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AIM: Understanding the molecular identity of human pluripotent stem cell (hPSC)-derived cardiac progenitors and mechanisms controlling their proliferation and differentiation, is valuable for developmental biology and regenerative medicine. METHODS AND RESULTS: Here we show that chemical modulation of Histone Acetyl Transferases (HATs; by IQ-1) and WNT (by CHIR99021), synergistically enable the transient and reversible block of directed cardiac differentiation progression on hPSCs. The resulting stabilized cardiovascular progenitors (SCPs) are characterized by ISL1pos/KI-67pos/NKX2-5neg expression. In the presence of the chemical inhibitors, SCPs maintain a proliferation quiescent state. Upon small molecules removal SCPs resume proliferation and concomitant NKX2-5 upregulation triggers cell-autonomous differentiation into cardiomyocytes. Directed differentiation of SCPs into the endothelial and smooth muscle lineages confirms their full developmental potential typical of bona fide cardiovascular progenitors. Single-cell RNAseq-based transcriptional profiling of our in vitro generated human SCPs notably reflects the dynamic cellular composition of E8.25-E9.25 posterior second heart field (pSHF) of mouse hearts, hallmarked by NR2F2 expression. Investigating molecular mechanisms of SCP stabilization, we found that the cell-autonomously regulated Retinoic Acid (RA) and BMP signaling is governing SCPs transition from quiescence towards proliferation and cell-autonomous differentiation, reminiscent of a niche-like behavior. CONCLUSION: The chemically defined and reversible nature our stabilization approach provides an unprecedented opportunity to dissect mechanisms of cardiovascular progenitors' specification and reveal their cellular and molecular properties.
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In the early phases of the COVID-19 pandemic, drug repurposing was widely used to identify compounds that could improve the prognosis of symptomatic patients infected by SARS-CoV-2. Hydroxychloroquine (HCQ) was one of the first drugs used to treat COVID-19 patients due to its supposed capacity of inhibiting SARS-CoV-2 infection and replication in vitro. While its efficacy is debated, HCQ has been associated with QT interval prolongation and potentially Torsades de Pointes, especially in patients predisposed to developing drug-induced Long QT Syndrome (LQTS) as silent carriers of variants associated with congenital LQTS. If confirmed, these effects represent a limitation to the at-home use of HCQ for COVID-19 infection as adequate ECG monitoring may be challenging. We investigated the proarrhythmic profile of HCQ with Multi-Electrode Arrays after subchronic exposure of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from two healthy donors, one asymptomatic and two symptomatic LQTS patients. We demonstrate that: I) HCQ induced a concentration-dependent Field Potential Duration (FPD) prolongation in vitro and triggered arrhythmias that halted the beating at high concentration. II) hiPSC-CMs from healthy or asymptomatic carriers tolerated higher concentrations of HCQ and showed lower susceptibility to HCQ-induced electrical abnormalities regardless of baseline FPD values. These findings agree with the clinical safety records of HCQ and demonstrated that hiPSC-CMs potentially discriminates symptomatic vs asymptomatic mutation carriers through pharmacological interventions. Disease-specific cohorts of hiPSC-CMs may be a valid preliminary addition to quickly assess drug safety in vulnerable populations, offering rapid preclinical results with valuable translational relevance for precision medicine.
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Background/Aims@#Patients with genotype 3 hepatitis C virus (G3-HCV) cirrhosis are very difficult to treat compared to patients with other HCV genotypes. The optimal treatment duration and drug regimen associated with ribavirin (RBV) remain unclear. To evaluate the efficacy and safety of daclatasvir (DCV)/sofosbuvir (SOF) plus a flat dose of 800 mg RBV (flat dose) compared to DCV/SOF without RBV or DCV/SOF plus an RBV dose based on body weight (weight-based) in G3-HCV patients with compensated or decompensated cirrhosis. @*Methods@#We analyzed data for 233 G3 cirrhotic patients. Of these, 70 (30%), 87(37%) and 76 (33%) received SOF/DCV, SOF/DCV/RBV flat dose, and SOF/DCV/RBV weight-based dose, respectively. Treatment duration was 24 weeks. Sustained virological response (SVR) was evaluated at week 12 posttreatment (SVR12). @*Results@#Overall, SVR12 was achieved in 220 out of 233 patients (94.4%). The SVR12 rate was lower in the DCV/SOF group than in the DCV/SOF/RBV flat-dose group and the DCV/SOF/RBV weight-based group (87.1% vs 97.7% and 97.4%, respectively, p=0.007). A higher incidence of anemia occurred in the DCV/SOF/RBV weight-based group compared to those in the other two groups (p<0.007). @*Conclusions@#We found that the DCV/SOF/RBV flat-dose regimen is an effective treatment in terms of efficacy and safety in patients with G3-HCV compensated or decompensated cirrhosis. Therefore, antiviral regimens without RBV should be restricted only to naïve patients with G3-HCV compensated cirrhosis who have a clear contraindication for RBV.
