Publications
245 results found
Toshner M, Church C, Harbaum L, et al., 2021, Mendelian randomisation and experimental medicine approaches to IL-6 as a drug target in PAH, European Respiratory Journal, Vol: 59, Pages: 1-11, ISSN: 0903-1936
Inflammation and dysregulated immunity are important in the development of pulmonary arterial hypertension. Compelling preclinical data supports the therapeutic blockade of interleukin-6 signalling.We conducted an open-label phase-II study of intravenous tocilizumab (8 mg·kg-1) over 6 months in group 1 pulmonary arterial hypertension. Co-primary endpoints 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 IL6R variant (rs7529229), known to associate with circulating IL6R levels.Twenty-nine patients (M/F 10/19; mean age 54.9[SD11.4]) were recruited. Nineteen had heritable/idiopathic and ten connective tissue disease associated pulmonary arterial hypertension. Six were withdrawn prior to drug administration. Twenty-three patients received at least one dose of tocilizumab. Tocilizumab was discontinued in 4 patients due to serious adverse events. There were no deaths. Despite evidence of target engagement in plasma interleukin-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 pulmonary arterial hypertension (OR 0.99, p=0.88).Adverse events were consistent with the known safety profile of tocilizumab. Tocilizumab did not show any consistent treatment effect.
Errington N, Iremonger J, Pickworth JA, et al., 2021, A diagnostic miRNA signature for pulmonary arterial hypertension using a consensus machine learning approach, EBioMedicine, Vol: 69, ISSN: 2352-3964
BACKGROUND: Pulmonary arterial hypertension (PAH) is a rare but life shortening disease, the diagnosis of which is often delayed, and requires an invasive right heart catheterisation. Identifying diagnostic biomarkers may improve screening to identify patients at risk of PAH earlier and provide new insights into disease pathogenesis. MicroRNAs are small, non-coding molecules of RNA, previously shown to be dysregulated in PAH, and contribute to the disease process in animal models. METHODS: Plasma from 64 treatment naïve patients with PAH and 43 disease and healthy controls were profiled for microRNA expression by Agilent Microarray. Following quality control and normalisation, the cohort was split into training and validation sets. Four separate machine learning feature selection methods were applied to the training set, along with a univariate analysis. FINDINGS: 20 microRNAs were identified as putative biomarkers by consensus feature selection from all four methods. Two microRNAs (miR-636 and miR-187-5p) were selected by all methods and used to predict PAH diagnosis with high accuracy. Integrating microRNA expression profiles with their associated target mRNA revealed 61 differentially expressed genes verified in two independent, publicly available PAH lung tissue data sets. Two of seven potentially novel gene targets were validated as differentially expressed in vitro in human pulmonary artery smooth muscle cells. INTERPRETATION: This consensus of multiple machine learning approaches identified two miRNAs that were able to distinguish PAH from both disease and healthy controls. These circulating miRNA, and their target genes may provide insight into PAH pathogenesis and reveal novel regulators of disease and putative drug targets.
Wojciak-Stothard B, Ainscough A, Smith T, et al., 2021, A MICROFLUIDIC CHIP FOR PULMONARY ARTERIAL HYPERTENSION
<jats:title>Abstract</jats:title> <jats:p>Pulmonary arterial hypertension (PAH) is an unmet clinical need. The lack of a disease model representative of the human condition is a key obstacle to the development of new treatments. Here we present a model of PAH, based on a biomimetic pulmonary artery (PA)-on-a-chip, that permits the study of the molecular and functional changes in human pulmonary vascular endothelial and smooth muscle cells in response to triggers of the disease and their response to drugs. We combine natural or induced BMPR2 dysfunction with hypoxia in vascular endothelial cells to trigger smooth muscle activation and proliferation and relate accompanying transcriptomic changes in affected cells to functional effects. Changes in gene expression consistent with observations made in genomic and biochemical studies of the human disease enable insights into underlying disease pathways and mechanisms of drug response. The model offers a novel, promising and more easily accessible approach for researchers to study pulmonary vascular remodelling and advance drug development in PAH.</jats:p>
Zhu N, Swietlik EM, Welch CL, et al., 2021, Rare variant analysis of 4241 pulmonary arterial hypertension cases from an international consortium implicates FBLN2, PDGFD, and rare de novo variants in PAH, Genome Medicine: medicine in the post-genomic era, Vol: 13, Pages: 1-18, ISSN: 1756-994X
BackgroundPulmonary arterial hypertension (PAH) is a lethal vasculopathy characterized by pathogenic remodeling of pulmonary arterioles leading to increased pulmonary pressures, right ventricular hypertrophy, and heart failure. PAH can be associated with other diseases (APAH: connective tissue diseases, congenital heart disease, and others) but often the etiology is idiopathic (IPAH). Mutations in bone morphogenetic protein receptor 2 (BMPR2) are the cause of most heritable cases but the vast majority of other cases are genetically undefined.MethodsTo identify new risk genes, we utilized an international consortium of 4241 PAH cases with exome or genome sequencing data from the National Biological Sample and Data Repository for PAH, Columbia University Irving Medical Center, and the UK NIHR BioResource – Rare Diseases Study. The strength of this combined cohort is a doubling of the number of IPAH cases compared to either national cohort alone. We identified protein-coding variants and performed rare variant association analyses in unrelated participants of European ancestry, including 1647 IPAH cases and 18,819 controls. We also analyzed de novo variants in 124 pediatric trios enriched for IPAH and APAH-CHD.ResultsSeven genes with rare deleterious variants were associated with IPAH with false discovery rate smaller than 0.1: three known genes (BMPR2, GDF2, and TBX4), two recently identified candidate genes (SOX17, KDR), and two new candidate genes (fibulin 2, FBLN2; platelet-derived growth factor D, PDGFD). The new genes were identified based solely on rare deleterious missense variants, a variant type that could not be adequately assessed in either cohort alone. The candidate genes exhibit expression patterns in lung and heart similar to that of known PAH risk genes, and most variants occur in conserved protein domains. For pediatric PAH, predicted deleterious de novo variants exhibited a significant burden compared to the background mutation rate (2.45×
Oldham WM, Hemnes AR, Aldred MA, et al., 2021, NHLBI-CMREF workshop report on pulmonary vascular disease classification: JACC state-of-the-art review., Journal of the American College of Cardiology, Vol: 77, Pages: 2040-2052, ISSN: 0735-1097
The National Heart, Lung, and Blood Institute and the Cardiovascular Medical Research and Education Fund held a workshop on the application of pulmonary vascular disease omics data to the understanding, prevention, and treatment of pulmonary vascular disease. Experts in pulmonary vascular disease, omics, and data analytics met to identify knowledge gaps and formulate ideas for future research priorities in pulmonary vascular disease in line with National Heart, Lung, and Blood Institute Strategic Vision goals. The group identified opportunities to develop analytic approaches to multiomic datasets, to identify molecular pathways in pulmonary vascular disease pathobiology, and to link novel phenotypes to meaningful clinical outcomes. The committee suggested support for interdisciplinary research teams to develop and validate analytic methods, a national effort to coordinate biosamples and data, a consortium of preclinical investigators to expedite target evaluation and drug development, longitudinal assessment of molecular biomarkers in clinical trials, and a task force to develop a master clinical trials protocol for pulmonary vascular disease.
Howard LSGE, He J, Watson GMJ, et al., 2021, Supplementation with iron in pulmonary arterial hypertension: two randomized crossover trials., Annals of the American Thoracic Society, Vol: 18, Pages: 981-988, ISSN: 1546-3222
RATIONALE: Iron deficiency, in the absence of anaemia, is common in patients with idiopathic and heritable pulmonary arterial hypertension (PAH) and is associated with a worse clinical outcome. Oral iron absorption may be impeded by elevated circulating hepcidin levels. The safety and benefit of parenteral iron replacement in this patient population is unclear. OBJECTIVES: To evaluate the safety and efficacy of parenteral iron replacement in pulmonary arterial hypertension. METHODS: In two randomised, double blind, placebo-controlled 12 week crossover studies, 39 patients in Europe received a single infusion of ferric carboxymaltose (Ferinject®) 1000 mg (or 15 mg/kg if weight < 66.7Kg) or saline as placebo and 17 patients in China received iron dextran (Cosmofer®) 20 mg iron/kg body weight or saline placebo. All patients had idiopathic or heritable PAH and iron deficiency at entry as defined by: a serum ferritin < 37 µg/l or iron < 10.3 µmol/l or transferrin saturations < 16.4%. RESULTS: Both iron treatments were well tolerated and improved iron status. Analysed separately and combined, there was no effect on any measure of exercise capacity (using cardiopulmonary exercise testing or 6 minute walk test) or cardio-pulmonary haemodynamics, as assessed by right heart catheterisation, cardiac magnetic resonance or plasma NT-proBNP, at 12 weeks. CONCLUSION: Iron repletion by administration of a slow release iron preparation as a single infusion to PAH patients with iron deficiency without overt anaemia was well tolerated but provided no significant clinical benefit at 12 weeks. Clinical trial registered with ClinicalTrials.gov (NCT01447628).
Wu Y, Wharton J, Walters R, et al., 2021, The pathophysiological role of novel pulmonary arterial hypertension gene SOX17., European Respiratory Journal, Vol: 57, ISSN: 0903-1936
Pulmonary arterial hypertension (PAH) is a progressive disease predominantly targeting pre-capillary blood vessels. Adverse structural re-modelling and increased pulmonary vascular resistance result in cardiac hypertrophy and ultimately failure of the right ventricle. Recent whole genome and exome sequencing studies have identified SOX17 as a novel risk gene in PAH, with a dominant mode of inheritance and incomplete penetrance. Rare deleterious variants in the gene and more common variants in upstream enhancer sites have both been associated with the disease and a deficiency of SOX17 expression may predispose to PAH. This review aims to consolidate the evidence linking genetic variants in SOX17 to PAH and explores the numerous targets and effects of the transcription factor, focussing on the pulmonary vasculature and the pathobiology of PAH.
Swietlik EM, Greene D, Zhu N, et al., 2021, Bayesian inference associates rare KDR variants with specific phenotypes in pulmonary arterial hypertension., Circulation: Genomic and Precision Medicine, Vol: 14, Pages: 57-70, ISSN: 2574-8300
Background - Approximately 25% of patients with pulmonary arterial hypertension (PAH) have been found to harbor rare mutations in disease-causing genes. To identify missing heritability in PAH we integrated deep phenotyping with whole-genome sequencing data using Bayesian statistics. Methods - We analyzed 13,037 participants enrolled in the NIHR BioResource - Rare Diseases (NBR) study, of which 1,148 were recruited to the PAH domain. To test for genetic associations between genes and selected phenotypes of pulmonary hypertension (PH), we used the Bayesian rare-variant association method BeviMed. Results - Heterozygous, high impact, likely loss-of-function variants in the Kinase Insert Domain Receptor (KDR) gene were strongly associated with significantly reduced transfer coefficient for carbon monoxide (KCO, posterior probability (PP)=0.989) and older age at diagnosis (PP=0.912). We also provide evidence for familial segregation of a rare nonsense KDR variant with these phenotypes. On computed tomographic imaging of the lungs, a range of parenchymal abnormalities were observed in the five patients harboring these predicted deleterious variants in KDR. Four additional PAH cases with rare likely loss-of-function variants in KDR were independently identified in the US PAH Biobank cohort with similar phenotypic characteristics. Conclusions - The Bayesian inference approach allowed us to independently validate KDR, which encodes for the Vascular Endothelial Growth Factor Receptor 2 (VEGFR2), as a novel PAH candidate gene. Furthermore, this approach specifically associated high impact likely loss-of-function variants in the genetically constrained gene with distinct phenotypes. These findings provide evidence for KDR being a clinically actionable PAH gene and further support the central role of the vascular endothelium in the pathobiology of PAH.
Harbaum L, Rhodes CJ, Otero-Núñez P, et al., 2021, The application of 'omics' to pulmonary arterial hypertension, British Journal of Pharmacology, Vol: 178, Pages: 108-120, ISSN: 0007-1188
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 strategy will reveal novel druggable targets and biomarkers that will open the way to personalised 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.
Chen CN, Zhao L, Rhodes C, et al., 2021, Pathobiology of Pulmonary Hypertension, Encyclopedia of Respiratory Medicine, Second Edition, Pages: 530-541, ISBN: 9780081027233
Pulmonary hypertension (PH) is a disease of progressive pulmonary vascular remodeling. The complexity of PH pathology, characterized by inflammation and dysregulated growth of pulmonary vascular cells, challenges current treatments. Clinical and translational research has played a major role in advancing our understanding of pathobiological mechanisms intrinsic to PH pathology, providing insights into new therapeutic targets.
Rhodes CJ, 2020, The cancer hypothesis of pulmonary arterial hypertension: are polyamines the new Warburg?, EUROPEAN RESPIRATORY JOURNAL, Vol: 56, ISSN: 0903-1936
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Ulrich A, Otero-Núñez P, Wharton J, et al., 2020, Expression quantitative trait locus mapping in pulmonary arterial hypertension, Genes, Vol: 11, ISSN: 2073-4425
Expression quantitative trait loci (eQTL) can provide a link between disease susceptibility variants discovered by genetic association studies and biology. To date, eQTL mapping studies have been primarily conducted in healthy individuals from population-based cohorts. Genetic effects have been known to be context-specific and vary with changing environmental stimuli. We conducted a transcriptome- and genome-wide eQTL mapping study in a cohort of patients with idiopathic or heritable pulmonary arterial hypertension (PAH) using RNA sequencing (RNAseq) data from whole blood. We sought confirmation from three published population-based eQTL studies, including the GTEx Project, and followed up potentially novel eQTL not observed in the general population. In total, we identified 2314 eQTL of which 90% were cis-acting and 75% were confirmed by at least one of the published studies. While we observed a higher GWAS trait colocalization rate among confirmed eQTL, colocalisation rate of novel eQTL reported for lung-related phenotypes was twice as high as that of confirmed eQTL. Functional enrichment analysis of genes with novel eQTL in PAH highlighted immune-related processes, a suspected contributor to PAH. These potentially novel eQTL specific to or active in PAH could be useful in understanding genetic risk factors for other diseases that share common mechanisms with PAH.
Swietlik EM, Ghataorhe P, Zalewska K, et al., 2020, Plasma metabolomics exhibit response to therapy in chronic thromboembolic pulmonary hypertension, European Respiratory Journal, Vol: 57, Pages: 1-14, ISSN: 0903-1936
Pulmonary hypertension is a condition with limited effective treatment options. Chronic thromboembolic pulmonary hypertension (CTEPH) is a notable exception with pulmonary endarterectomy (PEA) often proving curative. This study investigated the plasma metabolome of CTEPH patients, estimated reversibility to an effective treatment and explored the source of metabolic perturbations.We performed untargeted analysis of plasma metabolites in CTEPH patients compared to healthy controls and disease comparators. Changes in metabolic profile were evaluated in response to PEA. A subset of patients were sampled at three anatomical locations and plasma metabolite gradients calculated.We defined and validated altered plasma metabolite profiles in patients with CTEPH. 12 metabolites were confirmed by ROC analysis to distinguish CTEPH and both healthy (AUCs 0.64–0.94, all p<2×10−5) and disease controls (AUCs 0.58–0.77, all p<0.05. Many of the metabolic changes were notably similar to those observed in idiopathic pulmonary arterial hypertension (IPAH). Only five metabolites (5-methylthioadenosine, N1-methyladenosine, N1-methylinosine, 7-methylguanine, N-formylmethionine) distinguished CTEPH from chronic thromboembolic disease or IPAH. Significant corrections (15–100% of perturbation) in response to PEA were observed in some but not all metabolites. Anatomical sampling identified 188 plasma metabolites, with significant gradients in tryptophan, sphingomyelin, methionine, and Krebs cycle metabolites . Metabolites associated with CTEPH and gradients also showed significant associations with clinical measures of disease severity.We identified a specific metabolic profile that distinguishes CTEPH from controls and disease comparators, despite the observation that most metabolic changes were common to both CTEPH and IPAH patients. Plasma metabolite gradients implicate cardiopulmonary tissue metabolism of metabolites associated with PH and metabolites t
Swietlik E, Ghataorhe P, Zalewska K, et al., 2020, Plasma metabolomics in chronic thromboembolic pulmonary hypertension, Publisher: EUROPEAN RESPIRATORY SOC JOURNALS LTD, ISSN: 0903-1936
Otero-Nunez P, Rhodes C, Wharton J, et al., 2020, Multi-omic profiling in pulmonary arterial hypertension, Publisher: EUROPEAN RESPIRATORY SOC JOURNALS LTD, ISSN: 0903-1936
Rhodes C, Otero-Núñez P, Wharton J, et al., 2020, Whole blood RNA profiles associated with pulmonary arterial hypertension and clinical outcome, American Journal of Respiratory and Critical Care Medicine, Vol: 202, Pages: 586-594, ISSN: 1073-449X
Rationale: Idiopathic and hereditary pulmonary arterial hypertension (PAH) are rare but comprise a genetically heterogeneous patient group. RNA-sequencing linked to the underlying genetic architecture can be used to better understand the underlying pathology by identifying key signalling pathways and stratify patients more robustly according to clinical risk. Objectives: Using a three-stage design of RNA discovery, RNA validation/model construction and model validation to define a set of PAH-associated RNAs and a single summarising RNA model score. To define genes most likely to be involved in disease development, we performed Mendelian randomisation (MR) analysis. Methods: RNA-sequencing was performed on whole blood samples from 359 patients with idiopathic, heritable and drug-induced PAH and 72 age- and sex-matched healthy volunteers. The score was evaluated against disease severity markers including survival analysis using all-cause mortality from diagnosis. MR used known eQTL and summary statistics from a PAH GWAS. Measurements and Main Results: We identified 507 genes with differential RNA expression in PAH patients compared to controls. A model of 25 RNAs was able to distinguish PAH with 87% accuracy (AUC 95% CI: 0.791-0.945) in model validation. The RNA model score was associated with disease severity and long-term survival (p=4.66x10-6) in PAH. MR detected an association between SMAD5 levels and PAH disease susceptibility (OR:0.317, 95%CI:0.129-0.776, p=0.012). Conclusions: A whole blood RNA signature of PAH, which includes RNAs relevant to disease pathogenesis, associates with disease severity and identifies patients with poor clinical outcomes. Genetic variants associated with lower SMAD5 expression may increase susceptibility to PAH.
Thaventhiran JED, Lango Allen H, Burren OS, et al., 2020, Whole-genome sequencing of a sporadic primary immunodeficiency cohort (vol 583, pg 90, 2020), Nature, Vol: 584, Pages: E2-E2, ISSN: 0028-0836
Thaventhiran JED, Lango Allen H, Burren OS, et al., 2020, Whole-genome sequencing of a sporadic primary immunodeficiency cohort, Nature, Vol: 583, Pages: 90-95, ISSN: 0028-0836
Primary immunodeficiency (PID) is characterized by recurrent and often life-threatening infections, autoimmunity and cancer, and it poses major diagnostic and therapeutic challenges. Although the most severe forms of PID are identified in early childhood, most patients present in adulthood, typically with no apparent family history and a variable clinical phenotype of widespread immune dysregulation: about 25% of patients have autoimmune disease, allergy is prevalent and up to 10% develop lymphoid malignancies1-3. Consequently, in sporadic (or non-familial) PID genetic diagnosis is difficult and the role of genetics is not well defined. Here we address these challenges by performing whole-genome sequencing in a large PID cohort of 1,318 participants. An analysis of the coding regions of the genome in 886 index cases of PID found that disease-causing mutations in known genes that are implicated in monogenic PID occurred in 10.3% of these patients, and a Bayesian approach (BeviMed4) identified multiple new candidate PID-associated genes, including IVNS1ABP. We also examined the noncoding genome, and found deletions in regulatory regions that contribute to disease causation. In addition, we used a genome-wide association study to identify loci that are associated with PID, and found evidence for the colocalization of-and interplay between-novel high-penetrance monogenic variants and common variants (at the PTPN2 and SOCS1 loci). This begins to explain the contribution of common variants to the variable penetrance and phenotypic complexity that are observed in PID. Thus, using a cohort-based whole-genome-sequencing approach in the diagnosis of PID can increase diagnostic yield and further our understanding of the key pathways that influence immune responsiveness in humans.
Turro E, Astle WJ, Megy K, et al., 2020, Whole-genome sequencing of patients with rare diseases in a national health system, Nature, Vol: 583, Pages: 96-102, ISSN: 0028-0836
Most patients with rare diseases do not receive a molecular diagnosis and the aetiological variants and causative genes for more than half such disorders remain to be discovered1. Here we used whole-genome sequencing (WGS) in a national health system to streamline diagnosis and to discover unknown aetiological variants in the coding and non-coding regions of the genome. We generated WGS data for 13,037 participants, of whom 9,802 had a rare disease, and provided a genetic diagnosis to 1,138 of the 7,065 extensively phenotyped participants. We identified 95 Mendelian associations between genes and rare diseases, of which 11 have been discovered since 2015 and at least 79 are confirmed to be aetiological. By generating WGS data of UK Biobank participants2, we found that rare alleles can explain the presence of some individuals in the tails of a quantitative trait for red blood cells. Finally, we identified four novel non-coding variants that cause disease through the disruption of transcription of ARPC1B, GATA1, LRBA and MPL. Our study demonstrates a synergy by using WGS for diagnosis and aetiological discovery in routine healthcare.
Sindi HA, Russomanno G, Satta S, et al., 2020, Therapeutic potential of KLF2-induced exosomal microRNAs in pulmonary hypertension (vol 33, pg 631, 2020), Nature Communications, Vol: 11, Pages: 1-1, ISSN: 2041-1723
Rhodes CJ, 2020, Targeting vessel formation in pulmonary arterial hypertension: is the endostatin-Id1-thrombospondin 1 pathway a new hope?, American Journal of Respiratory Cell and Molecular Biology, Vol: 62, Pages: 411-412, ISSN: 1044-1549
Sindi H, Russomanno G, Satta S, et al., 2020, Therapeutic potential of KLF2 induced exosomal microRNAs in pulmonary hypertension, Nature Communications, Vol: 11, ISSN: 2041-1723
Pulmonary arterial hypertension (PAH) is a severe disorder of lung vasculature that causes right heart failure. Homeostatic effects of flow-activated transcription factor Krüppel-like factor 2 (KLF2) are compromised in PAH. Here we show that KLF2-induced exosomal microRNAs, miR-181a-5p and miR-324-5p act together to attenuate pulmonary vascular remodeling and that their actions are mediated by Notch4 and ETS1 and other key regulators of vascular homeostasis. Expressions of KLF2, miR-181a-5p and miR-324-5p are reduced, while levels of their target genes are elevated in pre-clinical PAH, idiopathic PAH and heritable PAH with missense p.H288Y KLF2 mutation. Therapeutic supplementation of miR-181a-5p and miR-324-5p reduces proliferative and angiogenic responses in patient-derived cells and attenuates disease progression in PAH mice.This study shows that reduced KLF2 signaling is a common feature of human PAH and highlights the potential therapeutic role of KLF2-regulated exosomal miRNAs in PAH and other diseases associated with vascular remodelling.
Hodgson J, Swietlik EM, Salmon RM, et al., 2020, Characterization of GDF2 mutations and levels of BMP9 and BMP10 in pulmonary arterial hypertension, American Journal of Respiratory and Critical Care Medicine, Vol: 201, Pages: 575-585, ISSN: 1073-449X
OBJECTIVES: Recently, rare heterozygous mutations in GDF2 were identified in patients with pulmonary arterial hypertension (PAH). GDF2 encodes the circulating bone morphogenetic protein, BMP9, which is a ligand for the BMP type 2 receptor (BMPR2). Here we determine the functional impact of GDF2 mutations and characterised plasma BMP9 and BMP10 levels in patients with idiopathic PAH. METHODS: Missense BMP9 mutant proteins were expressed in vitro and the impact on BMP9 protein processing and secretion, endothelial signalling and functional activity was assessed. Plasma BMP9 and BMP10 levels and activity were assayed in PAH patients with GDF2 mutations, and controls. Levels were also measured in a larger cohort of controls (n=120) and idiopathic PAH patients (n=260). MAIN RESULTS: We identified novel rare variation at the GDF2 and BMP10 loci, including copy number variation. In vitro, BMP9 missense proteins demonstrated impaired cellular processing and secretion. PAH patients carrying these mutations exhibited reduced plasma levels of BMP9 and reduced BMP activity. Unexpectedly, plasma BMP10 levels were also markedly reduced in these individuals. Although overall BMP9 and BMP10 levels did not differ between PAH patients and controls, BMP10 levels were lower in PAH females. A subset of PAH patients had markedly reduced plasma levels of BMP9 and BMP10 in the absence of GDF2 mutations. CONCLUSIONS: Our findings demonstrate that GDF2 mutations result in BMP9 loss-of-function and are likely causal. These mutations lead to reduced circulating levels of both BMP9 and BMP10. These findings support therapeutic strategies to enhance BMP9 or BMP10 signalling in PAH.
Ulrich A, Wharton J, Thayer T, et al., 2020, Mendelian randomization analysis of red cell distribution width in pulmonary arterial hypertension, European Respiratory Journal, Vol: 55, Pages: 1-9, ISSN: 0903-1936
Pulmonary arterial hypertension (PAH) is a rare disease that leads to premature death from right heart failure. It is strongly associated with elevated red cell distribution width (RDW), a correlate of several iron status biomarkers. High RDW values can signal early stage iron deficiency or iron deficiency anaemia. This study investigated if elevated RDW is causally associated with PAH.A two-sample Mendelian randomization (MR) approach was applied to investigate whether genetic predisposition to higher levels of RDW increases the odds of developing PAH. Primary and secondary MR analyses were performed using all available genome-wide significant RDW variants (n = 179) and five genome-wide significant RDW variants that act via systemic iron status, respectively. We confirmed the observed association between RDW and PAH (OR = 1.90, 95% CI = 1.80 - 2.01) in a multi-centre case-control study (N cases = 642, N disease controls = 15,889). The primary MR analysis was adequately powered to detect a causal effect (OR) from between 1.25-1.52 or greater based on estimates reported in the RDW GWAS or from our own data. There was no evidence for a causal association between RDW and PAH in either the primary (ORcausal = 1.07, 95% CI = 0.92 – 1.24) or the secondary (ORcausal = 1.09, 95% CI = 0.77 – 1.54) MR analysis.The results suggest that at least some of the observed association of RDW with PAH is secondary to disease progression. Results of iron therapeutic trials in PAH should be interpreted with caution as any improvements observed may not be mechanistically linked to the development of PAH.Take home message – Mendelian randomization using genetic data from the largest-to-date pulmonary arterial hypertension (PAH) cohort do not support RDW or iron deficiency as a cause of PAH, which is important when interpreting iron replacement trials in this condition.
Swietlik E, Greene D, Zhu N, et al., 2019, Bayesian inference associates rare KDR variants with specific phenotypes in pulmonary arterial hypertension, Circulation: Genomic and Precision Medicine, ISSN: 2574-8300
<h4>Background</h4> Approximately 25% of patients with pulmonary arterial hypertension (PAH) have been found to harbor rare mutations in disease-causing genes. To identify missing heritability in PAH we integrated deep phenotyping with whole-genome sequencing data using Bayesian statistics. <h4>Methods</h4> We analyzed 13,037 participants enrolled in the NIHR BioResource - Rare Diseases (NBR) study, of which 1,148 were recruited to the PAH domain. To test for genetic associations between genes and selected phenotypes of pulmonary hypertension (PH), we used the Bayesian rare-variant association method BeviMed. <h4>Results</h4> Heterozygous, high impact, likely loss-of-function variants in the Kinase Insert Domain Receptor ( KDR ) gene were strongly associated with significantly reduced transfer coefficient for carbon monoxide (KCO, posterior probability (PP)=0.989) and older age at diagnosis (PP=0.912). We also provide evidence for familial segregation of a rare nonsense KDR variant with these phenotypes. On computed tomographic imaging of the lungs, a range of parenchymal abnormalities were observed in the five patients harboring these predicted deleterious variants in KDR . Four additional PAH cases with rare likely loss-of-function variants in KDR were independently identified in the US PAH Biobank cohort with similar phenotypic characteristics. <h4>Conclusions</h4> The Bayesian inference approach allowed us to independently validate KDR , which encodes for the Vascular Endothelial Growth Factor Receptor 2 (VEGFR2), as a novel PAH candidate gene. Furthermore, this approach specifically associated high impact likely loss-of-function variants in the genetically constrained gene with distinct phenotypes. These findings provide evidence for KDR being a clinically actionable PAH gene and further support the central role of the vascular endothelium in the pathobiology of PAH.
Frid MG, McKeon BA, Thurman JM, et al., 2019, Immunoglobulin-driven complement activation regulates pro-inflammatory remodeling in pulmonary hypertension., American Journal of Respiratory and Critical Care Medicine, Vol: 201, Pages: 224-239, ISSN: 1073-449X
RATIONALE: Pulmonary (arterial) hypertension (PH/PAH) is a life-threatening cardiopulmonary disorder where inflammation and immunity have emerged as critical early pathogenic elements. Although pro-inflammatory processes in PH/PAH are the focus of extensive investigation, the initiating mechanisms remain elusive. OBJECTIVES: We tested whether activation of the complement cascade is critical in regulating pro-inflammatory and pro-proliferative processes in the initiation of experimental hypoxic PH, and can serve as a prognostic biomarker of outcome in human PAH. METHODS: We employed immunostaining of lung tissues from experimental PH models and PAH patients; analyses of genetic murine models lacking specific complement components or circulating immunoglobulins; cultured human pulmonary adventitial fibroblasts; and network medicine analysis of a biomarker risk panel from plasma of PAH patients. MEASUREMENTS AND MAIN RESULTS: Pulmonary perivascular-specific activation of the complement cascade was identified as a consistent critical determinant of PH/PAH in experimental animal models and humans. In experimental hypoxic PH, pro-inflammatory and pro-proliferative responses were complement (Alternative pathway and C5)-dependent, and immunoglobulins, particularly IgG, were critical for activation of the complement cascade. We identify Csf2/GM-CSF as a primary complement-dependent inflammatory mediator. Furthermore, using network medicine analysis of a biomarker risk panel from plasma of PAH patients, we demonstrate that complement signaling can serve as a prognostic factor for clinical outcome in PAH. CONCLUSIONS: The present study establishes immunoglobulin-driven dysregulated complement activation as a critical pathobiological mechanism regulating pro-inflammatory/pro-proliferative processes in the initiation of experimental hypoxic PH, and demonstrates complement signaling as a critical determinant of clinical outcome of in PAH.
Kaakinen M, Rhodes CJ, Humbert M, et al., 2019, Genome-wide association study of 1,124 protein levels in pulmonary arterial hypertension patients identifies a novel <i>trans</i>-pQTL at <i>ELK2AP</i> for Death Receptor 3, 51st Conference of the European-Society-of-Human-Genetics (ESHG) in conjunction with the European Meeting on Psychosocial Aspects of Genetics (EMPAG), Publisher: NATURE PUBLISHING GROUP, Pages: 590-590, ISSN: 1018-4813
Attard M, Dawes T, Simoes Monteiro de Marvao A, et al., 2019, Metabolic pathways associated with right ventricular adaptation to pulmonary hypertension: Three dimensional analysis of cardiac magnetic resonance imaging, EHJ Cardiovascular Imaging / European Heart Journal - Cardiovascular Imaging, Vol: 20, Pages: 668-676, ISSN: 2047-2412
AimsWe sought to identify metabolic pathways associated with right ventricular (RV) adaptation to pulmonary hypertension (PH). We evaluated candidate metabolites, previously associated with survival in pulmonary arterial hypertension, and used automated image segmentation and parametric mapping to model their relationship to adverse patterns of remodelling and wall stress.Methods and resultsIn 312 PH subjects (47.1% female, mean age 60.8 ± 15.9 years), of which 182 (50.5% female, mean age 58.6 ± 16.8 years) had metabolomics, we modelled the relationship between the RV phenotype, haemodynamic state, and metabolite levels. Atlas-based segmentation and co-registration of cardiac magnetic resonance imaging was used to create a quantitative 3D model of RV geometry and function—including maps of regional wall stress. Increasing mean pulmonary artery pressure was associated with hypertrophy of the basal free wall (β = 0.29) and reduced relative wall thickness (β = −0.38), indicative of eccentric remodelling. Wall stress was an independent predictor of all-cause mortality (hazard ratio = 1.27, P = 0.04). Six metabolites were significantly associated with elevated wall stress (β = 0.28–0.34) including increased levels of tRNA-specific modified nucleosides and fatty acid acylcarnitines, and decreased levels (β = −0.40) of sulfated androgen.ConclusionUsing computational image phenotyping, we identify metabolic profiles, reporting on energy metabolism and cellular stress-response, which are associated with adaptive RV mechanisms to PH.
Gorman KM, Meyer E, Grozeva D, et al., 2019, Bi-allelic Loss-of-Function <i>CACNA1B</i> Mutations in Progressive Epilepsy-Dyskinesia, AMERICAN JOURNAL OF HUMAN GENETICS, Vol: 104, Pages: 948-956, ISSN: 0002-9297
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Newnham M, South K, Bleda M, et al., 2019, The ADAMTS13-VWF axis is dysregulated in chronic thromboembolic pulmonary hypertension, European Respiratory Journal, Vol: 53, ISSN: 0903-1936
Chronic thromboembolic pulmonary hypertension (CTEPH) is an important consequence of pulmonary embolism (PE) that is associated with abnormalities in haemostasis. We investigated the ADAMTS13-VWF axis in CTEPH, including its relationship to disease severity, inflammation, ABO groups and ADAMTS13 genetic variants.ADAMTS13 and VWF plasma antigen levels were measured in patients with CTEPH (n=208), chronic thromboembolic disease without pulmonary hypertension (CTED; n=35), resolved PE (n=28), idiopathic pulmonary arterial hypertension (n=30) and healthy controls (n=68). CTEPH genetic ABO associations and protein quantitative trait loci were investigated. ADAMTS-VWF axis abnormalities were assessed in CTEPH and healthy control subsets by measuring ADAMTS13 activity, D-dimers and VWF-multimeric size.CTEPH patients had decreased ADAMTS13 (adjusted β (95% CI)=−23.4 (−30.9– −15.1)%, p<0.001) and increased VWF levels (β=+75.5 (44.8–113)%, p<0.001) compared to healthy controls. ADAMTS13 levels remained low after reversal of pulmonary hypertension by pulmonary endarterectomy surgery and were equally reduced in CTED. We identify a genetic variant near the ADAMTS13 gene associated with ADAMTS13 protein that accounted for ∼8% of the variation in levels.The ADAMTS13-VWF axis is dysregulated in CTEPH. This is unrelated to pulmonary hypertension, disease severity or markers of systemic inflammation and implicates the ADAMTS13-VWF axis in CTEPH pathobiology.
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