Hypoxia and re-oxygenation effects on human cardiomyocytes cultured on polycaprolactone and polyurethane nanofibrous mats.

Heart diseases are caused mainly by chronic oxygen insufficiency (hypoxia), leading to damage and apoptosis of cardiomyocytes. Research into the regeneration of a damaged human heart is limited due to the lack of cellular models that mimic damaged cardiac tissue. Based on the literature, nanofibrous mats affect the cardiomyocyte morphology and stimulate the growth and differentiation of cells cultured on them; therefore, nanofibrous materials can support the production of in vitro models that faithfully mimic the 3D structure of human cardiac tissue. Nanofibrous mats were used as scaffolds for adult primary human cardiomyocytes (HCM) and immature human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). This work focuses on understanding the effects of hypoxia and re-oxygenation on human cardiac cells cultured on polymer nanofibrous mats made of poly(ε-caprolactone) (PCL) and polyurethane (PU). The expression of selected genes and proteins in cardiomyocytes during hypoxia and re-oxygenation were evaluated. In addition, the type of cell death was analyzed. To the best of our knowledge, there are no studies on the effects of hypoxia on cardiomyocyte cells cultured on nanofibrous mats. The present study aimed to use nanofiber mats as scaffolds that structurally could mimic cardiac extracellular matrix. Understanding the impact of 3D structural properties in vitro cardiac models on different human cardiomyocytes is crucial for advancing cardiac tissue engineering and regenerative medicine. Observing how 3D scaffolds affect cardiomyocyte function under hypoxic conditions is necessary to understand the functioning of the entire human heart.

miR-29a activates expression of α-cardiac myosin heavy chain via ß1 thyroid hormone receptor in neonatal rats.

Introduction: MicroRNAs (miRs) are small noncoding RNAs which are regulators of gene expression and also regulate the genes in heart tissues. The aim of the study was to evaluate the effect of miRs on the expression level of myosin heavy chain (MHC), which is responsible for regulation of cardiac functions in neonatal rat ventricular myocytes and mice. Material and methods: The miRs were suppressed in neonatal rat ventricular myocytes using small interfering RNAs (siRNAs) against Dicer followed by evaluation of MHC levels. For in vivo study the C57 black/6 Jacksonian mice were subjected to the transverse aortic constriction (TAC) procedure. Results: The Dicer siRNA suppressed the endogenous miRs and the α-MHC gene but failed to down-regulate the ß-MHC. Among the 17 selected miRs, miR-29a was found to up-regulate the α-MHC gene significantly but not ß-MHC. The expression of α-MHC was suppressed by silencing the expression of miR-29a. Bioinformatics study done by TargetScan suggested thyroid hormone receptor-ß1 (TR-ß1) as a potential target of miR-29a. Additionally, miR-29a was found to regulate the expression of α-MHC via TR-ß1 signaling. Conclusions: The findings of the present study indicated that miR-29a modulates expression of α-the MHC gene by targeting TR-ß1 in cardiac cells. The study may provide a new direction for treating cardiac failure and cardiac hypertrophy.

What Powers Trastuzumab's Cardiotoxicity? Decoding Mitochondrial-Related Gene Expression Through Integrative Review and Meta-Analysis in Cardiomyocytes.

Trastuzumab is a monoclonal antibody used in oncotherapy for HER2-positive tumors. However, as an adverse effect, trastuzumab elevates the risk of heart failure, implying the involvement of energy production and mitochondrial processes. Past studies with transcriptome analysis have offered insights on pathways related to trastuzumab safety and toxicity but limited study sizes hinder conclusive findings. Therefore, we meta-analyzed mitochondria-related gene expression data in trastuzumab-treated cardiomyocytes. We searched the transcriptome databases for trastuzumab-treated cardiomyocytes in the ArrayExpress, DDBJ Omics Archive, Gene Expression Omnibus, Google Scholar, PubMed, and Web of Science repositories. A subset of 1270 genes related to mitochondrial functions (biogenesis, organization, mitophagy, and autophagy) was selected from the Kyoto Encyclopedia of Genes and Genomes and Gene Ontology Resource databases to conduct the present meta-analysis using the Metagen package (Study register at PROSPERO: CRD42021270645). Three datasets met the inclusion criteria and 1243 genes were meta-analyzed. We observed 69 upregulated genes after trastuzumab treatment which were related mainly to autophagy (28 genes) and mitochondrial organization (28 genes). We also found 37 downregulated genes which were related mainly to mitochondrial biogenesis (11 genes) and mitochondrial organization (24 genes). The present meta-analysis indicates that trastuzumab therapy causes an unbalance in mitochondrial functions, which could, in part, help explain the development of heart failure and yields a list of potential molecular targets. These findings contribute to our understanding of the molecular mechanisms underlying the cardiotoxic effects of trastuzumab and may have implications for the development of targeted therapies to mitigate such effects.

H2S Protects from Rotenone-Induced Ferroptosis by Stabilizing Fe-S Clusters in Rat Cardiac Cells.

Hydrogen sulfide (H2S) has been recently recognized as an important gasotransmitter with cardioprotections, and iron is vital for various cellular activities. This study explored the regulatory role of H2S on iron metabolism and mitochondrial functions in cultured rat cardiac cells. Rotenone, a mitochondrial complex I inhibitor, was used for establishing an in vitro model of ischemic cell damage. It was first found that rotenone induced oxidative stress and lipid peroxidation and decreased mitochondrial membrane potential and ATP generation, eventually causing cell death. The supplement of H2S at a physiologically relevant concentration protected from rotenone-induced ferroptotic cell death by reducing oxidative stress and mitochondrial damage, maintaining GPx4 expression and intracellular iron level. Deferiprone, an iron chelator, would also protect from rotenone-induced ferroptosis. Further studies demonstrated that H2S inhibited ABCB8-mediated iron efflux from mitochondria to cytosol and promoted NFS1-mediated Fe-S cluster biogenesis. It is also found that rotenone stimulated iron-dependent H2S generation. These results indicate that H2S would protect cardiac cells from ischemic damage through preserving mitochondrial functions and intracellular Fe-S cluster homeostasis.

Comparative In Vitro Study of the Cytotoxic Effects of Doxorubicin's Main Metabolites on Cardiac AC16 Cells Versus the Parent Drug.

Doxorubicin (DOX; also known as adriamycin) serves as a crucial antineoplastic agent in cancer treatment; however, its clinical utility is hampered by its' intrinsic cardiotoxicity. Although most DOX biotransformation occurs in the liver, a comprehensive understanding of the impact of DOX biotransformation and its' metabolites on its induced cardiotoxicity remains to be fully elucidated. This study aimed to explore the role of biotransformation and DOX's main metabolites in its induced cardiotoxicity in human differentiated cardiac AC16 cells. A key discovery from our study is that modulating metabolism had minimal effects on DOX-induced cytotoxicity: even so, metyrapone (a non-specific inhibitor of cytochrome P450) increased DOX-induced cytotoxicity at 2 µM, while diallyl sulphide (a CYP2E1 inhibitor) decreased the 1 µM DOX-triggered cytotoxicity. Then, the toxicity of the main DOX metabolites, doxorubicinol [(DOXol, 0.5 to 10 µM), doxorubicinone (DOXone, 1 to 10 µM), and 7-deoxydoxorubicinone (7-DeoxyDOX, 1 to 10 µM)] was compared to DOX (0.5 to 10 µM) following a 48-h exposure. All metabolites evaluated, DOXol, DOXone, and 7-DeoxyDOX caused mitochondrial dysfunction in differentiated AC16 cells, but only at 2 µM. In contrast, DOX elicited comparable cytotoxicity, but at half the concentration. Similarly, all metabolites, except 7-DeoxyDOX impacted on lysosomal ability to uptake neutral red. Therefore, the present study showed that the modulation of DOX metabolism demonstrated minimal impact on its cytotoxicity, with the main metabolites exhibiting lower toxicity to AC16 cardiac cells compared to DOX. In conclusion, our findings suggest that metabolism may not be a pivotal factor in mediating DOX's cardiotoxic effects.

Improving rodents and humans cardiac cell maturityin vitrothrough polycaprolactone and polyurethane nanofibers.

Currently, numerous studies are conducted using nanofibers as a scaffold for culture cardiac cells; however, there still needs to be more research evaluating the impact of the physicochemical properties of polymer nanofibers on the structure and function of cardiac cells. We have studied how poly(ϵ-caprolactone) and polyurethane nanofibrous mats with different physicochemical properties influence the viability, morphology, orientation, and maturation of cardiac cells. For this purpose, the cells taken from different species were used. They were rat ventricular cardiomyoblasts (H9c2), mouse atrial cardiomyocytes (CMs) (HL-1), and human ventricular CMs. Based on the results, it can be concluded that cardiac cells cultured on nanofibers exhibit greater maturity in terms of orientation, morphology, and gene expression levels compared to cells cultured on polystyrene plates. Additionally, the physicochemical properties of nanofibers affecting the functionality of cardiac cells from different species and different parts of the heart were evaluated. These studies can support research on understanding and explaining mechanisms leading to cellular maturity present in the heart and the selection of nanofibers that will effectively help the maturation of CMs.

Nitric Oxide Plays a Dual Role in Cardiorenal Syndrome in Vitro Model.

BACKGROUND/AIMS: Nitric oxide (NO) plays a dual role, acting as both an oxidant and a reducer, with various effects depending on its concentration and environment. Acute kidney injury's (AKI) pathogenesis observed in cardiorenal syndrome 3 (CRS 3) involves inflammatory responses and the production of reactive oxygen and nitrogen species. However, the role of NO on the development of CRS 3 is still not completely understood. The study aimed to mimic CRS 3 in vitro and investigate NO signaling and inflammatory molecules. METHODS: Thus, HEK293 cells were submitted to normoxia (NX) or hypoxia (HX) protocols for 16 h followed by 3 h of reoxygenation, treated or not with L-NAME. Conditionate medium by HEK293 was transferred to H9c2 for 24 h. Cellular viability was evaluated by MTT assay, real time PCR was used to analyze gene expression and NO content were evaluated in the intra and extracellular medium by amperimetry. RESULTS: Carbonic anhydrase 9 (CA9) expression increased 2.9-fold after hypoxia. Hypoxia reduced 18 % cell viability in HEK293 that was restored by L-NAME treatment. The sum of nitrite (NO2-) and S-nitrosothiol (S-NO) fractions in HEK293 cells showed a substantial decrease on NO intracellular content (38 %). Both IL-6 and IL-10 decreased in all groups compared to NX cells. Besides TNF-α and Bax/Bcl2 ratio increased in hypoxia (approximately 120-fold and 600-fold, respectively) and L-NAME restored this effect. Regarding H9c2 cells, the S-NO fractions showed a substantial decrease in extracellular content after HX (17%) that was not restored by L-NAME. IL-1ß decreases in cardiac cells treated with conditioned medium from HX/L-NAME. CONCLUSION: In conclusion this study highlights the complex interplay of NO and inflammatory factors in hypoxia-induced renal and cardiac cell responses, with potential implications for cardiorenal syndrome.

BEaTS-ß: an open-source electromechanical bioreactor for simulating human cardiac disease conditions.

Heart disease remains the leading cause of worldwide mortality. Although the last decades have broadened our understanding of the biology behind the pathologies of heart disease, ex vivo systems capable of mimicking disease progression and abnormal heart function using human cells remain elusive. In this contribution, an open-access electromechanical system (BEaTS-ß) capable of mimicking the environment of cardiac disease is reported. BEaTS-ß was designed using computer-aided modeling to combine tunable electrical stimulation and mechanical deformation of cells cultured on a flexible elastomer. To recapitulate the clinical scenario of a heart attack more closely, in designing BEaTS-ß we considered a device capable to operate under hypoxic conditions. We tested human induced pluripotent stem cell-derived cardiomyocytes, fibroblasts, and coronary artery endothelial cells in our simulated myocardial infarction environment. Our results indicate that, under simulated myocardium infarction, there was a decrease in maturation of cardiomyocytes, and reduced survival of fibroblasts and coronary artery endothelial cells. The open access nature of BEaTS-ß will allow for other investigators to use this platform to investigate cardiac cell biology or drug therapeutic efficacy in vitro under conditions that simulate arrhythmia and/or myocardial infarction.

Amiodarone but not propafenone impairs bioenergetics and autophagy of human myocardial cells.

Cardiac and extra-cardiac side effects of common antiarrhythmic agents might be related to drug-induced mitochondrial dysfunction. Supratherapeutic doses of amiodarone have been shown to impair mitochondria in animal studies, whilst influence of propafenone on cellular bioenergetics is unknown. We aimed to assess effects of protracted exposure to pharmacologically relevant doses of amiodarone and propafenone on cellular bioenergetics and mitochondrial biology of human and mouse cardiomyocytes. In this study, HL-1 mouse atrial cardiomyocytes and primary human cardiomyocytes derived from the ventricles of the adult heart were exposed to 2 and 7 µg/mL of either amiodarone or propafenone. After 24 h, extracellular flux analysis and confocal laser scanning microscopy were used to measure mitochondrial functions. Autophagy was assessed by western blots and live-cell imaging of lysosomes. In human cardiomyocytes, amiodarone significantly reduced mitochondrial membrane potential and ATP production, in association with an inhibition of fatty acid oxidation and impaired complex I- and II-linked respiration in the electron transport chain. Expectedly, this led to increased anaerobic glycolysis. Amiodarone increased the production of reactive oxygen species and autophagy was also markedly affected. In contrast, propafenone-exposed cardiomyocytes did not exert any impairment of cellular bioenergetics. Similar changes after amiodarone treatment were observed during identical experiments performed on HL-1 mouse cardiomyocytes, suggesting a comparable pharmacodynamics of amiodarone among mammalian species. In conclusion, amiodarone but not propafenone in near-therapeutic concentrations causes a pattern of mitochondrial dysfunction with affected autophagy and metabolic switch from oxidative metabolism to anaerobic glycolysis in human cardiomyocytes.

Advances in the study of exosomes derived from mesenchymal stem cells and cardiac cells for the treatment of myocardial infarction.

Acute myocardial infarction has long been the leading cause of death in coronary heart disease, which is characterized by irreversible cardiomyocyte death and restricted blood supply. Conventional reperfusion therapy can further aggravate myocardial injury. Stem cell therapy, especially with mesenchymal stem cells (MSCs), has emerged as a promising approach to promote cardiac repair and improve cardiac function. MSCs may induce these effects by secreting exosomes containing therapeutically active RNA, proteins and lipids. Notably, normal cardiac function depends on intracardiac paracrine signaling via exosomes, and exosomes secreted by cardiac cells can partially reflect changes in the heart during disease, so analyzing these vesicles may provide valuable insights into the pathology of myocardial infarction as well as guide the development of new treatments. The present review examines how exosomes produced by MSCs and cardiac cells may influence injury after myocardial infarction and serve as therapies against such injury. Video Abstract.

Paracrine effects of mir-210-3p on angiogenesis in hypoxia-treated c-kit-positive cardiac cells.

Objective: Treatment with c-kit-positive cardiac cells (CPCs) has been shown to improve the prognosis of ischemic heart disease. MicroRNAs (miRNAs) confer protection by enhancing the cardiac repair process, but their specific functional mechanisms remain unclear. This study aimed to screen for differentially expressed miRNAs in CPCs under hypoxia and explore their effects on the function of CPCs.Methods: We harvested CPCs from C57 adult mice and later performed a high-throughput miRNA sequencing for differential expression profiling analysis. Subsequently, we intervened with the differentially expressed gene miR-210-3p in CPCs and detected changes in the secretion of angiogenesis-related factors through a protein-chip analysis. Finally, we applied CPC supernatants of different groups as conditioned medium to treat mouse cardiac microvascular endothelial cells (CMECs) and further investigated the functional effects of miR-210-3p on c-kit+CPCs under ischemia and hypoxia conditions.Results: The miR-210-3p was highly increased in hypoxia-treated CPCs. Protein-chip detection revealed that CPCs expressed cytokines such as FGF basic, angiogenin, and vascular endothelial growth factor (VEGF) and that hypoxia enhanced their release. Silencing miR-210-3p resulted in a reduction in the release of these angiogenesis-related factors. In addition, the conditioned medium of hypoxia-treated CPCs promoted the proliferation, migration, and tube-forming capabilities of CMECs. In contrast, the conditioned media of CPCs with silenced miR-210-3p after hypoxia decreased the proliferation, migration, and tube-forming ability of CMEC.Conclusions: The CPCs exert proangiogenic effects via paracrine pathways mediated by miR-210-3p. Upregulation of miR-210-3p in hypoxia-treated CPCs may enhance their paracrine function by regulating the secretion of angiogenic factors, thereby promoting angiogenesis in ischemic heart disease.

An integrative review of nonobvious puzzles of cellular and molecular cardiooncology.

Oncologic patients are subjected to four major treatment types: surgery, radiotherapy, chemotherapy, and immunotherapy. All nonsurgical forms of cancer management are known to potentially violate the structural and functional integrity of the cardiovascular system. The prevalence and severity of cardiotoxicity and vascular abnormalities led to the emergence of a clinical subdiscipline, called cardiooncology. This relatively new, but rapidly expanding area of knowledge, primarily focuses on clinical observations linking the adverse effects of cancer therapy with deteriorated quality of life of cancer survivors and their increased morbidity and mortality. Cellular and molecular determinants of these relations are far less understood, mainly because of several unsolved paths and contradicting findings in the literature. In this article, we provide a comprehensive view of the cellular and molecular etiology of cardiooncology. We pay particular attention to various intracellular processes that arise in cardiomyocytes, vascular endothelial cells, and smooth muscle cells treated in experimentally-controlled conditions in vitro and in vivo with ionizing radiation and drugs representing diverse modes of anti-cancer activity.

Mitochondria-derived damage-associated molecular patterns and inflammation in the ischemic-reperfused heart.

Cardiac cell death after myocardial infarction release endogenous structures termed damage-associated molecular patterns (DAMPs) that trigger the innate immune system and initiate a sterile inflammation in the myocardium. Cardiomyocytes are energy demanding cells and 30% of their volume are mitochondria. Mitochondria are evolutionary endosymbionts originating from bacteria containing molecular patterns similar to bacteria, termed mitochondrial DAMPs (mDAMPs). Consequently, mitochondrial debris may be particularly immunogenic and damaging. However, the role of mDAMPs in myocardial infarction is not clarified. Identifying the most harmful mDAMPs and inhibiting their early inflammatory signaling may reduce infarct size and the risk of developing post-infarct heart failure. The focus of this review is the role of mDAMPs in the immediate pro-inflammatory phase after myocardial infarction before arrival of immune cells in the myocardium. We discuss different mDAMPs, their role in physiology and present knowledge regarding their role in the inflammatory response of acute myocardial infarction.

Autophagy (but not metabolism) is a key event in mitoxantrone-induced cytotoxicity in differentiated AC16 cardiac cells.

Mitoxantrone (MTX) is an antineoplastic agent used to treat advanced breast cancer, prostate cancer, acute leukemia, lymphoma and multiple sclerosis. Although it is known to cause cumulative dose-related cardiotoxicity, the underlying mechanisms are still poorly understood. This study aims to compare the cardiotoxicity of MTX and its' pharmacologically active metabolite naphthoquinoxaline (NAPHT) in an in vitro cardiac model, human-differentiated AC16 cells, and determine the role of metabolism in the cardiotoxic effects. Concentration-dependent cytotoxicity was observed after MTX exposure, affecting mitochondrial function and lysosome uptake. On the other hand, the metabolite NAPHT only caused concentration-dependent cytotoxicity in the MTT reduction assay. When assessing the effect of different inhibitors/inducers of metabolism, it was observed that metyrapone (a cytochrome P450 inhibitor) and phenobarbital (a cytochrome P450 inducer) slightly increased MTX cytotoxicity, while 1-aminobenzotriazole (a suicide cytochrome P450 inhibitor) decreased fairly the MTX-triggered cytotoxicity in differentiated AC16 cells. When focusing in autophagy, the mTOR inhibitor rapamycin and the autophagy inhibitor 3-methyladenine exacerbated the cytotoxicity caused by MTX and NAPHT, while the autophagy blocker, chloroquine, partially reduced the cytotoxicity of MTX. In addition, we observed a decrease in p62, beclin-1, and ATG5 levels and an increase in LC3-II levels in MTX-incubated cells. In conclusion, in our in vitro model, neither metabolism nor exogenously given NAPHT are major contributors to MTX toxicity as seen by the residual influence of metabolism modulators used on the observed cytotoxicity and by NAPHT's low cytotoxicity profile. Conversely, autophagy is involved in MTX-induced cytotoxicity and MTX seems to act as an autophagy inducer, possibly through p62/LC3-II involvement.

Hyper-transcription of heat shock factors and heat shock proteins safeguard caprine cardiac cells against heat stress.

The present study was undertaken to document the transcriptional abundance of heat shock factors and heat shock proteins and their role in survivability of caprine cardiac cells during heat stress. Cardiac tissues were collected from different goats (n = 6) and primary cardiac cell culture was done in an atmosphere of 5% CO2 and 95% air at 38.5 °C. Cardiac cells accomplished 70-75% confluence after 72 h of incubation. Confluent cardiac cells were exposed to heat stress at 42 °C for 0 (control), 20, 60, 100 and 200 min. Quantitative RT-PCR for ß2m (internal control), heat shock factors (HSF1, HSF2, HSF4, HSF5), heat shock proteins (HSP10, HSP40), and Caspase-3 was done and their transcriptional abundance was assessed by Pfaffl method. Transcriptional abundance of HSF1, HSF2, and HSF4 did not change at 20 min, increased (P < 0.05) from 60 to 200 min and reached zenith at 200 min of heat exposure. However, transcriptional abundance of HSF5 was gradually escalated (P < 0.05) from 20 to 200 min and registered highest at 200 min of heat exposure. Transcriptional abundance of HSP10 and HSP40 followed an similar pattern like that of HSF5. Transcriptional abundance of Caspase-3 was significantly down-regulated at 200 min of heat exposure. It could be speculated that over-expression of HSFs and HSPs might have reduced Caspase-3 expression at 200 min of heat exposure suggesting their involvement in cardiac cells survival under heat stress. Moreover, hyper-expression of HSFs and HSPs could maintain the integrity and endurance of cardiac tissues of goats under heat stress.

Cell culture: a promising environment for research on cardiology / Cultivos celulares: un entorno promisorio para la investigación en cardiología

Abstract At present, tissue engineering is transforming the area of cardiovascular regenerative medicine, which combines the principles and methods of materials engineering and biological sciences, interacting with biochemical and physicochemical factors, for the understanding of their structure-function relationship. Thus, the course of diseases is reoriented by implementing methods and procedures involved in the regeneration of organs and tissues by means of the interaction with biocompatible matrices, pre-treated organs or stem cell management, among others, thus recovering the functionality in the system affected by acquired pathologies, alterations or congenital defects. Consequently, these procedures are increasingly becoming one the most promising treatment alternative for patients who suffer from any type of functional deficit. Known that all these possibilities make cell cultures a promising study environment to be used in biomedical applications, especially in tissue engineering and regenerative medicine, this manuscript presents a general reviews of established cell lines or primary tissue lines and how cell cultures serve as a model before experimental work on laboratory animals and human subjects which makes it a valuable tool for broad models of study in the research on cardiology.

Resumen En la actualidad, la ingeniería de tejidos está transformando el área de la medicina regenerativa cardiovascular, combinando los principios y métodos de la ingeniería de materiales y las ciencias biológicas, interactuando entre factores bioquímicos y fisicoquímicos, para la comprensión de su relación estructura-función. Así, el curso de las enfermedades se viene a reorientar mediante la implementación de métodos y procedimientos implicados en la regeneración de órganos y tejidos a través de la interacción con matrices biocompatibles, órganos pretratados o manejo de células madre, entre otros, recuperando así la funcionalidad en el sistema afectado por enfermedades adquiridas y alteraciones o defectos congénitos. En consecuencia, estos procedimientos se están convirtiendo en una de las alternativas de tratamiento cada vez más prometedoras para los pacientes que sufren de algún tipo de alteración funcional. Considerando que todas estas posibilidades hacen de los cultivos celulares un entorno de estudio prometedor para ser utilizado en aplicaciones biomédicas, especialmente en ingeniería de tejidos y medicina regenerativa, este manuscrito presenta una revisión general de las líneas celulares establecidas o líneas de tejido primario y cómo los cultivos celulares sirven como modelo de evaluación antes del trabajo experimental en animales de laboratorio y sujetos humanos, lo cual los convierte en una herramienta valiosa para amplios modelos de estudio en la investigación en cardiología.

Application of Three-Dimensional Culture Method in the Cardiac Conduction System Research.

Congenital heart defects (CHD) are the most common type of birth defects. Several human case studies and genetically altered animal models have identified abnormalities in the development of ventricular conduction system (VCS) in the heart. While cell-based therapies hold promise for treating CHDs, translational efforts are limited by the lack of suitable in vitro models for feasibility and safety studies. A better understanding of cell differentiation pathways can lead to development of cell-based therapies for individuals living with CHD/VCS disorders. Here, we describe a new and reproducible 3-D cell culture method for studying cardiac cell lineage differentiation in vitro. We used primary ventricular cells isolated from embryonic day 11.5 (E11.5) mouse embryos, which can differentiate into multiple cardiac cell types including VCS cells. We compared 3-D cultures with three types of basement membrane extracts (BME) for their abilities to support E11.5 ventricular cell differentiation. In addition, the effects of atrial natriuretic peptide (ANP) and an inhibitor for its high affinity receptor were tested on cell differentiation in 3-D cultures. Following the cell culture, protocols for immunofluorescence imaging, cell extraction and protein isolation from the 3-D culture matrix and in-cell western methods are described. Further, these approaches can be used to study the effects of various ligands and genetic interventions on VCS cell development. We propose that these methodologies may also be extended for differentiation studies using other sources of stem cells such as induced pluripotent stem cells.

Titanium Dioxide (E171) Induces Toxicity in H9c2 Rat Cardiomyoblasts and Ex Vivo Rat Hearts.

Cardiovascular diseases are the leading cause of death worldwide. Food-grade TiO2 (E171) is the most widely used additive in the food industry. Existing evidence shows TiO2 nanoparticles reach systemic circulation through biological barriers, penetrate cell membranes, accumulate in cells of different organs, and cause damage; however, their effects on cardiac cells and the development of heart diseases are still unexplored. Therefore, in this work, we tested E171 toxicity in rat cardiomyoblasts and hearts. E171 internalization and impact on cell viability, proliferation, mitochondria, lysosomes, F-actin distribution, and cell morphology were evaluated in H9c2 cells. Additionally, effects of E171 were measured on cardiac function in ex vivo rat hearts. E171 was uptaken by cells and translocated into the cytoplasm. E171 particles changed cell morphology reducing proliferation and metabolic activity. Higher caspase-3 and caspase-9 expression as well as Tunel-positive cells induced by E171 exposure indicate apoptotic death. Mitochondrial and lysosome alterations resulting from mitophagy were detected after 24 and 48 h exposure, respectively. Additionally, high E171 concentrations caused rearrangements of the F-actin cytoskeleton. Finally, hearts exposed to E171 showed impaired cardiac function. These results support E171 toxicity in cardiac cells in vitro altering cardiac function in an ex vivo model, indicating that consumption of this food additive could be toxic and may lead to the development of cardiovascular disease.

Restoring anatomical complexity of a left ventricle wall as a step toward bioengineering a human heart with human induced pluripotent stem cell-derived cardiac cells.

The heart is a highly complex, multicellular solid organ with energy-demanding processes that require a dense vascular network, extensive cell-cell interactions, and extracellular matrix (ECM)-mediated crosstalk among heterogeneous cell populations. Here, we describe the regeneration of left ventricular (LV) wall using decellularized whole rabbit heart scaffolds recellularized exclusively with human induced pluripotent stem cell-derived endothelial cells, cardiomyocytes, and other cardiac cell types. Cells were sequentially delivered to the scaffold using an optimized endothelial cell:cardiomyocyte media. Macroscopic assessment after 60 days showed that the LV wall of recellularized hearts was anatomically restored to full thickness from base to apex and endocardium to epicardium. Histologic analysis of the recellularized LV wall revealed a heterogeneous pool of cardiac cells containing aligned cardiac troponin T-positive cells in close contact with ECM; vessels varied from large artery-like, surrounded by smooth muscle actin+ cells, to capillary-like. Vessel patency was demonstrated after perfusion of recellularized hearts transplanted into the femoral artery bed of a pig. The construct exhibited visible beating and responded to chronotropic drug administration. These results demonstrate the ability to tissue engineer a vascularized, full-thickness LV wall with an unparalleled level of microanatomical organization and multicellular composition, using decellularized ECM and human cardiomyocytes, endothelial cells, and other cardiac cell types. STATEMENT OF SIGNIFICANCE: Decellularized extracellular matrix (ECM) is a bioactive template for tissue engineering, but recellularizing acellular whole heart scaffolds is challenging. Here, we successfully revascularized and repopulated a large, full-thickness portion of a ventricle using human induced pluripotent stem cell-derived endothelial and cardiac cells. At 60 days, histologic studies showed that the microanatomical organization and cellular composition of this region was similar to that of the native heart. The recellularized heart showed visible beating and responded appropriately to heartbeat-altering drugs. Vessels surrounded by smooth muscle cells and endothelial cells supported blood flow through the vessels of a recellularized heart that was surgically connected to a pig femoral artery. These findings move this approach closer to the possibility of clinical translation.