Study design and rationale for ELPIS: A phase I/IIb randomized pilot study of allogeneic human mesenchymal stem cell injection in patients with hypoplastic left heart syndrome

Research hotspots and emerging trends of mesenchymal stem cells in cardiovascular diseases: a bibliometric-based visual analysis

Background

Mesenchymal stem cells (MSCs) have important research value and broad application prospects in cardiovascular diseases (CVDs). However, few bibliometric analyses on MSCs in cardiovascular diseases are available. This study aims to provide a thorough review of the cooperation and influence of countries, institutions, authors, and journals in the field of MSCs in cardiovascular diseases, with the provision of discoveries in the latest progress, evolution paths, frontier research hotspots, and future research trends in the regarding field.

Methods

The articles related to MSCs in cardiovascular diseases were retrieved from the Web of Science. The bibliometric study was performed by CiteSpace and VOSviewer, and the knowledge map was generated based on data obtained from retrieved articles.

Results

In our study, a total of 4,852 publications launched before August 31, 2023 were accessed through the Web of Science Core Collection (WoSCC) database via our searching strategy. Significant fluctuations in global publications were observed in the field of MSCs in CVDs. China emerged as the nation with the largest number of publications, yet a shortage of high-quality articles was noted. The interplay among countries, institutions, journals and authors is visually represented in the enclosed figures. Importantly, current research trends and hotspots are elucidated. Cluster analysis on references has highlighted the considerable interest in exosomes, extracellular vesicles, and microvesicles. Besides, keywords analysis revealed a strong emphasis on myocardial infarction, therapy, and transplantation. Treatment methods-related keywords were prominent, while keywords associated with extracellular vesicles gathered significant attention from the long-term perspective.

Conclusion

MSCs in CVDs have become a topic of active research interest, showcasing its latent value and potential. By summarizing the latest progress, identifying the research hotspots, and discussing the future trends in the advancement of MSCs in CVDs, we aim to offer valuable insights for considering research prospects.

Current advances in human-induced pluripotent stem cell-based models and therapeutic approaches for congenital heart disease

Congenital heart disease (CHD) represents a significant risk factor with profound implications for neonatal survival rates and the overall well-being of adult patients. The emergence of induced pluripotent stem cells (iPSCs) and their derived cells, combined with CRISPR technology, high-throughput experimental techniques, and organoid technology, which are better suited to contemporary research demands, offer new possibilities for treating CHD. Prior investigations have indicated that the paracrine effect of exosomes may hold potential solutions for therapeutic intervention. This review provides a summary of the advancements in iPSC-based models and clinical trials associated with CHD while elucidating potential therapeutic mechanisms and delineating clinical constraints pertinent to iPSC-based therapy, thereby offering valuable insights for further deliberation.

Prospective randomized controlled trial of the safety and feasibility of a novel mesenchymal precursor cell therapy in hypoplastic left heart syndrome

Objective

To assess the safety and feasibility of low-dose, novel, allogenic mesenchymal precursor cell (MPC) therapy as an adjunct to left ventricular (LV) recruitment for patients with hypoplastic left heart syndrome (HLHS) and borderline left ventricles. MPC injections into the hypoplastic left ventricle may stimulate neovascularization and beneficial LV remodeling and may improve the likelihood of achieving biventricular (BiV) or 1.5 ventricle (1.5V) circulation.

Methods

Children <5 years with prior single ventricle palliation undergoing LV recruitment surgery at a single center were randomized to MPC injections into the LV endocardium/papillary muscles (MPCs) or standard-of-care (controls) and followed for 24 months. The primary endpoint was safety, including (serious) adverse events (S/AEs), and panel reactive antibodies (PRAs). Secondary endpoints included BiV/1.5V conversion and LV size and function.

Results

Nineteen subjects were enrolled, including 9 MPC recipients and 10 controls. Fourteen patients (74%) had >1 AE, and 2 patients had SAEs, both deemed unrelated to the trial product. AE severity and frequency were similar in the 2 groups. Baseline PRA levels were high, with no difference between the groups at 12 months. The overall probability of BiV/1.5V conversion was 0.16 (95% confidence interval [CI], 0.05 to 0.41) at 12 months and 0.52 (95% CI, 0.31 to 0.77) at 24 months. For patients with imaging data at both time points, increases in LV volumes from baseline to 12 months were larger in the MPC group by 3-dimensional echocardiography and cardiac magnetic resonance imaging. For children who successfully underwent BiV conversion (n = 12), full BiV conversion was achieved at 24 months in 5 of 5 (100%) MPC-treated children compared with 4 of 7 (57%) controls.

Conclusions

MPC injections were considered safe and feasible in HLHS patients. More than 50% of subjects underwent BiV/1.5V conversion within 2 years. Larger trials are needed to investigate the therapeutic potential of MPCs in this population.

Cell-based therapy to boost right ventricular function and cardiovascular performance in hypoplastic left heart syndrome: Current approaches and future directions

Congenital heart disease remains one of the most frequently diagnosed congenital diseases of the newborn, with hypoplastic left heart syndrome (HLHS) being considered one of the most severe. This univentricular defect was uniformly fatal until the introduction, 40 years ago, of a complex surgical palliation consisting of multiple staged procedures spanning the first 4 years of the child's life. While survival has improved substantially, particularly in experienced centers, ventricular failure requiring heart transplant and a number of associated morbidities remain ongoing clinical challenges for these patients. Cell-based therapies aimed at boosting ventricular performance are under clinical evaluation as a novel intervention to decrease morbidity associated with surgical palliation. In this review, we will examine the current burden of HLHS and current modalities for treatment, discuss various cells therapies as an intervention while delineating challenges and future directions for this therapy for HLHS and other congenital heart diseases.

Intramyocardial cell-based therapy with Lomecel-B during bidirectional cavopulmonary anastomosis for hypoplastic left heart syndrome: the ELPIS phase I trial

Aims

Hypoplastic left heart syndrome (HLHS) survival relies on surgical reconstruction of the right ventricle (RV) to provide systemic circulation. This substantially increases the RV load, wall stress, maladaptive remodelling, and dysfunction, which in turn increases the risk of death or transplantation.

Methods and results

We conducted a phase 1 open-label multicentre trial to assess the safety and feasibility of Lomecel-B as an adjunct to second-stage HLHS surgical palliation. Lomecel-B, an investigational cell therapy consisting of allogeneic medicinal signalling cells (MSCs), was delivered via intramyocardial injections. The primary endpoint was safety, and measures of RV function for potential efficacy were obtained. Ten patients were treated. None experienced major adverse cardiac events. All were alive and transplant-free at 1-year post-treatment, and experienced growth comparable to healthy historical data. Cardiac magnetic resonance imaging (CMR) suggested improved tricuspid regurgitant fraction (TR RF) via qualitative rater assessment, and via significant quantitative improvements from baseline at 6 and 12 months post-treatment (P < 0.05). Global longitudinal strain (GLS) and RV ejection fraction (EF) showed no declines. To understand potential mechanisms of action, circulating exosomes from intramyocardially transplanted MSCs were examined. Computational modelling identified 54 MSC-specific exosome ribonucleic acids (RNAs) corresponding to changes in TR RF, including miR-215-3p, miR-374b-3p, and RNAs related to cell metabolism and MAPK signalling.

Conclusion

Intramyocardially delivered Lomecel-B appears safe in HLHS patients and may favourably affect RV performance. Circulating exosomes of transplanted MSC-specific provide novel insight into bioactivity. Conduct of a controlled phase trial is warranted and is underway.Trial registration number NCT03525418.

Stem Cells and Congenital Heart Disease: The Future Potential Clinical Therapy Beyond Current Treatment

Congenital heart disease (CHD) is the most common congenital anomaly in newborns. Current treatment for cyanotic CHD largely relies on the surgical intervention; however, significant morbidity and mortality for patients with CHD remain. Recent research to explore new avenues of treating CHD includes the utility of stem cells within the field. Stem cells have since been used to both model and potentially treat CHD. Most clinical applications to date have focused on hypoplastic left heart syndrome. Here, we examine the current role of stem cells in CHD and discuss future applications within the field.

Autologous Cardiac Stem Cell Injection in Patients with Hypoplastic Left Heart Syndrome (CHILD Study)

Mortality in infants with hypoplastic left heart syndrome (HLHS) is strongly correlated with right ventricle (RV) dysfunction. Cell therapy has demonstrated potential improvements of RV dysfunction in animal models related to HLHS, and neonatal human derived c-kit⁺ cardiac-derived progenitor cells (CPCs) show superior efficacy when compared to adult human cardiac-derived CPCs (aCPCs). Neonatal CPCs (nCPCs) have yet to be investigated in humans. The CHILD trial (Autologous Cardiac Stem Cell Injection in Patients with Hypoplastic Left Heart Syndrome) is a Phase I/II trial aimed at investigating intramyocardial administration of autologous nCPCs in HLHS infants by assessing the feasibility, safety, and potential efficacy of CPC therapy. Using an open-label, multicenter design, CHILD investigates nCPC safety and feasibility in the first enrollment group (Group A/Phase I). In the second enrollment group, CHILD uses a randomized, double-blinded, multicenter design (Group B/Phase II), to assess nCPC efficacy based on RV functional and structural characteristics. The study plans to enroll 32 patients across 4 institutions: Group A will enroll 10 patients, and Group B will enroll 22 patients. CHILD will provide important insights into the therapeutic potential of nCPCs in patients with HLHS.Clinical Trial Registration https://clinicaltrials.gov/ct2/home NCT03406884, First posted January 23, 2018.

Clinical application of mesenchymal stem cell in regenerative medicine: a narrative review

The multipotency property of mesenchymal stem cells (MSCs) has attained worldwide consideration because of their immense potential for immunomodulation and their therapeutic function in tissue regeneration. MSCs can migrate to tissue injury areas to contribute to immune modulation, secrete anti-inflammatory cytokines and hide themselves from the immune system. Certainly, various investigations have revealed anti-inflammatory, anti-aging, reconstruction, and wound healing potentials of MSCs in many in vitro and in vivo models. Moreover, current progresses in the field of MSCs biology have facilitated the progress of particular guidelines and quality control approaches, which eventually lead to clinical application of MSCs. In this literature, we provided a brief overview of immunoregulatory characteristics and immunosuppressive activities of MSCs. In addition, we discussed the enhancement, utilization, and therapeutic responses of MSCs in neural, liver, kidney, bone, heart diseases, and wound healing.

Surgical Strategies in Single Ventricle Management of Neonates and Infants

No area of congenital heart disease has undergone greater change and innovation than Single Ventricle management over the past 20 years. Surgical and catheter lab interventions have transformed outcomes such that in some subgroups more than 80% of these patients can survive into adulthood. Driven by parallel development in diagnostic imaging and cardiac intensive care, surgical management is focused on the neonatal period as the key time to creating a balanced circulation and limiting pulmonary blood-flow. Different configurations of the circulation including new types of surgical shunts and the role of 'hybrid' circulations provide greater options and better physiology. This overview will focus on these changes in surgical management and timing but also look at the exciting areas of regenerative therapies to improve ventricular function, and the concept of ventricular rehabilitation to achieve biventricular circulations in certain groups of patients. The importance of early (neonatal) intervention and multidisciplinary approach to management is emphasised, as well as looking beyond simply survival but also improving neurodevelopmental outcomes.

Complications and management of functional single ventricle patients with Fontan circulation: From surgeon's point of view

Fontan surgery by step-wise completing the isolation of originally mixed pulmonary and systemic circulation provides an operative approach for functional single-ventricle patients not amenable to biventricular repair and allows their survival into adulthood. In the absence of a subpulmonic pumping chamber, however, the unphysiological Fontan circulation consequently results in diminished cardiac output and elevated central venous pressure, in which multiple short-term or long-term complications may develop. Current understanding of the Fontan-associated complications, particularly toward etiology and pathophysiology, is extremely incomplete. What's more, ongoing efforts have been made to manage these complications to weaken the Fontan-associated adverse impact and improve the life quality, but strategies are ill-defined. Herein, this review summarizes recent studies on cardiac and non-cardiac complications associated with Fontan circulation, focusing on significance or severity, etiology, pathophysiology, prevalence, risk factors, surveillance, or diagnosis. From the perspective of surgeons, we also discuss the management of the Fontan circulation based on current evidence, including post-operative administration of antithrombotic agents, ablation, pacemaker implantation, mechanical circulatory support, and final orthotopic heart transplantation, etc., to standardize diagnosis and treatment in the future.

Bidirectional relationship between cardiac extracellular matrix and cardiac cells in ischemic heart disease

Ischemic heart diseases (IHDs), including myocardial infarction and cardiomyopathies, are a leading cause of mortality and morbidity worldwide. Cardiac-derived stem and progenitor cells have shown promise as a therapeutic for IHD but are limited by poor cell survival, limited retention, and rapid washout. One mechanism to address this is to encapsulate the cells in a matrix or three-dimensional construct, so as to provide structural support and better mimic the cells' physiological microenvironment during administration. More specifically, the extracellular matrix (ECM), the native cellular support network, has been a strong candidate for this purpose. Moreover, there is a strong consensus that the ECM and its residing cells, including cardiac stem cells, have a constant interplay in response to tissue development, aging, disease progression, and repair. When externally stimulated, the cells and ECM work together to mutually maintain the local homeostasis by initially altering the ECM composition and stiffness, which in turn alters the cellular response and behavior. Given this constant interplay, understanding the mechanism of bidirectional cell-ECM interaction is essential to develop better cell implantation matrices to enhance cell engraftment and cardiac tissue repair. This review summarizes current understanding in the field, elucidating the signaling mechanisms between cardiac ECM and residing cells in response to IHD onset. Furthermore, this review highlights recent advances in native ECM-mimicking cardiac matrices as a platform for modulating cardiac cell behavior and inducing cardiac repair.

CD24 for Cardiovascular Researchers: A Key Molecule in Cardiac Immunology, Marker of Stem Cells and Target for Drug Development

The study of the membrane protein, CD24, and its emerging role in major disease processes, has made a huge leap forward in the past two decades. It appears to have various key roles in oncogenesis, tumor progression and metastasis, stem cell maintenance and immune modulation. First described in the 1980s as the homologous human protein to the mouse HSA (Heat Stable Antigen), it was reported as a surface marker in developing hematopoietic cell lines. The later discovery of its overexpression in a large number of human neoplasms, lead cancer researchers to discover its various active roles in critical checkpoints during cancer development and progression. Targeting CD24 in directed drug development showed promising results in cancer treatment. More recently, the chimeric CD24-Fc protein has shown exciting results in clinical trials as a specific modulator of auto-inflammatory syndromes. This report is aimed to summarize the relevant literature on CD24 and tie it together with recent advancements in cardiovascular research. We hypothesize that CD24 is a promising focus of research in the understanding of cardiovascular disease processes and the development of novel biological therapies.

Cell therapy for the treatment of heart disease: Renovation work on the broken heart is still in progress

Cardiovascular disease (CVD) continues to be the number one killer in the aging population. Heart failure (HF) is also an important cause of morbidity and mortality in patients with congenital heart disease (CHD). Novel therapeutic approaches that could restore stable heart function are much needed in both paediatric and adult patients. Regenerative medicine holds promises to provide definitive solutions for correction of congenital and acquired cardiac defects. In this review article, we recap some important aspects of cardiovascular cell therapy. First, we report quantifiable data regarding the scientific advancements in the field and how this has been translated into tangible outcomes according clinical studies and related meta-analyses. We then comment on emerging trends and technologies, such as the use of second-generation cell products, including pericyte-like vascular progenitors, and reprogramming of cells by different approaches including modulation of oxidative stress. The more affordable and feasible strategy of repurposing clinically available drugs to awaken the intrinsic healing potential of the heart will be discussed in the light of current social, financial, and ethical context. Cell therapy remains a work in progress field. Uncertainty in the ability of the experts and policy makers to solve urgent medical problems is growing in a world that is significantly influenced by them. This is particularly true in the field of regenerative medicine, due to great public expectations, polarization of leadership and funding, and insufficient translational vision. Cardiovascular regenerative medicine should be contextualized in a holistic program with defined priorities to allow a complete realization. Reshaping the notion of medical expertise is fundamental to fill the current gap in translation.

Stem Cell Therapy in Single-Ventricle Physiology: Recent Progress and Future Directions

Current surgical and medical treatment options for single ventricle physiology conditions remain palliative. On the long term, despite treatment, the systemic ventricle has a significant risk of developing failure. There are unmet needs to develop novel treatment modalities to help ameliorate the ventricular dysfunction. Advances in the field of stem cell therapy have been promising for the treatment of heart failure. Numerous stem cell populations have been identified. Preclinical studies in small and large animal models provide evidence for effectiveness of this treatment modality and reveal several mechanisms of action by which stem cells exert their effect. Many clinical trials have been designed to further investigate the therapeutic potential that stem cell therapy may hold for pediatric populations with single ventricle physiology. In this review, we discuss the stem cell types used in these populations, some preclinical studies, and the clinical trials of stem cell therapy in single ventricle patients.

The role of regenerative therapy in the treatment of right ventricular failure: a literature review

Right ventricular (RV) failure is a commonly encountered problem in patients with congenital heart disease but can also be a consequence of left ventricular disease, primary pulmonary hypertension, or RV-specific cardiomyopathies. Improved survival of the aforementioned pathologies has led to increasing numbers of patients suffering from RV dysfunction, making it a key contributor to morbidity and mortality in this population. Currently available therapies for heart failure were developed for the left ventricle (LV), and there is clear evidence that LV-specific strategies are insufficient or inadequate for the RV. New therapeutic strategies are needed to address this growing clinical problem, and stem cells show significant promise. However, to properly evaluate the prospects of a potential stem cell-based therapy for RV failure, one needs to understand the unique pathophysiology of RV dysfunction and carefully consider available data from animal models and human clinical trials. In this review, we provide a comprehensive overview of the molecular mechanisms involved in RV failure such as hypertrophy, fibrosis, inflammation, changes in energy metabolism, calcium handling, decreasing RV contractility, and apoptosis. We also summarize the available preclinical and clinical experience with RV-specific stem cell therapies, covering the broad spectrum of stem cell sources used to date. We describe two different scientific rationales for stem cell transplantation, one of which seeks to add contractile units to the failing myocardium, while the other aims to augment endogenous repair mechanisms and/or attenuate harmful remodeling. We emphasize the limitations and challenges of regenerative strategies, but also highlight the characteristics of the failing RV myocardium that make it a promising target for stem cell therapy.

Biomimetic nanovesicle design for cardiac tissue repair

Cardiovascular disease is a major cause of mortality and morbidity worldwide. Exosome therapies are promising for cardiac repair. Exosomes transfer cargo between cells, have high uptake by native cells and are ideal natural carriers for proteins and nucleic acids. Despite their proreparative potential, exosome production is dependent on parent cell state with typically low yields and cargo variability. Therefore, there is potential value in engineering exosomes to maximize their benefits by delivering customized, potent cargo for cardiovascular disease. Here, we outline several methods of exosome engineering focusing on three important aspects: optimizing cargo, homing to target tissue and minimizing clearance. Finally, we put these methods in context of the cardiac field and discuss the future potential of vesicle design.

Engineering better stem cell therapies for treating heart diseases

For decades, stem cells and their byproducts have shown efficacy in repairing tissues and organs in numerous pre-clinical studies and some clinical trials, providing hope for possible cures for many important diseases. However, the translation of stem cell therapy for heart diseases from bench to bed is still hampered by several limitations. The therapeutic benefits of stem cells are mediated by a combo of mechanisms. In this review, we will provide a brief summary of stem cell therapies for ischemic heart disease. Basically, we will talk about these barriers for the clinical application of stem cell-based therapies, the investigation of mechanisms behind stem-cell based cardiac regeneration and also, what bioengineers can do and have been doing on the translational stage of stem cell therapies for heart repair.

Molecular Approaches in Single Ventricle Management

Advances in medical and surgical management have significantly improved early outcomes in single ventricle congenital heart disease over the last 2 decades. Despite these advances, long-term outcomes remain suboptimal and therapeutic options to address systemic ventricular and/or Fontan failure are limited even in the modern era. Intricate molecular biologic techniques have shed light into the mechanisms of development of single ventricle disease. Efforts are underway to leverage this knowledge to improve clinical diagnosis, therapy, and prognostication. Cell-based therapies aimed at inducing cardiomyocyte proliferation and preventing delayed cardiac dysfunction have already entered the clinical realm. Several more novel biological therapies are expected to become available for patients with single ventricle disease in the near future. These scientific advancements provide us hope and reaffirm our faith that molecular medicine will usher in the next generation of therapies for single ventricle management.

Stem cell therapy for preventing neonatal diseases in the 21st century: Current understanding and challenges

Diseases of the preterm newborn such as bronchopulmonary dysplasia, necrotizing enterocolitis, cerebral palsy, and hypoxic-ischemic encephalopathy continue to be major causes of infant mortality and long-term morbidity. Effective therapies for the prevention or treatment for these conditions are still lacking as recent clinical trials have shown modest or no benefit. Stem cell therapy is rapidly emerging as a novel therapeutic tool for several neonatal diseases with encouraging pre-clinical results that hold promise for clinical translation. However, there are a number of unanswered questions and facets to the development of stem cell therapy as a clinical intervention. There is much work to be done to fully elucidate the mechanisms by which stem cell therapy is effective (e.g., anti-inflammatory versus pro-angiogenic), identifying important paracrine mediators, and determining the timing and type of therapy (e.g., cellular versus secretomes), as well as patient characteristics that are ideal. Importantly, the interaction between stem cell therapy and current, standard-of-care interventions is nearly completely unknown. In this review, we will focus predominantly on the use of mesenchymal stromal cells for neonatal diseases, highlighting the promises and challenges in clinical translation towards preventing neonatal diseases in the 21st century.

Review on Mechanical Support and Cell-Based Therapies for the Prevention and Recovery of the Failed Fontan-Kreutzer Circulation

Though the current staged surgical strategy for palliation of single ventricle heart disease, culminating in a Fontan circulation, has increased short-term survival, mounting evidence has shown that the single ventricle, especially a morphologic right ventricle (RV), is inadequate for long-term circulatory support. In addition to high rates of ventricular failure, high central venous pressures (CVP) lead to liver fibrosis or cirrhosis, lymphatic dysfunction, kidney failure, and other comorbidities. In this review, we discuss the complications seen with Fontan physiology, including causes of ventricular and multi-organ failure. We then evaluate the clinical use, results, and limitations of long-term mechanical assist devices intended to reduce RV work and high CVP, as well as biological therapies for failed Fontan circulations. Finally, we discuss experimental tissue engineering solutions designed to prevent Fontan circulation failure and evaluate knowledge gaps and needed technology development to realize a more robust single ventricle therapy.

Update on stem cell technologies in congenital heart disease

BACKGROUND

Congenital heart disease (CHD) continues to be among the most common birth defects, affecting an estimated 40 000 births annually in the United States. The most common complication of CHD is heart failure. With improved medical management and surgical outcomes, survival for complex congenital heart defects has dramatically improved, but consequentially there are more adults with CHD than children with CHD. Due to longer-term sequelae of CHD, surgical and medical treatment previously thought to be curative is now realized at best to be palliative, and there is a considerable burden of CHD-related heart failure. Stem cell therapy as an adjunct to current surgical and medical strategies is being explored in an effort to ameliorate CHD-related heart failure. This review aims to explore the current literature with regard to stem cell therapy for CHD as well as ongoing trials.

METHODS

A MEDLINE (Ovid), MEDLINE (Pubmed), and clinicaltrials.gov search were performed using the medical subject headings congenital heart defects combined with hematopoietic stem cells, stem cell transplantation, mesenchymal stem cells (MSC), cell- or tissue-based therapy, or MSC transplantation. Articles must have been published after 2010.

RESULTS

Twenty three articles and 9 ongoing trials met all inclusion criteria.

CONCLUSIONS

Areas of interest include myocardiocyte regeneration, tissue graft development to minimize reoperations, and methods of stem cell delivery. While several small trials are showing promise, it is too soon to make definitive statements about the future of stem cell therapies in this field.

Stem Cell Therapy for Hypoplastic Left Heart Syndrome: Mechanism, Clinical Application, and Future Directions

Hypoplastic left heart syndrome is a type of congenital heart disease characterized by underdevelopment of the left ventricle, outflow tract, and aorta. The condition is fatal if aggressive palliative operations are not undertaken, but even after the complete 3-staged surgical palliation, there is significant morbidity because of progressive and ultimately intractable right ventricular failure. For this reason, there is interest in developing novel therapies for the management of right ventricular dysfunction in patients with hypoplastic left heart syndrome. Stem cell therapy may represent one such innovative approach. The field has identified numerous stem cell populations from different tissues (cardiac or bone marrow or umbilical cord blood), different age groups (adult versus neonate-derived), and different donors (autologous versus allogeneic), with preclinical and clinical experience demonstrating the potential utility of each cell type. Preclinical trials in small and large animal models have elucidated several mechanisms by which stem cells affect the injured myocardium. Our current understanding of stem cell activity is undergoing a shift from a paradigm based on cellular engraftment and differentiation to one recognizing a primarily paracrine effect. Recent studies have comprehensively evaluated the individual components of the stem cells' secretomes, shedding new light on the intracellular and extracellular pathways at the center of their therapeutic effects. This research has laid the groundwork for clinical application, and there are now several trials of stem cell therapies in pediatric populations that will provide important insights into the value of this therapeutic strategy in the management of hypoplastic left heart syndrome and other forms of congenital heart disease. This article reviews the many stem cell types applied to congenital heart disease, their preclinical investigation and the mechanisms by which they might affect right ventricular dysfunction in patients with hypoplastic left heart syndrome, and finally, the completed and ongoing clinical trials of stem cell therapy in patients with congenital heart disease.

New Aspects in the Diagnosis and Therapy of Fetal Hypoplastic Left Heart Syndrome

Fetal hypoplastic left heart syndrome (HLHS) is a severe congenital heart disease with a lethal prognosis without postnatal therapeutic intervention or surgery. The aim of this article is to give a brief overview of new findings in the field of prenatal diagnosis and the therapy of HLHS. As cardiac output in HLHS children depends on the right ventricle (RV), prenatal assessment of fetal RV function is of interest to predict poor functional RV status before the RV becomes the systemic ventricle. Prenatal cardiac interventions such as fetal aortic valvuloplasty and non-invasive procedures such as maternal hyperoxygenation seem to be promising treatment options but will need to be evaluated with regard to long-term outcomes. Novel approaches such as stem cell therapy or neuroprotection provide important clues about the complexity of the disease. New aspects in diagnostics and therapy of HLHS show the potential of a targeted prenatal treatment planning. This could be used to optimize parental counseling as well as pre- and postnatal management of affected children.

Autologous stem cell therapy for hypoplastic left heart syndrome: Safety and feasibility of intraoperative intramyocardial injections

OBJECTIVES

Staged surgical palliation for hypoplastic left heart syndrome results in an increased workload on the right ventricle serving as the systemic ventricle. Concerns for cardiac dysfunction and long-term heart failure have generated interest in first-in-infant, cell-based therapies as an additional surgical treatment modality.

METHODS

A phase 1 clinical trial was conducted to evaluate the safety and feasibility of direct intramyocardial injection of autologous umbilical cord blood-derived mononuclear cells in 10 infants with hypoplastic left heart syndrome at the time of stage II palliation.

RESULTS

All 10 patients underwent successful stage II palliation and intramyocardial injection of umbilical cord blood-derived mononuclear cells. Operative mortality was 0%. There was a single adverse event related to cell delivery: An injection site epicardial bleed that required simple oversew. The cohort did not demonstrate any significant safety concerns over 6 months. Additionally, the treatment group did not demonstrate any reduction in cardiac function in the context of the study related intramyocardial injections of autologous cells.

CONCLUSIONS

This phase 1 clinical trial showed that delivering autologous umbilical cord blood-derived mononuclear cells directly into the right ventricular myocardium during planned stage II surgical palliation for hypoplastic left heart syndrome was safe and feasible. Secondary findings of preservation of baseline right ventricular function throughout follow-up and normalized growth rates support the design of a phase 2b follow-up trial.

Using Statistical Modeling to Understand and Predict Pediatric Stem Cell Function

BACKGROUND

Congenital heart defects are a leading cause of morbidity and mortality in children, and despite advanced surgical treatments, many patients progress to heart failure. Currently, transplantation is the only effective cure and is limited by donor availability and organ rejection. Recently, cell therapy has emerged as a novel method for treating pediatric heart failure with several ongoing clinical trials. However, efficacy of stem cell therapy is variable, and choosing stem cells with the highest reparative effects has been a challenge.

METHODS

We previously demonstrated the age-dependent reparative effects of human c-kit+ progenitor cells (hCPCs) in a rat model of juvenile heart failure. Using a small subset of patient samples, computational modeling analysis showed that regression models could be made linking sequencing data to phenotypic outcomes. In the current study, we used a similar quantitative model to determine whether predictions can be made in a larger population of patients and validated the model using neonatal hCPCs. We performed RNA sequencing from c-kit+ progenitor cells isolated from 32 patients, including 8 neonatal samples. We tested 2 functional parameters of our model, cellular proliferation and chemotactic potential of conditioned media.

RESULTS

Interestingly, the observed proliferation and migration responses in each of the selected neonatal hCPC lines matched their predicted counterparts. We then performed canonical pathway analysis to determine potential mechanistic signals that regulated hCPC performance and identified several immune response genes that correlated with performance. ELISA analysis confirmed the presence of selected cytokines in good performing hCPCs and provided many more signals to further validate.

CONCLUSIONS

These data show that cell behavior may be predicted using large datasets like RNA sequencing and that we may be able to identify patients whose c-kit+ progenitor cells exceed or underperform expectations. With systems biology approaches, interventions can be tailored to improve cell therapy or mimic the qualities of reparative cells.

Human Neonatal Thymus Mesenchymal Stem/Stromal Cells and Chronic Right Ventricle Pressure Overload

Right ventricle (RV) failure secondary to pressure overload is associated with a loss of myocardial capillary density and an increase in oxidative stress. We have previously found that human neonatal thymus mesenchymal stem cells (ntMSCs) promote neovascularization, but the ability of ntMSCs to express the antioxidant extracellular superoxide dismutase (SOD3) is unknown. We hypothesized that ntMSCs express and secrete SOD3 as well as improve survival in the setting of chronic pressure overload. To evaluate this hypothesis, we compared SOD3 expression in ntMSCs to donor-matched bone-derived MSCs and evaluated the effect of ntMSCs in a rat RV pressure overload model induced by pulmonary artery banding (PAB). The primary outcome was survival, and secondary measures were an echocardiographic assessment of RV size and function as well as histological studies of the RV. We found that ntMSCs expressed SOD3 to a greater degree as compared to bone-derived MSCs. In the PAB model, all ntMSC-treated animals survived to the study endpoint whereas control animals had significantly decreased survival. Treatment animals had significantly less RV fibrosis and increased RV capillary density as compared to controls. We conclude that human ntMSCs demonstrate a therapeutic effect in a model of chronic RV pressure overload, which may in part be due to their antioxidative, antifibrotic, and proangiogenic effects. Given their readily available source, human ntMSCs may be a candidate cell therapy for individuals with congenital heart disease and a pressure-overloaded RV.

Regenerative medicine therapy for single ventricle congenital heart disease

One of the most complex forms of congenital heart disease (CHD) involving single ventricle physiology is hypoplastic left heart syndrome (HLHS), characterized by underdevelopment of the left ventricle (LV), mitral and aortic valves, and narrowing of the ascending aorta. The underdeveloped LV is incapable of providing long-term systemic flow, and if left untreated, the condition is fatal. Current treatment for this condition consists of three consecutive staged palliative operations: the first is conducted within the first few weeks of birth, the second between 4 to 6 months, and the third and final surgery within the first 4 years. At the conclusion of the third surgery, systemic perfusion is provided by the right ventricle (RV), and deoxygenated blood flows passively to the pulmonary vasculature. Despite these palliative interventions, the RV, which is ill suited to provide long-term systemic perfusion, is prone to eventual failure. In the absence of satisfying curative treatments, stem cell therapy may represent one innovative approach to the management of RV dysfunction in HLHS patients. Several stem cell populations from different tissues (cardiac and non-cardiac), different age groups (adult- vs. neonate-derived), and different donors (autologous vs. allogeneic), are under active investigation. Preclinical trials in small and large animal models have elucidated several mechanisms by which these stem cells affect the injured myocardium, and are driving the shift from a paradigm based upon cellular engraftment and differentiation to one based primarily on paracrine effects. Recent studies have comprehensively evaluated the individual components of the stem cells' secretomes, shedding new light on the intracellular and extracellular pathways at the center of their therapeutic effects. This research has laid the groundwork for clinical application, and there are now several trials of stem cell therapies in pediatric populations that will provide important insights into the value of this therapeutic strategy in the management of HLHS and other forms of CHD. This article reviews the many stem cell types applied to CHD, their preclinical investigation and the mechanisms by which they might affect RV dysfunction in HLHS patients, and finally, the completed and ongoing clinical trials of stem cell therapy in patients with CHD.