Search

Action potential (AP), via the transverse axial tubular system (TATS), synchronously triggers uniform Ca2+-release throughout the cardiomyocyte. Cardiac diseases associated with TATS structural remodeling preclude a uniform Ca2+-release across the myocyte, contributing to contractile dysfunction. Here, we combined the advantage of an ultrafast random access multi-photon (RAMP) microscope with a double staining approach to optically record AP in several TATS elements and, simultaneously, the corresponding local Ca2+-transient.In rat control cardiomyocytes, although AP was uniform between surface sarcolemma (SS) and t-tubules (TT) at steady-state stimulation, we observed a non-negligible beat-to-beat variability of local Ca2+-transient amplitude and kinetics. This variability was significantly reduced applying 0.1 μM Isoproterenol, which increases the open probability of Ca2+-release units. Ca2+ sparks, detected at times throughout the TATS, did not induce any membrane potential variation in the surrounding tubular elements.In a rat model of post-ischemic heart failure (HF), we previously demonstrated that some tubular elements fail to propagate AP (AP-; Sacconi PNAS 2012). Here, we found that those AP- tubules displayed a slower and reduced local Ca2+-transient compared to electrically coupled tubules (AP+). Consistently, in a model of acute detubulation, tubules that do not conduct AP showed a local reduction and delay of Ca2+-transient rise. In addition, variability of Ca2+-transient kinetics was increased in HF. Finally, AP- tubular elements, occasionally exhibited spontaneous depolarisations of various amplitude and kinetics. These events were never accompanied by local Ca2+-release in the absence of pro-arrhythmogenic stimuli, while they could induce local Ca2+-release in the presence of 0.1 μM Isoproterenol. Simultaneous recording of AP and Ca2+-transient allows us to probe the spatio-temporal variability of Ca2+-release, whereas the investigation of Ca2+-transient in HF discloses an unexpected uncoupling between t-tubular depolarization and Ca2+-release in remodelled tubules. This work was supported by the European Union 7th Framework Program (FP7/2007- 2013) under grant agreement n° 284464, 241526, by the Italian Ministry of University and Research (NANOMAX), and by Telethon-Italy (GGP13162). [ABSTRACT FROM AUTHOR]

Introduction: In HCM human tissue, primary functional alterations at the level of the sarcomeres are associated with secondary changes of Ca2+ handling and membrane EP, leading to a pro-arrhythmogenic phenotype and alteration of myocardial relaxation (Circulation. 2013 Feb 5;127(5):575-84). The relative contribution of primary vs secondary alterations is still unknown.Methods: Here we aim to study these changes in intact trabeculae, single cardiomyocytes and skinned preparations from the ventricles of transgenic mouse models aged 6 months carrying HCM-related mutations of cTnT (R92Q, E163R).Results: Compared to WT, R92Q trabeculae showed: (i) preserved peak isometric twitch tension at low inotropic level with reduced contractile reserve; (ii) prolonged relaxation kinetics associated with reduced SERCA function; (iii) faster mechanical restitution, indicating shorter RyR2 refractoriness; (iv) Frequent after-contractions or spontaneous beats during pauses, which increased in response to isoproterenol. Compared to WT, R92Q cardiomyocytes showed: (i) prolonged action potentials due to ionic current remodeling; (ii) reduced amplitude and slower decay rate of Ca2+transients; (iii) elevated diastolic [Ca2+]I and (iv) spontaneous Ca2+ waves and Ca2+transients under isoproterenol.In E163R vs. WT trabeculae and cells, peak isometric tension and Ca2+ transient amplitude were preserved in all conditions. Interestingly, the kinetics of force development and relaxation was prolonged, despite Ca2+ transient kinetics was faster and SERCA function unchanged. E163R myocardium showed faster mechanical restitution and increased spontaneous activity. Further, E163R myofibrils showed a prolongation of the overall relaxation, with incomplete inactivation in the absence of Ca2+. Energy cost of contraction, measured with an enzymatic assay of sarcomeric ATPase activity, as well as myofilaments Ca2+ sensitivity, were increased in E163R vs. WT skinned trabeculae.Conclusions: Primary changes of myofilaments function (increased Ca2+ sensitivity), previously described in R92Q hearts, are associated with a large spectrum of EC-coupling and membrane EP changes, which appear to be a major contributor to the observed mechanical dysfunction and arrhythmogeneicity in this mouse line, resembling advanced human disease. In E163R instead, impairment of myofilament function appear to be the leading element determining mechanical abnormalities. In the absence of major EC-coupling changes, the increased arrhythmogeneicity in E163R myocardium may be a direct consequence of the increased myofilaments Ca2 sensitivity. [ABSTRACT FROM AUTHOR]

Omecamtiv mecarbil (OM) is a small molecule that has been shown to improve the function of the slow human ventricular myosin (MyHC) motor through a complex perturbation of the thin/thick filament regulatory state of the sarcomere mediated by binding to myosin allosteric sites coupled to inorganic phosphate (Pi) release. Here, myofibrils from samples of human left ventricle (β-slow MyHC-7) and left atrium (α-fast MyHC-6) from healthy donors were used to study the differential effects of μmolar [OM] on isometric force in relaxing conditions (pCa 9.0) and at maximal (pCa 4.5) or half-maximal (pCa 5.75) calcium activation, both under control conditions (15 °C; equimolar DMSO; contaminant inorganic phosphate [Pi] ~170 μM) and in the presence of 5 mM [Pi]. The activation state and OM concentration within the contractile lattice were rapidly altered by fast solution switching, demonstrating that the effect of OM was rapid and fully reversible with dose-dependent and myosin isoform-dependent features. In MyHC-7 ventricular myofibrils, OM increased submaximal and maximal Ca 2+ -activated isometric force with a complex dose-dependent effect peaking (40% increase) at 0.5 μM, whereas in MyHC-6 atrial myofibrils, it had no effect or-at concentrations above 5 µM-decreased the maximum Ca 2+ -activated force. In both ventricular and atrial myofibrils, OM strongly depressed the kinetics of force development and relaxation up to 90% at 10 μM [OM] and reduced the inhibition of force by inorganic phosphate. Interestingly, in the ventricle, but not in the atrium, OM induced a large dose-dependent Ca 2+ -independent force development and an increase in basal ATPase that were abolished by the presence of millimolar inorganic phosphate, consistent with the hypothesis that the widely reported Ca 2+ -sensitising effect of OM may be coupled to a change in the state of the thick filaments that resembles the on-off regulation of thin filaments by Ca 2+ . The complexity of this scenario may help to understand the disappointing results of clinical trials testing OM as inotropic support in systolic heart failure compared with currently available inotropic drugs that alter the calcium signalling cascade.

Objective: To develop a differential diagnosis of a mass retrieved alongside skeletal remains in the crypt of the church of Santissima Annunziata of Valenza (Province of Alessandria, Northern Italy)., Material: A calcified mass measuring 40 × 39 mm and 17.62 × 16.3817.62 × 16.38 mm., Method: The analysis utilized macroscopic assessment and histologic examination (including histochemical and immunohistochemical analyses)., Results: Morphological traits include an irregular and spongy external surface. Holes of different sizes lead toward the inner part of the object. A section of the mass shows an "intertwined bundle" pattern, confirmed by microscopic examination., Conclusions: Differential diagnosis determined the mass to be consistent with calcified leiomyoma., Significance: Identifying uterine leiomyoma adds to the paucity of paleopathological literature on the condition and to calcified tumors more broadly. It also allows for an important discussion of women's gynecological health in the past and potentially among nulliparous women., Limitations: Neither histochemical staining nor immunohistochemical analysis demonstrated the certain muscular nature of the specimens due to the rehydration and decalcification processes, for which there are no gold standards., Suggestions for Further Research: Calcified masses are common in the clinical literature but remain rare in paleopathological literature. Careful excavation and improved recognition of apparently calcified masses are necessary to improve recognition, diagnosis, and interpretation., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

We discuss the coexistence of a postmortem cut and a pathological alteration, recorded on a skeleton belonging to an adult man that was discovered during the archaeological investigations of the cemetery of the Church of Santa Maria Maggiore in Vercelli (northern Italy, 18 th -19 th century). The skull presents an oblique cleft, which from the top of the frontal bone bends towards the occipital, and the left styloid process is elongated compared to normal values (48 mm). The elongated styloid process is due to the ossification of the styloid ligament which has several possible causes. To increase the knowledge about this pathological condition in the past, it was necessary to compare all the data present in the literature today and consider the few cases published in the paleopathological field. In this paper, our main goals are: i) to investigate the reasons for which the craniotomy was performed; ii) to examine the possible cause of the ossification of the styloid process, described as Eagle's syndrome; iii) to enrich the archaeological literature of elongated styloid process cases and iv) to investigate the presence of a hypothetical relationship between the autopsy cut and the diagnosed Eagle's syndrome on this skull.

Objectives: This paper aims to present one of the first osteoarchaeological cases of orbital osteomyelitis and provides the best diagnostic criteria to identify its pathophysiological changes., Materials: A well-preserved skeleton of an adult male from the medieval cemetery of Sant' Agostino in Caravate, Italy., Methods: Macroscopic, tomographic, and histological analyses were performed using standard methods., Results: The skeleton shows irregularities in the architecture of the left supraorbital margin. CT analysis reveals the presence of a radiotransparent area involving the diploe and the external cranial table. This area is lateromedially oval-shaped and bordered by a thick irregular radiodense rim, associated with the presence of a cloaca on the roof of the orbit and surrounding periosteal reaction. Microscopic examination shows the formation of a thin layer of cortical bone and an osteoid-like matrix., Conclusion: A careful differential diagnosis based on macroscopic, radiological, and histological evidence suggests a case of orbital osteomyelitis., Significance: This case study represents one of the few osteoarchaeological evaluations of ocular chronic osteomyelitis diagnosed using macroscopic skeletal, computed tomography, and histological analysis. As such, it provides a reference and an investigative criterion for future cases., Limitations: The diagnosis cannot be stated with certainty, and only probable diagnoses can be proposed. Although we referred especially to clinical literature, it is necessary to consider that the severity of conditions may be modified by modern medical intervention., Suggestion for Further Research: This case provides further insights into the presence of this condition in the past., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Palladin (PALLD) belongs to the PALLD/myopalladin (MYPN)/myotilin family of actin-associated immunoglobulin-containing proteins in the sarcomeric Z-line. PALLD is ubiquitously expressed in several isoforms, and its longest 200 kDa isoform, predominantly expressed in striated muscle, shows high structural homology to MYPN. MYPN gene mutations are associated with human cardiomyopathies, whereas the role of PALLD in the heart has remained unknown, partly due to embryonic lethality of PALLD knockout mice. In a yeast two-hybrid screening, CARP/Ankrd1 and FHOD1 were identified as novel interaction partners of PALLD's N-terminal region. To study the role of PALLD in the heart, we generated conditional (cPKO) and inducible (cPKOi) cardiomyocyte-specific PALLD knockout mice. While cPKO mice exhibited no pathological phenotype, ablation of PALLD in adult cPKOi mice caused progressive cardiac dilation and systolic dysfunction, associated with reduced cardiomyocyte contractility, intercalated disc abnormalities, and fibrosis, demonstrating that PALLD is essential for normal cardiac function. Double cPKO and MYPN knockout (MKO) mice exhibited a similar phenotype as MKO mice, suggesting that MYPN does not compensate for the loss of PALLD in cPKO mice. Altered transcript levels of MYPN and PALLD isoforms were found in myocardial tissue from human dilated and ischemic cardiomyopathy patients, whereas their protein expression levels were unaltered., Competing Interests: GM, PC, JZ, BS, NP, SN, MF, SS, CO, CT, FE, WL, CP, SB, MB No competing interests declared, (© 2023, Mastrototaro et al.)

This work presents the neoplastic bone changes found in the lower limb of a medieval skeleton from the church of Sant' Agostino in Caravate (Northern Italy). After briefly assessing the individual's overall pathological picture, a differential diagnosis for the neoplastic changes is now proposed. These changes were analysed macroscopically and radiographically and subsequently evaluated considering the paleopathological and clinical literature available. The differential diagnosis allowed us to recognize a tibiofibular osteochondroma and some enchondromas in the medullary cavity of the tibia. The results presented here highlight the importance of radiological analyses in the recognition and study of bone neoplasms in the paleopathological field, further contributing to our knowledge of the presence of neoplasms in Medieval Northern Italy.

Background: The pathogenesis of MYBPC3 -associated hypertrophic cardiomyopathy (HCM) is still unresolved. In our HCM patient cohort, a large and well-characterized population carrying the MYBPC3 :c772G>A variant (p.Glu258Lys, E258K) provides the unique opportunity to study the basic mechanisms of MYBPC3 -HCM with a comprehensive translational approach., Methods: We collected clinical and genetic data from 93 HCM patients carrying the MYBPC3 :c772G>A variant. Functional perturbations were investigated using different biophysical techniques in left ventricular samples from 4 patients who underwent myectomy for refractory outflow obstruction, compared with samples from non-failing non-hypertrophic surgical patients and healthy donors. Human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes and engineered heart tissues (EHTs) were also investigated., Results: Haplotype analysis revealed MYBPC3 :c772G>A as a founder mutation in Tuscany. In ventricular myocardium, the mutation leads to reduced cMyBP-C (cardiac myosin binding protein-C) expression, supporting haploinsufficiency as the main primary disease mechanism. Mechanical studies in single myofibrils and permeabilized muscle strips highlighted faster cross-bridge cycling, and higher energy cost of tension generation. A novel approach based on tissue clearing and advanced optical microscopy supported the idea that the sarcomere energetics dysfunction is intrinsically related with the reduction in cMyBP-C. Studies in single cardiomyocytes (native and hiPSC-derived), intact trabeculae and hiPSC-EHTs revealed prolonged action potentials, slower Ca 2+ transients and preserved twitch duration, suggesting that the slower excitation-contraction coupling counterbalanced the faster sarcomere kinetics. This conclusion was strengthened by in silico simulations., Conclusions: HCM-related MYBPC3 :c772G>A mutation invariably impairs sarcomere energetics and cross-bridge cycling. Compensatory electrophysiological changes (eg, reduced potassium channel expression) appear to preserve twitch contraction parameters, but may expose patients to greater arrhythmic propensity and disease progression. Therapeutic approaches correcting the primary sarcomeric defects may prevent secondary cardiomyocyte remodeling.

Introduction: Issues of disposal of fetal remains and related parental distress do not concern only the present. This contribution aims at offering a glimpse of what grieving management concerning perinatal death must have been in ancient times. The discussion of the topic of death and treatment of perinatal remains is based on historical, anthropological, and bioethical reasoning, in a dialogue that contributes to the current debate on fetal personhood. Methods: We have considered written and archaeological sources to investigate the response of past societies to perinatal death, in parallel with today's bioethical and legislative issues on fetal identity. Results: From historical evidence and archaeological findings, it emerges that lay community compassion and mercy often far exceeded the Church's norms, which for centuries have denied the burial of fetuses and stillborn infants in consecrated cemeteries. Over the centuries, the practices implemented by people have led to a theoretical reflection on the dignity to be recognized to infants. Conclusions: This contribution highlighted how issues about the treatment and burial of infants have interrogated women and men over the centuries. In the past, the development of rituals, even far from ecclesiastical norms, allowed people to endure mourning for the death of their children.Recent legislative initiatives by some States on the burial of embryos and fetuses within cemeteries have reopened the long-standing debate on the value to be attributed to the life of the fetus. The challenge of reaching an agreement on ethically controversial questions gives vigor to the research for strategies capable of settling different needs: the respect for the choice of women, the need to identify forms of protection of human life after death, the development by the community of rites capable of welcoming and accompanying parental mourning.

Cardiomyocytes differentiated from human induced Pluripotent Stem Cells (hiPSC- CMs) are a unique source for modelling inherited cardiomyopathies. In particular, the possibility of observing maturation processes in a simple culture dish opens novel perspectives in the study of early-disease defects caused by genetic mutations before the onset of clinical manifestations. For instance, calcium handling abnormalities are considered as a leading cause of cardiomyocyte dysfunction in several genetic-based dilated cardiomyopathies, including rare types such as Duchenne Muscular Dystrophy (DMD)-associated cardiomyopathy. To better define the maturation of calcium handling we simultaneously measured action potential and calcium transients (Ca-Ts) using fluorescent indicators at specific time points. We combined micropatterned substrates with long-term cultures to improve maturation of hiPSC-CMs (60, 75 or 90 days post-differentiation). Control-(hiPSC)-CMs displayed increased maturation over time (90 vs 60 days), with longer action potential duration (APD), increased Ca-T amplitude, faster Ca-T rise (time to peak) and Ca-T decay (RT50). The progressively increased contribution of the SR to Ca release (estimated by post-rest potentiation or Caffeine-induced Ca-Ts) appeared as the main determinant of the progressive rise of Ca-T amplitude during maturation. As an example of severe cardiomyopathy with early onset, we compared hiPSC-CMs generated from a DMD patient (DMD-ΔExon50) and a CRISPR-Cas9 genome edited cell line isogenic to the healthy control with deletion of a G base at position 263 of the DMD gene (c.263delG-CMs). In DMD-hiPSC-CMs, changes of Ca-Ts during maturation were less pronounced: indeed, DMD cells at 90 days showed reduced Ca-T amplitude and faster Ca-T rise and RT50, as compared with control hiPSC-CMs. Caffeine-Ca-T was reduced in amplitude and had a slower time course, suggesting lower SR calcium content and NCX function in DMD vs control cells. Nonetheless, the inotropic and lusitropic responses to forskolin were preserved. CRISPR-induced c.263delG-CM line recapitulated the same developmental calcium handling alterations observed in DMD-CMs. We then tested the effects of micropatterned substrates with higher stiffness. In control hiPSC-CMs, higher stiffness leads to higher amplitude of Ca-T with faster decay kinetics. In hiPSC-CMs lacking full-length dystrophin, however, stiffer substrates did not modify Ca-Ts but only led to higher SR Ca content. These findings highlighted the inability of dystrophin-deficient cardiomyocytes to adjust their calcium homeostasis in response to increases of extracellular matrix stiffness, which suggests a mechanism occurring during the physiological and pathological development (i.e. fibrosis)., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Pioner, Santini, Palandri, Langione, Grandinetti, Querceto, Martella, Mazzantini, Scellini, Giammarino, Lupi, Mazzarotto, Gowran, Rovina, Santoro, Pompilio, Tesi, Parmeggiani, Regnier, Cerbai, Mack, Poggesi, Ferrantini and Coppini.)

The quest for novel methods to mature human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for cardiac regeneration, modelling and drug testing has emphasized a need to create microenvironments with physiological features. Many studies have reported on how cardiomyocytes sense substrate stiffness and adapt their morphological and functional properties. However, these observations have raised new biological questions and a shared vision to translate it into a tissue or organ context is still elusive. In this review, we will focus on the relevance of substrates mimicking cardiac extracellular matrix (cECM) rigidity for the understanding of the biomechanical crosstalk between the extracellular and intracellular environment. The ability to opportunely modulate these pathways could be a key to regulate in vitro hiPSC-CM maturation. Therefore, both hiPSC-CM models and substrate stiffness appear as intriguing tools for the investigation of cECM-cell interactions. More understanding of these mechanisms may provide novel insights on how cECM affects cardiac cell function in the context of genetic cardiomyopathies., (Copyright © 2022. Published by Elsevier Ltd.)

Atrial dilation and atrial fibrillation (AF) are common in Hypertrophic CardioMyopathy (HCM) patients and associated with a worsening of prognosis. The pathogenesis of atrial myopathy in HCM remains poorly investigated and no specific association with genotype has been identified. By re-analysis of our cohort of thin-filament HCM patients (Coppini et al. 2014) AF was identified in 10% of patients with sporadic mutations in the cardiac Troponin T gene ( TNNT2 ), while AF occurrence was much higher (25-75%) in patients carrying specific "hot-spot" TNNT2 mutations. To determine the molecular basis of arrhythmia occurrence, two HCM mouse models expressing human TNNT2 variants (a "hot-spot" one, R92Q, and a "sporadic" one, E163R) were selected according to the different pathophysiological pathways previously demonstrated in ventricular tissue. Echocardiography studies showed a significant left atrial dilation in both models, but more pronounced in the R92Q. In E163R atrial trabeculae, in line with what previously observed in ventricular preparations, the energy cost of tension generation was markedly increased. However, no changes of twitch amplitude and kinetics were observed, and there was no atrial arrhythmic propensity. R92Q atrial trabeculae, instead, displayed normal ATP consumption but markedly increased myofilament calcium sensitivity, as previously observed in ventricular preparations. This was associated with reduced inotropic reserve and slower kinetics of twitch contractions and, importantly, with an increased occurrence of spontaneous beats and triggered contractions that represent an intrinsic arrhythmogenic mechanism promoting AF. The association of specific TNNT2 mutations with AF occurrence depends on the mutation-driven pathomechanism (i.e., increased atrial myofilament calcium sensitivity rather than increased myofilament tension cost) and may influence the individual response to treatment., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Pioner, Vitale, Gentile, Scellini, Piroddi, Cerbai, Olivotto, Tardiff, Coppini, Tesi, Poggesi and Ferrantini.)

The detection of parturition markers on archaeological pelvic bones is relevant for the reconstruction of the biological profiles of female individuals, in whose life history pregnancy represents a crucial biological event. During a preliminary study on a sample of 18 individuals from the medieval and post-medieval cemetery of San Biagio in Cittiglio (northern Italy), two skeletons exhibited evidence of noteworthy bony projections at the sacroiliac level. In clinical studies, these occurrences can be connected to several biological variables such as age, obesity, and multiple births, suggesting that they are a possible consequence of weight-bearing stresses. Here, we address two cases of accessory sacroiliac joints and the iliosacral complex found in two female individuals. The study is part of the anthropological analysis of the sample from the cemetery of Cittiglio (78 individuals have been investigated to date) and, in particular, of the examination of female and male pelves in order to highlight the expression and aspect of pelvic features in both sexes.

Abstract: This study aims at presenting a case of symmetrical and bilateral thinning observed in a skull belonging to the skeleton of a mature woman from the medieval cemetery of Caravate (north Italy). Macroscopical, radiological, and histological analyses were performed to investigate the condition. The analyses allowed us to detect a progressive loss of both the outer table and the diploe, and the sparing of the inner table. As a controversial condition in the clinical and paleopathological literature, this case poses some difficulties in discussing the differential diagnosis. However, the sex determination, estimation of the age-at-death and different characteristics observed at the level of the postcranial bones, in particular the fractures recorded on different vertebral bodies, allowed us to correlate the biparietal thinning found in this subject to ageing and osteoporosis., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 by Mutaz B. Habal, MD.)

Human atrial and ventricular contractions have distinct mechanical characteristics including speed of contraction, volume of blood delivered and the range of pressure generated. Notably, the ventricle expresses predominantly β-cardiac myosin while the atrium expresses mostly the α-isoform. In recent years exploration of the properties of pure α- & β-myosin isoforms have been possible in solution, in isolated myocytes and myofibrils. This allows us to consider the extent to which the atrial vs ventricular mechanical characteristics are defined by the myosin isoform expressed, and how the isoform properties are matched to their physiological roles. To do this we Outline the essential feature of atrial and ventricular contraction; Explore the molecular structural and functional characteristics of the two myosin isoforms; Describe the contractile behaviour of myocytes and myofibrils expressing a single myosin isoform; Finally we outline the outstanding problems in defining the differences between the atria and ventricles. This allowed us consider what features of contraction can and cannot be ascribed to the myosin isoforms present in the atria and ventricles., (© 2021. The Author(s).)

Myopalladin (MYPN) is a striated muscle-specific immunoglobulin domain-containing protein located in the sarcomeric Z-line and I-band. MYPN gene mutations are causative for dilated (DCM), hypertrophic, and restrictive cardiomyopathy. In a yeast two-hybrid screening, MYPN was found to bind to titin in the Z-line, which was confirmed by microscale thermophoresis. Cardiac analyses of MYPN knockout (MKO) mice showed the development of mild cardiac dilation and systolic dysfunction, associated with decreased myofibrillar isometric tension generation and increased resting tension at longer sarcomere lengths. MKO mice exhibited a normal hypertrophic response to transaortic constriction (TAC), but rapidly developed severe cardiac dilation and systolic dysfunction, associated with fibrosis, increased fetal gene expression, higher intercalated disc fold amplitude, decreased calsequestrin-2 protein levels, and increased desmoplakin and SORBS2 protein levels. Cardiomyocyte analyses showed delayed Ca 2+ release and reuptake in unstressed MKO mice as well as reduced Ca 2+ spark amplitude post-TAC, suggesting that altered Ca 2+ handling may contribute to the development of DCM in MKO mice., Competing Interests: MF, DY, RM, AG, NP, BS, RC, FD, JZ, AF, SN, SS, CT, DC, WL, RP, CP, MG, MB No competing interests declared, PC The authors declare that no competing interests exist., (© 2021, Filomena et al.)

At the end of the nineteenth century, recurrent cases of rib fractures were recorded in psychiatric asylums, opening a long chapter of discussions about the application of the 'non-restraint' system. Here we present a brief discussion of an article written by Enrico Morselli about five cases of rib fractures in the mental asylum of Reggio Emilia, in 1874-5. Morselli, a supporter of the ideas of 'non-restraint', suggested a common pathological cause. His analysis proposed the osteomalacic condition as the possible cause of fractured ribs, rejecting the accusations of violence by asylum attendants. The discussion also examines similar cases of the same period, making rib fractures the means through which the issue of management of the insane was addressed.

Mavacamten (MYK-461) is a small-molecule allosteric inhibitor of sarcomeric myosins being used in preclinical/clinical trials for hypertrophic cardiomyopathy treatment. A better understanding of its impact on force generation in intact or skinned striated muscle preparations, especially for human cardiac muscle, has been hindered by diffusional barriers. These limitations have been overcome by mechanical experiments using myofibrils subject to perturbations of the contractile environment by sudden solution changes. Here, we characterize the action of mavacamten in human ventricular myofibrils compared with fast skeletal myofibrils from rabbit psoas. Mavacamten had a fast, fully reversible, and dose-dependent negative effect on maximal Ca2+-activated isometric force at 15°C, which can be explained by a sudden decrease in the number of heads functionally available for interaction with actin. It also decreased the kinetics of force development in fast skeletal myofibrils, while it had no effect in human ventricular myofibrils. For both myofibril types, the effects of mavacamten were independent from phosphate in the low-concentration range. Mavacamten did not alter force relaxation of fast skeletal myofibrils, but it significantly accelerated the relaxation of human ventricular myofibrils. Lastly, mavacamten had no effect on resting tension but inhibited the ADP-stimulated force in the absence of Ca2+. Altogether, these effects outline a motor isoform-specific dependence of the inhibitory effect of mavacamten on force generation, which is mediated by a reduction in the availability of strongly actin-binding heads. Mavacamten may thus alter the interplay between thick and thin filament regulation mechanisms of contraction in association with the widely documented drug effect of stabilizing myosin motor heads into autoinhibited states., (© 2021 Scellini et al.)

The highly organized transverse T-tubule membrane system represents the ultrastructural substrate for excitation-contraction coupling in ventricular myocytes. While the architecture and function of T-tubules have been well described in animal models, there is limited morpho-functional data on T-tubules in human myocardium. Hypertrophic cardiomyopathy (HCM) is a primary disease of the heart muscle, characterized by different clinical presentations at the various stages of its progression. Most HCM patients, indeed, show a compensated hypertrophic disease ("non-failing hypertrophic phase"), with preserved left ventricular function, and only a small subset of individuals evolves into heart failure ("end stage HCM"). In terms of T-tubule remodeling, the "end-stage" disease does not differ from other forms of heart failure. In this review we aim to recapitulate the main structural features of T-tubules during the "non-failing hypertrophic stage" of human HCM by revisiting data obtained from human myectomy samples. Moreover, by comparing pathological changes observed in myectomy samples with those introduced by acute (experimentally induced) detubulation, we discuss the role of T-tubular disruption as a part of the complex excitation-contraction coupling remodeling process that occurs during disease progression. Lastly, we highlight how T-tubule morpho-functional changes may be related to patient genotype and we discuss the possibility of a primitive remodeling of the T-tubule system in rare HCM forms associated with genes coding for proteins implicated in T-tubule structural integrity, formation and maintenance., (© 2020. The Author(s).)

Full muscle relaxation happens when [Ca 2+ ] falls below the threshold for force activation. Several experimental models, from whole muscle organs and intact muscle down to skinned fibers, have been used to explore the cascade of kinetic events leading to mechanical relaxation. The use of single myofibrils together with fast solution switching techniques, has provided new information about the role of cross-bridge (CB) dissociation in the time course of isometric force decay. Myofibril's relaxation is biphasic starting with a slow seemingly linear phase, with a rate constant, slow k REL , followed by a fast mono-exponential phase. Sarcomeres remain isometric during the slow force decay that reflects CB detachment under isometric conditions while the final fast relaxation phase begins with a sudden give of few sarcomeres and is then dominated by intersarcomere dynamics. Based on a simple two-state model of the CB cycle, myofibril slow k REL represents the apparent forward rate with which CBs leave force generating states (g app ) under isometric conditions and correlates with the energy cost of tension generation (ATPase/tension ratio); in short slow k REL  ~ g app  ~ tension cost. The validation of this relationship is obtained by simultaneously measuring maximal isometric force and ATP consumption in skinned myocardial strips that provide an unambiguous determination of the relation between contractile and energetic properties of the sarcomere. Thus, combining kinetic experiments in isolated myofibrils and mechanical and energetic measurements in multicellular cardiac strips, we are able to provide direct evidence for a positive linear correlation between myofibril isometric relaxation kinetics (slow k REL ) and the energy cost of force production both measured in preparations from the same cardiac sample. This correlation remains true among different types of muscles with different ATPase activities and also when CB kinetics are altered by cardiomyopathy-related mutations. Sarcomeric mutations associated to hypertrophic cardiomyopathy (HCM), a primary cardiac disorder caused by mutations in genes encoding sarcomeric proteins, have been often found to accelerate CB turnover rate and increase the energy cost of myocardial contraction. Here we review data showing that faster CB detachment results in a proportional increase in the energetic cost of tension generation in heart samples from both HCM patients and mouse models of the disease.