Response Of Cardiac Cells Research Articles

Shaping cardiac destiny: the role of post-translational modifications on endoplasmic reticulum - mitochondria crosstalk in cardiac remodeling.

Cardiac remodeling is a shared pathological change in most cardiovascular diseases. Encompassing both adaptive physiological responses and decompensated pathological changes. Anatomically, atrial remodeling is primarily caused by atrial fibrillation, whereas ventricular remodeling is typically induced by myocardial infarction, hypertension, or cardiomyopathy. Mitochondria, the powerhouse of cardiomyocytes, collaborate with other organelles such as the endoplasmic reticulum to control a variety of pathophysiological processes such as calcium signaling, lipid transfer, mitochondrial dynamics, biogenesis, and mitophagy. This mechanism is proven to be essential for cardiac remodeling. Post-translational modifications can regulate intracellular signaling pathways, gene expression, and cellular stress responses in cardiac cells by modulating protein function, stability, and interactions, consequently shaping the myocardial response to injury and stress. These modifications, in particular phosphorylation, acetylation, and ubiquitination, are essential for the regulation of the complex molecular pathways that underlie cardiac remodeling. This review provides a comprehensive overview of the crosstalk between the endoplasmic reticulum and mitochondria during cardiac remodeling, focusing on the regulatory effects of various post-translational modifications on these interactions.

Single-cell RNA sequencing profiling of mouse cardiac cells in response to retinoic acid

Congenital heart disease (CHD) is the leading cause of birth defect-related mortality. CHD is a multifactorial, complex disease involving environmental factors playing important roles. To elucidate the cardiac cellular and molecular mechanisms of cardiac malformation, we administered pregnant mice with a single dose of all-trans retinoic acid (RA) at E8.5, as the CHD model. We performed single-cell RNA sequencing on cardiac cells from developing mouse hearts spanning from E8.5 to E17.5 after RA administration. A total of 69,447 cells were obtained from seven developmental stages ranging from E8.5 to E17.5. RA significantly impacted various CM subpopulations, particularly the outflow tract CMs at E9.0 by reduction of Tdgf1 expression. RA also influences the transition of endocardial-to-mesenchymal cells by decreasing the Stmn2 levels, which may contribute to abnormal valve development. In addition, RA altered the metabolic pattern of epicardial cells at E11.5 and promoted its differentiation potential. Taken together, these results are valuable for the development of preventive and therapeutic strategies for CHDs.

(Invited) Cardiac Engineering: Optical Mapping in Cellular Communication

Microfluidic platforms have emerged as valuable tools for replicating the adverse effects of chemotherapy drugs on cardiac and non-cardiac cells in vitro. However, these systems currently fall short of comprehensively capturing the intricate nature of human responses to chemotherapy, necessitating further validation to enhance model accuracy. While innovative chip systems provide insightful means for screening cardiac toxicity, they encounter challenges in addressing individual variations in drug responses and the influence of patient-specific factors.A novel cardiac chip incorporating intracellular electrophysiological techniques was developed to monitor acute hypoxia-induced responses in cardiac cells. Despite its promising potential, the model exhibits limitations inherent to its simplified two-dimensional microfluidic system, warranting additional validation and optimization efforts to enhance physiological relevance and facilitate applications in clinical translation.Moreover, previous research has proposed the formation of functional connections between human neurons and myocardial cells in a microfluidic chip. However, this study primarily focused on one-way connections between neurons and myocardial cells, overlooking the complexities of bidirectional neuro-muscular connections. Consequently, further research is imperative to deepen our understanding of the intricate interactions between neurons and myocardial cells.Optical mapping techniques assessed transmembrane voltage, mitochondrial activity, and calcium signals during electric pacing. These comprehensive assessments aim to advance our understanding of cardiac electrophysiology under drug exposure, providing crucial insights into the intricate responses of cardiac cells to chemotherapy. This research has significant implications for enhancing our understanding of cardiac safety in the context of chemotherapy.

Infiltrating macrophages amplify doxorubicin-induced cardiac damage: role of catecholamines

BackgroundThe functional contribution of non-myocyte cardiac cells, such as inflammatory cells, in the setup of heart failure in response to doxorubicin (Dox) is recently becoming of growing interest.ObjectivesThe study aims to evaluate the role of macrophages in cardiac damage elicited by Dox treatment.MethodsC57BL/6 mice were treated with one intraperitoneal injection of Dox (20 mg/kg) and followed up for 5 days by cardiac ultrasounds (CUS), histological, and flow cytometry evaluations. We also tested the impact of Dox in macrophage-depleted mice. Rat cardiomyoblasts were directly treated with Dox (D-Dox) or with a conditioned medium from cultured murine macrophages treated with Dox (M-Dox).ResultsIn response to Dox, macrophage infiltration preceded cardiac damage. Macrophage depletion prevents Dox-induced damage, suggesting a key role of these cells in promoting cardiotoxicity. To evaluate the crosstalk between macrophages and cardiac cells in response to DOX, we compared the effects of D-Dox and M-Dox in vitro. Cell vitality was lower in cardiomyoblasts and apoptosis was higher in response to M-Dox compared with D-Dox. These events were linked to p53-induced mitochondria morphology, function, and autophagy alterations. We identify a mechanistic role of catecholamines released by Dox-activated macrophages that lead to mitochondrial apoptosis of cardiac cells through β-AR stimulation.ConclusionsOur data indicate that crosstalk between macrophages and cardiac cells participates in cardiac damage in response to Dox.Graphical abstract

CARDIAC MACROPHAGES EXACERBATE DOXORUBICIN-INDUCED CARDIOTOXICITY

Objective: The functional contribution of non-myocyte cardiac cells, such as inflammatory cells, in the setup of heart failure in response to doxorubicin (Dox) is recently becoming of growing interest. Objective: The study aims to evaluate the role of macrophages in cardiac damage elicited by Dox treatment. Design and method: C57BL/6 mice were treated with one intraperitoneal injection of Dox (20mg/Kg) and followed up for 5 days by cardiac ultrasounds (CUS), histological, and flow cytometry evaluations. We also tested the impact of Dox in macrophage-depleted mice. Murine cardiomyoblasts were directly treated with Dox (D-Dox) or with a conditioned medium from cultured murine macrophages treated with Dox (M-Dox). Results: In response to Dox, macrophage infiltration preceded cardiac damage. Macrophage depletion prevents Dox-induced damage, suggesting a key role of these cells in promoting cardiotoxicity. To evaluate the crosstalk between macrophages and cardiac cells in response to DOX, we compared the effects of D-Dox and M-Dox in vitro. In cardiomyoblasts, cell vitality was lower and apoptosis was higher in response to M-Dox compared with D-Dox. These events were linked to p53-induced alterations of mitochondria morphology, function, and autophagy. We identify a mechanistic role of catecholamines released by Dox-activated macrophages that lead to mitochondrial apoptosis of cardiac cells through b-AR stimulation. Conclusions: Taken together, our data indicate that crosstalk between macrophages and cardiac cells participates in cardiac damage in response to Dox.

Methacrylated human recombinant collagen peptide as a hydrogel for manipulating and monitoring stiffness-related cardiac cell behavior

Environmental stiffness is a crucial determinant of cell function. There is a long-standing quest for reproducible and (human matrix) bio-mimicking biomaterials with controllable mechanical properties to unravel the relationship between stiffness and cell behavior. Here, we evaluate methacrylated human recombinant collagen peptide (RCPhC1-MA) hydrogels as a matrix to control 3D microenvironmental stiffness and monitor cardiac cell response. We show that RCPhC1-MA can form hydrogels with reproducible stiffness in the range of human developmental and adult myocardium. Cardiomyocytes (hPSC-CMs) and cardiac fibroblasts (cFBs) remain viable for up to 14days inside RCPhC1-MA hydrogels while the effect of hydrogel stiffness on extracellular matrix production and hPSC-CM contractility can be monitored in real-time. Interestingly, whereas the beating behavior of the hPSC-CM monocultures is affected by environmental stiffness, this effect ceases when cFBs are present. Together, we demonstrate RCPhC1-MA to be a promising candidate to mimic and control the 3D biomechanical environment of cardiac cells.

Malonyl-CoA Accumulation as a Compensatory Cytoprotective Mechanism in Cardiac Cells in Response to 7-Ketocholesterol-Induced Growth Retardation

The major oxidized product of cholesterol, 7-Ketocholesterol (7KCh), causes cellular oxidative damage. In the present study, we investigated the physiological responses of cardiomyocytes to 7KCh. A 7KCh treatment inhibited the growth of cardiac cells and their mitochondrial oxygen consumption. It was accompanied by a compensatory increase in mitochondrial mass and adaptive metabolic remodeling. The application of [U-13C] glucose labeling revealed an increased production of malonyl-CoA but a decreased formation of hydroxymethylglutaryl-coenzyme A (HMG-CoA) in the 7KCh-treated cells. The flux of the tricarboxylic acid (TCA) cycle decreased, while that of anaplerotic reaction increased, suggesting a net conversion of pyruvate to malonyl-CoA. The accumulation of malonyl-CoA inhibited the carnitine palmitoyltransferase-1 (CPT-1) activity, probably accounting for the 7-KCh-induced suppression of β-oxidation. We further examined the physiological roles of malonyl-CoA accumulation. Treatment with the inhibitor of malonyl-CoA decarboxylase, which increased the intracellular malonyl-CoA level, mitigated the growth inhibitory effect of 7KCh, whereas the treatment with the inhibitor of acetyl-CoA carboxylase, which reduced malonyl-CoA content, aggravated such a growth inhibitory effect. Knockout of malonyl-CoA decarboxylase gene (Mlycd-/-) alleviated the growth inhibitory effect of 7KCh. It was accompanied by improvement of the mitochondrial functions. These findings suggest that the formation of malonyl-CoA may represent a compensatory cytoprotective mechanism to sustain the growth of 7KCh-treated cells.

Mechano-biological phenotype in post-infarction cardiac remodeling

Ischemic heart disease is one of the leading cause of death in developed countries. In 30% of patients with heart infarction, inadequate cardiac fibrosis leads to terminal failure. We believe that local mechanical forces (inherent to the pump function of the heart) after cardiac infarction play a key role in the outcome of cardiac remodeling, in particular by modifying the response of microvascular endothelial cells (MECs), main players accompanying myocardial healing processes. Dynamic data, accessible by ultrasound, are however not widely used in the clinic, and could help to understand why patients remain refractory to treatments for heart failure. We aimed at studying the mechano-biological coupling that exists between mechanical stress applied to ischemic lesions, and the local biological response of cardiac cells. Using a mouse model of myocardial infarction (coronary artery ligation), we analyzed heart deformation using dynamic ultrasound imaging 1 month post-infarction (speckle tracking, VevoLabs). Mice were then sacrificed, and the hearts were harvested and processed for immunohistochemical analysis. Multiparametric mechanical maps (strain, displacement and velocity) were obtained using a morphometry program developed in the laboratory, and compared to a spatial transcriptomic analysis in the corresponding section planes (Visium, 10X genomics), in 4 infarcted heart of various size and localization. The transcriptomic data were validated in situ by immunofluorescence, in contiguous mouse heart sections ( Fig. 1 ). Generated big data highlight a panel of transcripts which expression highly correlates with radial strain and displacement of the heart wall. Among these factors, neuregulin-1 (involved in cardiac remodeling), and TRPC6 or PECAM-1 (sensors of mechanical forces) were found highly expressed in the mouse heart sections (immunofluorescence). Neuregulin-1 and TRPC6 strongly co-localized with MECs and coronary artery SMCs bordering the infarcted area, while PECAM-1 activation (phosphorylation) in MECs was found highly correlated with radial strain. These results support a mechano-biological coupling in infarcted hearts, modulating the expression of factors involved in its repair. Understanding the biology associated with mechanical stress could improve the management of patients after a heart attack, on the sole basis of dynamic imaging.

Sirt6 activation blocks LPS induced expression of inflammatory cytokines in cardiac cells

Sepsis induced myocardial dysfunction is a common complication that has been linked to an increased mortality. The activation of NFkB pathway and excessive production of pro‐inflammatory cytokines is considered to be one of the most important signaling pathway involved in the pathogenesis of sepsis. Earlier studies have shown that Sirt6, a member of class III of histone deacetylases, attenuates hyper‐activation of NFkB signaling that contributes to inflammation and the aging process. In the present study we tested the hypothesis whether pharmacological activation of Sirt6 can prevent LPS induced myocardial inflammation. Primary cultures of adult rat cardiac fibroblasts were treated with UBCS039, an allosteric activator of Sirt6, for 48 hours. The results showed a dose‐dependent increase in steady‐state levels of Sirt6 as well as deacetylation of its target H3K9 by Western analysis. A similar effect of UBCS039 treatment was observed in H9C2 cardiac myocytes. We also tested effects of UBCS039 on LPS induced NFkB activation and cytokine production in these cells. Our data showed that pretreatment of cardiac fibroblasts with UBCS039 for 48 hrs significantly reduced LPS (100ng/ml)‐induced phosphorylated levels of NFkB (pNFkB). By real‐time PCR analysis we found that LPS led to increased expression (4‐9 fold) of mRNA of IL‐6, IL‐1b, TLR4 and CD‐38 in cardiac fibroblasts within 6h of treatment. This effect of LPS in cardiac fibroblasts was completely blocked when cells were pretreated with UBCS039. These data thus indicated that pharmacological activation of Sirt6 is capable of blocking LPS induced inflammatory response in cardiac cells, and has the potential to alleviate sepsis induced myocardial dysfunction and related health consequences.

AKAP‐mediated regulation of extracellular matrix secretion in cardiac fibrosis

Cardiac fibroblasts represent the most abundant cell type in the myocardium and provide structural support through controlled proliferation and extracellular matrix (ECM) turnover. In response to chronic pressure overload, quiescent resident cardiac fibroblasts undergo transdifferentiation to myofibroblasts. These activated fibroblasts display increased ECM synthetic capacity and secrete large amounts of collagens. Excessive deposition of ECM results in massive interstitial fibrosis, which decreases myocardial compliance and affects electrical coupling between cardiomyocytes, causing diastolic dysfunctions and arrhythmias. In this context, deciphering the molecular mechanisms favouring increased ECM secretion and deposition in stressed hearts might be the key for the development of targeted approaches inhibiting excessive myocardial fibrosis and dysfunction.A‐kinase anchoring proteins (AKAPs) are molecular scaffolds that act as signal organizers. By recruiting and coordinating the activity of signalling enzymes in space and time they control physiological and pathological responses in cardiac cells. In this respect, our current findings suggest that AKAPs directly regulate the activity of the pathway that controls intracellular ECM protein transport and secretion in myofibroblasts. We are currently evaluating the use of molecular disruptors of selected AKAP complexes to reduce collagen secretion. These disruptors will be tested for their ability to prevent fibrosis and myocardial dysfunction in response to pressure overload.

The effect of lithium tetraborate as a novel cardioprotective agent after renal ischemia-reperfusion injury

Epidemiological studies suggest that acute kidney injury has certain effect on myocardial function. In this study, for the first time, we tested a boron compound namely lithium tetraborate an act as an anti-oxidant and anti-inflammatory agent in ischemia-reperfusion injury. For this, we employed an in vivo rat model with kidney ischemia reperfusion injury to evaluate cardiac injury to clarify the mechanisms of lithium tetraborate. The evaluation of cardiac injury through kidney artery occlusion and reperfusion rat model indicated that lithium tetraborate could (1) reduce oxidative stress-induced endothelial dysfunction; (2) attenuate the inflammatory response of cardiac cells; and (3) alleviate the apoptosis and necrosis of myocytes. In summary, lithium tetraborate demonstrates significant therapeutic properties that contribute to the amelioration of cardiac damage, and it could be a promising candidate for future applications in myocardial dysfunction.

Transcriptional Profiling of Cardiac Cells Links Age-Dependent Changes in Acetyl-CoA Signaling to Chromatin Modifications.

Metabolism has emerged as a regulator of core stem cell properties such as proliferation, survival, self-renewal, and multilineage potential. Metabolites serve as secondary messengers, fine-tuning signaling pathways in response to microenvironment alterations. Studies show a role for central metabolite acetyl-CoA in the regulation of chromatin state through changes in histone acetylation. Nevertheless, metabolic regulators of chromatin remodeling in cardiac cells in response to increasing biological age remains unknown. Previously, we identified novel cardiac-derived stem-like cells (CTSCs) that exhibit increased functional properties in the neonatal heart (nCTSC). These cells are linked to a unique metabolism which is altered with CTSC aging (aCTSC). Here, we present an in-depth, RNA-sequencing-based (RNA-Seq) bioinformatic with cluster analysis that details a distinct epigenome present in nCTSCs but not in aCTSCs. Gene Ontology (GO) and pathway enrichment reveal biological processes, including metabolism, gene regulation enriched in nCTSCs, and STRING analysis that identifies a network of genes related to acetyl-CoA that can potentially influence chromatin remodeling. Additional validation by Western blot and qRT-PCR shows increased acetyl-CoA signaling and histone acetylation in nCTSCs compared to aCTSCs. In conclusion, our data reveal that the link between metabolism and histone acetylation in cardiac cells is altered with the aging of the cardiac tissue.

Adenoviral Mediated Delivery of OSKM Factors Induces Partial Reprogramming of Mouse Cardiac Cells In Vivo

AbstractThe induction of in vivo reprogramming toward pluripotency has been demonstrated in several tissues utilizing either transgenic inducible mice or gene delivery approaches. However, the effects of exogenous reprogramming factor expression in the mammalian heart have not been previously reported. The present study aims to investigate the response of cardiac cells to ectopic Oct3/4, Sox2, Klf4, and cMyc (OSKM) expression in vivo using a non‐integrating adenoviral vector. Direct intramyocardial injection of this vector achieves effective and transient OSKM overexpression in the healthy heart and after myocardial infarction. The expression of these factors induces transient upregulation of a number of endogenous pluripotency (endo‐Oct3/4, Gdf3) and reprogramming related (Cdh1, Fut4) genes, confirming the induction of cell reprogramming. Despite the initiation of reprogramming, markers of fully de‐differentiated cells including Nanog remain silenced, consistent with a partially reprogrammed state. Furthermore, no indications of tumorigenesis or teratoma formation are observed. Overall, these data suggest that adenoviral mediated OSKM delivery can be utilized to induce partial in vivo reprogramming. However, the absence of any clear regenerative effects after myocardial infarction indicates that further optimization of vector mediated reprogramming strategies is essential to overcome barriers to therapeutic efficacy.

Phosphorylation of Troponin I finely controls the positioning of Troponin for the optimal regulation of cardiac muscle contraction

Troponin is the Ca2+ molecular switch that regulates striated muscle contraction. In the heart, troponin Ca2+ sensitivity is also modulated by the PKA-dependent phosphorylation of a unique 31-residue N-terminal extension region of the Troponin I subunit (NH2-TnI). However, the detailed mechanism for the propagation of the phosphorylation signal through Tn, which results in the enhancement of the myocardial relaxation rate, is difficult to examine within whole Tn. Several models exist for how phosphorylation modulates the troponin response in cardiac cells but these are mostly built from peptide-NMR studies and molecular dynamics simulations. Here we used a paramagnetic spin labeling approach to position and track the movement of the NH2-TnI region within whole Tn. Through paramagnetic relaxation enhancement (PRE)-NMR experiments, we show that the NH2-TnI region interacts with a broad surface area on the N-domain of the Troponin C subunit. This region includes the Ca2+ regulatory Site II and the TnI switch-binding site. Phosphorylation of the NH2-TnI both weakens and shifts this region to an adjacent site on TnC. Interspin EPR distances between NH2-TnI and TnC further reveal a phosphorylation induced re-orientation of the TnC N-domain under saturating Ca2+ conditions. We propose an allosteric model where phosphorylation triggered cooperative changes in both the interaction of the NH2-TnI region with TnC, and the re-orientation of the TnC interdomain orientation, together promote the release of the TnI switch-peptide. Enhancement of the myocardial relaxation rate then occurs. Knowledge of this unique role of phosphorylation in whole Tn is important for understanding pathological processes affecting the heart.

Abstract 257: Calreticulin Regulates Acetylation in Cardiac Cells During Endoplasmic Reticulum Stress

Background: Myocardial infarction (MI) is exacerbated by endoplasmic reticulum (ER) stress, which contributes to apoptosis signaling and tissue death in cardiomyocytes. Although the calcium-handing protein calreticulin is upregulated during MI, the role of calreticulin in the progression of ER stress remains controversial. We hypothesized that calreticulin expression accelerates ER stress via regulation of the acetylation status of ER proteins, and knockdown reduces pro-apoptotic ER stress. Methods: We examined the expression of calreticulin in human cardiac cells in response to ischemia or thapsigargin-mediated ER stress. To test the effect of calreticulin modulation on cell mortality, we generated a stable partial calreticulin knockdown line in proliferating human cardiomyocyte-derived cells. We further examined the induction and acetylation of ER stress signaling proteins, including proteins in each of the three major pathways that account for ER-stress mediated cell death. Results and Conclusions: Calreticulin is upregulated in human ischemic heart failure cardiac tissue, as well as simulated hypoxia and reoxygenation and thapsigargin-mediated ER stress. It was found that partial knockdown protects against the expression of caspase 12, CHOP, and reduces thapsigargin-driven TUNEL staining. In addition, significant changes in the acetylation of ER stress proteins and the expression of the deacetylase SIRT1 were observed. These data shed light on the role that calreticulin plays in apoptosis signaling during ER stress in cardiac cells.

The role of miR-711 in cardiac cells in response to oxidative stress and its biogenesis: a study on H9C2 cells

BackgroundOxidative stress results in cell apoptosis/death and plays a detrimental role in disease development and progression. Stressors alter the miRNA expression profile and miRNAs play a role in the cell response to stress. We previously showed that miR-711 is significantly over-expressed in extended cold ischemia reperfusion injured hearts in heart transplant. In this study, we aimed to investigate the role of miR-711 in cardiac cell damage in response to oxidative stress and how miR-711 is regulated.MethodsRat cardiac cell line H9c2 cells were cultured and exposed to oxidative conditions (Antimycin A (AA), H2O2, CoCl2, or cold hypoxia/reoxygenation (H/R)) in vitro. H9c2 cells were transfected with miR-711 mimics, miR-711 inhibitors, or small interference RNA, using transfection reagents. The expression of miR-711 was measured by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Cell apoptosis/death was detected by flow cytometry and an IncuCyte system. Mitochondrial damage was detected by measuring the mitochondria membrane potential by flow cytometry. Gene expression was detected by qRT-PCR at the mRNA level and Western blotting and immunocytochemistry staining at the protein level.ResultsWe found that miR-711 was significantly up-regulated in cells treated with H2O2, AA, CoCl2, and cold H/R. Over-expression of miR-711 increased cell apoptosis/death induced by AA and H/R whereas cell death was reduced by miR-711 inhibitors. MiR-711 induced cell death through negative regulation of angiopoietin 1 (Ang-1), fibroblast growth factor 14 (FGF14) and calcium voltage-gated channel subunit alpha1C (Cacna1c) genes. Both knockdown of hypoxia inducible factor 1α (HIF-1α) and inactivation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NFКB) pathway inhibited over-expression of miR-711.ConclusionOxidative stress increases the expression of miR-711. Over-expression of miR-711 induces cell apoptosis/death. HIF-1α and NFКB regulate miR-711 in H9c2 cells during oxidative stress. miR-711 is a new target for preventing oxidative stress.

SIRT3-mediated inhibition of FOS through histone H3 deacetylation prevents cardiac fibrosis and inflammation

Sirtuin 3 (SIRT3) is a deacetylase that modulates proteins that control metabolism and protects against oxidative stress. Modulation of SIRT3 activity has been proposed as a promising therapeutic target for ameliorating metabolic diseases and associated cardiac disturbances. In this study, we investigated the role of SIRT3 in inflammation and fibrosis in the heart using male mice with constitutive and systemic deletion of SIRT3 and human cardiac AC16 cells. SIRT3 knockout mice showed cardiac fibrosis and inflammation that was characterized by augmented transcriptional activity of AP-1. Consistent with this, SIRT3 overexpression in human and neonatal rat cardiomyocytes partially prevented the inflammatory and profibrotic response induced by TNF-α. Notably, these effects were associated with a decrease in the mRNA and protein levels of FOS and the DNA-binding activity of AP-1. Finally, we demonstrated that SIRT3 inhibits FOS transcription through specific histone H3 lysine K27 deacetylation at its promoter. These findings highlight an important function of SIRT3 in mediating the often intricate profibrotic and proinflammatory responses of cardiac cells through the modulation of the FOS/AP-1 pathway. Since fibrosis and inflammation are crucial in the progression of cardiac hypertrophy, heart failure, and diabetic cardiomyopathy, our results point to SIRT3 as a potential target for treating these diseases.

Non-Invasive Plasmonic-Based Real-Time Characterization of Cardiac Drugs on Cardiomyocytes Functional Behavior.

In the fabrication of cardiac tissue, an important factor is continuous measurement of its contraction features. A module that allows for a dynamic system capable of noninvasive and label-free monitoring of the contraction profile under administering chemicals and drugs is highly valuable for understanding accurate tissue mechanobiology. In this research, we have successfully demonstrated the use of surface plasmon resonance (SPR) technology for the first time to characterize the contractility of cardiac cells in response to Blebbistatin and ATP drug exposure in real tme. An optimal flow rate of 10 μL/min was selected for a continuous flow of warm media,and 10 μM drug administration effect was detected with high spatiotemporal sensitivity on contracting cardiomyocytes. Our drug screening has identified the source of the SPR periodic signal to be direct cell contraction rather than action potentials or calcium signaling. Per our results, SPR has high potential in applications in least-interference real-time and label-free tissue characterizations and cellular properties analysis from a functional and structural point of view.

Testing the limits of cardiac electrophysiology models through systematic variation of current

Mathematical models of the electrical response of cardiac cells are used to help develop an understanding of the electrophysiological properties of cardiac cells. Increasingly complex models are being developed in an effort to enhance the biological fidelity of the models and potentially increase their ability to predict electrical dynamics observed in vivo and in vitro. However, as the models increase in size, they have a tendency to become unstable and are highly sensitive to changes in established parameters. This means that such models might be unable to accurately predict person-to-person variability, dynamical changes due to disease pathologies that alter ionic currents, or the effect of treatment with antiarrhythmics. In this paper, we test the predictive limits of two mathematical models by altering the conductance of Ca2+, Na+, and K+ channels. We assess changes in action potential duration (APD), rate dependence, hysteresis, dynamical behavior, and restitution as conductance is varied. We find model predictions of abrupt changes in measured quantities and differences in the predictions of the two models that might be missed in a less systematic approach. These features can be compared to experimental observations to help assess the fidelity of the models.

Characterization of dynamic gene networks in response to thoracotomy, ischemia-reperfusion in mouse heart

Myocardial infarction is an irreversible death of cardiac cells in response to prolonged ischemia and ischemia-reperfusion injury. Experimental designs and analytical pipelines used in time-series ischemia-reperfusion (IR) transcriptomic studies represent major challenges in the understanding of progression of such multifactorial diseases. In this study, we aim to provide a pipeline for the analysis of kinetical transcriptomics, characterize the change in gene expression profiles in response to surgical preparations prior IR and measure the dynamic gene regulation during IR in the left ventricle of mouse heart. Eight to twelve- weeks old C57BL/6 mice were anesthetized, undergone surgical preparations with and without IR and sacrificed at different time points (8 animals per time point) of the IR sequence. RNA-seq data from sham myocardium, ischemic and non-ischemic myocardium of IR mice are analyzed, clustered and functionally characterized. Gene expression analysis by DESeq2 yielded a total of 1006, 446 and 3878 differentially expressed genes in response to surgical interventions, remote and ischemia-reperfusion effect. Temporal clustering by weighted gene co-expression network analysis (WGCNA) and gene ontology analysis have shown that surgical preparations prior IR initiates inflammatory response mediated mainly by the phenotypic shift between the different macrophages’ subtypes and the infiltration of neutrophils to the heart few hours post-surgery. This study not only provides a comprehensive framework for kinetical transcriptomic studies, but also sheds light on the importance of considering the change of gene expression profiles driven by the thoracotomy effect.