[Physiopathology of pulmonary arterial hypertension. Cellular and molecular aspects]

Therapeutic Evaluation of Antibody-Based Targeted Delivery of Interleukin 9 in Experimental Pulmonary Hypertension

Background and Aims: Pulmonary hypertension (PH) is a heterogeneous disorder associated with poor prognosis. For the majority of patients, only limited therapeutic options are available. Thus, there is great interest to develop novel treatment strategies focusing on pulmonary vascular and right ventricular remodeling. Interleukin 9 (IL9) is a pleiotropic cytokine with pro- and anti-inflammatory functions. The aim of this study was to evaluate the therapeutic activity of F8IL9F8 consisting of IL9 fused to the F8 antibody, specific to the alternatively-spliced EDA domain of fibronectin, which is abundantly expressed in pulmonary vasculature and right ventricular myocardium in PH. Methods: The efficacy of F8IL9F8 in attenuating PH progression in the monocrotaline mouse model was evaluated in comparison to an endothelin receptor antagonist (ERA) or an IL9 based immunocytokine with irrelevant antibody specificity (KSFIL9KSF). Treatment effects were assessed by right heart catheterization, echocardiography as well as histological and immunohistochemical tissue analyses. Results: Compared to controls, systolic right ventricular pressure (RVPsys) was significantly elevated and a variety of right ventricular echocardiographic parameters were significantly impaired in all MCT-induced PH groups except for the F8IL9F8 group. Both, F8IL9F8 and ERA treatments lead to a significant reduction in RVPsys and an improvement of echocardiographic parameters when compared to the MCT group not observable for the KSFIL9KSF group. Only F8IL9F8 significantly reduced lung tissue damage and displayed a significant decrease of leukocyte and macrophage accumulation in the lungs and right ventricles. Conclusions: Our study provides first pre-clinical evidence for the use of F8IL9F8 as a new therapeutic agent for PH in terms of a disease-modifying concept addressing cardiovascular remodeling.

Lumped-Parameter Circuit Platform for Simulating Typical Cases of Pulmonary Hypertensions from Point of Hemodynamics

Pulmonary hypertension (PH) presents unusual hemodynamic states characterized by abnormal high blood pressure in pulmonary artery. The objective of this study is to simulate how the hemodynamics develops in typical PH cases without treatment. A lumped-parameter circuit platform of human circulation system is set up to simulate hemodynamic abnormalities of PH in different etiologies and pathogenesis. Four typical cases are considered, which are distal pulmonary artery stenosis, left ventricular diastolic dysfunction, ventricular septal defect, and mitral stenosis. The authors propose regulation laws for chambers and vessels to adapt the abnormal hemodynamic conditions for each PH case. The occurrence and development of each PH case are simulated over time using the lumped-parameter circuit platform. The blood pressure, blood flow, pressure-volume relations for chambers and vessels are numerically calculated for each case of PH progression. The model results could be a quite helpful to understand the hemodynamic mechanism of typical PHs. Graphical Abstract.

Lung tissue remodelling in MCT-induced pulmonary hypertension: a proposal for a novel scoring system and changes in extracellular matrix and fibrosis associated gene expression

Pulmonary hypertension (PH) is associated with vasoconstriction and remodelling. We studied lung tissue remodelling in a rat model of PH with special focus on histology and extracellular matrix (ECM) remodelling. After induction of PH by monocrotaline, lung tissue was analysed histologically, by gene expression analysis and immunofluorescence labelling of ED-A domain containing fibronectin (ED-A+ Fn), B domain containing tenascin-C (B+ Tn-C) as well as alpha-smooth muscle actin (α-SMA). Serum concentrations of ED-A+ Fn were determined by ELISA. Systolic right ventricular pressure (RVPsys) values were significantly elevated in PH (n = 18; 75 ± 26.4 mmHg) compared to controls (n = 10; 29 ± 19.3 mmHg; p = 0.015). The histological sum-score was significantly increased in PH (8.0 ± 2.2) compared to controls (2.5 ± 1.6; p < 0.001). Gene expression analysis revealed relevant induction of several key genes of extracellular matrix remodelling. Increased protein deposition of ED-A+ Fn but not of B+ Tn-C and α-SMA in lung tissue was found in PH (2.88 ± 3.19 area%) compared to controls (1.32 ± 0.16 area%; p = 0.030). Serum levels of ED-A+ Fn were significantly higher in PH (p = 0.007) positively correlating with RVPsys (r = 0.618, p = 0.019). We here present a novel histological scoring system to assess lung tissue remodelling in PH. Gene expression analysis revealed induction of candidate genes involved in collagen matrix turnover, fibrosis and vascular remodelling. The stable increased tissue deposition of ED-A+ Fn in PH as well as its dynamics in serum suggests a role as a promising novel biomarker and potential therapeutic target.

A novel murine model of severe pulmonary arterial hypertension

RATIONALE

The complex pathologies associated with severe pulmonary arterial hypertension (PAH) in humans have been a challenge to reproduce in mice due to the subtle phenotype displayed to PAH stimuli.

OBJECTIVES

Here we aim to develop a novel murine model of PAH that recapitulates more of the pathologic processes, such as complex vascular remodeling and cardiac indices, that are not characteristic of alternative mouse models.

METHODS

Inhibition of vascular endothelial growth factor receptor (VEGFR) with SU5416 combined with 3 weeks of chronic hypoxia was investigated. Hemodynamics, cardiac function, histological assessment of pulmonary vasculature, and molecular pathway analysis gauged the extent of PAH pathology development.

MEASUREMENTS AND MAIN RESULTS

The combination of VEGFR inhibition with chronic hypoxia profoundly exacerbated all measures of PAH-like pathology when compared with hypoxia alone (> 45 mm Hg right ventricular pressure, > 0.35 right ventricular hypertrophy). The changes in pulmonary vascular remodeling in response to hypoxia were further enhanced on SU5416 treatment. Furthermore, hypoxia/SU5416 treatment steadily decreased cardiac output, indicating incipient heart failure. Molecular analysis showed a dysregulated transforming growth factor-β/bone morphogenetic protein/Smad axis in SU5416- and/or hypoxia-treated mice as well as augmented induction of IL-6 and Hif-1α levels. These changes were observed in accordance with up-regulation of Tph1 and Pdgfr gene transcripts as well as a rise in platelet-rich serotonin. Biomarker analysis in response to VEGFR inhibition and/or hypoxia revealed distinct signatures that correlate with cytokine profiles of patients with idiopathic PAH.

CONCLUSIONS

These data describe a novel murine model of PAH, which displays many of the hallmarks of the human disease, thus opening new avenues of investigation to better understand PAH pathophysiology.