The genetic basis of pulmonary arterial hypertension

Serum endostatin is a genetically determined predictor of survival in pulmonary arterial hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is a medically incurable disease resulting in death from right ventricular (RV) failure. Both pulmonary vascular and RV remodeling are linked to dynamic changes in the microvasculature. Therefore, we hypothesized that circulating angiostatic factors could be linked to outcomes and represent novel biomarkers of disease severity in PAH.

OBJECTIVES

We sought to determine the relationship of a potent angiostatic factor, endostatin (ES), with disease severity and mortality in PAH. Furthermore, we assessed genetic predictors of ES expression and/or function and their association with outcomes in PAH.

METHODS

We measured levels of serum ES in two independent cohorts of patients with PAH. Contemporaneous clinical data included New York Heart Association functional class, 6-minute-walk distance, invasive hemodynamics, and laboratory chemistries.

MEASUREMENTS AND MAIN RESULTS

Serum ES correlated with poor functional status, decreased exercise tolerance, and invasive hemodynamics variables. Furthermore, serum ES was a strong predictor of mortality. A loss-of-function, missense variant in the gene encoding ES, Col18a1, was linked to lower circulating protein and was independently associated with reduced mortality.

CONCLUSIONS

Our data link increased expression of ES to disease severity in PAH and demonstrate a significant relationship with adverse outcomes. Circulating ES levels can be genetically influenced, implicating ES as a genetically determined modifier of disease severity impacting on survival. These observations support serum ES as a potential biomarker in PAH with the capacity to predict poor outcomes. More importantly, this study implicates Col18a1/ES as a potential new therapeutic target in PAH.

Diffuse lung disease of infancy: a pattern-based, algorithmic approach to histological diagnosis

Diffuse lung disease (DLD) of infancy has multiple aetiologies and the spectrum of disease is substantially different from that seen in older children and adults. In many cases, a specific diagnosis renders a dire prognosis for the infant, with profound management implications. Two recently published series of DLD of infancy, collated from the archives of specialist centres, indicate that the majority of their cases were referred, implying that the majority of biopsies taken for DLD of infancy are first received by less experienced pathologists. The current literature describing DLD of infancy takes a predominantly aetiological approach to classification. We present an algorithmic, histological, pattern-based approach to diagnosis of DLD of infancy, which, with the aid of appropriate multidisciplinary input, including clinical and radiological expertise and ancillary diagnostic studies, may lead to an accurate and useful interim report, with timely exclusion of inappropriate diagnoses. Subsequent referral to a specialist centre for confirmatory diagnosis will be dependent on the individual case and the decision of the multidisciplinary team.

Pulmonary vascular development goes awry in congenital lung abnormalities

Pulmonary vascular diseases of the newborn comprise a wide range of pathological conditions with developmental abnormalities in the pulmonary vasculature. Clinically, pulmonary arterial hypertension (PH) is characterized by persistent increased resistance of the vasculature and abnormal vascular response. The classification of PH is primarily based on clinical parameters instead of morphology and distinguishes five groups of PH. Congenital lung anomalies, such as alveolar capillary dysplasia (ACD) and PH associated with congenital diaphragmatic hernia (CDH), but also bronchopulmonary dysplasia (BPD), are classified in group three. Clearly, tight and correct regulation of pulmonary vascular development is crucial for normal lung development. Human and animal model systems have increased our knowledge and make it possible to identify and characterize affected pathways and study pivotal genes. Understanding of the normal development of the pulmonary vasculature will give new insights in the origin of the spectrum of rare diseases, such as CDH, ACD, and BPD, which render a significant clinical problem in neonatal intensive care units around the world. In this review, we describe normal pulmonary vascular development, and focus on four diseases of the newborn in which abnormal pulmonary vascular development play a critical role in morbidity and mortality. In the future perspective, we indicate the lines of research that seem to be very promising for elucidating the molecular pathways involved in the origin of congenital pulmonary vascular disease.

The role of BMPs in endothelial cell function and dysfunction

The bone morphogenetic protein (BMP) family of proteins has a multitude of roles throughout the body. In embryonic development, BMPs promote endothelial specification and subsequent venous differentiation. The BMP pathway also plays important roles in the adult vascular endothelium, promoting angiogenesis and mediating shear and oxidative stress. The canonical BMP pathway functions through the Smad transcription factors; however, other intracellular signaling cascades can be activated, and receptor complexes beyond the traditional type I and type II receptors add additional layers of regulation. Dysregulated BMP signaling has been linked to vascular diseases including pulmonary hypertension and atherosclerosis. This review addresses recent advances in the roles of BMP signaling in the endothelium and how BMPs affect endothelial dysfunction and human disease.

Functional prostacyclin synthase promoter polymorphisms. Impact in pulmonary arterial hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by elevated pulmonary artery pressure, vascular remodeling, and ultimately right ventricular heart failure. PAH can have a genetic component (heritable PAH), most often through mutations of bone morphogenetic protein receptor 2, and idiopathic and associated forms. Heritable PAH is not completely penetrant within families, with approximately 20% concurrence of inactivating bone morphogenetic protein receptor 2 mutations and delayed onset of PAH disease. Because one of the treatment options is using prostacyclin analogs, we hypothesized that prostacyclin synthase promoter sequence variants associated with increased mRNA expression may play a protective role in the bone morphogenetic protein receptor 2 unaffected carriers.

OBJECTIVES

To characterize the range of prostacyclin synthase promoter variants and assess their transcriptional activities in PAH-relevant cell types. To determine the distribution of prostacyclin synthase promoter variants in PAH, unaffected carriers in heritable PAH families, and control populations.

METHODS

Polymerase chain reaction approaches were used to genotype prostacyclin synthase promoter variants in more than 300 individuals. Prostacyclin synthase promoter haplotypes' transcriptional activities were determined with luciferase reporter assays.

MEASUREMENTS AND MAIN RESULTS

We identified a comprehensive set of prostacyclin synthase promoter variants and tested their transcriptional activities in PAH-relevant cell types. We demonstrated differences of prostacyclin synthase promoter activities dependent on their haplotype.

CONCLUSIONS

Prostacyclin synthase promoter sequence variants exhibit a range of transcriptional activities. We discovered a significant bias for more active prostacyclin synthase promoter variants in unaffected carriers as compared with affected patients with PAH.