Long-Term Effects of Pulmonary Endarterectomy on Right Ventricular Stiffness and Fibrosis in Chronic Thromboembolic Pulmonary Hypertension.

BACKGROUND: Surgical removal of thromboembolic material by pulmonary endarterectomy (PEA) leads within months to the improvement of right ventricular (RV) function in the majority of patients with chronic thromboembolic pulmonary hypertension. However, RV mass does not always normalize. It is unknown whether incomplete reversal of RV remodeling results from extracellular matrix expansion (diffuse interstitial fibrosis) or cellular hypertrophy, and whether residual RV remodeling relates to altered diastolic function. METHODS: We prospectively included 25 patients with chronic thromboembolic pulmonary hypertension treated with PEA. Structured follow-up measurements were performed before, and 6 and 18 months after PEA. With single beat pressure-volume loop analyses, we determined RV end-systolic elastance (Ees), arterial elastance (Ea), RV-arterial coupling (Ees/Ea), and RV end-diastolic elastance (stiffness, Eed). The extracellular volume fraction of the RV free wall was measured by cardiac magnetic resonance imaging and used to separate the myocardium into cellular and matrix volume. Circulating collagen biomarkers were analyzed to determine the contribution of collagen metabolism. RESULTS: RV mass significantly decreased from 43±15 to 27±11g/m2 (-15.9 g/m2 [95% CI, -21.4 to -10.5]; P<0.0001) 6 months after PEA but did not normalize (28±9 versus 22±6 g/m2 in healthy controls [95% CI, 2.1 to 9.8]; P<0.01). On the contrary, Eed normalized after PEA. Extracellular volume fraction in the right ventricular free wall increased after PEA from 31.0±3.8 to 33.6±3.5% (3.6% [95% CI, 1.2-6.1]; P=0.013) as a result of a larger reduction in cellular volume than in matrix volume (Pinteraction=0.0013). Levels of MMP-1 (matrix metalloproteinase-1), TIMP-1 (tissue inhibitor of metalloproteinase-1), and TGF-ß (transforming growth factor-ß) were elevated at baseline and remained elevated post-PEA. CONCLUSIONS: Although cellular hypertrophy regresses and diastolic stiffness normalizes after PEA, a relative increase in extracellular volume remains. Incomplete regression of diffuse RV interstitial fibrosis after PEA is accompanied by elevated levels of circulating collagen biomarkers, suggestive of active collagen turnover.

Sex-biased TGFß signalling in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a rare cardiovascular disorder leading to pulmonary hypertension and, often fatal, right heart failure. Sex differences in PAH are evident, which primarily presents with a female predominance and increased male severity. Disturbed signalling of the transforming growth factor-ß (TGFß) family and gene mutations in the bone morphogenetic protein receptor 2 (BMPR2) are risk factors for PAH development, but how sex-specific cues affect the TGFß family signalling in PAH remains poorly understood. In this review, we aim to explore the sex bias in PAH by examining sex differences in the TGFß signalling family through mechanistical and translational evidence. Sex hormones including oestrogens, progestogens, and androgens, can determine the expression of receptors (including BMPR2), ligands, and soluble antagonists within the TGFß family in a tissue-specific manner. Furthermore, sex-related genetic processes, i.e. Y-chromosome expression and X-chromosome inactivation, can influence the TGFß signalling family at multiple levels. Given the clinical and mechanistical similarities, we expect that the conclusions arising from this review may apply also to hereditary haemorrhagic telangiectasia (HHT), a rare vascular disorder affecting the TGFß signalling family pathway. In summary, we anticipate that investigating the TGFß signalling family in a sex-specific manner will contribute to further understand the underlying processes leading to PAH and likely HHT.

Exogenous loading of miRNAs into small extracellular vesicles.

Small extracellular vesicles (sEVs), through their natural ability to interact with biological membranes and exploit endogenous processing pathways to convey biological information, are quintessential for the delivery of therapeutically relevant compounds, such as microRNAs (miRNAs) and proteins. Here, we used a fluorescently-labelled miRNA to quantify the efficiency of different methods to modulate the cargo of sEVs. Our results showed that, compared with electroporation, heat shock, permeation by a detergent-based compound (saponin) or cholesterol-modification of the miRNA, Exo-Fect was the most efficient method with > 50% transfection efficiency. Furthermore, qRT-PCR data showed that, compared with native sEVs, Exo-Fect modulation led to a > 1000-fold upregulation of the miRNA of interest. Importantly, this upregulation was observed for sEVs isolated from multiple sources. The modulated sEVs were able to delivery miR-155-5p into a reporter cell line, confirming the successful delivery of the miRNA to the target cell and, more importantly, its functionality. Finally, we showed that the membrane of Exo-Fect-loaded sEVs was altered compared with native sEVs and that enhanced the internalization of Exo-Fect-loaded sEVs within the target cells and decreased the interaction of those modulated sEVs with lysosomes.