Biology subjects

Ferrantini, C.

Publications and source records attributed to Ferrantini, C..

4 recordsLinked to original sources

bioRxiv2026

Species-Dependent Limitations of Murine Myocardium for Investigating the Combined Inotropic Effects of SERCA2a Stimulation and Myofilament Ca2+ Sensitization

Impaired sarcoplasmic reticulum Ca2+ handling and myofilament function both contribute to contractile dysfunction in heart failure. A previous study in failing human myocardium showed that combining the SERCA2a activator istaroxime (ISTA) with the Ca2+ sensitizer levosimendan (LEVO) produces greater positive inotropy than either drug alone. However, human multicellular preparations did not allow comprehensive investigation of the underlying cellular mechanisms. We therefore assessed contractile performance and Ca2+ dynamics in murine multicellular myocardial preparations and ventricular cardiomyocytes treated with ISTA (20 M), LEVO (0.5 M), or their combination. ISTA improved developed force, contraction-relaxation kinetics, and mechanical restitution. These effects were associated with increased Ca2+ transient amplitude, accelerated Ca2+ rise and decay, and enhanced sarcoplasmic reticulum reloading. Adding LEVO produced no further mechanical benefit and only minor changes in Ca2+ handling. LEVO alone elicited heterogeneous contractile responses and increased myofilament Ca2+ sensitivity in only a minority of cardiomyocytes, while consistently accelerating Ca2+ transient decay. This effect was reproduced by the phosphodiesterase-3 inhibitor cilostamide, after which LEVO caused no significant additional change, consistent with a contribution of downstream cAMP-PKA signaling to the acceleration of Ca2+ removal. Thus, limited murine responsiveness to LEVO-mediated myofilament sensitization prevented mechanistic reconstruction of the additive inotropic effect observed in human myocardium, highlighting a species-dependent limitation of the mouse model for studying this combined therapy.

physiology↗

bioRxiv2025

Long-term mavacamten exposure reduces force and sarcomere density in a hiPSC model of hypertrophic cardiomyopathy

BackgroundMavacamten, a first-in-class allosteric myosin inhibitor, has demonstrated efficacy and safety in obstructive hypertrophic cardiomyopathy (oHCM), notably reducing symptoms, left ventricular outflow obstruction, and wall thickness over 30 weeks. We recently reported that the MYBPC3:c.772G>A variant causes HCM through cMyBP-C haploinsufficiency, leading to accelerated sarcomere kinetics and higher energy consumption in patient myocardium and hiPSC- derived cardiomyocytes (hiPSC-CMs). These effects are counterbalanced by prolonged action potentials and slower Ca{superscript 2} transients, which preserve twitch duration but may increase arrhythmic risk. Mavacamten may reduce myocardial energetic defects in HCM. ObjectivesTo investigate the long-term effects of Mavacamten on sarcomere structure, contractility, and transcriptional remodeling using patient-specific and CRISPR-corrected isogenic hiPSC-derived cardiomyocyte models of HCM. MethodsHiPSC-CMs and engineered heart tissues (EHTs) derived from a MYBPC3:c.772G>A patient and its CRISPR-corrected line were first exposed to increasing concentrations of Mavacamten to assess acute dose-response relationships and determine IC50 values. Based on these data, chronic treatments (0.3- 0.75 M for 20 days) were performed mechanical, structural, electrophysiological, and transcriptomic adaptations. ResultsAcute exposure produced a rapid and fully reversible reduction in active force, while chronic treatment for 20 days induced a sustained decrease in contractility with incomplete recovery after 4 days of washout, indicating a two-phase mechanism of action. Long-term force reduction was paralleled by decreased cell area and sarcomere density, indicating that structural disassembly contributes to sustained functional depression and re-assembly after washout. Electrophysiological analysis confirmed the specific alterations of the MYBPC3:c.772G>A mutation previously observed, with no detectable effects following treatment with Mavacamten. In addition, transcriptome analysis was used to study the molecular mechanisms underlying the long-term effect. ConclusionsMavacamten induces a biphasic, persistent-to-reversible, reduction of sarcomeric force associated with structural remodeling, providing mechanistic insight into its capacity to promote favorable cardiac remodeling in oHCM.

physiology↗

bioRxiv2025

Probing relaxed myosin states in hypertrophic cardiomyopathy by second harmonic-generation microscopy

This study explores the use of polarized second-harmonic generation (pSHG) to investigate myosin conformation in the relaxed state, differentiating between the actin-available, disordered (ON) state and the energy-conserving, ordered (OFF) state. By shifting the ON/OFF equilibrium using both physical and chemical manipulations, we demonstrate the sensitivity of pSHG in quantifying the ON/OFF ratio in skeletal and cardiac tissues. Comparisons with X-ray diffraction measurements further validate our findings. Applying this approach to a sarcomeric mutation associated with hypertrophic cardiomyopathy, we show that R403Q/MYH7-mutated minipig ventricle tissue exhibits a higher ON fraction compared to controls. This difference is abolished under high concentrations of a myosin activator (2-deoxyATP) and an inhibitor (Mavacamten), indicating structural similarity between R403Q and controls in these two states. ATPase assays reveal increased resting ATPase activity in R403Q samples, which persists even in the presence of 2-deoxyATP, suggesting that the elevated energy consumption in the R403Q mutation is driven by both a population shift toward the ON state and enhanced myosin ATPase activity per motor head.

physiology↗

bioRxiv2020

3D imaging and morphometry of the heart capillary system in spontaneously hypertensive rats and normotensive controls

Systemic arterial hypertension is a highly prevalent chronic disease associated with hypertensive cardiomyopathy. One important feature of this condition is remodelling of intramural small coronary arteries and arterioles. Here, we investigated the implications of this remodelling in the downstream vascular organization, in particular at the capillary level. We used Spontaneously Hypertensive Rats (SHR) exhibiting many features of the human hypertensive cardiomyopathy. We generated 3D high-resolution mesoscopic reconstructions of the entire network of SHR hearts combining gel-based fluorescent labelling of coronaries with a CLARITY-based tissue clearing protocol. We performed morphometric quantification of the capillary network over time to assess capillary diameter, linear density, and angular dispersion. In SHRs, we found significant remodelling of the capillary network density and dispersion. SHR capillary density is increased in both ventricles and at all ages, including before the onset of systemic hypertension. This result suggests that remodelling occurs independently from the onset of systemic hypertension and left ventricular hypertrophy. On the contrary, capillary angular dispersion increases with time in SHR. Consistently, our multi-modal imaging underlined a strong correlation between vascular dispersion and cellular disarray. Together our data show that 3D high-resolution reconstruction of the capillary network can unveil anatomic signatures in both physiological and pathological cardiac conditions, thus offering a reliable method for integrated quantitative analyses.

physiology↗