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Kinetic analysis of intracellular calcium (Ca

Background: Cardiac-specific myosin light chain kinase (cMLCK), encoded by MYLK3 , regulates cardiac contractility through phosphorylation of ventricular myosin regulatory light chain. However, the pathophysiological and therapeutic implications of cMLCK in human heart failure remain unclear. We aimed to investigate whether cMLCK dysregulation causes cardiac dysfunction and whether the restoration of cMLCK could be a novel myotropic therapy for systolic heart failure. Methods: We generated the knock-in mice ( Mylk3 +/fs and Mylk 3 fs/fs ) with a familial dilated cardiomyopathy–associated MYLK3 frameshift mutation ( MYLK3 +/fs ) that had been identified previously by us (c.1951-1G>T; p.P639Vfs*15) and the human induced pluripotent stem cell–derived cardiomyocytes from the carrier of the mutation. We also developed a new small-molecule activator of cMLCK (LEUO-1154). Results: Both mice ( Mylk3 +/fs and Mylk 3 fs/fs ) showed reduced cMLCK expression due to nonsense-mediated messenger RNA decay, reduced MLC2v (ventricular myosin regulatory light chain) phosphorylation in the myocardium, and systolic dysfunction in a cMLCK dose–dependent manner. Consistent with this result, myocardium from the mutant mice showed an increased ratio of cardiac superrelaxation/disordered relaxation states that may contribute to impaired cardiac contractility. The phenotypes observed in the knock-in mice were rescued by cMLCK replenishment through the AAV9_ MYLK3 vector. MYLK3 +/fs induced pluripotent stem cell–derived cardiomyocytes reduced cMLCK expression by 50% and contractile dysfunction, accompanied by an increased superrelaxation/disordered relaxation ratio. CRISPR-mediated gene correction, or cMLCK replenishment by AAV9_ MYLK3 vector, successfully recovered cMLCK expression, the superrelaxation/disordered relaxation ratio, and contractile dysfunction. LEUO-1154 increased human cMLCK activity ≈2-fold in the V max for ventricular myosin regulatory light chain phosphorylation without affecting the K m . LEUO-1154 treatment of human MYLK3 +/fs induced pluripotent stem cell–derived cardiomyocytes restored the ventricular myosin regulatory light chain phosphorylation level and superrelaxation/disordered relaxation ratio and improved cardiac contractility without affecting calcium transients, indicating that the cMLCK activator acts as a myotrope. Finally, human myocardium from advanced heart failure with a wide variety of causes had a significantly lower MYLK3 / PPP1R12B messenger RNA expression ratio than control hearts, suggesting an altered balance between myosin regulatory light chain kinase and phosphatase in the failing myocardium, irrespective of the causes. Conclusions: cMLCK dysregulation contributes to the development of cardiac systolic dysfunction in humans. Our strategy to restore cMLCK activity could form the basis of a novel myotropic therapy for advanced systolic heart failure.

Although heart failure with preserved ejection fraction (HFpEF) has a highly variable phenotype, heterogeneity in left ventricular chamber size (LVCS) and its association with long-term outcome have not been thoroughly investigated. The present study sought to determine the impact of LVCS on clinical outcome in HFpEF.A total of 1505 consecutive HFpEF patients admitted to hospitals in the multicenter WET-HF Registry for acute decompensated HF (ADHF) between 2006 and 2017 were analyzed. The patients (age: 80 [73-86], male: 48%) were divided into larger (L) or smaller (S) LV end-diastolic diameter (LVEDD) groups by the median value 45 mm.Younger age, male sex, higher body mass index, more favorable nutritional status, valvular etiology, and lower LVEF were associated with larger LVEDD. After propensity matching (399 pairs), the L group showed a larger left atrial diameter, E/e', and tricuspid regurgitation pressure gradient and greater severity of mitral regurgitation. The L group had a higher rate of composite endpoint of all-cause death and ADHF re-admission (P = 0.021) and was an independent predictor. On the other hand, in the pre-matched cohort, the S group rather showed higher in-hospital (4% versus 2%. P = 0.004) and post-discharge mortality (P = 0.009).In HFpEF, LVCS was affected by demographic and cardiac parameters. After adjustment for demographic parameters, larger LVCS was associated with worse clinical outcome. Higher mortality in the S group in the pre-matched cohort might be related to the demographic factors suggesting frailty and/or sarcopenia.

The Δ160E mutation inWe identified a heterozygous in-frame deletion mutation (c.478_480del, p.Δ160E) inHetero-Δ160E-iPSC-CMs exhibited prolonged calcium decay, relaxation impairment, and hypertrophy compared to wild type-iPSC-CMs. Notably, these phenotypes were further exacerbated in Homo-Δ160E-iPSC-CMs. Overexpression of R-GECO-fused Δ160E mutant troponin T prolonged decay time and time to peak of the myofilament-localized calcium transient in iPSC-CMs, indicating that sarcomeric calcium retention with Δ160E may affect intracellular calcium concentration. High-content imaging analysis detected remarkable nuclear translocation of NFATc1, especially in Homo-Δ160E-iPSC-CMs, indicating that the Δ160E mutation promotes hypertrophic signaling pathway in a dose-dependent manner. Increased phosphorylation of CaMKIIδ (calcium/calmodulin-dependent protein kinase IIδ) and phospholamban at Thr17 was observed in Homo- and Hetero-Δ160E-iPSC-CMs. Epigallocatechin-3-gallate, a calcium desensitizing compound, shortened prolonged calcium decay and relaxation duration in Δ160E-iPSC-CMs.Isogenic iPSC-CMs recapitulate the prolonged calcium decay, relaxation impairment, and subsequent calcium-regulated signaling pathways caused by the

We herein report the clinical potential of Impella 5.0 support, which is a catheter-mounted micro-axial left ventricular support device, in a 39-year-old man with recurrent fulminant viral myocarditis complicated with profound cardiogenic shock despite inotropic infusion and an intra-aortic balloon pumping. Switching from these therapies to the Impella 5.0 device provided sufficient systemic perfusion with well-controlled left ventricular diastolic properties to facilitate a prompt recovery from profound cardiogenic shock. The patient was uneventfully discharged on the 27th hospital day. Given its effect of cardiac protection with sufficient systemic perfusion, the Impella device should be considered the first-line therapy for the treatment of fulminant myocarditis complicated with cardiogenic shock.