Comprehensive analysis of inflammatory markers in chronic thromboembolic pulmonary hypertension patients

Hypoxia Combined With Interleukin-17 Regulates Hypoxia-Inducible Factor-1α/Endothelial Nitric Oxide Synthase Expression in Pulmonary Artery Endothelial Cells

The pathogenesis of chronic thromboembolic pulmonary hypertension may be multifactorial and requires further studies. We explored alterations in pulmonary artery endothelial cells under the hypoxic and elevated interleukin-17 conditions that are commonly present in patients with chronic thromboembolic pulmonary hypertension. We measured the serum interleukin-17 levels in 10 chronic thromboembolic pulmonary hypertension patients and 10 healthy control persons. The expressions and localisations of hypoxia-inducible factor-1α and endothelial nitric oxide synthase were detected in tissues. The levels of hypoxia-inducible factor-1α, endothelial nitric oxide synthase, nitric oxide, and reactive oxygen species in cultured pulmonary artery endothelial cells were examined under hypoxia and/or interleukin-17 treatment. The serum interleukin-17 level was increased in chronic thromboembolic pulmonary hypertension patients. Hypoxia-inducible factor-1α was increased, and endothelial nitric oxide synthase was decreased in chronic thromboembolic pulmonary hypertension pulmonary vascular tissue. After receiving the hypoxia combined with interleukin-17 treatment, pulmonary artery endothelial cells showed increased levels of hypoxia-inducible factor-1α and phospho-endothelial nitric oxide synthase (Thr495) (p = 0.001 and 0.063, respectively) and a decreased level of endothelial nitric oxide synthase (p < 0.001). In addition, the nitric oxide level was significantly decreased (p = 0.001), whereas the reactive oxygen species level was insignificantly increased in pulmonary artery endothelial cells. Chronic thromboembolic pulmonary hypertension patients might experience increased inflammation and hypoxia due to dysregulation of the hypoxia-inducible factor-1α/endothelial nitric synthase pathway in pulmonary artery endothelial cells under inflammation and hypoxia, contributing to the pathogenesis of chronic thromboembolic pulmonary hypertension.

A Mendelian randomization study on the association between systemic inflammatory regulators and essential and secondary hypertension

Background

Inflammation is an important driver of hypertension with numerous components, and there is a paucity of research on the specific inflammatory factors that induce hypertension; therefore, we wanted to investigate the relationship between specific inflammatory factors and hypertension.

Purpose

A two-sample Mendelian randomization (MR) study was conducted to assess the causal relationship between systemic inflammatory regulators and hypertension (primary or secondary types).

Method

a large-scale, published genome-wide association study (GWAS) meta-analysis encompassing 41 cytokines (involved 8,293 Finnish participants from three independent population cohorts: the Cardiovascular Risk in Young Finns Study (YFS), FINRISK1997, and FINRISK2002.)were utilized, a variety of analyses including MR-Egger, weighted median, simple mode and weighted mode were used as sensitive analyses, to corroborate the causal relationship between inflammatory regulators and hypertension. Additionally, we used MR-Egger intercept test and Mendelian Randomization Pleiotropy RE Sidual Sum and Outlier (MR-PRESSO global test) to further evaluate the presence of horizontal pleiotropy.

Results

3 inflammatory regulators were found related to secondary hypertension, TNFb was negatively associated with risk of secondary hypertension, with a OR of one SD increase in genetically predicted TNFb causing 16.6% (95% CI: 4.4%-27.1%) lower risk of secondary hypertension. Similar trend was also found in MIP1b (OR = 0.91; 95% CI 0.84-0.99, p = 0.024) and MIG (OR = 0.88; 95% CI 0.78-0.99, p = 0.040). Additionally, there was not any evidence of 41 inflammatory regulators associated with primary hypertension.

Conclusion

This study supports a negative correlation between TNFb, MIP1b, MIG and secondary hypertension.

Identification and validation of CCL5 as a key gene in HIV infection and pulmonary arterial hypertension

Background

The relationship between human immunodeficiency virus (HIV) infection and pulmonary arterial hypertension (PAH) has garnered significant scrutiny. Individuals with HIV infection have a higher risk of developing PAH. However, the specific mechanism of HIV-associated PAH remains unclear. Our study aims at investigating the shared biomarkers in HIV infection and PAH and predicting the potential therapeutic target for HIV-associated PAH.

Methods

Data for HIV infection and PAH were downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) analysis was performed to detect shared genes in HIV infection and PAH. Enrichment analysis was conducted to identify the function of common DEGs. Protein-protein interaction (PPI) analysis was used to detect key genes. These crucial genes were subsequently verified by RT-qPCR. Finally, candidate drugs were identified by using the Drug Signatures Database (DSigDB).

Results

Nineteen common DEGs were identified in HIV infection and PAH. Enrichment analysis exhibited that the functions of these genes were mainly enriched in inflammatory responses, mainly including cellular immunity and interaction between viral proteins and cytokines. By constructing PPI networks, we identified the key gene CC-type chemokine ligand 5 (CCL5), and we verified that CCL5 was highly expressed in hypoxia induced human pulmonary artery endothelial cells (hPAECs) and human pulmonary artery smooth muscle cells (hPASMCs). In addition, we predicted 10 potential drugs targeting CCL5 by Autodock Vina.

Conclusion

This study revealed that CCL5 might be a common biomarker of HIV infection and PAH and provided a new therapeutic target for HIV-associated PAH. However, further clinical validation is still indispensable.

Understanding pulmonary hypertension: the need for an integrative metabolomics and transcriptomics approach

Pulmonary hypertension (PH), characterised by mean pulmonary arterial pressure (mPAP) >20 mm Hg at rest, is a complex pathophysiological disorder associated with multiple clinical conditions. The high prevalence of the disease along with increased mortality and morbidity makes it a global health burden. Despite major advances in understanding the disease pathophysiology, much of the underlying complex molecular mechanism remains to be elucidated. Lack of a robust diagnostic test and specific therapeutic targets also poses major challenges. This review provides a comprehensive update on the dysregulated pathways and promising candidate markers identified in PH patients using the transcriptomics and metabolomics approach. The review also highlights the need of using an integrative multi-omics approach for obtaining insight into the disease at a molecular level. The integrative multi-omics/pan-omics approach envisaged to help in bridging the gap from genotype to phenotype is outlined. Finally, the challenges commonly encountered while conducting omics-driven studies are also discussed.

Shared and Distinct Genomics of Chronic Thromboembolic Pulmonary Hypertension and Pulmonary Embolism

Rationale: Chronic thromboembolic pulmonary hypertension involves the formation and nonresolution of thrombus, dysregulated inflammation, angiogenesis, and the development of a small-vessel vasculopathy. Objectives: We aimed to establish the genetic basis of chronic thromboembolic pulmonary hypertension to gain insight into its pathophysiological contributors. Methods: We conducted a genome-wide association study on 1,907 European cases and 10,363 European control subjects. We coanalyzed our results with existing results from genome-wide association studies on deep vein thrombosis, pulmonary embolism, and idiopathic pulmonary arterial hypertension. Measurements and Main Results: Our primary association study revealed genetic associations at the ABO, FGG, F11, MYH7B, and HLA-DRA loci. Through our coanalysis, we demonstrate further associations with chronic thromboembolic pulmonary hypertension at the F2, TSPAN15, SLC44A2, and F5 loci but find no statistically significant associations shared with idiopathic pulmonary arterial hypertension. Conclusions: Chronic thromboembolic pulmonary hypertension is a partially heritable polygenic disease, with related though distinct genetic associations with pulmonary embolism and deep vein thrombosis.

Predominance of M2 macrophages in organized thrombi in chronic thromboembolic pulmonary hypertension patients

Chronic thromboembolic pulmonary hypertension (CTEPH) is a debilitating disease characterized by thrombotic occlusion of pulmonary arteries and vasculopathy, leading to increased pulmonary vascular resistance and progressive right-sided heart failure. Thrombotic lesions in CTEPH contain CD68+ macrophages, and increasing evidence supports their role in disease pathogenesis. Macrophages are classically divided into pro-inflammatory M1 macrophages and anti-inflammatory M2 macrophages, which are involved in wound healing and tissue repair. Currently, the phenotype of macrophages and their localization within thrombotic lesions of CTEPH are largely unknown. In our study, we subclassified thrombotic lesions of CTEPH patients into developing fresh thrombi (FT) and organized thrombi (OT), based on the degree of fibrosis and remodeling. We used multiplex immunofluorescence histology to identify immune cell infiltrates in thrombotic lesions of CPTEH patients. Utilizing software-assisted cell detection and quantification, increased proportions of macrophages were observed in immune cell infiltrates of OT lesions, compared with FT. Strikingly, the proportions with a CD206+INOS- M2 phenotype were significantly higher in OT than in FT, which mainly contained unpolarized macrophages. Taken together, we observed a shift from unpolarized macrophages in FT toward an expanded population of M2 macrophages in OT, indicating a dynamic role of macrophages during CTEPH pathogenesis.

Angiogenesis in Chronic Thromboembolic Pulmonary Hypertension: A Janus-Faced Player?

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare form of pulmonary hypertension characterized by the presence of organized thrombi that obstruct pulmonary arteries, ultimately leading to right heart failure and death. Among others, impaired angiogenesis and inflammatory thrombosis have been shown to contribute to the progression of CTEPH. In this review, we summarize the 2-faced nature of angiogenesis in both thrombus formation and resolution in the context of CTEPH and highlight the dual role of angiogenesis and neovascularization in resolving venous thrombi. Furthermore, we discuss relevant in vitro and in vivo models that support the benefits or drawbacks of angiogenesis in CTEPH progression. We discuss the key pathways involved in modulating angiogenesis, particularly the underexplored role of TGFβ (transforming growth factor-beta) signaling in driving fibrosis as an integral element of CTEPH pathogenesis. We finally explore innovative treatment strategies that target angiogenic pathways. These strategies have the potential to pioneer preventive, inventive, or alternative therapeutic options for patients with CTEPH who may not qualify for surgical interventions. Moreover, they could be used synergistically with established treatments such as pulmonary endarterectomy or balloon pulmonary angioplasty. In summary, this review emphasizes the crucial role of angiogenesis in the development of in fibrothrombotic tissue, a major pathological characteristic of CTEPH.

Pulmonary thromboendarterectomy in hospitalized versus elective patients with chronic thromboembolic pulmonary hypertension

OBJECTIVE

We sought to characterize outcomes in patients undergoing pulmonary thromboendarterectomy electively versus after acute presentation.

METHODS

This is a retrospective analysis of patients who underwent pulmonary thromboendarterectomy from October 2015 to April 2022. Patients were divided into 2 groups depending on elective surgery or surgery during the same hospitalization as their presentation.

RESULTS

In total, 69 patients were included: 45 in the hospitalized group and 24 in the elective group. Patients in the hospitalized group were less likely to have chronic lung disease, history of pulmonary embolism and hypertension, be on anticoagulation and medication for pulmonary hypertension, and present with >1 month of respiratory symptoms. They were more likely to have worse preoperative right ventricular function. Among other demographics, risk factors for venous thromboembolism were similar between both groups. Thirteen patients in the hospitalized group required preoperative extracorporeal membrane oxygenation. There was no difference in disease classification and operative, cardiopulmonary bypass, and hypothermic circulatory arrest durations between both groups. Postoperative complications were similar between both groups, except for greater frequency of deep vein thrombosis in the hospitalized group (26.7% vs 4.2%, P = .03). In-hospital and intensive care unit length of stay were similar between both groups. Overall, in-hospital mortality was 4.3% and was similar between both groups; P = .28.

CONCLUSIONS

Our series shows that pulmonary thromboendarterectomy can be safely performed in patients presenting acutely, with comparable postoperative complications and in-hospital mortality to an elective setting. Such patients present with worse right ventricular function, sometimes requiring temporary mechanical support.

Clonal Hematopoiesis of Indeterminate Potential in Chronic Thromboembolic Pulmonary Hypertension: A Multicenter Study

BACKGROUND

The pathogenesis of chronic thromboembolic pulmonary hypertension (CTEPH) is multifactorial and growing evidence has indicated that hematological disorders are involved. Clonal hematopoiesis of indeterminate potential (CHIP) has recently been associated with an increased risk of both hematological malignancies and cardiovascular diseases. However, the prevalence and clinical relevance of CHIP in patients with CTEPH remains unclear.

METHODS

Using stepwise calling on next-generation sequencing data from 499 patients with CTEPH referred to 3 centers between October 2006 and December 2021, CHIP mutations were identified. We associated CHIP with all-cause mortality in patients with CTEPH. To provide insights into potential mechanisms, the associations between CHIP and inflammatory markers were also determined.

RESULTS

In total, 47 (9.4%) patients with CTEPH carried at least 1 CHIP mutation at a variant allele frequency of ≥2%. The most common mutations were in DNMT3A, TET2, RUNX1, and ASXL1. During follow-up (mean, 55 months), deaths occurred in 22 (46.8%) and 104 (23.0%) patients in the CHIP and non-CHIP groups, respectively (P<0.001, log-rank test). The association of CHIP with mortality remained robust in the fully adjusted model (hazard ratio, 2.190 [95% CI, 1.257-3.816]; P=0.006). Moreover, patients with CHIP mutations showed higher circulating interleukin-1β and interleukin-6 and lower interleukin-4 and IgG galactosylation levels.

CONCLUSIONS

This is the first study to show that CHIP mutations occurred in 9.4% of patients with CTEPH are associated with a severe inflammatory state and confer a poorer prognosis in long-term follow-up.

Pulmonary Hypertension and the Gut Microbiome

The gut microbiome and its associated metabolites are integral to the maintenance of gut integrity and function. There is increasing evidence that its alteration, referred to as dysbiosis, is involved in the development of a systemic conditions such as cardiovascular disease (e.g., systemic hypertension, atherosclerosis). Pulmonary hypertension (PH) is a condition characterised by progressive remodelling and vasoconstriction of the pulmonary circulation, ultimately leading to right ventricular failure and premature mortality if untreated. Initial studies have suggested a possible association between dysbiosis of the microbiome and the development of PH. The aim of this article is to review the current experimental and clinical data with respect to the potential interaction between the gut microbiome and the pathophysiology of pulmonary hypertension. It will also highlight possible new therapeutic targets that may provide future therapies.

Chronic Thromboembolic Pulmonary Hypertension: A Review of the Multifaceted Pathobiology

Chronic thromboembolic pulmonary disease results from the incomplete resolution of thrombi, leading to fibrotic obstructions. These vascular obstructions and additional microvasculopathy may lead to chronic thromboembolic pulmonary hypertension (CTEPH) with increased pulmonary arterial pressure and pulmonary vascular resistance, which, if left untreated, can lead to right heart failure and death. The pathobiology of CTEPH has been challenging to unravel due to its rarity, possible interference of results with anticoagulation, difficulty in selecting the most relevant study time point in relation to presentation with acute pulmonary embolism (PE), and lack of animal models. In this article, we review the most relevant multifaceted cross-talking pathogenic mechanisms and advances in understanding the pathobiology in CTEPH, as well as its challenges and future direction. There appears to be a genetic background affecting the relevant pathological pathways. This includes genetic associations with dysfibrinogenemia resulting in fibrinolysis resistance, defective angiogenesis affecting thrombus resolution, and inflammatory mediators driving chronic inflammation in CTEPH. However, these are not necessarily specific to CTEPH and some of the pathways are also described in acute PE or deep vein thrombosis. In addition, there is a complex interplay between angiogenic and inflammatory mediators driving thrombus non-resolution, endothelial dysfunction, and vascular remodeling. Furthermore, there are data to suggest that infection, the microbiome, circulating microparticles, and the plasma metabolome are contributing to the pathobiology of CTEPH.

Single-Cell Analysis Reveals Distinct Immune and Smooth Muscle Cell Populations that Contribute to Chronic Thromboembolic Pulmonary Hypertension

Rationale: Chronic thromboembolic pulmonary hypertension (CTEPH) is a sequela of acute pulmonary embolism (PE) in which the PE remodels into a chronic scar in the pulmonary arteries. This results in vascular obstruction, pulmonary microvasculopathy, and pulmonary hypertension. Objectives: Our current understanding of CTEPH pathobiology is primarily derived from cell-based studies limited by the use of specific cell markers or phenotypic modulation in cell culture. Therefore, our main objective was to identify the multiple cell types that constitute CTEPH thrombusy and to study their dysfunction. Methods: Here we used single-cell RNA sequencing of tissue removed at the time of pulmonary endarterectomy surgery from five patients to identify the multiple cell types. Using in vitro assays, we analyzed differences in phenotype between CTEPH thrombus and healthy pulmonary vascular cells. We studied potential therapeutic targets in cells isolated from CTEPH thrombus. Measurements and Main Results: Single-cell RNA sequencing identified multiple cell types, including macrophages, T cells, and smooth muscle cells (SMCs), that constitute CTEPH thrombus. Notably, multiple macrophage subclusters were identified but broadly split into two categories, with the larger group characterized by an upregulation of inflammatory signaling predicted to promote pulmonary vascular remodeling. CD4+ and CD8+ T cells were identified and likely contribute to chronic inflammation in CTEPH. SMCs were a heterogeneous population, with a cluster of myofibroblasts that express markers of fibrosis and are predicted to arise from other SMC clusters based on pseudotime analysis. Additionally, cultured endothelial, smooth muscle, and myofibroblast cells isolated from CTEPH fibrothrombotic material have distinct phenotypes from control cells with regard to angiogenic potential and rates of proliferation and apoptosis. Last, our analysis identified PAR1 (protease-activated receptor 1) as a potential therapeutic target that links thrombosis to chronic PE in CTEPH, with PAR1 inhibition decreasing SMC and myofibroblast proliferation and migration. Conclusions: These findings suggest a model for CTEPH similar to atherosclerosis, with chronic inflammation promoted by macrophages and T cells driving vascular remodeling through SMC modulation, and suggest new approaches for pharmacologically targeting this disease.

Angiopoietin 2 and hsCRP are associated with pulmonary hemodynamics and long-term mortality respectively in CTEPH-Results from a prospective discovery and validation biomarker study

INTRODUCTION

Chronic thromboembolic pulmonary hypertension (CTEPH) is an underdiagnosed disease of uncertain etiology. Altered endothelial homeostasis, defective angiogenesis and inflammation are implicated. Angiopoietin 2 (Ang2) impairs acute thrombus resolution and is associated with vasculopathy in idiopathic pulmonary arterial hypertension.

METHODS

We assessed circulating proteins associated with these processes in serum from patients with CTEPH (n = 71) before and after pulmonary endarterectomy (PEA), chronic thromboembolic pulmonary disease without pulmonary hypertension (CTEPD, n = 9) and healthy controls (n = 20) using Luminex multiplex arrays. Comparisons between groups were made using multivariable rank regression models. Ang2 and high-sensitivity C-reactive protein (hsCRP) were measured in a larger validation dataset (CTEPH = 277, CTEPD = 26). Cox proportional hazards models were used to identify markers predictive of survival.

RESULTS

In CTEPH patients, Ang2, interleukin (IL) 8, tumor necrosis factor α, and hsCRP were elevated compared to controls, while vascular endothelial growth factor (VEGF) c was lower (p < 0.05). Ang2 fell post-PEA (p < 0.05) and was associated with both pre- and post-PEA pulmonary hemodynamic variables and functional assessments (p < 0.05). In the validation dataset, Ang2 was significantly higher in CTEPH compared to CTEPD. Pre-operative hsCRP was an independent predictor of mortality.

CONCLUSIONS

We hypothesize that CTEPH patients have significant distal micro-vasculopathy and consequently high circulating Ang2. Patients with CTEPD without pulmonary hypertension have no discernible distal micro-vasculopathy and therefore have low circulating Ang2. This suggests Ang2 may be critical to CTEPH disease pathogenesis (impaired thrombus organization and disease severity).

Pathophysiology and Treatment of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a condition in which an organic thrombus remains in the pulmonary artery (PA) even after receiving anticoagulation therapy for more than 3 months and is complicated by pulmonary hypertension (PH), leading to right-sided heart failure and death. CTEPH is a progressive pulmonary vascular disease with a poor prognosis if left untreated. The standard treatment for CTEPH is pulmonary endarterectomy (PEA), which is usually performed only in specialized centers. In recent years, balloon pulmonary angioplasty (BPA) and drug therapy for CTEPH have also shown good results. This review discusses the complex pathogenesis of CTEPH and presents the standard of care, PEA, as well as a new device called BPA, which is showing remarkable progress in efficacy and safety. Additionally, several drugs are now demonstrating established evidence of efficacy in treating CTEPH.

The Evolving Management and Treatment Options for Patients with Pulmonary Hypertension: Current Evidence and Challenges

Pulmonary hypertension may develop as a disease process specific to pulmonary arteries with no identifiable cause or may occur in relation to other cardiopulmonary and systemic illnesses. The World Health Organization (WHO) classifies pulmonary hypertensive diseases on the basis of primary mechanisms causing increased pulmonary vascular resistance. Effective management of pulmonary hypertension begins with accurately diagnosing and classifying the disease in order to determine appropriate treatment. Pulmonary arterial hypertension (PAH) is a particularly challenging form of pulmonary hypertension as it involves a progressive, hyperproliferative arterial process that leads to right heart failure and death if untreated. Over the last two decades, our understanding of the pathobiology and genetics behind PAH has evolved and led to the development of several targeted disease modifiers that ameliorate hemodynamics and quality of life. Effective risk management strategies and more aggressive treatment protocols have also allowed better outcomes for patients with PAH. For those patients who experience progressive PAH with medical therapy, lung transplantation remains a life-saving option. More recent work has been directed at developing effective treatment strategies for other forms of pulmonary hypertension, such as chronic thromboembolic pulmonary hypertension (CTEPH) and pulmonary hypertension due to other lung or heart diseases. The discovery of new disease pathways and modifiers affecting the pulmonary circulation is an ongoing area of intense investigation.

Evidence for a Role of CCR6+ T Cells in Chronic Thromboembolic Pulmonary Hypertension

Introduction

Previous studies have shown an increase of T cells and chemokines in vascular lesions of patients with chronic thromboembolic pulmonary hypertension (CTEPH). However, detailed characterization of these T cells is still lacking, nor have treatment effects been evaluated.

Methods

We included 41 treatment-naive CTEPH patients at diagnosis, 22 patients at 1-year follow-up, and 17 healthy controls (HCs). Peripheral blood T cells were characterized by flow cytometry for subset distribution, cytokine expression and activation marker profile. We used multiplex immunofluorescence to identify CCR6⁺ T cells in endarterectomy tissue from 25 patients.

Results

At diagnosis, proportions of CCR6⁺ CD4⁺ T cells were increased in CTEPH patients compared with HCs. Patients displayed a significantly reduced production capacity of several cytokines including TNFα, IFNγ, GM-CSF and IL-4 in CD4⁺ T cells, and TNFα and IFNγ in CD8⁺ T cells. CD4⁺ and CD8⁺ T cells showed increased expression of the immune checkpoint protein CTLA4. Multivariate analysis separated CTEPH patients from HCs, based on CCR6 and CTLA4 expression. At 1-year follow-up, proportions of CCR6⁺CD4⁺ T cells were further increased, IFNγ and IL-17 production capacity of CD4⁺ T cells was restored. In nearly all vascular lesions we found substantial numbers of CCR6⁺ T cells.

Conclusion

The observed increase of CCR6⁺ T cells and modulation of the IFNγ and IL-17 production capacity of circulating CD4⁺ T cells at diagnosis and 1-year follow-up – together with the presence of CCR6⁺ T cells in vascular lesions - support the involvement of the Th17-associated CCR6⁺ T cell subset in CTEPH.

Platelet, Fibrinolytic and Other Coagulation Abnormalities in Newly-Diagnosed Patients with Chronic Thromboembolic Pulmonary Hypertension

The pathophysiological background of chronic thromboembolic pulmonary hypertension (CTEPH) has not been fully elucidated. Evidence suggests that abnormal platelet function and ineffective fibrinolysis may play a key role in the development of the disease. The purpose of this study was to evaluate platelet and coagulation function in CTEPH, using non-conventional global coagulation assays, and platelet activation and endothelial dysfunction laboratory markers. A total of 40 newly-diagnosed CTEPH patients were studied, along with 35 healthy controls. Blood samples from CTEPH patients were taken directly from the pulmonary artery. All subjects were assessed with platelet function analyzer-100, light transmission aggregometry, thromboelastometry, endogenous thrombin potential. von Willebrand antigen and activity, p-selectin, thromboxane A2 and serotonin levels were also assessed. The results showed that CTEPH patients present diminished platelet aggregation, presence of disaggregation, decreased rate of fibrinolysis, defective thrombin generation and increased levels of thromboxane A2, p-selectin, von Willebrand antigen and activity. Serotonin levels did not present any differences between the two groups. The results of this study suggest that CTEPH patients present platelet function, fibrinolytic, thrombin generation and other clot formation abnormalities. Well-designed clinical studies are needed to further evaluate the complex hemostatic abnormalities in the CTEPH setting and assess their potential clinical applications.

CXCL10 levels in diagnosis and improved hemodynamics in patients with chronic thromboembolic pulmonary hypertension undergoing balloon pulmonary angioplasty

Chronic thromboembolic pulmonary hypertension (CTEPH) is a progressive pulmonary vascular disease characterized by pulmonary artery stenosis or obstructions resulting from insufficient thrombus resolution. Chemokine (C‐X‐C motif) ligand 10 (CXCL10) is a chemokine that contributes to the pathogenesis of many autoimmune diseases and cancers. The present study aims to investigate the levels of CXCL10 in patients with CTEPH throughout balloon pulmonary angioplasty (BPA) and its correlation with the improvement of pulmonary hemodynamics. Plasma CXCL10 levels were measured in 38 CTEPH patients with 100 BPA sessions and in 28 healthy controls. Correlations between CXCL10 and pulmonary hemodynamics were investigated. Receiver operating characteristic (ROC) curves were plotted to display the diagnostic value and the predictive ability for perioperative complications of CXCL10 and CXCL10‐related models. Nomograms were plotted to visualize the diagnostic value and the predictive ability for perioperative complications of CXCL10 and CXCL10‐related models. CXCL10 levels are higher in CTEPH patients compared with healthy controls (36.5 [95% confidence interval {CI}: 25.0–51.1] vs. 14.8 [95% CI: 11.1–30.9], p < 0.0001) and decreased significantly after BPA treatment (36.5 [95% CI: 25.0–51.1] vs. 24.7 [95% CI: 17.2–36.6], p < 0.0005). Preoperative CXCL10 levels positively correlated with mean right atrial pressure (r = 0.25), systolic pulmonary artery pressure (PAP; r = 0.28), diastolic PAP (r = 0.33), mean PAP (r = 0.36), pulmonary vascular resistance (r = 0.31), and N‐terminal pro‐B‐type natriuretic peptide (NT‐proBNP; r = 0.46). Furthermore, plasma CXCL10 levels adjusting for age and sex displayed a sensitivity of 86.0% and a specificity of 67.9% for discriminating CTEPH patients from healthy controls. Preoperative CXCL10 levels, in combination with NT‐proBNP, predicted perioperative complications with a sensitivity of 100.0% and a specificity of 46.9% as displayed in ROC analysis. In conclusion, circulating CXCL10 might contribute to the evaluation of disease severity in CTEPH patients and be useful to evaluate the treatment effect of BPA. Future studies are warranted to further study the relationship between pulmonary hemodynamics and circulating CXCL10.

Altered gut microbiota and its association with inflammation in patients with chronic thromboembolic pulmonary hypertension: a single-center observational study in Japan

Background

The pathogenesis of chronic thromboembolic pulmonary hypertension (CTEPH) is considered to be associated with chronic inflammation; however, the underlying mechanism remains unclear. Recently, altered gut microbiota were found in patients with pulmonary arterial hypertension (PAH) and in experimental PAH models. The aim of this study was to characterize the gut microbiota in patients with CTEPH and assess the relationship between gut dysbiosis and inflammation in CTEPH.

Methods

In this observational study, fecal samples were collected from 11 patients with CTEPH and 22 healthy participants. The abundance of gut microbiota in these fecal samples was assessed using 16S ribosomal ribonucleic acid (rRNA) gene sequencing. Inflammatory cytokine and endotoxin levels were also assessed in patients with CTEPH and control participants.

Results

The levels of serum tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-8, and macrophage inflammatory protein (MIP)-1α were elevated in patients with CTEPH. Plasma endotoxin levels were significantly increased in patients with CTEPH (P < 0.001), and were positively correlated with TNF-α, IL-6, IL-8, and MIP-1α levels. The 16S rRNA gene sequencing and the principal coordinate analysis revealed the distinction in the gut microbiota between patients with CTEPH (P < 0.01) and control participants as well as the decreased bacterial alpha-diversity in patients with CTEPH. A random forest analysis for predicting the distinction in gut microbiota revealed an accuracy of 80.3%.

Conclusion

The composition of the gut microbiota in patients with CTEPH was distinct from that of healthy participants, which may be associated with the elevated inflammatory cytokines and endotoxins in CTEPH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01932-0.

Epigenetic Modification of the VWF Promotor Drives Platelet Aggregation on the Pulmonary Endothelium in Chronic Thromboembolic Pulmonary Hypertension

RATIONALE

Von Willebrand Factor (VWF) mediates platelet adhesion during thrombosis. While chronic thromboembolic pulmonary hypertension (CTEPH) is associated with increased plasma levels of VWF, the role of this protein in CTEPH has remained enigmatic.

OBJECTIVE

To identify the role of VWF in CTEPH.

METHODS

CTEPH-specific patient plasma and pulmonary endarterectomy material from CTEPH patients were used to study the relationship between inflammation, VWF expression and pulmonary thrombosis. Cell culture findings were validated in human tissue and proteomics and chromatin immunoprecipitation were used to investigate the underlying mechanism of CTEPH.

MEASUREMENTS AND MAIN RESULTS

VWF is increased in plasma and in the pulmonary endothelium of CTEPH patients. In vitro, the increase in VWF gene expression and the higher release of VWF protein upon endothelial activation resulted in elevated platelet adhesion to CTEPH endothelium. Proteomic analysis revealed that Nuclear Factor κB 2 (NFκB2) was significantly increased in CTEPH. We demonstrate reduced histone tri-methylation and increased histone acetylation of the VWF promotor in CTEPH endothelium, facilitating binding of NFκB2 to the VWF promotor and driving VWF transcription. Genetic interference of NFκB2 normalized the high VWF RNA expression levels and reversed the pro-thrombotic phenotype observed in CTEPH-PAEC.

CONCLUSION

Epigenetic regulation of the VWF promotor contributes to the creation of a local environment that favors in situ thrombosis in the pulmonary arteries. It reveals a direct molecular link between inflammatory pathways and platelet adhesion in the pulmonary vascular wall, emphasizing a possible role of in situ thrombosis in the development or progression of CTEPH.

Circulating Blood-Based Biomarkers in Pulmonary Hypertension

Pulmonary hypertension (PH) is a serious hemodynamic condition, characterized by increased pulmonary vascular resistance (PVR), leading to right heart failure (HF) and death when not properly treated. The prognosis of PH depends on etiology, hemodynamic and biochemical parameters, as well as on response to specific treatment. Biomarkers appear to be useful noninvasive tools, providing information about the disease severity, treatment response, and prognosis. However, given the complexity of PH, it is impossible for a single biomarker to be adequate for the broad assessment of patients with different types of PH. The search for novel emerging biomarkers is still ongoing, resulting in a few potential biomarkers mirroring numerous pathophysiological courses. In this review, markers related to HF, myocardial remodeling, inflammation, hypoxia and tissue damage, and endothelial and pulmonary smooth muscle cell dysfunction are discussed in terms of diagnosis and prognosis. Extracellular vesicles and other markers with complex backgrounds are also reviewed. In conclusion, although many promising biomarkers have been identified and studied in recent years, there are still insufficient data on the application of multimarker strategies for monitoring and risk stratification in PH patients.

The Pathobiology of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension is characterized by obliteration and obstruction of the pulmonary arterioles that in turn results in high right ventricular afterload and right heart failure. The pathobiology of pulmonary arterial hypertension is complex, with contributions from multiple pathophysiologic processes that are regulated by a variety of molecular mechanisms. This nature likely explains the limited efficacy of our current therapies, which only target a small portion of the pathobiological mechanisms that underlie advanced disease. Here we review the pathobiology of pulmonary arterial hypertension, focusing on the systemic, cellular, and molecular mechanisms that underlie the disease.

Derivation and characterisation of endothelial cells from patients with chronic thromboembolic pulmonary hypertension

Pulmonary endarterectomy (PEA) resected material offers a unique opportunity to develop an in vitro endothelial cell model of chronic thromboembolic pulmonary hypertension (CTEPH). We aimed to comprehensively analyze the endothelial function, molecular signature, and mitochondrial profile of CTEPH-derived endothelial cells to better understand the pathophysiological mechanisms of endothelial dysfunction behind CTEPH, and to identify potential novel targets for the prevention and treatment of the disease. Isolated cells from specimens obtained at PEA (CTEPH-EC), were characterized based on morphology, phenotype, and functional analyses (in vitro and in vivo tubule formation, proliferation, apoptosis, and migration). Mitochondrial content, morphology, and dynamics, as well as high-resolution respirometry and oxidative stress, were also studied. CTEPH-EC displayed a hyperproliferative phenotype with an increase expression of adhesion molecules and a decreased apoptosis, eNOS activity, migration capacity and reduced angiogenic capacity in vitro and in vivo compared to healthy endothelial cells. CTEPH-EC presented altered mitochondrial dynamics, increased mitochondrial respiration and an unbalanced production of reactive oxygen species and antioxidants. Our study is the foremost comprehensive investigation of CTEPH-EC. Modulation of redox, mitochondrial homeostasis and adhesion molecule overexpression arise as novel targets and biomarkers in CTEPH.

Evaluation and management of patients with chronic thromboembolic pulmonary hypertension - consensus statement from the ISHLT

ISHLT members have recognized the importance of a consensus statement on the evaluation and management of patients with chronic thromboembolic pulmonary hypertension. The creation of this document required multiple steps, including the engagement of the ISHLT councils, approval by the Standards and Guidelines Committee, identification and selection of experts in the field, and the development of 6 working groups. Each working group provided a separate section based on an extensive literature search. These sections were then coalesced into a single document that was circulated to all members of the working groups. Key points were summarized at the end of each section. Due to the limited number of comparative trials in this field, the document was written as a literature review with expert opinion rather than based on level of evidence.

Chronic Thromboembolic Pulmonary Hypertension: the Bench

PURPOSE OF REVIEW

Chronic thromboembolic pulmonary hypertension (CTEPH) is an uncommon complication of acute pulmonary embolism (PE), in which the red, platelet-rich thrombus does not resolve but forms into an organized yellow, fibrotic scar-like obstruction in the pulmonary vasculature. Here we review the pathobiology of CTEPH.

RECENT FINDINGS

Our current knowledge has predominantly been informed by studies of human samples and animal models that are inherently limited in their ability to recapitulate all aspects of the disease. These studies have identified alterations in platelet biology and inflammation in the formation of a scar-like thrombus that comprised endothelial cells, myofibroblasts, and immune cells, along with a small vessel pulmonary arterial hypertension-like vasculopathy. The development of CTEPH-specific therapies is currently hindered by a limited knowledge of its pathobiology. The development of new CTEPH medical therapies will require new insights into its pathobiology that bridge the gap from bench to bedside.

In situ Pulmonary Artery Thrombosis: A Previously Overlooked Disease

Pulmonary thromboembolism (PTE) is the third leading cause of death in cardiovascular diseases. PTE is believed to be caused by thrombi detached from deep veins of lower extremities. The thrombi travel with systemic circulation to the lung and block pulmonary arteries, leading to sudden disruption of hemodynamics and blood gas exchange. However, this concept has recently been challenged by accumulating evidence demonstrating that de novo thrombosis may be formed in pulmonary arteries without deep venous thrombosis. On the other hand, chronic thromboembolic pulmonary hypertension (CTEPH), a subtype of pulmonary hypertension, could have different pathogenesis than traditional PTE. Therefore, this article summarized and compared the risk factors, the common and specific pathogenic mechanisms underlying PTE, in situ pulmonary artery thrombosis, and CTEPH at molecular and cellular levels, and suggested the therapeutic strategies to these diseases, aiming to facilitate understanding of pathogenesis, differential diagnosis, and precision therapeutics of the three pulmonary artery thrombotic diseases.

Peripheral Arterial Stiffness in Acute Pulmonary Embolism and Pulmonary Hypertension at Short-Term Follow-Up

Chronic thromboembolic pulmonary hypertension (CTEPH) is a severe and under-recognized complication of acute pulmonary embolism (PE). Forty consecutive patients with acute PE (Group 1), predominantly female (22, 55%) with a mean age of 69 ± 15 years, were matched for demographic data with 40 healthy subjects (Group 2), 40 systemic hypertension patients (Group 3) and 45 prevalent idiopathic pulmonary arterial hypertension (IPAH) patients (Group 4). The baseline evaluation included physical examination, NYHA/WHO functional class, right heart catheterization (RHC) limited to IPAH patients, echocardiographic assessment and systemic arterial stiffness measurement by cardio-ankle vascular index (CAVI). Patients with PE underwent an echocardiographic evaluation within 1 month from hospital discharge (median 27 days; IQR 21–30) to assess the echo-derived probability of PH. The CAVI values were significantly higher in the PE and IPAH groups compared with the others (Group 1 vs. Group 2, p < 0.001; Group 1 vs. Group 3, p < 0.001; Group 1 vs. Group 4, p = ns; Group 4 vs. Group 2, p < 0.001; Group 4 vs. Group 3, p < 0.001; Group 2 vs. Group 3, p = ns). The predicted probability of echocardiography-derived high-risk criteria of PH increases for any unit increase of CAVI (OR 9.0; C.I.3.9–20.5; p = 0.0001). The PE patients with CAVI ≥ 9.0 at the time of hospital discharge presented an increased probability of PH. This study highlights a possible positive predictive role of CAVI as an early marker for the development of CTEPH.

NEDD9 Is a Novel and Modifiable Mediator of Platelet-Endothelial Adhesion in the Pulmonary Circulation

Rationale: Data on the molecular mechanisms that regulate platelet-pulmonary endothelial adhesion under conditions of hypoxia are lacking, but may have important therapeutic implications. Objectives: To identify a hypoxia-sensitive, modifiable mediator of platelet-pulmonary artery endothelial cell adhesion and thrombotic remodeling. Methods: Network medicine was used to profile protein-protein interactions in hypoxia-treated human pulmonary artery endothelial cells. Data from liquid chromatography-mass spectrometry and microscale thermophoresis informed the development of a novel antibody (Ab) to inhibit platelet-endothelial adhesion, which was tested in cells from patients with chronic thromboembolic pulmonary hypertension (CTEPH) and three animal models in vivo. Measurements and Main Results: The protein NEDD9 was identified in the hypoxia thrombosome network in silico. Compared with normoxia, hypoxia (0.2% O2) for 24 hours increased HIF-1α (hypoxia-inducible factor-1α)-dependent NEDD9 upregulation in vitro. Increased NEDD9 was localized to the plasma-membrane surface of cells from control donors and patients with CTEPH. In endarterectomy specimens, NEDD9 colocalized with the platelet surface adhesion molecule P-selectin. Our custom-made anti-NEDD9 Ab targeted the NEDD9-P-selectin interaction and inhibited the adhesion of activated platelets to pulmonary artery endothelial cells from control donors in vitro and from patients with CTEPH ex vivo. Compared with control mice, platelet-pulmonary endothelial aggregates and pulmonary hypertension induced by ADP were decreased in NEDD9-/- mice or wild-type mice treated with the anti-NEDD9 Ab, which also decreased chronic pulmonary thromboembolic remodeling in vivo. Conclusions: The NEDD9-P-selectin protein-protein interaction is a modifiable target with which to inhibit platelet-pulmonary endothelial adhesion and thromboembolic vascular remodeling, with potential therapeutic implications for patients with disorders of increased hypoxia signaling pathways, including CTEPH.

Plasma markers in pulmonary hypertension subgroups correlate with patient survival

Background

Recent studies have provided evidence for an important contribution of the immune system in the pathophysiology of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). In this report, we investigated whether the inflammatory profile of pulmonary hypertension patients changes over time and correlates with patient WHO subgroups or survival.

Methods

50 PAH patients (16 idiopathic (I)PAH, 24 Connective Tissue Disease (CTD)-PAH and 10 Congenital Heart Disease (CHD)-PAH), 37 CTEPH patients and 18 healthy controls (HCs) were included in the study. Plasma inflammatory markers at baseline and after 1-year follow-up were measured using ELISAs. Subsequently, correlations with hemodynamic parameters and survival were explored and data sets were subjected to unbiased multivariate analyses.

Results

At diagnosis, we found that plasma levels of interleukin-6 (IL-6) and the chemokines (C-X3-C) motif legend CXCL9 and CXCL13 in CTD-PAH patients were significantly increased, compared with HCs. In idiopathic PAH patients the levels of tumor growth factor-β (TGFβ), IL-10 and CXCL9 were elevated, compared with HCs. The increased CXCL9 and IL-8 concentrations in CETPH patients correlated significantly with decreased survival, suggesting that CXCL9 and IL-8 may be prognostic markers. After one year of treatment, IL-10, CXCL13 and TGFβ levels changed significantly in the PAH subgroups and CTEPH patients. Unbiased multivariate analysis revealed clustering of PH patients based on inflammatory mediators and clinical parameters, but did not separate the WHO subgroups. Importantly, these multivariate analyses separated patients with < 3 years and > 3 years survival, in particular when inflammatory mediators were combined with clinical parameters.

Discussion

Our study revealed elevated plasma levels of inflammatory mediators in different PAH subgroups and CTEPH at baseline and at 1-year follow-up, whereby CXCL9 and IL-8 may prove to be prognostic markers for CTEPH patients. While this study is exploratory and hypothesis generating, our data indicate an important role for IL-8 and CXCL9 in CHD and CTEPH patients considering the increased plasma levels and the observed correlation with survival.

Conclusion

In conclusion, our studies identified an inflammatory signature that clustered PH patients into WHO classification-independent subgroups that correlated with patient survival.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01716-w.

Chronic Thromboembolic Pulmonary Hypertension - What Have We Learned From Large Animal Models

Chronic thrombo-embolic pulmonary hypertension (CTEPH) develops in a subset of patients after acute pulmonary embolism. In CTEPH, pulmonary vascular resistance, which is initially elevated due to the obstructions in the larger pulmonary arteries, is further increased by pulmonary microvascular remodeling. The increased afterload of the right ventricle (RV) leads to RV dilation and hypertrophy. This RV remodeling predisposes to arrhythmogenesis and RV failure. Yet, mechanisms involved in pulmonary microvascular remodeling, processes underlying the RV structural and functional adaptability in CTEPH as well as determinants of the susceptibility to arrhythmias such as atrial fibrillation in the context of CTEPH remain incompletely understood. Several large animal models with critical clinical features of human CTEPH and subsequent RV remodeling have relatively recently been developed in swine, sheep, and dogs. In this review we will discuss the current knowledge on the processes underlying development and progression of CTEPH, and on how animal models can help enlarge understanding of these processes.

Revisiting a Distinct Entity in Pulmonary Vascular Disease: Chronic Thromboembolic Pulmonary Hypertension (CTEPH)

Chronic thromboembolic pulmonary hypertension (CTEPH) is a specific type of pulmonary hypertension (PH) and the major component of Group 4 pulmonary hypertension (PH). It is caused by pulmonary vasculature obstruction that leads to a progressive increase in pulmonary vascular resistance and, ultimately, to failure of the right ventricle. Pulmonary thromboendarterectomy (PEA) is the only definitive therapy, so a timely diagnosis and early referral to a specialized PEA center to determine candidacy is prudent for a favorable outcome. Percutaneous balloon pulmonary angioplasty (BPA) has a potential role in patients unsuitable for PEA. Medical therapy with riociguat is the only PH-specific medical therapy currently approved for the treatment of inoperable or persistent CTEPH. This review article aims to revisit CTEPH succinctly with a review of prevailing literature.

The Inflammatory Profile of CTEPH-Derived Endothelial Cells Is a Possible Driver of Disease Progression

Chronic thromboembolic pulmonary hypertension (CTEPH) is a form of pulmonary hypertension characterized by the presence of fibrotic intraluminal thrombi and causing obliteration of the pulmonary arteries. Although both endothelial cell (EC) dysfunction and inflammation are linked to CTEPH pathogenesis, regulation of the basal inflammatory response of ECs in CTEPH is not fully understood. Therefore, in the present study, we investigated the role of the nuclear factor (NF)-κB pro-inflammatory signaling pathway in ECs in CTEPH under basal conditions. Basal mRNA levels of interleukin (IL)-8, IL-1β, monocyte chemoattractant protein-1 (MCP-1), C-C motif chemokine ligand 5 (CCL5), and vascular cell adhesion molecule-1 (VCAM-1) were upregulated in CTEPH-ECs compared to the control cells. To assess the involvement of NF-κB signaling in basal inflammatory activation, CTEPH-ECs were incubated with the NF-κB inhibitor Bay 11-7085. The increase in pro-inflammatory cytokines was abolished when cells were incubated with the NF-κB inhibitor. To determine if NF-κB was indeed activated, we stained pulmonary endarterectomy (PEA) specimens from CTEPH patients and ECs isolated from PEA specimens for phospho-NF-κB-P65 and found that especially the vessels within the thrombus and CTEPH-ECs are positive for phospho-NF-κB-P65. In summary, we show that CTEPH-ECs have a pro-inflammatory status under basal conditions, and blocking NF-κB signaling reduces the production of inflammatory factors in CTEPH-ECs. Therefore, our results show that the increased basal pro-inflammatory status of CTEPH-ECs is, at least partially, regulated through activation of NF-κB signaling and potentially contributes to the pathophysiology and progression of CTEPH.

Model of Chronic Thromboembolic Pulmonary Hypertension in Rats Caused by Repeated Intravenous Administration of Partially Biodegradable Sodium Alginate Microspheres

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare and life-threatening complication of pulmonary embolism. As existing animal models of CTEPH do not fully recapitulate complex disease pathophysiology, we report a new rat model for CTEPH evoked by repetitive embolization of the distal pulmonary artery branches with partially biodegradable alginate microspheres (MSs). MSs (180 ± 28 μm) were intravenously administered eight times at 4-day intervals; control animals received saline. The validity of the model was confirmed using transthoracic echocardiography, exercise testing, catheterization of the right ventricle, and histological examination of the lung and heart. The animals in the CTEPH group demonstrated a stable increase in right ventricular systolic pressure (RVSP) and decreased exercise tolerance. Histopathological examination revealed advanced medial hypertrophy in the small pulmonary arteries associated with fibrosis. The diameter of the main pulmonary artery was significantly larger in the CTEPH group than in the control group. Marinobufagenin and endothelin-1 serum levels were significantly elevated in rats with CTEPH. In conclusion, repetitive administration of alginate MSs in rats resulted in CTEPH development characterized by specific lung vasculature remodeling, reduced exercise tolerance, and a persistent rise in RVSP. The developed model can be used for pre-clinical testing of promising drug candidates.

Thrombotic Lesion of the Pulmonary Vessels in Patients with Pulmonary Embolism

After suffering pulmonary embolism (PE), doctors are confronted with various consequences of the disease, from asymptomatic residual pulmonary thrombosis to the formation of chronic thromboembolic pulmonary hypertension (CTEPH). There is also a subgroup of patients who have undergone pulmonary embolism, who experience shortness of breath during physical exertion, absent before pulmonary embolism, or shortened dyspnea preceding PE, combined with residual thrombosis of pulmonary artery (PA) and normal average pressure in PA at rest during catheterization of the right heart (CRH). This condition is defined as chronic thromboembolic pulmonary disease or post thromboembolic syndrome. Pathogenetic aspects of this condition are not fully investigated. It is important to predict the development of postembolic syndrome and to develop algorithms for the diagnosis, treatment and rehabilitation of patients with symptoms and residual pulmonary thrombosis. In case of the development of pulmonary vasculopathy in some patients who have undergone pulmonary embolism, a severe life-threatening condition forms - CTEPH, characterized by an increase in pressure in the pulmonary artery, right heart failure due to the presence of organized blood clots that have entered the pulmonary vascular bed during PE. The volume of thrombotic masses does not always correlate with clinical symptoms, which indicates the importance of microvascular remodeling. If CTEPH is suspected, a diagnostic algorithm is required, including ventilation-perfusion scintigraphy, CT angiopulmonography and catheterization of the right heart. Treating a patient with CTEPH is a difficult task fora doctor. The timely referral of the patient to the center where they are involved in treatment, including surgery and CTEPH is extremely important. Timely performed thrombendarterectomy in some cases allows to completely cure the patient. In the case of inoperable CTEPH or residual pulmonary hypertension after thrombendarterectomy, balloon angioplasty of the PA is used as well as drug treatment with specific drugs that reduce the pressure in the PA (riociguat), endothelin receptor antagonists (bosentan, macitentan), prostanoids (inhalant illoprost) phosphodiesterase-5 inhibitor and combined therapy. In this article we considered some consequences directly related to PE: asymptomatic residual pulmonary thrombosis, chronic thromboembolic pulmonary disease, chronic thromboembolic pulmonary hypertension.

Possible immune regulation mechanisms for the progression of chronic thromboembolic pulmonary hypertension

PURPOSE

This study aimed to screen key genes significantly associated with chronic thromboembolic pulmonary hypertension (CTEPH) and predicted suitable drugs for the treatment of CTEPH from the perspective of immune cells.

METHODS

The dataset GSE130391 was used for this analysis. Differentially expressed genes (DEGs) between the CTEPH and control groups were screened. Abundance of infiltrating immune cells was analyzed and immune-related DEGs were identified. Next, the circular RNA (circRNA)-micro RNA (miRNA)-mRNA network was constructed, followed by functional enrichment analysis. Then, the protein-protein interaction (PPI) network was constructed and drug-gene interactions were predicted. Finally, miRNA and circRNA prediction results were verified by our previously published studies.

RESULTS

Five key immune cell-related DEGs [CD83 molecule (CD83), complement c5a receptor 1 (C5AR1), atypical chemokine receptor 1 (ACKR1), profilin 2 (PFN2), and solute carrier family 2 member 3 (SLC2A3)] were identified. Several circRNA-miRNA-mRNA interactions were obtained, including circ_0022342miR-503-5pSLC2A3 and circ_0002062miR-92b-3p/miR-92a-3pmannosidase alpha class 2A member 1 (MAN2A1). Immune cell for SLC2A3 was eosinophils and for MAN2A1 was regulatory T cells (Tregs). Additionally, Glufosfamide and Kifunensine might be suitable as candidate drugs for CTEPH treatment.

CONCLUSIONS

SLC2A3 and MAN2A1 may be important genes for the pathogenesis of CTEPH. Possible immune regulation mechanisms in CTEPH may be circ_0022342miR-503-5pSLC2A3 and circ_0002062miR-92b-3p/miR-92a-3pMAN2A1. These results may be helpful for the diagnosis and treatment of CTEPH from the perspective of immunology.

Balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension: State of the art

Chronic thromboembolic pulmonary hypertension (CTEPH) is a complex chronic disease in which pulmonary artery stenosis or obstruction caused by organized thrombus can lead to increased pulmonary artery pressure and pulmonary vascular resistance, ultimately triggering progressive right heart failure and death. Currently, its exact mechanism is not fully understood. Pulmonary endarterectomy (PEA) has immediate effects with low perioperative mortality and satisfactory prognosis in experienced expert centers for CTEPH patients with proximal lesions. Nevertheless, 37% of patients are deemed unsuitable for PEA surgery due to comorbidities and other factors, and nearly half of the operated patients have residual or recurrent pulmonary hypertension. Riociguat is the only approved drug for CTEPH, although its effect is limited. Balloon pulmonary angioplasty (BPA) is a promising alternative treatment for patients with CTEPH. After more than 30 years of development and refinements, emerging evidence has confirmed its role in patients with inoperable CTEPH or residual/recurrent pulmonary hypertension, with acceptable complications and comparable long-term prognosis to PEA. This review summarizes the pathophysiology of CTEPH, BPA history and development, therapeutic principles, indications and contraindications, interventional procedures, imaging modalities, efficacy and prognosis, complications and management, bridging and hybrid therapies, ongoing clinical trials and future prospects.

Research progress on the pathogenesis of CTEPH

Chronic thromboembolic pulmonary hypertension (CTEPH) is an established long-term complication of pulmonary thromboembolism (PTE). However, studies have shown that many patients with a definitive CTEPH diagnosis have no history of symptomatic PTE, suggesting that PTE is not the only cause of CTEPH. Despite extensive progress in research on pulmonary hypertension in recent years, due to a lack of relevant studies on the pathophysiology of CTEPH, implementing pulmonary endarterectomy (PEA) in patients has many challenges, and the prognosis of patients with CTEPH is still not optimistic. Therefore, revealing the pathogenesis of CTEPH would be of great significance for understanding the occurrence and development of CTEPH, developing relevant drug treatment studies and formulating intervention strategies, and may provide new preventive measures. This article summarizes the current research progress in CTEPH pathogenesis from the perspective of risk factors related to medical history, abnormal coagulation and fibrinolytic mechanisms, inflammatory mechanisms, genetic susceptibility factors, angiogenesis, in situ thrombosis, vascular remodeling, and other aspects.

Formulation and Characterization of Solid Lipid Nanoparticles Loading RF22-c, a Potent and Selective 5-LO Inhibitor, in a Monocrotaline-Induced Model of Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is a rare but fatal disease characterized by persistent elevated blood pressure in the pulmonary circulation, due to increased resistance to blood flow, through the lungs. Advances in the understanding of the pathobiology of PAH clarify the role of leukotrienes (LTs) that appear to be an exciting new target for disease intervention. Over the years, our group has long investigated this field, detecting the 1,2-benzoquinone RF-22c as the most powerful and selective competitive inhibitor of the enzyme 5-lipoxygenase (5-LO). With the aim to improve the bioavailability of RF-22c and to confirm the role of 5-LO as therapeutic strategy for PAH treatment, we developed a solid lipid nanoparticle (SLN) loaded with drug. Therefore, in monocrotaline (MCT) rat model of PAH, the role of 5-LO has been investigated through the formulation of RF-22c-SLN. The rats were randomly grouped into control group, MCT group, and MCT + RF22-c group. After 21 days, all the animals were sacrificed to perform functional and histological evaluations. RF22-c-SLN treatment was able to significantly reduce the mean pulmonary arterial pressure (mPAP) and precapillary resistance (R-pre) compared to the MCT group. The MCT induced rise in medial wall thickness of pulmonary arterioles, and the cardiomyocytes width were significantly attenuated by RF22-c-SLN formulation upon treatment. The results showed that the selective inhibition of 5-LO improved hemodynamic parameters as well as vascular and cardiac remodeling by preventing induced pulmonary hypertension. The improved sustained release properties and targeting abilities achieved with the innovative nanotechnological approach may be therapeutically beneficial for PAH patients as a consequence of the increase of pharmacological effects and of the possible reduction and/or optimization of the drug frequency of administration.

Pulmonary Arterial Hypertension and Chronic Thromboembolic Pulmonary Hypertension: An Immunological Perspective

Pulmonary hypertension (PH) is a debilitating progressive disease characterized by increased pulmonary arterial pressures, leading to right ventricular (RV) failure, heart failure and, eventually, death. Based on the underlying conditions, PH patients can be subdivided into the following five groups: (1) pulmonary arterial hypertension (PAH), (2) PH due to left heart disease, (3) PH due to lung disease, (4) chronic thromboembolic PH (CTEPH), and (5) PH with unclear and/or multifactorial mechanisms. Currently, even with PAH-specific drug treatment, prognosis for PAH and CTEPH patients remains poor, with mean five-year survival rates of 57%-59% and 53%-69% for PAH and inoperable CTEPH, respectively. Therefore, more insight into the pathogenesis of PAH and CTEPH is highly needed, so that new therapeutic strategies can be developed. Recent studies have shown increased presence and activation of innate and adaptive immune cells in both PAH and CTEPH patients. Moreover, extensive biomarker research revealed that many inflammatory and immune markers correlate with the hemodynamics and/or prognosis of PAH and CTEPH patients. Increased evidence of the pathological role of immune cells in innate and adaptive immunity has led to many promising pre-clinical interventional studies which, in turn, are leading to innovative clinical trials which are currently being performed. A combination of immunomodulatory therapies might be required besides current treatment based on vasodilatation alone, to establish an effective treatment and prevention of progression for this disease. In this review, we describe the recent progress on our understanding of the involvement of the individual cell types of the immune system in PH. We summarize the accumulating body of evidence for inflammation and immunity in the pathogenesis of PH, as well as the use of inflammatory biomarkers and immunomodulatory therapy in PAH and CTEPH.

A multifaceted investigation into molecular associations of chronic thromboembolic pulmonary hypertension pathogenesis

Purpose

Chronic thromboembolic pulmonary hypertension is characterized by incomplete thrombus resolution following acute pulmonary embolism, leading to pulmonary hypertension and right ventricular dysfunction. Conditions such as thrombophilias, dysfibrinogenemias, and inflammatory states have been associated with chronic thromboembolic pulmonary hypertension, but molecular mechanisms underlying this disease are poorly understood. We sought to characterize the molecular and functional features associated with chronic thromboembolic pulmonary hypertension using a multifaceted approach.

Methods

We utilized functional assays to compare clot lysis times between chronic thromboembolic pulmonary hypertension patients and multiple controls. We then performed immunohistochemical characterization of tissue from chronic thromboembolic pulmonary hypertension, pulmonary arterial hypertension, and healthy controls, and examined RNA expression patterns of cultured lymphocytes and pulmonary arterial specimens. We then confirmed RNA expression changes using immunohistochemistry, immunofluorescence, and Western blotting in pulmonary arterial tissue.

Results

Clot lysis times in chronic thromboembolic pulmonary hypertension patients are similar to multiple controls. Chronic thromboembolic pulmonary hypertension endarterectomized tissue has reduced expression of both smooth muscle and endothelial cell markers. RNA expression profiles in pulmonary arteries and peripheral blood lymphocytes identified differences in RNA transcript levels related to inflammation and growth factor signaling, which we confirmed using immunohistochemistry. Gene expression data also suggested significant alterations in metabolic pathways, and immunofluorescence and Western blot experiments confirmed that unglycosylated CD36 and adiponectin expression were increased in chronic thromboembolic pulmonary hypertension versus controls.

Conclusions

Our data do not support impaired clot lysis underlying chronic thromboembolic pulmonary hypertension, but did demonstrate distinct molecular patterns present both in peripheral blood and in pathologic specimens of chronic thromboembolic pulmonary hypertension patients suggesting that altered metabolism may play a role in chronic thromboembolic pulmonary hypertension pathogenesis.

Chronic Thromboembolic Pulmonary Hypertension-Management Strategies and Outcomes

Chronic thromboembolic pulmonary hypertension (CTEPH) is rare but complex pathophysiological disease with hallmark features of chronic thrombotic mechanical obstruction, right ventricular dysfunction, and secondary pulmonary arteriopathy. It increasingly is being understood that chronic infection/inflammation, abnormal fibrinolysis, and cytokines play an important role in pathogenesis such that only a subset of patients with pulmonary embolism develop CTEPH. Diagnosis remains challenging given the lack of early clinical signs and overlap with other cardiopulmonary conditions. Pulmonary endarterectomy is the surgical procedure of choice with good postoperative survival and functional outcomes, especially when done at high-volume centers with a multidisciplinary approach. There has been a resurgence of balloon pulmonary angioplasty (BPA) as salvage therapy for inoperable CTEPH or in its newfound hybrid role for persistent postoperative pulmonary hypertension with excellent 1-year and 3-year survival. Use of riociguat has shown promising improvements in functional outcomes up to 2 years after initiation. Endothelin receptor antagonists serve a supplemental role postoperatively or in inoperable CTEPH. The role of drug therapy preoperatively or in tandem with BPA is currently under investigation.

Proteomic Analyses of Endarterectomized Tissues from Patients with Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND

The pathogenesis of chronic thromboembolic pulmonary hypertension (CTEPH) is largely unknown. Proteomics offers an approach to overview the molecular activities and signal transduction pathways involved in specific disease processes.

OBJECTIVES

In this study, the expression of proteins in endarterectomized tissues from patients with CTEPH was investigated in a novel strategy to explore the pathophysiology of this disease.

METHODS

We used the iTRAQ (isobaric tag for relative and absolute quantitation) approach combined with a Thermo Scientific Q Exactive MS analysis to compare the protein profiles in endarterectomized tissues from CTEPH patients and that of the control samples (mixture of cultured human pulmonary artery endothelial cells, human pulmonary artery smooth muscle cells, and human pulmonary fibroblasts). GO and KEGG analyses were performed to understand the functional classification and molecular activities of all the tissue-specific proteins, and the involved signal transduction pathways.

RESULTS

Six hundred and seventy-nine tissue-specific proteins were detected. Bioinformatic analysis showed that the major biological processes involving these proteins were: response to wounding, defense response, acute inflammatory response, immune response, complement activation, and blood coagulation. The main pathways involved were: complement and coagulation cascade, systemic lupus erythematosus, extracellular matrix-receptor interaction, cell adhesion molecules, FcεRI signaling, and leukocyte transendothelial migration.

CONCLUSIONS

The present study revealed that immune and defense response might play an important role in CTEPH.

The role of chemokines and chemokine receptors in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by progressive pulmonary artery remodelling leading to increased right ventricular pressure overload, which results in right heart failure and premature death. Inflammation plays a central role in the development of PAH, and the recruitment and function of immune cells are tightly regulated by chemotactic cytokines called chemokines. A number of studies have shown that the development and progression of PAH are associated with the dysregulated expression of several chemokines and chemokine receptors in the pulmonary vasculature. Moreover, some chemokines are differentially regulated in the pressure-overloaded right ventricle. Recent studies have tested the efficacy of pharmacological agents targeting several chemokines and chemokine receptors for their effects on the development of PAH, suggesting that these receptors could serve as useful therapeutic targets. In this review, we provide recent insights into the role of chemokines and chemokine receptors in PAH and RV remodelling and the opportunities and roadblocks in targeting them. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

The Prognostic Value of Soluble ST2 in Adults with Pulmonary Hypertension

Soluble ST2 (sST2) is upregulated in response to myocardial stress and may serve as biomarker in adults with pulmonary hypertension (PH). This prospective cohort study investigated sST2 levels and its association with echocardiographic and hemodynamic measures, and adverse clinical outcomes in adults with PH of different etiologies. sST2 was measured during the diagnostic right heart catheterization for PH, in adult patients enrolled between May 2012 and October 2016. PH due to left heart failure was excluded. The association between sST2 and a primary endpoint composed of death or lung transplantation and a secondary composite endpoint including death, lung transplantation or heart failure, was investigated using Cox regression with adjustment for NT-proBNP. In total 104 patients were included (median age was 59 years, 66% woman, 51% pulmonary arterial hypertension). Median sST2 was 28 [IQR 20–46] ng/mL. Higher sST2 was associated with worse right ventricular dysfunction and higher mean pulmonary and right atrial pressures. Median follow-up was 3.3 [IQR 2.3–4.6] years. The primary and secondary endpoint occurred in 33 (31.7%) and 43 (41.3%) patients, respectively. sST2 was significantly associated with both endpoints (HR per 2-fold higher value 1.53, 95%CI 1.12–2.07, p = 0.007 and 1.45, 95%CI 1.10–1.90, p = 0.008, respectively). However, after adjustment for NT-proBNP, both associations did not reach statistical significance. In conclusions, higher sST2 levels are associated with more severe PH and right ventricular dysfunction and yields prognostic value in adults with PH, although not independently of NT-proBNP.

Chronic Thromboembolic Pulmonary Hypertension: Evolving Therapeutic Approaches for Operable and Inoperable Disease

Chronic thromboembolic pulmonary hypertension (CTEPH), a rare consequence of an acute pulmonary embolism, is a disease that is underdiagnosed, and surgical pulmonary thromboendarterectomy (PTE) remains the preferred therapy. However, determination of operability is multifactorial and can be challenging. There is growing excitement for the percutaneous treatment of inoperable CTEPH with data from multiple centers around the world showing the clinical feasibility of balloon pulmonary angioplasty. Riociguat remains the only approved medical therapy for CTEPH patients deemed inoperable or with persistent pulmonary hypertension after PTE. We recommend that expert multidisciplinary CTEPH teams be developed at individual institutions. Additionally, optimal and standardized techniques for balloon pulmonary angioplasty need to be developed along with dedicated interventional equipment and appropriate training standards. In the meantime, the percutaneous revascularization option is appropriate for patients deemed inoperable in combination with targeted medical therapy, or those who have failed to benefit from surgery.