Differentiation, Metabolism, and Cardioprotective Secretory Functions of Human Cardiac Stromal Cells from Ischemic and Endocarditis Patients

This study investigates the characteristics of cardiac mesenchymal stem cell-like cells (CMSCLCs) isolated from the right atrial appendage of human donors with ischemia and a young patient with endocarditis (NE-CMSCLCs). Typical CMSCLCs from ischemic heart patients were derived from coronary artery bypass grafting procedures and compared against bone marrow mesenchymal stromal cells (BM-MSCs). NE-CMSCLCs had a normal immunophenotype, but exhibited enhanced osteogenic differentiation potential, rapid proliferation, reduced senescence, reduced glycolysis, and lower reactive oxygen species generation after oxidative stress compared with typical ischemic CMSCLCs. These differences suggest a unique functional status of NE-CMSCLCs, influenced by the donor health condition. Despite large variances in their paracrine secretome, NE-CMSCLCs retained therapeutic potential, as indicated by their ability to protect hypoxia/reoxygenation-injured human cardiomyocytes, albeit less effectively than typical CMSCLCs. This research describes a unique cell phenotype and underscores the importance of donor health status in the therapeutic efficacy of autologous cardiac cell therapy.

Long-term engraftment and maturation of autologous iPSC-derived cardiomyocytes in two rhesus macaques

Cellular therapies with cardiomyocytes produced from induced pluripotent stem cells (iPSC-CMs) offer a potential route to cardiac regeneration as a treatment for chronic ischemic heart disease. Here, we report successful long-term engraftment and in vivo maturation of autologous iPSC-CMs in two rhesus macaques with small, subclinical chronic myocardial infarctions, all without immunosuppression. Longitudinal positron emission tomography imaging using the sodium/iodide symporter (NIS) reporter gene revealed stable grafts for over 6 and 12 months, with no teratoma formation. Histological analyses suggested capability of the transplanted iPSC-CMs to mature and integrate with endogenous myocardium, with no sign of immune cell infiltration or rejection. By contrast, allogeneic iPSC-CMs were rejected within 8 weeks of transplantation. This study provides the longest-term safety and maturation data to date in any large animal model, addresses concerns regarding neoantigen immunoreactivity of autologous iPSC therapies, and suggests that autologous iPSC-CMs would similarly engraft and mature in human hearts.

Advanced Cardiac Patches for the Treatment of Myocardial Infarction

Myocardial infarction is a cardiovascular disease characterized by a high incidence rate and mortality. It leads to various cardiac pathophysiological changes, including ischemia/reperfusion injury, inflammation, fibrosis, and ventricular remodeling, which ultimately result in heart failure and pose a significant threat to global health. Although clinical reperfusion therapies and conventional pharmacological interventions improve emergency survival rates and short-term prognoses, they are still limited in providing long-lasting improvements in cardiac function or reversing pathological progression. Recently, cardiac patches have gained considerable attention as a promising therapy for myocardial infarction. These patches consist of scaffolds or loaded therapeutic agents that provide mechanical reinforcement, synchronous electrical conduction, and localized delivery within the infarct zone to promote cardiac restoration. This review elucidates the pathophysiological progression from myocardial infarction to heart failure, highlighting therapeutic targets and various cardiac patches. The review considers the primary scaffold materials, including synthetic, natural, and conductive materials, and the prevalent fabrication techniques and optimal properties of the patch, as well as advanced delivery strategies. Last, the current limitations and prospects of cardiac patch research are considered, with the goal of shedding light on innovative products poised for clinical application.

Addressing Cardiovascular Toxicity Risk of Electronic Nicotine Delivery Systems in the Twenty-First Century: "What Are the Tools Needed for the Job?" and "Do We Have Them?"

Cigarette smoking is positively and robustly associated with cardiovascular disease (CVD), including hypertension, atherosclerosis, cardiac arrhythmias, stroke, thromboembolism, myocardial infarctions, and heart failure. However, after more than a decade of ENDS presence in the U.S. marketplace, uncertainty persists regarding the long-term health consequences of ENDS use for CVD. New approach methods (NAMs) in the field of toxicology are being developed to enhance rapid prediction of human health hazards. Recent technical advances can now consider impact of biological factors such as sex and race/ethnicity, permitting application of NAMs findings to health equity and environmental justice issues. This has been the case for hazard assessments of drugs and environmental chemicals in areas such as cardiovascular, respiratory, and developmental toxicity. Despite these advances, a shortage of widely accepted methodologies to predict the impact of ENDS use on human health slows the application of regulatory oversight and the protection of public health. Minimizing the time between the emergence of risk (e.g., ENDS use) and the administration of well-founded regulatory policy requires thoughtful consideration of the currently available sources of data, their applicability to the prediction of health outcomes, and whether these available data streams are enough to support an actionable decision. This challenge forms the basis of this white paper on how best to reveal potential toxicities of ENDS use in the human cardiovascular system-a primary target of conventional tobacco smoking. We identify current approaches used to evaluate the impacts of tobacco on cardiovascular health, in particular emerging techniques that replace, reduce, and refine slower and more costly animal models with NAMs platforms that can be applied to tobacco regulatory science. The limitations of these emerging platforms are addressed, and systems biology approaches to close the knowledge gap between traditional models and NAMs are proposed. It is hoped that these suggestions and their adoption within the greater scientific community will result in fresh data streams that will support and enhance the scientific evaluation and subsequent decision-making of tobacco regulatory agencies worldwide.

Standardisation is the key to the sustained, rapid and healthy development of stem cell-based therapy

BACKGROUND

Stem cell-based therapy (SCT) is an important component of regenerative therapy that brings hope to many patients. After decades of development, SCT has made significant progress in the research of various diseases, and the market size has also expanded significantly. The transition of SCT from small-scale, customized experiments to routine clinical practice requires the assistance of standards. Many countries and international organizations around the world have developed corresponding SCT standards, which have effectively promoted the further development of the SCT industry.

METHODS

We conducted a comprehensive literature review to introduce the clinical application progress of SCT and focus on the development status of SCT standardization.

RESULTS

We first briefly introduced the types and characteristics of stem cells, and summarized the current clinical application and market development of SCT. Subsequently, we focused on the development status of SCT-related standards as of now from three levels: the International Organization for Standardization (ISO), important international organizations, and national organizations. Finally, we provided perspectives and conclusions on the significance and challenges of SCT standardization.

CONCLUSIONS

Standardization plays an important role in the sustained, rapid and healthy development of SCT.

Stem cell therapy for cardiac regeneration: past, present, and future

Cardiac disorders remain the leading cause of mortality worldwide. Current clinical strategies, including drug therapy, surgical interventions, and organ transplantation offer limited benefits to patients without regenerating the damaged myocardium. Over the past decade, stem cell therapy has generated a keen interest owing to its unique self-renewal and immune privileged characteristics. Furthermore, the ability of stem cells to differentiate into specialized cell types, has made them a popular therapeutic tool against various diseases. This comprehensive review provides an overview of therapeutic potential of different types of stem cells in reference to cardiovascular diseases. Furthermore, it sheds light on the advantages and limitations associated with each cell type. An in-depth analysis of the challenges associated with stem cell research and the hurdles for its clinical translation and their possible solutions have also been elaborated upon. It examines the controversies surrounding embryonic stem cells and the emergence of alternative approaches, such as the use of induced pluripotent stem cells for cardiac therapeutic applications. Overall, this review serves as a valuable resource for researchers, clinicians, and policymakers involved in the field of regenerative medicine, guiding the development of safe and effective stem cell-based therapies to revolutionize patient care.

Pluripotent stem cell-based cardiac regenerative therapy for heart failure

Cardiac regenerative therapy using human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) is expected to become an alternative to heart transplantation for severe heart failure. It is now possible to produce large numbers of human pluripotent stem cells (hPSCs) and eliminate non-cardiomyocytes, including residual undifferentiated hPSCs, which can cause teratoma formation after transplantation. There are two main strategies for transplanting hPSC-CMs: injection of hPSC-CMs into the myocardium from the epicardial side, and implantation of hPSC-CM patches or engineered heart tissues onto the epicardium. Transplantation of hPSC-CMs into the myocardium of large animals in a myocardial infarction model improved cardiac function. The engrafted hPSC-CMs matured, and microvessels derived from the host entered the graft abundantly. Furthermore, as less invasive methods using catheters, injection into the coronary artery and injection into the myocardium from the endocardium side have recently been investigated. Since transplantation of hPSC-CMs alone has a low engraftment rate, various methods such as transplantation with the extracellular matrix or non-cardiomyocytes and aggregation of hPSC-CMs have been developed. Post-transplant arrhythmias, imaging of engrafted hPSC-CMs, and immune rejection are the remaining major issues, and research is being conducted to address them. The clinical application of cardiac regenerative therapy using hPSC-CMs has just begun and is expected to spread widely if its safety and efficacy are proven in the near future.

Principle and design of clinical efficacy observation of extracorporeal cardiac shock wave therapy for patients with myocardial ischemia-reperfusion injury: A prospective randomized controlled trial protocol

BACKGROUND

Acute ST-segment elevation myocardial infarction (STEMI) remains a serious life threatening event with a poor prognosis due to myocardial ischemia/reperfusion injury despite coronary revascularization. Extracorporeal cardiac shock wave (ECSW) is a safe, effective and non-invasive new method for the treatment of cardiovascular diseases. The current results show that extracorporeal cardiac shock wave provides a new treatment option for patients with severe and advanced coronary heart disease. However, there are relatively few clinical studies on the application of in vitro cardiac shock waves in patients with myocardial ischemia-reperfusion injury. We hypothesized that extracorporeal cardiac shock therapy would also be effective in reducing clinical endpoints in patients with STEMI reperfusion.

OBJECTIVE

This study is order to provide a new therapeutic method for patients with myocardial ischemia-reperfusion injury and reveal the possible mechanism of ECSW for ischemia-reperfusion injury.

METHODS AND MATERIALS

CEECSWIIRI is a single-center, prospective randomized controlled trial that plans to enroll 102 eligible patients with acute ST-segment elevation myocardial infarction reperfusion. Eligible patients with STEMI reperfusion will be randomly divided into external cardiac shock therapy (ECSW) trial group and blank control group. The blank control group will receive optimal drug therapy, and the experimental group will receive optimal drug therapy combined with ECSW. The shock wave treatment plan will be 3-month therapy, specifically 1 week of treatment per month, 3 weeks of rest, 3 times of ECSW in each treatment week, respectively on the first day, the third day and the fifth day of the treatment week, lasting for 3 months and follow-up for 2 years. The primary endpoint will be to assess the 2-year improvement in all-cause death, re-hospitalization due to cardiovascular disease, major unintentional cerebrovascular events, including cardiogenic death, myocardial infarction, heart failure, arrhythmia, emergency coronary revascularization, and stroke in patients with STEMI reperfusion. Secondary endpoints will include improvements in angina pectoris, quality of life, cardiac structure and function, coronary microcirculation, and endothelial progenitor cell-derived miR-140-3p in relation to survival outcomes.

TRIAL REGISTRATION NUMBER

ClinicalTrial.gov.org PRS:NCT05624203; Date of registration: November 12, 2022.

hESC-Derived Epicardial Cells Promote Repair of Infarcted Hearts in Mouse and Swine

Myocardial infarction (MI) causes excessive damage to the myocardium, including the epicardium. However, whether pluripotent stem cell-derived epicardial cells (EPs) can be a therapeutic approach for infarcted hearts remains unclear. Here, the authors report that intramyocardial injection of human embryonic stem cell-derived EPs (hEPs) at the acute phase of MI ameliorates functional worsening and scar formation in mouse hearts, concomitantly with enhanced cardiomyocyte survival, angiogenesis, and lymphangiogenesis. Mechanistically, hEPs suppress MI-induced infiltration and cytokine-release of inflammatory cells and promote reparative macrophage polarization. These effects are blocked by a type I interferon (IFN-I) receptor agonist RO8191. Moreover, intelectin 1 (ITLN1), abundantly secreted by hEPs, interacts with IFN-β and mimics the effects of hEP-conditioned medium in suppression of IFN-β-stimulated responses in macrophages and promotion of reparative macrophage polarization, whereas ITLN1 downregulation in hEPs cancels beneficial effects of hEPs in anti-inflammation, IFN-I response inhibition, and cardiac repair. Further, similar beneficial effects of hEPs are observed in a clinically relevant porcine model of reperfused MI, with no increases in the risk of hepatic, renal, and cardiac toxicity. Collectively, this study reveals hEPs as an inflammatory modulator in promoting infarct healing via a paracrine mechanism and provides a new therapeutic approach for infarcted hearts.

Stem cells derived exosomes and biomaterials to modulate autophagy and mend broken hearts

Autophagy maintains cellular homeostasis and plays a crucial role in managing pathological conditions including ischemic myocardial injury leading to heart failure (HF). Despite treatments, no intervention can replace lost cardiomyocytes. Stem cell therapy offers potential for post-myocardial infarction repair but struggles with poor cell retention due to immune rejection. In the search for effective therapies, stem cell-derived extracellular vesicles (EVs), especially exosomes, have emerged as promising tools. These tiny bioactive molecule carriers play vital roles in intercellular communication and tissue engineering. They offer numerous therapeutic benefits including modulating immune responses, promoting tissue repair, and boosting angiogenesis. Additionally, biomaterials provide a conducive 3D microenvironment for cell, exosome, and biomolecule delivery, and enhance heart muscle strength, making it a comprehensive cardiac repair strategy. In this regard, the current review delves into the intricate application of extracellular vesicles (EVs) and biomaterials for managing autophagy in the heart muscle during cardiac injury. Central to our investigation is the exploration of how these elements interact within the context of cardiac repair and regeneration. Additionally, this review also casts light on the formidable challenges that plague this field, such as the issues of safety, efficacy, controlled delivery, and acceptance of these therapeutic strategies for effective clinical translation. Addressing these challenges is crucial for unlocking the full therapeutic potential of EV and biomaterial-based therapies and ensuring their successful translation from bench to bedside.

Cellular reprogramming of fibroblasts in heart regeneration

Myocardial infarction causes the loss of cardiomyocytes and the formation of cardiac fibrosis due to the activation of cardiac fibroblasts, leading to cardiac dysfunction and heart failure. Unfortunately, current therapeutic interventions can only slow the disease progression. Furthermore, they cannot fully restore cardiac function, likely because the adult human heart lacks sufficient capacity to regenerate cardiomyocytes. Therefore, intensive efforts have focused on developing therapeutics to regenerate the damaged heart. Several strategies have been intensively investigated, including stimulation of cardiomyocyte proliferation, transplantation of stem cell-derived cardiomyocytes, and conversion of fibroblasts into cardiac cells. Resident cardiac fibroblasts are critical in the maintenance of the structure and contractility of the heart. Fibroblast plasticity makes this type of cells be reprogrammed into many cell types, including but not limited to induced pluripotent stem cells, induced cardiac progenitor cells, and induced cardiomyocytes. Fibroblasts have become a therapeutic target due to their critical roles in cardiac pathogenesis. This review summarizes the reprogramming of fibroblasts into induced pluripotent stem cell-derived cardiomyocytes, induced cardiac progenitor cells, and induced cardiomyocytes to repair a damaged heart, outlines recent findings in utilizing fibroblast-derived cells for heart regeneration, and discusses the limitations and challenges.

Pluripotent stem cell-derived committed cardiac progenitors remuscularize damaged ischemic hearts and improve their function in pigs

Ischemic heart disease, which is often associated with irreversibly damaged heart muscle, is a major global health burden. Here, we report the potential of stem cell-derived committed cardiac progenitors (CCPs) have in regenerative cardiology. Human pluripotent embryonic stem cells were differentiated to CCPs on a laminin 521 + 221 matrix, characterized with bulk and single-cell RNA sequencing, and transplanted into infarcted pig hearts. CCPs differentiated for eleven days expressed a set of genes showing higher expression than cells differentiated for seven days. Functional heart studies revealed significant improvement in left ventricular ejection fraction at four and twelve weeks following transplantation. We also observed significant improvements in ventricular wall thickness and a reduction in infarction size after CCP transplantation (p-value < 0.05). Immunohistology analyses revealed in vivo maturation of the CCPs into cardiomyocytes (CM). We observed temporary episodes of ventricular tachyarrhythmia (VT) in four pigs and persistent VT in one pig, but the remaining five pigs exhibited normal sinus rhythm. Importantly, all pigs survived without the formation of any tumors or VT-related abnormalities. We conclude that pluripotent stem cell-derived CCPs constitute a promising possibility for myocardial infarction treatment and that they may positively impact regenerative cardiology.

Cells and Materials for Cardiac Repair and Regeneration

After more than 20 years following the introduction of regenerative medicine to address the problem of cardiac diseases, still questions arise as to the best cell types and materials to use to obtain effective clinical translation. Now that it is definitively clear that the heart does not have a consistent reservoir of stem cells that could give rise to new myocytes, and that there are cells that could contribute, at most, with their pro-angiogenic or immunomodulatory potential, there is fierce debate on what will emerge as the winning strategy. In this regard, new developments in somatic cells' reprogramming, material science and cell biophysics may be of help, not only for protecting the heart from the deleterious consequences of aging, ischemia and metabolic disorders, but also to boost an endogenous regeneration potential that seems to be lost in the adulthood of the human heart.

Protection of cell therapeutics from antibody-mediated killing by CD64 overexpression

Allogeneic cell therapeutics for cancer therapy or regenerative medicine are susceptible to antibody-mediated killing, which diminishes their efficacy. Here we report a strategy to protect cells from antibody-mediated killing that relies on engineered overexpression of the IgG receptor CD64. We show that human and mouse iPSC-derived endothelial cells (iECs) overexpressing CD64 escape antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity from IgG antibodies in vitro and in ADCC-enabled mice. When CD64 expression was combined with hypoimmune genetic modifications known to protect against cellular immunity, B2M-/-CIITA-/- CD47/CD64-transgenic iECs were resistant to both IgG antibody-mediated and cellular immune killing in vitro and in humanized mice. Mechanistic studies demonstrated that CD64 or its intracellularly truncated analog CD64t effectively capture monomeric IgG and occupy their Fc, and the IgG bind and occupy their target antigens. In three applications of the approach, human CD64t-engineered thyroid epithelial cells, pancreatic beta cells and CAR T cells withstood clinically relevant levels of graft-directed antibodies and fully evaded antibody-mediated killing.

Leaf-venation-directed cellular alignment for macroscale cardiac constructs with tissue-like functionalities

Recapitulating the complex structural, mechanical, and electrophysiological properties of native myocardium is crucial to engineering functional cardiac tissues. Here, we report a leaf-venation-directed strategy that enables the compaction and remodeling of cell-hydrogel hybrids into highly aligned and densely packed organizations in predetermined patterns. This strategy contributes to interconnected tubular structures with cell alignment along the hierarchical channels. Compared to randomly-distributed cells, the engineered leaf-venation-directed-cardiac tissues from neonatal rat cardiomyocytes manifest advanced maturation and functionality as evidenced by detectable electrophysiological activity, macroscopically synchronous contractions, and upregulated maturation genes. As a demonstration, human induced pluripotent stem cell-derived leaf-venation-directed-cardiac tissues are engineered with evident structural and functional improvement over time. With the elastic scaffolds, leaf-venation-directed tissues are assembled into 3D centimeter-scale cardiac constructs with programmed mechanical properties, which can be delivered through tubing without affecting cell viability. The present strategy may generate cardiac constructs with multifaceted functionalities to meet clinical demands.

RIPK necrotic cell death pathway in both donor photoreceptor and host immune cells synergize to affect photoreceptor graft survival

Photoreceptor transplant has been put forward as a repair strategy to tackle degenerated retinas. Nonetheless, cell death and immune rejection seriously limit the success of this strategy, with only a small fraction of transplanted cells surviving. Improving the survival of transplanted cells is of critical importance. Recent evidence has identified receptor-interacting protein kinase 3 (RIPK3) as a molecular trigger controlling necroptotic cell death and inflammation. However, its role in photoreceptor transplantation and regenerative medicine has not been studied. We hypothesized that modulation of RIPK3 to address both cell death and immunity could have advantageous effects on photoreceptor survival. In a model of inherited retinal degeneration, deletion of RIPK3 in donor photoreceptor precursors significantly increases the survival of transplanted cells. Simultaneous RIPK3 deletion in donor photoreceptors and recipients maximizes graft survival. Lastly, to discern the role of RIPK3 in the host immune response, bone marrow transplant experiments demonstrated that peripheral immune cell RIPK3 deficiency is protective for both donor and host photoreceptor survival. Interestingly, this finding is independent of photoreceptor transplantation, as the peripheral protective effect is also observed in an additional retinal detachment photoreceptor degeneration model. Altogether, these results indicate that immunomodulatory and neuroprotective strategies targeting the RIPK3 pathway can aid regenerative therapies of photoreceptor transplantation.

Identification of SALL4 Expressing Islet-1+ Cardiovascular Progenitor Cell Clones

The utilization of cardiac progenitor cells (CPCs) has been shown to induce favorable regenerative effects. While there are various populations of endogenous CPCs in the heart, there is no consensus regarding which population is ideal for cell-based regenerative therapy. Early-stage progenitor cells can be differentiated into all cardiovascular lineages, including cardiomyocytes and endothelial cells. Identifying an Islet-1+ (Isl-1+) early-stage progenitor population with enhanced stemness, multipotency and differentiation potential would be beneficial for the development of novel regenerative therapies. Here, we investigated the transcriptome of human neonatal Isl-1+ CPCs. Isl-1+ human neonatal CPCs exhibit enhanced stemness properties and were found to express Spalt-like transcription factor 4 (SALL4). SALL4 plays a role in embryonic development as well as proliferation and expansion of hematopoietic progenitor cells. SALL4, SOX2, EpCAM and TBX5 are co-expressed in the majority of Isl-1+ clones isolated from neonatal patients. The pre-mesendodermal transcript TFAP2C was identified in select Isl-1, SALL4, SOX2, EpCAM and TBX5 expressing clones. The ability to isolate and expand pre-mesendodermal stage cells from human patients is a novel finding that holds potential value for applications in regenerative medicine.

Cardiac Transcription Regulators Differentiate Human Umbilical Cord Mesenchymal Stem Cells into Cardiac Cells

Stem cell-based therapy presents an attractive alternative to conventional therapies for degenerative diseases. Numerous studies have investigated the capability of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) to contribute to the regeneration of cardiomyocytes, and the results have encouraged further basic and clinical studies on the MSC-based treatment of cardiomyopathies. This study aimed to determine the potential of cardiomyogenic transcription factors in differentiating hUC-MSCs into cardiac-like cells in vitro. MSCs were isolated from umbilical cord tissue and were transduced with the transcription factor genes, GATA-4 and Nkx 2.5, via infection with lentiviruses, to promote differentiation into the cardiomyogenic lineage. Gene and protein expression were analysed with qPCR and immunocytochemical staining. After transduction, differentiated cardiac-like cells showed significant expression of cardiac genes and proteins, namely GATA-4, Nkx-2.5, cardiac troponin I (cTnI) and myosin heavy chain (MHC). The cardiomyogenic-induced group significantly overexpressed cardiac-specific genes (GATA-4, Nkx-2.5, cTnI, MHC, α-actinin and Wnt2). Expression of the calcium channel gene was also significantly increased, while the sodium channel gene was downregulated in the transduced hUC-MSCs, as compared to non-transduced cells. The results suggest that GATA-4 and Nkx-2.5 interact synergistically in the activation of downstream cardiac transcription factors, demonstrating the functional convergence of hUC-MSC differentiation into cardiac-like cells. These findings could potentially be utilised in the efficient production of cardiac-like cells from stem cells; these cardiac-like cells could then be used in various applications, such as for in vivo implantation in infarcted myocardium, and for drug screening in toxicity testing.

Intracoronary transplantation of pluripotent stem cell-derived cardiomyocytes: Inefficient procedure for cardiac regeneration

Advances in stem cell biology have facilitated cardiac regeneration, and many animal studies and several initial clinical trials have been conducted using human pluripotent stem cell-derived cardiomyocytes (PSC-CMs). Most preclinical and clinical studies have typically transplanted PSC-CMs via the following two distinct approaches: direct intramyocardial injection or epicardial delivery of engineered heart tissue. Both approaches present common disadvantages, including a mandatory thoracotomy and poor engraftment. Furthermore, a standard transplantation approach has yet to be established. In this study, we tested the feasibility of performing intracoronary administration of PSC-CMs based on a commonly used method of transplanting somatic stem cells. Six male cynomolgus monkeys underwent intracoronary administration of dispersed human PSC-CMs or PSC-CM aggregates, which are called cardiac spheroids, with multiple cell dosages. The recipient animals were sacrificed at 4 weeks post-transplantation for histological analysis. Intracoronary administration of dispersed human PSC-CMs in the cynomolgus monkeys did not lead to coronary embolism or graft survival. Although the transplanted cardiac spheroids became partially engrafted, they also induced scar formation due to cardiac ischemic injury. Cardiac engraftment and scar formation were reasonably consistent with the spheroid size or cell dosage. These findings indicate that intracoronary transplantation of PSC-CMs is an inefficient therapeutic approach.

Generation of expandable cardiovascular progenitor cells from mouse and human fibroblasts via direct chemical reprogramming

Here, we present a protocol to reprogram mouse and human fibroblasts into expandable cardiovascular progenitor cells (CPCs) via a defined small-molecule treatment. We describe steps to prepare fibroblasts and generate the chemically induced CPCs (ciCPCs), followed by expansion and differentiation of the ciCPCs. These cells can self-renew in the long term, faithfully retaining the CPC phenotype and cardiovascular differentiation capacity. This protocol provides an autologous and expandable cardiovascular cell source, which may find uses in cardiovascular disease modelling, drug discovery, and cardiac cell therapy. For complete details on the use and execution of this protocol, please refer to Wang et al. (2022).¹.

Artificial-Intelligence-Based Imaging Analysis of Stem Cells: A Systematic Scoping Review

This systematic scoping review aims to map and identify the available artificial-intelligence-based techniques for imaging analysis, the characterization of stem cell differentiation, and trans-differentiation pathways. On the ninth of March 2022, data were collected from five electronic databases (PubMed, Medline, Web of Science, Cochrane, and Scopus) and manual citation searching; all data were gathered in Zotero 5.0. A total of 4422 articles were collected after deduplication; only twenty-seven studies were included in this systematic scoping review after a two-phase screening against inclusion criteria by two independent reviewers. The amount of research in this field is significantly increasing over the years. While the current state of artificial intelligence (AI) can tackle a multitude of medical problems, the consensus amongst researchers remains that AI still falls short in multiple ways that investigators should examine, ranging from the quality of images used in training sets and appropriate sample size, as well as the unexpected events that may occur which the algorithm cannot predict.

Cell-Based and Selected Cell-Free Therapies for Myocardial Infarction: How Do They Compare to the Current Treatment Options?

Because of cardiomyocyte death or dysfunction frequently caused by myocardial infarction (MI), heart failure is a leading cause of morbidity and mortality in modern society. Paradoxically, only limited and non-curative therapies for heart failure or MI are currently available. As a result, over the past two decades research has focused on developing cell-based approaches promoting the regeneration of infarcted tissue. Cell-based therapies for myocardial regeneration include powerful candidates, such as multipotent stem cells (mesenchymal stem cells (MSCs), bone-marrow-derived stem cells, endothelial progenitor cells, and hematopoietic stem cells) and induced pluripotent stem cells (iPSCs). These possess unique properties, such as potency to differentiate into desired cell types, proliferation capacity, and patient specificity. Preclinical and clinical studies have demonstrated modest improvement in the myocardial regeneration and reduced infarcted areas upon transplantation of pluripotent or multipotent stem cells. Another cell population that need to be considered as a potential source for cardiac regeneration are telocytes found in different organs, including the heart. Their therapeutic effect has been studied in various heart pathologies, such as MI, arrhythmias, or atrial amyloidosis. The most recent cell-free therapeutic tool relies on the cardioprotective effect of complex cargo carried by small membrane-bound vesicles-exosomes-released from stem cells via exocytosis. The MSC/iPSC-derived exosomes could be considered a novel exosome-based therapy for cardiovascular diseases thanks to their unique content. There are also other cell-free approaches, e.g., gene therapy, or acellular cardiac patches. Therefore, our review provides the most recent insights into the novel strategies for myocardial repair based on the regenerative potential of different cell types and cell-free approaches.

Myocardial infarction from a tissue engineering and regenerative medicine point of view: A comprehensive review on models and treatments

In the modern world, myocardial infarction is one of the most common cardiovascular diseases, which are responsible for around 18 million deaths every year or almost 32% of all deaths. Due to the detrimental effects of COVID-19 on the cardiovascular system, this rate is expected to increase in the coming years. Although there has been some progress in myocardial infarction treatment, translating pre-clinical findings to the clinic remains a major challenge. One reason for this is the lack of reliable and human representative healthy and fibrotic cardiac tissue models that can be used to understand the fundamentals of ischemic/reperfusion injury caused by myocardial infarction and to test new drugs and therapeutic strategies. In this review, we first present an overview of the anatomy of the heart and the pathophysiology of myocardial infarction, and then discuss the recent developments on pre-clinical infarct models, focusing mainly on the engineered three-dimensional cardiac ischemic/reperfusion injury and fibrosis models developed using different engineering methods such as organoids, microfluidic devices, and bioprinted constructs. We also present the benefits and limitations of emerging and promising regenerative therapy treatments for myocardial infarction such as cell therapies, extracellular vesicles, and cardiac patches. This review aims to overview recent advances in three-dimensional engineered infarct models and current regenerative therapeutic options, which can be used as a guide for developing new models and treatment strategies.

Stem cell-based therapy for human diseases

Recent advancements in stem cell technology open a new door for patients suffering from diseases and disorders that have yet to be treated. Stem cell-based therapy, including human pluripotent stem cells (hPSCs) and multipotent mesenchymal stem cells (MSCs), has recently emerged as a key player in regenerative medicine. hPSCs are defined as self-renewable cell types conferring the ability to differentiate into various cellular phenotypes of the human body, including three germ layers. MSCs are multipotent progenitor cells possessing self-renewal ability (limited in vitro) and differentiation potential into mesenchymal lineages, according to the International Society for Cell and Gene Therapy (ISCT). This review provides an update on recent clinical applications using either hPSCs or MSCs derived from bone marrow (BM), adipose tissue (AT), or the umbilical cord (UC) for the treatment of human diseases, including neurological disorders, pulmonary dysfunctions, metabolic/endocrine-related diseases, reproductive disorders, skin burns, and cardiovascular conditions. Moreover, we discuss our own clinical trial experiences on targeted therapies using MSCs in a clinical setting, and we propose and discuss the MSC tissue origin concept and how MSC origin may contribute to the role of MSCs in downstream applications, with the ultimate objective of facilitating translational research in regenerative medicine into clinical applications. The mechanisms discussed here support the proposed hypothesis that BM-MSCs are potentially good candidates for brain and spinal cord injury treatment, AT-MSCs are potentially good candidates for reproductive disorder treatment and skin regeneration, and UC-MSCs are potentially good candidates for pulmonary disease and acute respiratory distress syndrome treatment.

Apoptotic vesicles inherit SOX2 from pluripotent stem cells to accelerate wound healing by energizing mesenchymal stem cells

Billions of cells undergo apoptosis every day in the human body, resulting in the generation of a large number of apoptotic vesicles (apoVs) to maintain organ and tissue homeostasis. However, the characteristics and function of pluripotent stem cell (PSC)-derived apoVs (PSC-apoVs) are largely unknown. In this study, we showed that human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) produced larger numbers of apoVs than human umbilical cord mesenchymal stem cells (UMSCs) do when induced by staurosporine. In addition to expressing the general apoV markers cleaved caspase 3, Annexin V, calreticulin, ALIX, CD63 and TSG101, ESC-apoVs inherited pluripotent-specific molecules SOX2 from ESCs in a caspase 3-dependent manner. Moreover, ESC-apoVs could promote mouse skin wound healing via transferring SOX2 into skin MSCs via activating Hippo signaling pathway. Collectively, these findings reveal that apoVs are capable of inheriting pluripotent molecules from ESCs to energize adult stem cells, suggesting the potential to use PSC-apoVs for clinical applications. STATEMENT OF SIGNIFICANCE: Apoptotic vesicles (apoVs) are essential to maintain organ and tissue homeostasis. However, the characteristics and function of pluripotent stem cell (PSC)-derived apoVs (PSC-apoVs) are largely unknown. This study showed that PSC-apoVs produced 100 times more apoVs than human umbilical cord mesenchymal stem cells (UMSCs). Despite expressing the general apoV makers, PSC-apoVs inherited pluripotent-specific molecule SOX2 from PSCs in a caspase 3-dependent manner. Moreover, PSC-apoVs promote mouse skin wound healing via transferring SOX2 into skin MSCs, thus activating Hippo signaling pathway. These findings reveal that apoVs are capable of inheriting pluripotent molecules from PSCs to energize adult stem cells, thus providing a cell-free strategy for clinical applications of PSCs.

100 plus years of stem cell research-20 years of ISSCR

The International Society for Stem Cell Research (ISSCR) celebrates its 20th anniversary in 2022. This review looks back at some of the key developments in stem cell research as well as the evolution of the ISSCR as part of that field. Important discoveries from stem cell research are described, and how the improved understanding of basic stem cell biology translates into new clinical therapies and insights into disease mechanisms is discussed. Finally, the birth and growth of ISSCR into a leading stem cell society and a respected voice for ethics, advocacy, education and policy in stem cell research are described.

Epicardial injection of allogeneic human-induced-pluripotent stem cell-derived cardiomyocytes in patients with advanced heart failure: protocol for a phase I/IIa dose-escalation clinical trial

INTRODUCTION

Heart failure (HF) is a growing global public health burden. However, due to the very limited regenerative capacity of mature cardiomyocytes in the adult mammalian heart, conventional treatments can only improve the symptoms of HF but fail to restore cardiac function. Heart transplantation is limited by a severe shortage of donors. Cell-based transplantation for the treatment of HF has become a promising strategy. Human-induced-pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have been tested in animal models to assess safety and efficacy. This study aims at evaluating the safety and efficacy of epicardial injection of hiPSC-CMs in patients with advanced HF during coronary artery bypass grafting (CABG) surgery.

METHODS

This study is a dose-escalation, placebo-controlled, single-centre phase I/IIa clinical trial. Dose escalation will be guided by a modified 3+3 design for three doses (1×10⁸, 2×10⁸ and 4×10⁸ cells, sequentially). Patients with advanced heart failure will be enrolled and randomly allocated to receive epicardial injection of hiPSC-CMs during CABG surgery or CABG surgery alone, followed by a 12-month follow-up investigation. The primary endpoint is to assess the safety of hiPSC-CMs transplantation, including haemodynamic compromised sustained ventricular arrhythmias and newly formed tumours during 6 months postoperatively. The secondary endpoint is to evaluate the efficacy of epicardial injection of hiPSC-CMs and CABG surgery combination by comparison with CABG surgery alone.

ETHICS AND DISSEMINATION

The study protocol has been approved by the Institutional Ethical Committee of Nanjing Drum Tower Hospital (No. SC202000102) and approved by National Health Commission of the PRC (MR-32-21-014649). Findings will be disseminated to the academic community through peer-reviewed publications and presentation at national and international meetings.

TRIAL REGISTRATION NUMBER

NCT03763136.

Progress in Bioengineering Strategies for Heart Regenerative Medicine

The human heart has the least regenerative capabilities among tissues and organs, and heart disease continues to be a leading cause of mortality in the industrialized world with insufficient therapeutic options and poor prognosis. Therefore, developing new therapeutic strategies for heart regeneration is a major goal in modern cardiac biology and medicine. Recent advances in stem cell biology and biotechnologies such as human pluripotent stem cells (hPSCs) and cardiac tissue engineering hold great promise for opening novel paths to heart regeneration and repair for heart disease, although these areas are still in their infancy. In this review, we summarize and discuss the recent progress in cardiac tissue engineering strategies, highlighting stem cell engineering and cardiomyocyte maturation, development of novel functional biomaterials and biofabrication tools, and their therapeutic applications involving drug discovery, disease modeling, and regenerative medicine for heart disease.

Bioengineering approaches to treat the failing heart: from cell biology to 3D printing

Successfully engineering a functional, human, myocardial pump would represent a therapeutic alternative for the millions of patients with end-stage heart disease and provide an alternative to animal-based preclinical models. Although the field of cardiac tissue engineering has made tremendous advances, major challenges remain, which, if properly resolved, might allow the clinical implementation of engineered, functional, complex 3D structures in the future. In this Review, we provide an overview of state-of-the-art studies, challenges that have not yet been overcome and perspectives on cardiac tissue engineering. We begin with the most clinically relevant cell sources used in this field and discuss the use of topological, biophysical and metabolic stimuli to obtain mature phenotypes of cardiomyocytes, particularly in relation to organized cytoskeletal and contractile intracellular structures. We then move from the cellular level to engineering planar cardiac patches and discuss the need for proper vascularization and the main strategies for obtaining it. Finally, we provide an overview of several different approaches for the engineering of volumetric organs and organ parts - from whole-heart decellularization and recellularization to advanced 3D printing technologies.

Extracorporeal Cardiac Shock Wave-Induced Exosome Derived From Endothelial Colony-Forming Cells Carrying miR-140-3p Alleviate Cardiomyocyte Hypoxia/Reoxygenation Injury via the PTEN/PI3K/AKT Pathway

Background: Stem cell-derived exosomes have great potential in the treatment of myocardial ischemia–reperfusion injury (IRI). Extracorporeal cardiac shock waves (ECSW) as effective therapy, in part, could activate the function of exosomes. In this study, we explored the effect of ECSW-induced exosome derived from endothelial colony-forming cells on cardiomyocyte hypoxia/reoxygenation (H/R) injury and its underlying mechanisms.

Methods: The exosomes were extracted and purified from the supernatant of endothelial colony-forming cells (ECFCs-exo). ECFCs-exo treated with shock wave (SW-exo) or without shock wave (CON-exo) were performed with high-throughput sequencing of the miRNA. H9c2 cells were incubated with SW-exo or CON-exo after H/R injury. The cell viability, cell apoptosis, oxidative stress level, and inflammatory factor were assessed. qRT-PCR was used to detect the expression levels of miRNA and mRNA in cells and exosomes. The PTEN/PI3K/AKT pathway-related proteins were detected by Western blotting, respectively.

Results: Exosomes secreted by ECFCs could be taken up by H9c2 cells. Administration of SW-exo to H9c2 cells after H/R injury could significantly improve cell viability, inhibit cell apoptosis, and downregulate oxidative stress level (p < 0.01), with an increase in Bcl-2 protein and a decrease in Bax, cleaved caspase-3, and NF-κB protein (p < 0.05). Notably, miR-140-3p was found to be highly enriched both in ECFCs and ECFCs-exo treated with ECSW (p < 0.05) and served as a critical mediator. SW-exo increased miR-140-3p expression but decreased PTEN expression in H9c2 cells with enhanced phosphorylation of the PI3K/AKT signaling pathway. These cardioprotective effects of SW-exo on H/R injury were blunted by the miR-140-3p inhibitor. Dual-luciferase assay verified that miR-140-3p could directly target the 3′UTR of PTEN mRNA and exert a negative regulatory effect.

Conclusion: This study has shown the potential of ECSW as an effective stimulation for the exosomes derived from ECFCs in vitro. SW-exo exerted a stronger therapeutic effect on H/R injury in H9c2 cells possibly via delivering exosomal miR-140-3p, which might be a novel promising strategy for the myocardial IRI.

Cardiac Patch Transplantation Instruments for Robotic Minimally Invasive Cardiac Surgery: Initial Proof-of-concept Designs and Surgery in a Porcine Cadaver

Background: Damaged cardiac tissues could potentially be regenerated by transplanting bioengineered cardiac patches to the heart surface. To be fully paradigm-shifting, such patches may need to be transplanted using minimally invasive robotic cardiac surgery (not only traditional open surgery). Here, we present novel robotic designs, initial prototyping and a new surgical operation for instruments to transplant patches via robotic minimally invasive heart surgery.

Methods: Robotic surgical instruments and automated control systems were designed, tested with simulation software and prototyped. Surgical proof-of-concept testing was performed on a pig cadaver.

Results: Three robotic instrument designs were developed. The first (called “Claw” for the claw-like patch holder at the tip) operates on a rack and pinion mechanism. The second design (“Shell-Beak”) uses adjustable folding plates and rods with a bevel gear mechanism. The third (“HeartStamp”) utilizes a stamp platform protruding through an adjustable ring. For the HeartStamp, rods run through a cylindrical structure designed to fit a uniportal Video-Assisted Thorascopic Surgery (VATS) surgical port. Designed to work with or without a sterile sheath, the patch is pushed out by the stamp platform as it protrudes. Two instrument robotic control systems were designed, simulated in silico and one of these underwent early ‘sizing and learning’ prototyping as a proof-of-concept. To reflect real surgical conditions, surgery was run “live” and reported exactly (as-it-happened). We successfully picked up, transferred and released a patch onto the heart using the HeartStamp in a pig cadaver model.

Conclusion: These world-first designs, early prototypes and a novel surgical operation pave the way for robotic instruments for automated keyhole patch transplantation to the heart. Our novel approach is presented for others to build upon free from restrictions or cost—potentially a significant moment in myocardial regeneration surgery which may open a therapeutic avenue for patients unfit for traditional open surgery.

MSC Pretreatment for Improved Transplantation Viability Results in Improved Ventricular Function in Infarcted Hearts

Many clinical studies utilizing MSCs (mesenchymal stem cells, mesenchymal stromal cells, or multipotential stromal cells) are underway in multiple clinical settings; however, the ideal approach to prepare these cells in vitro and to deliver them to injury sites in vivo with maximal effectiveness remains a challenge. Here, pretreating MSCs with agents that block the apoptotic pathways were compared with untreated MSCs. The treatment effects were evaluated in the myocardial infarct setting following direct injection, and physiological parameters were examined at 4 weeks post-infarct in a rat permanent ligation model. The prosurvival treated MSCs were detected in the hearts in greater abundance at 1 week and 4 weeks than the untreated MSCs. The untreated MSCs improved ejection fraction in infarcted hearts from 61% to 77% and the prosurvival treated MSCs further improved ejection fraction to 83% of normal. The untreated MSCs improved fractional shortening in the infarcted heart from 52% to 68%, and the prosurvival treated MSCs further improved fractional shortening to 77% of normal. Further improvements in survival of the MSC dose seems possible. Thus, pretreating MSCs for improved in vivo survival has implications for MSC-based cardiac therapies and in other indications where improved cell survival may improve effectiveness.

CRISPR activation of endogenous genes reprograms fibroblasts into cardiovascular progenitor cells for myocardial infarction therapy

Fibroblasts can be reprogrammed into cardiovascular progenitor cells (CPCs) using transgenic approaches, although the underlying mechanism remains unclear. We determined whether activation of endogenous genes such as Gata4, Nkx2.5, and Tbx5 can rapidly establish autoregulatory loops and initiate CPC generation in adult extracardiac fibroblasts using a CRISPR activation system. The induced fibroblasts (>80%) showed phenotypic changes as indicated by an Nkx2.5 cardiac enhancer reporter. The progenitor characteristics were confirmed by colony formation and expression of cardiovascular genes. Cardiac sphere induction segregated the early and late reprogrammed cells that can generate functional cardiomyocytes and vascular cells in vitro. Therefore, they were termed CRISPR-induced CPCs (ciCPCs). Transcriptomic analysis showed that cell cycle and heart development pathways were important to accelerate CPC formation during the early reprogramming stage. The CRISPR system opened the silenced chromatin locus, thereby allowing transcriptional factors to access their own promoters and eventually forming a positive feedback loop. The regenerative potential of ciCPCs was assessed after implantation in mouse myocardial infarction models. The engrafted ciCPCs differentiated into cardiovascular cells in vivo but also significantly improved contractile function and scar formation. In conclusion, multiplex gene activation was sufficient to drive CPC reprogramming, providing a new cell source for regenerative therapeutics.

Cardiovascular Regeneration via Stem Cells and Direct Reprogramming: A Review

Despite recent advancements in treatment strategies, cardiovascular disease such as heart failure remains a significant source of global mortality. Stem cell technology and cellular reprogramming are rapidly growing fields that will continue to prove useful in cardiac regenerative therapeutics. This review provides information on the role of human pluripotent stem cells (hPSCs) in cardiac regeneration and discusses the practical applications of hPSC-derived cardiomyocytes (CMCs). Moreover, we discuss the practical applications of hPSC-derived CMCs while outlining the relevance of directly-reprogrammed CMCs in regenerative medicine. This review critically summarizes the most recent advances in the field will help to guide future research in this developing area.

Cardiovascular disease (CVD) is the leading causes of morbidity and death globally. In particular, a heart failure remains a major problem that contributes to global mortality. Considerable advancements have been made in conventional pharmacological therapies and coronary intervention surgery for cardiac disorder treatment. However, more than 15% of patients continuously progress to end-stage heart failure and eventually require heart transplantation. Over the past year, numerous numbers of protocols to generate cardiomyocytes (CMCs) from human pluripotent stem cells (hPSCs) have been developed and applied in clinical settings. Number of studies have described the therapeutic effects of hPSCs in animal models and revealed the underlying repair mechanisms of cardiac regeneration. In addition, biomedical engineering technologies have improved the therapeutic potential of hPSC-derived CMCs in vivo. Recently substantial progress has been made in driving the direct differentiation of somatic cells into mature CMCs, wherein an intermediate cellular reprogramming stage can be bypassed. This review provides information on the role of hPSCs in cardiac regeneration and discusses the practical applications of hPSC-derived CMCs; furthermore, it outlines the relevance of directly reprogrammed CMCs in regenerative medicine.

The Present State and Future Perspectives of Cardiac Regenerative Therapy Using Human Pluripotent Stem Cells

The number of patients with heart failure (HF) is increasing with aging in our society worldwide. Patients with HF who are resistant to medication and device therapy are candidates for heart transplantation (HT). However, the shortage of donor hearts is a serious issue. As an alternative to HT, cardiac regenerative therapy using human pluripotent stem cells (hPSCs), such as human embryonic stem cells and induced pluripotent stem cells, is expected to be realized. Differentiation of hPSCs into cardiomyocytes (CMs) is facilitated by mimicking normal heart development. To prevent tumorigenesis after transplantation, it is important to eliminate non-CMs, including residual hPSCs, and select only CMs. Among many CM selection systems, metabolic selection based on the differences in metabolism between CMs and non-CMs is favorable in terms of cost and efficacy. Large-scale culture systems have been developed because a large number of hPSC-derived CMs (hPSC-CMs) are required for transplantation in clinical settings. In large animal models, hPSC-CMs transplanted into the myocardium improved cardiac function in a myocardial infarction model. Although post-transplantation arrhythmia and immune rejection remain problems, their mechanisms and solutions are under investigation. In this manner, the problems of cardiac regenerative therapy are being solved individually. Thus, cardiac regenerative therapy with hPSC-CMs is expected to become a safe and effective treatment for HF in the near future. In this review, we describe previous studies related to hPSC-CMs and discuss the future perspectives of cardiac regenerative therapy using hPSC-CMs.

Regenerative strategies for the consequences of myocardial infarction: Chronological indication and upcoming visions

Heart muscle injury and an elevated troponin level signify myocardial infarction (MI), which may result in defective and uncoordinated segments, reduced cardiac output, and ultimately, death. Physicians apply thrombolytic therapy, coronary artery bypass graft (CABG) surgery, or percutaneous coronary intervention (PCI) to recanalize and restore blood flow to the coronary arteries, albeit they were not convincingly able to solve the heart problems. Thus, researchers aim to introduce novel substitutional therapies for regenerating and functionalizing damaged cardiac tissue based on engineering concepts. Cell-based engineering approaches, utilizing biomaterials, gene, drug, growth factor delivery systems, and tissue engineering are the most leading studies in the field of heart regeneration. Also, understanding the primary cause of MI and thus selecting the most efficient treatment method can be enhanced by preparing microdevices so-called heart-on-a-chip. In this regard, microfluidic approaches can be used as diagnostic platforms or drug screening in cardiac disease treatment. Additionally, bioprinting technique with whole organ 3D printing of human heart with major vessels, cardiomyocytes and endothelial cells can be an ideal goal for cardiac tissue engineering and remarkable achievement in near future. Consequently, this review discusses the different aspects, advancements, and challenges of the mentioned methods with presenting the advantages and disadvantages, chronological indications, and application prospects of various novel therapeutic approaches.

Cell Therapy: Types, Regulation, and Clinical Benefits

Cell therapy practices date back to the 19th century and continue to expand on investigational and investment grounds. Cell therapy includes stem cell- and non-stem cell-based, unicellular and multicellular therapies, with different immunophenotypic profiles, isolation techniques, mechanisms of action, and regulatory levels. Following the steps of their predecessor cell therapies that have become established or commercialized, investigational and premarket approval-exempt cell therapies continue to provide patients with promising therapeutic benefits in different disease areas. In this review article, we delineate the vast types of cell therapy, including stem cell-based and non-stem cell-based cell therapies, and create the first-in-literature compilation of the different "multicellular" therapies used in clinical settings. Besides providing the nuts and bolts of FDA policies regulating their use, we discuss the benefits of cell therapies reported in 3 therapeutic areas-regenerative medicine, immune diseases, and cancer. Finally, we contemplate the recent attention shift toward combined therapy approaches, highlighting the factors that render multicellular therapies a more attractive option than their unicellular counterparts.

Cardiac Tissue Engineering for the Treatment of Myocardial Infarction

Poor cell engraftment rate is one of the primary factors limiting the effectiveness of cell transfer therapy for cardiac repair. Recent studies have shown that the combination of cell-based therapy and tissue engineering technology can improve stem cell engraftment and promote the therapeutic effects of the treatment for myocardial infarction. This mini-review summarizes the recent progress in cardiac tissue engineering of cardiovascular cells from differentiated human pluripotent stem cells (PSCs), highlights their therapeutic applications for the treatment of myocardial infarction, and discusses the present challenges of cardiac tissue engineering and possible future directions from a clinical perspective.

A World-First Surgical Instrument for Minimally Invasive Robotically-Enabled Transplantation of Heart Patches for Myocardial Regeneration: A Brief Research Report

Background: Patch-based approaches to regenerating damaged myocardium include epicardial surgical transplantation of heart patches. By the time this therapy is ready for widespread clinical use, it may be important that patches can be delivered via minimally invasive and robotic surgical approaches. This brief research report describes a world-first minimally invasive patch transplantation surgical device design enabled for human operation, master-slave, and fully automated robotic control. Method: Over a 12-month period (2019-20) in our multidisciplinary team we designed a surgical instrument to transplant heart patches to the epicardial surface. The device was designed for use via uni-portal or multi-portal Video-Assisted Thorascopic Surgery (VATS). For preliminary feasibility and sizing, we used a 3D printer to produce parts of a flexible resin model from a computer-aided design (CAD) software platform in preparation for more robust high-resolution metal manufacturing. Results: The instrument was designed as a sheath containing foldable arms, <2 cm in diameter when infolded to fit minimally invasive thoracic ports. The total length was 35 cm. When the arms were projected from the sheath, three moveable mechanical arms at the distal end were designed to hold a patch. Features included: a rotational head allowing for the arms to be angled in real time, a surface with micro-attachment points for patches and a releasing mechanism to release the patch. Conclusion: This brief research report represents a first step on a potential pathway towards minimally invasive robotic epicardial patch transplantation. For full feasibility testing, future proof-of-concept studies, and efficacy trials will be needed.

Extracellular vesicles in cardiovascular disease: Biological functions and therapeutic implications

Extracellular vesicles (EVs), including exosomes and microvesicles, are lipid bilayer particles naturally released from the cell. While exosomes are formed as intraluminal vesicles (ILVs) of the multivesicular endosomes (MVEs) and released to extracellular space upon MVE-plasma membrane fusion, microvesicles are generated through direct outward budding of the plasma membrane. Exosomes and microvesicles have same membrane orientation, different yet overlapping sizes; their cargo contents are selectively packed and dependent on the source cell type and functional state. Both exosomes and microvesicles can transfer bioactive RNAs, proteins, lipids, and metabolites from donor to recipient cells and influence the biological properties of the latter. Over the last decade, their potential roles as effective inter-tissue communicators in cardiovascular physiology and pathology have been increasingly appreciated. In addition, EVs are attractive sources of biomarkers for the diagnosis and prognosis of diseases, because they acquire their complex cargoes through cellular processes intimately linked to disease pathogenesis. Furthermore, EVs obtained from various stem/progenitor cell populations have been tested as cell-free therapy in various preclinical models of cardiovascular diseases and demonstrate unequivocally encouraging benefits. Here we summarize the findings from recent research on the biological functions of EVs in the ischemic heart disease and heart failure, and their potential as novel diagnostic biomarkers and therapeutic opportunities.

CHIR99021 Promotes hiPSC-Derived Cardiomyocyte Proliferation in Engineered 3D Microtissues

Cardiac tissue engineering is a promising strategy to generate human cardiac tissues for modeling cardiac diseases, screening for therapeutic drugs, and repairing the injured heart. Yet, several issues remain to be resolved including the generation of tissues with high cardiomyocyte density. Here, it is shown that the integration of the glycogen synthase kinase-3β inhibitor CHIR99021 in collagen I hydrogels promotes proliferation of human-induced pluripotent stem cell-derived (hiPSC) cardiomyocytes post-fabrication improving contractility of and calcium flow in engineered 3D cardiac microtissues. CHIR99021 has no effect on the gelation kinetics or the mechanical properties of collagen I hydrogels. Analysis of cell density and proliferation based on Ki-67 staining indicates that integration of CHIR99021 together with external CHIR99021 stimulation increases hiPSC-cardiomyocyte number by ≈2-fold within 7 d post-fabrication. Analysis of the contractility of engineered cardiac tissues after another 3 d in the absence of external CHIR99021 shows that CHIR99021-induced hiPSC-cardiomyocyte proliferation results in synchronized calcium flow, rhythmic beating, increased speed of contraction and contraction amplitude, and reduced peak-to-peak time. The CHIR99021-stimulated engineered cardiac microtissues exhibit spontaneous rhythmic contractions for at least 35 d. Collectively, the data demonstrate the potential of induced cardiomyocyte proliferation to enhance engineered cardiac microtissues by increasing cardiomyocyte density.

Elabela gene therapy promotes angiogenesis after myocardial infarction

This study was aimed at investigating whether Elabela (ELA) gene therapy can promote angiogenesis in the treatment of myocardial infarction (MI). The fusion expression plasmid pAAV-3 × Flag/ELA-32 was successfully constructed using molecular cloning technique. The model of acute MI was established by ligating the left anterior descending coronary artery in mice. Adeno-associated virus serotype 9 (AAV9) was injected into the surrounding myocardium and tail vein immediately after the model was established. AAV was injected again from the tail vein one week later. Compared with the MI+PBS (control) group, the serum N-terminal pro-brain natriuretic peptide (NT-proBNP) concentration, and the values of left ventricular end-diastolic diameter (LVDd) and left ventricular end-systolic diameter (LVDs) of the MI+AAV-ELA (gene therapy) group were significantly decreased, while the value of left ventricular ejection fraction was significantly increased at 2 and 4 weeks after operation. Compared with the control group, the expression of CD105 and vWF and the percentage of CD31- and Ki67-co-positive cells were significantly increased in the gene therapy group. Moreover, the expressions of apelin peptide jejunum (APJ) receptor, vascular endothelial growth factor (VEGF), VEGFR2, Jagged1 and Notch3 in the heart tissue around the infarction were up-regulated in mice with gene therapy. The results suggest that ELA activates VEFG/VEGFR2 and Jagged1/Notch3 pathways through APJ to promote angiogenesis after myocardial infarction. ELA gene therapy may be used in the treatment of ischaemic cardiomyopathy in future.

Non-Coding RNAs in Stem Cell Regulation and Cardiac Regeneration: Current Problems and Future Perspectives

Although advances in rapid revascularization strategies following acute myocardial infarction (AMI) have led to improved short and long-term outcomes, the associated loss of cardiomyocytes and the subsequent remodeling result in an impaired ventricular function that can lead to heart failure or death. The poor regenerative capacity of the myocardium and the current lack of effective regenerative therapies have driven stem cell research in search of a possible solution. One approach involves the delivery of stem cells to the site of injury in order to stimulate repair response. Although animal studies initially delivered promising results, the application of similar techniques in humans has been hampered by poor target site retention and oncogenic considerations. In response, several alternative strategies, including the use of non-coding RNAs (ncRNAs), have been introduced with the aim of activating and regulating stem cells or inducing stem cell status in resident cells. Circular RNAs (circRNAs) and microRNAs (miRNAs) are ncRNAs with pivotal functions in cell proliferation and differentiation, whose role in stem cell regulation and potential significance for the field of cardiac regeneration is the primary focus of this review. We also address the general advantages of ncRNAs as promising drivers of cardiac regeneration and potent stem cell regulators.

Cardiomyocyte Death and Genome-Edited Stem Cell Therapy for Ischemic Heart Disease

Massive death of cardiomyocytes is a major feature of cardiovascular diseases. Since the regenerative capacity of cardiomyocytes is limited, the regulation of their death has been receiving great attention. The cell death of cardiomyocytes is a complex mechanism that has not yet been clarified, and it is known to appear in various forms such as apoptosis, necrosis, etc. In ischemic heart disease, the apoptosis and necrosis of cardiomyocytes appear in two types of programmed forms (intrinsic and extrinsic pathways) and they account for a large portion of cell death. To repair damaged cardiomyocytes, diverse stem cell therapies have been attempted. However, despite the many positive effects, the low engraftment and survival rates have clearly limited the application of stem cells in clinical therapy. To solve these challenges, the introduction of the desired genes in stem cells can be used to enhance their capacity and improve their therapeutic efficiency. Moreover, as genome engineering technologies have advanced significantly, safer and more stable delivery of target genes and more accurate deletion of genes have become possible, which facilitates the genetic modification of stem cells. Accordingly, stem cell therapy for damaged cardiac tissue is expected to further improve. This review describes myocardial cell death, stem cell therapy for cardiac repair, and genome-editing technologies. In addition, we introduce recent stem cell therapies that incorporate genome-editing technologies in the myocardial infarction model. Graphical Abstract.

Transcriptome analysis of non human primate-induced pluripotent stem cell-derived cardiomyocytes in 2D monolayer culture vs. 3D engineered heart tissue

AIMS

Stem cell therapy has shown promise for treating myocardial infarction via re-muscularization and paracrine signalling in both small and large animals. Non-human primates (NHPs), such as rhesus macaques (Macaca mulatta), are primarily utilized in preclinical trials due to their similarity to humans, both genetically and physiologically. Currently, induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) are delivered into the infarcted myocardium by either direct cell injection or an engineered tissue patch. Although both approaches have advantages in terms of sample preparation, cell-host interaction, and engraftment, how the iPSC-CMs respond to ischaemic conditions in the infarcted heart under these two different delivery approaches remains unclear. Here, we aim to gain a better understanding of the effects of hypoxia on iPSC-CMs at the transcriptome level.

METHODS AND RESULTS

NHP iPSC-CMs in both monolayer culture (2D) and engineered heart tissue (EHT) (3D) format were exposed to hypoxic conditions to serve as surrogates of direct cell injection and tissue implantation in vivo, respectively. Outcomes were compared at the transcriptome level. We found the 3D EHT model was more sensitive to ischaemic conditions and similar to the native in vivo myocardium in terms of cell-extracellular matrix/cell-cell interactions, energy metabolism, and paracrine signalling.

CONCLUSION

By exposing NHP iPSC-CMs to different culture conditions, transcriptome profiling improves our understanding of the mechanism of ischaemic injury.

Immunological considerations and challenges for regenerative cellular therapies

The central goal of regenerative medicine is to replace damaged or diseased tissue with cells that integrate and function optimally. The capacity of pluripotent stem cells to produce unlimited numbers of differentiated cells is of considerable therapeutic interest, with several clinical trials underway. However, the host immune response represents an important barrier to clinical translation. Here we describe the role of the host innate and adaptive immune responses as triggers of allogeneic graft rejection. We discuss how the immune response is determined by the cellular therapy. Additionally, we describe the range of available in vitro and in vivo experimental approaches to examine the immunogenicity of cellular therapies, and finally we review potential strategies to ameliorate immune rejection. In conclusion, we advocate establishment of platforms that bring together the multidisciplinary expertise and infrastructure necessary to comprehensively investigate the immunogenicity of cellular therapies to ensure their clinical safety and efficacy.

Harnessing organs-on-a-chip to model tissue regeneration

Tissue engineering has markedly matured since its early beginnings in the 1980s. In addition to the original goal to regenerate damaged organs, the field has started to explore modeling of human physiology "in a dish." Induced pluripotent stem cell (iPSC) technologies now enable studies of organ regeneration and disease modeling in a patient-specific context. We discuss the potential of "organ-on-a-chip" systems to study regenerative therapies with focus on three distinct organ systems: cardiac, respiratory, and hematopoietic. We propose that the combinatorial studies of human tissues at these two scales would help realize the translational potential of tissue engineering.

Omentum support for cardiac regeneration in ischaemic cardiomyopathy models: a systematic scoping review

OBJECTIVES

Preclinical in vivo studies using omental tissue as a biomaterial for myocardial regeneration are promising and have not previously been collated. We aimed to evaluate the effects of the omentum as a support for bioengineered tissue therapy for cardiac regeneration in vivo. 

METHODS

A systematic scoping review was performed. Only English-language studies that used bioengineered cardio-regenerative tissue, omentum and ischaemic cardiomyopathy in vivo models were included.

RESULTS

We initially screened 1926 studies of which 17 were included in the final qualitative analysis. Among these, 11 were methodologically comparable and 6 were non-comparable. The use of the omentum improved the engraftment of bioengineered tissue by improving cell retention and reducing infarct size. Vascularization was also improved by the induction of angiogenesis in the transplanted tissue. Omentum-supported bioengineered grafts were associated with enhanced host reverse remodelling and improved haemodynamic measurements.

CONCLUSIONS

The omentum is a promising support for myocardial regenerative bioengineering in vivo. Future studies would benefit from more homogenous methodologies and reporting of outcomes to allow for direct comparison.

iPSCs and Exosomes: Partners in Crime Fighting Cardiovascular Diseases

Cardiovascular diseases are the leading cause of mortality worldwide. Understanding the mechanisms at the basis of these diseases is necessary in order to generate therapeutic approaches. Recently, cardiac tissue engineering and induced pluripotent stem cell (iPSC) reprogramming has led to a skyrocketing number of publications describing cardiovascular regeneration as a promising option for cardiovascular disease treatment. Generation of artificial tissue and organoids derived from induced pluripotent stem cells is in the pipeline for regenerative medicine. The present review summarizes the multiple approaches of heart regeneration with a special focus on iPSC application. In particular, we describe the strength of iPSCs as a tool to study the molecular mechanisms driving cardiovascular pathologies, as well as their potential in drug discovery. Moreover, we will describe some insights into novel discoveries of how stem-cell-secreted biomolecules, such as exosomes, could affect cardiac regeneration, and how the fine tuning of the immune system could be a revolutionary tool in the modulation of heart regeneration.

Next generation of heart regenerative therapies: progress and promise of cardiac tissue engineering

The adult heart is a vital and highly specialized organ of the human body, with limited capability of self-repair and regeneration in case of injury or disease. Engineering biomimetic cardiac tissue to regenerate the heart has been an ambition in the field of tissue engineering, tracing back to the 1990s. Increased understanding of human stem cell biology and advances in process engineering have provided an unlimited source of cells, particularly cardiomyocytes, for the development of functional cardiac muscle, even though pluripotent stem cell-derived cardiomyocytes poorly resemble those of the adult heart. This review outlines key biology-inspired strategies reported to improve cardiomyocyte maturation features and current biofabrication approaches developed to engineer clinically relevant cardiac tissues. It also highlights the potential use of this technology in drug discovery science and disease modeling as well as the current efforts to translate it into effective therapies that improve heart function and promote regeneration.