Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary artery pressure and vascular resistance, typically leading to right heart failure and death. Current therapies improve quality of life of the patients but have a modest effect on long-term survival. A detailed transcriptomics and systems biology view of the PAH lung is expected to provide new testable hypotheses for exploring novel treatments. We completed transcriptomics analysis of PAH and control lung tissue to develop disease-specific and clinical data/tissue pathology gene expression classifiers from expression datasets. Gene expression data were integrated into pathway analyses. Gene expression microarray data were collected from 58 PAH and 25 control lung tissues. The strength of the dataset and its derived disease classifier was validated using multiple approaches. Pathways and upstream regulators analyses was completed with standard and novel graphical approaches. The PAH lung dataset identified expression patterns specific to PAH subtypes, clinical parameters, and lung pathology variables. Pathway analyses indicate the important global role of TNF and transforming growth factor signaling pathways. In addition, novel upstream regulators and insight into the cellular and innate immune responses driving PAH were identified. Finally, WNT-signaling pathways may be a major determinant underlying the observed sex differences in PAH. This study provides a transcriptional framework for the PAH-diseased lung, supported by previously reported findings, and will be a valuable resource to the PAH research community. Our investigation revealed novel potential targets and pathways amenable to further study in a variety of experimental systems.

Unlabelled

Blood transcriptional signatures are promising for tuberculosis (TB) diagnosis but have not been evaluated among U.S.

Patients

To be used clinically, transcriptional classifiers need reproducible accuracy in diverse populations that vary in genetic composition, disease spectrum and severity, and comorbidities. In a prospective case-control study, we identified novel transcriptional classifiers for active TB among U.S. patients and systematically compared their accuracy to classifiers from published studies. Blood samples from HIV-uninfected U.S. adults with active TB, pneumonia, or latent TB infection underwent whole-transcriptome microarray. We used support vector machines to classify disease state based on transcriptional patterns. We externally validated our classifiers using data from sub-Saharan African cohorts and evaluated previously published transcriptional classifiers in our population. Our classifier distinguishing active TB from pneumonia had an area under the concentration-time curve (AUC) of 96.5% (95.4% to 97.6%) among U.S. patients, but the AUC was lower (90.6% [89.6% to 91.7%]) in HIV-uninfected Sub-Saharan Africans. Previously published comparable classifiers had AUC values of 90.0% (87.7% to 92.3%) and 82.9% (80.8% to 85.1%) when tested in U.S.

Patients

Our classifier distinguishing active TB from latent TB had AUC values of 95.9% (95.2% to 96.6%) among U.S. patients and 95.3% (94.7% to 96.0%) among Sub-Saharan Africans. Previously published comparable classifiers had AUC values of 98.0% (97.4% to 98.7%) and 94.8% (92.9% to 96.8%) when tested in U.S.

Patients

Blood transcriptional classifiers accurately detected active TB among U.S. adults. The accuracy of classifiers for active TB versus that of other diseases decreased when tested in new populations with different disease controls, suggesting additional studies are required to enhance generalizability. Classifiers that distinguish active TB from latent TB are accurate and generalizable across populations and can be explored as screening assays.

Using RNAseq, we identified a 61 gene-based circulating transcriptomic profile most correlated with four indices of pulmonary arterial hypertension severity. In an independent dataset, 13/61 (21%) genes were differentially expressed in lung tissues of pulmonary arterial hypertension cases versus controls, highlighting potentially novel candidate genes involved in pulmonary arterial hypertension development.

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.