Physiological conditioning by electric field stimulation promotes cardiomyogenic gene expression in human cardiomyocyte progenitor cells

Analysis of the role of perfusion, mechanical, and electrical stimulation in bioreactors for cardiac tissue engineering

Since cardiovascular diseases (CVDs) are globally one of the leading causes of death, of which myocardial infarction (MI) can cause irreversible damage and decrease survivors' quality of life, novel therapeutics are needed. Current approaches such as organ transplantation do not fully restore cardiac function or are limited. As a valuable strategy, tissue engineering seeks to obtain constructs that resemble myocardial tissue, vessels, and heart valves using cells, biomaterials as scaffolds, biochemical and physical stimuli. The latter can be induced using a bioreactor mimicking the heart's physiological environment. An extensive review of bioreactors providing perfusion, mechanical and electrical stimulation, as well as the combination of them is provided. An analysis of the stimulations' mechanisms and modes that best suit cardiac construct culture is developed. Finally, we provide insights into bioreactor configuration and culture assessment properties that need to be elucidated for its clinical translation.

Study on the Influence of Shear Stress and Pulse Electrical Stimulation to the Growth of Cardiomyocytes

Engineered myocardial tissue is expected to be used in the treatment of myocardial defects and other diseases, and one of the keys is to construct a suitable environment for the culture of myocardial tissue in vitro. In this study, flow shear stress and pulse electrical stimulation were applied to cardiomyocytes with a self-designed device by simulating the mechanical and electrical physiological microenvironment of myocardial tissue. The strength and duration of pulse electrical stimulation as well as the intensity of shear stress were studied in detail to optimize the experimental parameters. Concretely, 100 mV pulse electrical stimulation (1 Hz and 10 ms pulse width) and 10 dyn/cm² shear stress were used for studying the influence of combined mechanical-electrical stimulation to the growth of cardiomyocytes. The mechanical factor of the combined stimulation promoted the expression of α-cardiac actin mRNA, the electrical factor caused an increase in Cx-43 mRNA expression, and shear stress and pulse electrical stimulation showed a synergistic action on the expression of GATA-4 mRNA. It indicated that combined mechanical-electrical stimulation had a better effect on the functionalized culture of cardiomyocytes, which provided an important theoretical basis for the further construction of in vitro engineered myocardial tissue.

Use of weak DC electric fields to rapidly align mammalian cells

Objective.The ability to modulate cell morphology has clinical relevance in regenerative biology. For example, cells of the skeletal muscle, peripheral nerve and vasculature have specific oriented architectures that emerge from unique structure-function relationships. Methods that can induce similar cell morphologiesin vitrocan be of use in the development of biomimetic constructs for the repair or replacement of damaged tissues. In this work, we demonstrate that direct current (DC) electric fields (EFs) can be used as a tool to globally align cell populationsin vitro. Approach.Using a 2D culture chamber system, we were able to quickly (within hours) align Schwann cells at different culture densities with an application of steady EFs at 200-500 mV mm^-1.Main results.Cellular alignment was perpendicular to the field vector and varied proportionately as a function of field magnitude. In addition, the degree of cellular alignment was also dependent on cellular density. Even well-established Schwann cell monolayers were responsive to the applied DC fields with cells retracting parallel oriented processes (with respect to the imposed field) and re-extending them along the perpendicular axis. When the DC field was removed, monolayers retained the aligned morphology for many days afterwards, likely due to contact inhibition. We further show the method is applicable to other field-responsive cells, such as 3T3 fibroblasts.Significance.The patterned cells provided nanoscale haptotactic cues and can be subsequently used as a basal layer for co-culturing or manipulated for other applications. DC fields represent a rapid, simple, and efficient technique compared to other cell patterning methods such as substrate manipulation.

Stimuli-responsive biomaterials for cardiac tissue engineering and dynamic mechanobiology

Since the term "smart materials" was put forward in the 1980s, stimuli-responsive biomaterials have been used as powerful tools in tissue engineering, mechanobiology, and clinical applications. For the purpose of myocardial repair and regeneration, stimuli-responsive biomaterials are employed to fabricate hydrogels and nanoparticles for targeted delivery of therapeutic drugs and cells, which have been proved to alleviate disease progression and enhance tissue regeneration. By reproducing the sophisticated and dynamic microenvironment of the native heart, stimuli-responsive biomaterials have also been used to engineer dynamic culture systems to understand how cardiac cells and tissues respond to progressive changes in extracellular microenvironments, enabling the investigation of dynamic cell mechanobiology. Here, we provide an overview of stimuli-responsive biomaterials used in cardiovascular research applications, with a specific focus on cardiac tissue engineering and dynamic cell mechanobiology. We also discuss how these smart materials can be utilized to mimic the dynamic microenvironment during heart development, which might provide an opportunity to reveal the fundamental mechanisms of cardiomyogenesis and cardiac maturation.

Review Insights In Cardiac Tissue Engineering: Cells, Scaffolds, and Pharmacological Agents

Heart failure (HF) is one of the most important cardiovascular diseases (CVD), causing many die every year. Cardiac tissue engineering is a multidisciplinary field for creating functional tissues to improve the cardiac function of the damaged heart and get hope for end-stage patients. Recent works have focused on creating engineered cardiac tissue ex-vivo. Simultaneously, new approaches are used to study ways of induction of regeneration in the damaged heart after injury. The heart as a complex physiological pump consists of many cells such as cardiomyocytes (80–90% of the heart volume). These cardiomyocytes are elongated, aligned, and have beating properties. To create the heart muscle, which should be functional, soft and elastic scaffolds are required to resemble the native heart tissue. These mechanical characteristics are not compatible with all materials and should be well selected. Some scaffolds promote the viability and differentiation of stem cells. Each material has advantages and disadvantages with relevant influence behavior for cells. In this review, we present an overview of the general approaches developed to generate functional cardiac tissues, discussing the different cell sources, biomaterials, pharmacological agents, and engineering strategies in this manner. Moreover, we discuss the main challenges in cardiac tissue engineering that cause difficulties to construct heart muscle. We trust that researchers interested in developing cardiac tissue engineering will find the information reviewed here useful. Furthermore, we think that providing a unified framework will further the development of human engineered cardiac tissue constructs.

Electrically stimulable indium tin oxide plate for long-term in vitro cardiomyocyte culture

Background

We investigated whether electrical stimulation via indium tin oxide (ITO) could enhance the in vitro culture of neonatal rat ventricular myocytes (NRVMs), which are important in vitro models for studying the mechanisms underlying many aspects of cardiology.

Methods

Cardiomyocytes were obtained from 1-day-old neonatal rat heart ventricles. To evaluate function of NRVMs cultured on ITO with electrical stimulation, the cell viability, change of cell morphology, immunochemistry using cardiac-specific antibodies, and gene expression were tested.

Results

Defined sarcomeric structure, cell enlargement, and increased distribution of NRVMs appeared in the presence of electrical stimulation. These characteristics were absent in NRVMs cultured under standard culture conditions. In addition, the expression levels of cardiomyocyte-specific and ion channel markers were higher in NRVMs seeded on ITO-coated dishes than in the control group at 14 days after seeding. ITO-coated dishes could effectively provide electrical cues to support the in vitro culture of NRVMs.

Conclusions

These results provide supporting evidence that electrical stimulation via ITO can be effectively used to maintain culture and enhance function of cardiomyocytes in vitro.

Electrical Stimulation of pediatric cardiac-derived c-kit+ progenitor cells improves retention and cardiac function in right ventricular heart failure

Nearly 1 in every 120 children born has a congenital heart defect. Although surgical therapy has improved survival, many of these children go on to develop right ventricular heart failure (RVHF). The emergence of cardiovascular regenerative medicine as a potential therapeutic strategy for pediatric HF has provided new avenues for treatment with a focus on repairing or regenerating the diseased myocardium to restore cardiac function. Although primarily tried using adult cells and adult disease models, stem cell therapy is relatively untested in the pediatric population. Here, we investigate the ability of electrical stimulation (ES) to enhance the retention and therapeutic function of pediatric cardiac-derived c-kit+ progenitor cells (CPCs) in an animal model of RVHF. Human CPCs isolated from pediatric patients were exposed to chronic ES and implanted into the RV myocardium of rats. Cardiac function and cellular retention analysis showed electrically stimulated CPCs (ES-CPCs) were retained in the heart at a significantly higher level and longer time than control CPCs and also significantly improved right ventricular functional parameters. ES also induced upregulation of extracellular matrix and adhesion genes and increased in vitro survival and adhesion of cells. Specifically, upregulation of β1 and β5 integrins contributed to the increased retention of ES-CPCs. Lastly, we show that ES induces CPCs to release higher levels of pro-reparative factors in vitro. These findings suggest that ES can be used to increase the retention, survival, and therapeutic effect of human c-kit+ progenitor cells and can have implications on a variety of cell-based therapies. Stem Cells 2019;37:1528-1541.

A microfluidic device for noninvasive cell electrical stimulation and extracellular field potential analysis

We developed a device that can quickly apply versatile electrical stimulation (ES) signals to cells suspended in microfluidic channels and measure extracellular field potential simultaneously. The device could trap cells onto the surface of measurement electrodes for ES and push them to the downstream channel after ES by increasing pressure for continuous measurement. Cardiomyocytes, major functional cells in heart, together with human fibroblast cells and human umbilical vein endothelial cells, were tested with the device. Extracellular field potential signals generated from the cells were recorded. We found that under electrical stimulation, cardiomyocytes were triggered to alter their field potential, while non-excitable cells were not triggered. Hence this device can noninvasively distinguish electrically excitable cells from electrically non-excitable cells. Results have also shown that increased cardiomyocyte cell number led to increased magnitude and occurrence of the cell responses. This relationship could be used to detect the viable cells in a cardiac tissue. Application of variable ES signals on different cardiomyocyte clusters has shown that the application of ES clearly boosted cardiomyocytes electrical activities according to the stimulation frequency. In addition, we confirmed that the device can apply ES onto and detect the electrical responses from a mixed cell cluster; the responses from the mixed cluster is dependent on the ratio of cardiomyocytes. These results demonstrated that our device could be used as a tool to optimize ES conditions to facilitate the functional engineered cardiac tissue development.

Electrical Stimulation Enhances Cardiac Differentiation of Human Induced Pluripotent Stem Cells for Myocardial Infarction Therapy

AIMS

Electrical stimulation (EleS) can promote cardiac differentiation, but the underlying mechanism is not well known. This study investigated the effect of EleS on cardiomyocyte (CM) differentiation of human induced pluripotent stem cells (hiPSCs) and evaluated the therapeutic effects for the treatment of myocardial infarction (MI).

RESULTS

Cardiac differentiation of hiPSCs was induced with EleS after embryoid body formation. Spontaneously beating hiPSCs were observed as early at 2 days when treated with EleS compared with control treatment. The cardiac differentiation efficiency of hiPSCs was significantly enhanced by EleS. In addition, the functional maturation of hiPSC-CMs under EleS was confirmed by calcium indicators, intracellular Ca²⁺ levels, and expression of structural genes. Mechanistically, EleS mediated cardiac differentiation of hiPSCs through activation of Ca²⁺/PKC/ERK pathways, as revealed by RNA sequencing, quantitative polymerase chain reaction, and Western blotting. After transplantation in immunodeficient MI mice, EleS-preconditioned hiPSC-derived cells significantly improved cardiac function and attenuated expansion of infarct size. The preconditioned hiPSC-derived CMs were functionally integrated with the host heart.

INNOVATION

We show EleS as an efficacious time-saving approach for CM generation. The global RNA profiling shows that EleS can accelerate cardiac differentiation of hiPSCs through activation of multiple pathways. The cardiac-mimetic electrical signals will provide a novel approach to generate functional CMs and facilitate cardiac tissue engineering for successful heart regeneration.

CONCLUSION

EleS can enhance efficiency of cardiac differentiation in hiPSCs and promote CM maturation. The EleS-preconditioned CMs emerge as a promising approach for clinical application in MI treatment. Antioxid. Redox Signal. 28, 371-384.

Mesenchymal stem cells for cardiac repair: are the actors ready for the clinical scenario?

For years, sufficient progress has been made in treating heart failure following myocardial infarction; however, the social and economic burdens and the costs to world health systems remain high. Moreover, treatment advances have not resolved the underlying problem of functional heart tissue loss. In this field of research, for years we have actively explored innovative biotherapies for cardiac repair. Here, we present a general, critical overview of our experience in using mesenchymal stem cells, derived from cardiac adipose tissue and umbilical cord blood, in a variety of cell therapy and tissue engineering approaches. We also include the latest advances and future challenges, including good manufacturing practice and regulatory issues. Finally, we evaluate whether recent approaches hold potential for reliable translation to clinical trials.

Electrically Induced Calcium Handling in Cardiac Progenitor Cells

For nearly a century, the heart was viewed as a terminally differentiated organ until the discovery of a resident population of cardiac stem cells known as cardiac progenitor cells (CPCs). It has been shown that the regenerative capacity of CPCs can be enhanced by ex vivo modification. Preconditioning CPCs could provide drastic improvements in cardiac structure and function; however, a systematic approach to determining a mechanistic basis for these modifications founded on the physiology of CPCs is lacking. We have identified a novel property of CPCs to respond to electrical stimulation by initiating intracellular Ca²⁺ oscillations. We used confocal microscopy and intracellular calcium imaging to determine the spatiotemporal properties of the Ca²⁺ signal and the key proteins involved in this process using pharmacological inhibition and confocal Ca²⁺ imaging. Our results provide valuable insights into mechanisms to enhance the therapeutic potential in stem cells and further our understanding of human CPC physiology.

Electromechanical Conditioning of Adult Progenitor Cells Improves Recovery of Cardiac Function After Myocardial Infarction

Cardiac cells are subjected to mechanical and electrical forces, which regulate gene expression and cellular function. Therefore, in vitro electromechanical stimuli could benefit further integration of therapeutic cells into the myocardium. Our goals were (a) to study the viability of a tissue-engineered construct with cardiac adipose tissue-derived progenitor cells (cardiac ATDPCs) and (b) to examine the effect of electromechanically stimulated cardiac ATDPCs within a myocardial infarction (MI) model in mice for the first time. Cardiac ATDPCs were electromechanically stimulated at 2-millisecond pulses of 50 mV/cm at 1 Hz and 10% stretching during 7 days. The cells were harvested, labeled, embedded in a fibrin hydrogel, and implanted over the infarcted area of the murine heart. A total of 39 animals were randomly distributed and sacrificed at 21 days: groups of grafts without cells and with stimulated or nonstimulated cells. Echocardiography and gene and protein analyses were also carried out. Physiologically stimulated ATDPCs showed increased expression of cardiac transcription factors, structural genes, and calcium handling genes. At 21 days after implantation, cardiac function (measured as left ventricle ejection fraction between presacrifice and post-MI) increased up to 12% in stimulated grafts relative to nontreated animals. Vascularization and integration with the host blood supply of grafts with stimulated cells resulted in increased vessel density in the infarct border region. Trained cells within the implanted fibrin patch expressed main cardiac markers and migrated into the underlying ischemic myocardium. To conclude, synchronous electromechanical cell conditioning before delivery may be a preferred alternative when considering strategies for heart repair after myocardial infarction. Stem Cells Translational Medicine 2017;6:970-981.

Modulation of cell function by electric field: a high-resolution analysis

Regulation of cell function by a non-thermal, physiological-level electromagnetic field has potential for vascular tissue healing therapies and advancing hybrid bioelectronic technology. We have recently demonstrated that a physiological electric field (EF) applied wirelessly can regulate intracellular signalling and cell function in a frequency-dependent manner. However, the mechanism for such regulation is not well understood. Here, we present a systematic numerical study of a cell-field interaction following cell exposure to the external EF. We use a realistic experimental environment that also recapitulates the absence of a direct electric contact between the field-sourcing electrodes and the cells or the culture medium. We identify characteristic regimes and present their classification with respect to frequency, location, and the electrical properties of the model components. The results show a striking difference in the frequency dependence of EF penetration and cell response between cells suspended in an electrolyte and cells attached to a substrate. The EF structure in the cell is strongly inhomogeneous and is sensitive to the physical properties of the cell and its environment. These findings provide insight into the mechanisms for frequency-dependent cell responses to EF that regulate cell function, which may have important implications for EF-based therapies and biotechnology development.

Electrical stimulation to optimize cardioprotective exosomes from cardiac stem cells

Injured or ischemic cardiac tissue has limited intrinsic capacity for regeneration. While stem cell transplantation is a promising approach to stimulating cardiac repair, its success in humans has thus far been limited. Harnessing the therapeutic benefits of stem cells requires a better understanding of their mechanisms of action and methods to optimize their function. Cardiac stem cells (CSC) represent a particularly effective cellular source for cardiac repair, and pre-conditioning CSC with electrical stimulation (EleS) was demonstrated to further enhance their function, although the mechanisms are unknown. Recent studies suggest that transplanted stem cells primarily exert their effects through communicating with endogenous tissues via the release of exosomes containing cardioprotective molecules such as miRNAs, which upon uptake by recipient cells may stimulate survival, proliferation, and angiogenesis. Exosomes are also effective therapeutic agents in isolation and may provide a feasible alternative to stem cell transplantation. We hypothesize that EleS enhances CSC-mediated cardiac repair through its beneficial effects on production of cardioprotective exosomes. Moreover, we hypothesize that the beneficial effects of biventricular pacing in patients with heart failure may in part result from EleS-induced preconditioning of endogenous CSC to promote cardiac repair. With future research, our hypothesis may provide applications to optimize stem cell therapy and augment current pacing protocols, which may significantly advance the treatment of patients with heart disease.

Silver-zinc redox-coupled electroceutical wound dressing disrupts bacterial biofilm

Pseudomonas aeruginosa biofilm is commonly associated with chronic wound infection. A FDA approved wireless electroceutical dressing (WED), which in the presence of conductive wound exudate gets activated to generate electric field (0.3–0.9V), was investigated for its anti-biofilm properties. Growth of pathogenic P. aeruginosa strain PAO1 in LB media was markedly arrested in the presence of the WED. Scanning electron microscopy demonstrated that WED markedly disrupted biofilm integrity in a setting where silver dressing was ineffective. Biofilm thickness and number of live bacterial cells were decreased in the presence of WED. Quorum sensing genes lasR and rhlR and activity of electric field sensitive enzyme, glycerol-3-phosphate dehydrogenase was also repressed by WED. This work provides first electron paramagnetic resonance spectroscopy evidence demonstrating that WED serves as a spontaneous source of reactive oxygen species. Redox-sensitive multidrug efflux systems mexAB and mexEF were repressed by WED. Taken together, these observations provide first evidence supporting the anti-biofilm properties of WED.