH vascular remodeling.

Single-cell transcriptomic analysis of radiation-induced lung injury in rat

Radiation-induced lung injury (RILI) frequently occurs as a complication following radiotherapy for chest tumors like lung and breast cancers. However, the precise underlying mechanisms of RILI remain unclear. In this study, we generated RILI models in rats treated with a single dose of 20 Gy and examined lung tissues by single-cell RNA sequencing (scRNA-seq) 2 weeks post-radiation. Analysis of lung tissues revealed 18 major cell populations, indicating an increase in cell-cell communication following radiation exposure. Neutrophils, macrophages, and monocytes displayed distinct subpopulations and uncovered potential for pro-inflammatory effects. Additionally, endothelial cells exhibited a highly inflammatory profile and the potential for reactive oxygen species (ROS) production. Furthermore, smooth muscle cells (SMC) showed a high propensity for extracellular matrix (ECM) deposition. Our findings broaden the current understanding of RILI and highlight potential avenues for further investigation and clinical applications.

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.

Immunotherapy for Pulmonary Arterial Hypertension: From the Pathogenesis to Clinical Management

Pulmonary hypertension (PH) is a progressive cardiovascular disease, which may lead to severe cardiopulmonary dysfunction. As one of the main PH disease groups, pulmonary artery hypertension (PAH) is characterized by pulmonary vascular remodeling and right ventricular dysfunction. Increased pulmonary artery resistance consequently causes right heart failure, which is the major reason for morbidity and mortality in this disease. Although various treatment strategies have been available, the poor clinical prognosis of patients with PAH reminds us that further studies of the pathological mechanism of PAH are still needed. Inflammation has been elucidated as relevant to the initiation and progression of PAH, and plays a crucial and functional role in vascular remodeling. Many immune cells and cytokines have been demonstrated to be involved in the pulmonary vascular lesions in PAH patients, with the activation of downstream signaling pathways related to inflammation. Consistently, this influence has been found to correlate with the progression and clinical outcome of PAH, indicating that immunity and inflammation may have significant potential in PAH therapy. Therefore, we reviewed the pathogenesis of inflammation and immunity in PAH development, focusing on the potential targets and clinical application of anti-inflammatory and immunosuppressive therapy.

Fetal hypoplastic lungs have multilineage inflammation that is reversed by amniotic fluid stem cell extracellular vesicle treatment

Antenatal administration of extracellular vesicles from amniotic fluid stem cells (AFSC-EVs) reverses features of pulmonary hypoplasia in models of congenital diaphragmatic hernia (CDH). However, it remains unknown which lung cellular compartments and biological pathways are affected by AFSC-EV therapy. Herein, we conducted single-nucleus RNA sequencing (snRNA-seq) on rat fetal CDH lungs treated with vehicle or AFSC-EVs. We identified that intra-amniotically injected AFSC-EVs reach the fetal lung in rats with CDH, where they promote lung branching morphogenesis and epithelial cell differentiation. Moreover, snRNA-seq revealed that rat fetal CDH lungs have a multilineage inflammatory signature with macrophage enrichment, which is reversed by AFSC-EV treatment. Macrophage enrichment in CDH fetal rat lungs was confirmed by immunofluorescence, flow cytometry, and inhibition studies with GW2580. Moreover, we validated macrophage enrichment in human fetal CDH lung autopsy samples. Together, this study advances knowledge on the pathogenesis of pulmonary hypoplasia and further evidence on the value of an EV-based therapy for CDH fetuses.

CRISPR-Cas9 Genome Editing Allows Generation of the Mouse Lung in a Rat

Rationale: Recent efforts in bioengineering and embryonic stem cell (ESC) technology allowed the generation of ESC-derived mouse lung tissues in transgenic mice that were missing critical morphogenetic genes. Epithelial cell lineages were efficiently generated from ESC, but other cell types were mosaic. A complete contribution of donor ESCs to lung tissue has never been achieved. The mouse lung has never been generated in a rat. Objective: We sought to generate the mouse lung in a rat. Methods: Clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 genome editing was used to disrupt the Nkx2-1 gene in rat one-cell zygotes. Interspecies mouse-rat chimeras were produced by injection of wild-type mouse ESCs into Nkx2-1-deficient rat embryos with lung agenesis. The contribution of mouse ESCs to the lung tissue was examined by immunostaining, flow cytometry, and single-cell RNA sequencing. Measurements and Main Results: Peripheral pulmonary and thyroid tissues were absent in rat embryos after CRISPR-Cas9-mediated disruption of the Nkx2-1 gene. Complementation of rat Nkx2-1-/- blastocysts with mouse ESCs restored pulmonary and thyroid structures in mouse-rat chimeras, leading to a near-99% contribution of ESCs to all respiratory cell lineages. Epithelial, endothelial, hematopoietic, and stromal cells in ESC-derived lungs were highly differentiated and exhibited lineage-specific gene signatures similar to those of respiratory cells from the normal mouse lung. Analysis of receptor-ligand interactions revealed normal signaling networks between mouse ESC-derived respiratory cells differentiated in a rat. Conclusions: A combination of CRISPR-Cas9 genome editing and blastocyst complementation was used to produce mouse lungs in rats, making an important step toward future generations of human lungs using large animals as "bioreactors."

Ultrasound Neuromodulation of an Anti-Inflammatory Pathway at the Spleen Improves Experimental Pulmonary Hypertension

BACKGROUND

Inflammation is pathogenically implicated in pulmonary arterial hypertension; however, it has not been adequately targeted therapeutically. We investigated whether neuromodulation of an anti-inflammatory neuroimmune pathway involving the splenic nerve using noninvasive, focused ultrasound stimulation of the spleen (sFUS) can improve experimental pulmonary hypertension.

METHODS

Pulmonary hypertension was induced in rats either by Sugen 5416 (20 mg/kg SQ) injection, followed by 21 (or 35) days of hypoxia (sugen/hypoxia model), or by monocrotaline (60 mg/kg IP) injection (monocrotaline model). Animals were randomized to receive either 12-minute-long sessions of sFUS daily or sham stimulation for 14 days. Catheterizations, echocardiography, indices of autonomic function, lung and heart histology and immunohistochemistry, spleen flow cytometry, and lung single-cell RNA sequencing were performed after treatment to assess the effects of sFUS.

RESULTS

Splenic denervation right before induction of pulmonary hypertension results in a more severe disease phenotype. In both sugen/hypoxia and monocrotaline models, sFUS treatment reduces right ventricular systolic pressure by 25% to 30% compared with sham treatment, without affecting systemic pressure, and improves right ventricular function and autonomic indices. sFUS reduces wall thickness, apoptosis, and proliferation in small pulmonary arterioles, suppresses CD3+ and CD68+ cell infiltration in lungs and right ventricular fibrosis and hypertrophy and lowers BNP (brain natriuretic peptide). Beneficial effects persist for weeks after sFUS discontinuation and are more robust with early and longer treatment. Splenic denervation abolishes sFUS therapeutic benefits. sFUS partially normalizes CD68+ and CD8+ T-cell counts in the spleen and downregulates several inflammatory genes and pathways in nonclassical and classical monocytes and macrophages in the lung. Differentially expressed genes in those cell types are significantly enriched for human pulmonary arterial hypertension-associated genes.

CONCLUSIONS

sFUS causes dose-dependent, sustained improvement of hemodynamic, autonomic, laboratory, and pathological manifestations in 2 models of experimental pulmonary hypertension. Mechanistically, sFUS normalizes immune cell populations in the spleen and downregulates inflammatory genes and pathways in the lung, many of which are relevant in human disease.

Fibroblasts in Pulmonary Hypertension: Roles and Molecular Mechanisms

Fibroblasts, among the most prevalent and widely distributed cell types in the human body, play a crucial role in defining tissue structure. They do this by depositing and remodeling extracellular matrixes and organizing functional tissue networks, which are essential for tissue homeostasis and various human diseases. Pulmonary hypertension (PH) is a devastating syndrome with high mortality, characterized by remodeling of the pulmonary vasculature and significant cellular and structural changes within the intima, media, and adventitia layers. Most research on PH has focused on alterations in the intima (endothelial cells) and media (smooth muscle cells). However, research over the past decade has provided strong evidence of the critical role played by pulmonary artery adventitial fibroblasts in PH. These fibroblasts exhibit the earliest, most dramatic, and most sustained proliferative, apoptosis-resistant, and inflammatory responses to vascular stress. This review examines the aberrant phenotypes of PH fibroblasts and their role in the pathogenesis of PH, discusses potential molecular signaling pathways underlying these activated phenotypes, and highlights areas of research that merit further study to identify promising targets for the prevention and treatment of PH.

Charting the cellular landscape of pulmonary arterial hypertension through single-cell omics

This review examines how single-cell omics technologies, particularly single-cell RNA sequencing (scRNAseq), enhance our understanding of pulmonary arterial hypertension (PAH). PAH is a multifaceted disorder marked by pulmonary vascular remodeling, leading to high morbidity and mortality. The cellular pathobiology of this heterogeneous disease, involving various vascular and non-vascular cell types, is not fully understood. Traditional PAH studies have struggled to resolve the complexity of pathogenic cell populations. scRNAseq offers a refined perspective by detailing cellular diversity within PAH, identifying unique cell subsets, gene networks, and molecular pathways that drive the disease. We discuss significant findings from recent literature, summarizing how scRNAseq has shifted our understanding of PAH in human, rat, and mouse models. This review highlights the insights gained into cellular phenotypes, gene expression patterns, and novel molecular targets, and contemplates the challenges and prospective paths for research. We propose ways in which single-cell omics could inform future research and translational efforts to combat PAH.

CircST6GAL1 knockdown alleviates pulmonary arterial hypertension by regulating miR-509-5p/multiple C2 and transmembrane domain containing 2 axis

BACKGROUND

Hypertension is a main contributing factor of cardiovascular diseases; deregulated circular RNAs are involved in the pathogenesis of pulmonary arterial hypertension (PAH). Herein, we evaluated the function and mechanism of circST6GAL1 in PAH process.

METHODS

Human pulmonary artery smooth muscle cells (HPASMCs) were cultured in hypoxic environment for functional analysis. The cell counting kit-8, 5-ethynyl-2'-deoxyuridine, wound healing, and flow cytometry assays were used to investigate cell proliferation, migration, and apoptosis. qRT-PCR and Western blotting analyses were used for level measurement of genes and proteins. The binding between miR-509-5p and circST6GAL1 or multiple C2 and transmembrane domain containing 2 (MCTP2) was analyzed by dual-luciferase reporter, RNA immunoprecipitation, and pull-down assays. The monocrotaline (MCT)-induced PAH mouse models were established for in vivo assay.

RESULTS

CircST6GAL1 was highly expressed in PAH patients and hypoxia-induced HPASMCs. Functionally, circST6GAL1 deficiency reversed hypoxia-induced proliferation and migration, as well as apoptosis arrest in HPASMCs. Mechanistically, circST6GAL1 directly targeted miR-509-5p, and MCTP2 was a target of miR-509-5p. Rescue assays showed that the regulatory effects of circST6GAL1 deficiency on hypoxia-induced HPASMCs were abolished. Moreover, forced expression of miR-509-5p suppressed HPASMC proliferation and migration and induced cell apoptosis under hypoxia stimulation, while these effects were abolished by MCTP2 overexpression. Moreover, circST6GAL1 silencing improved MCT-induced pulmonary vascular remodeling and PAH.

CONCLUSION

CircST6GAL1 deficiency reversed hypoxia-induced proliferation and migration, as well as apoptosis arrest in HPASMCs, and alleviated pulmonary vascular remodeling in MCT-induced PAH mouse models through the miR-509-5p/MCTP2 axis, indicating a potential therapeutic target for PAH.

Systemic Sclerosis-Associated Pulmonary Arterial Hypertension: From Bedside to Bench and Back Again

Systemic sclerosis (SSc) is a heterogeneous disease characterized by autoimmunity, vasculopathy, and fibrosis which affects the skin and internal organs. One key aspect of SSc vasculopathy is pulmonary arterial hypertension (SSc-PAH) which represents a leading cause of morbidity and mortality in patients with SSc. The pathogenesis of pulmonary hypertension is complex, with multiple vascular cell types, inflammation, and intracellular signaling pathways contributing to vascular pathology and remodeling. In this review, we focus on shared molecular features of pulmonary hypertension and those which make SSc-PAH a unique entity. We highlight advances in the understanding of the clinical and translational science pertinent to this disease. We first review clinical presentations and phenotypes, pathology, and novel biomarkers, and then highlight relevant animal models, key cellular and molecular pathways in pathogenesis, and explore emerging treatment strategies in SSc-PAH.

Identification of a distinct cluster of GDF15high macrophages induced by in vitro differentiation exhibiting anti-inflammatory activities

Introduction

Macrophage-mediated inflammatory response may have crucial roles in the pathogenesis of a variety of human diseases. Growth differentiation factor 15 (GDF15) is a cytokine of the transforming growth factor-β superfamily, with potential anti-inflammatory activities. Previous studies observed in human lungs some macrophages which expressed a high level of GDF15.

Methods

In the present study, we employed multiple techniques, including immunofluorescence, flow cytometry, and single-cell RNA sequencing, in order to further clarify the identity of such GDF15high macrophages.

Results

We demonstrated that macrophages derived from human peripheral blood mononuclear cells and rat bone marrow mononuclear cells by in vitro differentiation with granulocyte-macrophage colony stimulating factor contained a minor population (~1%) of GDF15high cells. GDF15high macrophages did not exhibit a typical M1 or M2 phenotype, but had a unique molecular signature as revealed by single-cell RNA sequencing. Functionally, the in vitro derived GDF15high macrophages were associated with reduced responsiveness to pro-inflammatory activation; furthermore, these GDF15high macrophages could inhibit the pro-inflammatory functions of other macrophages via a paracrine mechanism. We further confirmed that GDF15 per se was a key mediator of the anti-inflammatory effects of GDF15high macrophage. Also, we provided evidence showing that GDF15high macrophages were present in other macrophage-residing human tissues in addition to the lungs. Further scRNA-seq analysis in rat lung macrophages confirmed the presence of a GDF15high sub-population. However, these data indicated that GDF15high macrophages in the body were not a uniform population based on their molecular signatures. More importantly, as compared to the in vitro derived GDF15high macrophage, whether the tissue resident GDF15high counterpart is also associated with anti-inflammatory functions remains to be determined. We cannot exclude the possibility that the in vitro priming/induction protocol used in our study has a determinant role in inducing the anti-inflammatory phenotype in the resulting GDF15high macrophage cells.

Conclusion

In summary, our results suggest that the GDF15high macrophage cells obtained by in vitro induction may represent a distinct cluster with intrinsic anti-inflammatory functions. The (patho)physiological importance of these cells in vivo warrants further investigation.

Forsythoside B Mitigates Monocrotaline-Induced Pulmonary Arterial Hypertension via Blocking the NF-κB Signaling Pathway to Attenuate Vascular Remodeling

Purpose

Pulmonary arterial hypertension (PAH) is a devastating disease with little effective treatment. The proliferation of pulmonary artery smooth muscle cells (PASMCs) induced by the nuclear factor-κB (NF-κB) signaling activation plays a pivotal role in the pathogenesis of PAH. Forsythoside B (FTS•B) possesses inhibitory effect on NF-κB signaling pathway. The present study aims to explore the effects and mechanisms of FTS•B in PAH.

Methods

Sprague-Dawley rats received monocrotaline (MCT) intraperitoneal injection to establish PAH model, and FTS•B was co-treated after MCT injection. Right ventricular hypertrophy and pulmonary artery pressure were measured by echocardiography and right heart catheterization, respectively. Histological alterations were detected by H&E staining and immunohistochemistry. FTS•B's role in PASMC proliferation and migration were evaluated by CCK-8 and wound healing assay. To investigate the underlying mechanisms, Western blotting, immunofluorescence staining and ELISA were conducted. The NF-κB activator PMA was used to investigate the role of NF-κB in FTS•B's protective effects against PAH.

Results

FTS•B markedly alleviated MCT-induced vascular remodeling and pulmonary artery pressure, and improved right ventricular hypertrophy and survival. FTS•B also reversed PDGF-BB-induced PASMC proliferation and migration, decreased PCNA and CyclinD1 expression in vitro. The elevated levels of IL-1β and IL-6 caused by MCT were decreased by FTS•B. Mechanistically, MCT-triggered phosphorylation of p65, IκBα, IKKα and IKKβ was blunted by FTS•B. FTS•B also reversed MCT-induced nuclear translocation of p65. However, all these protective effects were blocked by PMA-mediated NF-κB activation.

Conclusion

FTS•B effectively attenuates PAH by suppressing the NF-κB signaling pathway to attenuate vascular remodeling. FTS•B might be a promising drug candidate with clinical translational potential for the treatment of PAH.

Pulmonary hypertension

Pulmonary hypertension encompasses a range of conditions directly or indirectly leading to elevated pressures within the pulmonary arteries. Five main groups of pulmonary hypertension are recognized, all defined by a mean pulmonary artery pressure of >20 mmHg: pulmonary arterial hypertension (rare), pulmonary hypertension associated with left-sided heart disease (very common), pulmonary hypertension associated with lung disease (common), pulmonary hypertension associated with pulmonary artery obstructions, usually related to thromboembolic disease (rare), and pulmonary hypertension with unclear and/or multifactorial mechanisms (rare). At least 1% of the world's population is affected, with a greater burden more likely in low-income and middle-income countries. Across all its forms, pulmonary hypertension is associated with adverse vascular remodelling with obstruction, stiffening and vasoconstriction of the pulmonary vasculature. Without proactive management this leads to hypertrophy and ultimately failure of the right ventricle, the main cause of death. In older individuals, dyspnoea is the most common symptom. Stepwise investigation precedes definitive diagnosis with right heart catheterization. Medical and surgical treatments are approved for pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. There are emerging treatments for other forms of pulmonary hypertension; but current therapy primarily targets the underlying cause. There are still major gaps in basic, clinical and translational knowledge; thus, further research, with a focus on vulnerable populations, is needed to better characterize, detect and effectively treat all forms of pulmonary hypertension.

Identification of hub genes based on integrated analysis of single-cell and microarray transcriptome in patients with pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a devastating chronic cardiopulmonary disease without an effective therapeutic approach. The underlying molecular mechanism of PAH remains largely unexplored at single-cell resolution.

METHODS

Single-cell RNA sequencing (scRNA-seq) data from the Gene Expression Omnibus (GEO) database (GSE210248) was included and analyzed comprehensively. Additionally, microarray transcriptome data including 15 lung tissue from PAH patients and 11 normal samples (GSE113439) was also obtained. Seurat R package was applied to process scRNA-seq data. Uniform manifold approximation and projection (UMAP) was utilized for dimensionality reduction and cluster identification, and the SingleR package was performed for cell annotation. FindAllMarkers analysis and ClusterProfiler package were applied to identify differentially expressed genes (DEGs) for each cluster in GSE210248 and GSE113439, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) were used for functional enrichment analysis of DEGs. Microenvironment Cell Populations counter (MCP counter) was applied to evaluate the immune cell infiltration. STRING was used to construct a protein-protein interaction (PPI) network of DEGs, followed by hub genes selection through Cytoscape software and Veen Diagram.

RESULTS

Nineteen thousand five hundred seventy-six cells from 3 donors and 21,896 cells from 3 PAH patients remained for subsequent analysis after filtration. A total of 42 cell clusters were identified through UMAP and annotated by the SingleR package. 10 cell clusters with the top 10 cell amounts were selected for consequent analysis. Compared with the control group, the proportion of adipocytes and fibroblasts was significantly reduced, while CD8+ T cells and macrophages were notably increased in the PAH group. MCP counter revealed decreased distribution of CD8+ T cells, cytotoxic lymphocytes, and NK cells, as well as increased infiltration of monocytic lineage in PAH lung samples. Among 997 DEGs in GSE113439, module 1 with 68 critical genes was screened out through the MCODE plug-in in Cytoscape software. The top 20 DEGs in each cluster of GSE210248 were filtered out by the Cytohubba plug-in using the MCC method. Eventually, WDR43 and GNL2 were found significantly increased in PAH and identified as the hub genes after overlapping these DEGs from GSE210248 and GSE113439.

CONCLUSION

WDR43 and GNL2 might provide novel insight into revealing the new molecular mechanisms and potential therapeutic targets for PAH.

Identification of monocyte-associated pathways participated in the pathogenesis of pulmonary arterial hypertension based on omics-data

Pulmonary arterial hypertension (PAH) is one kind of chronic and uncurable diseases that can cause heart failure. Immune microenvironment plays a significant role in PAH. The aim of this study was to assess the role of immune cell infiltration in the pathogenesis of PAH. Differentially expressed genes based on microarray data were enriched in several immune-related pathways. To evaluate the immune cell infiltration, based on the microarray data sets in the GEO database, we used both ssGSEA and the CIBERSORT algorithm. Additionally, single-cell RNA sequencing (scRNA-seq) data was used to further explicit the specific role and intercellular communications. Then receiver operating characteristic curves and least absolute shrinkage and selection operator were used to discover and test the potential diagnostic biomarkers for PAH. Both the immune cell infiltration analyses based on the microarray data sets and the cell proportion in scRNA-seq data exhibited a significant downregulation in the infiltration of monocytes in PAH. Then, the intercellular communications showed that the interaction weighs of most immune cells, including monocytes changed between the control and PAH groups, and the ITGAL-ITGB2 and ICAM signaling pathways played critical roles in this process. In addition, ITGAM and ICAM2 displayed good diagnosis values in PAH. This study implicated that the change of monocyte was one of the key immunologic features of PAH. Monocyte-associated ICAM-1 and ITGAL-ITGB2 signaling pathways might be involved in the pathogenesis of PAH.

Pulmonary Hypertension: A Contemporary Review

Major advances in pulmonary arterial hypertension, pulmonary hypertension (PH) associated with lung disease, and chronic thromboembolic PH cast new light on the pathogenetic mechanisms, epidemiology, diagnostic approach, and therapeutic armamentarium for pulmonary vascular disease. Here, we summarize key basic, translational, and clinical PH reports, emphasizing findings that build on current state-of-the-art research. This review includes cutting-edge progress in translational pulmonary vascular biology, with a guide to the diagnosis of patients in clinical practice, incorporating recent PH definition revisions that continue emphasis on early detection of disease. PH management is reviewed including an overview of the evolving considerations for the approach to treatment of PH in patients with cardiopulmonary comorbidities, as well as a discussion of the groundbreaking sotatercept data for the treatment of pulmonary arterial hypertension.

Bioinformatics analysis of the immune cell infiltration characteristics and correlation with crucial diagnostic markers in pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a pathophysiological syndrome, characterized by pulmonary vascular remodeling. Immunity and inflammation are progressively recognized properties of PAH, which are crucial for the initiation and maintenance of pulmonary vascular remodeling. This study explored immune cell infiltration characteristics and potential biomarkers of PAH using comprehensive bioinformatics analysis.

METHODS

Microarray data of GSE117261, GSE113439 and GSE53408 datasets were downloaded from Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified in GSE117261 dataset. The proportions of infiltrated immune cells were evaluated by CIBERSORT algorithm. Feature genes of PAH were selected by least absolute shrinkage and selection operator (LASSO) regression analysis and validated by fivefold cross-validation, random forest and logistic regression. The GSE113439 and GSE53408 datasets were used as validation sets and logistic regression and receiver operating characteristic (ROC) curve analysis were performed to evaluate the prediction value of PAH. The PAH-associated module was identified by weighted gene association network analysis (WGCNA). The intersection of genes in the modules screened and DEGs was used to construct protein-protein interaction (PPI) network and the core genes were selected. After the intersection of feature genes and core genes, the hub genes were identified. The correlation between hub genes and immune cell infiltration was analyzed by Pearson correlation analysis. The expression level of LTBP1 in the lungs of monocrotaline-induced PAH rats was determined by Western blotting. The localization of LTBP1 and CD4 in lungs of PAH was assayed by immunofluorescence.

RESULTS

A total of 419 DEGs were identified, including 223 upregulated genes and 196 downregulated genes. Functional enrichment analysis revealed that a significant enrichment in inflammation, immune response, and transforming growth factor β (TGFβ) signaling pathway. CIBERSORT analysis showed that ten significantly different types of immune cells were identified between PAH and control. Resting memory CD4+ T cells, CD8+ T cells, γδ T cells, M1 macrophages, and resting mast cells in the lungs of PAH patients were significantly higher than control. Seventeen feature genes were identified by LASSO regression for PAH prediction. WGCNA identified 15 co-expression modules. PPI network was constructed and 100 core genes were obtained. Complement C3b/C4b receptor 1 (CR1), thioredoxin reductase 1 (TXNRD1), latent TGFβ binding protein 1 (LTBP1), and toll-like receptor 1 (TLR1) were identified as hub genes and LTBP1 has the highest diagnostic efficacy for PAH (AUC = 0.968). Pearson correlation analysis showed that LTBP1 was positively correlated with resting memory CD4+ T cells, but negatively correlated with monocytes and neutrophils. Western blotting showed that the protein level of LTBP1 was increased in the lungs of monocrotaline-induced PAH rats. Immunofluorescence of lung tissues from rats with PAH showed increased expression of LTBP1 in pulmonary arteries as compared to control and LTBP1 was partly colocalized with CD4+ cells in the lungs.

CONCLUSION

LTBP1 was correlated with immune cell infiltration and identified as the critical diagnostic maker for PAH.

Spatial and temporal resolution of metabolic dysregulation in the Sugen hypoxia model of pulmonary hypertension

Although PAH is partially attributed to disordered metabolism, previous human studies have mostly examined circulating metabolites at a single time point, potentially overlooking crucial disease biology. Current knowledge gaps include an understanding of temporal changes that occur within and across relevant tissues, and whether observed metabolic changes might contribute to disease pathobiology. We utilized targeted tissue metabolomics in the Sugen hypoxia (SuHx) rodent model to investigate tissue-specific metabolic relationships with pulmonary hypertensive features over time using regression modeling and time-series analysis. Our hypotheses were that some metabolic changes would precede phenotypic changes, and that examining metabolic interactions across heart, lung, and liver tissues would yield insight into interconnected metabolic mechanisms. To support the relevance of our findings, we sought to establish links between SuHx tissue metabolomics and human PAH -omics data using bioinformatic predictions. Metabolic differences between and within tissue types were evident by Day 7 postinduction, demonstrating distinct tissue-specific metabolism in experimental pulmonary hypertension. Various metabolites demonstrated significant tissue-specific associations with hemodynamics and RV remodeling. Individual metabolite profiles were dynamic, and some metabolic shifts temporally preceded the emergence of overt pulmonary hypertension and RV remodeling. Metabolic interactions were observed such that abundance of several liver metabolites modulated lung and RV metabolite-phenotype relationships. Taken all together, regression analyses, pathway analyses and time-series analyses implicated aspartate and glutamate signaling and transport, glycine homeostasis, lung nucleotide abundance, and oxidative stress as relevant to early PAH pathobiology. These findings offer valuable insights into potential targets for early intervention in PAH.

Single-cell RNA landscape of cell heterogeneity and immune microenvironment in ligation-induced vascular remodeling in rat

BACKGROUND AND AIMS

Vascular remodeling is a common pathological basis for cardiovascular diseases. Although both immune and non-immune cells have been suggested to contribute to this process, the complex cellular heterogeneity and intercellular interactions remain largely uncharacterized.

METHODS AND RESULTS

In this study, we simulated early and late vascular remodeling by ligating the rat carotid artery for 1 week and 4 weeks, respectively. Using single-cell RNA-sequencing, we characterized gene expression signatures and driver signals of major cell types involved in vascular remodeling. Focused analysis revealed a novel sub-population of Selenbp1hi smooth muscle cells (SMCs) associated with vascular remodeling. Results of intercellular communication analyses predicted several ligand-receptor pairs between immune cells with SMCs and endothelial cells (ECs), implicating SMCs apoptosis and repair, ECs aging and inflammatory responses.

CONCLUSIONS

We present a comprehensive single-cell atlas of vascular cells in early and late stages of ligated rat carotid artery, providing valuable insights into the understanding of the initiation and progression of vascular remodeling.

Thoracic Spinal Cord Neuroinflammation as a Novel Therapeutic Target in Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is associated with aberrant sympathoexcitation leading to right ventricular failure (RVF), arrhythmias, and death. Microglial activation and neuroinflammation have been implicated in sympathoexcitation in experimental PH. We recently reported the first evidence of thoracic spinal cord (TSC) neuroinflammation in PH rats. Here, we hypothesize that PH is associated with increased cardiopulmonary afferent signaling leading to TSC-specific neuroinflammation and sympathoexcitation. Furthermore, inhibition of TSC neuroinflammation rescues experimental PH and RVF.

METHODS

We performed transcriptomic analysis and its validation on the TSC of monocrotaline (n=8) and Sugen hypoxia (n=8) rat models of severe PH-RVF. A group of monocrotaline rats received either daily intrathecal microglial activation inhibitor minocycline (200 μg/kg per day, n=5) or PBS (n=5) from day 14 through 28. Echocardiography and right ventricle-catheterization were performed terminally. Real-time quantitative reverse transcription PCR, immunolocalization, microglia+astrocyte quantification, and terminal deoxynucleotidyl transferase dUTP nick end labeling were assessed. Plasma catecholamines were measured by ELISA. Human spinal cord autopsy samples (Control n=3; pulmonary arterial hypertension n=3) were assessed to validate preclinical findings.

RESULTS

Increased cardiopulmonary afferent signaling was demonstrated in preclinical and clinical PH. Our findings delineated common dysregulated genes and pathways highlighting neuroinflammation and apoptosis in the remodeled TSC and highlighted increased sympathoexcitation in both rat models. Moreover, we validated significantly increased microglial and astrocytic activation and CX3CL1 expression in TSC of human pulmonary arterial hypertension. Finally, amelioration of TSC neuroinflammation by minocycline in monocrotaline rats inhibited microglial activation, decreased proinflammatory cytokines, sympathetic nervous system activation and significantly attenuated PH and RVF.

CONCLUSIONS

Targeting neuroinflammation and associated molecular pathways and genes in the TSC may yield novel therapeutic strategies for PH and RVF.

Tm4sf1-marked Endothelial Subpopulation Is Dysregulated in Pulmonary Arterial Hypertension

The identification and role of endothelial progenitor cells in pulmonary arterial hypertension (PAH) remain controversial. Single-cell omics analysis can shed light on endothelial progenitor cells and their potential contribution to PAH pathobiology. We aim to identify endothelial cells that may have stem/progenitor potential in rat lungs and assess their relevance to PAH. Differential expression, gene set enrichment, cell-cell communication, and trajectory reconstruction analyses were performed on lung endothelial cells from single-cell RNA sequencing of Sugen-hypoxia, monocrotaline, and control rats. Relevance to human PAH was assessed in multiple independent blood and lung transcriptomic data sets. Rat lung endothelial cells were visualized by immunofluorescence in situ, analyzed by flow cytometry, and assessed for tubulogenesis in vitro. A subpopulation of endothelial cells (endothelial arterial type 2 [EA2]) marked by Tm4sf1 (transmembrane 4 L six family member 1), a gene strongly implicated in cancer, harbored a distinct transcriptomic signature enriched for angiogenesis and CXCL12 signaling. Trajectory analysis predicted that EA2 has a less differentiated state compared with other endothelial subpopulations. Analysis of independent data sets revealed that TM4SF1 is downregulated in lungs and endothelial cells from patients and PAH models, is a marker for hematopoietic stem cells, and is upregulated in PAH circulation. TM4SF1+CD31+ rat lung endothelial cells were visualized in distal pulmonary arteries, expressed hematopoietic marker CD45, and formed tubules in coculture with lung fibroblasts. Our study uncovered a novel Tm4sf1-marked subpopulation of rat lung endothelial cells that may have stem/progenitor potential and demonstrated its relevance to PAH. Future studies are warranted to further elucidate the role of EA2 and Tm4sf1 in PAH.

Deciphering endothelial heterogeneity in health and disease at single-cell resolution: progress and perspectives

Endothelial cells (ECs) constitute the inner lining of vascular beds in mammals and are crucial for homeostatic regulation of blood vessel physiology, but also play a key role in pathogenesis of many diseases, thereby representing realistic therapeutic targets. However, it has become evident that ECs are heterogeneous, encompassing several subtypes with distinct functions, which makes EC targeting and modulation in diseases challenging. The rise of the new single-cell era has led to an emergence of studies aimed at interrogating transcriptome diversity along the vascular tree, and has revolutionized our understanding of EC heterogeneity from both a physiological and pathophysiological context. Here, we discuss recent landmark studies aimed at teasing apart the heterogeneous nature of ECs. We cover driving (epi)genetic, transcriptomic, and metabolic forces underlying EC heterogeneity in health and disease, as well as current strategies used to combat disease-enriched EC phenotypes, and propose strategies to transcend largely descriptive heterogeneity towards prioritization and functional validation of therapeutically targetable drivers of EC diversity. Lastly, we provide an overview of the most recent advances and hurdles in single EC OMICs.

Pulmonary Arterial Hypertension Patients Have a Proinflammatory Gut Microbiome and Altered Circulating Microbial Metabolites

Rationale: Inflammation drives pulmonary arterial hypertension (PAH). Gut dysbiosis causes immune dysregulation and systemic inflammation by altering circulating microbial metabolites; however, little is known about gut dysbiosis and microbial metabolites in PAH. Objectives: To characterize the gut microbiome and microbial metabolites in patients with PAH. Methods: We performed 16S ribosomal RNA gene and shotgun metagenomics sequencing on stool from patients with PAH, family control subjects, and healthy control subjects. We measured markers of inflammation, gut permeability, and microbial metabolites in plasma from patients with PAH, family control subjects, and healthy control subjects. Measurements and Main Results: The gut microbiome was less diverse in patients with PAH. Shannon diversity index correlated with measures of pulmonary vascular disease but not with right ventricular function. Patients with PAH had a distinct gut microbial signature at the phylogenetic level, with fewer copies of gut microbial genes that produce antiinflammatory short-chain fatty acids (SCFAs) and secondary bile acids and lower relative abundances of species encoding these genes. Consistent with the gut microbial changes, patients with PAH had relatively lower plasma concentrations of SCFAs and secondary bile acids. Patients with PAH also had enrichment of species with the microbial genes that encoded the proinflammatory microbial metabolite trimethylamine. The changes in the gut microbiome and circulating microbial metabolites between patients with PAH and family control subjects were not as substantial as the differences between patients with PAH and healthy control subjects. Conclusions: Patients with PAH have proinflammatory gut dysbiosis, in which lower circulating SCFAs and secondary bile acids may facilitate pulmonary vascular disease. These findings support investigating modulation of the gut microbiome as a potential treatment for PAH.

Integrative Multiomics to Dissect the Lung Transcriptional Landscape of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) remains an incurable and often fatal disease despite currently available therapies. Multiomics systems biology analysis can shed new light on PAH pathobiology and inform translational research efforts. Using RNA sequencing on the largest PAH lung biobank to date (96 disease and 52 control), we aim to identify gene co-expression network modules associated with PAH and potential therapeutic targets. Co-expression network analysis was performed to identify modules of co-expressed genes which were then assessed for and prioritized by importance in PAH, regulatory role, and therapeutic potential via integration with clinicopathologic data, human genome-wide association studies (GWAS) of PAH, lung Bayesian regulatory networks, single-cell RNA-sequencing data, and pharmacotranscriptomic profiles. We identified a co-expression module of 266 genes, called the pink module, which may be a response to the underlying disease process to counteract disease progression in PAH. This module was associated not only with PAH severity such as increased PVR and intimal thickness, but also with compensated PAH such as lower number of hospitalizations, WHO functional class and NT-proBNP. GWAS integration demonstrated the pink module is enriched for PAH-associated genetic variation in multiple cohorts. Regulatory network analysis revealed that BMPR2 regulates the main target of FDA-approved riociguat, GUCY1A2, in the pink module. Analysis of pathway enrichment and pink hub genes (i.e. ANTXR1 and SFRP4) suggests the pink module inhibits Wnt signaling and epithelial-mesenchymal transition. Cell type deconvolution showed the pink module correlates with higher vascular cell fractions (i.e. myofibroblasts). A pharmacotranscriptomic screen discovered ubiquitin-specific peptidases (USPs) as potential therapeutic targets to mimic the pink module signature. Our multiomics integrative study uncovered a novel gene subnetwork associated with clinicopathologic severity, genetic risk, specific vascular cell types, and new therapeutic targets in PAH. Future studies are warranted to investigate the role and therapeutic potential of the pink module and targeting USPs in PAH.

Loss of lung microvascular endothelial Piezo2 expression impairs NO synthesis, induces EndMT, and is associated with pulmonary hypertension

Mechanical forces are translated into biochemical stimuli by mechanotransduction channels, such as the mechanically activated cation channel Piezo2. Lung Piezo2 expression has recently been shown to be restricted to endothelial cells. Hence, we aimed to investigate the role of Piezo2 in regulation of pulmonary vascular function and structure, as well as its contribution to development of pulmonary arterial hypertension (PAH). The expression of Piezo2 was significantly reduced in pulmonary microvascular endothelial cells (MVECs) from patients with PAH, in lung tissue from mice with a Bmpr2^+/R899X knock-in mutation commonly found in patients with pulmonary hypertension, and in lung tissue of monocrotaline (MCT) and sugen-hypoxia-induced PH (SuHx) PAH rat models, as well as from a swine model with pulmonary vein banding. In MVECs, Piezo2 expression was reduced in response to abnormal shear stress, hypoxia, and TGFβ stimulation. Functional studies in MVECs exposed to shear stress illustrated that siRNA-mediated Piezo2 knockdown impaired endothelial alignment, calcium influx, phosphorylation of AKT, and nitric oxide production. In addition, siPiezo2 reduced the expression of the endothelial marker PECAM-1 and increased the expression of vascular smooth muscle markers ACTA2, SM22a, and calponin. Thus, Piezo2 acts as a mechanotransduction channel in pulmonary MVECs, stimulating shear-induced production of nitric oxide and is essentially involved in preventing endothelial to mesenchymal transition. Its blunted expression in pulmonary hypertension could impair the vasodilator capacity and stimulate vascular remodeling, indicating that Piezo2 might be an interesting therapeutic target to attenuate progression of the disease.NEW & NOTEWORTHY The mechanosensory ion channel Piezo2 is exclusively expressed in lung microvascular endothelial cells (MVECs). Patient MVECs as well as animal models of pulmonary (arterial) hypertension showed lower expression of Piezo2 in the lung. Mechanistically, Piezo2 is required for calcium influx and NO production in response to shear stress, whereas stimuli known to induce endothelial to mesenchymal transition (EndMT) reduce Piezo2 expression in MVECs, and Piezo2 knockdown induces a gene and protein expression pattern consistent with EndMT.

Inflammation and Oxidative Stress Induce NGF Secretion by Pulmonary Arterial Cells through a TGF-β1-Dependent Mechanism

Expression of the nerve growth factor NGF is increased in pulmonary hypertension (PH). We have here studied whether oxidative stress and inflammation, two pathological conditions associated with transforming growth factor-β1 (TGF-β1) in PH, may trigger NGF secretion by pulmonary arterial (PA) cells. Effects of hydrogen peroxide (H2O2) and interleukin-1β (IL-1β) were investigated ex vivo on rat pulmonary arteries, as well as in vitro on human PA smooth muscle (hPASMC) or endothelial cells (hPAEC). TβRI expression was assessed by Western blotting. NGF PA secretion was assessed by ELISA after TGF-β1 blockade (anti-TGF-β1 siRNA, TGF-β1 blocking antibodies, TβRI kinase, p38 or Smad3 inhibitors). TβRI PA expression was evidenced by Western blotting both ex vivo and in vitro. H2O2 or IL-1β significantly increased NGF secretion by hPASMC and hPAEC, and this effect was significantly reduced when blocking TGF-β1 expression, binding to TβRI, TβRI activity, or signaling pathways. In conclusion, oxidative stress and inflammation may trigger TGF-β1 secretion by hPASMC and hPAEC. TGF-β1 may then act as an autocrine factor on these cells, increasing NGF secretion via TβRI activation. Since NGF and TGF-β1 are relevant growth factors involved in PA remodeling, such mechanisms may therefore be relevant to PH pathophysiology.

Single-cell RNA sequencing profiling of mouse endothelial cells in response to pulmonary arterial hypertension

AIMS

Endothelial cell (EC) dysfunction drives the initiation and pathogenesis of pulmonary arterial hypertension (PAH). We aimed to characterize EC dynamics in PAH at single-cell resolution.

METHODS AND RESULTS

We carried out single-cell RNA sequencing (scRNA-seq) of lung ECs isolated from an EC lineage-tracing mouse model in Control and SU5416/hypoxia-induced PAH conditions. EC populations corresponding to distinct lung vessel types, including two discrete capillary populations, were identified in both Control and PAH mice. Differential gene expression analysis revealed global PAH-induced EC changes that were confirmed by bulk RNA-seq. This included upregulation of the major histocompatibility complex class II pathway, supporting a role for ECs in the inflammatory response in PAH. We also identified a PAH response specific to the second capillary EC population including upregulation of genes involved in cell death, cell motility, and angiogenesis. Interestingly, four genes with genetic variants associated with PAH were dysregulated in mouse ECs in PAH. To compare relevance across PAH models and species, we performed a detailed analysis of EC heterogeneity and response to PAH in rats and humans through whole-lung PAH scRNA-seq datasets, revealing that 51% of up-regulated mouse genes were also up-regulated in rat or human PAH. We identified promising new candidates to target endothelial dysfunction including CD74, the knockdown of which regulates EC proliferation and barrier integrity in vitro. Finally, with an in silico cell ordering approach, we identified zonation-dependent changes across the arteriovenous axis in mouse PAH and showed upregulation of the Serine/threonine-protein kinase Sgk1 at the junction between the macro- and microvasculature.

CONCLUSION

This study uncovers PAH-induced EC transcriptomic changes at a high resolution, revealing novel targets for potential therapeutic candidate development.

Effect of invasive mechanical ventilation on the diversity of the pulmonary microbiota

Pulmonary microbial diversity may be influenced by biotic or abiotic conditions (e.g., disease, smoking, invasive mechanical ventilation (MV), etc.). Specially, invasive MV may trigger structural and physiological changes in both tissue and microbiota of lung, due to gastric and oral microaspiration, altered body posture, high O2 inhalation-induced O2 toxicity in hypoxemic patients, impaired airway clearance and ventilator-induced lung injury (VILI), which in turn reduce the diversity of the pulmonary microbiota and may ultimately lead to poor prognosis. Furthermore, changes in (local) O2 concentration can reduce the diversity of the pulmonary microbiota by affecting the local immune microenvironment of lung. In conclusion, systematic literature studies have found that invasive MV reduces pulmonary microbiota diversity, and future rational regulation of pulmonary microbiota diversity by existing or novel clinical tools (e.g., lung probiotics, drugs) may improve the prognosis of invasive MV treatment and lead to more effective treatment of lung diseases with precision.

Evolving Concepts in Endothelial Pathobiology of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a deadly disease, characterized by increased vascular resistance, pulmonary arteriolar loss, and occlusive arterial remodeling, leading to eventual right heart failure. Evidence increasingly points to the pulmonary endothelium as a central actor in PAH. Endothelial cell apoptosis can result directly in distal lung arteriolar pruning and indirectly in the formation of complex and occlusive arterial lesions, reflecting an imbalance between endothelial injury and repair in the development and progression of PAH. Many of the mutations implicated in PAH are in genes, which are predominantly, or solely, expressed in endothelial cells, and the endothelium is a major target for therapeutic interventions to restore BMP signaling. We explore how arterial pruning can promote the emergence of occlusive arterial remodeling mediated by ongoing endothelial injury secondary to hemodynamic perturbation and pathological increases in luminal shear stress. The emerging role of endothelial cell senescence is discussed in the transition from reversible to irreversible arterial remodeling in advanced PAH, and we review the sometimes conflicting evidence that female sex hormones can both protect or promote vascular changes in disease. Finally, we explore the contribution of the endothelium to metabolic changes and the altered inflammatory and immune state in the PAH lung, focusing on the role of excessive TGFβ signaling. Given the complexity of the endothelial pathobiology of PAH, we anticipate that emerging technologies that allow the study of molecular events at a single cell level will provide answers to many of the questions raised in this review.

Single cell study of cellular diversity and mutual communication in chronic heart failure and drug repositioning

Non-cardiomyocytes (non-CMs) play an important role in the process of cardiac remodeling of chronic heart failure. The mechanism of non-CMs transit and interact with each other remains largely unknown. Here, we try to characterize the cellular landscape of non-CMs in mice with chronic heart failure by using single-cell RNA sequencing (scRNA-seq) and provide potential therapeutic hunts. Cellular and molecular analysis revealed that the most affected cellular types are mainly fibroblasts and endothelial cells. Specially, Fib_0 cluster, the most abundant cluster in fibroblasts, was the only increased one, enriched for collagen synthesis genes such as Adamts4 and Crem, which might be responsible for the fibrosis in cardiac remodeling. End_0 cluster in endothelial cells was also the most abundant and only increased one, which has an effect of blood vessel morphogenesis. Cell communication further confirmed that fibroblasts and endothelial cells are the driving hubs in chronic heart failure. Furthermore, using fibroblasts and endothelial cells as the entry point of CMap technology, histone deacetylation (HDAC) inhibitors and HSP inhibitors were identified as potential anti-heart failure new drugs, which should be evaluated in the future. The combined application of scRNA-seq and CMap might be an effective way to achieve drug repositioning.

Harnessing Big Data to Advance Treatment and Understanding of Pulmonary Hypertension

Pulmonary hypertension is a complex disease with multiple causes, corresponding to phenotypic heterogeneity and variable therapeutic responses. Advancing understanding of pulmonary hypertension pathogenesis is likely to hinge on integrated methods that leverage data from health records, imaging, novel molecular -omics profiling, and other modalities. In this review, we summarize key data sets generated thus far in the field and describe analytical methods that hold promise for deciphering the molecular mechanisms that underpin pulmonary vascular remodeling, including machine learning, network medicine, and functional genetics. We also detail how genetic and subphenotyping approaches enable earlier diagnosis, refined prognostication, and optimized treatment prediction. We propose strategies that identify functionally important molecular pathways, bolstered by findings across multi-omics platforms, which are well-positioned to individualize drug therapy selection and advance precision medicine in this highly morbid disease.

Experimental animal models of pulmonary hypertension: Development and challenges

Pulmonary hypertension (PH) is clinically divided into 5 major types, characterized by elevation in pulmonary arterial pressure (PAP) and pulmonary vascular resistance (PVR), finally leading to right heart failure and death. The pathogenesis of this arteriopathy remains unclear, leaving it impossible to target pulmonary vascular remodeling and reverse the deterioration of right ventricular (RV) function. Different animal models have been designed to reflect the complex mechanistic origins and pathology of PH, roughly divided into 4 categories according to the modeling methods: non‐invasive models in vivo, invasive models in vivo, gene editing models, and multi‐means joint modeling. Though each model shares some molecular and pathological changes with different classes of human PH, in most cases the molecular etiology of human PH is poorly known. The appropriate use of classic and novel PH animal models is essential for the hunt of molecular targets to reverse severe phenotypes.

Guidelines for bioinformatics of single-cell sequencing data analysis in Alzheimer's disease: review, recommendation, implementation and application

Alzheimer's disease (AD) is the most common form of dementia, characterized by progressive cognitive impairment and neurodegeneration. Extensive clinical and genomic studies have revealed biomarkers, risk factors, pathways, and targets of AD in the past decade. However, the exact molecular basis of AD development and progression remains elusive. The emerging single-cell sequencing technology can potentially provide cell-level insights into the disease. Here we systematically review the state-of-the-art bioinformatics approaches to analyze single-cell sequencing data and their applications to AD in 14 major directions, including 1) quality control and normalization, 2) dimension reduction and feature extraction, 3) cell clustering analysis, 4) cell type inference and annotation, 5) differential expression, 6) trajectory inference, 7) copy number variation analysis, 8) integration of single-cell multi-omics, 9) epigenomic analysis, 10) gene network inference, 11) prioritization of cell subpopulations, 12) integrative analysis of human and mouse sc-RNA-seq data, 13) spatial transcriptomics, and 14) comparison of single cell AD mouse model studies and single cell human AD studies. We also address challenges in using human postmortem and mouse tissues and outline future developments in single cell sequencing data analysis. Importantly, we have implemented our recommended workflow for each major analytic direction and applied them to a large single nucleus RNA-sequencing (snRNA-seq) dataset in AD. Key analytic results are reported while the scripts and the data are shared with the research community through  GitHub. In summary, this comprehensive review provides insights into various approaches to analyze single cell sequencing data and offers specific guidelines for study design and a variety of analytic directions. The review and the accompanied software tools will serve as a valuable resource for studying cellular and molecular mechanisms of AD, other diseases, or biological systems at the single cell level.

Identification of Hypoxia Induced Metabolism Associated Genes in Pulmonary Hypertension

Objective: Pulmonary hypertension (PH) associated with hypoxia and lung disease (Group 3) is the second most common form of PH and associated with increased morbidity and mortality. This study was aimed to identify hypoxia induced metabolism associated genes (MAGs) for better understanding of hypoxic PH.

Methods: Rat pulmonary arterial smooth muscle cells (PASMCs) were isolated and cultured in normoxic or hypoxic condition for 24 h. Cells were harvested for liquid chromatography-mass spectrometry analysis. Functional annotation of distinguishing metabolites was performed using Metaboanalyst. Top 10 enriched metabolite sets were selected for the identification of metabolism associated genes (MAGs) with a relevance score >8 in Genecards. Transcriptomic data from lungs of hypoxic PH in mice/rats or of PH patients were accessed from Gene Expression Omnibus (GEO) database or open-access online platform. Connectivity Map analysis was performed to identify potential compounds to reverse the metabolism associated gene profile under hypoxia stress. The construction and module analysis of the protein-protein interaction (PPI) network was performed. Hub genes were then identified and used to generate LASSO model to determine its accuracy to predict occurrence of PH.

Results: A total of 36 altered metabolites and 1,259 unique MAGs were identified in rat PASMCs under hypoxia. 38 differentially expressed MAGs in mouse lungs of hypoxic PH were revealed, with enrichment in multi-pathways including regulation of glucose metabolic process, which might be reversed by drugs such as blebbistatin. 5 differentially expressed MAGs were displayed in SMCs of Sugen 5416/hypoxia induced PH rats at the single cell resolution. Furthermore, 6 hub genes (Cat, Ephx1, Gpx3, Gstm4, Gstm5, and Gsto1) out of 42 unique hypoxia induced MAGs were identified. Higher Cat, Ephx1 and lower Gsto1 were displayed in mouse lungs under hypoxia (all p < 0.05), in consistent with the alteration in lungs of PH patients. The hub gene-based LASSO model can predict the occurrence of PH (AUC = 0.90).

Conclusion: Our findings revealed six hypoxia-induced metabolism associated hub genes, and shed some light on the molecular mechanism and therapeutic targets in hypoxic PH.

Molecular and Genetic Profiling for Precision Medicines in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a rare and chronic lung disease characterized by progressive occlusion of the small pulmonary arteries, which is associated with structural and functional alteration of the smooth muscle cells and endothelial cells within the pulmonary vasculature. Excessive vascular remodeling is, in part, responsible for high pulmonary vascular resistance and the mean pulmonary arterial pressure, increasing the transpulmonary gradient and the right ventricular "pressure overload", which may result in right ventricular (RV) dysfunction and failure. Current technological advances in multi-omics approaches, high-throughput sequencing, and computational methods have provided valuable tools in molecular profiling and led to the identification of numerous genetic variants in PAH patients. In this review, we summarized the pathogenesis, classification, and current treatments of the PAH disease. Additionally, we outlined the latest next-generation sequencing technologies and the consequences of common genetic variants underlying PAH susceptibility and disease progression. Finally, we discuss the importance of molecular genetic testing for precision medicine in PAH and the future of genomic medicines, including gene-editing technologies and gene therapies, as emerging alternative approaches to overcome genetic disorders in PAH.