Familial Pulmonary Arterial Hypertension Research Articles

TNFRSF13B c.226G>A (p.Gly76Ser) as a Novel Causative Mutation for Pulmonary Arterial Hypertension.

BackgroundRecently, some studies reported the pulmonary artery hypertension (PAH)–associated genes. However, a majority of patients with familial or sporadic PAH lack variants in the known pathogenic genes. In this study, we investigated the new causative gene variants associated with PAH.Methods and ResultsWhole‐exome sequencing in 242 Japanese patients with familial or sporadic PAH identified a heterozygous substitution change involving c.226G>A (p.Gly76Ser) in tumor necrotic factor receptor superfamily 13B gene (TNFRSF13B) in 6 (2.5%) patients. TNFRSF13B controls the differentiation of B cell and secretion of inflammatory cytokines and may be involved in vascular inflammation. In silico structural analysis simulation demonstrated the structural instability of the N‐terminal region of the protein synthesized from TNFRSF13B p.Gly76Ser variant. These suggest that the TNFRSF13B p.Gly76Ser variant may be involved in the development of PAH via aberrant inflammation in pulmonary vessels.Conclusions TNFRSF13B p.Gly76Ser variant is a candidate of novel causative gene variant for PAH.

Redox and Inflammatory Signaling, the Unfolded Protein Response, and the Pathogenesis of Pulmonary Hypertension.

Protein folding overload and oxidative stress disrupt endoplasmic reticulum (ER) homeostasis, generating reactive oxygen species (ROS) and activating the unfolded protein response (UPR). The altered ER redox state induces further ROS production through UPR signaling that balances the cell fates of survival and apoptosis, contributing to pulmonary microvascular inflammation and dysfunction and driving the development of pulmonary hypertension (PH). UPR-induced ROS production through ER calcium release along with NADPH oxidase activity results in endothelial injury and smooth muscle cell (SMC) proliferation. ROS and calcium signaling also promote endothelial nitric oxide (NO) synthase (eNOS) uncoupling, decreasing NO production and increasing vascular resistance through persistent vasoconstriction and SMC proliferation. C/EBP-homologous protein further inhibits eNOS, interfering with endothelial function. UPR-induced NF-κB activity regulates inflammatory processes in lung tissue and contributes to pulmonary vascular remodeling. Conversely, UPR-activated nuclear factor erythroid 2-related factor 2-mediated antioxidant signaling through heme oxygenase 1 attenuates inflammatory cytokine levels and protects against vascular SMC proliferation. A mutation in the bone morphogenic protein type 2 receptor (BMPR2) gene causes misfolded BMPR2 protein accumulation in the ER, implicating the UPR in familial pulmonary arterial hypertension pathogenesis. Altogether, there is substantial evidence that redox and inflammatory signaling associated with UPR activation is critical in PH pathogenesis.

Pulmonary Hypertension and Pregnancy

Pregnancy in patients with any type of pulmonary hypertension (PH) is associated with significant morbidity and mortality. That is why pulmonary artery hypertension (PAH) is a contraindication to pregnancy and belongs to class IV maternal cardiovascular risks. Maternal mortality rates for pulmonary (especially arterial) hypertension remain high even in the era of specific therapy, in particular, it reaches 12-30% in patients with PAH, 36% in Eisenmenger syndrome and up to 56% in secondary PH. Perinatal effects in such patients are also unfavorable, with high rates of fetal loss, premature birth and miscarriage.
 Multidisciplinary team of specialists of the National Amosov Institute of Cardiovascular Surgery and Institute of Pediatrics, Obstetrics and Gynecology named after acad. O. M. Lukianova has been providing medical support to such women for 7 years, using modern recommendations and wide experience. Overall, 39 pregnant and parturient women with PH were admitted to the clinic of the National Amosov Institute of Cardiovascular Surgery in the period from December 2013 to October 2020. Patients with PH were assigned to group II (n=24), and those with PAH (8 women) and acute PH (7 women) were assigned to group I. A total of 20 cardiac surgeries were performed. Patients with acute PH (n=6) underwent operations with cardiopulmonary bypass, those with critical mitral valve stenosis had “closed” off-pump surgery, and also there was one case of ECMO system implantation in patient with dilated cardiomyopathy (CMP). Endovascular operations (n=4) involved occluder implantation to patent ductus arteriosus (PDA), implantation of a cardioverter-defibrillator, cardiac resynchronization therapy with pacemaker (CRT-P) and cava-filter insertion. Early (n=1) and late (n=1) maternal mortality rates were 2.6% each. Perinatal loss (n=5) was 12.8%.
 The main goal at the preconception stage in patients with PH is to eliminate causative factors, and, if it is impossible (idiopathic, familial PAH, Eisenmenger syndrome, etc.), to avoid pregnancy. Patients who become pregnant should be informed of the high risk of pregnancy and discuss abortion, regardless of the WHO FC or other predictive markers. At prolongation of pregnancy careful clinical monitoring, by pregnancy heart team members is strongly recommended. Multidisciplinary support of pregnant women with PH is the cornerstone of a successful treatment strategy for such patients. The professional association of obstetric risk specialists, cardiologists, interventionists, neonatologists, and cardiac surgeons significantly increases the chances of a PH patient for safe delivery and giving birth to a healthy baby.

Abstract 15259: Breast Cancer and Heritable Pah Due to Bmpr2 Mutation: An Unexpected Discovery

Introduction: BMPR2 mutation is reported in 80% of familial PAH and 20% of idiopathic cases. Recently, a rat model of hereditary Pulmonary Arterial Hypertension with a BMPR2 loss-of-function mutation has been generated. Similarly to human, only around 20% of the rats spontaneously developed mild PAH. Unexpectedly, we observed that 20% (95%CI:12-28) of the 82 Bmpr2+/Δ71 rats (93% of females) versus 4% (95%CI:0-9)of the 84 age-matched wild type littermates spontaneously developed mammary masses requiring euthanasia. Interestingly, rats with tumor had elevated PA and clearly exhibit PAH signs. Hypothesis: We hypothesized that mammary tumor exacerbates the penetrance of PAH in the BMPR2 mutated female rats. Methods/Results: BMPR2 mutated and wild-type female young rats were treated with the breast cancer inducer 7, 12- diméthylbenz(a)anthracene (DMBA) or Vehicle. DMBA causes on average more tumors development in BMPR2 mutated rats versus WT rats (6,2 vs. 4) P=0,0275. Compare to both vehicle-treated and DMBA rats (without tumor) BMPR2 mutated rats with DMBA-induced tumors had a significant increase in mean PA pressure (p<0,0001); total pulmonary resistance (p<0,0001) and a significant decrease in cardiac output (P=0,0293). Histologically, these changes were associated with an increase of pulmonary artery remodelling assessed by immunofluorescence. Mechanistically, development of PAH in the BMPR2 mutated rats with tumor was associated with a significant upregulation of BRD4 (western blot) (p=0,0149); IL-1β (P=0,0052), BRD3 (P=0,0791) and BIRC5 (P=0,0166) mRNA expression levels. Co-culture experiments with breast cancer cells and PASMC from both WT and BMPR2 mutated rats are ongoing to identify whether cancer cells are realising factors responsible for BRD4 activation and thus PASMC proliferation and resistance to apoptosis. Conclusions: We demonstrated for the first time that breast cancer exacerbates PAH development in BMPR2 mutated rats. Increased BRDs driven pro-inflammatory signalling is associated with PAH development in BMPR2 mutated rats. We are currently exploring whether BMPR2 mutated patients are more prone to breast cancer development or not and whether PAH development occurs more frequently in breast cancer patients.

Endoplasmic Reticulum Associated Protein Degradation (ERAD) in the Pathology of Diseases Related to TGFβ Signaling Pathway: Future Therapeutic Perspectives.

The transforming growth factor signaling pathway (TGFβ) controls a wide range of cellular activities in adulthood as well as during embryogenesis including cell growth, differentiation, apoptosis, immunological responses and other cellular functions. Therefore, germline mutations in components of the pathway have given rise to a heterogeneous spectrum of hereditary diseases with variable phenotypes associated with malformations in the cardiovascular, muscular and skeletal systems. Our extensive literature and database searches revealed 47 monogenic diseases associated with germline mutations in 24 out of 41 gene variant encoding for TGFβ components. Most of the TGFβ components are membrane or secretory proteins and they are therefore expected to pass through the endoplasmic reticulum (ER), where fidelity of proteins folding is stringently monitored via the ER quality control machineries. Elucidation of the molecular mechanisms of mutant proteins’ folding and trafficking showed the implication of ER associated protein degradation (ERAD) in the pathogenesis of some of the diseases. For example, hereditary hemorrhagic telangiectasia types 1 and 2 (HHT1 and HHT2) and familial pulmonary arterial hypertension (FPAH) associated with mutations in Endoglin, ALK1 and BMPR2 components of the signaling pathway, respectively, have all exhibited loss of function phenotype as a result of ER retention of some of their disease-causing variants. In some cases, this has led to premature protein degradation through the proteasomal pathway. We anticipate that ERAD will be involved in the mechanisms of other TGFβ signaling components and therefore warrants further research. In this review, we highlight advances in ER quality control mechanisms and their modulation as a potential therapeutic target in general with particular focus on prospect of their implementation in the treatment of monogenic diseases associated with TGFβ components including HHT1, HHT2, and PAH. In particular, we emphasis the need to establish disease mechanisms and to implement such novel approaches in modulating the molecular pathway of mutant TGFβ components in the quest for restoring protein folding and trafficking as a therapeutic approach.

United States Pulmonary Hypertension Scientific Registry: Baseline Characteristics

The treatment, genotyping, and phenotyping of patients with World Health Organization Group 1 pulmonary arterial hypertension (PAH) have evolved dramatically in the last decade. The United States Pulmonary Hypertension Scientific Registry was established as the first US PAH patient registry to investigate genetic information, reproductive histories, and environmental exposure data in a contemporary patient population. Investigators at 15 US centers enrolled consecutively screened adults diagnosed with Group 1 PAH who had enrolled in the National Biological Sample and Data Repository for PAH (PAH Biobank) within 5 years of a cardiac catheterization demonstrating qualifying hemodynamic criteria. Exposure and reproductive histories were collected by using a structured interview and questionnaire. The biobank provided genetic data. Between 2015 and 2018, a total of 499 of 979 eligible patients with clinical diagnoses of idiopathic PAH (IPAH) or familial PAH (n= 240 [48%]), associated PAH (APAH; n= 256 [51%]), or pulmonary venoocclusive disease/pulmonary capillary hemangiomatosis (n= 3 [1%]) enrolled. The mean age was 55.8 years, average BMI was 29.2kg/m2, and 79%were women. Mean duration between symptom onset and diagnostic catheterization was 1.9 years. Sixty-six percent of patients were treated with more than one PAH medication at enrollment. Past use of prescription weight loss drugs (16%), recreational drugs (27%), and oral contraceptive pills (77%) was common. Women often reported miscarriage (37%), although PAH was rarely diagnosed within 6months of pregnancy (1.9%). Results of genetic testing identified pathogenic or suspected pathogenic variants in 13%of patients, reclassifying 18%of IPAH patients and 5%of APAH patients to heritable PAH. Patients with Group 1 PAH remain predominately middle-aged women diagnosed with IPAH or APAH. Delays in diagnosis of PAH persist. Treatment with combinations of PAH-targeted medications is more common than in the past. Women often report pregnancy complications, as well as exposure to anorexigens, oral contraceptives, and/or recreational drugs. Results of genetic tests frequently identify unsuspected heritable PAH.

Comprehensive identification of signaling pathways for idiopathic pulmonary arterial hypertension.

Whole exome sequencing (WES) was used in the research of familial pulmonary arterial hypertension (FPAH). CAV1 and KCNK3 were found as two novel candidate genes of FPAH. However, few pathogenic genes were identified in idiopathic pulmonary arterial hypertension (IPAH). We conducted WES in 20 unrelated IPAH patients who did not carry the known PAH-pathogenic variants among BMPR2, CAV1, KCNK3, SMAD9, ALK1, and ENG. We found a total of 4,950 variants in 3,534 genes, including 4,444 single-nucleotide polymorphisms and 506 insertions/deletions (InDels). Through the comprehensive and multilevel analysis, we disclosed several novel signaling cascades significantly connected to IPAH, including variants related to cadherin signaling pathway, dilated cardiomyopathy, glucose metabolism, immune response, mucin-type O-glycosylation, phospholipase C (PLC)-activating G protein-coupled receptor (GPCR) signaling pathway, vascular contraction and generation, and voltage-dependent Ca2+ channels. We also conducted validation studies in five mutant genes related to PLC-activating GPCR signaling pathway potentially involved in intracellular calcium regulation through Sanger sequencing for mutation accuracy, qRT-PCR for mRNA stability, immunofluorescence for subcellular localization, Western blotting for protein level, Fura-2 imaging for intracellular calcium, and proliferation analysis for cell function. The validation experiments showed that those variants in CCR5 and C3AR1 significantly increased the rise of intracellular calcium and the variant in CCR5 profoundly enhanced proliferative capacity of human pulmonary artery smooth muscle cells. Thus, our study suggests that multiple genetically affected signaling pathways take effect together to cause the formation of IPAH and the development of right heart failure and may further provide new therapy targets or putative clues for the present treatments such as limited therapeutic effectiveness of Ca2+ channel blockers.

Gender differences in pulmonary arterial hypertension patients with BMPR2 mutation: a meta-analysis

ObjectiveTo investigate the differences in the proportions of BMPR2 mutations in familial hereditary pulmonary arterial hypertension (HPAH) and idiopathic pulmonary arterial hypertension (IPAH) between males and females and the relationship between BMPR2 mutation and PAH severity.MethodsA computer was used to search the electronic Cochrane Library, PubMed/MEDLINE, and EMBASE databases for clinical trials containing information on the relationship between PAH prognosis and BMPR2 mutations through March 2019. After obtaining the data, a meta-analysis was performed using Review Manager Version 5.3 and Stata.ResultsA meta-analysis was performed on 17 clinical trials (2198 total patients: 644 male, 1554 female). The results showed that among patients with HPAH and IPAH, the BMPR2 mutation rate is higher in male than in female patients [male group (224/644, 34.78%), female group (457/1554, 29.41%), OR = 1.30, 95% CI: 1.06~1.60, P = 0.01, I2 = 10%]. Furthermore, haemodynamic and functional parameters were more severe in IPAH and HPAH patients with BMPR2 mutations than in those without, and those with BMPR2 mutation were diagnosed at a younger age. The risk of death or transplantation was higher in PAH patients with BMPR2 mutations than in those without (OR = 2.51, 95% CI: 1.29~3.57, P = 0.003, I2 = 24%). Furthermore, the difference was significant only in male patients (OR = 5.58, 95% CI: 2.16~14.39, P = 0.0004, I2 = 0%) and not in female patients (OR = 1.41, 95% CI: 0.75~2.67, P = 0.29, I2 = 0%).ConclusionAmong patients with HPAH and IPAH, men are more likely to have BMPR2 mutations, which may predict more severe PAH indications and prognosis.

Familial pulmonary arterial hypertension by KDR heterozygous loss of function.

Beyond the major gene BMPR2, several new genes predisposing to PAH have been identified during the last decade. Recently, preliminary evidence of the involvement of the KDR gene was found in a large genetic association study.We prospectively analysed the KDR gene by targeted panel sequencing in a series of 311 PAH patients referred to a clinical molecular laboratory for genetic diagnosis of PAH.Two index cases with severe PAH from two different families were found to carry a loss-of-function mutation in the KDR gene. These two index cases were clinically characterised by low diffusing capacity for carbon monoxide adjusted for haemoglobin (D LCOc) and interstitial lung disease. In one family, segregation analysis revealed that variant carriers are either presenting with PAH associated with low D LCOc, or have only decreased D LCOc, whereas non-carrier relatives have normal D LCOc. In the second family, a single affected carrier was alive. His carrier mother was unaffected with normal D LCOc.We provided genetic evidence for considering KDR as a newly identified PAH-causing gene by describing the segregation of KDR mutations with PAH in two families. In our study, KDR mutations are associated with a particular form of PAH characterised by low D LCOc and radiological evidence of parenchymal lung disease including interstitial lung disease and emphysema.

Autophagy contributes to BMP type 2 receptor degradation anddevelopment of pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is characterised by an increase in mean pulmonary arterial pressure which almost invariably leads to right heart failure and premature death. More than 70% of familial PAH and 20% of idiopathic PAH patients carry heterozygous mutations in the bone morphogenetic protein (BMP) type 2 receptor (BMPR2). However, the incomplete penetrance of BMPR2 mutations suggests that other genetic and environmental factors contribute to the disease. In the current study, we investigate the contribution of autophagy in the degradation of BMPR2 in pulmonary vascular cells. We demonstrate that endogenous BMPR2 is degraded through the lysosome in primary human pulmonary artery endothelial (PAECs) and smooth muscle cells (PASMCs): two cell types that play a key role in the pathology of the disease. By means of an elegant HaloTag system, we show that a block in lysosomal degradation leads to increased levels of BMPR2 at the plasma membrane. In addition, pharmacological or genetic manipulations of autophagy allow us to conclude that autophagy activation contributes to BMPR2 degradation. It has to be further investigated whether the role of autophagy in the degradation of BMPR2 is direct or through the modulation of the endocytic pathway. Interestingly, using an iPSC‐derived endothelial cell model, our findings indicate that BMPR2 heterozygosity alone is sufficient to cause an increased autophagic flux. Besides BMPR2 heterozygosity, pro‐inflammatory cytokines also contribute to an augmented autophagy in lung vascular cells. Furthermore, we demonstrate an increase in microtubule‐associated protein 1 light chain 3 beta (MAP1LC3B) levels in lung sections from PAH induced in rats. Accordingly, pulmonary microvascular endothelial cells (MVECs) from end‐stage idiopathic PAH patients present an elevated autophagic flux. Our findings support a model in which an increased autophagic flux in PAH patients contributes to a greater decrease in BMPR2 levels. Altogether, this study sheds light on the basic mechanisms of BMPR2 degradation and highlights a crucial role for autophagy in PAH. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Molecular genetic framework underlying pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a rare, progressive disorder typified by occlusion of the pulmonary arterioles owing to endothelial dysfunction and uncontrolled proliferation of pulmonary artery smooth muscle cells and fibroblasts. Vascular occlusion can lead to increased pressure in the pulmonary arteries, often resulting in right ventricular failure with shortness of breath and syncope. Since the identification of BMPR2, which encodes a receptor in the transforming growth factor-β superfamily, the development of high-throughput sequencing approaches to identify novel causal genes has substantially advanced our understanding of the molecular genetics of PAH. In the past 6 years, additional pathways involved in PAH susceptibility have been described through the identification of deleterious genetic variants in potassium channels (KCNK3 and ABCC8) and transcription factors (TBX4 and SOX17), among others. Although familial PAH most often has an autosomal-dominant pattern of inheritance, cases of incomplete penetrance and evidence of genetic heterogeneity support a model of PAH as a Mendelian disorder with complex disease features. In this Review, we outline the latest advances in the detection of rare and common genetic variants underlying PAH susceptibility and disease progression. These findings have clinical implications for lung vascular function and can help to identify mechanistic pathways amenable to pharmacological intervention.

A Combined Targeted and Whole Exome Sequencing Approach Identified Novel Candidate Genes Involved in Heritable Pulmonary Arterial Hypertension

The pathogenesis of idiopathic and heritable forms of pulmonary arterial hypertension is still not completely understood, even though several causative genes have been proposed, so that a third of patients remains genetically unresolved. Here we applied a multistep approach to extend identification of the genetic bases of such a disease by searching for novel candidate genes/pathways. Twenty-eight patients belonging to 18 families were screened for BMPR2 mutations and BMPR2-negative samples were tested for 12 additional candidate genes by means of a specific massive parallel sequencing-based assay. Finally, whole exome sequencing was performed on four patients showing no mutations at known disease genes, as well as on their unaffected parents. In addition to EIF2AK4, which has been already suggested to be associated with pulmonary veno-occlusive disease, we identified the novel candidate genes ATP13A3, CD248, EFCAB4B, involved in lung vascular remodeling that represent reliable drivers contributing to the disease according to their biological functions/inheritance patterns. Therefore, our results suggest that combining gene panel and whole exome sequencing provides new insights useful for the genetic diagnosis of familial and idiopathic pulmonary arterial hypertension, as well as for the identification of biological pathways that will be potentially targeted by new therapeutic strategies.

FHIT, a Novel Modifier Gene in Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is characterized by progressive narrowing of pulmonary arteries, resulting in right heart failure and death. BMPR2 (bone morphogenetic protein receptor type 2) mutations account for most familial PAH forms whereas reduced BMPR2 is present in many idiopathic PAH forms, suggesting dysfunctional BMPR2 signaling to be a key feature of PAH. Modulating BMPR2 signaling is therapeutically promising, yet how BMPR2 is downregulated in PAH is unclear. We intended to identify and pharmaceutically target BMPR2 modifier genes to improve PAH. We combined siRNA high-throughput screening of >20,000 genes with a multicohort analysis of publicly available PAH RNA expression data to identify clinically relevant BMPR2 modifiers. After confirming gene dysregulation in tissue from patients with PAH, we determined the functional roles of BMPR2 modifiers in vitro and tested the repurposed drug enzastaurin for its propensity to improve experimental pulmonary hypertension (PH). We discovered FHIT (fragile histidine triad) as a novel BMPR2 modifier. BMPR2 and FHIT expression were reduced in patients with PAH. FHIT reductions were associated with endothelial and smooth muscle cell dysfunction, rescued by enzastaurin through a dual mechanism: upregulation of FHIT as well as miR17-5 repression. Fhit-/- mice had exaggerated hypoxic PH and failed to recover in normoxia. Enzastaurin reversed PH in the Sugen5416/hypoxia/normoxia rat model, by improving right ventricular systolic pressure, right ventricular hypertrophy, cardiac fibrosis, and vascular remodeling. This study highlights the importance of the novel BMPR2 modifier FHIT in PH and the clinical value of the repurposed drug enzastaurin as a potential novel therapeutic strategy to improve PAH.

Widening the landscape of heritable pulmonary hypertension mutations in paediatric and adult cases.

Heritable forms of pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease/pulmonary capillary haemangiomatosis (PVOD/PCH) diverge by lung histopathological lesions, clinical and para-clinical presentation, their responsible genes, and mode of transmission. Since the identification of the BMPR2 gene in families affected by PAH, mutations in several other genes have been discovered for both forms. The mutation landscape in these new genes is not yet well known. We set up a next-generation sequencing-based targeted sequencing gene panel allowing known genes for PAH and PVOD/PCH to be analysed simultaneously. Genetic analysis was prospectively performed on 263 PAH and PVOD/PCH patients (adult and paediatric cases). Pathogenic mutations were identified in 19.5% of sporadic PAH patients (n=180), 54.5% of familial PAH patients and 13.3% of PVOD/PCH patients. BMPR2 was the most frequently mutated gene, followed by TBX4 in both paediatric and adult PAH. BMP9 mutations were identified in 1.2% of adult PAH cases. EIF2AK4 biallelic mutations were restricted to PVOD/PCH. A truncating mutation and a predicted loss-of-function variant were also identified in BMP10 in two severely affected sporadic PAH female patients. Our results confirm that mutations are found in genes beyond BMPR2 in heritable PAH, emphasise the role of TBX4 and BMP9, and designate BMP10 as a new PAH gene.

LONG-TERM CLINICAL OUTCOMES IN A SERIES OF PATIENTS TRANSITIONED FROM INFUSED OR INHALED TREPROSTINIL TO ORAL TREPROSTINIL

SESSION TITLE: Pulmonary Vascular Disease 2 SESSION TYPE: Original Investigation Posters PRESENTED ON: 10/10/2018 01:00 PM - 02:00 PM PURPOSE: To evaluate the clinical impact of long term treatment with oral treprostinil in patients with pulmonary arterial hypertension (PAH) transitioned from infused or inhaled treprostinil. METHODS: Medical records of 4 patients with PAH treated long term with oral treprostinil after transition from infused or inhaled treprostinil maintenance therapy were examined. WHO Group I or IV pulmonary hypertension was confirmed based on standard diagnostic guidelines. Data extracted included demographics, changes in functional capacity, clinical worsening events and echocardiogram parameters of right heart function. The impact of side effects on compliance and treatment effect were included in the analysis. RESULTS: All patients were male aged 43 to 71 at the time of conversion to oral treprostinil. Two patients had idiopathic PAH, 1 familial PAH and 1 chronic thromboembolic pulmonary hypertension. Two patients transitioned from long term infused treprostinil (> 40 months) and concurrent tadalafil. Two patients transitioned from long term inhaled treprostinil (> 19 months) and concurrent phosphodiesterase 5 inhibitor or soluble guanylate cyclase stimulator. Oral treprostinil continued in combination with other PAH therapies in all cases. Duration of exposure to oral treprostinil ranged from 16 to 34 months. There was no therapy escalation due to clinical worsening. Two patients were hospitalized during the period of interest; none were for PAH related reasons. 6 minute walk distance was maintained or improved in 3 patients; transient decrease in 6 minute walk distance in 1 patient was related to temporary noncompliance. WHO functional class was maintained or improved in all patients. Improvement in right ventricular size or function were noted by echocardiography in 3 patients, while the fourth patient maintained right ventricular function without change. Serial data reflecting changes in functional capacity and echocardiographic features of PAH suggested patients transitioning from inhaled therapy may have experienced more beneficial impact. Three patients had significant gastrointestinal side effects that affected compliance or dose titration. CONCLUSIONS: Patients transitioned from infused or inhaled forms of treprostinil were able to maintain long term functional capacity and in some cases experienced further improvement in function and echocardiographic changes associated with PAH. A synergistic dependence on concurrent PAH therapies cannot be excluded. Long term use of oral treprostinil is associated with significant side effects which may affect compliance or dose titration. CLINICAL IMPLICATIONS: There is little known or reported about the effects of long term treatment with oral treprostinil. This report supports the long term use of oral treprostinil in PAH treatment regimens to maintain or improve functional capacity and prevent clinical worsening. DISCLOSURES: No relevant relationships by Regina Overton-Barnes, source=Web Response Speaker/Speaker's Bureau relationship with United Therapeutics Please note: $5001 - $20000 Added 03/02/2018 by John Swisher, source=Web Response, value=Honoraria Clinical trial participant relationship with United Therapeutics Please note: $1-$1000 Added 03/02/2018 by John Swisher, source=Web Response, value=Grant/Research Speaker/Speaker's Bureau relationship with Actelion Pharmaceuticals Please note: $5001 - $20000 Added 03/02/2018 by John Swisher, source=Web Response, value=Honoraria Speaker/Speaker's Bureau relationship with Gilead Please note: $5001 - $20000 Added 03/02/2018 by John Swisher, source=Web Response, value=Honoraria No relevant relationships by Eric Weaver, source=Web Response

Consequences of BMPR2 Deficiency in the Pulmonary Vasculature and Beyond: Contributions to Pulmonary Arterial Hypertension.

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

Recent advances in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a rare disorder with a high mortality rate. Treatment options have improved in the last 20 years, but patients still die prematurely of right heart failure. Though rare, it is heterogeneous at the genetic and molecular level, and understanding and exploiting this is key to the development of more effective treatments. BMPR2, encoding bone morphogenetic receptor type 2, is the most commonly affected gene in both familial and non-familial PAH, but rare mutations have been identified in other genes. Transcriptomic, proteomic, and metabolomic studies looking for endophenotypes are under way. There is no shortage of candidate new drug targets for PAH, but the selection and prioritisation of these are challenges for the research community.

Rare variants in SOX17 are associated with pulmonary arterial hypertension with congenital heart disease

BackgroundPulmonary arterial hypertension (PAH) is a rare disease characterized by distinctive changes in pulmonary arterioles that lead to progressive pulmonary arterial pressures, right-sided heart failure, and a high mortality rate. Up to 30% of adult and 75% of pediatric PAH cases are associated with congenital heart disease (PAH-CHD), and the underlying etiology is largely unknown. There are no known major risk genes for PAH-CHD.MethodsTo identify novel genetic causes of PAH-CHD, we performed whole exome sequencing in 256 PAH-CHD patients. We performed a case-control gene-based association test of rare deleterious variants using 7509 gnomAD whole genome sequencing population controls. We then screened a separate cohort of 413 idiopathic and familial PAH patients without CHD for rare deleterious variants in the top association gene.ResultsWe identified SOX17 as a novel candidate risk gene (p = 5.5e−7). SOX17 is highly constrained and encodes a transcription factor involved in Wnt/β-catenin and Notch signaling during development. We estimate that rare deleterious variants contribute to approximately 3.2% of PAH-CHD cases. The coding variants identified include likely gene-disrupting (LGD) and deleterious missense, with most of the missense variants occurring in a highly conserved HMG-box protein domain. We further observed an enrichment of rare deleterious variants in putative targets of SOX17, many of which are highly expressed in developing heart and pulmonary vasculature. In the cohort of PAH without CHD, rare deleterious variants of SOX17 were observed in 0.7% of cases.ConclusionsThese data strongly implicate SOX17 as a new risk gene contributing to PAH-CHD as well as idiopathic/familial PAH. Replication in other PAH cohorts and further characterization of the clinical phenotype will be important to confirm the precise role of SOX17 and better estimate the contribution of genes regulated by SOX17.

Exome Sequencing in Children With Pulmonary Arterial Hypertension Demonstrates Differences Compared With Adults

Pulmonary arterial hypertension (PAH) is a rare disease characterized by pulmonary arteriole remodeling, elevated arterial pressure and resistance, and subsequent heart failure. Compared with adult-onset disease, pediatric-onset PAH is more heterogeneous and often associated with worse prognosis. Although BMPR2 mutations underlie ≈70% of adult familial PAH (FPAH) cases, the genetic basis of PAH in children is less understood. We performed genetic analysis of 155 pediatric- and 257 adult-onset PAH patients, including both FPAH and sporadic, idiopathic PAH (IPAH). After screening for 2 common PAH risk genes, mutation-negative FPAH and all IPAH cases were evaluated by exome sequencing. We observed similar frequencies of rare, deleterious BMPR2 mutations in pediatric- and adult-onset patients: ≈55% in FPAH and 10% in IPAH patients in both age groups. However, there was significant enrichment of TBX4 mutations in pediatric- compared with adult-onset patients (IPAH: 10/130 pediatric versus 0/178 adult-onset), and TBX4 carriers had younger mean age-of-onset compared with BMPR2 carriers. Mutations in other known PAH risk genes were infrequent in both age groups. Notably, among pediatric IPAH patients without mutations in known risk genes, exome sequencing revealed a 2-fold enrichment of de novo likely gene-damaging and predicted deleterious missense variants. Mutations in known PAH risk genes accounted for ≈70% to 80% of FPAH in both age groups, 21% of pediatric-onset IPAH, and 11% of adult-onset IPAH. Rare, predicted deleterious variants in TBX4 are enriched in pediatric patients and de novo variants in novel genes may explain ≈19% of pediatric-onset IPAH cases.

Treatment of familial pulmonary arterial hypertension with novel nebulizer (BreelibTM) for iloprost inhalations - first use outside of clinical trials

Treatment of familial pulmonary arterial hypertension with novel nebulizer (BreelibTM) for iloprost inhalations - first use outside of clinical trials