Genetic counselling and testing in pulmonary arterial hypertension: a consensus statement on behalf of the International Consortium for Genetic Studies in PAH

The prevalence of pathogenic variants in the BMPR2 gene in patients with the idiopathic pulmonary arterial hypertension in the Russian population: sequencing data and meta-analysis

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is a rare and severe form of pulmonary hypertension, with a genetic basis most commonly associated with mutations in the BMPR2 gene. However, no genetic testing has been reported for IPAH patients in the Russian population, nor have systematic studies been conducted to assess the frequency of pathogenic variants in this group.

METHODS

The study cohort included 105 IPAH patients, consisting of 23 males and 82 females, who were managed at the PH care center in Moscow, Russia, from 2014 to 2024. Genetic testing was performed using whole-genome sequencing. Variant identification and annotation were conducted using GATK, DeepVariant, VEP, sv-callers and AnnotSV. A meta-analysis, performed with MOOSE, included 24 studies involving 3124 IPAH patients and 470 P/LP variants. Pathogenicity reassessment was carried out using InterVar, which incorporates ACMG criteria.

RESULTS

Analysis of 105 adult IPAH patients in Russia revealed 11 patients (10.48%) as carriers of pathogenic or likely pathogenetic (P/LP) BMPR2 variants. As the result of reassessment, the number of P/LP BMPR2 variants raised from 394 (59%) to 445 (67%) with 80 pathogenic variants became of uncertain significance, and 152 unclassified variants became P/LP. The meta-analysis of these reevaluated pathogenic variants showed that while the frequency of P/LP variants in our cohort (10.48%) is lower than the overall average of 17.75% from the meta-analysis, the difference is not statistically significant (p = 0.062). Additionally, we report three P/LP BMPR2 variants, not reported in literature, with one being structural, and four P/LP variants in TBX4, ATP13A3 and AQP1 genes from 27 IPAH genes in 3 patients.

CONCLUSIONS

For the first time, we present the results of genetic testing in IPAH patients from the Russian population. Despite the considerable heterogeneity in the world-wide data, the prevalence of pathogenic BMPR2 mutations in IPAH patients from the Russian population does not significantly differ from the overall average in the meta-analysis. It is crucial to periodically reassess the pathogenicity of published variants, as half of the pathogenic BMPR2 IPAH variants were reclassified as LP or of uncertain significance.

Pathogenic SMAD6 variants in patients with idiopathic and complex congenital heart disease associated pulmonary arterial hypertension

In patients with complex congenital heart disease (CHD) pathogenic SMAD6 variants have been described previously. The aim of this study was to analyze if pathogenic SMAD6 variants also occur in patients with CHD associated with pulmonary arterial hypertension (CHD-APAH) or idiopathic PAH. A PAH gene panel with up to 64 genes including SMAD6 was used to sequence 311 patients with idiopathic PAH (IPAH) and 32 with CHD-APAH. In 4 of 32 (12.5%) CHD-APAH and in 2 out of 311 (0.64%) IPAH patients we identified likely pathogenic or rare SMAD6 missense variants. All CHD-APAH patients with a rare SMAD6 variant had complex CHD. One patient had bi-allelic SMAD6 variants, combined pulmonary valve defect and supravalvular aortic stenosis, craniosynostosis and radioulnar synostosis. This is the first description of potentially disease-causing SMAD6 variants in patients with IPAH and complex CHD-APAH. Further studies are needed to assess pathogenesis and prevalence of pathogenic SMAD6 variants in PAH.

Navigating family dynamics and ethical considerations in genetic diagnosis of pulmonary arterial hypertension: insights from in-depth semi-structured interviews

Background

Genetic diagnosis and precision medicine are rapidly advancing, driven by innovations in next-generation sequencing and omic methods. The UK's collaboration between national research initiatives and the National Health Service facilitates translation of research into clinical practice. This rapid transition impacts family dynamics and family planning, and raises ethical concerns, compounded by limited public and practitioner awareness of the long-term consequences of genetic diagnosis. Our objective is to explore the impact of genetic diagnosis on family dynamics and the ethical considerations of genetic testing at different life stages in patients with pulmonary arterial hypertension (PAH) and their at-risk relatives.

Methods

Stakeholders from the National Institute for Health Research BioResource Rare Diseases Study and the National Cohort Study of Idiopathic and Heritable Pulmonary Arterial Hypertension were recruited using purposive sampling. 53 interviews and focus groups with 63 participants were recorded, transcribed and thematically analysed using MAXQDA data analysis software.

Results

The study revealed three main themes: the impact of diagnosis on family dynamics, considerations for family planning, and genetic testing of relatives. Two attitudes toward testing offspring emerged: proactive advocates and gatekeepers. The gatekeeper stance was driven by three key factors: shielding children from genetic risk awareness, feelings of guilt or a desire to avoid blame for disease transmission, and limited family connections. Each theme highlighted various moral and ethical dilemmas faced by individuals.

Conclusions

A PAH diagnosis reshapes family roles and responsibilities. Genetic risk awareness strengthens bonds but also introduces challenges such as disclosing information and deciding on testing for at-risk relatives. Our research highlights the need for comprehensive genetic counselling and support systems to enhance patient care and familial wellbeing.

Implementing pulmonary arterial hypertension screening among TBX4 mutation carriers: a timely endeavour

Systematic genetic counselling for TBX4 carriers and their relatives enables screening for small patella syndrome and early diagnosis of pulmonary arterial hypertension https://bit.ly/4eKaPzY.

Pulmonary hypertension in patients carrying FLNA loss-of-function variants

BACKGROUND

Pulmonary hypertension (PH) is an unusual complication of X-linked disease caused by loss-of-function (LOF) variants in the filamin A (FLNA) gene. Patients with FLNA LOF may also present dysmorphic facial features, aortic dilation, thrombocytopenia and periventricular nodular heterotopia (PVNH).

METHODS

We reported the clinical, functional, haemodynamic and radiological characteristics of patients with FLNA LOF variants and PH from the French PH Network.

RESULTS

Nine patients were identified with a female:male ratio of 8:1. PH was diagnosed at a median (range) age of 36 (0-69) years. Associated conditions included epilepsy (n=5), PVNH (n=7), valvular heart disease (n=8), congenital heart diseases (n=4), thrombocytopenia (n=4) and hyperlaxity (n=4). Right heart catheterisation confirmed moderate-to-severe pre-capillary PH with a median (range) mean pulmonary arterial pressure of 33 (22-49) mmHg and pulmonary vascular resistance of 4.7 (2.4-8.0) WU. The median (range) diffusing capacity of the lung for carbon monoxide corrected for haemoglobin was markedly decreased (48% (22-64%) of predicted values) and five patients had obstructive ventilatory disorder. High-resolution computed tomography showed heterogeneous parenchyma (n=8), emphysema (n=3), presence of a peripheral hyperclear band (n=3) and aortic ectasia (n=4). Pathological assessment available in one patient revealed significant remodelling of small pulmonary arteries, interstitial oedema and irregular alveoli shapes. During follow-up, three patients died, including two from right heart failure. No patient died from aortic rupture.

CONCLUSIONS

Pre-capillary PH, likely due to multiple mechanisms, may complicate the course of patients with FLNA LOF variants and may be the presenting symptom leading to diagnosis. The combination of PH with parenchymal involvement and extrapulmonary symptoms (epilepsy, congenital heart diseases, valvular and aortic involvement, and thrombocytopenia) should prompt genetic screening for FLNA.

SMAD5 as a novel gene for familial pulmonary arterial hypertension

Genetic diagnostic testing of 325 pulmonary arterial hypertension (PAH) patients using a PAH specific gene panel including 18 known PAH genes revealed mutations in 23%. Further PAH candidate genes were sequenced in the remaining patients exposing two SMAD5 variants, which were clinically and functionally characterized. We first recorded familial cosegregation and clinical parameters. Functional tests were performed following transient over-expression of the two SMAD5 variants in pulmonary artery smooth muscle cells (PASMCs). Expression of these variants was confirmed by quantitative PCR, Sanger sequencing, and Western blotting. Cell viability was evaluated using cell counting kit 8, cell proliferation by bromodeoxyuridine (BrdU), and apoptosis by annexin V assay. Both SMAD5 missense variants were absent in healthy controls and predicted to be pathogenic. The variant c.1175T>C p.(Leu392Pro) was identified in a heritable PAH patient and her healthy son. The mother had died of suspected PAH at age 42. The expression of this variant in PASMCs led to significantly higher cell viability due to higher proliferation in comparison with SMAD5 wild-type cells. The second variant c.277T>A p.(Trp93Arg) was identified in a patient with congenital heart disease associated PAH with a surgically repaired ventricular septal defect. Its expression led to significantly lower cell viability due to increased apoptosis in comparison with wild-type SMAD5 cells. Taking into account familial aggregation, clinical findings, and functional evidence, both variants could be classified as likely pathogenic. This is the first description of SMAD5 as a potential novel PAH gene for genetic diagnostic testing.

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

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

Hemodynamic and Genetic Associations with the Risk of Idiopathic Pulmonary Arterial Hypertension Development in an Ethnic Cohort of Kazakhs

INTRODUCTION

Idiopathic pulmonary arterial hypertension (IPAH) is a progressive and fatal disease. The aim of this study was to evaluate the association of polymorphism of the type 2 bone morphogenetic protein receptor gene (BMPR2) with the risk of IPAH development in an ethnic group of Kazakhs. We also describe the clinical and hemodynamic characteristics and outcomes of patients with and without carriers of BMPR2 gene mutations in IPAH. No available research highlights this problem in an ethnic group of Kazakhs.

MATERIALS AND METHODS

A total of 53 patients of only Kazakh nationality with IPAH participated in the study. Clinical, functional, and hemodynamic characteristics, as well as the outcome of the disease, were compared among carriers and non-carriers of the BMPR2 mutation.

RESULTS

When receiving IPAH diagnosis, the average age of patients was 40.0 (32.0-48.0) years. Women predominated among the patients (86.8%). Of these, 17 (32.0%) were carriers of the gene mutation, and 36 (68.0%) did not have this mutation. The results of our research demonstrate that the Rs17199249 variant in BMPR2 contributed to increased susceptibility to IPAH. The T allele was associated with an increased risk of IPAH, with T = 75 (70.75%), G = 31 (29.24%), MAF-0.2925, x2-0.001, and HWE p-0.975. Carriers of the BMPR2 mutation were predominantly women (80.0%), and they had higher pulmonary vascular resistance (8.7-14.9 vs. 5.9-12.6 WU; p = 0.038), a low cardiac index (1.9-2.6 vs. 2.3-3.1 L/min per m2; p = 0.027), and a shorter time to death (p = 0.022).

CONCLUSIONS

This is the first study of the genetic causes of IPAH that demonstrates the genetic polymorphism of BMPR2 is associated with an increased risk of IPAH developing with worse hemodynamic parameters and clinical outcomes.

Adaptation of ACMG/AMP guidelines for clinical classification of BMPR2 variants in Pulmonary Arterial Hypertension resolves variants of unclear pathogenicity in ClinVar

PURPOSE

Pulmonary arterial hypertension (PAH) is a rare disease that can be caused by pathogenic variants, most frequently in the bone morphogenetic protein receptor type 2 ( BMPR2 ) gene. We formed a ClinGen variant curation expert panel to devise guidelines for the clinical interpretation of BMPR2 variants identified in PAH patients.

METHODS

The general ACMG/AMP variant classification criteria were refined for PAH and adapted to BMPR2 following ClinGen procedures. Subsequently, these specifications were tested independently by three members of the curation expert panel on 28 representative BMPR2 variants selected from ClinVar, and then presented and discussed in the plenum.

RESULTS

Application of the final BMPR2 variant specifications resolved 6 of 9 variants (66%) where multiple ClinVar classifications included a Variant of Uncertain Significance, with all six being reclassified as Benign or Likely Benign. Four splice site variants underwent clinically consequential reclassifications based on the presence or absence of supporting mRNA splicing data.

CONCLUSION

The variant specifications provide an international framework and a useful tool for BMPR2 variant classification and can be applied to increase confidence and consistency in BMPR2 interpretation for diagnostic laboratories, clinical providers, and patients.

Case report: A finding of PVOD and PAH in first degree relatives suggests shared heritable risk and overlapping features of both pulmonary vascular diseases

Pulmonary veno-occlusive disease (PVOD) is a rare form of pulmonary vascular disease that is difficult to distinguish clinically from pulmonary arterial hypertension (PAH). Multiple genes have been implicated in disease pathogenesis in PAH and PVOD and the diseases are thought to be genetically distinct. In this report we present a case of first-degree relatives with pathological evidence of PVOD and PAH. The index patient was diagnosed with PAH at age 42, was treated with escalating pulmonary vasodilator therapy, but eventually succumbed to her disease. On autopsy, her pathology was consistent with PAH. Her son was diagnosed with PAH at age 16, did well on pulmonary vasodilator therapy for over 10 years, but ultimately developed refractory right ventricular failure and received a heart and lung transplantation. Pathology of his explanted lung was consistent with PVOD, and genetic testing was negative for recognized variants that cause PAH or PVOD.

Novel insights into the GCN2 pathway and its targeting. Therapeutic value in cancer and lessons from lung fibrosis development

Defining the mechanisms that allow cells to adapt to environmental stress is critical for understanding the progression of chronic diseases and identifying relevant drug targets. Among these, activation of the pathway controlled by the eIF2-alpha kinase GCN2 is critical for translational and metabolic reprogramming of the cell in response to various metabolic, proteotoxic, and ribosomal stressors. However, its role has frequently been investigated through the lens of a stress pathway signaling via the eIF2α-activating transcription factor 4 (ATF4) downstream axis, while recent advances in the field have revealed that the GCN2 pathway is more complex than previously thought. Indeed, this kinase can be activated through a variety of mechanisms, phosphorylate substrates other than eIF2α, and regulate cell proliferation in a steady state. This review presents recent findings regarding the fundamental mechanisms underlying GCN2 signaling and function, as well as the development of drugs that modulate its activity. Furthermore, by comparing the literature on GCN2's antagonistic roles in two challenging pathologies, cancer and pulmonary diseases, the benefits, and drawbacks of GCN2 targeting, particularly inhibition, are discussed.

Pulmonary hypertension in adults with congenital heart defects (ACHDs)-in light of the 2022 ESC PAH guidelines-part I: definition, epidemiology, classification, diagnostics, genetics, risk stratification and follow-up, gender aspects

The number of adults with congenital heart defects (ACHDs) is steadily increasing and is about 360,000 in Germany. Congenital heart defect (CHD) is often associated with pulmonary hypertension (PH), which sometimes develops early in untreated CHD. Despite timely treatment of CHD, PH not infrequently persists, redevelops in older age, and is associated with significant morbidity and lethality. The revised European Society of Cardiology (ESC)/European Respiratory Society (ERS) 2022 guidelines for the diagnosis and treatment of PH represent a significant contribution to the optimized care of those affected. However, the topic of "adults with congenital heart defects" is treated only relatively superficially in this context. In the present article, part I, therefore, this topic is commented on in detail from the perspective of congenital cardiology with a special focus on definition, epidemiology, classification, diagnostics, genetics, risk stratification and follow-up and gender aspects of PH in ACHDs. This paper consists of two parts. Part II will provide comments on the topics of supportive therapy, special situations like pregnancy, contraception, and non-cardiac surgery, targeted pharmacotherapy, organ transplantation, special management like shunt lesion, left ventricular disease, and univentricular hearts, interventions, intensive care, ACHDs follow-up and future perspective on PH in ACHDs. By examining these aspects in detail, this article aims to fill the gaps in the existing guidelines and provide a more thorough understanding from the perspective of congenital cardiology.

Deep phenotyping of unaffected carriers of pathogenic BMPR2 variants screened for pulmonary arterial hypertension

INTRODUCTION

Pathogenic variants in the gene encoding for BMPR2 are a major genetic risk factor for heritable pulmonary arterial hypertension. Owing to incomplete penetrance, deep phenotyping of unaffected carriers of a pathogenic BMPR2 variant through multimodality screening may aid in early diagnosis and identify susceptibility traits for future development of pulmonary arterial hypertension.

METHODS

28 unaffected carriers (44±16 years, 57% female) and 21 healthy controls (44±18 years, 48% female) underwent annual screening, including cardiac magnetic resonance imaging, transthoracic echocardiography, cardiopulmonary exercise testing and right heart catheterisation. Right ventricular pressure-volume loops were constructed to assess load-independent contractility and compared with a healthy control group. A transgenic Bmpr2Δ71Ex1/+ rat model was employed to validate findings from humans.

RESULTS

Unaffected carriers had lower indexed right ventricular end-diastolic (79.5±17.6 mL·m-2 versus 62.7±15.3 mL·m-2; p=0.001), end-systolic (34.2±10.5 mL·m-2 versus 27.1±8.3 mL·m-2; p=0.014) and left ventricular end-diastolic (68.9±14.1 mL·m-2 versus 58.5±10.7 mL·m-2; p=0.007) volumes than control subjects. Bmpr2Δ71Ex1/+ rats were also observed to have smaller cardiac volumes than wild-type rats. Pressure-volume loop analysis showed that unaffected carriers had significantly higher afterload (arterial elastance 0.15±0.06 versus 0.27±0.08 mmHg·mL-1; p<0.001) and end-systolic elastance (0.28±0.07 versus 0.35±0.10 mmHg·mL-1; p=0.047) in addition to lower right ventricular pulmonary artery coupling (end-systolic elastance/arterial elastance 2.24±1.03 versus 1.36±0.37; p=0.006). During the 4-year follow-up period, two unaffected carriers developed pulmonary arterial hypertension, with normal N-terminal pro-brain natriuretic peptide and transthoracic echocardiography indices at diagnosis.

CONCLUSION

Unaffected BMPR2 mutation carriers have an altered cardiac phenotype mimicked in Bmpr2Δ71Ex1/+ transgenic rats. Future efforts to establish an effective screening protocol for individuals at risk for developing pulmonary arterial hypertension warrant longer follow-up periods.

Definition, classification and diagnosis of pulmonary hypertension

Pulmonary hypertension (PH) is a haemodynamic condition characterised by elevation of mean pulmonary arterial pressure (mPAP) >20 mmHg, assessed by right heart catheterisation. Pulmonary arterial wedge pressure (PAWP) and pulmonary vascular resistance (PVR) distinguish pre-capillary PH (PAWP ≤15 mmHg, PVR >2 Wood Units (WU)), isolated post-capillary PH (PAWP >15 mmHg, PVR ≤2 WU) and combined post- and pre-capillary PH (PAWP >15 mmHg, PVR >2 WU). Exercise PH is a haemodynamic condition describing a normal mPAP at rest with an abnormal increase of mPAP during exercise, defined as a mPAP/cardiac output slope >3 mmHg/L/min between rest and exercise. The core structure of the clinical classification of PH has been retained, including the five major groups. However, some changes are presented herewith, such as the re-introduction of "long-term responders to calcium channel blockers" as a subgroup of idiopathic pulmonary arterial hypertension, the addition of subgroups in group 2 PH and the differentiation of group 3 PH subgroups based on pulmonary diseases instead of functional abnormalities. Mitomycin-C and carfilzomib have been added to the list of drugs with "definite association" with PAH. For diagnosis of PH, we propose a stepwise approach with the main aim of discerning those patients who need to be referred to a PH centre and who should undergo invasive haemodynamic assessment. In case of high probability of severe pulmonary vascular disease, especially if there are signs of right heart failure, a fast-track referral to a PH centre is recommended at any point during the clinical workup.

Exploring Diagnostic and Therapeutic Odyssey in Pulmonary Arterial Hypertension: Insights from In-Depth Semi-Structured Interviews

INTRODUCTION

Establishing a diagnosis is paramount in medical practice as it shapes patients' experiences and guides treatment. Patients grappling with rare diseases face a triple challenge: prolonged diagnostic journeys, limited responses to existing therapies, and the absence of effective monitoring tools. Genetic diagnosis often provides crucial diagnostic and prognostic information, opening up possibilities for genotype-targeted treatments and facilitating counselling and relative testing. The NIHR BioResource - Rare Diseases (NBR) Study and the Cohort Study in Idiopathic and Hereditary Pulmonary Arterial Hypertension (PAH Cohort study) aimed to enhance diagnosis and treatment for PAH, successfully identifying the genetic cause in 25% of idiopathic cases. However, the diagnostic and therapeutic odyssey in patients with PAH remains largely unexplored.

METHODS

Stakeholders from the NBR and PAH Cohort studies were recruited using purposive sampling. In-depth interviews and focus groups were recorded, transcribed, anonymised, and analysed thematically using MAXQDA software.

RESULTS

The study involved 53 interviews and focus groups with 63 participants, revealing key themes across five stages of the diagnostic odyssey: initial health concerns and interactions with general practitioners, experiences of misdiagnosis, relief upon receiving the correct diagnosis, and mixed emotions regarding genetic results and the challenges of living with the disease. Following the diagnosis, participants embarked on a therapeutic journey, facing various challenges, including the disease's impact on professional and social lives, the learning curve associated with understanding the disease, shifts in communication dynamics with healthcare providers, therapeutic hurdles, and insurance-related issues. Building on these insights, we identified areas of unmet needs, such as improved collaboration with primary care providers and local hospitals, the provision of psychological support and counselling, and the necessity for ongoing patient education in the ever-evolving realms of research and therapy.

CONCLUSIONS

The study highlights the significant challenges encountered throughout the diagnostic and therapeutic journey in PAH. To enhance patient outcomes, it is crucial to raise awareness of the disease, establish clear diagnostic pathways, and seamlessly integrate genetic diagnostics into clinical practice. Streamlining the diagnostic process can be achieved by utilising existing clinical infrastructure to support research and fostering better communication within the NHS. Moreover, there is an urgent need for more effective therapies alongside less burdensome drug delivery methods.

Genetic background of pulmonary (vascular) diseases - how much is written in the codes?

PURPOSE OF REVIEW

To provide a comprehensive overview of the underlying genetic defects of pulmonary (vascular) diseases and novel treatment avenues.

RECENT FINDINGS

Pulmonary arterial hypertension (PAH) is the prime example of a pulmonary vascular disease, which can be caused by genetic mutations in some patients. Germline mutations in the BMPR2 gene and further genes lead to vessel remodelling, increase of pulmonary vascular resistance and onset of heritable PAH. The PAH genes with the highest evidence and strategies for genetic testing and counselling have been assessed and evaluated in 2023 by international expert consortia. Moreover, first treatment options have just arisen targeting the molecular basis of PAH.

SUMMARY

Apart from PAH, this review touches on the underlying genetic causes of further lung diseases including alpha 1 antitrypsin deficiency, cystic fibrosis, familial pulmonary fibrosis and lymphangioleiomyomatosis. We point out the main disease genes, the underlying pathomechanisms and novel therapies trying not only to relieve symptoms but to treat the molecular causes of the diseases.

Bone morphogenetic protein signalling in pulmonary arterial hypertension: revisiting the BMPRII connection

Pulmonary arterial hypertension (PAH) is a rare and life-threatening vascular disorder, characterised by abnormal remodelling of the pulmonary vessels and elevated pulmonary artery pressure, leading to right ventricular hypertrophy and right-sided heart failure. The importance of bone morphogenetic protein (BMP) signalling in the pathogenesis of PAH is demonstrated by human genetic studies. Many PAH risk genes are involved in the BMP signalling pathway and are highly expressed or preferentially act on vascular endothelial cells. Endothelial dysfunction is recognised as an initial trigger for PAH, and endothelial BMP signalling plays a crucial role in the maintenance of endothelial integrity. BMPR2 is the most prevalent PAH gene, found in over 80% of heritable cases. As BMPRII protein is the major type II receptor for a large family of BMP ligands and expressed ubiquitously in many tissues, dysregulated BMP signalling in other cells may also contribute to PAH pathobiology. Sotatercept, which contains the extracellular domain of another transforming growth factor-β family type II receptor ActRIIA fused to immunoglobin Fc domain, was recently approved by the FDA as a treatment for PAH. Neither its target cells nor its mechanism of action is fully understood. This review will revisit BMPRII function and its extracellular regulation, summarise how dysregulated BMP signalling in endothelial cells and smooth muscle cells may contribute to PAH pathogenesis, and discuss how novel therapeutics targeting the extracellular regulation of BMP signalling, such as BMP9 and Sotatercept, can be related to restoring BMPRII function.

[Heritable pulmonary arterial hypertension]

Heritable pulmonary arterial hypertension (PAH) can be triggered by at least 18 genes. The most frequently altered gene is the bone morphogenetic protein receptor 2 (BMPR2). Further genes from the same pathway are also well known PAH-causing genes. Genetic testing can aid to confirm differential diagnoses such as a pulmonary veno-occlusive disease. It also enables the testing of healthy family members. In addition to the PAH patient population particularly served by genetic testing, this article touches on the mode of inheritance and provides insights into the first treatments soon on the market that rebalance the BMPR2 signaling pathway.

Pulmonary vascular phenotype identified in patients with GDF2 (BMP9) or BMP10 variants: an international multicentre study

BACKGROUND

Bone morphogenetic proteins 9 and 10 (BMP9 and BMP10), encoded by GDF2 and BMP10, respectively, play a pivotal role in pulmonary vascular regulation. GDF2 variants have been reported in pulmonary arterial hypertension (PAH) and hereditary haemorrhagic telangiectasia (HHT). However, the phenotype of GDF2 and BMP10 carriers remains largely unexplored.

METHODS

We report the characteristics and outcomes of PAH patients in GDF2 and BMP10 carriers from the French and Dutch pulmonary hypertension registries. A literature review explored the phenotypic spectrum of these patients.

RESULTS

26 PAH patients were identified: 20 harbouring heterozygous GDF2 variants, one homozygous GDF2 variant, four heterozygous BMP10 variants, and one with both GDF2 and BMP10 variants. The prevalence of GDF2 and BMP10 variants was 1.3% and 0.4%, respectively. Median age at PAH diagnosis was 30 years, with a female/male ratio of 1.9. Congenital heart disease (CHD) was present in 15.4% of the patients. At diagnosis, most of the patients (61.5%) were in New York Heart Association Functional Class III or IV with severe haemodynamic compromise (median (range) pulmonary vascular resistance 9.0 (3.3-40.6) WU). Haemoptysis was reported in four patients; none met the HHT criteria. Two patients carrying BMP10 variants underwent lung transplantation, revealing typical PAH histopathology. The literature analysis showed that 7.6% of GDF2 carriers developed isolated HHT, and identified cardiomyopathy and developmental disorders in BMP10 carriers.

CONCLUSIONS

GDF2 and BMP10 pathogenic variants are rare among PAH patients, and occasionally associated with CHD. HHT cases among GDF2 carriers are limited according to the literature. BMP10 full phenotypic ramifications warrant further investigation.

A surgical mouse model of neonatal right ventricular outflow tract obstruction by pulmonary artery banding

BACKGROUD

Diseased animal models play an extremely important role in preclinical research. Lacking the corresponding animal models, many basic research studies cannot be carried out, and the conclusions obtained are incomplete or even incorrect. Right ventricular (RV) outflow tract (RVOT) obstruction leads to RV pressure overload (PO) and reduced pulmonary blood flow (RPF), which are 2 of the most important pathophysiological characteristics in pediatric cardiovascular diseases and seriously affect the survival rate and long-term quality of life of many children. Due to the lack of a neonatal mouse model for RVOT obstruction, it is largely unknown how RV PO and RPF regulate postnatal RV and pulmonary development. The aim of this study was to construct a neonatal RVOT obstruction mouse model.

METHODS AND RESULTS

Here, we first introduced a neonatal mouse model of RVOT obstruction by pulmonary artery banding (PAB) on postnatal day 1. PAB induced neonatal RVOT obstruction, RV PO, and RPF. Neonatal RV PO induced cardiomyocyte proliferation, and neonatal RPF induced pulmonary dysplasia, the 2 features that are not observed in adult RVOT obstruction. As a result, PAB neonates exhibited overall developmental dysplasia, a sign similar to that of children with RVOT obstruction.

CONCLUSIONS

Because many pediatric cardiovascular diseases are associated with RV PO and RPF, the introduction of a neonatal mouse model of RVOT obstruction may greatly enhance our understanding of these diseases and eventually improve or save the lives of many children.

Extrapulmonary manifestations of pulmonary arterial hypertension

INTRODUCTION

Extrapulmonary manifestations of pulmonary arterial hypertension (PAH) may play a critical pathobiological role and a deeper understanding will advance insight into mechanisms and novel therapeutic targets. This manuscript reviews our understanding of extrapulmonary manifestations of PAH.

AREAS COVERED

A group of experts was assembled and a complimentary PubMed search performed (October 2023 - March 2024). Inflammation is observed throughout the central nervous system and attempts at manipulation are an encouraging step toward novel therapeutics. Retinal vascular imaging holds promise as a noninvasive method of detecting early disease and monitoring treatment responses. PAH patients have gut flora alterations and dysbiosis likely plays a role in systemic inflammation. Despite inconsistent observations, the roles of obesity, insulin resistance and dysregulated metabolism may be illuminated by deep phenotyping of body composition. Skeletal muscle dysfunction is perpetuated by metabolic dysfunction, inflammation, and hypoperfusion, but exercise training shows benefit. Renal, hepatic, and bone marrow abnormalities are observed in PAH and may represent both end-organ damage and disease modifiers.

EXPERT OPINION

Insights into systemic manifestations of PAH will illuminate disease mechanisms and novel therapeutic targets. Additional study is needed to understand whether extrapulmonary manifestations are a cause or effect of PAH and how manipulation may affect outcomes.

Pulmonary hypertension

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

[Diagnostic Algorithm and Screening of Pulmonary Hypertension]

The new guidelines for the diagnosis and treatment of pulmonary hypertension include a new diagnostic algorithm and provide specific recommendations for the required diagnostic procedures, including screening methods. These recommendations are commented on by national experts under the auspices of the DACH. These comments provide additional decision support and background information, serving as a further guide for the complex diagnosis of pulmonary hypertension.

[Genetic diagnostics and molecular approaches in pulmonary arterial hypertension]

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.

Defining the clinical validity of genes reported to cause pulmonary arterial hypertension

PURPOSE

Pulmonary arterial hypertension (PAH) is a rare, progressive vasculopathy with significant cardiopulmonary morbidity and mortality. Genetic testing is currently recommended for adults diagnosed with heritable, idiopathic, anorexigen-, hereditary hemorrhagic telangiectasia-, and congenital heart disease-associated PAH, PAH with overt features of venous/capillary involvement, and all children diagnosed with PAH. Variants in at least 27 genes have putative evidence for PAH causality. Rigorous assessment of the evidence is needed to inform genetic testing.

METHODS

An international panel of experts in PAH applied a semi-quantitative scoring system developed by the NIH Clinical Genome Resource to classify the relative strength of evidence supporting PAH gene-disease relationships based on genetic and experimental evidence.

RESULTS

Twelve genes (BMPR2, ACVRL1, ATP13A3, CAV1, EIF2AK4, ENG, GDF2, KCNK3, KDR, SMAD9, SOX17, and TBX4) were classified as having definitive evidence and 3 genes (ABCC8, GGCX, and TET2) with moderate evidence. Six genes (AQP1, BMP10, FBLN2, KLF2, KLK1, and PDGFD) were classified as having limited evidence for causal effects of variants. TOPBP1 was classified as having no known PAH relationship. Five genes (BMPR1A, BMPR1B, NOTCH3, SMAD1, and SMAD4) were disputed because of a paucity of genetic evidence over time.

CONCLUSION

We recommend that genetic testing includes all genes with definitive evidence and that caution be taken in the interpretation of variants identified in genes with moderate or limited evidence. Genes with no known evidence for PAH or disputed genes should not be included in genetic testing.

Advances in the research of sulfur dioxide and pulmonary hypertension

Pulmonary hypertension (PH) is a fatal disease caused by progressive pulmonary vascular remodeling (PVR). Currently, the mechanisms underlying the occurrence and progression of PVR remain unclear, and effective therapeutic approaches to reverse PVR and PH are lacking. Since the beginning of the 21st century, the endogenous sulfur dioxide (SO2)/aspartate transaminase system has emerged as a novel research focus in the fields of PH and PVR. As a gaseous signaling molecule, SO2 metabolism is tightly regulated in the pulmonary vasculature and is associated with the development of PH as it is involved in the regulation of pathological and physiological activities, such as pulmonary vascular cellular inflammation, proliferation and collagen metabolism, to exert a protective effect against PH. In this review, we present an overview of the studies conducted to date that have provided a theoretical basis for the development of SO2-related drug to inhibit or reverse PVR and effectively treat PH-related diseases.

The cascade screening in heritable forms of pulmonary arterial hypertension

Heritable pulmonary artery hypertension (HPAH) is an increasingly recognized type of pulmonary arterial hypertension, in both pediatric and adult population. Intrinsic to hereditary disease, screening for genetic mutations within families is an important component of diagnosis and understanding burden of disease. Recently, consensus guidelines are published for genetic screening in PAH. These guidelines include recommendations for screening at diagnosis, noting individuals with presumed PAH due to familial, or idiopathic etiologies. Cascade genetic testing is specifically recommended as a testing paradigm to screen relatives for detection of mutation carriers, who may be asymptomatic. Without targeted genetic testing, familial mutation carriers may only come to attention when pulmonary vascular disease burden is high enough to cause symptoms, suggesting more advanced disease. Here, we present our collective experience with HPAH in five distinct families, specifically to report on the clinical courses of patients who were diagnosed with genetic mutation at diagnosis versus those who were offered genetic screening. In three families, asymptomatic mutation carriers were identified and monitored for clinical worsening. In two families, screening was not done and affected family members presented with advanced disease.