Sex-specific Genetic Determinants of Right Ventricular Structure and Function.

RATIONALE: While sex differences in right heart phenotypes have been observed, the molecular drivers remain unknown. OBJECTIVES: To provide biological insights into sex differences in the structure and function of the right ventricle (RV) using common genetic variation. METHODS: RV phenotypes were obtained from cardiac magnetic resonance imaging in 18,156 women and 16,171 men from the UK Biobank. Observational analyses and sex-stratified genome-wide association studies were performed. Candidate female-specific loci were evaluated against invasively measured cardiac performance in 479 female patients with idiopathic or heritable pulmonary arterial hypertension (PAH), recruited to the UK NIHR BioResource Rare Diseases study. MEASUREMENTS AND MAIN RESULTS: Sex was associated with differences in RV volumes and ejection fraction in models adjusting for left heart counterparts, blood pressure, lung function and sex hormone levels. Six genome-wide significant loci (13%) revealed heterogeneity of allelic effects between women and men, and significant sex-by-genotype interaction. These included two sex-specific candidate loci present in women only: a locus for RV ejection fraction in BMPR1A and a locus for RV end-systolic volume near DMRT2. Epigenetic data in RV tissue indicate that variation at the BMPR1A locus likely alters transcriptional regulation. In female patients with PAH, a variant located in the promoter of BMPR1A was significantly associated with cardiac index (effect size 0.16 l/min/m2), despite similar RV afterload. CONCLUSIONS: BMPR1A has emerged as a biologically plausible candidate gene for female-specific genetic determination of RV function, showing associations with cardiac performance under chronically increased afterload in female patients with PAH.

Right ventricular strain to systolic pulmonary artery pressure ratio in response to treatment of pulmonary arterial hypertension.

The RVFWLS/PASP ratio, a novel surrogate for ventriculoarterial coupling, showed sensitivity to afterload-lowering treatment and the magnitude of change informed on long-term outcomes in PAH https://bit.ly/4cRtREC.

[Genetic diagnostics and molecular approaches in pulmonary arterial hypertension]. / Genetische Diagnostik und molekulare Ansätze bei pulmonalarterieller Hypertonie.

The recently published new European guidelines for diagnosis and treatment of pulmonary hypertension now offer the so far most extensive description of genetic testing and counselling for pulmonary arterial hypertension patients. In addition, the importance of a clinical screening of healthy mutation carriers is highlighted as well as the genetic testing of patients with a suspicion of pulmonary veno-occlusive disease. We frame the respective parts of the guidelines on genetic testing and counselling in the context of recent data and provide comments. Finally, we give an outlook on novel molecular approaches starting from Sotatercept, addressing ion channels and novel therapeutic developments.

[Targeted therapy for pulmonary arterial hypertension in patients without comorbidities]. / Gezielte medikamentöse Therapie der pulmonalarteriellen Hypertonie bei Patient*innen ohne Komorbiditäten.

The 2022 guidelines on pulmonary hypertension from the European Society of Cardiology (ESC) and the European Respiratory Society (ERS) provide therapeutic strategies that account for the variability in the clinical presentation of newly diagnosed patients. We summarize treatment recommendations for pulmonary arterial hypertension (PAH) in patients without significant comorbidities, particularly for idiopathic, hereditary, drug/toxin-induced, or connective tissue disease-associated PAH. In this group of patients, multidimensional assessments for short-term mortality risk guide initial treatment decisions and treatment decisions during follow-up. Upfront dual combination therapy (phosphodiesterase type-5 inhibitor and endothelin receptor antagonist) is recommended for low- and intermediate-risk patients, and triple therapy including a parenteral prostacyclin should be considered in high- or intermediate-high-risk patients. If a low or intermediate-low-risk profile cannot be achieved during therapy, sequential add-on therapy escalation with parenteral prostacyclin or a prostacyclin receptor agonist should be considered, and switching from a phosphodiesterase type-5 inhibitor to a guanylate cyclase stimulator may also be considered.

Residual risk identified in routine noninvasive follow-up assessments in pulmonary arterial hypertension.

Background: The 2022 ESC/ERS guidelines on pulmonary hypertension recommend noninvasive risk assessments based on three clinical variables during follow-up in patients with pulmonary arterial hypertension (PAH). We set out to test whether residual risk can be captured from routinely measured noninvasive clinical variables during follow-up in PAH. Methods: We retrospectively studied 298 incident PAH patients from a German pulmonary hypertension centre who underwent routine noninvasive follow-up assessments including exercise testing, echocardiography, electrocardiography, pulmonary function testing and biochemistry. To select variables, we used least absolute shrinkage and selection operator (LASSO)-regularised Cox regression models. Outcome was defined as mortality or lung transplant after first follow-up assessment. Results: 12 noninvasive variables that were associated with outcomes in a training sub-cohort (n=208) after correction for multiple testing entered LASSO modelling. A model combining seven variables discriminated 1-year (area under the curve (AUC) 0.83, 95% confidence interval (CI) 0.68-0.99, p=8.4×10-6) and 3-year (AUC 0.81, 95% CI 0.70-0.92, p=2.9×10-8) outcome status in a replication sub-cohort (n=90). The model's discriminatory ability was comparable to that of the guideline approach in the replication sub-cohort. From the individual model components, World Health Organization functional class, 6-min walking distance and the tricuspid annular plane systolic excursion to systolic pulmonary arterial pressure (TAPSE/sPAP) ratio were sensitive to treatment initiation. Addition of TAPSE/sPAP ratio to the guideline approach numerically increased its ability to discriminate outcome status. Conclusion: Our real-world data suggest that residual risk can be captured by noninvasive clinical procedures during routine follow-up assessments in patients with PAH and highlights the potential use of echocardiographic imaging to refine risk assessment.

Clinical phenotyping of plasma thrombospondin-2 reveals relationship to right ventricular structure and function in pulmonary hypertension.

Background: Converging evidence from proteogenomic analyses prioritises thrombospondin-2 (TSP2) as a potential biomarker for idiopathic or heritable pulmonary arterial hypertension (PAH). We aimed to assess TSP2 levels in different forms of pulmonary hypertension (PH) and to define its clinical phenotype. Methods: Absolute concentrations of TSP2 were quantified in plasma samples from a prospective single-centre cohort study including 196 patients with different forms of PH and 16 disease controls (suspected PH, but normal resting pulmonary haemodynamics). In an unbiased approach, TSP2 levels were related to 152 clinical variables. Results: Concentrations of TSP2 were increased in patients with PH versus disease controls (p<0.001 for group comparison). The discriminatory ability of TSP2 levels to distinguish between patients and controls was superior to that of N-terminal pro-brain natriuretic peptide (p=0.0023 for comparison of areas under the curve). Elevation of TSP2 levels was consistently found in subcategories of PAH, in PH due to lung disease and due to left heart disease. Phenotypically, TSP2 levels were robustly related to echocardiographic markers that indicate the right ventricular (RV) response to chronically increased afterload with increased levels in patients with impaired systolic function and ventriculoarterial uncoupling. Focusing on PAH, increased TSP2 levels were able to distinguish between adaptive and maladaptive RV phenotypes (area under the curve 0.87, 95% CI 0.76-0.98). Interpretation: The study indicates that plasma TSP2 levels inform on the presence of PH and associate with clinically relevant RV phenotypes in the setting of increased afterload, which may provide insight into processes of RV adaptability.

[Intimal pulmonary sarcoma: A case report of a rare differential diagnosis of chronic thromboembolic pulmonary hypertension]. / Das intimale Sarkom der Pulmonalarterie ­ Fallbericht einer seltenen Differenzialdiagnose der chronisch thromboembolischen pulmonalen Hypertonie.

Pulmonary angiosarcoma is a rare and malignant disease of the blood vessels. Initially, it can be misdiagnosed as chronic thromboembolic hypertension (CTEPH). In CTEPH, there is increased pressure and resistance of the pulmonary arteries following persistent obstruction of pulmonary circulation from (recurrent) thromboembolism despite adequate anticoagulative treatment.A 76-year-old patient was referred to our centre for pulmonary hypertension after a central, left-sided, subacute pulmonary thromboembolism had been observed 7 months earlier. It was treated with apixaban, but the patient described persistent dyspnoea and cough. We observed severely reduced diffusion capacity, ineffective ventilation during cardiopulmonary exercise testing and right heart strain on echocardiograph, signs that are in agreement with suspected CTEPH. Computer tomography of the chest showed a persistent, size-constant obliteration of the left main pulmonary artery, and ventilation perfusion scan confirmed complete interruption of perfusion. We suspected malignancy; PET-CT scan confirmed metabolically active lesions. Histopathological examination of a sample obtained from the lesion by endobronchial ultrasound-guided needle aspiration showed a sarcomatous tumour with amplification of the MDM2-gene. We diagnosed an intimal angiosarcoma of the left pulmonary artery and referred the patient to pneumectomy.Angiosarcoma of the pulmonary arteries is a rare differential diagnosis of persistent thrombotic lesion and suspected CTEPH. In 2015 there were less than 300 cases described.Pulmonary angiosarcoma should be considered if: lesion occupies the entire lumen of pulmonary arteries with dilatation, contrast enhancement and infiltration of the wall in radiological examination, FDG-PET CT reveals metabolically active lesions, no pulmonary thromboembolism was documented in the anamnesis, increase in size is seen despite anticoagulation, patient presents with B symptoms.Diagnosis confirmed by biopsy, resection of tumour and removal of metastases is the therapeutic standard. Median survival remains poor. Further research is needed for improved diagnosis and treatment.

Respiratory muscle dysfunction in long-COVID patients.

PURPOSE: Symptoms often persistent for more than 4 weeks after COVID-19-now commonly referred to as 'Long COVID'. Independent of initial disease severity or pathological pulmonary functions tests, fatigue, exertional intolerance and dyspnea are among the most common COVID-19 sequelae. We hypothesized that respiratory muscle dysfunction might be prevalent in persistently symptomatic patients after COVID-19 with self-reported exercise intolerance. METHODS: In a small cross-sectional pilot study (n = 67) of mild-to-moderate (nonhospitalized) and moderate-to-critical convalescent (formerly hospitalized) patients presenting to our outpatient clinic approx. 5 months after acute infection, we measured neuroventilatory activity P0.1, inspiratory muscle strength (PImax) and total respiratory muscle strain (P0.1/PImax) in addition to standard pulmonary functions tests, capillary blood gas analysis, 6 min walking tests and functional questionnaires. RESULTS: Pathological P0.1/PImax was found in 88% of symptomatic patients. Mean PImax was reduced in hospitalized patients, but reduced PImax was also found in 65% of nonhospitalized patients. Mean P0.1 was pathologically increased in both groups. Increased P0.1 was associated with exercise-induced deoxygenation, impaired exercise tolerance, decreased activity and productivity and worse Post-COVID-19 functional status scale. Pathological changes in P0.1, PImax or P0.1/PImax were not associated with pre-existing conditions. CONCLUSIONS: Our findings point towards respiratory muscle dysfunction as a novel aspect of COVID-19 sequelae. Thus, we strongly advocate for systematic respiratory muscle testing during the diagnostic workup of persistently symptomatic, convalescent COVID-19 patients.

Mining the Plasma Proteome for Insights into the Molecular Pathology of Pulmonary Arterial Hypertension.

Rationale: Pulmonary arterial hypertension (PAH) is characterized by structural remodeling of pulmonary arteries and arterioles. Underlying biological processes are likely reflected in a perturbation of circulating proteins. Objectives: To quantify and analyze the plasma proteome of patients with PAH using inherited genetic variation to inform on underlying molecular drivers. Methods: An aptamer-based assay was used to measure plasma proteins in 357 patients with idiopathic or heritable PAH, 103 healthy volunteers, and 23 relatives of patients with PAH. In discovery and replication subgroups, the plasma proteomes of PAH and healthy individuals were compared, and the relationship to transplantation-free survival in PAH was determined. To examine causal relationships to PAH, protein quantitative trait loci (pQTL) that influenced protein levels in the patient population were used as instruments for Mendelian randomization (MR) analysis. Measurements and Main Results: From 4,152 annotated plasma proteins, levels of 208 differed between patients with PAH and healthy subjects, and 49 predicted long-term survival. MR based on cis-pQTL located in proximity to the encoding gene for proteins that were prognostic and distinguished PAH from health estimated an adverse effect for higher levels of netrin-4 (odds ratio [OR], 1.55; 95% confidence interval [CI], 1.16-2.08) and a protective effect for higher levels of thrombospondin-2 (OR, 0.83; 95% CI, 0.74-0.94) on PAH. Both proteins tracked the development of PAH in previously healthy relatives and changes in thrombospondin-2 associated with pulmonary arterial pressure at disease onset. Conclusions: Integrated analysis of the plasma proteome and genome implicates two secreted matrix-binding proteins, netrin-4 and thrombospondin-2, in the pathobiology of PAH.

[Organ-specific sequelae of COVID-19 in adults]. / Organbezogene Folgeerscheinungen von COVID­19 bei Erwachsenen.

Organ-specific sequelae after COVID-19 occur frequently and are highly diverse in their features. Sequelae and symptoms persisting for more than four weeks after COVID-19 define the condition "long COVID."Organ-specific sequelae of COVID-19 generally occur more often after severe disease. Yet, duration and intensity of organ-specific sequelae are highly variable. While pulmonary sequelae typically persist after more severe acute disease, COVID-19 sequelae may also develop weeks after infection and can affect any organ. The degree of SARS-CoV­2 specificity of COVID-19 sequelae, however, remains unclear. Thus, diagnosis and treatment of COVID-19 sequelae represent an interdisciplinary challenge. Diagnostic and therapeutic approaches are guided by type, extent, and cause of the specific sequelae as targeted therapy options for long COVID are lacking.In the present work, we review current knowledge regarding the prevalence/incidence, duration, specificity, type, and extent of organ-specific COVID-19 sequelae and summarize current diagnostic and therapeutic strategies (as of November 2021).

Using the Plasma Proteome for Risk Stratifying Patients with Pulmonary Arterial Hypertension.

Rationale: NT-proBNP (N-terminal pro-brain natriuretic peptide), a biomarker of cardiac origin, is used to risk stratify patients with pulmonary arterial hypertension (PAH). Its limitations include poor sensitivity to early vascular pathology. Other biomarkers of vascular or systemic origin may also be useful in the management of PAH. Objectives: Identify prognostic proteins in PAH that complement NT-proBNP and clinical risk scores. Methods: An aptamer-based assay (SomaScan version 4) targeting 4,152 proteins was used to measure plasma proteins in patients with idiopathic, heritable, or drug-induced PAH from the UK National Cohort of PAH (n = 357) and the French EFORT (Evaluation of Prognostic Factors and Therapeutic Targets in PAH) study (n = 79). Prognostic proteins were identified in discovery-replication analyses of UK samples. Proteins independent of 6-minute-walk distance and NT-proBNP entered least absolute shrinkage and selection operator modeling, and the best combination in a single score was evaluated against clinical targets in EFORT. Measurements and Main Results: Thirty-one proteins robustly informed prognosis independent of NT-proBNP and 6-minute-walk distance in the UK cohort. A weighted combination score of six proteins was validated at baseline (5-yr mortality; area under the curve [AUC], 0.73; 95% confidence interval [CI], 0.63-0.85) and follow-up in EFORT (AUC, 0.84; 95% CI, 0.75-0.94; P = 9.96 × 10-6). The protein score risk stratified patients independent of established clinical targets and risk equations. The addition of the six-protein model score to NT-proBNP improved prediction of 5-year outcomes from AUC 0.762 (0.702-0.821) to 0.818 (0.767-0.869) by receiver operating characteristic analysis (P = 0.00426 for difference in AUC) in the UK replication and French samples combined. Conclusions: The plasma proteome informs prognosis beyond established factors in PAH and may provide a more sensitive measure of therapeutic response.

Risk assessment in pulmonary hypertension based on routinely measured laboratory parameters.

BACKGROUND: γ-glutamyl transferase (GGT), the aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio, and the neutrophil-to-lymphocyte ratio (NLR) are prognostic biomarkers in several cardiovascular diseases, but their relevance in pulmonary hypertension (PH) is not fully understood. We aimed to assess their prognostic value in patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic PH (CTEPH). METHODS: We retrospectively analyzed 731 incident patients with idiopathic PAH or CTEPH who entered the Giessen PH registry during 1993-2019. A risk stratification score based on GGT, AST/ALT ratio, and NLR tertiles was compared with a truncated version of the European Society of Cardiology/European Respiratory Society (ESC/ERS) risk stratification scheme. Associations with survival were evaluated using Kaplan-Meier and Cox regression analyses. External validation was performed in 311 patients with various types of PAH or CTEPH from a second German center. RESULTS: GGT levels, AST/ALT, and NLR independently predicted mortality at baseline and during follow-up. The scoring system based on these biomarkers predicted mortality at baseline and during follow-up (both log-rank p < 0.001; hazard ratio [95% confidence interval], high vs low risk: baseline, 7.6 [3.9, 15.0]; follow-up, 13.3 [4.8, 37.1]). Five-year survival of low, intermediate, and high risk groups was 92%, 76%, and 51%, respectively, at baseline and 95%, 78%, and 50%, respectively, during follow-up. Our scoring system showed characteristics comparable to the ESC/ERS scheme, and predicted mortality in the validation cohort. CONCLUSION: GGT, AST/ALT, and NLR were reliable prognostic biomarkers at baseline and during follow-up, with predictive power comparable to the gold standard for risk stratification.

Transcription factors in the pathogenesis of pulmonary arterial hypertension-Current knowledge and therapeutic potential.

Pulmonary arterial hypertension (PAH) is a disease characterized by elevated pulmonary vascular resistance and pulmonary artery pressure. Mortality remains high in severe cases despite significant advances in management and pharmacotherapy. Since currently approved PAH therapies are unable to significantly reverse pathological vessel remodeling, novel disease-modifying, targeted therapeutics are needed. Pathogenetically, PAH is characterized by vessel wall cell dysfunction with consecutive remodeling of the pulmonary vasculature and the right heart. Transcription factors (TFs) regulate the process of transcribing DNA into RNA and, in the pulmonary circulation, control the response of pulmonary vascular cells to macro- and microenvironmental stimuli. Often, TFs form complex protein interaction networks with other TFs or co-factors to allow for fine-tuning of gene expression. Therefore, identification of the underlying molecular mechanisms of TF (dys-)function is essential to develop tailored modulation strategies in PAH. This current review provides a compendium-style overview of TFs and TF complexes associated with PAH pathogenesis and highlights their potential as targets for vasculoregenerative or reverse remodeling therapies.

Mendelian randomisation and experimental medicine approaches to interleukin-6 as a drug target in pulmonary arterial hypertension.

BACKGROUND: Inflammation and dysregulated immunity are important in the development of pulmonary arterial hypertension (PAH). Compelling preclinical data supports the therapeutic blockade of interleukin-6 (IL-6) signalling. METHODS: We conducted a phase 2 open-label study of intravenous tocilizumab (8 mg·kg-1) over 6 months in patients with group 1 PAH. Co-primary end-points were safety, defined by incidence and severity of adverse events, and change in pulmonary vascular resistance. Separately, a mendelian randomisation study was undertaken on 11 744 individuals with European ancestry including 2085 patients with idiopathic/heritable disease for the IL-6 receptor (IL6R) variant (rs7529229), known to associate with circulating IL-6R levels. RESULTS: We recruited 29 patients (male/female 10/19; mean±sd age 54.9±11.4 years). Of these, 19 had heritable/idiopathic PAH and 10 had connective tissue disease-associated PAH. Six were withdrawn prior to drug administration; 23 patients received at least one dose of tocilizumab. Tocilizumab was discontinued in four patients owing to serious adverse events. There were no deaths. Despite evidence of target engagement in plasma IL-6 and C-reactive protein levels, both intention-to-treat and modified intention-to-treat analyses demonstrated no change in pulmonary vascular resistance. Inflammatory markers did not predict treatment response. Mendelian randomisation did not support an effect of the lead IL6R variant on risk of PAH (OR 0.99, p=0.88). CONCLUSION: Adverse events were consistent with the known safety profile of tocilizumab. Tocilizumab did not show any consistent treatment effect.

Positioning imatinib for pulmonary arterial hypertension: A phase I/II design comprising dose finding and single-arm efficacy.

Pulmonary arterial hypertension is an unmet clinical need. Imatinib, a tyrosine kinase inhibitor, 200 to 400 mg daily reduces pulmonary artery pressure and increases functional capacity in this patient group, but is generally poorly tolerated at the higher dose. We have designed an open-label, single-arm clinical study to investigate whether there is a tolerated dose of imatinib that can be better targeted to patients who will benefit. The study consists of two parts. Part 1 seeks to identify the best tolerated dose of Imatinib in the range from 100 and up to 400 mg using a Bayesian Continuous Reassessment Method. Part 2 will measure efficacy after 24 weeks treatment with the best tolerated dose using a Simon's two-stage design. The primary efficacy endpoint is a binary variable. For patients with a baseline pulmonary vascular resistance (PVR) >1000 dynes · s · cm-5, success is defined by an absolute reduction in PVR of ≥300 dynes · s · cm-5 at 24 weeks. For patients with a baseline PVR ≤1000 dynes · s · cm-5, success is a 30% reduction in PVR at 24 weeks. PVR will also be evaluated as a continuous variable by genotype as an exploratory analysis. Evaluating the response to that dose by genotype may inform a prospective biomarker-driven study.

Non-Invasive Risk Prediction Based on Right Ventricular Function in Patients with Pulmonary Arterial Hypertension.

BACKGROUND: Right ventricular dysfunction is a major determinant of outcome in pulmonary arterial hypertension (PAH). We aimed to identify echocardiographic right heart parameters associated with adverse outcome and to develop a non-invasive, echocardiography-based risk score for PAH patients. METHODS AND RESULTS: In 254 PAH patients we analyzed functional status, laboratory results, and echocardiographic parameters. We included these parameters to estimate all-cause death or lung transplantation using Cox regression models. The analyses included a conventional model using guideline-recommended variables and an extended echocardiographic model. Based on the final model a 12-point risk score was derived, indicating the association with the primary outcome within five years. During a median follow-up time of 4.2 years 74 patients died or underwent lung transplantation. The conventional model resulted in a C-Index of 0.539, whereas the extended echocardiographic model improved the discrimination (C-index 0.639, p-value 0.017). Ultimately, the newly developed risk score included WHO functional class, 6-min walking distance, N-terminal brain natriuretic peptide concentrations, pericardial effusion, right atrial area, tricuspid annular plane systolic excursion, and fractional area change. CONCLUSION: Integrating right heart function assessed by echocardiography improves prediction of death or lung transplantation in PAH patients. Independent validation of this finding is warranted.

Genetic evidence for a causative effect of airflow obstruction on left ventricular filling: a Mendelian randomisation study.

BACKGROUND: Observational studies on the general population have suggested that airflow obstruction associates with left ventricular (LV) filling. To limit the influence of environmental risk factors/exposures, we used a Mendelian randomisation (MR) approach based on common genetic variations and tested whether a causative relation between airflow obstruction and LV filling can be detected. METHODS: We used summary statistics from large genome-wide association studies (GWAS) on the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) measured by spirometry and the LV end-diastolic volume (LVEDV) as assessed by cardiac magnetic resonance imaging. The primary MR was based on an inverse variance weighted regression. Various complementary MR methods and subsets of the instrument variables were used to assess the plausibility of the findings. RESULTS: We obtained consistent evidence in our primary MR analysis and subsequent sensitivity analyses that reducing airflow obstruction leads to increased inflow to the LV (odds ratio [OR] from inverse variance weighted regression 1.05, 95% confidence interval [CI] 1.01-1.09, P = 0.0172). Sensitivity analyses indicated a certain extent of negative horizontal pleiotropy and the estimate from biased-corrected MR-Egger was adjusted upward (OR 1.2, 95% CI 1.09-1.31, P < 0.001). Prioritisation of single genetic variants revealed rs995758, rs2070600 and rs7733410 as major contributors to the MR result. CONCLUSION: Our findings indicate a causal relationship between airflow obstruction and LV filling in the general population providing genetic context to observational associations. The results suggest that targeting (even subclinical) airflow obstruction can lead to direct cardiac improvements, demonstrated by an increase in LVEDV. Functional annotation of single genetic variants contributing most to the causal effect estimate could help to prioritise biological underpinnings.

The application of 'omics' to pulmonary arterial hypertension.

Recent genome-wide analyses of rare and common sequence variations have brought greater clarity to the genetic architecture of pulmonary arterial hypertension and implicated novel genes in disease development. Transcriptional signatures have been reported in whole lung tissue, pulmonary vascular cells and peripheral circulating cells. High-throughput platforms for plasma proteomics and metabolomics have identified novel biomarkers associated with clinical outcomes and provided molecular instruments for risk assessment. There are methodological challenges to integrating these datasets, coupled to statistical power limitations inherent to the study of a rare disease, but the expectation is that this approach will reveal novel druggable targets and biomarkers that will open the way to personalized medicine. Here, we review the current state-of-the-art and future promise of 'omics' in the field of translational medicine in pulmonary arterial hypertension. 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.

Upregulation of DDAH2 Limits Pulmonary Hypertension and Right Ventricular Hypertrophy During Chronic Hypoxia in Ddah1 Knockout Mice.

Objective: Chronic hypoxia causes pulmonary vasoconstriction leading to pulmonary hypertension and right ventricular hypertrophy. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthesis; its level increases in hypoxia (HX) concomitantly with reduced activity of dimethylarginine dimethylaminohydrolases (DDAH-1 and DDAH-2), enzymes metabolizing ADMA. Ddah1 knockout (KO) mice may therefore help to understand the pathophysiological roles of this enzyme and its substrate, ADMA, in the development of hypoxia-associated pulmonary hypertension. Methods: Ddah1 KO mice and their wild-type (WT) littermates were subjected to normoxia (NX) or for 21 days. We measured ADMA concentration in plasma and lungs, DDAH1 and DDAH2 mRNA and protein expression in the lungs, right ventricular systolic pressure (RVSP), right ventricular hypertrophy by the Fulton index, and cardiomyocyte hypertrophy by dystrophin staining of the heart. Results: Ddah1 KO mice had higher ADMA concentrations in plasma and in lung tissue than WT in NX (p < 0.05). ADMA significantly increased in WT-HX in plasma and lungs, while there were no significant differences in WT-HX vs. KO-HX. This finding was paralleled by a 38 ± 13% reduction in Ddah1 but not Ddah2 mRNA expression, and reduced DDAH1 protein expression but stable DDAH2 protein levels in WT mice. Ddah1 KO mice showed significant elevation of DDAH2 protein but not mRNA levels, which further increased in HX. HX led to increased RVSP and right ventricular hypertrophy in both, WT and KO mice, with no significant differences between both genotypes. Conclusions: Chronic hypoxia causes an elevation of ADMA, which may impair NO production and lead to endothelial dysfunction and vasoconstriction. Downregulation of DDAH1 expression and activity may be involved in this; however, knockout of the Ddah1 gene does not modify the hypoxia-induced pathophysiological changes of pulmonary blood pressure and right ventricular hypertrophy, possibly due to compensatory upregulation of DDAH2 protein.

Idiopathic pulmonary arterial hypertension phenotypes determined by cluster analysis from the COMPERA registry.

The term idiopathic pulmonary arterial hypertension (IPAH) is used to categorize patients with pre-capillary pulmonary hypertension of unknown origin. There is considerable variability in the clinical presentation of these patients. Using data from the Comparative, Prospective Registry of Newly Initiated Therapies for Pulmonary Hypertension, we performed a cluster analysis of 841 patients with IPAH based on age, sex, diffusion capacity of the lung for carbon monoxide (DLCO; <45% vs ≥45% predicted), smoking status, and presence of comorbidities (obesity, hypertension, coronary heart disease, and diabetes mellitus). A hierarchical agglomerative clustering algorithm was performed using Ward's minimum variance method. The clusters were analyzed in terms of baseline characteristics; survival; and response to pulmonary arterial hypertension (PAH) therapy, expressed as changes from baseline to follow-up in functional class, 6-minute walking distance, cardiac biomarkers, and risk. Three clusters were identified: Cluster 1 (n = 106; 12.6%): median age 45 years, 76% females, no comorbidities, mostly never smokers, DLCO ≥45%; Cluster 2 (n = 301; 35.8%): median age 75 years, 98% females, frequent comorbidities, no smoking history, DLCO mostly ≥45%; and Cluster 3 (n = 434; 51.6%): median age 72 years, 72% males, frequent comorbidities, history of smoking, and low DLCO. Patients in Cluster 1 had a better response to PAH treatment than patients in the 2 other clusters. Survival over 5 years was 84.6% in Cluster 1, 59.2% in Cluster 2, and 42.2% in Cluster 3 (unadjusted p < 0.001 for comparison between all groups). The population of patients diagnosed with IPAH is heterogenous. This cluster analysis identified distinct phenotypes, which differed in clinical presentation, response to therapy, and survival.