Challenges for heart disease stem cell therapy

Promotion of adipose stem cell transplantation using GelMA hydrogel reinforced by PLCL/ADM short nanofibers

Adipose-derived mesenchymal stem cells (ADSCs) show poor survival after transplantation, limiting their clinical application. In this study, a series of poly(l-lactide-co-ϵ-caprolactone) (PLCL)/acellular dermal matrix (ADM) nanofiber scaffolds with different proportions were prepared by electrospinning. By studying their morphology, hydrophilicity, tensile mechanics, and biocompatibility, PLCL/ADM nanofiber scaffolds with the best composition ratio (PLCL:ADM = 7:3) were selected to prepare short nanofibers. And based on this, injectable gelatin methacryloyl (GelMA) hydrogel loaded with PLCL/ADM short nanofibers (GelMA-Fibers) was constructed as a transplantation vector of ADSCs. ADSCs and GelMA-Fibers were co-cultured, and the optimal loading concentration of PLCL/ADM nanofibers was investigated by cell proliferation assay, live/dead cell staining, and cytoskeleton stainingin vitro. In vivoinvestigations were also performed by H&E staining, Oil red O staining, and TUNEL staining, and the survival and apoptosis rates of ADSCs transplantedin vivowere analyzed. It was demonstrated that GelMA-Fibers could effectively promote the proliferation of ADSCsin vitro. Most importantly, GelMA-Fibers increased the survival rate of ADSCs transplantation and decreased their apoptosis rate within 14 d. In conclusion, the constructed GelMA-Fibers would provide new ideas and options for stem cell tissue engineering and stem cell-based clinical therapies.

Administration of stem cells against cardiovascular diseases with a focus on molecular mechanisms: Current knowledge and prospects

Cardiovascular diseases (CVDs) are a serious global concern for public and human health. Despite the emergence of significant therapeutic advances, it is still the leading cause of death and disability worldwide. As a result, extensive efforts are underway to develop practical therapeutic approaches. Stem cell-based therapies could be considered a promising strategy for the treatment of CVDs. The efficacy of stem cell-based therapeutic approaches is demonstrated through recent laboratory and clinical studies due to their inherent regenerative properties, proliferative nature, and their capacity to differentiate into different cells such as cardiomyocytes. These properties could improve cardiovascular functioning leading to heart regeneration. The two most common types of stem cells with the potential to cure heart diseases are induced pluripotent stem cells (iPSCs) and mesenchymal stem cells (MSCs). Several studies have demonstrated the use, efficacy, and safety of MSC and iPSCs-based therapies for the treatment of CVDs. In this study, we explain the application of stem cells, especially iPSCs and MSCs, in the treatment of CVDs with a focus on cellular and molecular mechanisms and then discuss the advantages, disadvantages, and perspectives of using this technology in the treatment of these diseases.

Therapeutic Acellular Scaffolds for Limiting Left Ventricular Remodelling-Current Status and Future Directions

Myocardial infarction (MI) is one of the leading causes of heart-related deaths worldwide. Following MI, the hypoxic microenvironment triggers apoptosis, disrupts the extracellular matrix and forms a non-functional scar that leads towards adverse left ventricular (LV) remodelling. If left untreated this eventually leads to heart failure. Besides extensive advancement in medical therapy, complete functional recovery is never accomplished, as the heart possesses limited regenerative ability. In recent decades, the focus has shifted towards tissue engineering and regenerative strategies that provide an attractive option to improve cardiac regeneration, limit adverse LV remodelling and restore function in an infarcted heart. Acellular scaffolds possess attractive features that have made them a promising therapeutic candidate. Their application in infarcted areas has been shown to improve LV remodelling and enhance functional recovery in post-MI hearts. This review will summarise the updates on acellular scaffolds developed and tested in pre-clinical and clinical scenarios in the past five years with a focus on their ability to overcome damage caused by MI. It will also describe how acellular scaffolds alone or in combination with biomolecules have been employed for MI treatment. A better understanding of acellular scaffolds potentialities may guide the development of customised and optimised therapeutic strategies for MI treatment.

Nanotechnology in cardiac stem cell therapy: cell modulation, imaging and gene delivery

The wide arena of applications opened by nanotechnology is multidimensional. It is already been proven that its prominence can continuously influence human life. The role of stem cells in curing degenerative diseases is another major area of research. Cardiovascular diseases are one of the major causes of death globally. Nanotechnology-assisted stem cell therapy could be used to tackle the challenges faced in the management of cardiovascular diseases. In spite of the positive indications and proven potential of stem cells to differentiate into cardiomyocytes for cardiac repair and regeneration during myocardial infarction, this therapeutic approach still remains in its infancy due to several factors such as non-specificity of injected cells, insignificant survival rate, and low cell retention. Attempts to improve stem cell therapy using nanoparticles have shown some interest among researchers. This review focuses on the major hurdles associated with cardiac stem cell therapy and the role of nanoparticles to overcome the major challenges in this field, including cell modulation, imaging, tracking and gene delivery.

This review summarizes the potential challenges present in cardiac stem cell therapy and the major role of nanotechnology to overcome these challenges including cell modulation, tracking and imaging of stem cells.

HIF-1α inhibits mitochondria-mediated apoptosis and improves the survival of human adipose-derived stem cells in ischemic microenvironments

BACKGROUND

Human adipose mesenchymal stem cells (hADSCs) show poor survival after transplantation, limiting their clinical application. Tissue regeneration resulting from stem cell treatment may be caused by attenuation of hypoxia-inducible factor-1α (HIF-1α). In this study, we constructed hADSCs stably expressing HIF-1α and investigated the potential effects of HIF-1α expression in the ischemic microenvironment on mitochondrial apoptosis and survival of hADSCs, and studied the mechanisms involved.

METHOD

Apoptosis was induced by an ischemic microenvironment in vitro. ADSCs with stable HIF-1α expression were established. Cell survival and apoptosis were observed by CCK-8 assay, western blotting, flow cytometry, and fluorescence staining. ADSCs were subcutaneously transplanted into nude mice in the location where a hypoxia ischemic microenvironment was simulated in vivo. After 1, 3, and 7 d, mitochondrial apoptotic proteins were evaluated by immunohistochemistry and immunofluorescence staining.

RESULTS

Exogenous HIF-1α downregulated mitochondrial reactive oxygen species, cytochrome c, caspase-9, and caspase-3, but inhibited mitochondrial membrane potential depolarization and increased the Bcl-2/bax ratio. HIF-1α prevented apoptosis and promoted vascular endothelial growth factor (VEGF) secretion as demonstrated by enzyme-linked immunosorbent assay (ELISA), terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, and flow cytometry analysis. HIF-1α enhanced the survival of transplanted ADSCs in nude mice.

CONCLUSION

We have shown that through inhibition of the mitochondria-mediated apoptotic pathway and promotion of VEGF secretion in hADSCs in an ischemic microenvironment, HIF-1α may potentially be applied in clinical therapy and as an alternative strategy for improving hADSC therapy.

In Vivo Assessment of Decellularized Porcine Myocardial Slice as an Acellular Cardiac Patch

Acellular cardiac patches made of various biomaterials have shown to improve heart function after myocardial infarction (MI). Extracellular matrix scaffold derived from a decellularized tissue has unique advantages to serve as an acellular cardiac patch due to its biomimetic nature. In this study, we examined the therapeutic outcomes of using a decellularized porcine myocardium slice (dPMS) as an acellular patch in a rat acute MI model. dPMSs with two different thicknesses (300 and 600 μm) were patched to the infarcted area of the rat myocardium, and their effects on cardiac function and host interactions were assessed. We found that the implanted dPMS firmly attached to host myocardium after implantation and prevented thinning of the left ventricular (LV) wall after an MI. A large number of host cells were identified to infiltrate into the implanted dPMS, and a significant number of vessel structures was observed in the dPMS and infarcted area. We detected a significantly higher density of M2 macrophages in the groups treated with dPMSs as compared to the MI group. Contraction of the LV wall and cardiac functional parameters (left ventricular ejection fraction and fractional shortening) was significantly improved in the treatment groups (300 and 600 μm dPMS) 4 weeks after surgery. Our results proved the therapeutic benefits of using dPMS as an acellular cardiac patch for the treatment of acute myocardial infarction.

Increasing the Efficacy of Stem Cell Therapy via Triple-Function Inorganic Nanoparticles

Stem cell therapy in heart disease is challenged by mis-injection, poor survival, and low cell retention. Here, we describe a biocompatible multifunctional silica-iron oxide nanoparticle to help solve these issues. The nanoparticles were made via an in situ growth of Fe₃O₄ nanoparticles on both the external surfaces and pore walls of mesocellular foam silica nanoparticles. In contrast to previous work, this approach builds a magnetic moiety inside the pores of a porous silica structure. These materials serve three roles: drug delivery, magnetic manipulation, and imaging. The addition of Fe₃O₄ to the silica nanoparticles increased their colloidal stability, T₂-based magnetic resonance imaging contrast, and superparamagnetism. We then used the hybrid materials as a sustained release vehicle of insulin-like growth factor-a pro-survival agent that can increase cell viability. In vivo rodent studies show that labeling stem cells with this nanoparticle increased the efficacy of stem cell therapy in a ligation/reperfusion model. The nanoparticle-labeled cells increase the mean left ventricular ejection fraction by 11 and 21% and the global longitudinal strain by 24 and 34% on days 30 and 60, respectively. In summary, this multifunctional nanomedicine improves stem cell survival via the sustained release of pro-survival agents.

Effects of transplantation of hypoxia-inducible factor-1α genemodified cardiac stem cells on cardiac function of heart failure rats after myocardial infarction

OBJECTIVE

To evaluate the effects of transplantation of hypoxia-inducible factor-1α (HIF-1α) gene-modified cardiac stem cells (CSCs) on the cardiac function of heart failure rats after myocardial infarction (MI).

METHODS

Twenty-four Sprague-Dawley rats were randomly divided into three groups: HIF-1α-modified CSCs group, single CSCs group, and model group. The model of heart failure after MI was established by thoracotomy-left anterior descending coronary artery ligation, followed by injection of modified CSCs, single CSCs, and PBS, respectively, 2 weeks later. The results were observed 4 weeks later.

RESULTS

CSCs were infected with recombinant adenovirus. HIF-1α mRNA level of HIF-1α-enhanced green fluorescent protein (EGFP)+CSCs group significantly surpassed those of EGFP+CSCs and CSCs groups (p<0.001). Left ventricular ejection fractions (LVEFs) of HIF-1α+CSCs+MI and CSCs+MI groups significantly increased compared with the model group (p<0.001). The difference between LVEFs before and after transplantation was positively correlated with the survival rate of CSCs in infarction border zone (r=0.867, p<0.001). The apoptosis rate of HIF1α+CSCs+MI group was significantly lower than that of CSCs+MI group (p=0.008). The expression of vascular endothelial growth factor protein in HIF-1α+CSCs+MI group significantly increased, compared with that of MI group (p<0.001). The capillary density of HIF-1α+CSCs+MI group significantly exceeded that of CSCs+MI group (p<0.001).

CONCLUSION

Transplantation of either HIF-1α-modified CSCs or single CSCs reduced cardiomyocyte apoptosis in rats with heart failure after MI, promoted vascular regeneration in infarct area, and improved cardiac function. Particularly, HIF-1α-modified CSCs had more significant effects.

[Stem cells: searching predisposition to cardiac commitment by surface markers expression]

It is well-known that cardiovascular diseases are the leading cause of death worldwide, and represent an important economic burden to health systems. In an attempt to solve this problem, stem cell therapy has emerged as a therapeutic option. Within the last 20 years, a great variety of stem cells have been used in different myocardial infarction models. Up until now, the use of cardiac stem cells (CSCs) has seemed to be the best option, but the inaccessibility and scarcity of these cells make their use unreliable. Additionally, there is a high risk as they have to be obtained directly from the heart of the patient. Unlike CSCs, adult stem cells originating from bone marrow or adipose tissue, among others, appear to be an attractive option due to their easier accessibility and abundance, but particularly due to the probable existence of cardiac progenitors among their different sub-populations. In this review an analysis is made of the surface markers present in CSCs compared with other adult stem cells. This suggested the pre-existence of cells sharing specific surface markers with CSCs, a predictable immunophenotype present in some cells, although in low proportions, and with a potential of cardiac differentiation that could be similar to CSCs, thus increasing their therapeutic value. This study highlights new perspectives regarding MSCs that would enable some of these sub-populations to be differentiated at cardiac tissue level.

Optimal Environmental Stiffness for Stem Cell Mediated Ischemic Myocardium Repair

Cardiovascular diseases related to myocardial infarction (MI) contribute significantly to morbidity and mortality worldwide. The loss of cardiomyocytes during MI is a key factor in the impairment of cardiac-pump functions. Employing cell transplantation has shown great potential as a therapeutic approach in regenerating ischemic myocardium. Several studies have suggested that the therapeutic effects of stem cells vary based on the timing of cell administration. It has been clearly established that the myocardium post-infarction experiences a time-dependent stiffness change, and many studies have highlighted the importance of stiffness (elasticity) of microenvironment on modulating the fate and function of stem cells. Therefore, this chapter outlines our studies and other experiments designed to establish the optimal stiffness of microenvironment that maximizes benefits for maintaining cell survival, promoting phenotypic plasticity, and improving functional specification of the engrafted stem cells.

Progenitor cells from atria, ventricle and peripheral blood of the same patients exhibit functional differences associated with cardiac repair

AIM

Deciding the best cell type for cardiac regeneration remains a big challenge. No studies have directly compared the functional efficacy of cardiac progenitor cells (CPCs) with extra-cardiac stem cells isolated from the same patient.

METHODS AND RESULTS

We compared the functional characteristics of endothelial progenitor cells (EPCs), right atrial (RAA) CPCs and left ventricular (LV) CPCs isolated from the same patients (n=14). Within the same heart, RAA and LV CPCs exhibited marked differences in surface marker expression, with RAA CPCs exhibiting better expansion potential and migration properties. When subjected to hypoxia and serum starvation to simulate in vivo ischemic environment, RAA and LV CPCs exhibited similar pattern of resistance to apoptotic cell death under ischemia. Interestingly, EPCs exhibited highest resistance to apoptotic cell death, however, they also showed the lowest proliferation under hypoxia. RT-profiler array showed comparable gene expression pattern in RAA and LV CPCs, while they were differentially expressed in EPCs. Further, treating human umbilical vein endothelial cells with conditioned medium (CM) from LV showed maximum angiogenic potential, while cardiomyocytes treated with CM from RAA showed greatest survival under hypoxic conditions.

CONCLUSIONS

Results from this study provide the first evidence that progenitor cells from different regions exhibit functional differences within the same patient.

Stem cell-based therapies to promote angiogenesis in ischemic cardiovascular disease

Stem cell therapy is a promising approach for the treatment of tissue ischemia associated with myocardial infarction and peripheral arterial disease. Stem and progenitor cells derived from bone marrow or from pluripotent stem cells have shown therapeutic benefit in boosting angiogenesis as well as restoring tissue function. Notably, adult stem and progenitor cells including mononuclear cells, endothelial progenitor cells, and mesenchymal stem cells have progressed into clinical trials and have shown positive benefits. In this review, we overview the major classes of stem and progenitor cells, including pluripotent stem cells, and summarize the state of the art in applying these cell types for treating myocardial infarction and peripheral arterial disease.

Stem cells: An eventual treatment option for heart diseases

Stem cells are of global excitement for various diseases including heart diseases. It is worth to understand the mechanism or role of stem cells in the treatment of heart failure. Bone marrow derived stem cells are commonly practiced with an aim to improve the function of the heart. The majority of studies have been conducted with acute myocardial infarction and a few has been investigated with the use of stem cells for treating chronic or dilated cardiomyopathy. Heterogeneity in the treated group using stem cells has greatly emerged. Ever increasing demand for any alternative made is of at most priority for cardiomyopathy. Stem cells are of top priority with the current impact that has generated among physicians. However, meticulous selection of proper source is required since redundancy is clearly evident with the present survey. This review focuses on the methods adopted using stem cells for heart diseases and outcomes that are generated so far with an idea to determine the best therapeutic possibility in order to fulfill the present demand.

Effects of C-Reactive Protein on the Cardiac Differentiation of Mouse Embryonic Stem Cells

A major challenge in stem cell therapy for cardiac repair is how to obtain normally functioning stem cell-derived cardiomyocytes. We aim to address the effects of C-reactive protein (CRP) on the cardiac differentiation of embryonic stem (ES) cells. Immunostaining, Western blotting and electrophysiology were employed. A hundred fifty milligran/liters CRP significantly reduced the percentage of cardiomyocytes differentiated from mouse ES cells, while it may also promote sarcomere development compared to 30 mg/L CRP treatment. Further examination of the action potential (AP) in individual ES cell-derived cardiomyocytes showed that there exist three types of cardiomyocytes: artial-like (A-like), ventricular-like (V-like), and pacemaker-like (P-like). A hundred fifty milligran/liters CRP treatment decreased the P-like cardiomyocytes, whereas it increased the A-like. Such inhibitory effect and alteration were not significant at 30 mg/L CRP treatment. Moreover, 150 mg/L CRP significantly increased the APD90 (90% of duration of AP) and decreased the spontaneous firing rate of AP in P-like cells, while had little effect on other electrophysiological characteristics, including APA (AP amplitude) and MDP (maximum diastolic potential). This study revealed the effect of CRP on the cardiac differentiation of ES cells. It provides an in vitro pathological model and may be of importance to the future work of ES cell-based therapy in clinical applications and in vivo pathological studies.

in vitro development of bioimplants made up of elastomeric scaffolds with peptide gel filling seeded with human subcutaneous adipose tissue-derived progenitor cells

Myocardial tissue lacks the ability to regenerate itself significantly following a myocardial infarction. Thus, new strategies that could compensate this lack are of high interest. Cardiac tissue engineering (CTE) strategies are a relatively new approach that aims to compensate the tissue loss using combination of biomaterials, cells and bioactive molecules. The goal of the present study was to evaluate cell survival and growth, seeding capacity and cellular phenotype maintenance of subcutaneous adipose tissue-derived progenitor cells in a new synthetic biomaterial scaffold platform. Specifically, here we tested the effect of the RAD16-I peptide gel in microporous poly(ethyl acrylate) polymers using two-dimensional PEA films as controls. Results showed optimal cell adhesion efficiency and growth in the polymers coated with the self-assembling peptide RAD16-I. Importantly, subATDPCs seeded into microporous PEA scaffolds coated with RAD16-I maintained its phenotype and were able to migrate outwards the bioactive patch, hopefully toward the infarcted area once implanted. These data suggest that this bioimplant (scaffold/RAD16-I/cells) can be suitable for further in vivo implantation with the aim to improve the function of affected tissue after myocardial infarction.

Enhancing stem cell survival in an ischemic heart by CRISPR-dCas9-based gene regulation

Ischemic heart disease has remained the number one killer around the world for over the past 20 years. While stem cell therapy has become a promising new frontier to repair the damaged heart, limited stem cell survivability post-transplantation has precluded widespread use of this therapy. Strategies to genetically modify stem cells to activate pro-survival and anti-apoptotic and anti-inflammatory pathways, such as Akt and heme oxygenase-1, have been shown to improve the lifespan of transplanted stem cells within the ischemic myocardium, but constitutive overexpression of these pathways at high levels has been shown to have side effects. Therefore, more specific and controlled gene activation would be necessary. Current techniques used for gene regulation include zinc finger and TALE proteins, but there are still disadvantages to each of these methods, such as ease and cost of use. Also, those methods use synthesized promoters to express synthesized cDNA, which lack regulatory elements, including introns and 3' untranslated regions for microRNA mediated post-transcriptional regulation. A new novel technique, the CRISPR/dCas9 system, was recently developed as a simple and efficient method for endogenous gene regulation. With its use of single guide chimeric RNA's (sgRNA's), this system has been shown to provide a high level of specificity and efficiency. When targeting different loci, past studies have found that the CRISPR/dCas9 system can activate gene expression at varying levels. In addition, this system makes use of the genome's endogenous regulatory elements, such as the aforementioned introns and 3' UTR's, which can help provide a safer method of gene activation. If targeted to a gene promoting cellular survival or decreasing cell death, it could potentially improve stem cell longevity in a more efficient and controllable manner. As a result, our hypothesis is to use the CRISPR/dCas9 system to activate expression of an anti-inflammatory and anti-apoptotic gene, such as heme oxygenase-1 (HO-1), to an optimal level to increase transplanted stem cell survival while also mitigating its cytotoxic effects due to lack of internal regulation, thus prolonging its effects within the ischemic myocardium leading to greater therapeutic benefit.

Fostering public cord blood banking and research in Canada

In June 2013, Canadian Blood Services (CBS) established the National Public Cord Blood Bank (NPCBB) accessible to Canadian and international patients and researchers. The NPCBB promotes efforts that contribute to research and improved clinical care by making units not suitable for banking or transplantation available for research. In the context of the NPCBB of the CBS, this article will focus on the practical tools (e.g., consent protocols) developed to optimize umbilical cord blood (UCB) banking and research while enabling ethical provenance of UCB stem cells. The Canadian approach represents an ideal model for comparison as it is a country in which the national public bank (and other regional/provincial public banks) coexists with private companies.

Stem cell therapies for the treatment of radiation-induced normal tissue side effects

SIGNIFICANCE

Targeted irradiation is an effective cancer therapy but damage inflicted to normal tissues surrounding the tumor may cause severe complications. While certain pharmacologic strategies can temper the adverse effects of irradiation, stem cell therapies provide unique opportunities for restoring functionality to the irradiated tissue bed.

RECENT ADVANCES

Preclinical studies presented in this review provide encouraging proof of concept regarding the therapeutic potential of stem cells for treating the adverse side effects associated with radiotherapy in different organs. Early-stage clinical data for radiation-induced lung, bone, and skin complications are promising and highlight the importance of selecting the appropriate stem cell type to stimulate tissue regeneration.

CRITICAL ISSUES

While therapeutic efficacy has been demonstrated in a variety of animal models and human trials, a range of additional concerns regarding stem cell transplantation for ameliorating radiation-induced normal tissue sequelae remain. Safety issues regarding teratoma formation, disease progression, and genomic stability along with technical issues impacting disease targeting, immunorejection, and clinical scale-up are factors bearing on the eventual translation of stem cell therapies into routine clinical practice.

FUTURE DIRECTIONS

Follow-up studies will need to identify the best possible stem cell types for the treatment of early and late radiation-induced normal tissue injury. Additional work should seek to optimize cellular dosing regimes, identify the best routes of administration, elucidate optimal transplantation windows for introducing cells into more receptive host tissues, and improve immune tolerance for longer-term engrafted cell survival into the irradiated microenvironment.

Myocardial regeneration of the failing heart

Human heart failure (HF) is one of the leading causes of morbidity and mortality worldwide. Currently, heart transplantation and implantation of mechanical devices represent the only available treatments for advanced HF. Two alternative strategies have emerged to treat patients with HF. One approach relies on transplantation of exogenous stem cells (SCs) of non-cardiac or cardiac origin to induce cardiac regeneration and improve ventricular function. Another complementary strategy relies on stimulation of the endogenous regenerative capacity of uninjured cardiac progenitor cells to rebuild cardiac muscle and restore ventricular function. Various SC types and delivery strategies have been examined in the experimental and clinical settings; however, neither the ideal cell type nor the cell delivery method for cardiac cell therapy has yet emerged. Although the use of bone marrow (BM)-derived cells, most frequently exploited in clinical trials, appears to be safe, the results are controversial. Two recent randomized trials have failed to document any beneficial effects of intracardiac delivery of autologous BM mononuclear cells on cardiac function of patients with HF. The remarkable discovery that various populations of cardiac progenitor cells (CPCs) are present in the adult human heart and that it possesses limited regeneration capacity has opened a new era in cardiac repair. Importantly, unlike BM-derived SCs, autologous CPCs from myocardial biopsies cultured and subsequently delivered by coronary injection to patients have given positive results. Although these data are promising, a better understanding of how to control proliferation and differentiation of CPCs, to enhance their recruitment and survival, is required before CPCs become clinically applicable therapeutics.

Directed cardiomyogenesis of autologous human induced pluripotent stem cells recruited to infarcted myocardium with bioengineered antibodies

OBJECTIVE

Myocardial infarctions constitute a major factor contributing to non-natural mortality world-wide. Clinical trials of myocardial regenerative therapy, currently pursued by cardiac surgeons, involve administration of stem cells into the hearts of patients suffering from myocardial infarctions. Unfortunately, surgical acquisition of these cells from bone marrow or heart is traumatic, retention of these cells to sites of therapeutic interventions is low, and directed differentiation of these cells in situ into cardiomyocytes is difficult. The specific aims of this work were: (1) to generate autologous, human, pluripotent, induced stem cells (ahiPSCs) from the peripheral blood of the patients suffering myocardial infarctions; (2) to bioengineer heterospecific antibodies (htAbs) and use them for recruitment of the ahiPSCs to infarcted myocardium; (3) to initiate in situ directed cardiomyogenesis of the ahiPSCs retained to infarcted myocardium.

METHODS

Peripheral blood was drawn from six patients scheduled for heart transplants. Mononuclear cells were isolated and reprogrammed, with plasmids carrying six genes (NANOG, POU5F1, SOX2, KLF4, LIN28A, MYC), to yield the ahiPSCs. Cardiac tissues were excised from the injured hearts of the patients, who received transplants during orthotopic surgery. These tissues were used to prepare in vitro models of stem cell therapy of infarcted myocardium. The htAbs were bioengineered, which simultaneously targeted receptors displayed on pluripotent stem cells (SSEA-4, SSEA-3, TRA-1-60, TRA-1-81) and proteins of myocardial sarcomeres (myosin, α-actinin, actin, titin). They were used to bridge the ahiPSCs to the infarcted myocardium. The retained ahiPSCs were directed with bone morphogenetic proteins and nicotinamides to differentiate towards myocardial lineage.

RESULTS

The patients' mononuclear cells were efficiently reprogrammed into the ahiPSCs. These ahiPSCs were administered to infarcted myocardium in in vitro models. They were recruited to and retained at the treated myocardium with higher efficacy and specificity, if were preceded with the htAbs, than with isotype antibodies or plain buffers. The retained cells differentiated into cardiomyocytes.

CONCLUSIONS

The proof of concept has been attained, for reprogramming the patients' blood mononuclear cells (PBMCs) into the ahiPSCs, recruiting these cells to infarcted myocardium, and initiating their cardiomyogenesis. This novel strategy is ready to support the ongoing clinical trials aimed at regeneration of infarcted myocardium.

Plasminogen regulates cardiac repair after myocardial infarction through its noncanonical function in stem cell homing to the infarcted heart

OBJECTIVES

The purpose of this study was to investigate the role of plasminogen (Plg) in stem cell-mediated cardiac repair and regeneration after myocardial infarction (MI).

BACKGROUND

An MI induces irreversible tissue damage, eventually leading to heart failure. Bone marrow (BM)-derived stem cells promote tissue repair and regeneration after MI. Thrombolytic treatment with Plg activators significantly improves the clinical outcome in MI by restoring cardiac perfusion. However, the role of Plg in stem cell-mediated cardiac repair remains unclear.

METHODS

An MI was induced in Plg-deficient (Plg(-/-)) and wild-type (Plg(+/+)) mice by ligation of the left anterior descending coronary artery. Stem cells were visualized by in vivo tracking of green fluorescent protein (GFP)-expressing BM cells after BM transplantation. Cardiac function, stem cell homing, and signaling pathways downstream of Plg were examined.

RESULTS

Granulocyte colony-stimulating factor, a stem cell mobilizer, significantly promoted BM-derived stem cell (GFP(+)c-kit(+) cell) recruitment into the infarcted heart and stem cell-mediated cardiac repair in Plg(+/+) mice. However, Plg deficiency markedly inhibited stem cell homing and cardiac repair, suggesting that Plg is critical for stem cell-mediated cardiac repair. Moreover, Plg regulated C-X-C chemokine receptor type 4 (CXCR4) expression in stem cells in vivo and in vitro through matrix metalloproteinase-9. Lentiviral reconstitution of CXCR4 expression in BM cells successfully rescued stem cell homing to the infarcted heart in Plg-deficient mice, indicating that CXCR4 has a critical role in Plg-mediated stem cell homing after MI.

CONCLUSIONS

These findings have identified a novel role for Plg in stem cell-mediated cardiac repair after MI. Thus, targeting Plg may offer a new therapeutic strategy for stem cell-mediated cardiac repair after MI.

Mesenchymal stem cell delivery strategies to promote cardiac regeneration following ischemic injury

Myocardial infarction (MI) is one of the leading causes of mortality worldwide and is associated with irreversible cardiomyocyte death and pathological remodeling of cardiac tissue. In the past 15 years, several animal models have been developed for pre-clinical testing to assess the potential of stem cells for functional tissue regeneration and the attenuation of left ventricular remodeling. The promising results obtained in terms of improved cardiac function, neo-angiogenesis and reduction in infarct size have motivated the initiation of clinical trials in humans. Despite the potential, the results of these studies have highlighted that the effective delivery and retention of viable cells within the heart remain significant challenges that have limited the therapeutic efficacy of cell-based therapies for treating the ischemic myocardium. In this review, we discuss key elements for designing clinically translatable cell-delivery approaches to promote myocardial regeneration. Key topics addressed include cell selection, with a focus on mesenchymal stem cells derived from the bone marrow (bMSCs) and adipose tissue (ASCs), including a discussion of their potential mechanisms of action. Natural and synthetic biomaterials that have been investigated as injectable cell delivery vehicles for cardiac applications are critically reviewed, including an analysis of the role of the biomaterials themselves in the therapeutic scheme.

Directed cardiomyogenesis of autologous human induced pluripotent stem cells recruited to infarcted myocardium with bioengineered antibodies

Objective

Myocardial infarctions constitute a major factor contributing to non-natural mortality world-wide. Clinical trials ofmyocardial regenerative therapy, currently pursued by cardiac surgeons, involve administration of stem cells into the hearts of patients suffering from myocardial infarctions. Unfortunately, surgical acquisition of these cells from bone marrow or heart is traumatic, retention of these cells to sites of therapeutic interventions is low, and directed differentiation of these cells in situ into cardiomyocytes is difficult. The specific aims of this work were: (1) to generate autologous, human, pluripotent, induced stem cells (ahiPSCs) from the peripheral blood of the patients suffering myocardial infarctions; (2) to bioengineer heterospecific tetravalent antibodies (htAbs) and use them for recruitment of the ahiPSCs to infarcted myocardium; (3) to initiate in situ directed cardiomyogenesis of the ahiPSCs retained to infarcted myocardium.

Methods

Peripheral blood was drawn from six patients scheduled for heart transplants. Mononuclear cells were isolated and reprogrammed, with plasmids carrying six genes (NANOG, POU5F1, SOX2, KLF4, LIN28A, MYC), to yield the ahiPSCs. Cardiac tissues were excised from the injured hearts of the patients, who received transplants during orthotopic surgery. These tissues were used to prepare in vitro model of stem cell therapy of infarcted myocardium. The htAbs were bioengineered, which simultaneously targeted receptors displayed on pluripotent stem cells (SSEA-4, SSEA-3, TRA-1-60, TRA-1-81) and proteins of myocardial sarcomeres (myosin, α-actinin, actin, titin). They were used to bridge the ahiPSCs to the infarcted myocardium. The retained ahiPSCs were directed with bone morphogenetic proteins and nicotinamides to differentiate towards myocardial lineage.

Results

The patients’ mononuclear cells were efficiently reprogrammed into the ahiPSCs. These ahiPSCs were administered to infarcted myocardium in in vitro models. They were recruited to and retained at the treated myocardium with higher efficacy and specificity, if were preceded the htAbs, than with isotype antibodies or plain buffers. The retained cells differentiated into cardiomyocytes.

Conclusions

The proof of concept has been attained, for reprogramming the patients’ blood mononuclear cells (PBMCs) into the ahiPSCs, recruiting these cells to infarcted myocardium, and initiating their cardiomyogenesis. This novel strategy is ready to support the ongoing clinical trials aimed at regeneration of infarcted myocardium.

Intracoronary Infusion of Autologous CD133(+) Cells in Myocardial Infarction and Tracing by Tc99m MIBI Scintigraphy of the Heart Areas Involved in Cell Homing

CD133 mesenchymal cells were enriched using magnetic microbead anti-CD133 antibody from bone marrow mononuclear cells (BMMNCs). Flow cytometry and immunocytochemistry analysis using specific antibodies revealed that these cells were essentially 89 ± 4% CD133⁺ and 8 ± 5% CD34⁺. CD133⁺/CD34⁺ BMMNCs secrete important bioactive proteins such as cardiotrophin-1, angiogenic and neurogenic factors, morphogenetic proteins, and proinflammatory and remodeling factors in vitro. Single intracoronary infusions of autologous CD133⁺/CD34⁺ BMMNCs are effective and reduce infarct size in patients as analyzed by Tc99m MIBI myocardial scintigraphy. The majority of patients were treated via left coronary artery. Nine months after cell therapy, 5 out of 8 patients showed a net positive response to therapy in different regions of the heart. Uptake of Tc99 isotope and revitalization of the heart area in inferoseptal region are more pronounced (P = 0.016) as compared to apex and anterosptal regions after intracoronary injection of the stem cells. The cells chosen here have the properties essential for their potential use in cell therapy and their homing can be followed without major difficulty by the scintigraphy. The cell therapy proposed here is safe and should be practiced, as we found, in conjunction with scintigraphic observation of areas of heart which respond optimally to the infusion of autologous CD133⁺/CD34⁺ BMMNCs.

Guidance of stem cells to a target destination in vivo by magnetic nanoparticles in a magnetic field

Stem cells contribute to physiological processes such as postischemic neovascularization and vascular re-endothelialization, which help regenerate myocardial defects or repair vascular injury. However, therapeutic efficacy of stem cell transplantation is often limited by inefficient homing of systemically administered cells, which results in a low number of cells accumulating at sites of pathology. In this study, anti-CD34 antibody-coated magnetic nanoparticles (Fe3O4@PEG-CD34) are shown to have high affinity to stem cells. The results of hemolysis rate and activated partial thromboplastin time (APTT) tests indicate that such nanoparticle may be used safely in the blood system. In vitro studies showed that a nanoparticle concentration of 100 μg/mL gives rise to a significant increase in cell retention using an applicable permanent magnet, exerting minimal negative effect on cell viability and migration. Subsequent in vivo studies indicate that nanopartical can specifically bind stem cells with good magnetic response. Anti-CD34 antibody coated magnetic nanoparticle may be used to help deliver stem cells to a lesion site in the body for better treatment.

Stem cell recruitment after injury: lessons for regenerative medicine

Tissue repair and regeneration are thought to involve resident cell proliferation as well as the selective recruitment of circulating stem and progenitor cell populations through complex signaling cascades. Many of these recruited cells originate from the bone marrow, and specific subpopulations of bone marrow cells have been isolated and used to augment adult tissue regeneration in preclinical models. Clinical studies of cell-based therapies have reported mixed results, however, and a variety of approaches to enhance the regenerative capacity of stem cell therapies are being developed based on emerging insights into the mechanisms of progenitor cell biology and recruitment following injury. This article discusses the function and mechanisms of recruitment of important bone marrow-derived stem and progenitor cell populations following injury, as well as the emerging therapeutic applications targeting these cells.

Cellular cardiomyoplasty: its past, present, and future

Cellular cardiomyoplasty is a cell therapy using stem cells or progenitor cells for myocardial regeneration to improve cardiac function and mitigate heart failure. Since we first published cellular cardiomyoplasty in 1989, this procedure became the innovative method to treat damaged myocardium other than heart transplantation. A significant improvement in cardiac function, metabolism, and perfusion is generally observed in experimental and clinical studies, but the improvement is mild and incomplete. Although safety, feasibility, and efficacy have been well documented for the procedure, the beneficial mechanisms remain unclear and optimization of the procedure requires further study. This chapter briefly reviews the stem cells used for cellular cardiomyoplasty and their clinical outcomes with possible improvements in future studies.

Recombinant human brain natriuretic peptide therapy combined with bone mesenchymal stem cell transplantation for treating heart failure in rats

This study aimed to investigate the effects of combined recombinant human brain natriuretic peptide (rhBNP) therapy and bone mesenchymal stem cell (BMSC) transplantation on cell survival in myocardial tissues and on heart function in a rat model of heart failure (HF). Rat BMSCs were isolated, amplified and adherent cultured in vitro. A rat model of HF was established via the intraperitoneal injection of doxorubicin (Adriamycin). The rats were randomly divided into normal, HF, BMSC, rhBNP and BMSC plus rhBNP groups. The BMSCs were administered once via tail vein injection and rhBNP was infused via the jugular vein. Echocardiography and polygraphy were used to evaluate heart function. An enzyme‑linked immunosorbent assay was used to detect the changes in brain natriuretic peptide (BNP) concentration prior to and following intervention. Western blot analysis was used to detect the expression of the myocardium‑specific proteins GATA-binding protein 4 (GATA-4), connexin 43 (Cx43) and cardiac troponin I (cTnI). The results of cardiac echocardiography and the hemodynamic data show that various indicators of left ventricular systolic function in the BMSC plus rhBNP group were significantly improved compared with those in the other groups (P<0.05). No significant differences in the improvement of cardiac function were observed between the BMSC and rhBNP groups (P>0.05). Following treatment, a significant difference in BNP levels was observed between the BMSC plus rhBNP and the BMSC groups (P<0.05). The GATA-4, Cx43 and cTnI expression levels in the BMSC plus rhBNP group were higher than those in the BMSC group. Compared with rhBNP treatment, BMSC transplantation alone does not significantly improve heart function. However, combining rhBNP therapy and BMSC transplantation increases the expression levels of GATA-4 and other proteins to improve cardiac systolic and diastolic function.

The plasminogen system in regulating stem cell mobilization

The treatment of patients with hematopoietic progenitor and stem cells (HPSCs) to reconstitute hematopoiesis after myeloablative therapy or to repair ischemia after myocardial infarction has significantly improved clinical outcomes. Successful blood or bone marrow transplants require a sufficient number of HPSCs capable of homing to the injured site to regenerate tissue. Granulocyte-colony stimulating factor (G-CSF) is widely used clinically for stem cell mobilization. However, in some patients the response is poor, thus a better understanding of the mechanisms underlying G-CSF-regulated stem cell mobilization is needed. The pasminogen (Plg) system is the primary fibrinolytic pathway responsible for clot dissolution after thrombosis. Recent evidence suggests that Plg plays a pivotal role in stem cell mobilization from the bone marrow to the peripheral circulation, particularly in HPSC mobilization in response to G-CSF. This paper will discuss the potential mechanisms by which the Plg system regulates stem cell mobilization, focusing on stepwise proteolysis and signal transduction during HPSC egress from their bone marrow niche. Clear elucidation of the underlying mechanisms may lead to the development of new Plg-based therapeutic strategies to improve stem cell mobilization in treating hematological and cardiovascular diseases.

Heart repair by reprogramming non-myocytes with cardiac transcription factors

The adult mammalian heart possesses little regenerative potential following injury. Fibrosis due to activation of cardiac fibroblasts impedes cardiac regeneration and contributes to loss of contractile function, pathological remodelling and susceptibility to arrhythmias. Cardiac fibroblasts account for a majority of cells in the heart and represent a potential cellular source for restoration of cardiac function following injury through phenotypic reprogramming to a myocardial cell fate. Here we show that four transcription factors, GATA4, HAND2, MEF2C and TBX5, can cooperatively reprogram adult mouse tail-tip and cardiac fibroblasts into beating cardiac-like myocytes in vitro. Forced expression of these factors in dividing non-cardiomyocytes in mice reprograms these cells into functional cardiac-like myocytes, improves cardiac function and reduces adverse ventricular remodelling following myocardial infarction. Our results suggest a strategy for cardiac repair through reprogramming fibroblasts resident in the heart with cardiogenic transcription factors or other molecules.