Autologous bone marrow-derived stem-cell transfer in patients with ST-segment elevation myocardial infarction: double-blind, randomised controlled trial

Clinical Studies of Cell Therapy in Cardiovascular Medicine: Recent Developments and Future Directions

Given the rising prevalence of cardiovascular disease worldwide and the limited therapeutic options for severe heart failure, novel technologies that harness the regenerative capacity of the heart are sorely needed. The therapeutic use of stem cells has the potential to reverse myocardial injury and improve cardiac function, in contrast to most current medical therapies that only mitigate heart failure symptoms. Nearly 2 decades and >200 trials for cardiovascular disease have revealed that most cell types are safe; however, their efficacy remains controversial, limiting the transition of this therapy from investigation to practice. Lessons learned from these initial studies are driving the design of new clinical trials; higher fidelity of cell isolation techniques, standardization of conditions, more consistent use of state of the art measurement techniques, and assessment of multiple end points to garner insights into the efficacy of stem cells. Translation to clinical trials has almost outpaced our mechanistic understanding, and individual patient factors likely play a large role in stem cell efficacy. Therefore, careful analysis of dosing, delivery methods, and the ideal patient populations is necessary to translate cell therapy from research to practice. We are at a pivotal stage in the field in which information from many relatively small clinical trials must guide carefully executed efficacy trials. Larger efficacy trials are being launched to answer questions about older, first-generation stem cell therapeutics, while novel, second-generation products are being introduced into the clinical realm. This review critically examines the current state of clinical research on cell-based therapies for cardiovascular disease, highlighting the controversies in the field, improvements in clinical trial design, and the application of exciting new cell products.

Stem cell activity in the repair of cardiovascular tissues

Stem cells can become different types of cells and have the potential to divide and self-renew. There are two types of stem cells, first the embryonic stem cells and second the adult stem cells, both help in regeneration or repair tissues of an organism, for this reason, the stem cells are being used to renew the world of medicine. Stem cells are obtained from three sources: the first can be our own body that where certain organs still have some cells still not completely differentiated. The second source is the embryos when they are in the blastocyst phase (between five to fourteen days from conception), and the third source can be in the cells of the skin, liver or another cell type that have been modified to behave like embryonic stem cells. With this therapy, we would find ourselves before an inexhaustible source to repair the tissues and organs that were damaged in our bodies. One of the main causes of mortality in heart failure, but with the help of cell therapy has been studied the repair of cardiac tissue with the stem cell transplant. The objective of the cellular transplantation is that the transplanted cells in the heart tissue manage to regenerate, renewed, and repair any part of the heart tissue damaged.

Adenosine stress perfusion cardiac magnetic resonance imaging in patients undergoing intracoronary bone marrow cell transfer after ST-elevation myocardial infarction: the BOOST-2 perfusion substudy

AIMS

In the placebo-controlled, double-blind BOne marrOw transfer to enhance ST-elevation infarct regeneration (BOOST) 2 trial, intracoronary autologous bone marrow cell (BMC) transfer did not improve recovery of left ventricular ejection fraction (LVEF) at 6 months in patients with ST-elevation myocardial infarction (STEMI) and moderately reduced LVEF. Regional myocardial perfusion as determined by adenosine stress perfusion cardiac magnetic resonance imaging (S-CMR) may be more sensitive than global LVEF in detecting BMC treatment effects. Here, we sought to evaluate (i) the changes of myocardial perfusion in the infarct area over time (ii) the effects of BMC therapy on infarct perfusion, and (iii) the relation of infarct perfusion to LVEF recovery at 6 months.

METHODS AND RESULTS

In 51 patients from BOOST-2 (placebo, n = 10; BMC, n = 41), S-CMR was performed 5.1 ± 2.9 days after PCI (before placebo/BMC treatment) and after 6 months. Infarct perfusion improved from baseline to 6 months in the overall patient cohort as reflected by the semi-quantitative parameters, perfusion defect-infarct size ratio (change from 0.54 ± 0.20 to 0.43 ± 0.22; P = 0.006) and perfusion defect-upslope ratio (0.54 ± 0.23 to 0.68 ± 0.22; P < 0.001), irrespective of randomised treatment. Perfusion defect-upslope ratio at baseline correlated with LVEF recovery (r = 0.62; P < 0.001) after 6 months, with a threshold of 0.54 providing the best sensitivity (79%) and specificity (74%) (area under the curve, 0.79; 95% confidence interval, 0.67-0.92).

CONCLUSION

Infarct perfusion improves from baseline to 6 months and predicts LVEF recovery in STEMI patients undergoing early PCI. Intracoronary BMC therapy did not enhance infarct perfusion in the BOOST-2 trial.

Current Status of Stem Cell Therapies in Tissue Repair and Regeneration

Tissue engineering is a multi-disciplinary field such as material science, life science, and bioengineering that are necessary to make artificial tissue or rejuvenate damaged tissue. Numerous tissue repair techniques and substitute now exist even though it has several shortcomings; these shortcomings give a good reason for the continuous research for more acceptable tissue-engineered substitutes. The search for and use of a suitable stem cell in tissue engineering is a promising concept. Stem cells have a distinctive capability to differentiate and self-renew that make more suitable for cell-based therapies in tissue repair and regeneration. This review article focuses on stem cell for tissue engineering and their methods of manufacture with their application in nerve, bone, skin, cartilage, bladder, cardiac, liver tissue repair and regeneration.

Asprosin improves the survival of mesenchymal stromal cells in myocardial infarction by inhibiting apoptosis via the activated ERK1/2-SOD2 pathway

AIMS

Several adipokines have been proven to improve the therapeutic efficacy of mesenchymal stromal cells (MSCs) when used to treat ischemic heart disease. Asprosin (ASP) is a newly-discovered adipokine. ASP might also predict the severity of coronary pathology. We investigated the role of ASP on MSCs and the effects of ASP-pretreated MSCs on myocardial infarction (MI).

MAIN METHODS

MSCs were labelled with a lentivirus carrying green fluorescent protein (GFP). For in vivo study, after pretreatment with vehicle or ASP, MSCs were injected into infarcted hearts. Cardiac function and fibrosis were then evaluated 4 weeks after the induction of MI and survival of MSCs evaluated after 1 week. MSCs proliferation and migration were investigated after ASP treatment in vitro. MSCs apoptosis induced by hydrogen peroxide (H₂O₂) was assessed using flow cytometry.

KEY FINDINGS

Compared to vehicle-pretreated MSCs, ASP-pretreated MSCs significantly improved the left ventricular ejection fraction (LVEF), and inhibited myocardial fibrosis 4 weeks after MI. ASP pretreatment may have promoted homing of transplanted MSCs. In vitro results showed that ASP had no significant effect on MSC proliferation and migration, but protected these cells from H₂O₂-induced apoptosis. Among 21 molecules associated with antioxidation and cell death, the antioxidant enzyme SOD2 was significantly upregulated by ASP. Furthermore, ASP treatment inhibited H₂O₂-induced ROS generation and apoptosis via the activated ERK1/2-SOD2 pathway.

SIGNIFICANCE

This is the first evidence that ASP can regulate MSCs function and enhance MSCs therapy for ischemic heart disease. Furthermore, we demonstrate that ASP protects MSCs from oxidative stress-induced apoptosis via the ERK1/2-SOD2 pathway.

Local pharmacological induction of angiogenesis: Drugs for cells and cells as drugs

The past decades have seen significant advances in pro-angiogenic strategies based on delivery of molecules and cells for conditions such as coronary artery disease, critical limb ischemia and stroke. Currently, three major strategies are evolving. Firstly, various pharmacological agents (growth factors, interleukins, small molecules, DNA/RNA) are locally applied at the ischemic region. Secondly, preparations of living cells with considerable bandwidth of tissue origin, differentiation state and preconditioning are delivered locally, rarely systemically. Thirdly, based on the notion, that cellular effects can be attributed mostly to factors secreted in situ, the cellular secretome (conditioned media, exosomes) has come into the spotlight. We review these three strategies to achieve (neo)angiogenesis in ischemic tissue with focus on the angiogenic mechanisms they tackle, such as transcription cascades, specific signalling steps and cellular gases. We also include cancer-therapy relevant lymphangiogenesis, and shall seek to explain why there are often conflicting data between in vitro and in vivo. The lion's share of data encompassing all three approaches comes from experimental animal work and we shall highlight common technical obstacles in the delivery of therapeutic molecules, cells, and secretome. This plethora of preclinical data contrasts with a dearth of clinical studies. A lack of adequate delivery vehicles and standardised assessment of clinical outcomes might play a role here, as well as regulatory, IP, and manufacturing constraints of candidate compounds; in addition, completed clinical trials have yet to reveal a successful and efficacious strategy. As the biology of angiogenesis is understood well enough for clinical purposes, it will be a matter of time to achieve success for well-stratified patients, and most probably with a combination of compounds.

Bone-derived Nestin-positive mesenchymal stem cells improve cardiac function via recruiting cardiac endothelial cells after myocardial infarction

BACKGROUND

Bone-derived mesenchymal stem cell (BMSC) transplantation has been reported to be effective for the treatment of ischemic heart disease, but whether BMSCs are the optimal cell type remains under debate. Increasing numbers of studies have shown that Nestin, an intermediate filament protein, is a potential marker for MSCs, which raises the question of whether Nestin⁺ cells in BMSCs may play a more crucial role in myocardial repair.

METHODS

Nestin⁺ cells were isolated using flow cytometry by gating for CD45^- Ter119^- CD31^- cells from the compact bone of Nestin-GFP transgenic mice, expressing GFP driven by the Nestin promoter. Colony-forming and proliferative curve assays were conducted to determine the proliferative capacity of these cells, while qRT-PCR was used to analyze the mRNA levels of relative chemokines and growth factors. Cardiac endothelial cell (CEC) recruitment was assessed via a transwell assay. Moreover, permanent ligation of the left anterior descending (LAD) coronary artery was performed to establish an acute myocardial infarction (AMI) mouse model. After cell transplantation, conventional echocardiography was conducted 1 and 4 weeks post-MI, and hearts were harvested for hematoxylin-and-eosin (HE) staining and immunofluorescence staining 1 week post-MI. Further evaluation of paracrine factor levels and administration of a neutralizing antibody (TIMP-1, TIMP-2, and CXCL12) or a CXCR4 antagonist (AMD3100) in MI hearts were performed to elucidate the mechanism involved in the chemotactic effect of Nestin⁺ BMSCs in vivo.

RESULTS

Compared with Nestin^- BMSCs, a greater proliferative capacity of Nestin⁺ BMSCs was observed, which further exhibited moderately high expression of chemokines instead of growth factors. More CEC recruitment in the Nestin⁺ BMSC-cocultured group was observed in vitro, while this effect was obviously abolished after treatment with neutralizing antibodies against TIMP-1, TIMP-2, or CXCL12, and more importantly, blocking the CXCL12/CXCR4 axis with a AMD3100 significantly reduced the chemotactic effect of Nestin⁺ BMSCs. After transplantation into mice exposed to myocardial infarction (MI), Nestin⁺ BMSC-treated mice showed significantly improved survival and left ventricular function compared with Nestin^- BMSC-treated mice. Moreover, endogenous CECs were markedly increased, and chemokine levels were significantly higher, in the infarcted border zone with Nestin⁺ BMSC treatment. Meanwhile, neutralization of each TIMP-1, TIMP-2, or CXCL12 in vivo could reduce the left ventricular function at 1 and 4 weeks post-MI; importantly, the combined use of these three neutralizing antibodies could make a higher significance on cardiac function. Finally, blocking the CXCL12/CXCR4 axis with AMD3100 significantly reduced the left ventricular function and greatly inhibited Nestin⁺ BMSC-induced CEC chemotaxis in vivo.

CONCLUSIONS

These results suggest that Nestin⁺ BMSC transplantation can improve cardiac function in an AMI model by recruiting resident CECs to the infarcted border region via the CXCL12/CXCR4 chemokine pathway. And we demonstrated that Nestin⁺BMSC-secreted TIMP-1/2 enhances CXCL12(SDF1α)/CXCR4 axis-driven migration of endogenous Sca-1⁺ endothelial cells in ischemic heart post-AMI. Taken together, our results show that Nestin is a useful marker for the identification of functional BMSCs and indicate that Nestin⁺ BMSCs could be a better therapeutic candidate for cardiac repair.

Prolonged elevated levels of c-kit+ progenitor cells after a myocardial infarction by beta 2 adrenergic receptor priming

Endogenous progenitor cells may participate in cardiac repair after a myocardial infarction (MI). The beta 2 adrenergic receptor (ß2-AR) pathway induces proliferation of c-kit+ cardiac progenitor cells (CPC) in vitro. We investigated if ß2-AR pharmacological stimulation could ameliorate endogenous CPC-mediated regeneration after a MI. C-kit+ CPC ß1-AR and ß2-AR expression was evaluated in vivo and in vitro. A significant increase in the percentage of CPCs expressing ß1-AR and ß2-AR was measured 7 days post-MI. Accordingly, 24 hrs of low serum and hypoxia in vitro significantly increased CPC ß2-AR expression. Cell viability and differentiation assays validated a functional role of CPC ß2-AR. The effect of pharmacological activation of ß2-AR was studied in C57 mice using fenoterol administered in the drinking water 1 week before MI or sham surgery or at the time of the surgery. MI induced a significant increase in the percentage of c-kit+ progenitor cells at 7 days, whereas pretreatment with fenoterol prolonged this response resulting in a significant elevated number of CPC up to 21 days post-MI. This increased number of CPC correlated with a decrease in infarct size. The immunofluorescence analysis of the heart tissue for proliferation, apoptosis, macrophage infiltration, cardiomyocytes surface area, and vessel density showed significant changes on the basis of surgery but no benefit due to fenoterol treatment. Cardiac function was not ameliorated by fenoterol administration when evaluated by echocardiography. Our results suggest that ß2-AR stimulation may improve the cardiac repair process by supporting an endogenous progenitor cell response but is not sufficient to improve the cardiac function.

Regenerative Cardiovascular Therapies: Stem Cells and Beyond

Although reperfusion therapy has improved outcomes, acute myocardial infarction (AMI) is still associated with both significant mortality and morbidity. Once irreversible myocardial cell death due to ischemia and reperfusion sets in, scarring leads to reduction in left ventricular function and subsequent heart failure. Regenerative cardiovascular medicine experienced a boost in the early 2000s when regenerative effects of bone marrow stem cells in a murine model of AMI were described. Translation from an animal model to stem cell application in a clinical setting was rapid and the first large trials in humans suffering from AMI were conducted. However, high initial hopes were early shattered by inconsistent results of randomized clinical trials in patients suffering from AMI treated with stem cells. Hence, we provide an overview of both basic science and clinical trials carried out in regenerative cardiovascular therapies. Possible pitfalls in specific cell processing techniques and trial design are discussed as these factors influence both basic science and clinical outcomes. We address possible solutions. Alternative mechanisms and explanations for effects seen in both basic science and some clinical trials are discussed here, with special emphasis on paracrine mechanisms via growth factors, exosomes, and microRNAs. Based on these findings, we propose an outlook in which stem cell therapy, or therapeutic effects associated with stem cell therapy, such as paracrine mechanisms, might play an important role in the future. Optimizing stem cell processing and a better understanding of paracrine signaling as well as its effect on cardioprotection and remodeling after AMI might improve not only AMI research, but also our patients' outcomes.

Regenerating the field of cardiovascular cell therapy

The retraction of >30 falsified studies by Anversa et al. has had a disheartening impact on the cardiac cell therapeutics field. The premise of heart muscle regeneration by the transdifferentiation of bone marrow cells or putative adult resident cardiac progenitors has been largely disproven. Over the past 18 years, a generation of physicians and scientists has lost years chasing these studies, and patients have been placed at risk with little scientific grounding. Funding agencies invested hundreds of millions of dollars in irreproducible work, and both academic institutions and the scientific community ignored troubling signals over a decade of questionable work. Our collective retrospective analysis identifies preventable problems at the level of the editorial and peer-review process, funding agencies and academic institutions. This Perspective provides a chronology of the forces that led to this scientific debacle, integrating direct knowledge of the process. We suggest a science-driven path forward that includes multiple novel approaches to the problem of heart muscle regeneration.

Improvement in Left Ventricular Function with Intracoronary Mesenchymal Stem Cell Therapy in a Patient with Anterior Wall ST-Segment Elevation Myocardial Infarction

Background/Aims

The progression and development of congestive heart failure is still considered a large problem despite the existence of revascularization therapies and optimal, state-of-the-art medical services. An acute myocardial infarction (AMI) is a major cause of congestive heart failure, so researchers are investigating techniques to complement primary percutaneous coronary intervention (PCI) or thrombolytic therapy to prevent congestive heart failure after AMI.

Methods

Twenty-six patients with successful PCI for acute ST-segment elevation anterior wall myocardial infarction were assigned to either a control group (n = 12) or a bone marrow mesenchymal stem cells (BM-MSC) group (n = 14). The control group received optimum post-infarction treatment, and the BMSC group received intracoronary delivery of autologous BMSC at 1 month after PCI with the optimum medical treatment. The primary endpoint was a left ventricular ejection fraction (LVEF) change from baseline to 4-month follow-up, as determined via myocardial single-photon emission computed tomography (SPECT).

Results

The global LVEF at baseline (determined 3.5 ± 1.5 days after PCI) was 35.4 ± 3.0% in the control group and 33.6 ± 4.7% in the BM-MSC group. BMSC transfer enhanced left ventricular systolic function primarily in anterior wall myocardial segments adjacent to the LAD infarcted area. Four months later, via SPECT, global LVEF had increased by 4.8 ± 1.9% in the control group and 8.8 ± 2.9% in the BM-MSC group (p = 0.031). The cell transfer did not increase the risk of adverse clinical events, in-stent restenosis, or proarrhythmic effects. The echocardiographic evaluation also revealed a significant increase in the LVEF value from baseline to the 4-month (9.0 ± 4.7 and 5.3 ± 2.6%, p = 0.023) and 12-month (9.9 ± 5.2% and 6.5 ± 2.7%, p = 0.048) follow-up in the BM-MSC group but not in the control group.

Conclusions

Intracoronary administration of autologous BM-MSC was tolerable and safe with significant improvement in LVEF at 4-month (SPECT and echocardiography result) and 12-month (echocardiography result only) follow-up in patients with anterior AMI.

Repeated cell transplantation and adjunct renal denervation in ischemic heart failure: exploring modalities for improving cell therapy efficacy

Enthusiasm for cell therapy for myocardial injury has waned due to equivocal benefits in clinical trials. In an attempt to improve efficacy, we investigated repeated cell therapy and adjunct renal denervation (RDN) as strategies for augmenting cardioprotection with cardiosphere-derived cells (CDCs). We hypothesized that combining CDC post-conditioning with repeated CDC doses or delayed RDN therapy would result in superior function and remodeling. Wistar-Kyoto (WKY) rats or spontaneously hypertensive rats (SHR) were subjected to 45 min of coronary artery ligation followed by reperfusion for 12-14 weeks. In the first study arm, SHR were treated with CDCs (0.5 × 10⁶ i.c.) or PBS 20 min following reperfusion, or additionally treated with CDCs (1.0 × 10⁶ i.v.) at 2, 4, and 8 weeks. In the second arm, at 4 weeks following myocardial infarction (MI), SHR received CDCs (0.5 × 10⁶ i.c.) or CDCs + RDN. In the third arm, WKY rats were treated with i.c. CDCs administered 20 min following reperfusion and RDN or a sham at 4 weeks. Early i.c. + multiple i.v. dosing, but not single i.c. dosing, of CDCs improved long-term left ventricular (LV) function, but not remodeling. Delayed CDC + RDN therapy was not superior to single-dose delayed CDC therapy. Early CDC + delayed RDN therapy improved LV ejection fraction and remodeling compared to both CDCs alone and RDN alone. Given that both RDN and CDCs are currently in the clinic, our findings motivate further translation targeting a heart failure indication with combined approaches.

Toxicity of functionalized multi-walled carbon nanotubes on bone mesenchymal stem cell in rats

Carbon nanotubes (CNTs) are promising biomaterials in the medical field, especially in tissue engineering of bone. However, the use of CNTs is largely confined by its unfavorable solubility and toxicity. To improve solubility and biocompatibility of CNTs, functionalization has been proven to be an effective strategy. Although various functionalized CNTs have been extensively studied, only few CNTs have the desired qualities. We compared the toxicity of several promising functionalized multi-walled carbon nanotubes (MWCNTs) on rat bone-marrow derived stem cells (BMSCs). Cell experiments showed that while acid oxidation (AO)-MWCNTs and Raw-MWCNTs exhibited significant toxicity on BMSCs, polyethylene glycols (PEG)-MWCNTs and hydroxyapatit (HA)-MWCNTs had favorable biocompatibility and a trivial effect on BMSCs. Possible mechanisms for the cytotoxicity on BMSCs included mitochondrisome and deoxyribonucleic acid damage, increased oxidative stress and damaging of cellular membranes. Our data indicated that PEG-MWCNTs and HA-MWCNTs may be promising materials for bio-related applications.

Bone marrow cell therapy and cardiac reparability: better cell characterization will enhance clinical success

Nearly two decades of experimental and clinical research with bone marrow cells have paved the way for Phase III pivotal trials in larger groups of heart patients. Despite immense advancements, a multitude of factors are hampering the acceptance of bone marrow cell-based therapy for routine clinical use. These include uncertainties regarding purification and characterization of the cell preparation, delivery protocols, mechanistic understanding and study end points and their methods of assessment. Clinical data show mediocre outcomes in terms of sustained cardiac pump function. This review reasons that the modest outcomes observed in trials thus far are based on quality of the cell preparation with a focus on the chronological aging of cells when autologous cells are used for transplantation in elderly patients.

Growth arrest-specific gene 6 transfer promotes mesenchymal stem cell survival and cardiac repair under hypoxia and ischemia via enhanced autocrine signaling and paracrine action

Poor cell viability after transplantation has restricted the therapeutic capacity of mesenchymal stem cells (MSCs) for cardiac dysfunction after myocardial infarction (MI). Growth arrest-specific gene 6 (Gas6) encodes a secreted γ-carboxyglutamic acid (Gla)-containing protein that functions in cell growth, adhesion, chemotaxis, mitogenesis and cell survival. In this study, we genetically modified MSCs with Gas6 and evaluated cell survival, cardiac function, and infarct size in a rat model of MI via intramyocardial delivery. Functional studies demonstrated that Gas6 transfer significantly reduced MSC apoptosis, increased survival of MSCs in vitro and in vivo, and that Gas6-engineered MSCs (MSC^Gas6)-treated animals had smaller infarct size and showed remarkably functional recovery as compared with control MSCs (MSC^Null)-treated animals. Mechanistically, Gas6 could enhance phosphatidylinositol 3-kinase (PI3K)/Akt signaling and improve hypoxia-inducible factor-1 alpha (HIF-1α)-driven secretion of four major growth factors (VEGF, bFGF, SDF and IGF-1) in MSCs under hypoxia in an Axl-dependent autocrine manner. The paracrine action of MSC^Gas6 was further validated by coculture neonatal rat cardiomyocytes with conditioned medium from hypoxia-treated MSC^Gas6, as well as by pretreatment cardiomyocytes with the specific receptor inhibitors of VEGF, bFGF, SDF and IGF-1. Collectively, our data suggest that Gas6 may advance the efficacy of MSC therapy for post-infarcted heart failure via enhanced Gas6/Axl autocrine prosurvival signaling and paracrine cytoprotective action.

Cardiac tissue engineering: current state-of-the-art materials, cells and tissue formation

Cardiovascular diseases are the major cause of death worldwide. The heart has limited capacity of regeneration, therefore, transplantation is the only solution in some cases despite presenting many disadvantages. Tissue engineering has been considered the ideal strategy for regenerative medicine in cardiology. It is an interdisciplinary field combining many techniques that aim to maintain, regenerate or replace a tissue or organ. The main approach of cardiac tissue engineering is to create cardiac grafts, either whole heart substitutes or tissues that can be efficiently implanted in the organism, regenerating the tissue and giving rise to a fully functional heart, without causing side effects, such as immunogenicity. In this review, we systematically present and compare the techniques that have drawn the most attention in this field and that generally have focused on four important issues: the scaffold material selection, the scaffold material production, cellular selection and in vitro cell culture. Many studies used several techniques that are herein presented, including biopolymers, decellularization and bioreactors, and made significant advances, either seeking a graft or an entire bioartificial heart. However, much work remains to better understand and improve existing techniques, to develop robust, efficient and efficacious methods.

Adult Stem Cell Therapy and Heart Failure, 2000 to 2016: A Systematic Review

Importance

Stem cell therapy is a promising treatment strategy for patients with heart failure, which accounts for more than 10% of deaths in the United States annually. Despite more than a decade of research, further investigation is still needed to determine whether stem cell regenerative therapy is an effective treatment strategy and can be routinely implemented in clinical practice.

Objective

To describe the progress in cardiac stem cell regenerative therapy using adult stem cells and to highlight the merits and limitations of clinical trials performed to date.

Evidence Review

Information for this review was obtained through a search of PubMed and the Cochrane database for English-language studies published between January 1, 2000, and July 26, 2016. Twenty-nine randomized clinical trials and 7 systematic reviews and meta-analyses were included in this review.

Findings

Although adult stem cells were once believed to have the ability to create new heart tissue, preclinical studies suggest that these cells release cardioprotective paracrine factors that activate endogenous pathways, leading to myocardial repair. Subsequent randomized clinical trials, most of which used autologous bone marrow mononuclear cells, have found only a modest benefit in patients receiving stem cell therapy. The lack of a significant benefit may result from variations in trial methods, discrepancies in reporting, and an overreliance on surrogate end points.

Conclusions and Relevance

Although stem cell therapy for cardiovascular disease is not yet ready for routine clinical application, significant progress continues to be made. Physicians should be aware of the current status of this treatment so that they can better inform their patients who may be in search of alternative therapies.

Angiogenic lncRNAs: A potential therapeutic target for ischaemic heart disease

Long noncoding RNAs (LncRNAs) are involved in biological processes and the pathology of diseases and represent an important biomarker or therapeutic target for disease. Emerging evidence has suggested that lncRNAs modulate angiogenesis by regulating the angiogenic cell process-including vascular endothelial cells (VECs); stem cells, particularly bone marrow-derived stem cells, endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs); and vascular smooth muscle cells (VSMCs)-and participating in ischaemic heart disease (IHD). Therapeutic angiogenesis as an alternative therapy to promote coronary collateral circulation has been demonstrated to significantly improve the prognosis and quality of life of patients with IHD in past decades. Therefore, lncRNAs are likely to represent a novel therapeutic target for IHD through regulation of the angiogenesis process. This review summarizes the classification and functions of lncRNAs and their roles in regulating angiogenesis and in IHD, in the context of an overview of therapeutic angiogenesis in clinical trials.

Cardiosphere-Derived Cells and Ischemic Heart Failure

After a myocardial infarction, heart tissue becomes irreversibly damaged, leading to scar formation and inevitably ischemic heart failure. Of the many available interventions after a myocardial infarction, such as percutaneous intervention or pharmacological optimization, none can reverse the ischemic insult on the heart and restore cardiac function. Thus, the only available cure for patients with scarred myocardium is allogeneic heart transplantation, which comes with extensive costs, risks, and complications. However, multiple studies have shown that the heart is, in fact, not an end-stage organ and that there are endogenous mechanisms in place that have the potential to spark regeneration. Stem cell therapy has emerged as a potential tool to tap into and activate this endogenous framework. Particularly promising are stem cells derived from cardiac tissue itself, referred to as cardiosphere-derived cells (CDCs). CDCs can be extracted and isolated from the patient's myocardium and then administered by intramyocardial injection or intracoronary infusion. After early success in the animal model, multiple clinical trials have demonstrated the safety and efficacy of autologous CDC therapy in humans. Clinical trials with allogeneic CDCs showed early promising results and pose a potential "off-the-shelf" therapy for patients in the acute setting after a myocardial infarction. The mechanism responsible for CDC-induced cardiac regeneration seems to be a combination of triggering native cardiomyocyte proliferation and recruitment of endogenous progenitor cells, which most prominently occurs via paracrine effects. A further understanding of the mediators involved in paracrine signaling can help with the development of a stem cell-free therapy, with all the benefits and none of the associated complications.

New Advances in the Management of Refractory Angina Pectoris

Refractory angina is a significant clinical problem and its successful management is often extremely challenging. Defined as chronic angina-type chest pain in the presence of myocardial ischaemia that persists despite optimal medical, interventional and surgical treatment, current therapies are limited and new approaches to treatment are needed. With an ageing population and increased survival from coronary artery disease, clinicians will increasingly encounter this complex condition in routine clinical practice. Novel therapies to target myocardial ischaemia in patients with refractory angina are at the forefront of research and in this review we discuss those in clinical translation and assess the evidence behind their efficacy.

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.

Bone Marrow Mononuclear Cells Transfer for Patients after ST-Elevated Myocardial Infarction: A Meta-Analysis of Randomized Control Trials

PURPOSE

Results on the clinical utility of cell therapy for ST-elevated myocardial infarction (STEMI) are controversial. This study sought to analyze the efficacy of treatment with intracoronary bone marrow mononuclear cells (BMMC) on left ventricular (LV) function and remodeling and LV diastolic and systolic function in patients with STEMI.

MATERIALS AND METHODS

Literature search of PubMed and EMBASE databases between 2004 and 2017 was performed for randomized controlled trials in STEMI patients who underwent successful percutaneous coronary intervention and received intracoronary BMMC therapy. The defined end points were left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume (LVEDV), and left ventricular end-systolic volume (LVESV). Also, sensitivity analysis and several subgroup analyses based on follow-up duration, timing of injection, doses of cells, and imaging modalities were conducted to strengthen the statistic power of the study.

RESULTS

A total of 22 trials with 1360 patients were available for the current meta-analysis. The pooled statistics showed a significant improvement in LVEF {2.58 [95% confidence interval (CI), 1.32, 3.84]; p<0.001}, LVEDV [-3.73, (95% CI, -6.94, -0.52), p=0.02], and LVESV [?4.67, (95% CI, -7.07, -2.28), p<0.001] in the BMMC group, compared with the control group. However, in sensitivity analysis, a significant reduction in LVEDV disappeared, while the outcomes of LVEF and LVESV remained unchanged. The same results were presented in the subgroup analysis adjusting for imaging modalities and timing of cells injection.

CONCLUSION

BMMC transplantation in patients with STEMI was found to lead to improvement in LVEF, LVEDV, and LVESV parameters, indicating that cell therapy has a potential beneficial effect on LV remodeling and function.

From state-of-the-art cell therapy to endogenous cardiac repair

Clinical heart failure prevention and contemporary therapy often involve breaking the vicious cycle of global haemodynamic consequences of myocardial decay. The lack of effective regenerative therapies results in a primary focus on preventing further deterioration of cardiac performance. The cellular transplantation hypothesis has been evaluated in many different preclinical models and a handful of important clinical trials. The primary expectation that cellular transplants will be embedded into failing myocardium and fuse with existing functioning cells appears unlikely. A multitude of cellular formulas, access routes and clinical surrogate endpoints for evaluation add to the complexity of cellular therapies. Several recent large clinical trials have provided insights into both the regenerative potential and clinical improvement from non-regenerative mechanisms. Initiating endogenous repair seems to be another meaningful alternative to recover structural integrity in myocardial injury. This option may be achieved using a transcoronary sinus catheter intervention, implying the understanding of basic principles in biology. With intermittent reduction of outflow in cardiac veins (PICSO), vascular cells appear to be activated and restart a programme similar to pathways in the developing heart. Structural regeneration may be possible without requiring exogenous agents, or a combination of both approaches may become clinical reality in the next decade.

Thermo-rheological responsive microcapsules for time-dependent controlled release of human mesenchymal stromal cells

Human mesenchymal stromal cells (hMSCs) are adult-source cells that have been extensively evaluated for cell-based therapies. hMSCs delivered by intravascular injection have been reported to accumulate at the sites of injury to promote tissue repair and can also be employed as vectors for the delivery of therapeutic genes. However, the full potential of hMSCs remains limited as the cells are lost after injection due to anoikis and the adverse pathologic environment. Encapsulation of cells has been proposed as a means of increasing cell viability. However, controlling the release of therapeutic cells over time to target tissue still remains a challenge today. Here, we report the design and development of thermo-rheological responsive hydrogels that allow for precise, time dependent controlled-release of hMSCs. The encapsulated hMSCs retained good viability from 76% to 87% dependent upon the hydrogel compositions. We demonstrated the design of different blended hydrogel composites with modulated strength (S parameter) and looseness of hydrogel networks (N parameter) to control the release of hMSCs from thermo-responsive hydrogel capsules. We further showed the feasibility for controlled-release of encapsulated hMSCs within 3D matrix scaffolds. We reported for the first time by a systematic analysis that there is a direct correlation between the thermo-rheological properties associated with the degradation of the hydrogel composite and the cell release kinetics. This work therefore provides new insights into the further development of smart carrier systems for stem cell therapy.

Suppression of Pro-fibrotic Signaling Potentiates Factor-mediated Reprogramming of Mouse Embryonic Fibroblasts into Induced Cardiomyocytes

Trans-differentiation of one somatic cell type into another has enormous potential to model and treat human diseases. Previous studies have shown that mouse embryonic, dermal, and cardiac fibroblasts can be reprogrammed into functional induced-cardiomyocyte-like cells (iCMs) through overexpression of cardiogenic transcription factors including GATA4, Hand2, Mef2c, and Tbx5 both in vitro and in vivo. However, these previous studies have shown relatively low efficiency. In order to restore heart function following injury, mechanisms governing cardiac reprogramming must be elucidated to increase efficiency and maturation of iCMs. We previously demonstrated that inhibition of pro-fibrotic signaling dramatically increases reprogramming efficiency. Here, we detail methods to achieve a reprogramming efficiency of up to 60%. Furthermore, we describe several methods including flow cytometry, immunofluorescent imaging, and calcium imaging to quantify reprogramming efficiency and maturation of reprogrammed fibroblasts. Using the protocol detailed here, mechanistic studies can be undertaken to determine positive and negative regulators of cardiac reprogramming. These studies may identify signaling pathways that can be targeted to promote reprogramming efficiency and maturation, which could lead to novel cell therapies to treat human heart disease.

Randomized placebo controlled trial evaluating the safety and efficacy of single low-dose intracoronary insulin-like growth factor following percutaneous coronary intervention in acute myocardial infarction (RESUS-AMI)

BACKGROUND

Residual and significant postinfarction left ventricular (LV) dysfunction, despite technically successful percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI), remains an important clinical issue. In preclinical models, low-dose insulin-like growth factor 1 (IGF1) has potent cytoprotective and positive cardiac remodeling effects. We studied the safety and efficacy of immediate post-PCI low-dose intracoronary IGF1 infusion in STEMI patients.

METHODS

Using a double-blind, placebo-controlled, multidose study design, we randomized 47 STEMI patients with significantly reduced (≤40%) LV ejection fraction (LVEF) after successful PCI to single intracoronary infusion of placebo (n = 15), 1.5 ng IGF1 (n = 16), or 15 ng IGF1 (n = 16). All received optimal medical therapy. Safety end points were freedom from hypoglycemia, hypotension, or significant arrhythmias within 1 hour of therapy. The primary efficacy end point was LVEF, and secondary end points were LV volumes, mass, stroke volume, and infarct size at 2-month follow-up, all assessed by magnetic resonance imaging. Treatment effects were estimated by analysis of covariance adjusted for baseline (24 hours) outcome.

RESULTS

No significant differences in safety end points occurred between treatment groups out to 30 days (χ² test, P value = .77). There were no statistically significant differences in baseline (24 hours post STEMI) clinical characteristics or LVEF among groups. LVEF at 2 months, compared to baseline, increased in all groups, with no statistically significant differences related to treatment assignment. However, compared with placebo or 1.5 ng IGF1, treatment with 15 ng IGF1 was associated with a significant improvement in indexed LV end-diastolic volume (P = .018), LV mass (P = .004), and stroke volume (P = .016). Late gadolinium enhancement (±SD) at 2 months was lower in 15 ng IGF1 (34.5 ± 29.6 g) compared to placebo (49.1 ± 19.3 g) or 1.5 ng IGF1 (47.4 ± 22.4 g) treated patients, although the result was not statistically significant (P = .095).

CONCLUSIONS

In this pilot trial, low-dose IGF1, given after optimal mechanical reperfusion in STEMI, is safe but does not improve LVEF. However, there is a signal for a dose-dependent benefit on post-MI remodeling that may warrant further study.

Concise Review: The Regenerative Journey of Pericytes Toward Clinical Translation

Coronary artery disease (CAD) is the single leading cause of death worldwide. Advances in treatment and management have significantly improved patient outcomes. On the other hand, although mortality rates have decreased, more people are left with sequelae that require additional treatment and hospitalization. Moreover, patients with severe nonrevascularizable CAD remain with only the option of heart transplantation, which is limited by the shortage of suitable donors. In recent years, cell-based regenerative therapy has emerged as a possible alternative treatment, with several regenerative medicinal products already in the clinical phase of development and others emerging as competitive preclinical solutions. Recent evidence indicates that pericytes, the mural cells of blood microvessels, represent a promising therapeutic candidate. Pericytes are abundant in the human body, play an active role in angiogenesis, vessel stabilization and blood flow regulation, and possess the capacity to differentiate into multiple cells of the mesenchymal lineage. Moreover, early studies suggest a robustness to hypoxic insult, making them uniquely equipped to withstand the ischemic microenvironment. This review summarizes the rationale behind pericyte-based cell therapy and the progress that has been made toward its clinical application. We present the different sources of pericytes and the case for harvesting them from tissue leftovers of cardiovascular surgery. We also discuss the healing potential of pericytes in preclinical animal models of myocardial ischemia (MI) and current practices to upgrade the production protocol for translation to the clinic. Standardization of these procedures is of utmost importance, as lack of uniformity in cell manufacturing may influence clinical outcome. Stem Cells 2018;36:1295-1310.

Cardiomyocyte renewal in the human heart: insights from the fall-out

The capacity of the mammalian heart to regenerate cardiomyocytes has been debated over the last decades. However, limitations in existing techniques to track and identify nascent cardiomyocytes have often led to inconsistent results. Radiocarbon (14C) birth dating, in combination with other quantitative strategies, allows to establish the number and age of human cardiomyocytes, making it possible to describe their age distribution and turnover dynamics. Accurate estimates of cardiomyocyte generation in the adult heart can provide the foundation for novel regenerative strategies that aim to stimulate cardiomyocyte renewal in various cardiac pathologies.

Angiogenesis PET Tracer Uptake (68Ga-NODAGA-E[(cRGDyK)]₂) in Induced Myocardial Infarction and Stromal Cell Treatment in Minipigs

Angiogenesis is considered integral to the reparative process after ischemic injury. The α_vβ₃ integrin is a critical modulator of angiogenesis and highly expressed in activated endothelial cells. ⁶⁸Ga-NODAGA-E[(cRGDyK)]₂ (RGD) is a positron-emission-tomography (PET) ligand targeted towards α_vβ₃ integrin. The aim was to present data for the uptake of RGD and correlate it with histology and to further illustrate the differences in angiogenesis due to porcine adipose-derived mesenchymal stromal cell (pASC) or saline treatment in minipigs after induction of myocardial infarction (MI). Three minipigs were treated with direct intra-myocardial injection of pASCs and two minipigs with saline. MI was confirmed by ⁸²Rubidium (⁸²Rb) dipyridamole stress PET. Mean Standardized Uptake Values (SUV_mean) of RGD were higher in the infarct compared to non-infarct area one week and one month after MI in both pASC-treated (SUV_mean: 1.23 vs. 0.88 and 1.02 vs. 0.86, p < 0.05 for both) and non-pASC-treated minipigs (SUV_mean: 1.44 vs. 1.07 and 1.26 vs. 1.04, p < 0.05 for both). However, there was no difference in RGD uptake, ejection fractions, coronary flow reserves or capillary density in histology between the two groups. In summary, indications of angiogenesis were present in the infarcted myocardium. However, no differences between pASC-treated and non-pASC-treated minipigs could be demonstrated.

Generation of Human Pluripotent Stem Cell-derived Endothelial Cells and Their Therapeutic Utility

PURPOSE OF REVIEW

Human pluripotent stem cell-derived endothelial cells (hPSC-ECs) emerged as an important source of cells for cardiovascular regeneration. This review summarizes protocols for generating hPSC-ECs and provides an overview of the current state of the research in clinical application of hPSC-derived ECs.

RECENT FINDINGS

Various systems were developed for differentiating hPSCs into the EC lineage. Stepwise two-dimensional systems are now well established, in which various growth factors, small molecules, and coating materials are used at specific developmental stages. Moreover, studies made significant advances in clinical applicability of hPSC-ECs by removing undefined components from the differentiation system, improving the differentiation efficiency, and proving their direct vascular incorporating effects, which contrast with adult stem cells and their therapeutic effects in vivo. Finally, by using biomaterial-mediated delivery, investigators improved the survival of hPSC-ECs to more than 10 months in ischemic tissues and described long-term behavior and safety of in vivo transplanted hPSC-ECs at the histological level. hPSC-derived ECs can be as a critical source of cells for treating advanced cardiovascular diseases. Over the past two decades, substantial improvement has been made in the differentiation systems and their clinical compatibility. In the near future, establishment of fully defined differentiation systems and proof of the advantages of biomaterial-mediated cell delivery, with some additional pre-clinical studies, will move this therapy into a vital option for treating those diseases that cannot be managed by currently available therapies.

Stem Cell Therapies in Cardiovascular Disease

Despite considerable advances in medicine, cardiovascular disease is still rising, with ischemic heart disease being the leading cause of death and disability worldwide. Thus extensive efforts are continuing to establish effective therapeutic modalities that would improve both quality of life and survival in this patient population. Novel therapies are being investigated not only to protect the myocardium against ischemia-reperfusion injury but also to regenerate the heart. Stem cell therapy, such as potential use of human mesenchymal stem cells and induced pluripotent stem cells and their exosomes, will make it possible not only to address molecular mechanisms of cardiac conditioning, but also to develop new therapies for ischemic heart disease. Despite the studies and progress made over the last 15 years on the use of stem cell therapy for cardiovascular disease, the efforts are still in their infancy. Even though the expectations have been high, the findings indicate that most of the clinical trials generally have been small and the results inconclusive. Because of many negative findings, there is certain pessimism that cardiac cell therapy is likely to yield any meaningful results over the next decade or so. Similar to other new technologies, early failures are not unusual and they may be followed by impressive success. Nevertheless, there has been considerable attention to safety by the clinical investigators because the adverse events of stem cell therapy have been impressively rare. In summary, although regenerative biology might not help the cardiovascular patient in the near term, it is destined to do so over the next several decades.

Mechanisms of Cardiac Repair and Regeneration

Cardiovascular regenerative therapies are pursued on both basic and translational levels. Although efficacy and value of cell therapy for myocardial regeneration can be debated, there is a consensus that profound deficits in mechanistic understanding limit advances, optimization, and implementation. In collaboration with the TACTICS (Transnational Alliance for Regenerative Therapies in Cardiovascular Syndromes), this review overviews several pivotal aspects of biological processes impinging on cardiac maintenance, repair, and regeneration. The goal of summarizing current mechanistic understanding is to prompt innovative directions for fundamental studies delineating cellular reparative and regenerative processes. Empowering myocardial regenerative interventions, whether dependent on endogenous processes or exogenously delivered repair agents, ultimately depends on mastering mechanisms and novel strategies that take advantage of rather than being limited by inherent myocardial biology.

Impact of bone marrow mononuclear cells therapy on left ventricular function in patients with ST-elevated myocardial infarction: A meta-analysis

BACKGROUND

Bone marrow mononuclear cell (BMMNC) therapy has been used as an adjunctive treatment in patients with ST-elevated myocardial infarction (STEMI). However, the therapeutic efficacy of this approach remains controversial. The present meta-analysis is aimed to evaluate the impact of cell therapy on left ventricular function after STEMI.

METHODS

We searched through PubMed and EMBASE databases till 2017 for all relevant publications using certain search terms. Randomized controlled trials investigating the effect of BMMNC therapy in patients with STEMI who underwent percutaneous coronary intervention were selected. Wall motion score index (WMSI), infarct size, wall thickening, and myocardial perfusion were our endpoints.

RESULTS

A total of 24 trials with 1536 patients were included in our study. Overall, as observed in our data, cell therapy reduced infarct size by -2.32 (95% confidence interval [CI] -4.03, -0.62; P = .007; I = 24%) and improved myocardial perfusion by -3.04 (95% CI -3.94, -2.15; P < .001; I = 0%). However, there was no significant difference between treatment group and control group in WMSI or wall thickening.

CONCLUSION

Intracoronary BMMNC infusion is safe for patients with STEMI. It is also associated with improvement of infarct size and myocardial perfusion. Further multicenter randomized trials should be conducted to validate the therapeutic efficacy of this treatment.

Stem-cell therapy in ST-segment elevation myocardial infarction with reduced ejection fraction: A multicenter, double-blind randomized trial

BACKGROUND

Left ventricular ejection fraction (LVEF) is a major determinant of long-term prognosis after ST-segment elevation myocardial infarction (STEMI). STEMI patients with reduced LVEF have a poor prognosis, despite successful reperfusion and the use of renin-angiotensin-aldosterone inhibitors.

HYPOTHESIS

Intracoronary infusion of bone marrow-derived mononuclear cells (BMMC) may improve LVEF in STEMI patients successfully reperfused.

METHODS

The main inclusion criteria for this double-blind, randomized, multicenter study were patient age 30 to 80 years, LVEF ≤50%, successful angioplasty of infarct-related artery, and regional dysfunction in the infarct-related area analyzed before cell injection. Cardiac magnetic resonance imaging was used to assess LVEF, left ventricular volumes, and infarct size at 7 to 9 days and 6 months post-myocardial infarction.

RESULTS

One hundred and twenty-one patients were included (66 patients in the BMMC group and 55 patients in the placebo group). The primary endpoint, mean LVEF, was similar between both groups at baseline (44.63% ± 10.74% vs 42.23% ± 10.33%; P = 0.21) and at 6 months (44.74% ± 12.95 % vs 43.50 ± 12.43%; P = 0.59). The groups were also similar regarding the difference between baseline and 6 months (0.11% ± 8.5% vs 1.27% ± 8.93%; P = 0.46). Other parameters of left ventricular remodeling, such as systolic and diastolic volumes, as well as infarct size, were also similar between groups.

CONCLUSIONS

In this randomized, multicenter, double-blind trial, BMMC intracoronary infusion did not improve left ventricular remodeling or decrease infarct size.

Mechanistic effects of mesenchymal and hematopoietic stem cells: New therapeutic targets in myocardial infarction

Myocardial infarction (MI) results in dysfunction and irreversible loss of cardiomyocytes and is of the most serious health threats today. Mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) have been explored as promising cell therapy in MI and regenerative therapy. Recently, reports investigated the potential therapeutic effects of MSCs or HSCs transplantation after MI in numerous experimental and clinical studies; however, their results are controversy and needs more explorations. The current review is an attempt to clarify the therapeutic potentials of MSCs and HSCs in MI therapy, as well as their possible effects; especially the paracrine one and the exosome-derived stem cell among animal models as well as clinical trials conducted within the last 10 years. In this context, various sources of MSCs and HSCs have been addressed in helping cardiac regeneration by either revitalizing the cardiac stem cells niche or revascularizing the arteries and veins of the heart. In addition, both MSCs and HSCs could produce paracrine mediators and growth factors which led to cardiomyocytes protection, angiogenesis, immunemodulation, antioxidants, anti-apoptotic, anti-inflammatory, antifibrotic, as well as increasing cardiac contractility. Recently, microRNAs (miRNAs), post-transcriptional regulators of gene expression, and long non-coding RNA (lncRNA), a miRNA sponge, are recent stem cell-derived mediators can be promising targets of MSCs and HSCs through their paracrine effects. Although MSCs and HSCs have achieved considerable achievements, however, some challenges still remain that need to be overcome in order to establish it as a successful technique. The present review clarified the mechanistic potentials of MSCs and HSCs especially paracrine effects involved in MI including human and animal studies and the challenges challenges regarding type, differentiation, route, and number of injections.

Recent Advances in Treatment of Coronary Artery Disease: Role of Science and Technology

Coronary artery disease (CAD) is one of the most common causes of death worldwide. In the last decade, significant advancements in CAD treatment have been made. The existing treatment is medical, surgical or a combination of both depending on the extent, severity and clinical presentation of CAD. The collaboration between different science disciplines such as biotechnology and tissue engineering has led to the development of novel therapeutic strategies such as stem cells, nanotechnology, robotic surgery and other advancements (3-D printing and drugs). These treatment modalities show promising effects in managing CAD and associated conditions. Research on stem cells focuses on studying the potential for cardiac regeneration, while nanotechnology research investigates nano-drug delivery and percutaneous coronary interventions including stent modifications and coatings. This article aims to provide an update on the literature (in vitro, translational, animal and clinical) related to these novel strategies and to elucidate the rationale behind their potential treatment of CAD. Through the extensive and continued efforts of researchers and clinicians worldwide, these novel strategies hold the promise to be effective alternatives to existing treatment modalities.

Adult Stem Cells in Vascular Remodeling

Understanding the contribution of vascular cells to blood vessel remodeling is critical for the development of new therapeutic approaches to cure cardiovascular diseases (CVDs) and regenerate blood vessels. Recent findings suggest that neointimal formation and atherosclerotic lesions involve not only inflammatory cells, endothelial cells, and smooth muscle cells, but also several types of stem cells or progenitors in arterial walls and the circulation. Some of these stem cells also participate in the remodeling of vascular grafts, microvessel regeneration, and formation of fibrotic tissue around biomaterial implants. Here we review the recent findings on how adult stem cells participate in CVD development and regeneration as well as the current state of clinical trials in the field, which may lead to new approaches for cardiovascular therapies and tissue engineering.

Cardiac Regeneration with Human Pluripotent Stem Cell-Derived Cardiomyocytes

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), which are collectively called pluripotent stem cells (PSCs), have emerged as a promising source for regenerative medicine. Particularly, human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) have shown robust potential for regenerating injured heart. Over the past two decades, protocols to differentiate hPSCs into CMs at high efficiency have been developed, opening the door for clinical application. Studies further demonstrated therapeutic effects of hPSC-CMs in small and large animal models and the underlying mechanisms of cardiac repair. However, gaps remain in explanations of the therapeutic effects of engrafted hPSC-CMs. In addition, bioengineering technologies improved survival and therapeutic effects of hPSC-CMs in vivo. While most of the original concerns associated with the use of hPSCs have been addressed, several issues remain to be resolved such as immaturity of transplanted cells, lack of electrical integration leading to arrhythmogenic risk, and tumorigenicity. Cell therapy with hPSC-CMs has shown great potential for biological therapy of injured heart; however, more studies are needed to ensure the therapeutic effects, underlying mechanisms, and safety, before this technology can be applied clinically.

Stem Cell Therapy for Congenital Heart Disease: A Systematic Review

BACKGROUND

Congenital heart disease (CHD) constitutes the most prevalent and heterogeneous group of congenital anomalies. Although surgery remains the gold standard treatment modality, stem cell therapy has been gaining ground as a complimentary or alternative treatment option in certain types of CHD. The aim of this study was to present the existing published evidence and ongoing research efforts on the implementation of stem cell-based therapeutic strategies in CHD.

METHODS

A systematic review was conducted by searching Medline, ClinicalTrials.gov, and the Cochrane library, along with reference lists of the included studies through April 23, 2017.

RESULTS

Nineteen studies were included in this review (8 preclinical, 6 clinical, and 5 ongoing trials). Various routes of cardiac stem cell delivery have been reported, including intracoronary, intramyocardial, intravenous, and epicardial. Depending on their origin and level of differentiation at which they are harvested, stem cells may exhibit different properties. Preclinical studies have mostly focused on modeling right ventricle dysfunction or failure and pulmonary artery hypertension by using pressure or volume overload in vitro or in vivo. Only a limited number of clinical trials on patients with CHD exist, and these primarily focus on hypoplastic left heart syndrome. Cell-based tissue engineering has recently been introduced, and research currently is focusing on developing cell-seeded grafts and patches that could potentially grow in parallel with whole body growth once implanted in the heart.

CONCLUSIONS

It seems that stem cell delivery to the diseased heart as an adjunct to surgical palliation may provide some benefits over surgery alone in terms of cardiac function, somatic growth, and quality of life. Despite encouraging preliminary results, stem cell therapies for patients with CHD should only be considered in the setting of well-designed clinical trials. More wet laboratory research experience is needed, and translation of promising findings to large clinical studies is warranted to clearly define the efficacy and safety profile of this alternative and potentially groundbreaking therapeutic approach.

Pursuing meaningful end-points for stem cell therapy assessment in ischemic cardiac disease

Despite optimal interventional and medical therapy, ischemic heart disease is still an important cause of morbidity and mortality worldwide. Although not included in standard of care rehabilitation, stem cell therapy (SCT) could be a solution for prompting cardiac regeneration. Multiple studies have been published from the beginning of SCT until now, but overall no unanimous conclusion could be drawn in part due to the lack of appropriate end-points. In order to appreciate the impact of SCT, multiple markers from different categories should be considered: Structural, biological, functional, physiological, but also major adverse cardiac events or quality of life. Imaging end-points are among the most used - especially left ventricle ejection fraction (LVEF) measured through different methods. Other imaging parameters are infarct size, myocardial viability and perfusion. The impact of SCT on all of the aforementioned end-points is controversial and debatable. 2D-echocardiography is widely exploited, but new approaches such as tissue Doppler, strain/strain rate or 3D-echocardiography are more accurate, especially since the latter one is comparable with the MRI gold standard estimation of LVEF. Apart from the objective parameters, there are also patient-centered evaluations to reveal the benefits of SCT, such as quality of life and performance status, the most valuable from the patient point of view. Emerging parameters investigating molecular pathways such as non-coding RNAs or inflammation cytokines have a high potential as prognostic factors. Due to the disadvantages of current techniques, new imaging methods with labelled cells tracked along their lifetime seem promising, but until now only pre-clinical trials have been conducted in humans. Overall, SCT is characterized by high heterogeneity not only in preparation, administration and type of cells, but also in quantification of therapy effects.

Mesenchymal stem cell therapy: A promising cell-based therapy for treatment of myocardial infarction

For decades, mesenchymal stem (MSCs) cells have been used for cardiovascular diseases as regenerative therapy. This review is an attempt to summarize the types of MSCs involved in myocardial infarction (MI) therapy, as well as its possible mechanisms effects, especially the paracrine one in MI focusing on the studies (human and animal) conducted within the last 10 years. Recently, reports showed that MSC therapy could have infarct-limiting effects after MI in both experimental and clinical trials. In this context, various types of MSCs can help cardiac regeneration by either revitalizing the cardiac stem cells or revascularizing the arteries and veins of the heart. Furthermore, MSCs could produce paracrine growth factors that increase the survival of nearby cardiomyocytes, as well as increase angiogenesis through recruitment of stem cell from bone marrow or inducing vessel growth from existing capillaries. Recent research suggests that the paracrine effects of MSCs could be mediated by extracellular vesicles including exosomes. Exosomal microRNAs (miRNAs) released by MSCs are promising therapeutic hotspot target for MI. This could be attributed to the role of miRNA in cardiac biology, including cardiac regeneration, stem cell differentiation, apoptosis, neovascularization, cardiac contractility and cardiac remodeling. Furthermore, gene-modified MSCs could be a recent promising therapy for MI to enhance the paracrine effects of MSCs, including better homing and effective cell targeted tissue regeneration. Although MSC therapy has achieved considerable attention and progress, there are critical challenges that remains to be overcome to achieve the most effective successful cell-based therapy in MI.

NT-proBNP test with improved accuracy for the diagnosis of chronic heart failure

The circulating concentration of N-terminal pro-brain natriuretic peptide (NT-proBNP) has been shown to be a diagnostic tool for the detection of heart failure. Several factors influence NT-proBNP levels including age, sex, and body mass index (BMI). Therefore, the diagnostic sensitivity of NT-proBNP level for heart failure is relatively higher, but its specificity is low. This study aims to improve the diagnostic accuracy rate of this test by including multiple variables in the diagnostic test.The suspected chronic heart failure outpatients were divided into heart failure with reduced ejection fraction, heart failure with mid-range ejection fraction, heart failure with preserved ejection fraction, and normal heart function groups. Area under the receiver-operating characteristic (ROC) curve, cut-off value, and logistic regression analysis were used to select the model variables, sensitivity and specificity.In all, 436 subjects enrolled into this study were divided in 2 groups: model establishment (n = 300) and model validation (n = 136). In the model establishment group, the area under the curve (AUC) and cut-off value of NT-proBNP was 0.926 and 257.4 pg/mL, respectively. When age, glomerular filtration rate, BMI, atrial fibrillation, and sex were entered into the diagnosis model, AUC, sensitivity, and specificity further increased to 0.955 (95% confidence interval [CI] 0.934, 0.976), 94.2% (from 93.0%), and 86.7% (from 74.2%). The ROC curve of corrected NT-proBNP diagnostic formula for heart failure was also significantly higher (P = .037).The corrected NT-proBNP diagnostic formula was found to improve the diagnostic accuracy of chronic heart failure.

Novel molecular targets for coronary angiogenesis and ischemic heart disease

Coronary artery disease (CAD) is the number one cause of death among men and women in the USA. Genetic predisposition and environmental factors lead to the development of atherosclerotic plaques in the vessel walls of the coronary arteries, resulting in decreased myocardial perfusion. Treatment includes a combination of revascularization procedures and medical therapy. Because of the high surgical risk of many of the patients undergoing revascularization procedures, medical therapies to reduce ischemic disease are an area of active research. Small molecule, cytokine, endothelial progenitor cell, stem cell, gene, and mechanical therapies show promise in increasing the collateral growth of blood vessels, thereby reducing myocardial ischemia.

Effects of timing on intracoronary autologous bone marrow-derived cell transplantation in acute myocardial infarction: a meta-analysis of randomized controlled trials

Background

Several cell-based therapies for adjunctive treatment of acute myocardial infarction have been investigated in multiple clinical trials, but the timing of transplantation remains controversial. We conducted a meta-analysis of randomized controlled trials to investigate the effects of timing on bone marrow-derived cell (BMC) therapy in acute myocardial infarction (AMI).

Methods

A systematic literature search of PubMed, MEDLINE, and Cochrane Evidence-Based Medicine databases from January 2000 to June 2017 was performed on randomized controlled trials with at least a 3-month follow-up for patients with AMI undergoing emergency percutaneous coronary intervention (PCI) and receiving intracoronary BMC transfer thereafter. The defined end points were left ventricular (LV) ejection fraction, LV end-diastolic and end-systolic index. The data were analyzed to evaluate the effects of timing on BMC therapy.

Results

Thirty-four RCTs comprising a total of 2,307 patients were included; the results show that, compared to the control group, AMI patients who received BMC transplantation showed significantly improved cardiac function. BMC transplantation 3–7 days after PCI (+3.32%; 95% CI, 1.91 to 4.74; P < 0.00001) resulted in a significant increase of left ventricular ejection fraction (LVEF). As for the inhibitory effect on ventricular remodeling, BMC transplantation 3–7 days after PCI reduced LV end-diastolic indexes (–4.48; 95% CI, −7.98 to –0.98; P = 0.01) and LV end-systolic indexes (–6.73; 95% CI, –11.27 to –2.19; P = 0.004). However, in the groups who received BMC transplantation either within 24 hours or later than 7 days there was no significant effect on treatment outcome. In subgroup analysis, the group with LVEF ≤ 50% underwent a significant decrease in LV end-diastolic index after BMC transplantation (WMD = –3.29, 95% CI, –4.49 to –2.09; P < 0.00001); the decrease was even more remarkable in the LV end-systolic index after BMC transplantation in the group with LVEF ≤ 50% (WMD = –5.25, 95% CI, –9.30 to –1.20; P = 0.01), as well as in patients who received a dose of 10^7–10^8 cells (WMD = –12.99, 95% CI, –19.07 to –6.91; P < 0.0001). In the group with a follow-up of more than 12 months, this beneficial effect was significant and increased to a more pronounced effect of +3.58% (95% CI, 1.55 to 5.61; P = 0.0006) when compared with control.

Conclusions

In this meta-analysis, BMC transfer at 3 to 7 days post-AMI was superior to transfer within 24 hours or more than 7 days after AMI in improving LVEF and decreasing LV end-systolic dimensions or LV end-diastolic dimensions. It is more effective in patients with lower baseline LVEF (≤50%) and the effect can last more than 12 months.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0680-5) contains supplementary material, which is available to authorized users.