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Pulmonary arterial hypertension (PAH) is characterized by a progressive accumulation of pulmonary artery smooth muscle cells (PA-SMCs) in pulmonary arterioles leading to the narrowing of the lumen, right heart failure, and death. Although most studies have supported the notion of a role for IL-6/glycoprotein 130 (gp130) signaling in PAH, it remains unclear how this signaling pathway determines the progression of the disease. Here, we identify ectopic upregulation of membrane-bound IL-6 receptor (IL6R) on PA-SMCs in PAH patients and in rodent models of pulmonary hypertension (PH) and demonstrate its key role for PA-SMC accumulation in vitro and in vivo. Using Sm22a-Cre Il6rfl/fl, which lack Il6r in SM22A-expressing cells, we found that these animals are protected against chronic hypoxia-induced PH with reduced PA-SMC accumulation, revealing the potent pro-survival potential of membrane-bound IL6R. Moreover, we determine that treatment with IL6R-specific antagonist reverses experimental PH in two rat models. This therapeutic strategy holds promise for future clinical studies in PAH.

Background Although pulmonary vascular bed has been the main subject of research for many years in pulmonary hypertension (PH), interest has recently started to divert towards the possibility of a co-existing peripheral microangiopathy. The aim of the current study was to investigate the presence of nailfold video-capillaroscopic (NVC) structural changes in patients with precapillary PH and to identify possible associations of NVC measurements with markers of disease severity. Methods Α prospective case–control study was performed in 28 consecutive patients with precapillary PH [14 with idiopathic pulmonary arterial hypertension (IPAH) and 14 with chronic thromboembolic pulmonary hypertension (CTEPH)] and 30 healthy controls. NVC quantitative and qualitative parameters were evaluated using Optilia Digital Capillaroscope. To ensure inter-observer repeatability capillaroscopic images were reviewed by two independent investigators. For multiple comparisons among continuous variables, one-way ANOVA or the Kruskal–Wallis test were used. Differences between the groups were tested with post-hoc analysis with adjustment for multiple comparisons (Bonferroni test). Results Both IPAH (71.4% were women, mean age 53.1 ± 13.4 years) and CTEPH (64.3% women, mean age 60.9 ± 14.4 years) groups presented reduced capillary density compared to healthy controls (8.4 ± 1.2 loops/mm and 8.0 ± 1.2 loops/mm vs. 9.7 ± 0.81 loops/mm, p < 0.001) and increased loop width (15.7 ± 3.9 μm and 15.8 ± 1.9 μm vs. 11.5 ± 2.3 μm, p < 0.001). More than half of patients with IPAH presented microhaemorrhages on capillary nailfold, while increased shape abnormalities in capillary morphology and more capillary thrombi per linear mm were detected in patients with CTEPH compared to patients with IPAH and healthy controls. All PH patients presented a non-specific NVC pattern compared to controls (p < 0.001). Conclusion The findings of the study reveal a degree of significant peripheral microvascular alterations in patients with IPAH and CTEPH, suggesting a generalized impairment of peripheral microvasculature in pulmonary vascular disease.

Pulmonary arterial hypertension (PAH) is a rare but fatal disease. Current treatments increase life expectancy but have limited impact on the progressive pulmonary vascular remodelling that drives PAH. Osteoprotegerin (OPG) is increased within serum and lesions of patients with idiopathic PAH and is a mitogen and migratory stimulus for pulmonary artery smooth muscle cells (PASMCs). Here, we report that the pro-proliferative and migratory phenotype in PASMCs stimulated with OPG is mediated via the Fas receptor and that treatment with a human antibody targeting OPG can attenuate pulmonary vascular remodelling associated with PAH in multiple rodent models of early and late treatment. We also demonstrate that the therapeutic efficacy of the anti-OPG antibody approach in the presence of standard of care vasodilator therapy is mediated by a reduction in pulmonary vascular remodelling. Targeting OPG with a therapeutic antibody is a potential treatment strategy in PAH. Pulmonary arterial hypertension (PAH) is characterised by progressive pulmonary vascular remodelling. Here, Arnold et al. develop a therapeutic antibody targeting osteoprotegerin and find it attenuates pulmonary vascular remodelling in multiple rodent models of PAH, alone or in combination with standard of care vasodilator therapy.

Background Pulmonary arterial hypertension is a life-threatening progressive disorder characterised by high blood pressure (hypertension) in the arteries of the lungs (pulmonary artery). Although treatable, there is no known cure for this rare disorder, and its exact cause is unknown. Mutations in the bone morphogenetic protein receptor type-2 (BMPR2) are the most common genetic cause of familial pulmonary arterial hypertension. This study represents the first-ever trial of treatments aimed at directly rescuing the BMPR2 pathway, repurposing two drugs that have shown promise at restoring levels of BMPR2 signalling: hydroxychloroquine and phenylbutyrate. Methods This three-armed phase II precision medicine study will investigate BMPR2 target engagement and explore the efficacy of two repurposed therapies in pulmonary arterial hypertension patients with BMPR2 mutations. Patients will be stratified based on two BMPR2 mutation classes: missense and haploinsufficient mutations. Eligible subjects will be randomised to one of the three arms (two active therapy arms and a placebo arm, all plus standard of care) following a Bayesian response-adaptive design implemented independently in each stratum and updated in response to a novel panel of primary biomarkers designed to assess biological modification of the disease. Discussion The results of this trial will provide the first randomised evidence of the efficacy of these therapies to rescue BMPR2 function and will efficiently explore the potential for a differential response of these therapies per mutation class to address causes rather than consequences of this rare disease. Trial registration The study has been registered with ISRCTN (ISRCTN10304915, 22/09/2023).

Idiopathic/heritable pulmonary arterial hypertension has a poor prognosis despite the available therapeutic options. Survival of Japanese patients with this disease entity has not been reported in the multicenter setting. A retrospective study of 141 patients with idiopathic/heritable pulmonary arterial hypertension treated at 3 pulmonary hypertension centers in Japan from 1992 to 2012 investigated survival and determinants of survival. Mean survival time from treatment initiation was 14.7 ± 0.8 years (95% confidence interval, 13.1 to 16.3 years) and the 1-, 3-, 5-, and 10-year survival rates were 97.9%, 92.1%, 85.8%, and 69.5%, respectively. Patients showed significant improvement in exercise capacity and hemodynamics after treatment. Patients with 6-minute walk distance >372 m, mean pulmonary arterial pressure ≤46 mm Hg, and cardiac index >2.5 L/min/m2 at follow-up had a significantly better prognosis. Most patients (99.2%) were receiving pulmonary hypertension-targeted drugs at follow-up. Use of endothelin receptor antagonists and intravenous epoprostenol were related to survival in the univariate analysis. Among the patients who were on intravenous epoprostenol therapy, those with endothelin receptor antagonists had a significantly better prognosis, whereas patients on warfarin had a significantly worse prognosis. In conclusion, survival of Japanese patients with idiopathic/heritable pulmonary arterial hypertension in this study was good, showing improvement in hemodynamic parameters supported by pulmonary hypertension-targeted drugs.

Background Hyperglycemia upon admission is associated with poor prognosis of many cardiovascular diseases. However, the relationship of stress hyperglycemia ratio (SHR), admission blood glucose (ABG), and hemoglobin A1c (HbA1c) with pulmonary hypertension has not been reported. This study aimed to explore the association of hyperglycemia indices with disease severity and long-term adverse outcomes in patients with idiopathic pulmonary arterial hypertension (IPAH). Methods This multi-center cohort study included 625 consecutive patients diagnosed with or treated for IPAH between January 2015 and June 2023. SHR was calculated using the followings: ABG (mmol/L)/(1.59 × HbA1c [%] − 2.59). The primary endpoint was defined as clinical worsening events. Multivariable Cox regression and restricted cubic spline analyses were employed to evaluate the association of SHR, ABG, and HbA1c with endpoint events. The mediating effect of pulmonary hemodynamics was evaluated to investigate the potential mechanism between hyperglycemia and clinical outcomes. Results During a mean follow-up period of 3.8 years, 219 (35.0%) patients experienced all-cause death or clinical worsening events. Hyperglycemia indices correlated with well-validated variables that reflected the severity of IPAH, such as the World Health Organization functional class, 6-min walk distance, and N-terminal pro-brain natriuretic peptide levels. Multivariable Cox regression analyses indicated that SHR (hazard ratio [HR] 1.328, 95% confidence intervals [CI]: 1.185, 1.489 per 0.1-unit increment, P  < 0.001) and ABG (HR 1.317, 95% CI: 1.134, 1.529 per 1.0-unit increment, P  < 0.001) were independent predictors of primary endpoint events. Mediation analysis indicated that pulmonary vascular resistance mediated 5.65% and 14.62% of the associations between SHR and ABG and clinical worsening events, respectively. The addition of SHR significantly improved reclassification, discrimination ability, and model fit beyond the clinical risk prediction model. Conclusions SHR is positively associated with clinical worsening in patients with IPAH. The association appeared to be partially mediated through the pathway of pulmonary vascular remodeling, indicating that SHR may serve as a valuable indicator for providing additional risk information.

Background Insulin resistance (IR) plays an important role in the pathophysiology of cardiovascular disease. Recent studies have shown that diabetes mellitus and impaired lipid metabolism are associated with the severity and prognosis of idiopathic pulmonary arterial hypertension (IPAH). However, the relationship between IR and pulmonary hypertension is poorly understood. This study explored the association between four IR indices and IPAH using data from a multicenter cohort. Methods A total of 602 consecutive participants with IPAH were included in this study between January 2015 and December 2022. The metabolic score for IR (METS-IR), triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio, triglyceride and glucose (TyG) index, and triglyceride-glucose-body mass index (TyG-BMI) were used to quantify IR levels in patients with IPAH. The correlation between non-insulin-based IR indices and long-term adverse outcomes was determined using multivariate Cox regression models and restricted cubic splines. Results During a mean of 3.6 years’ follow-up, 214 participants experienced all-cause death or worsening condition. Compared with in low to intermediate-low risk patients, the TG/HDL-C ratio (2.9 ± 1.7 vs. 3.3 ± 2.1, P = 0.003) and METS-IR (34.5 ± 6.7 vs. 36.4 ± 7.5, P < 0.001) were significantly increased in high to intermediate-high risk patients. IR indices correlated with well-validated variables that reflected the severity of IPAH, such as the cardiac index and stroke volume index. Multivariate Cox regression analyses indicated that the TyG-BMI index (hazard ratio [HR] 1.179, 95% confidence interval [CI] 1.020, 1.363 per 1.0-standard deviation [SD] increment, P = 0.026) and METS-IR (HR 1.169, 95% CI 1.016, 1.345 per 1.0-SD increment, P = 0.030) independently predicted adverse outcomes. Addition of the TG/HDL-C ratio and METS-IR significantly improved the reclassification and discrimination ability beyond the European Society of Cardiology (ESC) risk score. Conclusions IR is associated with the severity and long-term prognosis of IPAH. TyG-BMI and METS-IR can independently predict clinical worsening events, while METS-IR also provide incremental predictive performance beyond the ESC risk stratification.

Since its association with familial pulmonary arterial hypertension (PAH) in 2000, Bone Morphogenetic Protein Receptor II (BMPR2) and its related signaling pathway have become recognized as a key regulator of pulmonary vascular homeostasis. Herein, we define BMPR2 deficiency as either an inactivation of the receptor, decreased receptor expression, or an impairment of the receptor’s downstream signaling pathway. Although traditionally the phenotypic consequences of BMPR2 deficiency in PAH have been thought to be limited to the pulmonary vasculature, there is evidence that abnormalities in BMPR2 signaling may have consequences in many other organ systems and cellular compartments. Revisiting how BMPR2 functions throughout health and disease in cells and organs beyond the lung vasculature may provide insight into the contribution of these organ systems to PAH pathogenesis as well as the potential systemic manifestation of PAH. Here we review our knowledge of the consequences of BMPR2 deficiency across multiple organ systems.

Background Malnutrition is common in patients with chronic cardiovascular disease and is associated with significantly higher all-cause mortality. Approximately one-third of patients with heart failure are malnourished. However, the relationship between malnutrition and idiopathic pulmonary arterial hypertension (IPAH) remains unclear. This study aimed to clarify the prognostic value of malnutrition in patients with IPAH. Methods A total of 432 consecutive participants with IPAH were included in this study between March 2013 and August 2021. Three common malnutrition assessment tools, including the geriatric nutritional risk index (GNRI), prognostic nutritional index (PNI), and controlling nutritional status (CONUT) score, were used to evaluate the nutritional status of patients with IPAH. The relationships between the malnutrition tools and long-term adverse outcomes were determined using restricted cubic splines and multivariate Cox regression models. Results During a mean follow-up of 3.1 years, 158 participants experienced clinical worsening or all-cause death. Patients were stratified into the low-, intermediate- and high-risk groups based on the European Society of Cardiology (ESC) risk stratification, and the PNI (55.9 ± 5.7 vs. 54.4 ± 7.2 vs. 51.1 ± 7.1, P = 0.005) and CONUT score (2.1 ± 0.9 vs. 2.5 ± 1.2 vs. 3.3 ± 1.1, P < 0.001) identified these patient groups better than the GNRI. All three malnutrition tools were associated with well-validated variables that reflected IPAH severity, such as the World Health Organization functional class, 6-min walk distance, and N-terminal pro-brain natriuretic peptide level. The CONUT score exhibited better predictive ability than both the GNRI (ΔAUC = 0.059, P < 0.001) and PNI (ΔAUC = 0.095, P < 0.001) for adverse outcomes and significantly improved reclassification and discrimination beyond the ESC risk score. Multivariable Cox regression analysis indicated that only the CONUT score (hazard ratio = 1.363, 95% confidence interval 1.147, 1.619 per 1.0-standard deviation increment, P < 0.001) independently predicted adverse outcomes. Conclusions The malnutrition status was associated with disease severity in patients with IPAH. The CONUT score provided additional information regarding the risk of clinically worsening events, making it a meaningful risk stratification tool for these patients.

Pulmonary arterial hypertension is characterized by endothelial dysregulation, but global changes in gene expression have not been related to perturbations in function. RNA sequencing was used to discriminate changes in transcriptomes of endothelial cells cultured from lungs of patients with idiopathic pulmonary arterial hypertension versus control subjects and to assess the functional significance of major differentially expressed transcripts. The endothelial transcriptomes from the lungs of seven control subjects and six patients with idiopathic pulmonary arterial hypertension were analyzed. Differentially expressed genes were related to bone morphogenetic protein type 2 receptor (BMPR2) signaling. Those down-regulated were assessed for function in cultured cells and in a transgenic mouse. Fold differences in 10 genes were significant (P < 0.05), four increased and six decreased in patients versus control subjects. No patient was mutant for BMPR2. However, knockdown of BMPR2 by siRNA in control pulmonary arterial endothelial cells recapitulated 6 of 10 patient-related gene changes, including decreased collagen IV (COL4A1, COL4A2) and ephrinA1 (EFNA1). Reduction of BMPR2-regulated transcripts was related to decreased β-catenin. Reducing COL4A1, COL4A2, and EFNA1 by siRNA inhibited pulmonary endothelial adhesion, migration, and tube formation. In mice null for the EFNA1 receptor, EphA2, versus control animals, vascular endothelial growth factor receptor blockade and hypoxia caused more severe pulmonary hypertension, judged by elevated right ventricular systolic pressure, right ventricular hypertrophy, and loss of small arteries. The novel relationship between BMPR2 dysfunction and reduced expression of endothelial COL4 and EFNA1 may underlie vulnerability to injury in pulmonary arterial hypertension.