Early Alteration of Right Ventricle-Pulmonary Artery Coupling in Experimental Heart Failure With Preserved Ejection Fraction.

BACKGROUND: Pulmonary hypertension and right ventricular (RV) dysfunction are major prognostic determinants in patients with heart failure with preserved ejection fraction (HFpEF). The underlying pathomechanisms remain unknown. In this context, we sought to study the pathogenesis of pulmonary hypertension and RV dysfunction in a rat model of obesity-associated HFpEF. METHODS AND RESULTS: HFpEF was induced in obesity-prone rats fed a high-fat diet (n=13) and compared with obesity-resistant rats fed with standard chow (n=9). After 12 months, the animals underwent echocardiographic and hemodynamic evaluation followed by tissue sampling for pathobiological assessment. HFpEF rats presented mild RV pressure overload (with increased RV systolic pressure and pulmonary vascular resistance). No changes in pulmonary artery medial thickness and ex vivo vasoreactivity (to acetylcholine and endothelin-1) were observed and RNA sequencing analysis failed to identify gene clustering in HFpEF lungs. However, released nitric oxide levels were decreased in HFpEF pulmonary artery, while lung expression of preproendothelin-1 was increased. In HFpEF rats, RV structure and function were altered, with RV enlargement, decreased RV fractional area change and free wall longitudinal fractional shortening, together with altered right ventricle-pulmonary artery coupling (estimated by tricuspid annular plane systolic excursion/systolic pulmonary artery pressure). Hypertrophy and apoptosis (evaluated by transferase biotin- dUTP nick-end labeling staining) were increased in right and left ventricles of HFpEF rats. There was an inverse correlation between tricuspid annular plane systolic excursion/systolic pulmonary artery pressure and RV apoptotic rate. Plasma levels of soluble suppression of tumorigenicity-2, interleukin-1ß, -6 and -17A were increased in HFpEF rats. CONCLUSIONS: Obesity-associated HFpEF in rats spontaneously evolves to pulmonary hypertension-HFpEF associated with impaired right ventricle-pulmonary artery coupling that appears disproportionate to a slight increase in RV afterload.

Dual targeting of MAPK and PI3K pathways unlocks redifferentiation of Braf-mutated thyroid cancer organoids.

Thyroid cancer is the most common endocrine malignancy and several genetic events have been described to promote the development of thyroid carcinogenesis. Besides the effects of specific mutations on thyroid cancer development, the molecular mechanisms controlling tumorigenesis, tumor behavior, and drug resistance are still largely unknown. Cancer organoids have been proposed as a powerful tool to study aspects related to tumor development and progression and appear promising to test individual responses to therapies. Here, using mESC-derived thyroid organoids, we developed a BrafV637E-inducible model able to recapitulate the features of papillary thyroid cancer in vitro. Overexpression of the murine BrafV637E mutation, equivalent to BrafV600E in humans, rapidly triggers to MAPK activation, cell dedifferentiation, and disruption of follicular organization. BrafV637E-expressing organoids show a transcriptomic signature for p53, focal adhesion, ECM-receptor interactions, EMT, and inflammatory signaling pathways. Finally, PTC-like thyroid organoids were used for drug screening assays. The combination of MAPK and PI3K inhibitors reversed BrafV637E oncogene-promoted cell dedifferentiation while restoring thyroid follicle organization and function in vitro. Our results demonstrate that pluripotent stem cells-derived thyroid cancer organoids can mimic tumor development and features while providing an efficient tool for testing novel targeted therapies.

Zebrafish Galectin 3 binding protein is the target antigen of the microglial 4C4 monoclonal antibody.

BACKGROUND: Two decades ago, the fish-specific monoclonal antibody 4C4 was found to be highly reactive to zebrafish microglia, the macrophages of the central nervous system. This has resulted in 4C4 being widely used, in combination with available fluorescent transgenic reporters to identify and isolate microglia. However, the target protein of 4C4 remains unidentified, which represents a major caveat. In addition, whether the 4C4 expression pattern is strictly restricted to microglial cells in zebrafish has never been investigated. RESULTS: Having demonstrated that 4C4 is able to capture its native antigen from adult brain lysates, we used immunoprecipitation/mass-spectrometry, coupled to recombinant expression analyses, to identify its target. The cognate antigen was found to be a paralog of Galectin 3 binding protein (Lgals3bpb), known as MAC2-binding protein in mammals. Notably, 4C4 did not recognize other paralogs, demonstrating specificity. Moreover, our data show that Lgals3bpb expression, while ubiquitous in microglia, also identifies leukocytes in the periphery, including populations of gut and liver macrophages. CONCLUSIONS: The 4C4 monoclonal antibody recognizes Lgals3bpb, a predicted highly glycosylated protein whose function in the microglial lineage is currently unknown. Identification of Lgals3bpb as a new pan-microglia marker will be fundamental in forthcoming studies using the zebrafish model.

Transplantable human thyroid organoids generated from embryonic stem cells to rescue hypothyroidism.

The thyroid gland captures iodide in order to synthesize hormones that act on almost all tissues and are essential for normal growth and metabolism. Low plasma levels of thyroid hormones lead to hypothyroidism, which is one of the most common disorder in humans and is not always satisfactorily treated by lifelong hormone replacement. Therefore, in addition to the lack of in vitro tractable models to study human thyroid development, differentiation and maturation, functional human thyroid organoids could pave the way to explore new therapeutic approaches. Here we report the generation of transplantable thyroid organoids derived from human embryonic stem cells capable of restoring plasma thyroid hormone in athyreotic mice as a proof of concept for future therapeutic development.

Early-onset and severe pulmonary arterial hypertension due to a novel compound heterozygous association of rare VHL mutations: A case report and review of existing data.

Very rare cases of pulmonary arterial hypertension (PAH) have been linked to homozygous or compound heterozygous von Hippel-Lindau (VHL) tumor suppressor gene mutations, while heterozygous VHL mutations lead to VHL tumor syndrome. Although those entities are defined, the genotype-phenotype correlation is incompletely understood, and patient management recommendations are lacking. Here, we describe a case of severe early-onset PAH due to a so-far unreported compound heterozygous association of VHL mutations and review the existing data.

A Preclinical Rat Model of Heart Failure With Preserved Ejection Fraction With Multiple Comorbidities.

Heart failure with preserved ejection fraction (HFpEF) is a common complex clinical syndrome for which there are currently few evidence-based therapies. As patients with HFpEF very often present with comorbidities comprising the metabolic syndrome, we hypothesized, that metabolic syndrome could lead over time to the development of diastolic dysfunction and HFpEF. Obesity-prone rats were exposed to high-fat diet and compared to obesity-resistant rats fed with standard chow. Phenotyping of metabolic syndrome, associated with echocardiographic and cardiac hemodynamic measurements, was performed after 4 and 12 months. Blood and myocardial tissue sampling were performed for pathobiological evaluation. High-fat diet in obesity-prone rats elicited metabolic syndrome, characterized by increased body and abdominal fat weights, glucose intolerance and hyperlipidemia, as well as increased left ventricular (LV) systolic pressure (after 12 months). This was associated with LV diastolic dysfunction (assessed by increased LV end-diastolic pressure) and pulmonary hypertension (assessed by increased right ventricular systolic pressure). Echocardiography revealed significant concentric LV hypertrophy, while LV ejection fraction was preserved. LV remodeling was associated with cardiomyocyte hypertrophy, as well as myocardial and perivascular fibrosis. Circulating levels of soluble ST2 (the interleukin-1 receptor-like) markedly increased in rats with HFpEF, while plasma NT-proBNP levels decreased. RNA-sequencing analysis identified clusters of genes implicated in fatty acid metabolism and calcium-dependent contraction as upregulated pathways in the myocardium of rats with HFpEF. High-fat diet during 12 months in obesity-prone rats led to the development of a relevant preclinical model of HFpEF with multiple comorbidities, suitable for investigating novel therapeutic interventions.

Clinical phenotypes and outcomes of pulmonary hypertension due to left heart disease: Role of the pre-capillary component.

BACKGROUND: In pulmonary hypertension (PH), both wedge pressure elevation (PAWP) and a precapillary component may affect right ventricular (RV) afterload. These changes may contribute to RV failure and prognosis. We aimed at describing the different haemodynamic phenotypes of patients with PH due to left heart disease (LHD) and at characterizing the impact of pulmonary haemodynamics on RV function and outcome PH-LHD. METHODS: Patients with PH-LHD were compared with treatment-naïve idiopathic/heritable pulmonary arterial hypertension (PAH, n = 35). PH-LHD patients were subdivided in Isolated post-capillary PH (IpcPH: diastolic pressure gradient, DPG<7 mmHg and pulmonary vascular resistance, PVR≤3 WU, n = 37), Combined post- and pre-capillary PH (CpcPH: DPG≥7 mmHg and PVR>3 WU, n = 27), and "intermediate" PH-LHD (either DPG <7 mmHg or PVR ≤3 WU, n = 29). RESULTS: Despite similar PAWP and cardiac index, haemodynamic severity and prevalence of RV dysfunction increased from IpcPH, to "intermediate" and CpcPH. PVR and DPG (but not compliance, Ca) were linearly correlated with RV dysfunction. CpcPH had worse prognosis (p<0.05) than IpcPH and PAH, but similar to "intermediate" patients. Only NTproBNP and Ca independently predicted survival in PH-LHD. CONCLUSIONS: In PH-LHD, haemodynamic characterization according to DPG and PVR provides important information on disease severity, predisposition to RV failure and prognosis. Patients presenting the CpcPH phenotype appear to have haemodynamic profile closer to PAH but with worse prognosis. In PH-LHD, Ca and NTproBNP were independent predictors of survival.