Intracoronary infusion of allogeneic mesenchymal precursor cells directly after experimental acute myocardial infarction reduces infarct size, abrogates adverse remodeling, and improves cardiac function

Unveiling heterogeneity in MSCs: exploring marker-based strategies for defining MSC subpopulations

Mesenchymal stem/stromal cells (MSCs) represent a heterogeneous cell population distributed throughout various tissues, demonstrating remarkable adaptability to microenvironmental cues and holding immense promise for disease treatment. However, the inherent diversity within MSCs often leads to variability in therapeutic outcomes, posing challenges for clinical applications. To address this heterogeneity, purification of MSC subpopulations through marker-based isolation has emerged as a promising approach to ensure consistent therapeutic efficacy. In this review, we discussed the reported markers of MSCs, encompassing those developed through candidate marker strategies and high-throughput approaches, with the aim of explore viable strategies for addressing the heterogeneity of MSCs and illuminate prospective research directions in this field.

Human-umbilical cord matrix mesenchymal cells improved left ventricular contractility independently of infarct size in swine myocardial infarction with reperfusion

Background

Human umbilical cord matrix-mesenchymal stromal cells (hUCM-MSC) have demonstrated beneficial effects in experimental acute myocardial infarction (AMI). Reperfusion injury hampers myocardial recovery in a clinical setting and its management is an unmet need. We investigated the efficacy of intracoronary (IC) delivery of xenogeneic hUCM-MSC as reperfusion-adjuvant therapy in a translational model of AMI in swine.

Methods

In a placebo-controlled trial, pot-belied pigs were randomly assigned to a sham-control group (vehicle-injection; n = 8), AMI + vehicle (n = 12) or AMI + IC-injection (n = 11) of 5 × 10⁵ hUCM-MSC/Kg, within 30 min of reperfusion. AMI was created percutaneously by balloon occlusion of the mid-LAD. Left-ventricular function was blindly evaluated at 8-weeks by invasive pressure-volume loop analysis (primary endpoint). Mechanistic readouts included histology, strength-length relationship in skinned cardiomyocytes and gene expression analysis by RNA-sequencing.

Results

As compared to vehicle, hUCM-MSC enhanced systolic function as shown by higher ejection fraction (65 ± 6% vs. 43 ± 4%; p = 0.0048), cardiac index (4.1 ± 0.4 vs. 3.1 ± 0.2 L/min/m²; p = 0.0378), preload recruitable stroke work (75 ± 13 vs. 36 ± 4 mmHg; p = 0.0256) and end-systolic elastance (2.8 ± 0.7 vs. 2.1 ± 0.4 mmHg*m²/ml; p = 0.0663). Infarct size was non-significantly lower in cell-treated animals (13.7 ± 2.2% vs. 15.9 ± 2.7%; Δ = -2.2%; p = 0.23), as was interstitial fibrosis and cardiomyocyte hypertrophy in the remote myocardium. Sarcomere active tension improved, and genes related to extracellular matrix remodelling (including MMP9, TIMP1 and PAI1), collagen fibril organization and glycosaminoglycan biosynthesis were downregulated in animals treated with hUCM-MSC.

Conclusion

Intracoronary transfer of xenogeneic hUCM-MSC shortly after reperfusion improved left-ventricular systolic function, which could not be explained by the observed extent of infarct size reduction alone. Combined contributions of favourable modification of myocardial interstitial fibrosis, matrix remodelling and enhanced cardiomyocyte contractility in the remote myocardium may provide mechanistic insight for the biological effect.

Reproducing extracellular matrix adverse remodelling of non-ST myocardial infarction in a large animal model

The rising incidence of non-ST-segment elevation myocardial infarction (NSTEMI) and associated long-term high mortality constitutes an urgent clinical issue. Unfortunately, the study of possible interventions to treat this pathology lacks a reproducible pre-clinical model. Indeed, currently adopted small and large animal models of MI mimic only full-thickness, ST-segment-elevation (STEMI) infarcts, and hence cater only for an investigation into therapeutics and interventions directed at this subset of MI. Thus, we develop an ovine model of NSTEMI by ligating the myocardial muscle at precise intervals parallel to the left anterior descending coronary artery. Upon histological and functional investigation to validate the proposed model and comparison with STEMI full ligation model, RNA-seq and proteomics show the distinctive features of post-NSTEMI tissue remodelling. Transcriptome and proteome-derived pathway analyses at acute (7 days) and late (28 days) post-NSTEMI pinpoint specific alterations in cardiac post-ischaemic extracellular matrix. Together with the rise of well-known markers of inflammation and fibrosis, NSTEMI ischaemic regions show distinctive patterns of complex galactosylated and sialylated N-glycans in cellular membranes and extracellular matrix. Identifying such changes in molecular moieties accessible to infusible and intra-myocardial injectable drugs sheds light on developing targeted pharmacological solutions to contrast adverse fibrotic remodelling.

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.

Elastin-like recombinamers-based hydrogel modulates post-ischemic remodeling in a non-transmural myocardial infarction in sheep

Ischemic heart disease is a leading cause of mortality due to irreversible damage to cardiac muscle. Inspired by the post-ischemic microenvironment, we devised an extracellular matrix (ECM)-mimicking hydrogel using catalyst-free click chemistry covalent bonding between two elastin-like recombinamers (ELRs). The resulting customized hydrogel included functional domains for cell adhesion and protease cleavage sites, sensitive to cleavage by matrix metalloproteases overexpressed after myocardial infarction (MI). The scaffold permitted stromal cell invasion and endothelial cell sprouting in vitro. The incidence of non-transmural infarcts has increased clinically over the past decade, and there is currently no treatment preventing further functional deterioration in the infarcted areas. Here, we have developed a clinically relevant ovine model of non-transmural infarcts induced by multiple suture ligations. Intramyocardial injections of the degradable ELRs-hydrogel led to complete functional recovery of ejection fraction 21 days after the intervention. We observed less fibrosis and more angiogenesis in the ELRs-hydrogel-treated ischemic core region compared to the untreated animals, as validated by the expression, proteomic, glycomic, and histological analyses. These findings were accompanied by enhanced preservation of GATA4⁺ cardiomyocytes in the border zone of the infarct. We propose that our customized ECM favors cardiomyocyte preservation in the border zone by modulating the ischemic core and a marked functional recovery. The functional benefits obtained by the timely injection of the ELRs-hydrogel in a clinically relevant MI model support the potential utility of this treatment for further clinical translation.

Human umbilical cord tissue-derived mesenchymal stromal cells as adjuvant therapy for myocardial infarction: a review of current evidence focusing on pre-clinical large animal models and early human trials

Although biologically appealing, the concept of tissue regeneration underlying first- and second-generation cell therapies has failed to translate into consistent results in clinical trials. Several types of cells from different origins have been tested in pre-clinical models and in patients with acute myocardial infarction (AMI). Mesenchymal stromal cells (MSCs) have gained attention because of their potential for immune modulation and ability to promote endogenous tissue repair, mainly through their secretome. MSCs can be easily obtained from several human tissues, the umbilical cord being the most abundant source, and further expanded in culture, making them attractive as an allogeneic "of-the-shelf" cell product, suitable for the AMI setting. The available evidence concerning umbilical cord-derived MSCs in AMI is reviewed, focusing on large animal pre-clinical studies and early human trials. Molecular and cellular mechanisms as well as current limitations and possible translational solutions are also discussed.

Current Status and Limitations of Myocardial Infarction Large Animal Models in Cardiovascular Translational Research

Establishing an appropriate disease model that mimics the complexities of human cardiovascular disease is critical for evaluating the clinical efficacy and translation success. The multifaceted and complex nature of human ischemic heart disease is difficult to recapitulate in animal models. This difficulty is often compounded by the methodological biases introduced in animal studies. Considerable variations across animal species, modifications made in surgical procedures, and inadequate randomization, sample size calculation, blinding, and heterogeneity of animal models used often produce preclinical cardiovascular research that looks promising but is irreproducible and not translatable. Moreover, many published papers are not transparent enough for other investigators to verify the feasibility of the studies and the therapeutics' efficacy. Unfortunately, successful translation of these innovative therapies in such a closed and biased research is difficult. This review discusses some challenges in current preclinical myocardial infarction research, focusing on the following three major inhibitors for its successful translation: Inappropriate disease model, frequent modifications to surgical procedures, and insufficient reporting transparency.

Small Ruminants and Its Use in Regenerative Medicine: Recent Works and Future Perspectives

Simple Summary

Small ruminants such as sheep and goats have been increasingly used as animal models due to their dimensions, physiology and anatomy identical to those of humans. Their low costs, ease of accommodation, great longevity and easy handling make them advantageous animals to be used in a wide range of research work. Although there is already a lot of scientific literature describing these species, their use still lacks some standardization. The purpose of this review is to summarize the general principles related to the use of small ruminants as animal models for scientific research.

Abstract

Medical and translational scientific research requires the use of animal models as an initial approach to the study of new therapies and treatments, but when the objective is an exploration of translational potentialities, classical models fail to adequately mimic problems in humans. Among the larger animal models that have been explored more intensely in recent decades, small ruminants, namely sheep and goats, have emerged as excellent options. The main advantages associated to the use of these animals in research works are related to their anatomy and dimensions, larger than conventional laboratory animals, but very similar to those of humans in most physiological systems, in addition to their low maintenance and feeding costs, tendency to be docile, long life expectancies and few ethical complications raised in society. The most obvious disadvantages are the significant differences in some systems such as the gastrointestinal, and the reduced amount of data that limits the comparison between works and the validation of the characterization essays. Despite everything, recently these species have been increasingly used as animal models for diseases in different systems, and the results obtained open doors for their more frequent and advantageous use in the future. The purpose of this review is to summarize the general principles related to the use of small ruminants as animal models, with a focus on regenerative medicine, to group the most relevant works and results published recently and to highlight the potentials for the near future in medical research.

Fabrication of New Hybrid Scaffolds for in vivo Perivascular Application to Treat Limb Ischemia

Cell therapies are emerging as a new therapeutic frontier for the treatment of ischemic disease. However, femoral occlusions can be challenging environments for effective therapeutic cell delivery. In this study, cell-engineered hybrid scaffolds are implanted around the occluded femoral artery and the therapeutic benefit through the formation of new collateral arteries is investigated. First, it is reported the fabrication of different hybrid “hard-soft” 3D channel-shaped scaffolds comprising either poly(ε-caprolactone) (PCL) or polylactic-co-glycolic acid (PLGA) and electro-spun of gelatin (GL) nanofibers. Both PCL-GL and PLGA-GL scaffolds show anisotropic characteristics in mechanical tests and PLGA displays a greater rigidity and faster degradability in wet conditions. The resulting constructs are engineered using human adventitial pericytes (APCs) and both exhibit excellent biocompatibility. The 3D environment also induces expressional changes in APCs, conferring a more pronounced proangiogenic secretory profile. Bioprinting of alginate-pluronic gel (AG/PL), containing APCs and endothelial cells, completes the hybrid scaffold providing accurate spatial organization of the delivered cells. The scaffolds implantation around the mice occluded femoral artery shows that bioengineered PLGA hybrid scaffold outperforms the PCL counterpart accelerating limb blood flow recovery through the formation arterioles with diameters >50 μm, demonstrating the therapeutic potential in stimulating reparative angiogenesis.

Large Animal Models in Regenerative Medicine and Tissue Engineering: To Do or Not to Do

Rapid developments in Regenerative Medicine and Tissue Engineering has witnessed an increasing drive toward clinical translation of breakthrough technologies. However, the progression of promising preclinical data to achieve successful clinical market authorisation remains a bottleneck. One hurdle for progress to the clinic is the transition from small animal research to advanced preclinical studies in large animals to test safety and efficacy of products. Notwithstanding this, to draw meaningful and reliable conclusions from animal experiments it is critical that the species and disease model of choice is relevant to answer the research question as well as the clinical problem. Selecting the most appropriate animal model requires in-depth knowledge of specific species and breeds to ascertain the adequacy of the model and outcome measures that closely mirror the clinical situation. Traditional reductionist approaches in animal experiments, which often do not sufficiently reflect the studied disease, are still the norm and can result in a disconnect in outcomes observed between animal studies and clinical trials. To address these concerns a reconsideration in approach will be required. This should include a stepwise approach using in vitro and ex vivo experiments as well as in silico modeling to minimize the need for in vivo studies for screening and early development studies, followed by large animal models which more closely resemble human disease. Naturally occurring, or spontaneous diseases in large animals remain a largely untapped resource, and given the similarities in pathophysiology to humans they not only allow for studying new treatment strategies but also disease etiology and prevention. Naturally occurring disease models, particularly for longer lived large animal species, allow for studying disorders at an age when the disease is most prevalent. As these diseases are usually also a concern in the chosen veterinary species they would be beneficiaries of newly developed therapies. Improved awareness of the progress in animal models is mutually beneficial for animals, researchers, human and veterinary patients. In this overview we describe advantages and disadvantages of various animal models including domesticated and companion animals used in regenerative medicine and tissue engineering to provide an informed choice of disease-relevant animal models.

Nanomedicine for Gene Delivery for the Treatment of Cardiovascular Diseases

Background:

Myocardial infarction (MI) is the most severe ischemic heart disease and di-rectly leads to heart failure till death. Target molecules have been identified in the event of MI including increasing angiogenesis, promoting cardiomyocyte survival, improving heart function and restraining inflammation and myocyte activation and subsequent fibrosis. All of which are substantial in cardiomy-ocyte protection and preservation of cardiac function.

Methodology:

To modulate target molecule expression, virus and non-virus-mediated gene transfer have been investigated. Despite successful in animal models of MI, virus-mediated gene transfer is hampered by poor targeting efficiency, low packaging capacity for large DNA sequences, immunogenicity induced by virus and random integration into the human genome.

Discussion:

Nanoparticles could be synthesized and equipped on purpose for large-scale production. They are relatively small in size and do not incorporate into the genome. They could carry DNA and drug within the same transfer. All of these properties make them an alternative strategy for gene transfer. In the review, we first introduce the pathological progression of MI. After concise discussion on the current status of virus-mediated gene therapy in treating MI, we overview the history and development of nanoparticle-based gene delivery system. We point out the limitations and future perspective in the field of nanoparticle vehicle.

Conclusion:

Ultimately, we hope that this review could help to better understand how far we are with nanoparticle-facilitated gene transfer strategy and what obstacles we need to solve for utilization of na-nomedicine in the treatment of MI.

Selective perfusion of coronary vasculature in preterm sheep: a methodological innovation undermined by unfavourable operation of the foramen ovale

Antenatal cardiac intervention affords new prospects for hypoplastic left heart syndrome. Its success, however, may come not only from absence of impediments to blood flow but also from a sufficiently developed cardiac wall. Here, we examined the feasibility to perfuse selectively the fetal coronary circulation for treatment with growth promoting agents. Pregnant sheep (94-114 days gestation, term 145 days) were used. An aortic stop-flow procedure was developed for intracoronary access in the nonexposed fetus and human mesenchymal stem cells and their exosomes served as test agents. We found that aortic stop-flow ensures preferential distribution of fluorescent microspheres to the heart. However, intracoronary administration of stem cells or exosomes was detrimental, with fetal demise occurring around surgery or at variable intervals afterwards. Coincidentally, stop-flow caused by itself a marked rise of intraluminal pressure within the occluded aorta along with histological signs of coronary obstruction. We conclude that it is feasible to perfuse selectively the coronary circulation of the preterm fetus, but treatments are not compatible with survival of the animals. The cause for failure is found in the absence of hemodynamic compensation to stop-flow via a left-to-right shunt. This unexpected event is attributed to a largely membranous foramen ovale, characteristic of sheep, that collapses under pressure.

Macrophages in cardiac repair: Environmental cues and therapeutic strategies

Mammals, in contrast to urodeles and teleost fish, lose the ability to regenerate their hearts soon after birth. Central to this regenerative response are cardiac macrophages, which comprise a heterogeneous population of cells with origins from the yolk sac, fetal liver, and bone marrow. These cardiac macrophages maintain residency in the myocardium through local proliferation and partial replacement over time by circulating monocytes. The intrinsic plasticity of cardiac macrophages in the adult heart promotes dynamic phenotypic changes in response to environmental cues, which may either protect against injury or promote maladaptive remodeling. Thus, therapeutic strategies promoting myocardial repair are warranted. Adult stromal cell-derived exosomes have shown therapeutic promise by skewing macrophages toward a cardioprotective phenotype. While several key exosomal non-coding RNA have been identified, additional factors responsible for cardiomyocyte proliferation remain to be elucidated. Here I review cardiac macrophages in development and following injury, unravel environmental cues modulating macrophage activation, and assess novel approaches for targeted delivery.

The human heart may be coaxed toward regeneration by modifying the activity of specialized immune cells known as macrophages. Insight from the regenerating hearts of zebrafish, newt, and neonatal mammals has revealed that macrophages are required to replace scar with functioning heart tissue. As mammals lose the ability to regenerate heart tissue, macrophages mature from a regenerative phenotype towards an immunomodulatory phenotype. By adulthood, heart macrophages comprise a mixed population of cells arising from either early embryonic development or differentiation from white blood cells. In this issue, Dr. Geoffrey de Couto from the Smidt Heart Institute at Cedars-Sinai Medical Center, reviews the role of macrophages in heart repair and therapeutic strategies to enhance their activity. Recent studies suggest that exosomes, which are naturally-released nano-sized vesicles, can re-educate adult macrophages to protect the heart from injury.

Unmodified autologous stem cells at point of care for chronic myocardial infarction

BACKGROUND

Numerous studies investigated cell-based therapies for myocardial infarction (MI). The conflicting results of these studies have established the need for developing innovative approaches for applying cell-based therapy for MI. Experimental studies on animal models demonstrated the potential of fresh, uncultured, unmodified, autologous adipose-derived regenerative cells (UA-ADRCs) for treating acute MI. In contrast, studies on the treatment of chronic MI (CMI; > 4 wk post-MI) with UA-ADRCs have not been published so far. Among several methods for delivering cells to the myocardium, retrograde delivery into a temporarily blocked coronary vein has recently been demonstrated as an effective option.

AIM

To test the hypothesis that in experimentally-induced chronic myocardial infarction (CMI; > 4 wk post-MI) in pigs, retrograde delivery of fresh, uncultured, unmodified, autologous adipose-derived regenerative cells (UA-ADRCs) into a temporarily blocked coronary vein improves cardiac function and structure.

METHODS

The left anterior descending (LAD) coronary artery of pigs was blocked for 180 min at time point T0. Then, either 18 × 10⁶ UA-ADRCs prepared at “point of care” or saline as control were retrogradely delivered via an over-the-wire balloon catheter placed in the temporarily blocked LAD vein 4 wk after T0 (T1). Effects of cells or saline were assessed by cardiac magnetic resonance (CMR) imaging, late gadolinium enhancement CMR imaging, and post mortem histologic analysis 10 wk after T0 (T2).

RESULTS

Unlike the delivery of saline, delivery of UA-ADRCs demonstrated statistically significant improvements in cardiac function and structure at T2 compared to T1 (all values given as mean ± SE): Increased mean LVEF (UA-ADRCs group: 34.3% ± 2.9% at T1 vs 40.4 ± 2.6% at T2, P = 0.037; saline group: 37.8% ± 2.6% at T1 vs 36.2% ± 2.4% at T2, P > 0.999), increased mean cardiac output (UA-ADRCs group: 2.7 ± 0.2 L/min at T1 vs 3.8 ± 0.2 L/min at T2, P = 0.002; saline group: 3.4 ± 0.3 L/min at T1 vs 3.6 ± 0.3 L/min at T2, P = 0.798), increased mean mass of the left ventricle (UA-ADRCs group: 55.3 ± 5.0 g at T1 vs 71.3 ± 4.5 g at T2, P < 0.001; saline group: 63.2 ± 3.4 g at T1 vs 68.4 ± 4.0 g at T2, P = 0.321) and reduced mean relative amount of scar volume of the left ventricular wall (UA-ADRCs group: 20.9% ± 2.3% at T1 vs 16.6% ± 1.2% at T2, P = 0.042; saline group: 17.6% ± 1.4% at T1 vs 22.7% ± 1.8% at T2, P = 0.022).

CONCLUSION

Retrograde cell delivery of UA-ADRCs in a porcine model for the study of CMI significantly improved myocardial function, increased myocardial mass and reduced the formation of scar tissue.

Preclinical Studies of Stem Cell Therapy for Heart Disease

As part of the TACTICS (Transnational Alliance for Regenerative Therapies in Cardiovascular Syndromes) series to enhance regenerative medicine, here, we discuss the role of preclinical studies designed to advance stem cell therapies for cardiovascular disease. The quality of this research has improved over the past 10 to 15 years and overall indicates that cell therapy promotes cardiac repair. However, many issues remain, including inability to provide complete cardiac recovery. Recent studies question the need for intact cells suggesting that harnessing what the cells release is the solution. Our contribution describes important breakthroughs and current directions in a cell-based approach to alleviating cardiovascular disease.

Phase 3 DREAM-HF Trial of Mesenchymal Precursor Cells in Chronic Heart Failure

Advanced heart failure (HF) is a progressive disease characterized by recurrent hospitalizations and high risk of mortality. Indeed, outcomes in late stages of HF approximate those seen in patients with various aggressive malignancies. Clinical trials assessing beneficial outcomes of new treatments in patients with cancer have used innovative approaches to measure impact on total disease burden or surrogates to assess treatment efficacy. Although most cardiovascular outcomes trials continue to use time-to-first event analyses to assess the primary efficacy end point, such analyses do not adequately reflect the impact of new treatments on the totality of the chronic disease burden. Consequently, patient enrichment and other strategies for ongoing clinical trial design, as well as new statistical methodologies, are important considerations, particularly when studying a population with advanced chronic HF. The DREAM-HF trial (Double-Blind Randomized Assessment of Clinical Events With Allogeneic Mesenchymal Precursor Cells in Advanced Heart Failure) is an ongoing, randomized, sham-controlled phase 3 study of the efficacy and safety of mesenchymal precursor cells as immunotherapy in patients with advanced chronic HF with reduced ejection fraction. Mesenchymal precursor cells have a unique multimodal mechanism of action that is believed to result in polarization of proinflammatory type 1 macrophages in the heart to an anti-inflammatory type 2 macrophage state, inhibition of maladaptive adverse left ventricular remodeling, reversal of cardiac and peripheral endothelial dysfunction, and recovery of deranged vasculature. The objective of DREAM-HF is to confirm earlier phase 2 results and evaluate whether mesenchymal precursor cells will reduce the rate of nonfatal recurrent HF-related major adverse cardiac events while delaying or preventing progression of HF to terminal cardiac events. DREAM-HF is an example of an ongoing contemporary events-driven cardiovascular cell-based immunotherapy study that has utilized the concepts of baseline disease enrichment, prognostic enrichment, and predictive enrichment to improve its efficiency by using accumulating data from within as well as external to the trial. Adaptive enrichment designs and strategies are important components of a rational approach to achieve clinical research objectives in shorter clinical trial timelines and with increased cost-effectiveness without compromising ethical standards or the overall statistical integrity of the study. The DREAM-HF trial also presents an alternative approach to traditional composite time-to-first event primary efficacy end points. Statistical methodologies such as the joint frailty model provide opportunities to expand the scope of events-driven HF with reduced ejection fraction clinical trials to utilize time to recurrent nonfatal HF-related major adverse cardiac events as the primary efficacy end point without compromising the integrity of the statistical analyses for terminal cardiac events. In advanced chronic HF with reduced ejection fraction studies, the joint frailty model is utilized to reflect characteristics of the high-risk patient population with important unmet therapeutic needs. In some cases, use of the joint frailty model may substantially reduce sample size requirements. In addition, using an end point that is acceptable to the Food and Drug Administration and the European Medicines Agency, such as recurrent nonfatal HF-related major adverse cardiac events, enables generation of clinically relevant pharmacoeconomic data while providing comprehensive views of the patient's overall cardiovascular disease burden. The major goal of this review is to provide lessons learned from the ongoing DREAM-HF trial that relate to biologic plausibility and flexible clinical trial design and are potentially applicable to other development programs of innovative therapies for patients with advanced cardiovascular disease. Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02032004.

Nonocclusive multivessel intracoronary infusion of allogeneic cardiosphere-derived cells early after reperfusion prevents remote zone myocyte loss and improves global left ventricular function in swine with myocardial infarction

Intracoronary cardiosphere-derived cells (icCDCs) infused into the infarct-related artery reduce scar volume but do not improve left ventricular (LV) ejection fraction (LVEF). We tested the hypothesis that this reflects the inability of regional delivery to prevent myocyte death or promote myocyte proliferation in viable myocardium remote from the infarct. Swine (n = 23) pretreated with oral cyclosporine (200 mg/day) underwent a 1-h left anterior descending coronary artery (LAD) occlusion, which reduced LVEF from 61.6 ± 1.0 to 45.3 ± 1.5% 30 min after reperfusion. At that time, animals received global infusion of allogeneic icCDCs (n = 8), regional infusion of icCDCs restricted to the LAD using the stop-flow technique (n = 8), or vehicle (n = 7). After 1 mo, global icCDCs increased LVEF from 44.8 ± 1.9 to 60.8 ± 3.8% (P < 0.05) with no significant change after LAD stop-flow icCDCs (44.8 ± 3.6 to 50.9 ± 3.1%) or vehicle (46.5 ± 2.5 to 47.7 ± 2.6%). In contrast, global icCDCs did not alter infarct volume (%LV mass) assessed at 2 days (11.2 ± 2.3 vs. 12.6 ± 2.3%), whereas it was reduced after LAD stop-flow icCDCs (7.1 ± 1.1%, P < 0.05). Histopathological analysis of remote myocardium after global icCDCs demonstrated a significant increase in myocyte proliferation (147 ± 32 vs. 14 ± 10 nuclei/10⁶ myocytes, P < 0.05) and a reduction in myocyte apoptosis (15 ± 9 vs. 46 ± 10 nuclei/10⁶ myocytes, P < 0.05) that increased myocyte nuclear density (1,264 ± 39 vs. 1,157 ± 33 nuclei/mm², P < 0.05) and decreased myocyte diameter (13.2 ± 0.2 vs. 14.5 ± 0.3 μm, P < 0.05) compared with vehicle-treated controls. In contrast, remote zone changes after regional LAD icCDCs were no different from vehicle. These data indicate that changes in global LVEF after icCDCs are dependent upon preventing myocyte loss and hypertrophy in myocardium remote from the infarct. These arise from stimulating myocyte proliferation and reducing myocyte apoptosis indicating the importance of directing cell therapy to viable remote regions.NEW & NOTEWORTHY Administration of allogeneic cardiosphere-derived cells to the entire heart via global intracoronary infusion shortly after myocardial infarction favorably influenced left ventricular ejection fraction by preventing myocyte death and promoting myocyte proliferation in remote, noninfarcted myocardium in swine. In contrast, regional intracoronary cell infusion did not significantly affect remote zone myocyte remodeling. Global cell administration targeting viable myocardium remote from the infarct may be an effective approach to prevent adverse ventricular remodeling after myocardial infarction.

Regenerative Capacity of Adipose Derived Stem Cells (ADSCs), Comparison with Mesenchymal Stem Cells (MSCs)

Adipose tissue is now on the top one of stem cell sources regarding its accessibility, abundance, and less painful collection procedure when compared to other sources. The adipose derived stem cells (ADSCs) that it contains can be maintained and expanded in culture for long periods of time without losing their differentiation capacity, leading to large cell quantities being increasingly used in cell therapy purposes. Many reports showed that ADSCs-based cell therapy products demonstrated optimal efficacy and efficiency in some clinical indications for both autologous and allogeneic purposes, hence becoming considered as potential tools for replacing, repairing, and regenerating dead or damaged cells. In this review, we analyzed the therapeutic advancement of ADSCs in comparison to bone marrow (BM) and umbilical cord (UC)-mesenchymal stem cells (MSCs) and designed the specific requirements to their best clinical practices and safety. Our analysis was focused on the ADSCs, rather than the whole stromal vascular fraction (SVF) cell populations, to facilitate characterization that is related to their source of origins. Clinical outcomes improvement suggested that these cells hold great promise in stem cell-based therapies in neurodegenerative, cardiovascular, and auto-immunes diseases.

Regenerative Capacity of Adipose Derived Stem Cells (ADSCs), Comparison with Mesenchymal Stem Cells (MSCs)

Adipose tissue is now on the top one of stem cell sources regarding its accessibility, abundance, and less painful collection procedure when compared to other sources. The adipose derived stem cells (ADSCs) that it contains can be maintained and expanded in culture for long periods of time without losing their differentiation capacity, leading to large cell quantities being increasingly used in cell therapy purposes. Many reports showed that ADSCs-based cell therapy products demonstrated optimal efficacy and efficiency in some clinical indications for both autologous and allogeneic purposes, hence becoming considered as potential tools for replacing, repairing, and regenerating dead or damaged cells. In this review, we analyzed the therapeutic advancement of ADSCs in comparison to bone marrow (BM) and umbilical cord (UC)-mesenchymal stem cells (MSCs) and designed the specific requirements to their best clinical practices and safety. Our analysis was focused on the ADSCs, rather than the whole stromal vascular fraction (SVF) cell populations, to facilitate characterization that is related to their source of origins. Clinical outcomes improvement suggested that these cells hold great promise in stem cell-based therapies in neurodegenerative, cardiovascular, and auto-immunes diseases.

Apoptosis of mesenchymal stem cells is regulated by Rspo1 via the Wnt/β-catenin signaling pathway

Objective

The aim of this study was to investigate the effect and possible mechanism of action of roof plate-specific spondin1 (Rspo1) in the apoptosis of rat bone marrow mesenchymal stem cells (BMSCs).

Methods

Osteogenic and adipogenic differentiation of BMSCs was identified by Alizarin Red and Oil Red O staining, respectively. BMSC surface markers (cluster of differentiation 29 [CD29], CD90, and CD45) were detected using flow cytometry. BMSCs were transfected with an adenoviral vector encoding Rspo1 (BMSCs-Rspo1 group). The expression levels of Rspo1 gene and Rspo1 protein in the BMSCs-Rspo1 group and the two control groups (untransfected BMSCs group and BMSCs-green fluorescent protein [GFP] group) were analyzed and compared by quantitative polymerase chain reaction and Western blot. The occurrence of apoptosis in the three groups was detected by flow cytometry and acridine orange-ethidium bromide (AO-EB) double dyeing. The activity of the Wnt/β-catenin signaling pathway was evaluated by measuring the expression levels of the key proteins of the pathway (β-catenin, c-Jun N-terminal kinase [JNK], and phospho-JNK).

Results

Osteogenic and adipogenic differentiation was confirmed in cultured BMSCs by the positive expression of CD29 and CD90 and the negative expression of CD45. Significantly increased expression levels of Rspo1 protein in the BMSCs-Rspo1 group compared to those in the BMSCs (0.60 ± 0.05 vs. 0.13 ± 0.02; t=95.007, P=0.001) and BMSCs-GFP groups (0.60 ± 0.05 vs. 0.10 ± 0.02; t=104.842, P=0.001) were observed. The apoptotic rate was significantly lower in the BMSCs-Rspo1 group compared with those in the BMSCs group ([24.06 ± 2.37]% vs. [40.87 ± 2.82]%; t = 49.872, P = 0.002) and the BMSCs-GFP group ([24.06 ± 2.37]% vs. [42.34 ± 0.26]%; t = 62.358, P = 0.001). In addition, compared to the BMSCs group, the protein expression levels of β-catenin (2.67 ± 0.19 vs. 1.14 ± 0.14; t = −9.217, P = 0.000) and JNK (1.87 ± 0.17 vs. 0.61 ± 0.07; t = −22.289, P = 0.000) were increased in the BMSCs-Rspo1 group. Compared to the BMSCs-GFP group, the protein expression levels of β-catenin (2.67 ± 0.19 vs. 1.44 ± 0.14; t = −5.692, P = 0.000) and JNK (1.87 ± 0.17 vs. 0.53 ± 0.06; t = −10.589, P = 0.000) were also upregulated in the BMSCs-Rspo1 group. Moreover, the protein expression levels of phospho-JNK were increased in the BMSCs-Rspo1 group compared to those in the BMSCs group (1.89 ± 0.10 vs. 0.63 ± 0.09; t = −8.975, P = 0.001) and the BMSCs-GFP group (1.89 ± 0.10 vs. 0.69 ± 0.08; t = −9.483, P = 0.001).

Conclusion

The Wnt/β-catenin pathway could play a vital role in the Rspo1-mediated inhibition of apoptosis in BMSCs.

Cellular and molecular approaches to enhance myocardial recovery after myocardial infarction

Reperfusion therapy has resulted in significant improvement in post-myocardial infarction morbidity and mortality in over the last 4 decades. Nonetheless, it is well recognized that simply restoring patency of the epicardial artery may not stop or reverse damage at microvascular level, and myocardial salvage is often suboptimal. Numerous efforts have been undertaken to elucidate the mechanisms underlying extensive myonecrosis to facilitate the discovery of therapies to provide additional and incremental benefits over current therapeutic pathways. To date, conclusively effective strategies to promote myocardial recovery have not yet been established. Novel approaches are investigating the foundational cellular and molecular bases of myocardial ischemia and irreversible injury. Herein, we review the emerging concepts and proposed therapies that may improve myocardial protection and reduce infarct size. We examine the preclinical and clinical evidence for reduced infarct size with these strategies, including anti-inflammatory agents, intracellular ion channel modulators, agents affecting the reperfusion injury salvage kinase (RISK) and nitric oxide signaling pathways, modulators of mitochondrial function, anti-apoptotic agents, and stem cell and gene therapy. We review the potential reasons of failures to date and the potential for new strategies to further promote myocardial recovery and improve prognosis.

Is Cardioprotection Dead?

For >4 decades, the holy grail in the treatment of acute myocardial infarction has been the mitigation of lethal injury. Despite promising initial results and decades of investigation by the cardiology research community, the only treatment with proven efficacy is early reperfusion of the occluded coronary artery. The remarkable record of failure has led us and others to wonder if cardioprotection is dead. The path to translation, like the ascent to Everest, is certainly littered with corpses. We do, however, highlight a therapeutic principle that provides a glimmer of hope: cellular postconditioning. Administration of cardiosphere-derived cells after reperfusion limits infarct size measured acutely, while providing long-term structural and functional benefits. The recognition that cell therapy may be cardioprotective, and not just regenerative, merits further exploration before we abandon the pursuit entirely.

Paracrine Effects of Mesenchymal Stromal Cells Cultured in Three-Dimensional Settings on Tissue Repair

Mesenchymal stromal cells (MSCs) are a promising cell source for promoting tissue repair, due to their ability to release growth, angiogenic, and immunomodulatory factors. However, when injected as a suspension, these cells suffer from poor survival and localization, and suboptimal release of paracrine factors. While there have been attempts to overcome these limitations by modifying MSCs themselves, a more versatile solution is to grow them in three dimensions, as aggregates or embedded into biomaterials. Here we review the mechanisms by which 3D culture can influence the regenerative capacity of undifferentiated MSCs, focusing on recent examples from the literature. We further discuss how knowledge of these mechanisms can lead to strategic design of MSC therapies that overcome some of the challenges to their effective translation.

Intracoronary Administration of Allogeneic Adipose Tissue-Derived Mesenchymal Stem Cells Improves Myocardial Perfusion But Not Left Ventricle Function, in a Translational Model of Acute Myocardial Infarction

BACKGROUND

Autologous adipose tissue-derived mesenchymal stem cells (ATMSCs) therapy is a promising strategy to improve post-myocardial infarction outcomes. In a porcine model of acute myocardial infarction, we studied the long-term effects and the mechanisms involved in allogeneic ATMSCs administration on myocardial performance.

METHODS AND RESULTS

Thirty-eight pigs underwent 50 minutes of coronary occlusion; the study was completed in 33 pigs. After reperfusion, allogeneic ATMSCs or culture medium (vehicle) were intracoronarily administered. Follow-ups were performed at short (2 days after acute myocardial infarction vehicle-treated, n=10; ATMSCs-treated, n=9) or long term (60 days after acute myocardial infarction vehicle-treated, n=7; ATMSCs-treated, n=7). At short term, infarcted myocardium analysis showed reduced apoptosis in the ATMSCs-treated animals (48.6±6% versus 55.9±5.7% in vehicle; P=0.017); enhancement of the reparative process with up-regulated vascular endothelial growth factor, granulocyte macrophage colony-stimulating factor, and stromal-derived factor-1α gene expression; and increased M2 macrophages (67.2±10% versus 54.7±10.2% in vehicle; P=0.016). In long-term groups, increase in myocardial perfusion at the anterior infarct border was observed both on day-7 and day-60 cardiac magnetic resonance studies in ATMSCs-treated animals, compared to vehicle (87.9±28.7 versus 57.4±17.7 mL/min per gram at 7 days; P=0.034 and 99±22.6 versus 43.3±14.7 22.6 mL/min per gram at 60 days; P=0.0001, respectively). At day 60, higher vascular density was detected at the border zone in the ATMSCs-treated animals (118±18 versus 92.4±24.3 vessels/mm2 in vehicle; P=0.045). Cardiac magnetic resonance-measured left ventricular ejection fraction of left ventricular volumes was not different between groups at any time point.

CONCLUSIONS

In this porcine acute myocardial infarction model, allogeneic ATMSCs-based therapy was associated with increased cardioprotective and reparative mechanisms and with better cardiac magnetic resonance-measured perfusion. No effect on left ventricular volumes or ejection fraction was observed.

Rational transplant timing and dose of mesenchymal stromal cells in patients with acute myocardial infarction: a meta-analysis of randomized controlled trials

Background

Mesenchymal stromal cells (MSCs) are considered to have a modest benefit on left ventricular ejection fraction (LVEF) in patients with acute myocardial infarction (AMI). However, the optimal injection timing and dose needed to induce beneficial cardiac effects are unknown. The purpose of this meta-analysis was to identify an optimal MSC transplantation time and cell dose in the setting of AMI to achieve better clinical endpoints.

Methods

The authors conducted a systematic review of studies published up to June 2016 by searching PubMed, EMBASE, MEDLINE, and the Cochrane Library for relevant randomized controlled trials (RCTs).

Results

Eight prospective RCTs with 449 participants were included. The pooled results revealed that patients in the MSC group had no significant increase in LVEF from baseline compared with that in the control group (1.47% increase, 95% confidence interval (CI) −4.5 to 7.45; I² = 97%; P > 0.05). A subgroup analysis was conducted to explore the results according to differences in transplantation time and dose of MSCs injected. For transplantation timing, the LVEF of patients accepting a MSC infusion within 1 week was significantly increased by 3.22% (95% CI 1.31 to 5.14; I² = 0; P < 0.05), but this increase was insignificant in the group that accepted an MSC infusion after 1 week (−0.35% in LVEF, 95% CI −10.22 to 9.52; I² = 99%; P > 0.05). Furthermore, patients accepting a MSC dose of less than 10⁷ cells exhibited an LVEF improvement of 2.25% compared with the control (95% CI 0.56 to 3.93; I² = 9%; P < 0.05). Combining transplantation time and cell dose indicates that a significant improvement of LVEF of 3.32% was achieved in the group of patients injected with <10⁷ MSCs within 1 week (95% CI 1.14 to 5.50; I² = 0; P = 0.003).

Conclusions

Transplantation time and injected cell dose are key factors that determine the therapeutic effect of stem cell therapy. The injection of no more than 10⁷ MSCs within 1 week for AMI after percutaneous coronary intervention might improve left ventricular systolic function. Further studies on the mechanism and the effectiveness of MSCs for long-term therapy are warranted.

Adipose-Derived Cell Transplantation in Systemic Sclerosis: State of the Art and Future Perspectives

Systemic sclerosis (SSc) is one of the most complex connective tissue diseases. Although significant progress in the knowledge of pathogenic mechanisms and timely diagnosis, therapeutic options remain limited. The attempt to find new treatments for SSc has led researchers to investigate the potential of cellular therapies using autologous and allogeneic stem cells. Multipotent mesenchymal stromal cells (MSCs) are considered an attractive candidate for cell-based therapies. MSCs comprise a heterogeneous population of cells with multilineage differentiation potential that are preferentially able to home to the sites of damage, and secrete various cytokines and growth factors that can have immunomodulatory, angiogenic, anti-inflammatory and anti-apoptotic effects. MSCs from bone-marrow have been first extensively characterized. Adipose tissue represents an additional abundant and accessible source of stem cells. Compared with BM-MSCs, adipose-derived stromal/stem cells (ASCs) offer several advantages, including ease of isolation, less donor morbidity, relative abundance, and rapidity of expansion. For all these reasons, at present ASCs are one of the most attractive and promising sources of adult stem cells for cell therapy, finding a field of application in the treatment of SSc, too. This review will focus on the current applications and possible future perspectives of adipose tissue-cell therapies in SSc.

Short- and Long-term Therapeutic Efficacies of Intravenous Transplantation of Bone Marrow Stem Cells on Cardiac Function in Rats with Acute Myocardial Infarction: A Meta-analysis of Randomized Controlled Trials

<strong>Objective</strong> To investigate the short- and long-term therapeutic efficacies of intravenous trans- plantation of bone marrow stem cells (MSCs) in rats with experimental myocardial infarction by meta- analysis. <strong>Methods</strong> Randomized controlled trials were systematically searched from PubMed, Science Citation Index (SCI), Chinese journal full-text database (CJFD) up to December 2014. While the experimental groups (MSCs groups) were injected MSCs intravenously, the control groups were injected Delubecco's minimum essential medium (DMEM) or phosphate buffered saline (PBS). Subgroup analysis for each outcome measure was performed for the observing time point after the transplantation of MSCs. Weighted mean differences (WMD) and 95% confidence intervals (CI) were calculated for outcome parameters including ejection fraction (EF) and fractional shortening (FS), which were measured by echocardiogram after intravenous injection and analyzed by RevMan 5.2 and STATA 12.0. <strong>Results</strong> Data from 9 studies (190 rats) were included in the meta-analysis. As compared to the control groups, the cardiac function of the experimental groups were not improved at day 7 (EF: WMD=0.08, 95%CI -1.32 to 1.16, P>0.01; FS: WMD=-0.12, 95%CI -0.90 to 0.65, P>0.01) until at day 14 after MSCs' transplantation (EF: WMD=10.79, 95%CI 9.16 to 12.42, P<0.01; FS: WMD=11.34, 95%CI 10.44 to 12.23, P<0.01), and it lasted 4 weeks or more after transplantation of MSCs (EF: WMD=13.94, 95%CI 12.24 to 15.64, P<0.01; FS: WMD=9.64, 95%CI 7.98 to 11.31, P<0.01). <strong>Conclusion</strong> The therapeutic efficacies of MSCs in rats with myocardid infarction become increasing apparent as time advances since 2 weeks after injection.

Therapeutic use of stem cells for cardiovascular disease

Stem cell treatments are a desirable therapeutic option to regenerate myocardium and improve cardiac function after myocardial infarction. Several different types of cells have been explored, each with their own benefits and limitations. Induced pluripotent stem cells possess an embryonic-like state and therefore have a high proliferative capacity, but they also pose a risk of teratoma formation. Mesenchymal stem cells have been investigated from both bone marrow and adipose tissue. Their immunomodulatory characteristics may permit the use of allogeneic cells as universal donor cells in the future. Lastly, studies have consistently shown that cardiac stem cells are better able to express markers of cardiogenesis compared to other cell types, as well improve cardiac function. The ideal source of stem cells depends on multiple factors such as the ease of extraction/isolation, effectiveness of engraftment, ability to differentiate into cardiac lineages and effect on cardiac function. Although multiple studies highlight the benefits and limitations of each cell type and reinforce the successful potential use of these cells to regenerate damaged myocardium, more studies are needed to directly compare cells from various sources. It is interesting to note that research using stem cell therapies is also expanding to treat other cardiovascular diseases including non-ischemic cardiomyopathies.

Allogeneic Mesenchymal Stromal Cells Overexpressing Mutant Human Hypoxia-Inducible Factor 1-α (HIF1-α) in an Ovine Model of Acute Myocardial Infarction

Background

Bone marrow mesenchymal stromal cells (BMMSCs) are cardioprotective in acute myocardial infarction (AMI) because of release of paracrine angiogenic and prosurvival factors. Hypoxia‐inducible factor 1‐α (HIF1‐α), rapidly degraded during normoxia, is stabilized during ischemia and upregulates various cardioprotective genes. We hypothesized that BMMSCs engineered to overexpress mutant, oxygen‐resistant HIF1‐α would confer greater cardioprotection than nontransfected BMMSCs in sheep with AMI.

Methods and Results

Allogeneic BMMSCs transfected with a minicircle vector encoding mutant HIF1‐α (BMMSC‐HIF) were injected in the peri‐infarct of sheep (n=6) undergoing coronary occlusion. Over 2 months, infarct volume measured by cardiac magnetic resonance (CMR) imaging decreased by 71.7±1.3% (P<0.001), and left ventricular (LV) percent ejection fraction (%EF) increased near 2‐fold (P<0.001) in the presence of markedly decreased end‐systolic volume. Sheep receiving nontransfected BMMSCs (BMMSC; n=6) displayed less infarct size limitation and percent LVEF improvement, whereas in placebo‐treated animals (n=6), neither parameters changed over time. HIF1‐α‐transfected BMMSCs (BMMSC‐HIF) induced angio‐/arteriogenesis and decreased apoptosis by HIF1‐mediated overexpression of erythropoietin, inducible nitrous oxide synthase, vascular endothelial growth factor, and angiopoietin‐1. Cell tracking using paramagnetic iron nanoparticles in 12 additional sheep revealed enhanced long‐term retention of BMMSC‐HIF.

Conclusions

Intramyocardial delivery of BMMSC‐HIF reduced infarct size and improved LV systolic performance compared to BMMSC, attributed to increased neovascularization and cardioprotective effects induced by HIF1‐mediated overexpression of paracrine factors and enhanced retention of injected cells. Given the safety of the minicircle vector and the feasibility of BMMSCs for allogeneic application, this treatment may be potentially useful in the clinic.

Vascular stem cells-potential for clinical application

INTRODUCTION

Cell therapy is a growing area of research as an alternative to pharmaceuticals or surgery for the treatment of ischaemic disease. Studies are focusing on delivering tissue-derived cells into damaged organs to promote vascular regeneration or gain of function.

SOURCES OF DATA

Pubmed, clinicaltrials.gov, BHF website.

AREAS OF AGREEMENT

Stem cells have the potential to become a viable treatment for many diseases, as indicated by the numerous pre-clinical studies demonstrating therapeutic benefit.

AREAS OF CONTROVERSY

The mechanisms of action for transplanted stem cells are still open to debate. Proposed mechanism includes direct cell incorporation and paracrine action. Additionally, the secretome produced by transplanted cells remains largely unknown.

GROWING POINTS

Initial studies focused on delivering stem cells by injection; however, current research is utilizing biomaterials to target cell delivery to specific areas.

AREAS TIMELY FOR DEVELOPING RESEARCH

Whilst stem cell research in the laboratory is expanding rapidly, transition into clinical studies is hindered by the availability of equivalent clinical grade reagents.

Widespread Myocardial Delivery of Heart-Derived Stem Cells by Nonocclusive Triple-Vessel Intracoronary Infusion in Porcine Ischemic Cardiomyopathy: Superior Attenuation of Adverse Remodeling Documented by Magnetic Resonance Imaging and Histology

Single-vessel, intracoronary infusion of stem cells under stop-flow conditions has proven safe but achieves only limited myocardial coverage. Continuous flow intracoronary delivery to one or more coronary vessels may achieve broader coverage for treating cardiomyopathy, but has not been investigated. Using nonocclusive coronary guiding catheters, we infused allogeneic cardiosphere-derived cells (CDCs) either in a single vessel or sequentially in all three coronary arteries in porcine ischemic cardiomyopathy and used magnetic resonance imaging (MRI) to assess structural and physiological outcomes. Vehicle-infused animals served as controls. Single-vessel stop-flow and continuous-flow intracoronary infusion revealed equivalent effects on scar size and function. Sequential infusion into each of the three major coronary vessels under stop-flow or continuous-flow conditions revealed equal efficacy, but less elevation of necrotic biomarkers with continuous-flow delivery. In addition, multi-vessel delivery resulted in enhanced global and regional tissue function compared to a triple-vessel placebo-treated group. The functional benefits after global cell infusion were accompanied histologically by minimal inflammatory cellular infiltration, attenuated regional fibrosis and enhanced vessel density in the heart. Sequential multi-vessel non-occlusive delivery of CDCs is safe and provides enhanced preservation of left ventricular function and structure. The current findings provide preclinical validation of the delivery method currently undergoing clinical testing in the Dilated cardiomYopathy iNtervention With Allogeneic MyocardIally-regenerative Cells (DYNAMIC) trial of CDCs in heart failure patients.

Immunotolerant Properties of Mesenchymal Stem Cells: Updated Review

Stem cell transplantation is a potential therapeutic option to regenerate damaged myocardium and restore function after infarct. Current research is focused on the use of allogeneic mesenchymal stem cells (MSCs) due to their unique immunomodulatory characteristics and ability to be harvested from young and healthy donors. Both animal and human studies support the immunoprivileged state of MSCs and even demonstrate improvements in cardiac function after transplantation. This research continues to be a topic of interest, as advances will ultimately enable the clinical use of these universal cells for therapy after a myocardial infarction. Updated in vitro, in vivo, and clinical trial studies are discussed in detail in the following review.

Translational research of adult stem cell therapy

Congestive heart failure (CHF) secondary to chronic coronary artery disease is a major cause of morbidity and mortality world-wide. Its prevalence is increasing despite advances in medical and device therapies. Cell based therapies generating new cardiomyocytes and vessels have emerged as a promising treatment to reverse functional deterioration and prevent the progression to CHF. Functional efficacy of progenitor cells isolated from the bone marrow and the heart have been evaluated in preclinical large animal models. Furthermore, several clinical trials using autologous and allogeneic stem cells and progenitor cells have demonstrated their safety in humans yet their clinical relevance is inconclusive. This review will discuss the clinical therapeutic applications of three specific adult stem cells that have shown particularly promising regenerative effects in preclinical studies, bone marrow derived mesenchymal stem cell, heart derived cardiosphere-derived cell and cardiac stem cell. We will also discuss future therapeutic approaches.

Myocardial infarction: stem cell transplantation for cardiac regeneration

It is estimated that by 2030, almost 23.6 million people will perish from cardiovascular disease, according to the WHO. The review discusses advances in stem cell therapy for myocardial infarction, including cell sources, methods of differentiation, expansion selection and their route of delivery. Skeletal muscle cells, hematopoietic cells and mesenchymal stem cells (MSCs) and embryonic stem cells (ESCs)-derived cardiomyocytes have advanced to the clinical stage, while induced pluripotent cells (iPSCs) are yet to be considered clinically. Delivery of cells to the sites of injury and their subsequent retention is a major issue. The development of supportive scaffold matrices to facilitate stem cell retention and differentiation are analyzed. The review outlines clinical translation of conjugate stem cell-based cellular therapeutics post-myocardial infarction.

Mesenchymal Stem Cells Reduce Murine Atherosclerosis Development

Mesenchymal stem cells (MSCs) have regenerative properties, but recently they were also found to have immunomodulatory capacities. We therefore investigated whether MSCs could reduce atherosclerosis, which is determined by dyslipidaemia and chronic inflammation. We adoptively transferred MSCs into low-density lipoprotein-receptor knockout mice and put these on a Western-type diet to induce atherosclerosis. Initially after treatment, we found higher levels of circulating regulatory T cells. In the long-term, overall numbers of effector T cells were reduced by MSC treatment. Moreover, MSC-treated mice displayed a significant 33% reduction in circulating monocytes and a 77% reduction of serum CCL2 levels. Most strikingly, we found a previously unappreciated effect on lipid metabolism. Serum cholesterol was reduced by 33%, due to reduced very low-density lipoprotein levels, likely a result of reduced de novo hepatic lipogenesis as determined by a reduced expression of Stearoyl-CoA desaturase-1 and lipoprotein lipase. MSCs significantly affected lesion development, which was reduced by 33% in the aortic root. These lesions contained 56% less macrophages and showed a 61% reduction in T cell numbers. We show here for the first time that MSC treatment affects not only inflammatory responses but also significantly reduces dyslipidaemia in mice. This makes MSCs a potent candidate for atherosclerosis therapies.

Translational failure of anti-inflammatory compounds for myocardial infarction: a meta-analysis of large animal models

AIMS

Numerous anti-inflammatory drugs have been tested in large animal studies of myocardial infarction (MI). Despite positive results, translation of anti-inflammatory strategies into clinical practice has proved to be difficult. Critical disparities between preclinical and clinical study design that influence efficacy may partly be responsible for this translational failure. The aim of the present systematic review was to better understand which factors underlie the failure of transition towards the clinic.

METHODS AND RESULTS

Meta-analysis and regression of large animal studies were performed to identify sources that influenced effect size of anti-inflammatory compounds in large animal models of MI. We included 183 studies, containing 3331 large animals. Infarct size (IS) as a ratio of the area at risk (12.7%; 95% confidence interval, CI 11.1-14.4%, P < 0.001) and IS as a ratio of the left ventricle (3.9%; 95% CI 3.1-4.7%, P < 0.001) were reduced in treatment compared with control groups. Effect size was higher when outcome was assessed early after MI (P = 0.013) and where studies included only male animals (P < 0.001). Mortality in treated animals was higher in studies that blinded the investigator during the experiment (P = 0.041) and depended on the type of drug used (P < 0.001).

CONCLUSIONS

As expected, treatment with anti-inflammatory drugs leads to smaller infarct size in large animal MI models. Timing of outcome assessment, sex, and study quality are significantly associated with outcome and may explain part of the translational failure in clinical settings. Effect size depends on the type of drug used, enabling identification of compounds for future clinical testing.

Intracoronary Delivery of Human Mesenchymal/Stromal Stem Cells: Insights from Coronary Microcirculation Invasive Assessment in a Swine Model

BACKGROUND

Mesenchymal stem/stromal cells have unique properties favorable to their use in clinical practice and have been studied for cardiac repair. However, these cells are larger than coronary microvessels and there is controversy about the risk of embolization and microinfarctions, which could jeopardize the safety and efficacy of intracoronary route for their delivery. The index of microcirculatory resistance (IMR) is an invasive method for quantitatively assessing the coronary microcirculation status.

OBJECTIVES

To examine heart microcirculation after intracoronary injection of mesenchymal stem/stromal cells with the index of microcirculatory resistance.

METHODS

Healthy swine were randomized to receive by intracoronary route either 30x106 MSC or the same solution with no cells (1% human albumin/PBS) (placebo). Blinded operators took coronary pressure and flow measurements, prior to intracoronary infusion and at 5 and 30 minutes post-delivery. Coronary flow reserve (CFR) and the IMR were compared between groups.

RESULTS

CFR and IMR were done with a variance within the 3 transit time measurements of 6% at rest and 11% at maximal hyperemia. After intracoronary infusion there were no significant differences in CFR. The IMR was significantly higher in MSC-injected animals (at 30 minutes, 14.2U vs. 8.8U, p = 0.02) and intragroup analysis showed a significant increase of 112% from baseline to 30 minutes after cell infusion, although no electrocardiographic changes or clinical deterioration were noted.

CONCLUSION

Overall, this study provides definitive evidence of microcirculatory disruption upon intracoronary administration of mesenchymal stem/stromal cells, in a large animal model closely resembling human cardiac physiology, function and anatomy.

Intracoronary Delivery of Human Mesenchymal/Stromal Stem Cells: Insights from Coronary Microcirculation Invasive Assessment in a Swine Model

BACKGROUND

Mesenchymal stem/stromal cells have unique properties favorable to their use in clinical practice and have been studied for cardiac repair. However, these cells are larger than coronary microvessels and there is controversy about the risk of embolization and microinfarctions, which could jeopardize the safety and efficacy of intracoronary route for their delivery. The index of microcirculatory resistance (IMR) is an invasive method for quantitatively assessing the coronary microcirculation status.

OBJECTIVES

To examine heart microcirculation after intracoronary injection of mesenchymal stem/stromal cells with the index of microcirculatory resistance.

METHODS

Healthy swine were randomized to receive by intracoronary route either 30x106 MSC or the same solution with no cells (1% human albumin/PBS) (placebo). Blinded operators took coronary pressure and flow measurements, prior to intracoronary infusion and at 5 and 30 minutes post-delivery. Coronary flow reserve (CFR) and the IMR were compared between groups.

RESULTS

CFR and IMR were done with a variance within the 3 transit time measurements of 6% at rest and 11% at maximal hyperemia. After intracoronary infusion there were no significant differences in CFR. The IMR was significantly higher in MSC-injected animals (at 30 minutes, 14.2U vs. 8.8U, p = 0.02) and intragroup analysis showed a significant increase of 112% from baseline to 30 minutes after cell infusion, although no electrocardiographic changes or clinical deterioration were noted.

CONCLUSION

Overall, this study provides definitive evidence of microcirculatory disruption upon intracoronary administration of mesenchymal stem/stromal cells, in a large animal model closely resembling human cardiac physiology, function and anatomy.

Bone marrow-derived mesenchymal stem cells for the treatment of heart failure

Heart failure remains a major cause of death and disability, requiring rapid development of new therapies. Bone marrow-derived mesenchymal stem cell (MSC)-based therapy is an emerging approach for the treatment of both acute and chronic heart failure. Following successful experimental studies in a range of models, more than 40 clinical trials of MSC-based therapy for heart failure have now been registered, and the results of completed clinical trials so far have shown feasibility and safety of this approach with therapeutic potential suggested (though preliminarily). However, there appear to be several critical issues to be solved before this treatment could become a widespread standard therapy for heart failure. In this review, we comprehensively and systemically summarize a total of 73 preclinical studies and 11 clinical trial reports published to date. By analyzing the data in these reports, (1) improvement in the cell delivery method to the heart in order to enhance donor cell engraftment, (2) elucidation of mechanisms underpinning the therapeutic effects of the treatment differentiation and/or treatment secretion, and (3) validation of the utility of allogeneic MSCs which could enhance the efficacy and expand the application/indication of this therapeutic approach are highlighted as future perspectives. These important respects are further discussed in this review article with referencing latest scientific and clinical information.

Myocardial regeneration strategy using Wharton's jelly mesenchymal stem cells as an off-the-shelf 'unlimited' therapeutic agent: results from the Acute Myocardial Infarction First-in-Man Study

INTRODUCTION

In large-animal acute myocardial infarction (AMI) models, Wharton's jelly (umbilical cord matrix) mesenchymal stem cells (WJMSCs) effectively promote angiogenesis and drive functional myocardial regeneration. Human data are lacking.

AIM

To evaluate the feasibility and safety of a novel myocardial regeneration strategy using human WJMSCs as a unique, allogenic but immuno-privileged, off-the-shelf cellular therapeutic agent.

MATERIAL AND METHODS

The inclusion criterion was first, large (LVEF ≤ 45%, CK-MB > 100 U/l) AMI with successful infarct-related artery primary percutaneous coronary intervention reperfusion (TIMI ≥ 2). Ten consecutive patients (age 32-65 years, peak hs-troponin T 17.3 ±9.1 ng/ml and peak CK-MB 533 ±89 U/l, sustained echo LVEF reduction to 37.6 ±2.6%, cMRI LVEF 40.3 ±2.7% and infarct size 20.1 ±2.8%) were enrolled.

RESULTS

30 × 10(6) WJMSCs were administered (LAD/Cx/RCA in 6/3/1) per protocol at ≈ 5-7 days using a cell delivery-dedicated, coronary-non-occlusive method. No clinical symptoms or ECG signs of myocardial ischemia occurred. There was no epicardial flow or myocardial perfusion impairment (TIMI-3 in all; cTFC 45 ±8 vs. 44 ±9, p = 0.51), and no patient showed hs-troponin T elevation (0.92 ±0.29 ≤ 24 h before vs. 0.89 ±0.28 ≤ 24 h after; decrease, p = 0.04). One subject experienced, 2 days after cell transfer, a transient temperature rise (38.9°C); this was reactive to paracetamol with no sequel. No other adverse events and no significant arrhythmias (ECG Holter) occurred. Up to 12 months there was one new, non-index territory lethal AMI but no adverse events that might be attributable to WJMSC treatment.

CONCLUSIONS

This study demonstrated the feasibility and procedural safety of WJMSC use as off-the-shelf cellular therapy in human AMI and suggested further clinical safety of WJMSC cardiac transfer, providing a basis for randomized placebo-controlled endpoint-powered evaluation.

Use of mesenchymal stem cells for therapy of cardiac disease

Despite substantial clinical advances over the past 65 years, cardiovascular disease remains the leading cause of death in America. The past 15 years has witnessed major basic and translational interest in the use of stem and precursor cells as a therapeutic agent for chronically injured organs. Among the cell types under investigation, adult mesenchymal stem cells are widely studied, and in early stage, clinical studies show promise for repair and regeneration of cardiac tissues. The ability of mesenchymal stem cells to differentiate into mesoderm- and nonmesoderm-derived tissues, their immunomodulatory effects, their availability, and their key role in maintaining and replenishing endogenous stem cell niches have rendered them one of the most heavily investigated and clinically tested type of stem cell. Accumulating data from preclinical and early phase clinical trials document their safety when delivered as either autologous or allogeneic forms in a range of cardiovascular diseases, but also importantly define parameters of clinical efficacy that justify further investigation in larger clinical trials. Here, we review the biology of mesenchymal stem cells, their interaction with endogenous molecular and cellular pathways, and their modulation of immune responses. Additionally, we discuss factors that enhance their proliferative and regenerative ability and factors that may hinder their effectiveness in the clinical setting.