Search

Surgically accessible lesions of chronic thromboembolic pulmonary hypertension (CTEPH) are classified as proximal or distal based on the distribution of thrombus burden in the pulmonary vasculature post operatively. Surgically accessible distal CTEPH lesions typically has a higher risk profile and worse clinical outcomes in less experienced centers, but the underlying molecular differences between proximal and distal CTEPH lesions remain unknown. Oxylipins, a diverse group of bioactive lipid mediators, have previously been implicated in a range of disorders including pulmonary hypertension. Therefore, we sought to characterize oxylipin profiles among patients with proximal and distal operable CTEPH lesions, as well as those with idiopathic pulmonary arterial hypertension (IPAH). We studied 271 patients with proximal operable CTEPH (n=123), distal operable CTEPH (n=74), or IPAH (n=74). Liquid chromatography-mass spectrometry was used to analyze oxylipin profiles in each patient. We found that patients with distal operable CTEPH had elevated levels of proinflammatory oxylipins while those with proximal CTEPH had an increase in procoagulant oxylipins. Notably, the proinflammatory oxylipins elevated in distal operable CTEPH were similarly elevated in IPAH. These findings suggest that distal operable and proximal CTEPH represent heterogenous disease processes. Furthermore, oxylipin profiles may be useful for potential risk stratification and therapeutic targeting in CTEPH.

The molecular signature in patients with systemic sclerosis (SSc)-associated pulmonary arterial hypertension (SSc-PAH) relative to idiopathic pulmonary arterial hypertension (IPAH) remain unclear. We hypothesize that patients with SSc-PAH exhibit unfavorable bioactive metabolite derangements compared to IPAH that contribute to their poor prognosis and limited response to therapy. We sought to determine whether circulating bioactive metabolites are differentially altered in SSc-PAH versus IPAH.Plasma biosamples from 415 patients with SSc-PAH (cases) and 1115 patients with IPAH (controls) were included in the study. Over 700 bioactive metabolites were assayed in plasma samples from independent discovery and validation cohorts using liquid chromatography - mass spectrometry (LC-MS) based approaches. Regression analyses were used to identify metabolites which exhibited differential levels between SSc-PAH and IPAH and associated with disease severity.From among hundreds of circulating bioactive molecules, twelve metabolites were found to distinguish between SSc-PAH and IPAH, as well as associate with PAH disease severity. SSc-PAH patients had increased levels of fatty acid metabolites including lignoceric acid and nervonic acid, as well as kynurenine, polyamines, eicosanoids/oxylipins and sex hormone metabolites relative to IPAH. In conclusion, SSc-PAH patients are characterized by an unfavorable bioactive metabolic profile that may explain the poor and limited response to therapy. These data provide important metabolic insights into the pathogenesis of SSc-PAH.Take Home MessageAmong patients with PAH, those with SSc-PAH suffer disproportionately worse outcomes and disease course. This study represents the most comprehensive analysis of bioactive metabolites profiling comparing two subgroups of PAH. The findings shed light on key differences between SSc-PAH and IPAH that provide important metabolic insight into the disease pathogenesis.

BackgroundGroup 1 pulmonary 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. Recent high-throughput sequencing studies have identified additional PAH risk genes and suggested differences in genetic causes by age of onset. However, known risk genes explain only 15-20% of non-familial idiopathic PAH cases.MethodsTo identify new risk genes, we utilized an international consortium of 4,241 PAH cases with 4,175 sequenced exomes (n=2,572 National Biological Sample and Data Repository for PAH; n=469 Columbia University Irving Medical Center, enriched for pediatric trios) and 1,134 sequenced genomes (UK NIHR Bioresource – Rare Diseases Study). Most of the cases were adult-onset disease (93%), and 55% idiopathic (IPAH) and 35% associated with other diseases (APAH). We identified protein-coding variants and performed rare variant association analyses in unrelated participants of European ancestry, including 2,789 cases and 18,819 controls (11,101 unaffected parents from the Simons Powering Autism Research for Knowledge study and 7,718 gnomAD individuals). We analyzedde novovariants in 124 pediatric trios.ResultsSeven genes with rare deleterious variants were significantly associated (false discovery rate BMPR2,GDF2, andTBX4), two recently identified candidate genes (SOX17,KDR), and two new candidate genes (FBLN2, fibulin 2;PDGFD, platelet-derived growth factor D). The candidate genes exhibit expression patterns in lung and heart similar to that of known PAH risk genes, and most of the variants occur in conserved protein domains. Variants in known PAH gene,ACVRL1, showed association with APAH. Predicted deleteriousde novovariants in pediatric cases exhibited a significant burden compared to the background mutation rate (2.5x, p=7.0E-6). At least eight novel candidate genes carryingde novovariants have plausible roles in lung/heart development.ConclusionsRare variant analysis of a large international consortium identifies two new candidate genes -FBLN2andPDGFD. The new genes have known functions in vasculogenesis and remodeling but have not been previously implicated in PAH. Trio analysis predicts that ~15% of pediatric IPAH may be explained byde novovariants.

BackgroundApproximately 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.MethodsWe 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.ResultsHeterozygous, 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.ConclusionsThe 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.

Group 1 pulmonary arterial hypertension (PAH) is a rare disease with high mortality despite recent therapeutic advances. Pathogenic remodeling of pulmonary arterioles leads to increased pulmonary pressures, right ventricular hypertrophy and heart failure. Mutations in bone morphogenetic protein receptor type 2 and other risk genes predispose to disease, but the vast majority of non-familial cases remain genetically undefined. To identify new risk genes, we performed exome sequencing in a large cohort from the National Biological Sample and Data Repository for PAH. By statistical association of rare deleterious variants, we found tissue kallikrein 1 and gamma glutamyl carboxylase as new candidate risk genes for idiopathic PAH associated with a later age-of-onset and relatively moderate disease phenotype compared to bone morphogenetic receptor type 2. Both genes play important roles in vascular hemodynamics and inflammation but have not been implicated in PAH previously. These data suggest new genes, pathogenic mechanisms and therapeutic targets for this lethal vasculopathy.