4D flow cardiac MRI to assess pulmonary blood flow in patients with pulmonary arterial hypertension associated with congenital heart disease.

PURPOSE: The purpose of this study was to evaluate the accuracy of four-dimensional flow cardiac magnetic resonance imaging (4D flow MRI) compared to right heart catheterization in measuring pulmonary flow (Qp), systemic flow (Qs) and pulmonary-to-systemic flow ratio (Qp/Qs) in patients with pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD). MATERIALS AND METHODS: The study was registered on Clinical-trial.gov (NCT03928002). Sixty-four patients with PAH-CHD who underwent 4D flow MRI were included. There were 16 men and 48 women with a mean age of 45.3 ± 13.7 (standard deviation [SD]) years (age range: 21-77 years). Fifty patients (50/64; 78%) presented with pre-tricuspid shunt. Qp (L/min), Qs (L/min) and Qp/Qs were measured invasively using direct Fick method during right heart catheterization and compared with measurements assessed by 4D flow MRI within a 24-48-hour window. RESULTS: The average mean pulmonary artery pressure was 51 ± 17 (SD) mm Hg with median pulmonary vascular resistance of 8.8 Wood units (Q1, Q3: 5.3, 11.7). A strong linear correlation was found between Qp measurements obtained with 4D flow MRI and those obtained with the Fick method (r = 0.96; P < 0.001). Bland Altman analysis indicated a mean difference of 0.15 ± 0.48 (SD) L/min between Qp estimated by 4D flow MRI and by right heart catheterization. A strong correlation was found between Qs and Qp/Qs measured by 4D flow MRI and those obtained with the direct Fick method (r = 0.85 and r = 0.92; P < 0.001 for both). CONCLUSION: Qp as measured by 4D flow MRI shows a strong correlation with measurements derived from the direct Fick method. Further investigation is needed to develop less complex and standardized methods for measuring essential PAH parameters, such as pulmonary arterial pressures and pulmonary vascular resistance.

A Modified Technique for Transcatheter Pulmonary Valve Implantation of SAPIEN 3 Valves in Large Right Ventricular Outflow Tract: A Matched Comparison Study.

INTRODUCTION: Percutaneous pulmonary valve implantation (PPVI) with a SAPIEN 3 valve is effective for treating treat right ventricle outflow (RVOT) dysfunction. A modified technique was developed without prestenting using a protective valve delivery method. We aimed to compare the procedural results of the modified technique group (MTG) to those of patients in a conventional technique group (CTG). METHODS: We designed a matched before-after study. All consecutive PPVI with SAPIEN 3 performed in the MTG over 9 months were matched, based on the RVOT type and size, to consecutive procedures performed previously with SAPIEN 3. RESULTS: A total of 54 patients were included, equally distributed in the two groups. The sizes of the SAPIEN 3 valves were 23 mm (n = 9), 26 mm (n = 9), 29 mm (n = 36). The two groups were similar regarding demographic data, RVOT type, and pre-procedure hemodynamics. PPVI was performed in a single procedure in all patients of the MTG, whereas six (22.2%) patients of the CTG group underwent prestenting as a first step and valve implantation later (p = 0.02). The procedures were successful in all cases. Stent embolization was reported in two patients (7.4%) in the CTG, which were impacted in pulmonary arteries. In one case (3.7%), in the MTG, an unstable 29 mm SAPIEN 3 valve was stabilized with two stents and additional valve-in-valve implantation. The hemodynamics results were good in all cases, without significant differences between the two groups. The procedures' durations and fluoroscopy times were significantly reduced in the MTG (48.1 versus 82.6 min, p < 0.0001; 15.2 versus 29.8 min, p = 0.0002). During follow-up, neither stent fracture nor valve dysfunction was noticed in either group. CONCLUSION: PPVI without prestenting and with a protective delivery method of the SAPIEN 3 valve significantly reduces the procedure's complexity, the duration, and the irradiation while maintaining excellent hemodynamics results in selected cases.

Long-term outcomes of transcatheter pulmonary valve implantation with melody and SAPIEN valves.

BACKGROUND: Transcatheter pulmonary valve implantation (TPVI) is effective for treating right ventricle outflow tract (RVOT) dysfunction. Factors associated with long-term valve durability remain to be investigated. METHODS: Consecutive patients successfully treated by TPVI with Melody valves (n = 32) and SAPIEN valves (n = 182) between 2008 and 2020 at a single tertiary centre were included prospectively and monitored. RESULTS: The 214 patients had a median age of 28 years (range, 10-81). The RVOT was a patched native pulmonary artery in 96 (44.8%) patients. Median follow-up was 2.8 years (range, 3 months-11.4 years). Secondary pulmonary valve replacement (sPVR) was performed in 23 cases (10.7%), due to stenosis (n = 22, 95.7%) or severe regurgitation (n = 1, 4.3%), yielding an incidence of 7.6/100 patient-years with melody valves and 1.3/100 patient-years with SAPIEN valves (P = 0.06). The 5- and 10-year sPVR-freedom rates were 78.1% and 50.4% with Melody vs. 94.3% and 82.2% with SAPIEN, respectively (P = 0.06). The incidence of infective endocarditis (IE) was 5.5/100 patient-years with Melody and 0.2/100 patient-years with SAPIEN (P < 0.0001). Factors associated with sPVR by univariate analysis were RV obstruction before TPVI (P = 0.04), transpulmonary maximal velocity > 2.7 m/s after TPVI (p = 0.0005), valve diameter ≤ 22 mm (P < 0.003), IE (P < 0.0001), and age < 25 years at TPVI (P = 0.04). By multivariate analysis adjusted for IE occurrence, transpulmonary maximal velocity remained associated with sPVR. CONCLUSIONS: TPVI is effective for treating RVOT dysfunction. Incidence of sPVR is higher in patients with residual RV obstruction or IE. IE add a substantial risk of TPVI graft failure and is mainly linked to the Melody valve. SOCIAL MEDIA ABSTRACT: Transcatheter pulmonary valve implantation is effective for treating right ventricular outflow tract dysfunction in patients with congenital heart diseases. Incidence of secondary valve replacement is higher in patients with residual obstruction or infective endocarditis.

Electric toy car to reduce anxiety before a cardiac catherisation: randomised controlled trial.

BACKGROUND: Anxiety before an invasive intervention is associated in children with persistent psychological disorders. We studied the effect of the transfer to the catheterisation room by an electric toy car on the anxiety of children and their parents before a cardiac catheterisation. METHODS: Forty-eight children with a median age of 5.6 years [4.2-7.0] were randomised to either riding on an electric car to go to the catheterisation laboratory or being transported lying supine on a gurney. Anxiety assessments were performed by a physician blinded to group allocation on the day before the procedure (T0) and at anaesthesia induction (T1). The modified Yale Preoperative Anxiety Scale Short Form (mYPAS-SF) and visual analogue scale for anxiety (VAS-A) were used in the children and the VAS-A in the parents. RESULTS: The mYPAS-SF, VAS-A-child, and the VAS-A-parent scores were significantly higher at T1 than at T0 (p < 0.001, p < 0.001, and p = 0.005, respectively). The primary outcome (the median mYPAS-SF score at T1) was not significantly different in the two groups when males and females were combined. At T1, the VAS-A-child score, however, was significantly lower in the intervention than the control group (22 versus 55, p < 0.001). In the boys, the median mYPAS-SF score at T1 was significantly lower in the intervention group (25.0 versus 51.0, p = 0.024). No difference was observed in girls. The VAS-A parent score was lower at T1 in the intervention group (60 versus 87, p = 0.05). CONCLUSION: Riding to the catheterisation laboratory on an electric toy car decreased anxiety in boys and decreased parental anxiety.

Retraction notice to ICAM-1 PROMOTES THE ABNORMAL ENDOTHELIAL CELL PHENOTYPE IN CHRONIC THROMBOEMBOLIC PULMONARY HYPERTENSION.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Authors. This request follows an examination by The Editors of the uncut gels provided by the authors, which led the Editors to conclude that data were compromised in the following western blot images: Figure 3C, Figure 5B and Figure 6B. Duplicated data for the beta actin images were found in Figures 5 and 6. Examination of the raw data used for the western blot quantification also revealed frequent duplicated data. The microscopy data in Figure 5A also has features compatible with compromised data although the raw data were not available to the Editors due to the regrettable death of Dr. Saadia Eddahibi. All of the remaining authors agree with the retraction and apologize to the Editors and the readers of The Journal for difficulties this issue has caused.

Targeted proteomics of right heart adaptation to pulmonary arterial hypertension.

No prior proteomic screening study has centred on the right ventricle (RV) in pulmonary arterial hypertension (PAH). This study investigates the circulating proteomic profile associated with right heart maladaptive phenotype (RHMP) in PAH.Plasma proteomic profiling was performed using multiplex immunoassay in 121 (discovery cohort) and 76 (validation cohort) PAH patients. The association between proteomic markers and RHMP, defined by the Mayo right heart score (combining RV strain, New York Heart Association (NYHA) class and N-terminal pro-brain natriuretic peptide (NT-proBNP)) and Stanford score (RV end-systolic remodelling index, NYHA class and NT-proBNP), was assessed by partial least squares regression. Biomarker expression was measured in RV samples from PAH patients and controls, and pulmonary artery banding (PAB) mice.High levels of hepatocyte growth factor (HGF), stem cell growth factor-ß, nerve growth factor and stromal derived factor-1 were associated with worse Mayo and Stanford scores independently from pulmonary resistance or pressure in both cohorts (the validation cohort had more severe disease features: lower cardiac index and higher NT-proBNP). In both cohorts, HGF added value to the REVEAL score in the prediction of death, transplant or hospitalisation at 3 years. RV expression levels of HGF and its receptor c-Met were higher in end-stage PAH patients than controls, and in PAB mice than shams.High plasma HGF levels are associated with RHMP and predictive of 3-year clinical worsening. Both HGF and c-Met RV expression levels are increased in PAH. Assessing plasma HGF levels might identify patients at risk of heart failure who warrant closer follow-up and intensified therapy.

Trichloroethylene increases pulmonary endothelial permeability: implication for pulmonary veno-occlusive disease.

Trichloroethylene exposure is a major risk factor for pulmonary veno-occlusive disease. We demonstrated that trichloroethylene alters the endothelial barrier integrity, at least in part, through vascular endothelial (VE)-Cadherin internalisation, and suggested that this mechanism may play a role in the development of pulmonary veno-occlusive disease.

Comparison of Human and Experimental Pulmonary Veno-Occlusive Disease.

Pulmonary veno-occlusive disease (PVOD) occurs in humans either as a heritable form (hPVOD) due to biallelic inactivating mutations of EIF2AK4 (encoding GCN2) or as a sporadic form in older age (sPVOD). The chemotherapeutic agent mitomycin C (MMC) is a potent inducer of PVOD in humans and in rats (MMC-PVOD). Here, we compared human hPVOD and sPVOD, and MMC-PVOD pathophysiology at the histological, cellular, and molecular levels to unravel common altered pathomechanisms. MMC exposure in rats was associated primarily with arterial and microvessel remodeling, and secondarily by venous remodeling, when PVOD became symptomatic. In all forms of PVOD tested, there was convergent GCN2-dependent but eIF2α-independent pulmonary protein overexpression of HO-1 (heme oxygenase 1) and CHOP (CCAAT-enhancer-binding protein [C/EBP] homologous protein), two downstream effectors of GCN2 signaling and endoplasmic reticulum stress. In human PVOD samples, CHOP immunohistochemical staining mainly labeled endothelial cells in remodeled veins and arteries. Strong HO-1 staining was observed only within capillary hemangiomatosis foci, where intense microvascular proliferation occurs. HO-1 and CHOP stainings were not observed in control and pulmonary arterial hypertension lung tissues, supporting the specificity for CHOP and HO-1 involvement in PVOD pathobiology. In vivo loss of GCN2 (EIF2AK4 mutations carriers and Eif2ak4-/- rats) or in vitro GCN2 inhibition in cultured pulmonary artery endothelial cells using pharmacological and siRNA approaches demonstrated that GCN2 loss of function negatively regulates BMP (bone morphogenetic protein)-dependent SMAD1/5/9 signaling. Exogenous BMP9 was still able to reverse GCN2 inhibition-induced proliferation of pulmonary artery endothelial cells. In conclusion, we identified CHOP and HO-1 inhibition, and BMP9, as potential therapeutic options for PVOD.

ICAM-1 promotes the abnormal endothelial cell phenotype in chronic thromboembolic pulmonary hypertension.

BACKGROUND: Pulmonary endothelial cells play a key role in the pathogenesis of Chronic Thromboembolic Pulmonary Hypertension (CTEPH). Increased synthesis and/or the release of intercellular adhesion molecule-1 (ICAM-1) by pulmonary endothelial cells of patients with CTEPH has been recently reported, suggesting a potential role for ICAM-1 in CTEPH. METHODS: We studied pulmonary endarterectomy specimens from 172 patients with CTEPH and pulmonary artery specimens from 97 controls undergoing lobectomy for low-stage cancer without metastasis. RESULTS: ICAM-1 was overexpressed in vitro in isolated and cultured endothelial cells from endarterectomy specimens. Endothelial cell growth and apoptosis resistance were significantly higher in CTEPH specimens than in the controls (p < 0.001). Both abnormalities were abolished by pharmacological inhibition of ICAM-1 synthesis or activity. The overexpression of ICAM-1 contributed to the acquisition and maintenance of abnormal EC growth and apoptosis resistance via the phosphorylation of SRC, p38 and ERK1/2 and the overproduction of survivin. Regarding the ICAM-1 E469K polymorphism, the KE heterozygote genotype was significantly more frequent in CTEPH than in the controls, but it was not associated with disease severity among patients with CTEPH. CONCLUSIONS: ICAM-1 contributes to maintaining the abnormal endothelial cell phenotype in CTEPH.

Smooth Muscle Phenotype in Idiopathic Pulmonary Hypertension: Hyper-Proliferative but not Cancerous.

Idiopathic pulmonary arterial hypertension (IPAH) is a complex disease associated with vascular remodeling and a proliferative disorder in pulmonary artery smooth muscle cells (PASMCs) that has been variably described as having neoplastic features. To decode the phenotype of PASMCs in IPAH, PASMCs from explanted lungs of patients with IPAH (IPAH-PASMCs) and from controls (C-PASMCs) were cultured. The IPAH-PASMCs grew faster than the controls; however, both growth curves plateaued, suggesting contact inhibition in IPAH cells. No proliferation was seen without stimulation with exogenous growth factors, suggesting that IPAH cells are incapable of self-sufficient growth. IPAH-PASMCs were more resistant to apoptosis than C-PASMCs, consistent with the increase in the Bcl2/Bax ratio. As cell replication is governed by telomere length, these parameters were assessed jointly. Compared to C-PASMCs, IPAH-PASMCs had longer telomeres, but a limited replicative capacity. Additionally, it was noted that IPAH-PASMCs had a shift in energy production from mitochondrial oxidative phosphorylation to aerobic glycolysis. As DNA damage and genomic instability are strongly implicated in IPAH development a comparative genomic hybridization was performed on genomic DNA from PASMCs which showed multiple break-points unaffected by IPAH severity. Activation of DNA damage/repair factors (γH2AX, p53, and GADD45) in response to cisplatin was measured. All proteins showed lower phosphorylation in IPAH samples than in controls, suggesting that the cells were resistant to DNA damage. Despite the cancer-like processes that are associated with end-stage IPAH-PASMCs, we identified no evidence of self-sufficient proliferation in these cells-the defining feature of neoplasia.

Early outcomes of percutaneous pulmonary valve implantation using the Edwards SAPIEN 3 transcatheter heart valve system.

AIMS: Multiple surgical revisions are often necessary in individuals with congenital heart defects affecting the RVOT or pulmonary valve. There are no multicentre data on the feasibility and safety of percutaneous pulmonary valve implantation (PPVI) using the SAPIEN 3 (S3) transcatheter heart valve. The aim of this study was to explore the short-term safety, feasibility, and haemodynamic outcomes of PPVI using the S3 transcatheter heart valve. METHODS AND RESULTS: Pulmonic S3 is an observational registry of patients undergoing PPVI with the S3 valve across centres in Europe and Canada. Data for 82 patients (mean age 27.3 years) were obtained. The most common underlying diagnosis was tetralogy of Fallot (ToF) (58.5%), with 16.0% of patients having native RVOT anatomy; 90.2% received pre-stenting. Prosthesis dislodgement occurred in one patient and conduit perforation in another. Both were successfully resolved without the need for open surgery. Peak systolic gradient over the RVOT fell from 46.3 mmHg to 17.2 mmHg, moderate/severe pulmonary regurgitation from 86.3% to 0.0%, and NYHA ≥II from 86.0% to 15.2%. During follow-up, valve thrombosis was observed in two patients which resolved with adequate anticoagulation. No other procedural complications, endocarditis, stent fracture or death were reported within two years. CONCLUSIONS: PPVI with the S3 valve appears feasible and safe in a wide range of patients with congenital heart defects, with good short-term haemodynamic and functional outcomes.

Bmpr2 Mutant Rats Develop Pulmonary and Cardiac Characteristics of Pulmonary Arterial Hypertension.

BACKGROUND: Monoallelic mutations in the gene encoding bone morphogenetic protein receptor 2 ( Bmpr2) are the main genetic risk factor for heritable pulmonary arterial hypertension (PAH) with incomplete penetrance. Several Bmpr2 transgenic mice have been reported to develop mild spontaneous PAH. In this study, we examined whether rats with the Bmpr2 mutation were susceptible to developing more severe PAH. METHODS: The zinc finger nuclease method was used to establish rat lines with mutations in the Bmpr2 gene. These rats were then characterized at the hemodynamic, histological, electrophysiological, and molecular levels. RESULTS: Rats with a monoallelic deletion of 71 bp in exon 1 (Δ 71 rats) showed decreased BMPRII expression and phosphorylated SMAD1/5/9 levels. Δ 71 Rats develop age-dependent spontaneous PAH with a low penetrance (16%-27%), similar to that in humans. Δ 71 Rats were more susceptible to hypoxia-induced pulmonary hypertension than wild-type rats. Δ 71 Rats exhibited progressive pulmonary vascular remodeling associated with a proproliferative phenotype and showed lower pulmonary microvascular density than wild-type rats. Organ bath studies revealed severe alteration of pulmonary artery contraction and relaxation associated with potassium channel subfamily K member 3 (KCNK3) dysfunction. High levels of perivascular fibrillar collagen and pulmonary interleukin-6 overexpression discriminated rats that developed spontaneous PAH and rats that did not develop spontaneous PAH. Finally, detailed assessments of cardiomyocytes demonstrated alterations in morphology, calcium (Ca2+), and cell contractility specific to the right ventricle; these changes could explain the lower cardiac output of Δ 71 rats. Indeed, adult right ventricular cardiomyocytes from Δ 71 rats exhibited a smaller diameter, decreased sensitivity of sarcomeres to Ca2+, decreased [Ca2+] transient amplitude, reduced sarcoplasmic reticulum Ca2+ content, and short action potential duration compared with right ventricular cardiomyocytes from wild-type rats. CONCLUSIONS: We characterized the first Bmpr2 mutant rats and showed some of the critical cellular and molecular dysfunctions described in human PAH. We also identified the heart as an unexpected but potential target organ of Bmpr2 mutations. Thus, this new genetic rat model represents a promising tool to study the pathogenesis of PAH.

T-type Ca2+ channels elicit pro-proliferative and anti-apoptotic responses through impaired PP2A/Akt1 signaling in PASMCs from patients with pulmonary arterial hypertension.

Idiopathic pulmonary arterial hypertension (iPAH) is characterized by obstructive hyperproliferation and apoptosis resistance of distal pulmonary artery smooth muscle cells (PASMCs). T-type Ca2+ channel blockers have been shown to reduce experimental pulmonary hypertension, although the impact of T-type channel inhibition remains unexplored in PASMCs from iPAH patients. Here we show that T-type channels Cav3.1 and Cav3.2 are present in the lung and PASMCs from iPAH patients and control subjects. The blockade of T-type channels by the specific blocker, TTA-A2, prevents cell cycle progression and PASMCs growth. In iPAH cells, T-type channel signaling fails to activate phosphatase PP2A, leading to an increase in ERK1/2, P38 activation. Moreover, T-type channel signaling is redirected towards the activation of the kinase Akt1, leading to increased expression of the anti-apoptotic protein survivin, and a decrease in the pro-apoptotic mediator FoxO3A. Finally, in iPAH cells, Akt1 is no longer able to regulate caspase 9 activation, whereas T-type channel overexpression reverses PP2A defect in iPAH cells but reinforces the deleterious effects of Akt1 activation. Altogether, these data highlight T-type channel signaling as a strong trigger of the pathological phenotype of PASMCs from iPAH patients (hyper-proliferation/cells survival and apoptosis resistance), suggesting that both T-type channels and PP2A may be promising therapeutic targets for pulmonary hypertension.

Abnormal pulmonary endothelial cells may underlie the enigmatic pathogenesis of chronic thromboembolic pulmonary hypertension.

BACKGROUND: Chronic thromboembolic pulmonary hypertension results from chronic mechanical obstruction of the pulmonary arteries after acute venous thromboembolism. However, the mechanisms that result in the progression from unresolved thrombus to fibrotic vascular remodeling are unknown. We hypothesized that pulmonary artery endothelial cells contribute to this phenomenon via paracrine growth factor and cytokine signaling. METHODS: Using enzyme-linked immunosorbent assay and cell migration assays, we investigated the circulating growth factors and cytokines of chronic thromboembolic pulmonary hypertension patients as well as the cross talk between pulmonary endothelial cells and pulmonary artery smooth muscle cells and monocytes from patients with chronic thromboembolic pulmonary hypertension in vitro. RESULTS: Culture medium from the pulmonary endothelial cells of chronic thromboembolic pulmonary hypertension patients contained higher levels of growth factors (fibroblast growth factor 2), inflammatory cytokines (interleukin 1ß, interleukin 6, monocyte chemoattractant protein 1), and cell adhesion molecules (vascular cell adhesion molecule 1 and intercellular adhesion molecule 1). Furthermore, exposure to the culture medium of pulmonary endothelial cells from patients with chronic thromboembolic pulmonary hypertension elicited marked pulmonary artery smooth muscle cell growth and monocyte migration. CONCLUSIONS: These findings implicate pulmonary endothelial cells as key regulators of pulmonary artery smooth muscle cell and monocyte behavior in chronic thromboembolic pulmonary hypertension and suggest a potential mechanism for the progression from unresolved thrombus to fibrotic vascular remodeling.

Nebivolol for improving endothelial dysfunction, pulmonary vascular remodeling, and right heart function in pulmonary hypertension.

BACKGROUND: Endothelial cell (EC) dysfunction plays a central role in the pathogenesis of pulmonary arterial hypertension (PAH), promoting vasoconstriction, smooth muscle proliferation, and inflammation. OBJECTIVES: This study sought to test the hypothesis that nebivolol, a ß1-antagonist and ß2,3-agonist, may improve PAH and reverse the PAH-related phenotype of pulmonary ECs (P-EC). METHODS: We compared the effects of nebivolol with metoprolol, a first-generation ß1-selective ß-blocker, on human cultured PAH and control P-EC proliferation, vasoactive and proinflammatory factor production, and crosstalk with PA smooth muscle cells. We assessed the effects of both ß-blockers in precontracted PA rings. We also compared the effects of both ß-blockers in experimental PAH. RESULTS: PAH P-ECs overexpressed the proinflammatory mediators interleukin-6 and monocyte chemoattractant protein-1, fibroblast growth factor-2, and the potent vasoconstrictive agent endothelin-1 as compared with control cells. This pathological phenotype was corrected by nebivolol but not metoprolol in a dose-dependent fashion. We confirmed that PAH P-EC proliferate more than control cells and stimulate more PA smooth muscle cell mitosis, a growth abnormality that was normalized by nebivolol but not by metoprolol. Nebivolol but not metoprolol induced endothelium-dependent and nitric oxide-dependent relaxation of PA. Nebivolol was more potent than metoprolol in improving cardiac function, pulmonary vascular remodeling, and inflammation of rats with monocrotaline-induced pulmonary hypertension. CONCLUSIONS: Nebivolol could be a promising option for the management of PAH, improving endothelial dysfunction, pulmonary vascular remodeling, and right heart function. Until clinical studies are undertaken, however, routine use of ß-blockers in PAH cannot be recommended.

Endothelial-to-mesenchymal transition in pulmonary hypertension.

BACKGROUND: The vascular remodeling responsible for pulmonary arterial hypertension (PAH) involves predominantly the accumulation of α-smooth muscle actin-expressing mesenchymal-like cells in obstructive pulmonary vascular lesions. Endothelial-to-mesenchymal transition (EndoMT) may be a source of those α-smooth muscle actin-expressing cells. METHODS AND RESULTS: In situ evidence of EndoMT in human PAH was obtained by using confocal microscopy of multiple fluorescent stainings at the arterial level, and by using transmission electron microscopy and correlative light and electron microscopy at the ultrastructural level. Findings were confirmed by in vitro analyses of human PAH and control cultured pulmonary artery endothelial cells. In addition, the mRNA and protein signature of EndoMT was recognized at the arterial and lung level by quantitative real-time polymerase chain reaction and Western blot analyses. We confirmed our human observations in established animal models of pulmonary hypertension (monocrotaline and SuHx). After establishing the first genetically modified rat model linked to BMPR2 mutations (BMPR2(Δ140Ex1/+) rats), we demonstrated that EndoMT is linked to alterations in signaling of BMPR2, a gene that is mutated in 70% of cases of familial PAH and in 10% to 40% of cases of idiopathic PAH. We identified molecular actors of this pathological transition, including twist overexpression and vimentin phosphorylation. We demonstrated that rapamycin partially reversed the protein expression patterns of EndoMT, improved experimental PAH, and decreased the migration of human pulmonary artery endothelial cells, providing the proof of concept that EndoMT is druggable. CONCLUSIONS: EndoMT is linked to alterations in BPMR2 signaling and is involved in the occlusive vas cular remodeling of PAH, findings that may have therapeutic implications.

N-acetylcysteine improves established monocrotaline-induced pulmonary hypertension in rats.

BACKGROUND: The outcome of patients suffering from pulmonary arterial hypertension (PAH) are predominantly determined by the response of the right ventricle to the increase afterload secondary to high vascular pulmonary resistance. However, little is known about the effects of the current available or experimental PAH treatments on the heart. Recently, inflammation has been implicated in the pathophysiology of PAH. N-acetylcysteine (NAC), a well-known safe anti-oxidant drug, has immuno-modulatory and cardioprotective properties. We therefore hypothesized that NAC could reduce the severity of pulmonary hypertension (PH) in rats exposed to monocrotaline (MCT), lowering inflammation and preserving pulmonary vascular system and right heart function. METHODS: Saline-treated control, MCT-exposed, MCT-exposed and NAC treated rats (day 14-28) were evaluated at day 28 following MCT for hemodynamic parameters (right ventricular systolic pressure, mean pulmonary arterial pressure and cardiac output), right ventricular hypertrophy, pulmonary vascular morphometry, lung inflammatory cells immunohistochemistry (monocyte/macrophages and dendritic cells), IL-6 expression, cardiomyocyte hypertrophy and cardiac fibrosis. RESULTS: The treatment with NAC significantly decreased pulmonary vascular remodeling, lung inflammation, and improved total pulmonary resistance (from 0.71 ± 0.05 for MCT group to 0.50 ± 0.06 for MCT + NAC group, p < 0.05). Right ventricular function was also improved with NAC treatment associated with a significant decrease in cardiomyocyte hypertrophy (625 ± 69 vs. 439 ± 21 µm2 for MCT and MCT + NAC group respectively, p < 0.001) and heart fibrosis (14.1 ± 0.8 vs. 8.8 ± 0.1% for MCT and MCT + NAC group respectively, p < 0.001). CONCLUSIONS: Through its immuno-modulatory and cardioprotective properties, NAC has beneficial effect on pulmonary vascular and right heart function in experimental PH.

The beneficial effect of suramin on monocrotaline-induced pulmonary hypertension in rats.

BACKGROUND: Pulmonary hypertension (PH) is a progressive disorder characterized by an increase in pulmonary artery pressure and structural changes in the pulmonary vasculature. Several observations indicate that growth factors play a key role in PH by modulating pulmonary artery smooth muscle cell (PA-SMC) function. In rats, established monocrotaline-induced PH (MCT-PH) can be reversed by blocking platelet-derived growth factor receptors (PDGF-R), epidermal growth factor receptors (EGF-R), or fibroblast growth factor receptors (FGF-R). All these receptors belong to the receptor tyrosine kinase (RTK) family. METHODS AND RESULTS: We evaluated whether RTK blockade by the nonspecific growth factor inhibitor, suramin, reversed advanced MCT-PH in rats via its effects on growth-factor signaling pathways. We found that suramin inhibited RTK and ERK1/2 phosphorylation in cultured human PA-SMCs. Suramin inhibited PA-SMC proliferation induced by serum, PDGF, FGF2, or EGF in vitro and ex vivo. Treatment with suramin from day 1 to day 21 after monocrotaline injection attenuated PH development, as shown by lower values for pulmonary artery pressure, right ventricular hypertrophy, and distal vessel muscularization on day 21 compared to control rats. Treatment with suramin from day 21 to day 42 after monocrotaline injection reversed established PH, thereby normalizing the pulmonary artery pressure values and vessel structure. Suramin treatment suppressed PA-SMC proliferation and attenuated both the inflammatory response and the deposition of collagen. CONCLUSIONS: RTK blockade by suramin can prevent MCT-PH and reverse established MCT-PH in rats. This study suggests that an anti-RTK strategy that targets multiple RTKs could be useful in the treatment of pulmonary hypertension.