Safety and efficacy of cardiopoietic stem cells in the treatment of post-infarction left-ventricular dysfunction – From cardioprotection to functional repair in a translational pig infarction model

Stem cell-based therapy in cardiac repair after myocardial infarction: Promise, challenges, and future directions

Stem cells represent an attractive resource for cardiac regeneration. However, the survival and function of transplanted stem cells is poor and remains a major challenge for the development of effective therapies. As two main cell types currently under investigation in heart repair, mesenchymal stromal cells (MSCs) indirectly support endogenous regenerative capacities after transplantation, while induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) functionally integrate into the damaged myocardium and directly contribute to the restoration of its pump function. These two cell types are exposed to a common microenvironment with many stressors in ischemic heart tissue. This review summarizes the research progress on the mechanisms and challenges of MSCs and iPSC-CMs in post-MI heart repair, introduces several randomized clinical trials with 3D-mapping-guided cell therapy, and outlines recent findings related to the factors that affect the survival and function of stem cells. We also discuss the future directions for optimization such as biomaterial utilization, cell combinations, and intravenous injection of engineered nucleus-free MSCs.

Early to sustained impacts of lethal radiation on circulating miRNAs in a minipig model

Early diagnosis of lethal radiation is imperative since its intervention time windows are considerably short. Hence, ideal diagnostic candidates of radiation should be easily accessible, enable to inform about the stress history and objectively triage subjects in a time-efficient manner. Therefore, the small molecules such as metabolites and microRNAs (miRNAs) from plasma are legitimate biomarker candidate for lethal radiation. Our objectives were to comprehend the radiation-driven molecular pathogenesis and thereby determine biomarkers of translational potential. We investigated an established minipig model of LD70/45 total body irradiation (TBI). In this pilot study, plasma was collected pre-TBI and at multiple time points post-TBI. The majority of differentially expressed miRNAs and metabolites were perturbed immediately after TBI that potentially underlined the severity of its acute impact. The integrative network analysis of miRNA and metabolites showed a cohesive response; the early and consistent perturbations of networks were linked to cancer and the shift in musculoskeletal atrophy synchronized with the comorbidity-networks associated with inflammation and bioenergy synthesis. Subsequent comparative pipeline delivered 92 miRNAs, which demonstrated sequential homology between human and minipig, and potentially similar responses to lethal radiation across these two species. This panel promised to retrospectively inform the time since the radiation occurred; thereby could facilitate knowledge-driven interventions.

Efficacy of Stem Cell Therapy in Large Animal Models of Ischemic Cardiomyopathies: A Systematic Review and Meta-Analysis

Stem-cell therapy provides a promising strategy for patients with ischemic heart disease. In recent years, numerous studies related to this therapeutic approach were performed; however, the results were often heterogeneous and contradictory. For this reason, we conducted a systematic review and meta-analysis of trials, reporting the use of stem-cell treatment against acute or chronic ischemic cardiomyopathies in large animal models with regard to Left Ventricular Ejection Fraction (LVEF). The defined research strategy was applied to the PubMed database to identify relevant studies published from January 2011 to July 2021. A random-effect meta-analysis was performed on LVEF mean data at follow-up between control and stem-cell-treated animals. In order to improve the definition of the effect measure and to analyze the factors that could influence the outcomes, a subgroup comparison was conducted. Sixty-six studies (n = 1183 animals) satisfied our inclusion criteria. Ischemia/reperfusion infarction was performed in 37 studies, and chronic occlusion in 29 studies; moreover, 58 studies were on a pig animal model. The meta-analysis showed that cell therapy increased LVEF by 7.41% (95% Confidence Interval 6.23−8.59%; p < 0.001) at follow-up, with significative heterogeneity and high inconsistency (I2 = 82%, p < 0.001). By subgroup comparison, the follow-up after 31−60 days (p = 0.025), the late cell injection (>7 days, p = 0.005) and the route of cellular delivery by surgical treatment (p < 0.001) were significant predictors of LVEF improvement. This meta-analysis showed that stem-cell therapy may improve heart function in large animal models and that the swine specie is confirmed as a relevant animal model in the cardiovascular field. Due to the significative heterogeneity and high inconsistency, future translational studies should be designed to take into account the evidenced predictors to allow for the reduction of the number of animals used.

Hopes and Hurdles of Employing Mesenchymal Stromal Cells in the Treatment of Cardiac Fibrosis

Excessive cardiac fibrosis plays a crucial role in almost all types of heart disease. Generally, cardiac fibrosis is a scarring process triggered in response to stress, injury, or aging and is characterized by the accumulation of activated myofibroblasts that deposit high levels of extracellular matrix proteins in the myocardium. While it is beneficial for cardiac repair in the short term, it can also result in pathological remodeling, tissue stiffening, and cardiac dysfunction, contributing to the progression of heart failure, arrhythmia, and sudden cardiac death. Despite its high prevalence, there is a lack of effective and safe therapies that specifically target myofibroblasts to inhibit or even reverse pathological cardiac fibrosis. In the past few decades, cell therapy has been under continuous evaluation as a potential treatment strategy, and several studies have shown that transplantation of mesenchymal stromal cells (MSCs) can reduce cardiac fibrosis and improve heart function. Mechanistically, it is believed that the heart benefits from MSC therapy by stimulating innate anti-fibrotic and regenerative reactions. The mechanisms of action include paracrine signaling and cell-to-cell interactions. In this review, we provide an overview of the anti-fibrotic properties of MSCs and approaches to enhance them and discuss future directions of MSCs for the treatment of cardiac fibrosis.

Mesenchymal stromal cells: what have we learned so far about their therapeutic potential and mechanisms of action?

Mesenchymal stromal cells (MSCs) have been found to be safe and effective in a wide range of animal models of human disease. MSCs have been tested in thousands of clinical trials, but results show that while these cells appear to be safe, they tend to lack efficacy. This has raised questions about whether animal models are useful for predicting efficacy in patients. However, a problem with animal studies is that there is a lack of standardisation in the models and MSC therapy regimes used; there appears to be publication bias towards studies reporting positive outcomes; and the reproducibility of results from animal experiments tends not to be confirmed prior to clinical translation. A further problem is that while some progress has been made towards investigating the mechanisms of action (MoA) of MSCs, we still fail to understand how they work. To make progress, it is important to ensure that prior to clinical translation, the beneficial effects of MSCs in animal studies are real and can be repeated by independent research groups. We also need to understand the MoA of MSCs to assess whether their effects are likely to be beneficial across different species. In this review, we give an overview of the current clinical picture of MSC therapies and discuss what we have learned from animal studies. We also give a comprehensive update of what we know about the MoA of MSCs, particularly in relation to their role in immunomodulation.

Mass Customized Outlook for Regenerative Heart Failure Care

Heart failure pathobiology is permissive to reparative intent. Regenerative therapies exemplify an emerging disruptive innovation aimed at achieving structural and functional organ restitution. However, mixed outcomes, complexity in use, and unsustainable cost have curtailed broader adoption, mandating the development of novel cardio-regenerative approaches. Lineage guidance offers a standardized path to customize stem cell fitness for therapy. A case in point is the molecular induction of the cardiopoiesis program in adult stem cells to yield cardiopoietic cell derivatives designed for heart failure treatment. Tested in early and advanced clinical trials in patients with ischemic heart failure, clinical grade cardiopoietic cells were safe and revealed therapeutic improvement within a window of treatment intensity and pre-treatment disease severity. With the prospect of mass customization, cardiopoietic guidance has been streamlined from the demanding, recombinant protein cocktail-based to a protein-free, messenger RNA-based single gene protocol to engineer affordable cardiac repair competent cells. Clinical trial biobanked stem cells enabled a systems biology deconvolution of the cardiopoietic cell secretome linked to therapeutic benefit, exposing a paracrine mode of action. Collectively, this new knowledge informs next generation regenerative therapeutics manufactured as engineered cellular or secretome mimicking cell-free platforms. Launching biotherapeutics tailored for optimal outcome and offered at mass production cost would contribute to advancing equitable regenerative care that addresses population health needs.

Secretome signature of cardiopoietic cells echoed in rescued infarcted heart proteome

Stem cell paracrine activity is implicated in cardiac repair. Linkage between secretome functionality and therapeutic outcome was here interrogated by systems analytics of biobanked human cardiopoietic cells, a regenerative biologic in advanced clinical trials. Protein chip array identified 155 proteins differentially secreted by cardiopoietic cells with clinical benefit, expanded into a 520 node network, collectively revealing inherent vasculogenic properties along with cardiac and smooth muscle differentiation and development. Next generation RNA sequencing, refined by pathway analysis, pinpointed miR-146 dependent regulation upstream of the decoded secretome. Intracellular and extracellular integration unmasked commonality across cardio-vasculogenic processes. Mirroring the secretome pattern, infarcted hearts benefiting from cardiopoietic cell therapy restored the disease proteome engaging cardiovascular system functions. The cardiopoietic cell secretome thus confers a therapeutic molecular imprint on recipient hearts, with response informed by predictive systems profiling.

Investigating the Multi-Faceted Nature of Radiation-Induced Coagulopathies in a Göttingen Minipig Model of Hematopoietic Acute Radiation Syndrome

Coagulopathies are well documented after acute radiation exposure at hematopoietic doses, and radiation-induced bleeding is notably one of the two main causes of mortality in the hematopoietic acute radiation syndrome. Despite this, understanding of the mechanisms by which radiation alters hemostasis and induces bleeding is still lacking. Here, male Göttingen minipigs received hematopoietic doses of 60Co gamma irradiation (total body) and coagulopathies were characterized by assessing bleeding, blood cytopenia, fibrin deposition, changes in hemostatic properties, coagulant/anticoagulant enzyme levels, and markers of inflammation, endothelial dysfunction, and barrier integrity to understand if a relationship exists between bleeding, hemostatic defects, bone marrow aplasia, inflammation, endothelial dysfunction and loss of barrier integrity. Acute radiation exposure induced coagulopathies in the Göttingen minipig model of hematopoietic acute radiation syndrome; instances of bleeding were not dependent upon thrombocytopenia. Neutropenia, alterations in hemostatic parameters and damage to the glycocalyx occurred in all animals irrespective of occurrence of bleeding. Radiation-induced bleeding was concurrent with simultaneous thrombocytopenia, anemia, neutropenia, inflammation, increased heart rate, decreased nitric oxide bioavailability and endothelial dysfunction; bleeding was not observed with the sole occurrence of a single aforementioned parameter in the absence of the others. Alteration of barrier function or clotting proteins was not observed in all cases of bleeding. Additionally, fibrin deposition was observed in the heart and lungs of decedent animals but no evidence of DIC was noted, suggesting a unique pathophysiology of radiation-induced coagulopathies. These findings suggest radiation-induced coagulopathies are the result of simultaneous damage to several key organs and biological functions, including the immune system, the inflammatory response, the bone marrow and the cardiovasculature.

Advanced clinical imaging for the evaluation of stem cell based therapies

Introduction: As stem cell treatments reach closer to the clinic, the need for appropriate noninvasive imaging for accurate disease diagnosis, treatment planning, follow-up, and early detection of complications, is constantly rising. Clinical radiology affords an extensive arsenal of advanced imaging techniques, to provide anatomical and functional information on the whole spectrum of stem cell treatments from diagnosis to follow-up.Areas covered: This manuscript aims at providing a critical review of major published studies on the utilization of advanced imaging for stem cell treatments. Uses of magnetic resonance imaging (MRI), computed tomography (CT), ultrasound, and positron emission tomography (PET) are reviewed and interrogated for their applicability to stem cell imaging.Expert opinion: A wide spectrum of imaging methods have been utilized for the evaluation of stem cell therapies. The majority of published techniques are not clinically applicable, using methods exclusively applicable to animals or technology irrelevant to current clinical practice. Harmonization of preclinical methods with clinical reality is necessary for the timely translation of stem cell therapies to the clinic. Methods such as diffusion weighted MRI, hybrid imaging, and contrast-enhanced ultrasound hold great promise and should be routinely incorporated in the evaluation of patients receiving stem cell treatments.

[89Zr]Zr-DBN labeled cardiopoietic stem cells proficient for heart failure

INTRODUCTION

Radiolabeling of stem cells with a positron emitting radioisotope represents a major advancement in regenerative biotherapy enabling non-invasive imaging. To assess the value of such an approach in a clinically relevant scenario, the tolerability and therapeutic aptitude of [89Zr]zirconium-p-isothiocyanatobenzyl-desferrioxamine ([89Zr]Zr-DBN) labeled human cardiopoietic stem cells (CPs) were evaluated in a model of ischemic heart failure.

METHODS AND RESULTS

[89Zr]Zr-DBN based radiolabeling of human CPs yielded [89Zr]Zr-DBN-CPs with radioactivity yield of 0.70 ± 0.20 MBq/106 cells and excellent label stability. Compared to unlabeled cell counterparts, [89Zr]Zr-DBN-CPs maintained morphology, viability, and proliferation capacity with characteristic expression of mesodermal and pro-cardiogenic transcription factors defining the cardiopoietic phenotype. Administered in chronically infarcted murine hearts, [89Zr]Zr-DBN-CPs salvaged cardiac pump failure, documented by improved left ventricular ejection fraction not inferior to unlabeled CPs and notably superior to infarcted hearts without cell treatment.

CONCLUSION

The present study establishes that [89Zr]Zr-DBN labeling does not compromise stem cell identity or efficacy in the setting of heart failure, offering a non-invasive molecular imaging platform to monitor regenerative biotherapeutics post-transplantation.

Brachyury engineers cardiac repair competent stem cells

To optimize the regenerative proficiency of stem cells, a cardiopoietic protein-based cocktail consisting of multiple growth factors has been developed and advanced into clinical trials for treatment of ischemic heart failure. Streamlining the inductors of cardiopoiesis would address the resource intensive nature of the current stem cell enhancement protocol. To this end, the microencapsulated-modified-mRNA (M³ RNA) technique was here applied to introduce early cardiogenic genes into human adipose-derived mesenchymal stem cells (AMSCs). A single mesodermal transcription factor, Brachyury, was sufficient to trigger high expression of cardiopoietic markers, Nkx2.5 and Mef2c. Engineered cardiopoietic stem cells (eCP) featured a transcriptome profile distinct from pre-engineered AMSCs. In vitro, eCP demonstrated protective antioxidant capacity with enhanced superoxide dismutase expression and activity; a vasculogenic secretome driving angiogenic tube formation; and macrophage polarizing immunomodulatory properties. In vivo, in a murine model of myocardial infarction, intramyocardial delivery of eCP (600 000 cells per heart) improved cardiac performance and protected against decompensated heart failure. Thus, heart repair competent stem cells, armed with antioxidant, vasculogenic, and immunomodulatory traits, are here engineered through a protein-independent single gene manipulation, expanding the available regenerative toolkit.

Cardiopoietic stem cell therapy in ischaemic heart failure: long-term clinical outcomes

Aims

This study aims to explore long‐term clinical outcomes of cardiopoiesis‐guided stem cell therapy for ischaemic heart failure assessed in the Congestive Heart Failure Cardiopoietic Regenerative Therapy (CHART‐1) trial.

Methods and results

CHART‐1 is a multinational, randomized, and double‐blind trial conducted in 39 centres in heart failure patients (n = 315) on standard‐of‐care therapy. The ‘active’ group received cardiopoietic stem cells delivered intramyocardially using a retention‐enhanced catheter. The ‘control’ group underwent patient‐level sham procedure. Patients were followed up to 104 weeks. In the entire study population, results of the primary hierarchical composite outcome were maintained neutral at Week 52 [Mann–Whitney estimator 0.52, 95% confidence interval (CI) 0.45–0.59, P = 0.51]. Landmark analyses suggested late clinical benefit in patients with significant left ventricular enlargement receiving adequate dosing. Specifically, beyond 100 days of follow‐up, patients with left ventricular end‐diastolic volume of 200–370 mL treated with ≤19 injections of cardiopoietic stem cells showed reduced risk of death or cardiovascular hospitalization (hazard ratio 0.38, 95% CI 0.16–0.91, P = 0.031) and cardiovascular death or heart failure hospitalization (hazard ratio 0.28, 95% CI 0.09–0.94, P = 0.040). Cardiopoietic stem cell therapy was well tolerated long term with no difference in safety readouts compared with sham at 2 years.

Conclusions

Longitudinal follow‐up documents that cardiopoietic stem cell therapy is overall safe, and post hoc analyses suggest benefit in an ischaemic heart failure subpopulation defined by advanced left ventricular enlargement on tolerable stem cell dosing. The long‐term clinical follow‐up thus offers guidance for future targeted trials.

Human brain microvascular endothelial cell pairs model tissue-level blood-brain barrier function

The blood-brain barrier plays a critical role in delivering oxygen and nutrients to the brain while preventing the transport of neurotoxins. Predicting the ability of potential therapeutics and neurotoxicants to modulate brain barrier function remains a challenge due to limited spatial resolution and geometric constraints offered by existing in vitro models. Using soft lithography to control the shape of microvascular tissues, we predicted blood-brain barrier permeability states based on structural changes in human brain endothelial cells. We quantified morphological differences in nuclear, junction, and cytoskeletal proteins that influence, or indicate, barrier permeability. We established a correlation between brain endothelial cell pair structure and permeability by treating cell pairs and tissues with known cytoskeleton-modulating agents, including a Rho activator, a Rho inhibitor, and a cyclic adenosine monophosphate analog. Using this approach, we found that high-permeability cell pairs showed nuclear elongation, loss of junction proteins, and increased actin stress fiber formation, which were indicative of increased contractility. We measured traction forces generated by high- and low-permeability pairs, finding that higher stress at the intercellular junction contributes to barrier leakiness. We further tested the applicability of this platform to predict modulations in brain endothelial permeability by exposing cell pairs to engineered nanomaterials, including gold, silver-silica, and cerium oxide nanoparticles, thereby uncovering new insights into the mechanism of nanoparticle-mediated barrier disruption. Overall, we confirm the utility of this platform to assess the multiscale impact of pharmacological agents or environmental toxicants on blood-brain barrier integrity.

Cardiopoietic stem cell therapy restores infarction-altered cardiac proteome

Cardiopoietic stem cells have reached advanced clinical testing for ischemic heart failure. To profile their molecular influence on recipient hearts, systems proteomics was here applied in a chronic model of infarction randomized with and without human cardiopoietic stem cell treatment. Multidimensional label-free tandem mass spectrometry resolved and quantified 3987 proteins constituting the cardiac proteome. Infarction altered 450 proteins, reduced to 283 by stem cell treatment. Notably, cell therapy non-stochastically reversed a majority of infarction-provoked changes, remediating 85% of disease-affected protein clusters. Pathway and network analysis decoded functional reorganization, distinguished by prioritization of vasculogenesis, cardiac development, organ regeneration, and differentiation. Subproteome restoration nullified adverse ischemic effects, validated by echo-/electro-cardiographic documentation of improved cardiac chamber size, reduced QT prolongation and augmented ejection fraction post-cell therapy. Collectively, cardiopoietic stem cell intervention transitioned infarcted hearts from a cardiomyopathic trajectory towards pre-disease. Systems proteomics thus offers utility to delineate and interpret complex molecular regenerative outcomes.

Novel multimodal MRI and MicroCT imaging approach to quantify angiogenesis and 3D vascular architecture of biomaterials

Quantitative assessment of functional perfusion capacity and vessel architecture is critical when validating biomaterials for regenerative medicine purposes and requires high-tech analytical methods. Here, combining two clinically relevant imaging techniques, (magnetic resonance imaging; MRI and microcomputed tomography; MicroCT) and using the chorioallantoic membrane (CAM) assay, we present and validate a novel functional and morphological three-dimensional (3D) analysis strategy to study neovascularization in biomaterials relevant for bone regeneration. Using our new pump-assisted approach, the two scaffolds, Optimaix (laminar structure mimicking entities of the diaphysis) and DegraPol (highly porous resembling spongy bone), were shown to directly affect the architecture of the ingrowing neovasculature. Perfusion capacity (MRI) and total vessel volume (MicroCT) strongly correlated for both biomaterials, suggesting that our approach allows for a comprehensive evaluation of the vascularization pattern and efficiency of biomaterials. Being compliant with the 3R-principles (replacement, reduction and refinement), the well-established and easy-to-handle CAM model offers many advantages such as low costs, immune-incompetence and short experimental times with high-grade read-outs when compared to conventional animal models. Therefore, combined with our imaging-guided approach it represents a powerful tool to study angiogenesis in biomaterials.

Cell therapy trials for heart regeneration - lessons learned and future directions

The effects of cell therapy on heart regeneration in patients with chronic cardiomyopathy have been assessed in several clinical trials. These trials can be categorized as those using noncardiac stem cells, including mesenchymal stem cells, and those using cardiac-committed cells, including KIT⁺ cardiac stem cells, cardiosphere-derived cells, and cardiovascular progenitor cells derived from embryonic stem cells. Although the safety of cell therapies has been consistently reported, their efficacy remains more elusive. Nevertheless, several lessons have been learned that provide useful clues for future studies. This Review summarizes the main outcomes of these studies and draws some perspectives for future cell-based regenerative trials, which are largely based on the primary therapeutic target: remuscularization of chronic myocardial scars by exogenous cells or predominant use of these cells to activate host-associated repair pathways though paracrine signalling. In the first case, the study design should entail delivery of large numbers of cardiac-committed cells, supply of supportive noncardiac cells, and promotion of cell survival and appropriate coupling with endogenous cardiomyocytes. If the primary objective is to harness endogenous repair pathways, then the flexibility of cell type is greater. As the premise is that the transplanted cells need to engraft only transiently, the priority is to optimize their early retention and possibly to switch towards the sole administration of their secretome.

Large Animal Models of Heart Failure With Reduced Ejection Fraction (HFrEF)

Heart failure with reduced ejection fraction (HFrEF) is defined by an ejection fraction (EF) below 40%. Many distinct disease processes culminate in HFrEF, among them acute and chronic ischemia, pressure overload, volume overload, cytotoxic medication, and arrhythmia. To study these different etiologies the development of accurate animal models is vital. While small animal models are generally cheaper, allow for larger sample sizes and offer a greater variety of transgenic models, they have important limitations in the context of HFrEF research. Small mammals have much higher heart rates and distinct ion channels. They also have much higher basal metabolic rates and their physiology in many ways does not reflect that of humans. The size of their organs also puts practical constraints on experiments. Therefore, large animal models have been developed to accurately simulate human HFrEF. This review aims to give a short overview of the currently established large animal models of HFrEF. The main animal models discussed are dogs, pigs, and sheep. Furthermore, multiple approaches for modeling the different etiologies of HF are discussed, namely models of acute and chronic ischemia, pressure overload, volume overload as well as cytotoxic, and tachycardic pacing approaches.

Isolation, Characterization, and Differentiation of Cardiac Stem Cells from the Adult Mouse Heart

Myocardial infarction (MI) is a leading cause of morbidity and mortality around the world. A major goal of regenerative medicine is to replenish the dead myocardium after MI. Although several strategies have been used to regenerate myocardium, stem cell therapy remains a major approach to replenish the dead myocardium of an MI heart. Accumulating evidence suggests the presence of resident cardiac stem cells (CSCs) in the adult heart and their endocrine and/or paracrine effects on cardiac regeneration. However, CSC isolation and their characterization and differentiation toward myocardial cells, especially cardiomyocytes, remains a technical challenge. In the present study, we provided a simple method for the isolation, characterization, and differentiation of CSCs from the adult mouse heart. Here, we describe a density gradient method for the isolation of CSCs, where the heart is digested by a 0.2% collagenase II solution. To characterize the isolated CSCs, we evaluated the expression of CSCs/cardiac markers Sca-1, NKX2-5, and GATA4, and pluripotency/stemness markers OCT4, SOX2, and Nanog. We also determined the proliferation potential of isolated CSCs by culturing them in a Petri dish and assessing the expression of the proliferation marker Ki-67. For evaluating the differentiation potential of CSCs, we selected seven- to ten-days cultured CSCs. We transferred them to a new plate with a cardiomyocyte differentiation medium. They are incubated in a cell culture incubator for 12 days, while the differentiation medium is changed every three days. The differentiated CSCs express cardiomyocyte-specific markers: actinin and troponin I. Thus, CSCs isolated with this protocol have stemness and cardiac markers, and they have a potential for proliferation and differentiation toward cardiomyocyte lineage.

Cellular self-assembly into 3D microtissues enhances the angiogenic activity and functional neovascularization capacity of human cardiopoietic stem cells

While cell therapy has been proposed as next-generation therapy to treat the diseased heart, current strategies display only limited clinical efficacy. Besides the ongoing quest for the ideal cell type, in particular the very low retention rate of single-cell (SC) suspensions after delivery remains a major problem. To improve cellular retention, cellular self-assembly into 3D microtissues (MTs) prior to transplantation has emerged as an encouraging alternative. Importantly, 3D-MTs have also been reported to enhance the angiogenic activity and neovascularization potential of stem cells. Therefore, here using the chorioallantoic membrane (CAM) assay we comprehensively evaluate the impact of cell format (SCs versus 3D-MTs) on the angiogenic potential of human cardiopoietic stem cells, a promising second-generation cell type for cardiac repair. Biodegradable collagen scaffolds were seeded with human cardiopoietic stem cells, either as SCs or as 3D-MTs generated by using a modified hanging drop method. Thereafter, seeded scaffolds were placed on the CAM of living chicken embryos and analyzed for their perfusion capacity in vivo using magnetic resonance imaging assessment which was then linked to a longitudinal histomorphometric ex vivo analysis comprising blood vessel density and characteristics such as shape and size. Cellular self-assembly into 3D-MTs led to a significant increase of vessel density mainly driven by a higher number of neo-capillary formation. In contrast, SC-seeded scaffolds displayed a higher frequency of larger neo-vessels resulting in an overall 1.76-fold higher total vessel area (TVA). Importantly, despite that larger TVA in SC-seeded group, the mean perfusion capacity (MPC) was comparable between groups, therefore suggesting functional superiority together with an enhanced perfusion efficacy of the neo-vessels in 3D-MT-seeded scaffolds. This was further underlined by a 1.64-fold higher perfusion ratio when relating MPC to TVA. Our study shows that cellular self-assembly of human cardiopoietic stem cells into 3D-MTs substantially enhances their overall angiogenic potential and their functional neovascularization capacity. Hence, the concept of 3D-MTs may be considered to increase the therapeutic efficacy of future cell therapy concepts.

Clinical Experience With Regenerative Therapy in Heart Failure: Advancing Care With Cardiopoietic Stem Cell Interventions

Adoption of regenerative strategies for heart failure is challenged by mixed outcomes in clinical trials. Ongoing development plans strive to improve biotherapeutic potency, optimize delivery, standardize dosing, and target responsive patient populations. The Congestive Heart Failure Cardiopoietic Regenerative Therapy (CHART) program offers advanced experience in clinical development of next generation regenerative therapies.

Preparation of high bioactivity multilayered bone-marrow mesenchymal stem cell sheets for myocardial infarction using a 3D-dynamic system

Cell sheet techniques offer a promising future for myocardial infarction (MI) therapy; however, insufficient nutrition supply remains the major limitation in maintaining stem cell bioactivity in vitro. In order to enhance cell sheet mechanical strength and bioactivity, a decellularized porcine pericardium (DPP) scaffold was prepared by the phospholipase A2 method, and aspartic acid was used as a spacer arm to improve the vascular endothelial growth factor crosslink efficiency on the DPP scaffold. Based on this scaffold, multilayered bone marrow mesenchymal stem cell sheets were rapidly constructed, using RAD16-I peptide hydrogel as a temporary 3D scaffold, and cell sheets were cultured in either the 3D-dynamic system (DCcs) or the traditional static condition (SCcs). The multilayered structure, stem cell bioactivity, and ultrastructure of DCcs and SCcs were assessed. The DCcs exhibited lower apoptosis, lower differentiation, and an improved paracrine effect after a 48 h culture in vitro compared to the SCcs. Four groups were set to evaluate the cell sheet effect in rat MI model: sham group, MI control group, DCcs group, and SCcs group. The DCcs group improved cardiac function and decreased the infarcted area compared to the MI control group, while no significant improvements were observed in the SCcs group. Improved cell survival, angiogenesis, and Sca-1⁺ cell and c-kit⁺ cell amounts were observed in the DCcs group. In conclusion, the DCcs maintained higher stem cell bioactivity by using the 3D-dynamic system to provide sufficient nutrition, and transplanting DCcs significantly improved the cardiac function and angiogenesis.

STATEMENT OF SIGNIFICANCE

This study provides an efficient method to prepare vascular endothelial growth factor covalent decellularized pericardium scaffold with aspartic acid, and a multilayered bone marrow mesenchymal stem cell (BMSC) sheet is constructed on it using a 3D-dynamic system. The dynamic nutrition supply showed a significant benefit on BMSC bioactivity in vitro, including decreasing cell apoptosis, reducing stem cell differentiation, and improving growth factor secretion. These favorable bioactivity improved BMSC survival, angiogenesis, and cardiac function of the infarcted myocardium. The study highlights the importance of dynamic nutrition supply on maintaining stem cell bioactivity within cell sheet, and it stresses the necessity and significance of setting a standard for assessing cell sheet products before transplantation in the future application.

Production-scale fibronectin nanofibers promote wound closure and tissue repair in a dermal mouse model

Wounds in the fetus can heal without scarring. Consequently, biomaterials that attempt to recapitulate the biophysical and biochemical properties of fetal skin have emerged as promising pro-regenerative strategies. The extracellular matrix (ECM) protein fibronectin (Fn) in particular is believed to play a crucial role in directing this regenerative phenotype. Accordingly, Fn has been implicated in numerous wound healing studies, yet remains untested in its fibrillar conformation as found in fetal skin. Here, we show that high extensional (∼1.2 ×10⁵ s^-1) and shear (∼3 ×10⁵ s^-1) strain rates in rotary jet spinning (RJS) can drive high throughput Fn fibrillogenesis (∼10 mL/min), thus producing nanofiber scaffolds that are used to effectively enhance wound healing. When tested on a full-thickness wound mouse model, Fn nanofiber dressings not only accelerated wound closure, but also significantly improved tissue restoration, recovering dermal and epidermal structures as well as skin appendages and adipose tissue. Together, these results suggest that bioprotein nanofiber fabrication via RJS could set a new paradigm for enhancing wound healing and may thus find use in a variety of regenerative medicine applications.

Optimization of cell growth on palmitoyl-hyaluronan knitted scaffolds developed for tissue engineering applications

Polysaccharides meet several criteria for a suitable biomaterial for tissue engineering, which include biocompatibility and ability to support the delivery and growth of cells. Nevertheless, most of these polysaccharides, for example dextran, alginate, and glycosaminoglycans, are highly soluble in aqueous solutions. Hyaluronic acid hydrophobized by palmitic acid and processed to the form of wet-spun fibers and the warp-knitted textile scaffold is water non-soluble, but biodegradable material, which could be used for the tissue engineering purpose. However, its surface quality does not allow cell attachment. To enhance the biocompatibility the surface of palmitoyl-hyaluronan was roughened by freeze drying and treated by different cell adhesive proteins (fibronectin, fibrinogen, laminin, methacrylated gelatin and collagen IV). Except for collagen IV, these proteins covered the fibers uniformly for an extended period of time and supported the adhesion and cultivation of dermal fibroblasts and mesenchymal stem cells. Interestingly, adipose stem cells cultivated on the fibronectin-modified scaffold secreted increasing amount of HGF, SDF-1, and VEGF, three key growth factors involved in cardiac regeneration. These results suggested that palmitoyl-hyaluronan scaffold may be a promising material for various applications in tissue regeneration, including cardiac tissue repair. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1488-1499, 2018.

Involment of RAS/ERK1/2 signaling and MEF2C in miR-155-3p inhibition-triggered cardiomyocyte differentiation of embryonic stem cell

MicroRNAs (miRNAs) are short, noncoding RNAs that regulate post-transcriptional gene expression by targeting messenger RNAs (mRNAs) for cleavage or translational repression. Growing evidence indicates that miR-155 expression changes with the development of heart and plays an important role in heart physiopathology. However, the role of miR-155 in cardiac cells differentiation is unclear. Using the well-established embryonic stem cell (ESC), we demonstrated that miR-155-3p expression was down-regulated during cardiogenesis from mouse ESC. By contrast, the myogenic enhance factor 2C (MEF2C), a predicted target gene of miR-155-3p, was up-regulated. We further demonstrated that miR-155-3p inhibition increased the percentage of embryoid bodies (EB) beating and up-regulated the expression of cardiac specific markers, GATA4, Nkx2.5, and cTnT mRNA and protein. Notably, miR-155-3p inhibition caused upregulation of MEF2C, KRAS and ERK1/2. ERK1/2 inhibitor, PD98059 significantly decreased the expression of MEF2C protein. These findings indicate that miR-155-3p inhibition promotes cardiogenesis, and its mechanisms are involved in the RAS-ERK1/2 signaling and MEF2C.

Translational cardiac stem cell therapy: advancing from first-generation to next-generation cell types

Acute myocardial infarction and chronic heart failure rank among the major causes of morbidity and mortality worldwide. Except for heart transplantation, current therapy options only treat the symptoms but do not cure the disease. Stem cell-based therapies represent a possible paradigm shift for cardiac repair. However, most of the first-generation approaches displayed heterogeneous clinical outcomes regarding efficacy. Stemming from the desire to closely match the target organ, second-generation cell types were introduced and rapidly moved from bench to bedside. Unfortunately, debates remain around the benefit of stem cell therapy, optimal trial design parameters, and the ideal cell type. Aiming at highlighting controversies, this article provides a critical overview of the translation of first-generation and second-generation cell types. It further emphasizes the importance of understanding the mechanisms of cardiac repair and the lessons learned from first-generation trials, in order to improve cell-based therapies and to potentially finally implement cell-free therapies.