Unlocking cardiac motion: assessing software and machine learning for single-cell and cardioid kinematic insights

The heart coordinates its functional parameters for optimal beat-to-beat mechanical activity. Reliable detection and quantification of these parameters still represent a hot topic in cardiovascular research. Nowadays, computer vision allows the development of open-source algorithms to measure cellular kinematics. However, the analysis software can vary based on analyzed specimens. In this study, we compared different software performances in in-silico model, in-vitro mouse adult ventricular cardiomyocytes and cardioids. We acquired in-vitro high-resolution videos during suprathreshold stimulation at 0.5-1-2 Hz, adapting the protocol for the cardioids. Moreover, we exposed the samples to inotropic and depolarizing substances. We analyzed in-silico and in-vitro videos by (i) MUSCLEMOTION, the gold standard among open-source software; (ii) CONTRACTIONWAVE, a recently developed tracking software; and (iii) ViKiE, an in-house customized video kinematic evaluation software. We enriched the study with three machine-learning algorithms to test the robustness of the motion-tracking approaches. Our results revealed that all software produced comparable estimations of cardiac mechanical parameters. For instance, in cardioids, beat duration measurements at 0.5 Hz were 1053.58 ms (MUSCLEMOTION), 1043.59 ms (CONTRACTIONWAVE), and 937.11 ms (ViKiE). ViKiE exhibited higher sensitivity in exposed samples due to its localized kinematic analysis, while MUSCLEMOTION and CONTRACTIONWAVE offered temporal correlation, combining global assessment with time-efficient analysis. Finally, machine learning reveals greater accuracy when trained with MUSCLEMOTION dataset in comparison with the other software (accuracy > 83%). In conclusion, our findings provide valuable insights for the accurate selection and integration of software tools into the kinematic analysis pipeline, tailored to the experimental protocol.

Cardiac Aging Is Promoted by Pseudohypoxia Increasing p300-Induced Glycolysis

BACKGROUND

Heart failure is typical in the elderly. Metabolic remodeling of cardiomyocytes underlies inexorable deterioration of cardiac function with aging: glycolysis increases at the expense of oxidative phosphorylation, causing an energy deficit contributing to impaired contractility. Better understanding of the mechanisms of this metabolic switching could be critical for reversing the condition.

METHODS

To investigate the role of 3 histone modifications (H3K27ac, H3K27me3, and H3K4me1) in the metabolic remodeling occurring in the aging heart, we cross-compared epigenomic, transcriptomic, and metabolomic data from mice of different ages. In addition, the role of the transcriptional coactivator p300 (E1A-associated binding protein p300)/CBP (CREB binding protein) in cardiac aging was investigated using a specific inhibitor of this histone acetyltransferase enzyme.

RESULTS

We report a set of species-conserved enhancers associated with transcriptional changes underlying age-related metabolic remodeling in cardiomyocytes. Activation of the enhancer region of Hk2-a key glycolysis pathway gene-was fostered in old age-onset mouse heart by pseudohypoxia, wherein hypoxia-related genes are expressed under normal O2 levels, via increased activity of P300/CBP. Pharmacological inhibition of this transcriptional coactivator before the onset of cardiac aging led to a more aerobic, less glycolytic, metabolic state, improved heart contractility, and overall blunting of cardiac decline.

CONCLUSIONS

Taken together, our results suggest how epigenetic dysregulation of glycolysis pathway enhancers could potentially be targeted to treat heart failure in the elderly.

Video analysis of ex vivo beating hearts during preservation on the TransMedics® organ care system

Background

Reliable biomarkers for assessing the viability of the donor hearts undergoing ex vivo perfusion remain elusive. A unique feature of normothermic ex vivo perfusion on the TransMedics® Organ Care System (OCS™) is that the donor heart is maintained in a beating state throughout the preservation period. We applied a video algorithm for an in vivo assessment of cardiac kinematics, video kinematic evaluation (Vi.Ki.E.), to the donor hearts undergoing ex vivo perfusion on the OCS™ to assess the feasibility of applying this algorithm in this setting.

Methods

Healthy donor porcine hearts (n = 6) were procured from Yucatan pigs and underwent 2 h of normothermic ex vivo perfusion on the OCS™ device. During the preservation period, serial high-resolution videos were captured at 30 frames per second. Using Vi.Ki.E., we assessed the force, energy, contractility, and trajectory parameters of each heart.

Results

There were no significant changes in any of the measured parameters of the heart on the OCS™ device over time as judged by linear regression analysis. Importantly, there were no significant changes in contractility during the duration of the preservation period (time 0-30 min, 918 ± 430 px/s; time 31-60 min, 1,386 ± 603 px/s; time 61-90 min, 1,299 ± 617 px/s; time 91-120 min, 1,535 ± 728 px/s). Similarly, there were no significant changes in the force, energy, or trajectory parameters. Post-transplantation echocardiograms demonstrated robust contractility of each allograft.

Conclusion

Vi.Ki.E. assessment of the donor hearts undergoing ex vivo perfusion is feasible on the TransMedics OCS™, and we observed that the donor hearts maintain steady kinematic measurements throughout the duration.

Age-related increases in cardiac excitability, refractoriness and impulse conduction favor arrhythmogenesis in male rats

The effects of excitability, refractoriness, and impulse conduction have been independently related to enhanced arrhythmias in the aged myocardium in experimental and clinical studies. However, their combined arrhythmic effects in the elderly are not yet completely understood. Hence, the aim of the present work is to relate relevant cardiac electrophysiological parameters to enhanced arrhythmia vulnerability in the in vivo senescent heart. We used multiple-lead epicardial potential mapping in control (9-month-old) and aged (24-month-old) rat hearts. Cardiac excitability and refractoriness were evaluated at numerous epicardial test sites by means of the strength-duration curve and effective refractory period, respectively. During sinus rhythm, durations of electrogram intervals and waves were prolonged in the senescent heart, compared with control, demonstrating a latency in tissue activation and recovery. During ventricular pacing, cardiac excitability, effective refractory period, and dispersion of refractoriness increased in the aged animal. This scenario was accompanied by impairment of impulse propagation. Moreover, both spontaneous and induced arrhythmias were increased in senescent cardiac tissue. Histopathological evaluation of aged heart specimens revealed connective tissue deposition and perinuclear myocytolysis in the atria, while scattered microfoci of interstitial fibrosis were mostly present in the ventricular subendocardium. This work suggests that enhanced arrhythmogenesis in the elderly is a multifactorial process due to the joint increase in excitability and dispersion of refractoriness in association with enhanced conduction inhomogeneity. The knowledge of these electrophysiological changes will possibly contribute to improved prevention of the age-associated increase in cardiac arrhythmias.

Three-Dimensional Bioprinting of Organoid-Based Scaffolds (OBST) for Long-Term Nanoparticle Toxicology Investigation

The toxicity of nanoparticles absorbed through contact or inhalation is one of the major concerns for public health. It is mandatory to continually evaluate the toxicity of nanomaterials. In vitro nanotoxicological studies are conventionally limited by the two dimensions. Although 3D bioprinting has been recently adopted for three-dimensional culture in the context of drug release and tissue regeneration, little is known regarding its use for nanotoxicology investigation. Therefore, aiming to simulate the exposure of lung cells to nanoparticles, we developed organoid-based scaffolds for long-term studies in immortalized cell lines. We printed the viscous cell-laden material via a customized 3D bioprinter and subsequently exposed the scaffold to either 40 nm latex-fluorescent or 11–14 nm silver nanoparticles. The number of cells significantly increased on the 14th day in the 3D environment, from 5 × 105 to 1.27 × 106, showing a 91% lipid peroxidation reduction over time and minimal cell death observed throughout 21 days. Administered fluorescent nanoparticles can diffuse throughout the 3D-printed scaffolds while this was not the case for the unprinted ones. A significant increment in cell viability from 3D vs. 2D cultures exposed to silver nanoparticles has been demonstrated. This shows toxicology responses that recapitulate in vivo experiments, such as inhaled silver nanoparticles. The results open a new perspective in 3D protocols for nanotoxicology investigation supporting 3Rs.

Nocturnal Heart Rate Variability Might Help in Predicting Severe Obstructive Sleep-Disordered Breathing

Obstructive sleep apnea (OSA) can have long-term cardiovascular and metabolic effects. The identification of OSA-related impairments would provide diagnostic and prognostic value. Heart rate variability (HRV) as a measure of cardiac autonomic regulation is a promising candidate marker of OSA and OSA-related conditions. We took advantage of the Physionet Apnea-ECG database for two purposes. First, we performed time- and frequency-domain analysis of nocturnal HRV on each recording of this database to evaluate the cardiac autonomic regulation in patients with nighttime sleep breathing disorders. Second, we conducted a logistic regression analysis (backward stepwise) to identify the HRV indices able to predict the apnea–hypopnea index (AHI) categories (i.e., “Severe OSA”, AHI ≥ 30; “Moderate-Mild OSA”, 5 ≥ AHI < 30; and “Normal”, AHI < 5). Compared to the “Normal”, the “Severe OSA” group showed lower high-frequency power in normalized units (HFnu) and higher low-frequency power in normalized units (LFnu). The standard deviation of normal R–R intervals (SDNN) and the root mean square of successive R–R interval differences (RMSSD) were independently associated with sleep-disordered breathing. Our findings suggest altered cardiac autonomic regulation with a reduced parasympathetic component in OSA patients and suggest a role of nighttime HRV in the characterization and identification of sleep breathing disorders.

Maternal air pollution exposure during the first trimester of pregnancy and markers of inflammation and endothelial dysfunction

BACKGROUND

Maternal exposure to air pollutants has been associated with pregnancy complications and adverse birth outcomes. Endothelial dysfunction, an imbalance in vascular function, during pregnancy is considered a key element in the development of pre-eclampsia. Environmental exposure to particulate matter (PM) during the first trimester of pregnancy might increase maternal inflammatory status thus affecting fetal growth, possibly leading to preterm delivery.

OBJECTIVES

The purpose of the study was to evaluate possible effects of PM₁₀ and PM_2.5 exposure on fetal growth in healthy pregnant women at the end of the first trimester of pregnancy by investigating the relationship between circulating biomarkers of inflammation (IL-6), early systemic prothrombotic effects (CRP, plasma fibrinogen, PAI-1) and endothelial dysfunction (sICAM-1 and sVCAM-1).

METHODS

295 pregnant women were recruited. Individual PM exposure was assigned to each subject by calculating the mean of PM₁₀ and PM_2.5 daily values observed during the 30, 60, and 90 days preceding enrolment (long-term) and single lag days back to fourteen days (short-term), and circulating plasma biomarkers were determined.

RESULTS

For long-term exposure, we observed an increase in sVCAM-1 and a decrease of PAI-1 levels for each 10 μg/m³ increase in PM₁₀ concentration. Decreases in IL-6 and CRP levels were associated with each 10 μg/m³ PM_2.5 increase. For short-term exposure, the levels of sVCAM-1 and PAI-1 were found to be associated with PM₁₀ exposure, whereas fibrinogen levels were associated with PM_2.5 exposure. Maternal plasmatic fibrinogen levels were negatively associated with the crown-rump length (p-value = 0.008).

DISCUSSION

The present study showed that both long- and short-term exposures to PM are associated with changes in circulating levels of biomarkers in pregnant women reflecting systemic inflammation and endothelial dysfunction/activation. Our findings support the hypothesis that inflammation and endothelial dysfunction might have a central role in modulating the detrimental effects of air pollution exposure during pregnancy.

Cell Shortening and Calcium Homeostasis Analysis in Adult Cardiomyocytes via a New Software Tool

Intracellular calcium (Ca2+) is the central regulator of heart contractility. Indeed, it couples the electrical signal, which pervades the myocardium, with cardiomyocytes contraction. Moreover, alterations in calcium management are the main factors contributing to the mechanical and electrical dysfunction observed in failing hearts. So, simultaneous analysis of the contractile function and intracellular Ca2+ is indispensable to evaluate cardiomyocytes activity. Intracellular Ca2+ variations and fraction shortening are commonly studied with fluorescent Ca2+ indicator dyes associated with microscopy techniques. However, tracking and dealing with multiple files manually is time-consuming and error-prone and often requires expensive apparatus and software. Here, we announce a new, user-friendly image processing and analysis tool, based on ImageJ-Fiji/MATLAB® software, to evaluate the major cardiomyocyte functional parameters. We succeeded in analyzing fractional cell shortening, Ca2+ transient amplitude, and the kinematics/dynamics parameters of mouse isolated adult cardiomyocytes. The proposed method can be applied to evaluate changes in the Ca2+ cycle and contractile behavior in genetically or pharmacologically induced disease models, in drug screening and other common applications to assess mammalian cardiomyocyte functions.

Synthetic recovery of impulse propagation in myocardial infarction via silicon carbide semiconductive nanowires

Myocardial infarction causes 7.3 million deaths worldwide, mostly for fibrillation that electrically originates from the damaged areas of the left ventricle. Conventional cardiac bypass graft and percutaneous coronary interventions allow reperfusion of the downstream tissue but do not counteract the bioelectrical alteration originated from the infarct area. Genetic, cellular, and tissue engineering therapies are promising avenues but require days/months for permitting proper functional tissue regeneration. Here we engineered biocompatible silicon carbide semiconductive nanowires that synthetically couple, via membrane nanobridge formations, isolated beating cardiomyocytes over distance, restoring physiological cell-cell conductance, thereby permitting the synchronization of bioelectrical activity in otherwise uncoupled cells. Local in-situ multiple injections of nanowires in the left ventricular infarcted regions allow rapid reinstatement of impulse propagation across damaged areas and recover electrogram parameters and conduction velocity. Here we propose this nanomedical intervention as a strategy for reducing ventricular arrhythmia after acute myocardial infarction.

Silicon-based materials have the ability to support bioelectrical activity. Here the authors show how injectable silicon carbide nanowires reduce arrhythmias and rapidly restore conduction in a myocardial infarction model.

Heart rate variability in neonatal seizures: Investigation and implications for management

Many factors acting during the neonatal period can affect neurological development of the infant. Neonatal seizures (NS) that frequently occur in the immature brain may influence autonomic maturation and lead to detectable cardiovascular signs. These autonomic manifestations can also have significant diagnostic and prognostic value. The analysis of Heart Rate Variability (HRV) represents the most used and feasible method to evaluate cardiac autonomic regulation. This narrative review summarizes studies investigating HRV dynamics in newborns with seizures, with the aim of highlighting the potential utility of HRV measures for seizure detection and management. While HRV analysis in critically ill newborns is influenced by many potential confounders, we suggest that it can enhance the ability to better diagnose seizures in the clinical setting. We present potential applications of the analysis of HRV, which could have a useful future role, beyond the research setting.

Exposure to nanoparticles derived from diesel particulate filter equipped engine increases vulnerability to arrhythmia in rat hearts

Air pollution is well recognized as a central player in cardiovascular disease. Exhaust particulate from diesel engines (DEP) is rich in nanoparticles and may contribute to the health effects of particulate matter in the environment. Moreover, diesel soot emitted by modern engines denotes defective surfaces alongside chemically-reactive sites increasing soot cytotoxicity. We recently demonstrated that engineered nanoparticles can cross the air/blood barrier and are capable to reach the heart. We hypothesize that DEP nanoparticles are pro-arrhythmogenic by direct interaction with cardiac cells. We evaluated the internalization kinetics and the effects of DEP, collected from Euro III (DEPe3, in the absence of Diesel Particulate Filter, DPF) and Euro IV (DEPe4, in the presence of DPF) engines, on alveolar and cardiac cell lines and on in situ rat hearts following DEP tracheal instillation. We observed significant differences in DEP size, metal and organic compositions derived from both engines. DEPe4 comprised ultrafine particles (<100 nm) and denoted a more pronounced toxicological outcome compared to DEPe3. In cardiomyocytes, particle internalization is fastened for DEPe4 compared to DEPe3. The in-vivo epicardial recording shows significant alteration of EGs parameters in both groups. However, the DEPe4-instilled group showed, compared to DEPe3, a significant increment of the effective refractory period, cardiac conduction velocity, and likelihood of arrhythmic events, with a significant increment of membrane lipid peroxidation but no increment in inflammation biomarkers. Our data suggest that DEPe4, possibly due to ultrafine nanoparticles, is rapidly internalized by cardiomyocytes resulting in an acute susceptibility to cardiac electrical disorder and arrhythmias that could accrue from cellular toxicity. Since the postulated transfer of nanoparticles from the lung to myocardial cells has not been investigated it remains open whether the effects on the cardiovascular function are the result of lung inflammatory reactions or due to particles that have reached the heart.

Myocardial hypoxic stress mediates functional cardiac extracellular vesicle release

AIMS

Increased shedding of extracellular vesicles (EVs)-small, lipid bilayer-delimited particles with a role in paracrine signalling-has been associated with human pathologies, e.g. atherosclerosis, but whether this is true for cardiac diseases is unknown.

METHODS AND RESULTS

Here, we used the surface antigen CD172a as a specific marker of cardiomyocyte (CM)-derived EVs; the CM origin of CD172a+ EVs was supported by their content of cardiac-specific proteins and heart-enriched microRNAs. We found that patients with aortic stenosis, ischaemic heart disease, or cardiomyopathy had higher circulating CD172a+ cardiac EV counts than did healthy subjects. Cellular stress was a major determinant of EV release from CMs, with hypoxia increasing shedding in in vitro and in vivo experiments. At the functional level, EVs isolated from the supernatant of CMs derived from human-induced pluripotent stem cells and cultured in a hypoxic atmosphere elicited a positive inotropic response in unstressed CMs, an effect we found to be dependent on an increase in the number of EVs expressing ceramide on their surface. Of potential clinical relevance, aortic stenosis patients with the highest counts of circulating cardiac CD172a+ EVs had a more favourable prognosis for transcatheter aortic valve replacement than those with lower counts.

CONCLUSION

We identified circulating CD172a+ EVs as cardiac derived, showing their release and function and providing evidence for their prognostic potential in aortic stenosis patients.

Right ventricular functional recovery depends on timing of pulmonary valve replacement in tetralogy of Fallot: a video kinematic study

OBJECTIVES

Indications for and timing of pulmonary valve replacement (PVR) after tetralogy of Fallot repair are controversial. Among magnetic resonance imaging indices proposed to time valve replacement, a right ventricular (RV) end-diastolic volume index greater than 160 ml/m2 is often used. Recent evidence suggests that this value may still identify patients with irreversible RV dysfunction, thus hindering recovery. Our goal was to define, using intraoperative video kinematic evaluation, whether a relationship exists between timing of PVR and early functional recovery after surgery.

METHODS

Between November 2016 and November 2018, a total of 12 consecutive patients aged 27.1 ± 19.1 years underwent PVR on average 22.2 ± 13.3 years after tetralogy of Fallot repair. Mean RV end-diastolic volume evident on the magnetic resonance images was 136.9 ± 35.7 ml/m2. Intraoperative cardiac kinematics were assessed by video kinematic evaluation via a high-speed camera acquiring videos at 200 fps before and after valve replacement.

RESULTS

Patients presenting with RV end-diastolic volume <147 ml/m2 were significantly younger (11.2 ± 5.0 vs 38.4 ± 17.0; P = 0.005) and had a shorter time interval to valve replacement (11.0 ± 5.2 vs 30.1 ± 11.3; P = 0.03). The entire population showed a moderate correlation among energy expenditure, cardiac fatigue, perimeter of contraction and preoperative RV end-diastolic volume index. Both groups showed a reduction in all kinematic parameters after PVR, but those with end-diastolic volume >147 ml/m2 showed an unpredictable outcome.

CONCLUSIONS

Video kinematic evaluation provides insight into intraoperative RV recovery in patients with tetralogy of Fallot undergoing PVR. Accordingly, functional recovery can be expected in patients with preoperative end-diastolic volume <147 ml/m2.

Understanding the heart-brain axis response in COVID-19 patients: A suggestive perspective for therapeutic development

In-depth characterization of heart-brain communication in critically ill patients with severe acute respiratory failure is attracting significant interest in the COronaVIrus Disease 19 (COVID-19) pandemic era during intensive care unit (ICU) stay and after ICU or hospital discharge. Emerging research has provided new insights into pathogenic role of the deregulation of the heart-brain axis (HBA), a bidirectional flow of information, in leading to severe multiorgan disease syndrome (MODS) in patients with confirmed infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Noteworthy, HBA dysfunction may worsen the outcome of the COVID-19 patients. In this review, we discuss the critical role HBA plays in both promoting and limiting MODS in COVID-19. We also highlight the role of HBA as new target for novel therapeutic strategies in COVID-19 in order to open new translational frontiers of care. This is a translational perspective from the Italian Society of Cardiovascular Researches.

Local hyperactivation of L-type Ca2+ channels increases spontaneous Ca2+ release activity and cellular hypertrophy in right ventricular myocytes from heart failure rats

Right ventricle (RV) dysfunction is an independent predictor of patient survival in heart failure (HF). However, the mechanisms of RV progression towards failing are not well understood. We studied cellular mechanisms of RV remodelling in a rat model of left ventricle myocardial infarction (MI)-caused HF. RV myocytes from HF rats show significant cellular hypertrophy accompanied with a disruption of transverse-axial tubular network and surface flattening. Functionally these cells exhibit higher contractility with lower Ca²⁺ transients. The structural changes in HF RV myocytes correlate with more frequent spontaneous Ca²⁺ release activity than in control RV myocytes. This is accompanied by hyperactivated L-type Ca²⁺ channels (LTCCs) located specifically in the T-tubules of HF RV myocytes. The increased open probability of tubular LTCCs and Ca²⁺ sparks activation is linked to protein kinase A-mediated channel phosphorylation that occurs locally in T-tubules. Thus, our approach revealed that alterations in RV myocytes in heart failure are specifically localized in microdomains. Our findings may indicate the development of compensatory, though potentially arrhythmogenic, RV remodelling in the setting of LV failure. These data will foster better understanding of mechanisms of heart failure and it could promote an optimized treatment of patients.

3D Printed Masks for Powders and Viruses Safety Protection Using Food Grade Polymers: Empirical Tests

The production of 3D printed safety protection devices (SPD) requires particular attention to the material selection and to the evaluation of mechanical resistance, biological safety and surface roughness related to the accumulation of bacteria and viruses. We explored the possibility to adopt additive manufacturing technologies for the production of respirator masks, responding to the sudden demand of SPDs caused by the emergency scenario of the pandemic spread of SARS-COV-2. In this study, we developed different prototypes of masks, exclusively applying basic additive manufacturing technologies like fused deposition modeling (FDM) and droplet-based precision extrusion deposition (db-PED) to common food packaging materials. We analyzed the resulting mechanical characteristics, biological safety (cell adhesion and viability), surface roughness and resistance to dissolution, before and after the cleaning and disinfection phases. We showed that masks 3D printed with home-grade printing equipment have similar performances compared to the industrial-grade ones, and furthermore we obtained a perfect face fit by customizing their shape. Finally, we developed novel approaches to the additive manufacturing post-processing phases essential to assure human safety in the production of 3D printed custom medical devices.

Nanoscale Study of Calcium Handling Remodeling in Right Ventricular Cardiomyocytes Following Pulmonary Hypertension

Pulmonary hypertension is a complex disorder characterized by pulmonary vascular remodeling and right ventricular hypertrophy, leading to right heart failure. The mechanisms underlying this process are not well understood. We hypothesize that the structural remodeling occurring in the cardiomyocytes of the right ventricle affects the cytosolic Ca²⁺ handling leading to arrhythmias. After 12 days of monocrotaline-induced pulmonary hypertension in rats, epicardial mapping showed electrical remodeling in both ventricles. In myocytes isolated from the hypertensive rats, a combination of high-speed camera and confocal line-scan documented a prolongation of Ca²⁺ transients along with a higher local Ca²⁺-release activity. These Ca²⁺ transients were less synchronous than in controls, likely due to disorganized transverse-axial tubular system. In fact, following pulmonary hypertension, hypertrophied right ventricular myocytes showed significantly reduced number of transverse tubules and increased number of axial tubules; however, Stimulation Emission Depletion microscopy demonstrated that the colocalization of L-type Ca²⁺ channels and RyR2 (ryanodine receptor 2) remained unchanged. Finally, Stimulation Emission Depletion microscopy and super-resolution scanning patch-clamp analysis uncovered a decrease in the density of active L-type Ca²⁺ channels in right ventricular myocytes with an elevated open probability of the T-tubule anchored channels. This may represent a general mechanism of how nanoscale structural changes at the early stage of pulmonary hypertension impact on the development of the end stage failing phenotype in the right ventricle.

Author Correction: In-vivo vascular application via ultra-fast bioprinting for future 5D personalised nanomedicine

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

COVID-19-associated cardiovascular morbidity in older adults: a position paper from the Italian Society of Cardiovascular Researches

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells following binding with the cell surface ACE2 receptors, thereby leading to coronavirus disease 2019 (COVID-19). SARS-CoV-2 causes viral pneumonia with additional extrapulmonary manifestations and major complications, including acute myocardial injury, arrhythmia, and shock mainly in elderly patients. Furthermore, patients with existing cardiovascular comorbidities, such as hypertension and coronary heart disease, have a worse clinical outcome following contraction of the viral illness. A striking feature of COVID-19 pandemics is the high incidence of fatalities in advanced aged patients: this might be due to the prevalence of frailty and cardiovascular disease increase with age due to endothelial dysfunction and loss of endogenous cardioprotective mechanisms. Although experimental evidence on this topic is still at its infancy, the aim of this position paper is to hypothesize and discuss more suggestive cellular and molecular mechanisms whereby SARS-CoV-2 may lead to detrimental consequences to the cardiovascular system. We will focus on aging, cytokine storm, NLRP3/inflammasome, hypoxemia, and air pollution, which is an emerging cardiovascular risk factor associated with rapid urbanization and globalization. We will finally discuss the impact of clinically available CV drugs on the clinical course of COVID-19 patients. Understanding the role played by SARS-CoV2 on the CV system is indeed mandatory to get further insights into COVID-19 pathogenesis and to design a therapeutic strategy of cardio-protection for frail patients.

Mitochondrial mechanosensor in cardiovascular diseases

The role of mitochondria in cardiac tissue is of utmost importance due to the dynamic nature of the heart and its energetic demands, necessary to assure its proper beating function. Recently, other important mitochondrial roles have been discovered, namely its contribution to intracellular calcium handling in normal and pathological myocardium. Novel investigations support the fact that during the progression toward heart failure, mitochondrial calcium machinery is compromised due to its morphological, structural and biochemical modifications resulting in facilitated arrhythmogenesis and heart failure development. The interaction between mitochondria and sarcomere directly affect cardiomyocyte excitation-contraction and is also involved in mechano-transduction through the cytoskeletal proteins that tether together the mitochondria and the sarcoplasmic reticulum. The focus of this review is to briefly elucidate the role of mitochondria as (mechano) sensors in the heart.

Alginate Formulations: Current Developments in the Race for Hydrogel-Based Cardiac Regeneration

Cardiovascular diseases, including myocardial infarction (MI), represent the main worldwide cause of mortality and morbidity. In this scenario, to contrast the irreversible damages following MI, cardiac regeneration has emerged as a novel and promising solution for in situ cellular regeneration, preserving cell behavior and tissue cytoarchitecture. Among the huge variety of natural, synthetic, and hybrid compounds used for tissue regeneration, alginate emerged as a good candidate for cellular preservation and delivery, becoming one of the first biomaterial tested in pre-clinical research and clinical trials concerning cardiovascular diseases. Although promising results have been obtained, recellularization and revascularization of the infarcted area present still major limitations. Therefore, the demand is rising for alginate functionalization and its combination with molecules, factors, and drugs capable to boost the regenerative potential of the cardiac tissue. The focus of this review is to elucidate the promising properties of alginate and to highlight its benefits in clinical trials in relation to cardiac regeneration. The definition of hydrogels, the alginate characteristics, and recent biomedical applications are herewith described. Afterward, the review examines in depth the ongoing developments to refine the material relevance in cardiac recovery and regeneration after MI and presents current clinical trials based on alginate.

In-vivo vascular application via ultra-fast bioprinting for future 5D personalised nanomedicine

The design of 3D complex structures enables new correlation studies between the engineering parameters and the biological activity. Moreover, additive manufacturing technology could revolutionise the personalised medical pre-operative management due to its possibility to interplay with computer tomography. Here we present a method based on rapid freeze prototyping (RFP) 3D printer, reconstruction cutting, nano dry formulation, fast freeze gelation, disinfection and partial processes for the 5D digital models functionalisation. We elaborated the high-resolution computer tomography scan derived from a complex human peripheral artery and we reconstructed the 3D model of the vessel in order to obtain and verify the additive manufacturing processes. Then, based on the drug-eluting balloon selected for the percutaneous intervention, we reconstructed the biocompatible eluting-freeform coating containing 40 nm fluorescent nanoparticles (NPs) by means of RFP printer and we tested the in-vivo feasibility. We introduced the NPs-loaded 5D device in a rat's vena cava. The coating dissolved in a few minutes releasing NPs which were rapidly absorbed in vascular smooth muscle cell (VSMC) and human umbilical vein endothelial cell (HUVEC) in-vitro. We developed 5D high-resolution self-dissolving devices incorporating NPs with the perspective to apply this method to the personalised medicine.

3072Myocardial delivery of therapeutic miR-133 via inhalable nanoparticles prevents the pathologic development in a model of ventricular pressure overload

Background

MicroRNAs (miRs) are regulators involved in several biological processes and have been recognized as potential novel therapeutic targets for the treatment and prevention of CDs. We previously demonstrated that the cardiac-enriched miR-133, which is inversely related to failing heart conditions, is involved in several aspects of pathological cardiac remodeling via mitigation of cardiac hypertrophy and fibrosis, fine-tuning of the β1-adrenergic receptor signaling, and protection against oxidative stress-mediated apoptosis. However, effective and clinically oriented interventions aiming to delivery exogenous miR-133 for preventing the stress-induced downregulation of miR-133 levels are still missing.

Here, we applied an unconventional and effective nanotechnology-based inhalation approach enabling the delivery to diseased heart of exogenous miR-133 loaded into biocompatible and biodegradable calcium phosphate-based nanoparticles (CaPs).

Methods

Male C57Bl/6J mice (8 weeks) were subjected to a trans-aortic constriction (TAC), to induce a ventricular pressure overload. 4 experimental groups of TAC animals were randomly assigned to different intratracheal administrations of: 1. Saline (TAC Control); 2. CaP-miR133 (TAC CaP-miR133); 3. Pristine miR-133 (TAC miR133); 4. Unloaded CaPs (TAC CaP). Not TAC operated mice served as SHAM group. Intratracheal nebulizations were performed immediately after TAC surgery once-a-day in alternative days for 4 consecutive weeks. Echocardiography (ECO) were conducted before TAC, at 2 and 4 weeks after surgery. ECO as well as molecular and histological analyses were performed at sacrifices.

Results

ECO analyses showed an effective CaP-miR133-associated reversal of the failure progression, preserving left ventricular internal diameter (LVID) during cardiac cycle, ejection fraction (EF) and fraction shortening (FS), both at 2 and 4 weeks after TAC. This improvement was associated with the restoration of physiological levels of miR-133 in TAC-stressed isolated cardiomyocytes as well as its contractile activity. TAC mice receiving CaP-mir133 showed reduced indexes of fibrosis. In contrast, no beneficial effects were observed when unloaded CaPs or pristine miR-133 were administered. No major alterations of the immunological status of mice were observed after CaP-miR133 administration.

Conclusions

Intratracheal nebulization of miR-133-loaded nanoparticles is an effective approach for the beneficial restoration of cardiac performance, cell contractility and remodeling in a mouse model of left ventricular pressure overload. Providing the evidence for a potential innovative application of the emerging nanotechnologies, our approach might represent an important step forward for the treatment of cardiovascular diseases.

Acknowledgement/Funding

Fondazione Umberto Veronesi and CUPIDO project (EU's Horizon 2020, Grant Agreement 720834)

Cardiomyocyte-myofibroblast contact dynamism is modulated by connexin-43

Healthy cardiomyocytes are electrically coupled at the intercalated discs by gap junctions. In infarcted hearts, adverse gap-junctional remodeling occurs in the border zone, where cardiomyocytes are chemically and electrically influenced by myofibroblasts. The physical movement of these contacts remains unquantified. Using scanning ion conductance microscopy, we show that intercellular contacts between cardiomyocytes and myofibroblasts are highly dynamic, mainly owing to the edge dynamics (lamellipodia) of the myofibroblasts. Decreasing the amount of functional connexin-43 (Cx43) at the membrane through Cx43 silencing, suppression of Cx43 trafficking, or hypoxia-induced Cx43 internalization attenuates heterocellular contact dynamism. However, we found decreased dynamism and stabilized membrane contacts when cellular coupling was strengthened using 4-phenylbutyrate (4PB). Fluorescent-dye transfer between cells showed that the extent of functional coupling between the 2 cell types correlated with contact dynamism. Intercellular calcein transfer from myofibroblasts to cardiomyocytes is reduced after myofibroblast-specific Cx43 down-regulation. Conversely, 4PB-treated myofibroblasts increased their functional coupling to cardiomyocytes. Consistent with lamellipodia-mediated contacts, latrunculin-B decreases dynamism, lowers physical communication between heterocellular pairs, and reduces Cx43 intensity in contact regions. Our data show that heterocellular cardiomyocyte-myofibroblast contacts exhibit high dynamism. Therefore, Cx43 is a potential target for prevention of aberrant cardiomyocyte coupling and myofibroblast proliferation in the infarct border zone.-Schultz, F., Swiatlowska, P., Alvarez-Laviada, A., Sanchez-Alonso, J. L., Song, Q., de Vries, A. A. F., Pijnappels, D. A., Ongstad, E., Braga, V. M. M., Entcheva, E., Gourdie, R. G., Miragoli, M., Gorelik, J. Cardiomyocyte-myofibroblast contact dynamism is modulated by connexin-43.

Subchronic exposure to titanium dioxide nanoparticles modifies cardiac structure and performance in spontaneously hypertensive rats

BACKGROUND

Non-communicable diseases, intended as the results of a combination of inherited, environmental and biological factors, kill 40 million people each year, equivalent to roughly 70% of all premature deaths globally. The possibility that manufactured nanoparticles (NPs) may affect cardiac performance, has led to recognize NPs-exposure not only as a major Public Health concern, but also as an occupational hazard. In volunteers, NPs-exposure is problematic to quantify. We recently found that inhaled titanium dioxide NPs, one of the most produced engineered nanomaterials, acutely increased cardiac excitability and promoted arrhythmogenesis in normotensive rats by a direct interaction with cardiac cells. We hypothesized that such scenario can be exacerbated by latent cardiovascular disorders such as hypertension.

RESULTS

We monitored cardiac electromechanical performance in spontaneously hypertensive rats (SHRs) exposed to titanium dioxide NPs for 6 weeks using a combination of cardiac functional measurements associated with toxicological, immunological, physical and genetic assays. Longitudinal radio-telemetry ECG recordings and multiple-lead epicardial potential mapping revealed that atrial activation times significantly increased as well as proneness to arrhythmia. At the third week of nanoparticles administration, the lung and cardiac tissue encountered a maladaptive irreversible structural remodelling starting with increased pro-inflammatory cytokines levels and lipid peroxidation, resulting in upregulation of the main pro-fibrotic cardiac genes. At the end of the exposure, the majority of spontaneous arrhythmic events terminated, while cardiac hemodynamic deteriorated and a significant accumulation of fibrotic tissue occurred as compared to control untreated SHRs. Titanium dioxide nanoparticles were quantified in the heart tissue although without definite accumulation as revealed by particle-induced X-ray emission and ultrastructural analysis.

CONCLUSIONS

The co-morbidity of hypertension and inhaled nanoparticles induces irreversible hemodynamic impairment associated with cardiac structural damage potentially leading to heart failure. The time-dependence of exposure indicates a non-return point that needs to be taken into account in hypertensive subjects daily exposed to nanoparticles.

In-situ optical assessment of rat epicardial kinematic parameters reveals frequency-dependent mechanic heterogeneity related to gender

BACKGROUND

Gender-related cardiac mechanics following the electrical activity has been investigated from basic to clinical research, but results are still controversial. The aim of this work is to study the gender related cardiac mechanics and to focus on its heart rate dependency.

METHODS

We employed 12 Sprague Dawley rats (5 males and 7 females) of the same age and, through a novel high resolution artificial vision contactless approach, we evaluated in-situ cardiac kinematic. The hearts were paced on the right atria appendage via cathodal stimuli at rising frequency.

RESULTS

Kinematic data obtained at rising pacing rates are different between male and female rat hearts: male tended to maintain the same level of cardiac force, energy and contractility, while female responded with an increment of such parameters at increasing heart rate. Female hearts preserved their pattern of contraction and epicardial torsion (vorticity) at rising pacing rates compared to male. Furthermore, we observed a difference in the mechanical restitution: systolic time vs. diastolic time, as an index of cardiac performance, reached higher value in male compared to female hearts.

CONCLUSION

Our innovative technology was capable to evaluate in-situ rat epicardial kinematic at high stimulation frequency, revealing that male preserved kinematic parameters but varying the pattern of contraction/relaxation. On the contrary, female preserved the pattern of contraction/relaxation increasing kinematic parameters.

The K219T-Lamin mutation induces conduction defects through epigenetic inhibition of SCN5A in human cardiac laminopathy

Mutations in LMNA, which encodes the nuclear proteins Lamin A/C, can cause cardiomyopathy and conduction disorders. Here, we employ induced pluripotent stem cells (iPSCs) generated from human cells carrying heterozygous K219T mutation on LMNA to develop a disease model. Cardiomyocytes differentiated from these iPSCs, and which thus carry K219T-LMNA, have altered action potential, reduced peak sodium current and diminished conduction velocity. Moreover, they have significantly downregulated Nav1.5 channel expression and increased binding of Lamin A/C to the promoter of SCN5A, the channel's gene. Coherently, binding of the Polycomb Repressive Complex 2 (PRC2) protein SUZ12 and deposition of the repressive histone mark H3K27me3 are increased at SCN5A. CRISPR/Cas9-mediated correction of the mutation re-establishes sodium current density and SCN5A expression. Thus, K219T-LMNA cooperates with PRC2 in downregulating SCN5A, leading to decreased sodium current density and slower conduction velocity. This mechanism may underlie the conduction abnormalities associated with LMNA-cardiomyopathy.

Inhalation of peptide-loaded nanoparticles improves heart failure

Peptides are highly selective and efficacious for the treatment of cardiovascular and other diseases. However, it is currently not possible to administer peptides for cardiac-targeting therapy via a noninvasive procedure, thus representing scientific and technological challenges. We demonstrate that inhalation of small (<50 nm in diameter) biocompatible and biodegradable calcium phosphate nanoparticles (CaPs) allows for rapid translocation of CaPs from the pulmonary tree to the bloodstream and to the myocardium, where their cargo is quickly released. Treatment of a rodent model of diabetic cardiomyopathy by inhalation of CaPs loaded with a therapeutic mimetic peptide that we previously demonstrated to improve myocardial contraction resulted in restoration of cardiac function. Translation to a porcine large animal model provides evidence that inhalation of a peptide-loaded CaP formulation is an effective method of targeted administration to the heart. Together, these results demonstrate that inhalation of biocompatible tailored peptide nanocarriers represents a pioneering approach for the pharmacological treatment of heart failure.

A combined low-frequency electromagnetic and fluidic stimulation for a controlled drug release from superparamagnetic calcium phosphate nanoparticles: potential application for cardiovascular diseases

Alternative drug delivery approaches to treat cardiovascular diseases are currently under intense investigation. In this domain, the possibility to target the heart and tailor the amount of drug dose by using a combination of magnetic nanoparticles (NPs) and electromagnetic devices is a fascinating approach. Here, an electromagnetic device based on Helmholtz coils was generated for the application of low-frequency magnetic stimulations to manage drug release from biocompatible superparamagnetic Fe-hydroxyapatite NPs (FeHAs). Integrated with a fluidic circuit mimicking the flow of the cardiovascular environment, the device was efficient to trigger the release of a model drug (ibuprofen) from FeHAs as a function of the applied frequencies. Furthermore, the biological effects on the cardiac system of the identified electromagnetic exposure were assessed in vitro and in vivo by acute stimulation of isolated adult cardiomyocytes and in an animal model. The cardio-compatibility of FeHAs was also assessed in vitro and in an animal model. No alterations of cardiac electrophysiological properties were observed in both cases, providing the evidence that the combination of low-frequency magnetic stimulations and FeHAs might represent a promising strategy for controlled drug delivery to the failing heart.

The unrecognized occupational relevance of the interaction between engineered nanomaterials and the gastro-intestinal tract: a consensus paper from a multidisciplinary working group

BACKGROUND

There is a fundamental gap of knowledge on the health effects caused by the interaction of engineered nanomaterials (ENM) with the gastro-intestinal tract (GIT). This is partly due to the incomplete knowledge of the complex physical and chemical transformations that ENM undergo in the GIT, and partly to the widespread belief that GIT health effects of ENM are much less relevant than pulmonary effects. However, recent experimental findings, considering the role of new players in gut physiology (e.g. the microbiota), shed light on several outcomes of the interaction ENM/GIT. Along with this new information, there is growing direct and indirect evidence that not only ingested ENM, but also inhaled ENM may impact on the GIT. This fact, which may have relevant implications in occupational setting, has never been taken into consideration. This review paper summarizes the opinions and findings of a multidisciplinary team of experts, focusing on two main aspects of the issue: 1) ENM interactions within the GIT and their possible consequences, and 2) relevance of gastro-intestinal effects of inhaled ENMs. Under point 1, we analyzed how luminal gut-constituents, including mucus, may influence the adherence of ENM to cell surfaces in a size-dependent manner, and how intestinal permeability may be affected by different physico-chemical characteristics of ENM. Cytotoxic, oxidative, genotoxic and inflammatory effects on different GIT cells, as well as effects on microbiota, are also discussed. Concerning point 2, recent studies highlight the relevance of gastro-intestinal handling of inhaled ENM, showing significant excretion with feces of inhaled ENM and supporting the hypothesis that GIT should be considered an important target of extrapulmonary effects of inhaled ENM.

CONCLUSIONS

In spite of recent insights on the relevance of the GIT as a target for toxic effects of nanoparticles, there is still a major gap in knowledge regarding the impact of the direct versus indirect oral exposure. This fact probably applies also to larger particles and dictates careful consideration in workers, who carry the highest risk of exposure to particulate matter.

TGF-β1 (Transforming Growth Factor-β1) Plays a Pivotal Role in Cardiac Myofibroblast Arrhythmogenicity

BACKGROUND

TGF-β₁ (transforming growth factor-β₁) importantly contributes to cardiac fibrosis by controlling differentiation, migration, and collagen secretion of cardiac myofibroblasts. It is still elusive, however, to which extent TGF-β₁ alters the electrophysiological phenotype of myofibroblasts and cardiomyocytes and whether it affects proarrhythmic myofibroblast-cardiomyocyte crosstalk observed in vitro.

METHODS AND RESULTS

Patch-clamp recordings of cultured neonatal rat ventricular myofibroblasts revealed that TGF-β₁, applied for 24 to 48 hours at clinically relevant concentrations (≤2.5 ng/mL), causes substantial membrane depolarization concomitant with a several-fold increase of transmembrane currents. Transcriptome analysis revealed TGF-β₁-dependent changes in 29 of 63 ion channel/pump/connexin transcripts, indicating a pleiotropic effect on the electrical phenotype of myofibroblasts. Whereas not affecting cardiomyocyte membrane potentials and cardiomyocyte-cardiomyocyte gap junctional coupling, TGF-β₁ depolarized cardiomyocytes coupled to myofibroblasts by ≈20 mV and increased gap junctional coupling between myofibroblasts and cardiomyocytes >5-fold as reflected by elevated connexin 43 and consortin transcripts. TGF-β₁-dependent cardiomyocyte depolarization resulted from electrotonic crosstalk with myofibroblasts as demonstrated by immediate normalization of cardiomyocyte electrophysiology after targeted disruption of coupled myofibroblasts and by cessation of ectopic activity of cardiomyocytes coupled to myofibroblasts during pharmacological gap junctional uncoupling. In cardiac fibrosis models exhibiting slow conduction and ectopic activity, block of TGF-β₁ signaling completely abolished both arrhythmogenic conditions.

CONCLUSIONS

TGF-β₁ profoundly alters the electrophysiological phenotype of cardiac myofibroblasts. Apart from possibly contributing to the control of cell function in general, the changes proved to be pivotal for proarrhythmic myofibroblast-cardiomyocyte crosstalk in vitro, which suggests that TGF-β₁ may play a potentially important role in arrhythmogenesis of the fibrotic heart.

Histone Methyltransferase G9a Is Required for Cardiomyocyte Homeostasis and Hypertrophy

BACKGROUND

Correct gene expression programming of the cardiomyocyte underlies the normal functioning of the heart. Alterations to this can lead to the loss of cardiac homeostasis, triggering heart dysfunction. Although the role of some histone methyltransferases in establishing the transcriptional program of postnatal cardiomyocytes during heart development has been shown, the function of this class of epigenetic enzymes is largely unexplored in the adult heart. In this study, we investigated the role of G9a/Ehmt2, a histone methyltransferase that defines a repressive epigenetic signature, in defining the transcriptional program for cardiomyocyte homeostasis and cardiac hypertrophy.

METHODS

We investigated the function of G9a in normal and stressed cardiomyocytes with the use of a conditional, cardiac-specific G9a knockout mouse, a specific G9a inhibitor, and high-throughput approaches for the study of the epigenome (chromatin immunoprecipitation sequencing) and transcriptome (RNA sequencing); traditional methods were used to assess cardiac function and cardiovascular disease.

RESULTS

We found that G9a is required for cardiomyocyte homeostasis in the adult heart by mediating the repression of key genes regulating cardiomyocyte function via dimethylation of H3 lysine 9 and interaction with enhancer of zeste homolog 2, the catalytic subunit of polycomb repressive complex 2, and MEF2C-dependent gene expression by forming a complex with this transcription factor. The G9a-MEF2C complex was found to be required also for the maintenance of heterochromatin needed for the silencing of developmental genes in the adult heart. Moreover, G9a promoted cardiac hypertrophy by repressing antihypertrophic genes.

CONCLUSIONS

Taken together, our findings demonstrate that G9a orchestrates critical epigenetic changes in cardiomyocytes in physiological and pathological conditions, thereby providing novel therapeutic avenues for cardiac pathologies associated with dysregulation of these mechanisms.

Abstract 11: Lamin A/C Mutations Epigenetically Dysregulate Scn5a Gene Expression, Perturbing Action Potential Properties in IPSC-derived Cardiomyocytes

Mutations of the LMNA gene, encoding the nuclear lamina proteins Lamin A/C, are a common cause of dilated cardiomyopathy, typically manifesting in association with cardiac conduction defects. LaminA/C regulate various nuclear activities, including maintenance of the nuclear structure, gene transcription and chromatin organization. Most studies on the consequences of Lamin A/C defects were conducted on fibroblasts, while studies on human cardiomyocytes (CMs) are scarce. We therefore generated a cardiac model of laminopathy obtained by differentiation of CMs from induced pluripotent stem cells (iPSCs) of patients carrying the K219T Lamin A/C mutation. In vitro, these cells recapitulate the morphological features of dilated cardiomyopathy, specifically sarcomeric disorganization and increased size. Using this model, we performed a comprehensive analysis of the electrophysiological properties of LMNA-CMs both at single cell level and in a multi-cellular setting. Using patch-clamp technique, results revealed significant changes in maximal upstroke velocity (dV/dt max ), action potential amplitude (APA) and overshoot (OV) in LMNA-CMs compared to those obtained from family-matched healthy controls (CNTR); these defects were associated with a reduction of the peak sodium currents and a diminished conduction velocity, measured in strands of electrically-coupled CMs. Biochemical studies showed a significant reduction of both the sodium channel Nav1.5 protein and its transcript in LMNA-CMs, accompanied by an increased binding of LaminA/C to the promoter of its coding gene, SCN5A. Binding of the Polycomb group protein SUZ12 and of the H3K27me3 histone repressive mark was also increased. Consistently, 3D-FISH experiments also indicated a preferential localization of SCN5A genomic loci at the nuclear periphery in LMNA-CMs. As a whole, our findings support a model in which mutated Lamin A/C perturb SCN5A gene expression by favouring PRC2 (Polycomb Repressive Complex 2) binding to its promoter, leading to decreased sodium current peak and slower conduction velocity. This mechanism may eventually sustain the conduction abnormalities inevitably occurring in patients with LMNA-cardiomyopathy.

Cardiac kinematic parameters computed from video of in situ beating heart

Mechanical function of the heart during open-chest cardiac surgery is exclusively monitored by echocardiographic techniques. However, little is known about local kinematics, particularly for the reperfused regions after ischemic events. We report a novel imaging modality, which extracts local and global kinematic parameters from videos of in situ beating hearts, displaying live video cardiograms of the contraction events. A custom algorithm tracked the movement of a video marker positioned ad hoc onto a selected area and analyzed, during the entire recording, the contraction trajectory, displacement, velocity, acceleration, kinetic energy and force. Moreover, global epicardial velocity and vorticity were analyzed by means of Particle Image Velocimetry tool. We validated our new technique by i) computational modeling of cardiac ischemia, ii) video recordings of ischemic/reperfused rat hearts, iii) videos of beating human hearts before and after coronary artery bypass graft, and iv) local Frank-Starling effect. In rats, we observed a decrement of kinematic parameters during acute ischemia and a significant increment in the same region after reperfusion. We detected similar behavior in operated patients. This modality adds important functional values on cardiac outcomes and supports the intervention in a contact-free and non-invasive mode. Moreover, it does not require particular operator-dependent skills.

Cardiac kinematic parameters computed from video of in situ beating heart

Mechanical function of the heart during open-chest cardiac surgery is exclusively monitored by echocardiographic techniques. However, little is known about local kinematics, particularly for the reperfused regions after ischemic events. We report a novel imaging modality, which extracts local and global kinematic parameters from videos of in situ beating hearts, displaying live video cardiograms of the contraction events. A custom algorithm tracked the movement of a video marker positioned ad hoc onto a selected area and analyzed, during the entire recording, the contraction trajectory, displacement, velocity, acceleration, kinetic energy and force. Moreover, global epicardial velocity and vorticity were analyzed by means of Particle Image Velocimetry tool. We validated our new technique by i) computational modeling of cardiac ischemia, ii) video recordings of ischemic/reperfused rat hearts, iii) videos of beating human hearts before and after coronary artery bypass graft, and iv) local Frank-Starling effect. In rats, we observed a decrement of kinematic parameters during acute ischemia and a significant increment in the same region after reperfusion. We detected similar behavior in operated patients. This modality adds important functional values on cardiac outcomes and supports the intervention in a contact-free and non-invasive mode. Moreover, it does not require particular operator-dependent skills.

Mitochondrial Mechanosensor Microdomains in Cardiovascular Disorders

The cardiomyocytes populating the 'working myocardium' are highly organized and such organization ranges from macroscale (e.g. the geometrical rod shape) to microscale (dyad/t-tubules) domains. This meticulous level of organization is imperative for assuring the normal and physiological pump-function of the heart. In the pathological cardiac tissue, the domains-related architecture is partially lost, resulting in morphological, electrical and metabolic remodeling and promoting cardiovascular diseases including heart failure and arrhythmias. Indeed, arrhythmogenesis during heart failure is a major clinical problem. Arrhythmias have been extensively studied from an electrical etiology, but only recently, physiologists and scientists have focused their attention on cellular and subcellular mechanosensors. We and others have investigated whether the nanoscale mechanosensitive properties of cardiomyocytes from failing hearts have a bearing upon the initiation of abnormal electrical activity. This chapter highlights the recent findings in the field, especially the role of mitochondria function and alignment in failing cardiomyocytes interrogated via nanomechanical stimuli.

Effect of anisotropy on ventricular vulnerability to unidirectional block and reentry by single premature stimulation during normal sinus rhythm in rat heart

Single high-intensity premature stimuli when applied to the ventricles during ventricular drive of an ectopic site, as in Winfree's "pinwheel experiment," usually induce reentry arrhythmias in the normal heart, while single low-intensity stimuli barely do. Yet ventricular arrhythmia vulnerability during normal sinus rhythm remains largely unexplored. With a view to define the role of anisotropy on ventricular vulnerability to unidirectional conduction block and reentry, we revisited the pinwheel experiment with reduced constraints in the in situ rat heart. New features included single premature stimulation during normal sinus rhythm, stimulation and unipolar potential mapping from the same high-resolution epicardial electrode array, and progressive increase in stimulation strength and prematurity from diastolic threshold until arrhythmia induction. Measurements were performed with 1-ms cathodal stimuli at multiple test sites (n = 26) in seven rats. Stimulus-induced virtual electrode polarization during sinus beat recovery phase influenced premature ventricular responses. Specifically, gradual increase in stimulus strength and prematurity progressively induced make, break, and graded-response stimulation mechanisms. Hence unidirectional conduction block occurred as follows: 1) along fiber direction, on right and left ventricular free walls (n = 23), initiating figure-eight reentry (n = 17) and tachycardia (n = 12), and 2) across fiber direction, on lower interventricular septum (n = 3), initiating spiral wave reentry (n = 2) and tachycardia (n = 1). Critical time window (55.1 ± 4.7 ms, 68.2 ± 6.0 ms) and stimulus strength lower limit (4.9 ± 0.6 mA) defined vulnerability to reentry. A novel finding of this study was that ventricular tachycardia evolves and is maintained by episodes of scroll-like wave and focal activation couplets. We also found that single low-intensity premature stimuli can induce repetitive ventricular response (n = 13) characterized by focal activations.NEW & NOTEWORTHY We performed ventricular cathodal point stimulation during sinus rhythm by progressively increasing stimulus strength and prematurity. Virtual electrode polarization and recovery gradient progressively induced make, break, and graded-response stimulation mechanisms. Unidirectional conduction block occurred along or across fiber direction, initiating figure-eight or spiral wave reentry, respectively, and tachycardia sustained by scroll wave and focal activations.

Peptidomimetic Targeting of Cavβ2 Overcomes Dysregulation of the L-Type Calcium Channel Density and Recovers Cardiac Function

BACKGROUND

L-type calcium channels (LTCCs) play important roles in regulating cardiomyocyte physiology, which is governed by appropriate LTCC trafficking to and density at the cell surface. Factors influencing the expression, half-life, subcellular trafficking, and gating of LTCCs are therefore critically involved in conditions of cardiac physiology and disease.

METHODS

Yeast 2-hybrid screenings, biochemical and molecular evaluations, protein interaction assays, fluorescence microscopy, structural molecular modeling, and functional studies were used to investigate the molecular mechanisms through which the LTCC Cavβ2 chaperone regulates channel density at the plasma membrane.

RESULTS

On the basis of our previous results, we found a direct linear correlation between the total amount of the LTCC pore-forming Cavα1.2 and the Akt-dependent phosphorylation status of Cavβ2 both in a mouse model of diabetic cardiac disease and in 6 diabetic and 7 nondiabetic cardiomyopathy patients with aortic stenosis undergoing aortic valve replacement. Mechanistically, we demonstrate that a conformational change in Cavβ2 triggered by Akt phosphorylation increases LTCC density at the cardiac plasma membrane, and thus the inward calcium current, through a complex pathway involving reduction of Cavα1.2 retrograde trafficking and protein degradation through the prevention of dynamin-mediated LTCC endocytosis; promotion of Cavα1.2 anterograde trafficking by blocking Kir/Gem-dependent sequestration of Cavβ2, thus facilitating the chaperoning of Cavα1.2; and promotion of Cavα1.2 transcription by the prevention of Kir/Gem-mediated shuttling of Cavβ2 to the nucleus, where it limits the transcription of Cavα1.2 through recruitment of the heterochromatin protein 1γ epigenetic repressor to the Cacna1c promoter. On the basis of this mechanism, we developed a novel mimetic peptide that, through targeting of Cavβ2, corrects LTCC life-cycle alterations, facilitating the proper function of cardiac cells. Delivery of mimetic peptide into a mouse model of diabetic cardiac disease associated with LTCC abnormalities restored impaired calcium balance and recovered cardiac function.

CONCLUSIONS

We have uncovered novel mechanisms modulating LTCC trafficking and life cycle and provide proof of concept for the use of Cavβ2 mimetic peptide as a novel therapeutic tool for the improvement of cardiac conditions correlated with alterations in LTCC levels and function.

Bioinspired negatively charged calcium phosphate nanocarriers for cardiac delivery of MicroRNAs

Aim: To develop biocompatible and bioresorbable negatively charged calcium phosphate nanoparticles (CaP-NPs) as an innovative therapeutic system for the delivery of bioactive molecules to the heart. Materials & methods: CaP-NPs were synthesized via a straightforward one-pot biomineralization-inspired protocol employing citrate as a stabilizing agent and regulator of crystal growth. CaP-NPs were administered to cardiac cells in vitro and effects of treatments were assessed. CaP-NPs were administered in vivo and delivery of microRNAs was evaluated. Results: CaP-NPs efficiently internalized into cardiomyocytes without promoting toxicity or interfering with any functional properties. CaP-NPs successfully encapsulated synthetic microRNAs, which were efficiently delivered into cardiac cells in vitro and in vivo. Conclusion: CaP-NPs are a safe and efficient drug-delivery system for potential therapeutic treatments of polarized cells such as cardiomyocytes.

Antiarrhythmic effect of growth factor-supplemented cardiac progenitor cells in chronic infarcted heart

c-Kit(pos) cardiac progenitor cells (CPCs) represent a successful approach in healing the infarcted heart and rescuing its mechanical function, but electrophysiological consequences are uncertain. CPC mobilization promoted by hepatocyte growth factor (HGF) and IGF-1 improved electrogenesis in myocardial infarction (MI). We hypothesized that locally delivered CPCs supplemented with HGF + IGF-1 (GFs) can concur in ameliorating electrical stability of the regenerated heart. Adult male Wistar rats (139 rats) with 4-wk-old MI or sham conditions were randomized to receive intramyocardial injection of GFs, CPCs, CPCs + GFs, or vehicle (V). Enhanced green fluorescent protein-tagged CPCs were used for cell tracking. Vulnerability to stress-induced arrhythmia was assessed by telemetry-ECG. Basic cardiac electrophysiological properties were examined by epicardial multiple-lead recording. Hemodynamic function was measured invasively. Hearts were subjected to anatomical, morphometric, immunohistochemical, and molecular biology analyses. Compared with V and at variance with individual CPCs, CPCs + GFs approximately halved arrhythmias in all animals, restoring cardiac anisotropy toward sham values. GFs alone reduced arrhythmias by less than CPCs + GFs, prolonging ventricular refractoriness without affecting conduction velocity. Concomitantly, CPCs + GFs reactivated the expression levels of Connexin-43 and Connexin-40 as well as channel proteins of key depolarizing and repolarizing ion currents differently than sole GFs. Mechanical function and anatomical remodeling were equally improved by all regenerative treatments, thus exhibiting a divergent behavior relative to electrical aspects. Conclusively, we provided evidence of distinctive antiarrhythmic action of locally injected GF-supplemented CPCs, likely attributable to retrieval of Connexin-43, Connexin-40, and Cav1.2 expression, favoring intercellular coupling and spread of excitation in mended heart.

Electroactive polyurethane/siloxane derived from castor oil as a versatile cardiac patch, part II: HL-1 cytocompatibility and electrical characterizations

In first part of this experiment, biocompatibility of the newly developed electroactive polyurethane/siloxane films containing aniline tetramer moieties was demonstrated with proliferation and differentiation of C2C12 myoblasts. Here we further assessed the cytocompatibility of the prepared samples with HL1-cell line, the electrophysiological properties and the patch clamp recording of the seeded cells over the selected electroactive sample. Presence of electroactive aniline tetramer in the structure of polyurethane/siloxane led to the increased expression of cardiac-specific genes of HL-1 cells involved in muscle contraction and electrical coupling. Our results showed that expression of Cx43, TrpT-2, and SERCA genes was significantly increased in conductive sample compared to tissue culture plate and the corresponding non-conductive analogous. The prepared materials were not only biocompatible in terms of cellular toxicity, but did not alter the intrinsic electrical characteristics of HL-1 cells. Embedding the electroactive moiety into the prepared films improved the properties of these polymeric cardiac construct through the enhanced transmission of electrical signals between the cells. Based on morphological observation, calcium imaging and electrophysiological recordings, we demonstrated the potential applicability of these materials for cardiac tissue engineering. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1398-1407, 2016.