Rationale:: Primary cilia are cellular protrusions that serve as mechanosensors for fluid flow. In endothelial cells (ECs), they function by transducing local blood flow information into functional responses, such as nitric oxide production and initiation of gene expression. Cilia are present on ECs in areas of low or disturbed flow and absent in areas of high flow. In the embryonic heart, high-flow regime applies to the endocardial cushion area, and the absence of cilia here coincides with the process of endothelial-to-mesenchymal transition (EndoMT). Objective:: In this study, we investigated the role of the primary cilium in defining the responses of ECs to fluid shear stress and in EndoMT. Methods and Results:: Nonciliated mouse embryonic ECs with a mutation in Tg737/Ift88 were used to compare the response to fluid shear stress to that of ciliated ECs. In vitro, nonciliated ECs undergo shear-induced EndoMT, which is accompanied by downregulation of Klf4. This Tgfβ/Alk5-dependent transformation is prevented by blocking Tgfβ signaling, overexpression of Klf4, or rescue of the primary cilium. In the hearts of Tg737 ^orpk/orpk embryos, Tgfβ/Alk5 signaling was activated in areas in which ECs would normally be ciliated but now lack cilia because of the mutation. In these areas, ECs show increased Smad2 phosphorylation and expression of α-smooth muscle actin. Conclusions:: This study demonstrates the central role of primary cilia in rendering ECs prone to shear-induced activation of Tgfβ/Alk5 signaling and EndoMT and thereby provides a functional link between primary cilia and flow-related endothelial performance.

Objective Pharmacological options for patients with a failing systemic right ventricle (RV) in the context of transposition of the great arteries (TGA) after atrial switch or congenitally corrected TGA (ccTGA) are not well defined. This study aims to investigate the feasibility and effects of sacubitril/valsartan treatment in a single-centre cohort of patients. Methods Data on all consecutive adult patients (n=20, mean age 46 years, 50% women) with a failing systemic RV in a biventricular circulation treated with sacubitril/valsartan in our centre are reported. Patients with a systemic RV ejection fraction of ≤35% who were symptomatic despite treatment with β-blocker and ACE-inhibitor/angiotensin II receptor-blockers were started on sacubitril/valsartan. This cohort underwent structural follow-up including echocardiography, exercise testing, laboratory investigations and quality of life (QOL) assessment. Results Six-month follow-up data were available in 18 out of 20 patients, including 12 (67%) patients with TGA after atrial switch and 6 (33%) patients with ccTGA. N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) decreased significantly (950–358 ng/L, p<0.001). Echocardiographic systemic RV fractional area change and global longitudinal strain showed small improvements (19%–22%, p<0.001 and −11% to −13%, p=0.014, respectively). The 6 min walking distance improved significantly from an average of 564 to 600 m (p=0.011). The QOL domains of cognitive function, sleep and vitality improved (p=0.015, p=0.007 and p=0.037, respectively). Conclusions We describe the first patient cohort with systemic RV failure treated with sacubitril/valsartan. Treatment appears feasible with improvements in NT-pro-BNP and echocardiographic function. Our positive results show the potential of sacubitril/valsartan for this patient population.

Endothelial-to-mesenchymal transition (EndoMT) is an instrumental step in the development of valves in the embryonic heart. This process is driven by activation of transforming growth factor–β (TGF-β) signaling and is characterized by the loss of endothelial and gain of mesenchymal phenotype, and by delamination of cells from the surface into the underlying endocardial cushion matrix. The endothelial cells (ECs) overlying the cushions are typically exposed to high blood flow and concomitant shear stress and do not have a primary cilium. Here, we show that shear stress activates TGF-β–Alk5 signaling in ECs, which is necessary for EndoMT in the cushions. Moreover, we show that the absence of a primary cilium is critically important for this transition process.

Endothelial cells (EC) translate biomechanical forces into functional and phenotypic responses that play important roles in cardiac development. Specifically, EC in areas of high shear stress, i.e., in the cardiac outflow tract and atrioventricular canal, are characterized by high expression of Krüppel-like factor 2 (Klf2) and by transforming growth factor-beta (Tgfβ)-driven endothelial-to-mesenchymal transition. Extraembryonic venous obstruction (venous clip model) results in congenital heart malformations, and venous clip-induced alterations in shear stress-related gene expression are suggestive for an increase in cardiac shear stress. Here, we study the effects of shear stress on Klf2 expression and Tgfβ-associated signaling in embryonic EC in vivo using the venous clip model and in vitro by subjecting cultured EC to fluid flow. Cellular responses were assessed by analysis of Klf2, Tgfβ ligands, and their downstream signaling targets. Results show that, in embryonic EC, shear stress activates Tgfβ/Alk5 signaling and that induction of Klf2 is an Alk5 dependent process. Developmental Dynamics 240:1670–1680, 2011.

Heart failure (HF) is the principal cause of morbidity and mortality in adults with congenital heart disease (ACHD). Robust evidence-based treatment options are lacking. This study aims to evaluate the safety, tolerability, and short-term HF-related effects of sodium-glucose cotransporter 2 inhibitors (SGLT2i) in a real-world ACHD population. All patients with ACHD treated with SGLT2i in 4 European ACHD centers were included in this retrospective study. Data were collected from 1 year before starting SGLT2i to the most recent follow-up. Data on side effects, discontinuation, mortality, and hospitalizations were collected. In total, 174 patients with ACHD were treated with SGLT2i from April 2016 to July 2023. The mean age was 48.7 ± 15.3 years, 72 (41.4%) were female, and 29 (16.7%) had type 2 diabetes mellitus. Ten (5.7%) patients had mild, 75 (43.1%) moderate, and 89 (51.1%) severe congenital heart disease. HF was the most frequent starting indication (n = 162, 93.1%), followed by type 2 diabetes (n = 11, 6.3%) and chronic kidney disease (n = 1, 0.6%). At median follow-up of 7.7 months (Q1-Q3: 3.9-13.2 months), 18 patients (10.3%) reported side effects, 12 (6.9%) permanently discontinued SGLT2i, and 4 (2.3%) died of SGLT2i-unrelated causes. A significant reduction in the HF hospitalization rate was observed from 6 months before to 6 months after starting SGLT2i (relative rate = 0.30; 95% CI: 0.14-0.62; P = 0.001). SGLT2i generally seem safe, well-tolerated, and potentially beneficial in patients with ACHD. SGLT2i was associated with a 3-fold reduction in the 6-month HF hospitalization rate. These results warrant prospective randomized investigation of the potential benefits of SGLT2i for patients with ACHD.