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1.
Circ Res ; 132(5): 628-644, 2023 03 03.
Article in English | MEDLINE | ID: mdl-36744470

ABSTRACT

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 Ca2+ 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.


Subject(s)
Cardiomyopathy, Hypertrophic , Induced Pluripotent Stem Cells , Humans , Calcium/metabolism , Carrier Proteins/genetics , Carrier Proteins/metabolism , Induced Pluripotent Stem Cells/metabolism , Cardiomyopathy, Hypertrophic/pathology , Myocardium/metabolism , Myocytes, Cardiac/metabolism , Mutation , Calcium, Dietary/metabolism , Cytoskeletal Proteins/genetics
2.
J Mol Cell Cardiol ; 166: 36-49, 2022 05.
Article in English | MEDLINE | ID: mdl-35139328

ABSTRACT

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.


Subject(s)
Induced Pluripotent Stem Cells , Myocytes, Cardiac , Cell Communication , Cell Differentiation , Extracellular Matrix/metabolism , Humans , Induced Pluripotent Stem Cells/metabolism , Myocytes, Cardiac/metabolism
3.
Cell Mol Life Sci ; 78(23): 7309-7337, 2021 Dec.
Article in English | MEDLINE | ID: mdl-34704115

ABSTRACT

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 ß-cardiac myosin while the atrium expresses mostly the α-isoform. In recent years exploration of the properties of pure α- & ß-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.


Subject(s)
Heart Atria/metabolism , Heart Ventricles/metabolism , Myocardial Contraction/physiology , Myocytes, Cardiac/physiology , Ventricular Myosins/metabolism , Amino Acid Sequence , Atrial Function/physiology , Blood Pressure/physiology , Humans , Myocytes, Cardiac/metabolism , Myofibrils/physiology , Protein Domains , Protein Isoforms , Ventricular Function/physiology
4.
J Craniofac Surg ; 33(1): 70-75, 2022.
Article in English | MEDLINE | ID: mdl-34260447

ABSTRACT

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.


Subject(s)
Fractures, Bone , Osteoporosis , Female , Head , History, Medieval , Humans , Italy , Paleopathology , Skull/diagnostic imaging
5.
J Muscle Res Cell Motil ; 42(2): 305-322, 2021 06.
Article in English | MEDLINE | ID: mdl-33222034

ABSTRACT

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.


Subject(s)
Cardiomyopathy, Hypertrophic , Sarcolemma , Animals , Cardiomyopathy, Hypertrophic/genetics , Excitation Contraction Coupling , Humans , Myocardium , Myocytes, Cardiac
6.
J Muscle Res Cell Motil ; 42(1): 47-57, 2021 03.
Article in English | MEDLINE | ID: mdl-31745760

ABSTRACT

Full muscle relaxation happens when [Ca2+] 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 kREL, 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 kREL represents the apparent forward rate with which CBs leave force generating states (gapp) under isometric conditions and correlates with the energy cost of tension generation (ATPase/tension ratio); in short slow kREL ~ gapp ~ 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 kREL) 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.


Subject(s)
Myocardial Contraction/genetics , Sarcomeres/metabolism , Animals , Humans , Mice , Myocardium/metabolism
7.
Circ Res ; 124(8): e44-e54, 2019 04 12.
Article in English | MEDLINE | ID: mdl-30732554

ABSTRACT

RATIONALE: Despite major advances in cardiovascular medicine, heart disease remains a leading cause of death worldwide. However, the field of tissue engineering has been growing exponentially in the last decade and restoring heart functionality is now an affordable target; yet, new materials are still needed for effectively provide rapid and long-lasting interventions. Liquid crystalline elastomers (LCEs) are biocompatible polymers able to reversibly change shape in response to a given stimulus and generate movement. Once stimulated, LCEs can produce tension or movement like a muscle. However, so far their application in biology was limited by slow response times and a modest possibility to modulate tension levels during activation. OBJECTIVE: To develop suitable LCE-based materials to assist cardiac contraction. METHODS AND RESULTS: Thanks to a quick, simple, and versatile synthetic approach, a palette of biocompatible acrylate-based light-responsive LCEs with different molecular composition was prepared and mechanically characterized. Out of this, the more compliant one was selected. This material was able to contract for some weeks when activated with very low light intensity within a physiological environment. Its contraction was modulated in terms of light intensity, stimulation frequency, and ton/toff ratio to fit different contraction amplitude/time courses, including those of the human heart. Finally, LCE strips were mounted in parallel with cardiac trabeculae, and we demonstrated their ability to improve muscular systolic function, with no impact on diastolic properties. CONCLUSIONS: Our results indicated LCEs are promising in assisting cardiac mechanical function and developing a new generation of contraction assist devices.


Subject(s)
Biocompatible Materials , Elastomers , Heart-Assist Devices , Light , Liquid Crystals , Myocardial Contraction , Tissue Engineering/methods , Acrylates , Bioartificial Organs , Biocompatible Materials/chemical synthesis , Biophysical Phenomena , Cross-Linking Reagents/chemistry , Elastomers/chemical synthesis , Energy Transfer , Liquid Crystals/chemistry , Micro-Electrical-Mechanical Systems/methods , Organ Motion , Time Factors , Tissue Scaffolds/chemistry
8.
Hist Psychiatry ; 32(3): 350-358, 2021 09.
Article in English | MEDLINE | ID: mdl-33960229

ABSTRACT

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.


Subject(s)
Hospitals, Psychiatric/history , Restraint, Physical/adverse effects , Rib Fractures/history , Adult , Aged , Autopsy/history , Causality , Female , History, 19th Century , Humans , Larynx/injuries , Male , Mental Disorders/history , Middle Aged , Osteomalacia/history , Rib Fractures/etiology
9.
Int J Mol Sci ; 20(15)2019 Aug 03.
Article in English | MEDLINE | ID: mdl-31382622

ABSTRACT

Cardiomyocytes from human induced pluripotent stem cells (hiPSC-CMs) are the most promising human source with preserved genetic background of healthy individuals or patients. This study aimed to establish a systematic procedure for exploring development of hiPSC-CM functional output to predict genetic cardiomyopathy outcomes and identify molecular targets for therapy. Biomimetic substrates with microtopography and physiological stiffness can overcome the immaturity of hiPSC-CM function. We have developed a custom-made apparatus for simultaneous optical measurements of hiPSC-CM action potential and calcium transients to correlate these parameters at specific time points (day 60, 75 and 90 post differentiation) and under inotropic interventions. In later-stages, single hiPSC-CMs revealed prolonged action potential duration, increased calcium transient amplitude and shorter duration that closely resembled those of human adult cardiomyocytes from fresh ventricular tissue of patients. Thus, the major contribution of sarcoplasmic reticulum and positive inotropic response to ß-adrenergic stimulation are time-dependent events underlying excitation contraction coupling (ECC) maturation of hiPSC-CM; biomimetic substrates can promote calcium-handling regulation towards adult-like kinetics. Simultaneous optical recordings of long-term cultured hiPSC-CMs on biomimetic substrates favor high-throughput electrophysiological analysis aimed at testing (mechanistic hypothesis on) disease progression and pharmacological interventions in patient-derived hiPSC-CMs.


Subject(s)
Adrenergic beta-Antagonists/pharmacology , Calcium/metabolism , Cardiomyopathies/drug therapy , Induced Pluripotent Stem Cells/metabolism , Action Potentials/drug effects , Biomimetics , Cardiomyopathies/genetics , Cardiomyopathies/pathology , Cell Differentiation/drug effects , Cells, Cultured , Excitation Contraction Coupling/drug effects , Humans , Hydrogels/pharmacology , Induced Pluripotent Stem Cells/drug effects , Myocytes, Cardiac/drug effects , Myocytes, Cardiac/metabolism , Sarcoplasmic Reticulum/drug effects , Sarcoplasmic Reticulum/metabolism , Substrate Specificity
10.
Biophys J ; 112(2): 376-387, 2017 Jan 24.
Article in English | MEDLINE | ID: mdl-28122223

ABSTRACT

We investigated the functional impact of α-tropomyosin (Tm) substituted with one (D137L) or two (D137L/G126R) stabilizing amino acid substitutions on the mechanical behavior of rabbit psoas skeletal myofibrils by replacing endogenous Tm and troponin (Tn) with recombinant Tm mutants and purified skeletal Tn. Force recordings from myofibrils (15°C) at saturating [Ca2+] showed that Tm-stabilizing substitutions did not significantly affect the maximal isometric tension and the rates of force activation (kACT) and redevelopment (kTR). However, a clear effect was observed on force relaxation: myofibrils with D137L/G126R or D137L Tm showed prolonged durations of the slow phase of relaxation and decreased rates of the fast phase. Both Tm-stabilizing substitutions strongly decreased the slack sarcomere length (SL) at submaximal activating [Ca2+] and increased the steepness of the SL-passive tension relation. These effects were reversed by addition of 10 mM 2,3-butanedione 2-monoxime. Myofibrils also showed an apparent increase in Ca2+ sensitivity. Measurements of myofibrillar ATPase activity in the absence of Ca2+ showed a significant increase in the presence of these Tms, indicating that single and double stabilizing substitutions compromise the full inhibition of contraction in the relaxed state. These data can be understood with the three-state (blocked-closed-open) theory of muscle regulation, according to which the mutations increase the contribution of the active open state in the absence of Ca2+ (M-). Force measurements on myofibrils substituted with C-terminal truncated TnI showed similar compromised relaxation effects, indicating the importance of TnI-Tm interactions in maintaining the blocked state. It appears that reducing the flexibility of native Tm coiled-coil structure decreases the optimum interactions of the central part of Tm with the C-terminal region of TnI. This results in a shift away from the blocked state, allowing myosin binding and activity in the absence of Ca2+. This work provides a basis for understanding the effects of disease-producing mutations in muscle proteins.


Subject(s)
Amino Acid Substitution , Muscle Relaxation , Myofibrils/physiology , Tropomyosin/chemistry , Tropomyosin/metabolism , Animals , Calcium/metabolism , Humans , Muscle Relaxation/drug effects , Myofibrils/drug effects , Myofibrils/metabolism , Protein Stability , Psoas Muscles/cytology , Psoas Muscles/physiology , Rabbits , Sequence Deletion , Tropomyosin/genetics , Tropomyosin/pharmacology , Troponin I/genetics , Troponin I/metabolism
11.
J Muscle Res Cell Motil ; 38(3-4): 275-289, 2017 08.
Article in English | MEDLINE | ID: mdl-28918606

ABSTRACT

A basic goal in muscle research is to understand how the cyclic ATPase activity of cross-bridges is converted into mechanical force. A direct approach to study the chemo-mechanical coupling between Pi release and the force-generating step is provided by the kinetics of force response induced by a rapid change in [Pi]. Classical studies on fibres using caged-Pi discovered that rapid increases in [Pi] induce fast force decays dependent on final [Pi] whose kinetics were interpreted to probe a fast force-generating step prior to Pi release. However, this hypothesis was called into question by studies on skeletal and cardiac myofibrils subjected to Pi jumps in both directions (increases and decreases in [Pi]) which revealed that rapid decreases in [Pi] trigger force rises with slow kinetics, similar to those of calcium-induced force development and mechanically-induced force redevelopment at the same [Pi]. A possible explanation for this discrepancy came from imaging of individual sarcomeres in cardiac myofibrils, showing that the fast force decay upon increase in [Pi] results from so-called sarcomere 'give'. The slow force rise upon decrease in [Pi] was found to better reflect overall sarcomeres cross-bridge kinetics and its [Pi] dependence, suggesting that the force generation coupled to Pi release cannot be separated from the rate-limiting transition. The reasons for the different conclusions achieved in fibre and myofibril studies are re-examined as the recent findings on cardiac myofibrils have fundamental consequences for the coupling between Pi release, rate-limiting steps and force generation. The implications from Pi-induced force kinetics of myofibrils are discussed in combination with historical and recent models of the cross-bridge cycle.


Subject(s)
Adenosine Triphosphate/metabolism , Calcium/metabolism , Isometric Contraction/physiology , Muscle Strength/physiology , Sarcomeres/physiology , Animals , Humans , Kinetics , Phosphates
12.
Proc Natl Acad Sci U S A ; 111(42): 15196-201, 2014 Oct 21.
Article in English | MEDLINE | ID: mdl-25288764

ABSTRACT

Action potentials (APs), via the transverse axial tubular system (TATS), synchronously trigger uniform Ca(2+) release throughout the cardiomyocyte. In heart failure (HF), TATS structural remodeling occurs, leading to asynchronous Ca(2+) release across the myocyte and contributing to contractile dysfunction. In cardiomyocytes from failing rat hearts, we previously documented the presence of TATS elements which failed to propagate AP and displayed spontaneous electrical activity; the consequence for Ca(2+) release remained, however, unsolved. Here, we develop an imaging method to simultaneously assess TATS electrical activity and local Ca(2+) release. In HF cardiomyocytes, sites where T-tubules fail to conduct AP show a slower and reduced local Ca(2+) transient compared with regions with electrically coupled elements. It is concluded that TATS electrical remodeling is a major determinant of altered kinetics, amplitude, and homogeneity of Ca(2+) release in HF. Moreover, spontaneous depolarization events occurring in failing T-tubules can trigger local Ca(2+) release, resulting in Ca(2+) sparks. The occurrence of tubule-driven depolarizations and Ca(2+) sparks may contribute to the arrhythmic burden in heart failure.


Subject(s)
Calcium/metabolism , Heart Failure/metabolism , Muscle Cells/cytology , Myocytes, Cardiac/metabolism , Action Potentials/physiology , Animals , Calcium Signaling/physiology , Cells, Cultured , Green Fluorescent Proteins/metabolism , Heart Ventricles/cytology , Heart Ventricles/metabolism , Male , Myocardial Contraction/physiology , Rats , Rats, Wistar , Sarcoplasmic Reticulum/metabolism
14.
Proc Natl Acad Sci U S A ; 109(15): 5815-9, 2012 Apr 10.
Article in English | MEDLINE | ID: mdl-22451916

ABSTRACT

The plasma membrane of cardiac myocytes presents complex invaginations known as the transverse-axial tubular system (TATS). Despite TATS's crucial role in excitation-contraction coupling and morphological alterations found in pathological settings, TATS's electrical activity has never been directly investigated in remodeled tubular networks. Here we develop an ultrafast random access multiphoton microscope that, in combination with a customly synthesized voltage-sensitive dye, is used to simultaneously measure action potentials (APs) at multiple sites within the sarcolemma with submillisecond temporal and submicrometer spatial resolution in real time. We find that the tight electrical coupling between different sarcolemmal domains is guaranteed only within an intact tubular system. In fact, acute detachment by osmotic shock of most tubules from the surface sarcolemma prevents AP propagation not only in the disconnected tubules, but also in some of the tubules that remain connected with the surface. This indicates that a structural disorganization of the tubular system worsens the electrical coupling between the TATS and the surface. The pathological implications of this finding are investigated in failing hearts. We find that AP propagation into the pathologically remodeled TATS frequently fails and may be followed by local spontaneous electrical activity. Our findings provide insight on the relationship between abnormal TATS and asynchronous calcium release, a major determinant of cardiac contractile dysfunction and arrhythmias.


Subject(s)
Action Potentials/physiology , Cell Membrane/physiology , Heart Failure/physiopathology , Animals , Heart Failure/pathology , Male , Rats , Rats, Wistar
15.
J Physiol ; 592(15): 3257-72, 2014 Aug 01.
Article in English | MEDLINE | ID: mdl-24928957

ABSTRACT

The first mutation associated with hypertrophic cardiomyopathy (HCM) is the R403Q mutation in the gene encoding ß-myosin heavy chain (ß-MyHC). R403Q locates in the globular head of myosin (S1), responsible for interaction with actin, and thus motor function of myosin. Increased cross-bridge relaxation kinetics caused by the R403Q mutation might underlie increased energetic cost of tension generation; however, direct evidence is absent. Here we studied to what extent cross-bridge kinetics and energetics are related in single cardiac myofibrils and multicellular cardiac muscle strips of three HCM patients with the R403Q mutation and nine sarcomere mutation-negative HCM patients (HCMsmn). Expression of R403Q was on average 41 ± 4% of total MYH7 mRNA. Cross-bridge slow relaxation kinetics in single R403Q myofibrils was significantly higher (P < 0.0001) than in HCMsmn myofibrils (0.47 ± 0.02 and 0.30 ± 0.02 s(-1), respectively). Moreover, compared to HCMsmn, tension cost was significantly higher in the muscle strips of the three R403Q patients (2.93 ± 0.25 and 1.78 ± 0.10 µmol l(-1) s(-1) kN(-1) m(-2), respectively) which showed a positive linear correlation with relaxation kinetics in the corresponding myofibril preparations. This correlation suggests that faster cross-bridge relaxation kinetics results in an increase in energetic cost of tension generation in human HCM with the R403Q mutation compared to HCMsmn. Therefore, increased tension cost might contribute to HCM disease in patients carrying the R403Q mutation.


Subject(s)
Cardiac Myosins/genetics , Cardiomyopathy, Hypertrophic/physiopathology , Muscle Relaxation , Myocardial Contraction , Myosin Heavy Chains/genetics , Sarcomeres/physiology , Adenosine Triphosphate/metabolism , Adult , Aged , Cardiac Myosins/metabolism , Cardiomyopathy, Hypertrophic/genetics , Cardiomyopathy, Hypertrophic/metabolism , Female , Humans , Male , Middle Aged , Mutation, Missense , Myosin Heavy Chains/metabolism , Sarcomeres/metabolism
16.
Circulation ; 127(5): 575-84, 2013 Feb 05.
Article in English | MEDLINE | ID: mdl-23271797

ABSTRACT

BACKGROUND: Hypertrophic cardiomyopathy (HCM), the most common mendelian heart disorder, remains an orphan of disease-specific pharmacological treatment because of the limited understanding of cellular mechanisms underlying arrhythmogenicity and diastolic dysfunction. METHODS AND RESULTS: We assessed the electromechanical profile of cardiomyocytes from 26 HCM patients undergoing myectomy compared with those from nonfailing nonhypertrophic surgical patients by performing patch-clamp and intracellular Ca(2+) (Ca(2+)(i)) studies. Compared with controls, HCM cardiomyocytes showed prolonged action potential related to increased late Na(+) (I(NaL)) and Ca(2+) (I(CaL)) currents and decreased repolarizing K(+) currents, increased occurrence of cellular arrhythmias, prolonged Ca(2+)(i) transients, and higher diastolic Ca(2+)(i). Such changes were related to enhanced Ca(2+)/calmodulin kinase II (CaMKII) activity and increased phosphorylation of its targets. Ranolazine at therapeutic concentrations partially reversed the HCM-related cellular abnormalities via I(NaL) inhibition, with negligible effects in controls. By shortening the action potential duration in HCM cardiomyocytes, ranolazine reduced the occurrence of early and delayed afterdepolarizations. Finally, as a result of the faster kinetics of Ca(2+)(i) transients and the lower diastolic Ca(2+)(i), ranolazine accelerated the contraction-relaxation cycle of HCM trabeculae, ameliorating diastolic function. CONCLUSIONS: We highlighted a specific set of functional changes in human HCM myocardium that stem from a complex remodeling process involving alterations of CaMKII-dependent signaling, rather than being a direct consequence of the causal sarcomeric mutations. Among the several ion channel and Ca(2+)(i) handling proteins changes identified, an enhanced I(NaL) seems to be a major contributor to the electrophysiological and Ca(2+)(i) dynamic abnormalities of ventricular myocytes and trabeculae from patients with HCM, suggesting potential therapeutic implications of I(NaL) inhibition.


Subject(s)
Acetanilides/pharmacology , Action Potentials/drug effects , Cardiomyopathy, Hypertrophic/physiopathology , Myocytes, Cardiac/drug effects , Piperazines/pharmacology , Sodium Channel Blockers/pharmacology , Action Potentials/physiology , Adult , Calcium/metabolism , Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism , Case-Control Studies , Diastole/drug effects , Diastole/physiology , Female , Humans , Male , Middle Aged , Myocytes, Cardiac/physiology , Patch-Clamp Techniques , Potassium Channels/drug effects , Potassium Channels/physiology , Ranolazine , Signal Transduction/drug effects , Signal Transduction/physiology
17.
Am J Physiol Heart Circ Physiol ; 307(2): H252-8, 2014 Jul 15.
Article in English | MEDLINE | ID: mdl-24858848

ABSTRACT

Little is known about the function of the cytoplasmic histone deacetylase HDAC6 in striated muscle. Here, we addressed the role of HDAC6 in cardiac and skeletal muscle remodeling induced by the peptide hormone angiotensin II (ANG II), which plays a central role in blood pressure control, heart failure, and associated skeletal muscle wasting. Comparable with wild-type (WT) mice, HDAC6 null mice developed cardiac hypertrophy and fibrosis in response to ANG II. However, whereas WT mice developed systolic dysfunction upon treatment with ANG II, cardiac function was maintained in HDAC6 null mice treated with ANG II for up to 8 wk. The cardioprotective effect of HDAC6 deletion was mimicked in WT mice treated with the small molecule HDAC6 inhibitor tubastatin A. HDAC6 null mice also exhibited improved left ventricular function in the setting of pressure overload mediated by transverse aortic constriction. HDAC6 inhibition appeared to preserve systolic function, in part, by enhancing cooperativity of myofibrillar force generation. Finally, we show that HDAC6 null mice are resistant to skeletal muscle wasting mediated by chronic ANG-II signaling. These findings define novel roles for HDAC6 in striated muscle and suggest potential for HDAC6-selective inhibitors for the treatment of cardiac dysfunction and muscle wasting in patients with heart failure.


Subject(s)
Angiotensin II , Cardiomegaly/enzymology , Heart Failure/enzymology , Histone Deacetylases/metabolism , Muscle, Skeletal/enzymology , Muscular Atrophy/enzymology , Myocardium/enzymology , Animals , Cardiomegaly/chemically induced , Cardiomegaly/pathology , Cardiomegaly/physiopathology , Cardiomegaly/prevention & control , Disease Models, Animal , Fibrosis , Heart Failure/chemically induced , Heart Failure/pathology , Heart Failure/physiopathology , Heart Failure/prevention & control , Histone Deacetylase 6 , Histone Deacetylase Inhibitors/pharmacology , Histone Deacetylases/deficiency , Histone Deacetylases/genetics , Hydroxamic Acids/pharmacology , Indoles/pharmacology , Male , Mice , Mice, Knockout , Muscle, Skeletal/drug effects , Muscle, Skeletal/pathology , Muscular Atrophy/chemically induced , Muscular Atrophy/pathology , Muscular Atrophy/prevention & control , Myocardium/pathology , Signal Transduction , Stroke Volume , Systole , Time Factors , Ventricular Function, Left , Ventricular Remodeling
18.
Brain ; 136(Pt 6): 1718-31, 2013 Jun.
Article in English | MEDLINE | ID: mdl-23715096

ABSTRACT

Nebulin--a giant sarcomeric protein--plays a pivotal role in skeletal muscle contractility by specifying thin filament length and function. Although mutations in the gene encoding nebulin (NEB) are a frequent cause of nemaline myopathy, the most common non-dystrophic congenital myopathy, the mechanisms by which mutations in NEB cause muscle weakness remain largely unknown. To better understand these mechanisms, we have generated a mouse model in which Neb exon 55 is deleted (Neb(ΔExon55)) to replicate a founder mutation seen frequently in patients with nemaline myopathy with Ashkenazi Jewish heritage. Neb(ΔExon55) mice are born close to Mendelian ratios, but show growth retardation after birth. Electron microscopy studies show nemaline bodies--a hallmark feature of nemaline myopathy--in muscle fibres from Neb(ΔExon55) mice. Western blotting studies with nebulin-specific antibodies reveal reduced nebulin levels in muscle from Neb(ΔExon55) mice, and immunofluorescence confocal microscopy studies with tropomodulin antibodies and phalloidin reveal that thin filament length is significantly reduced. In line with reduced thin filament length, the maximal force generating capacity of permeabilized muscle fibres and single myofibrils is reduced in Neb(ΔExon55) mice with a more pronounced reduction at longer sarcomere lengths. Finally, in Neb(ΔExon55) mice the regulation of contraction is impaired, as evidenced by marked changes in crossbridge cycling kinetics and by a reduction of the calcium sensitivity of force generation. A novel drug that facilitates calcium binding to the thin filament significantly augmented the calcium sensitivity of submaximal force to levels that exceed those observed in untreated control muscle. In conclusion, we have characterized the first nebulin-based nemaline myopathy model, which recapitulates important features of the phenotype observed in patients harbouring this particular mutation, and which has severe muscle weakness caused by thin filament dysfunction.


Subject(s)
Disease Models, Animal , Exons/genetics , Muscle Proteins/genetics , Myopathies, Nemaline/genetics , Severity of Illness Index , Animals , Gene Deletion , Humans , Mice , Mice, Inbred C57BL , Mice, Transgenic , Muscle Weakness/genetics , Muscle Weakness/pathology , Myopathies, Nemaline/pathology
19.
Int J Paleopathol ; 45: 1-6, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38377784

ABSTRACT

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.


Subject(s)
Calcinosis , Leiomyoma , Uterine Neoplasms , Humans , Female , Leiomyoma/history , Leiomyoma/pathology , Italy , Uterine Neoplasms/pathology , Uterine Neoplasms/history , Calcinosis/pathology , Calcinosis/history , History, 18th Century , Paleopathology , Diagnosis, Differential
20.
Anthropol Anz ; 81(2): 209-218, 2024 Mar 21.
Article in English | MEDLINE | ID: mdl-37869940

ABSTRACT

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, 18th-19th 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.


Subject(s)
Cemeteries , Ossification, Heterotopic , Temporal Bone/abnormalities , Male , Adult , Humans , Temporal Bone/pathology , Temporal Bone/surgery , Ossification, Heterotopic/pathology , Ossification, Heterotopic/surgery , Autopsy
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