Cell-based therapy for heart disease: a clinically oriented perspective

Engineered resveratrol-loaded fibrous scaffolds promotes functional cardiac repair and regeneration through Thioredoxin-1 mediated VEGF pathway

Despite recent advancements, mortality due to coronary heart disease (CHD) remains high. Recently, the use of tissue-engineered grafts and scaffolds has emerged as a candidate for supporting the myocardium after an ischemic event. Resveratrol is a naturally occurring plant-based non-flavonoid polyphenolic compound found in many natural foods, including grapes and red wine. We embedded resveratrol in a polycaprolactone (PCL) scaffold and evaluated the cardio-therapeutic effects in a murine model of myocardial infarction (MI), with animals being grouped into Sham (S), Myocardial Infarction (MI), MI + PCL, and MI + PCL-Resveratrol (MI + PCL-R). After 4 and 8 weeks, echocardiography was performed to assess ejection fraction (EF) and fractional shortening (FS), which was followed by immunohistochemistry and immunofluorescence analysis at 8 weeks. The MI + PCL-R group showed a significant improvement in EF and FS compared with the MI + PCL group at 4 and 8-weeks post-surgery. PCL-R scaffolds treated hearts revealed decreased inflammatory cell infiltration, improved collagen extracellular matrix (ECM) secretion and blood vessel network formation following MI. The immunofluorescence analysis revealed resveratrol-loaded scaffolds promote increased expression of cTnT, Cx-43, Trx-1, and VEGF proteins. This study reports resveratrol-mediated rescue of ischemic myocardium when delivered through a biodegradable polymeric scaffold system after MI.

Molecular basis of functional myogenic specification of Bona Fide multipotent adult cardiac stem cells

Ischemic Heart Disease (IHD) remains the developed world's number one killer. The improved survival from Acute Myocardial Infarction (AMI) and the progressive aging of western population brought to an increased incidence of chronic Heart Failure (HF), which assumed epidemic proportions nowadays. Except for heart transplantation, all treatments for HF should be considered palliative because none of the current therapies can reverse myocardial degeneration responsible for HF syndrome. To stop the HF epidemic will ultimately require protocols to reduce the progressive cardiomyocyte (CM) loss and to foster their regeneration. It is now generally accepted that mammalian CMs renew throughout life. However, this endogenous regenerative reservoir is insufficient to repair the extensive damage produced by AMI/IHD while the source and degree of CM turnover remains strongly disputed. Independent groups have convincingly shown that the adult myocardium harbors bona-fide tissue specific cardiac stem cells (CSCs). Unfortunately, recent reports have challenged the identity and the endogenous myogenic capacity of the c-kit expressing CSCs. This has hampered progress and unless this conflict is settled, clinical tests of repair/regenerative protocols are unlikely to provide convincing answers about their clinical potential. Here we review recent data that have eventually clarified the specific phenotypic identity of true multipotent CSCs. These cells when coaxed by embryonic cardiac morphogens undergo a precisely orchestrated myogenic commitment process robustly generating bona-fide functional cardiomyocytes. These data should set the path for the revival of further investigation untangling the regenerative biology of adult CSCs to harness their potential for HF prevention and treatment.

Imaging cellular pharmacokinetics of 18F-FDG and 6-NBDG uptake by inflammatory and stem cells

OBJECTIVES

Myocardial infarction (MI) causes significant loss of cardiomyocytes, myocardial tissue damage, and impairment of myocardial function. The inability of cardiomyocytes to proliferate prevents the heart from self-regeneration. The treatment for advanced heart failure following an MI is heart transplantation despite the limited availability of the organs. Thus, stem-cell-based cardiac therapies could ultimately prevent heart failure by repairing injured myocardium that reverses cardiomyocyte loss. However, stem-cell-based therapies lack understanding of the mechanisms behind a successful therapy, including difficulty tracking stem cells to provide information on cell migration, proliferation and differentiation. In this study, we have investigated the interaction between different types of stem and inflammatory cells and cell-targeted imaging molecules, 18F-FDG and 6-NBDG, to identify uptake patterns and pharmacokinetics in vitro.

METHODS

Macrophages (both M1 and M2), human induced pluripotent stem cells (hiPSCs), and human amniotic mesenchymal stem cells (hAMSCs) were incubated with either 18F-FDG or 6-NBDG. Excess radiotracer and fluorescence were removed and a 100 μm-thin CdWO4 scintillator plate was placed on top of the cells for radioluminescence microscopy imaging of 18F-FDG uptake, while no scintillator was needed for fluorescence imaging of 6-NBDG uptake. Light produced following beta decay was imaged with a highly sensitive inverted microscope (LV200, Olympus) and an Electron Multiplying Charge-Couple Device (EM-CCD) camera. Custom-written software was developed in MATLAB for image processing.

RESULTS

The average cellular activity of 18F-FDG in a single cell of hAMSCs (0.670±0.028 fCi/μm2, P = 0.001) was 20% and 36% higher compared to uptake in hiPSCs (0.540±0.026 fCi/μm2, P = 0.003) and macrophages (0.430±0.023 fCi/μm2, P = 0.002), respectively. hAMSCs exhibited the slowest influx (0.210 min-1) but the fastest efflux (0.327 min-1) rate compared to the other tested cell lines for 18F-FDG. This cell line also has the highest phosphorylation but exhibited the lowest rate of de-phosphorylation. The uptake pattern for 6-NBDG was very different in these three cell lines. The average cellular activity of 6-NBDG in a single cell of macrophages (0.570±0.230 fM/μm2, P = 0.004) was 38% and 14% higher compared to hiPSCs (0.350±0.160 fM/μm2, P = 0.001) and hAMSCs (0.490±0.028 fM/μm2, P = 0.006), respectively. The influx (0.276 min-1), efflux (0.612 min-1), phosphorylation (0.269 min-1), and de-phosphorylation (0.049 min-1) rates were also highest for macrophages compared to the other two tested cell lines.

CONCLUSION

hAMSCs were found to be 2-3× more sensitive to 18F-FDG molecule compared to hiPSCs/macrophages. However, macrophages exhibited the most sensitivity towards 6-NBDG. Based on this result, hAMSCs targeted with 18F-FDG could be more suitable for understanding the mechanisms behind successful therapy for treating MI patients by gathering information on cell migration, proliferation and differentiation.

Differentiation of Enhanced Green Fluorescent Protein-Labeled Mouse Amniotic Fluid-Derived Stem Cells into Cardiomyocyte-Like Beating Cells

BACKGROUND

Amniotic fluid-derived stem cells (AFSCs) possess optimal differentiation potential and are a promising resource for cell therapy and tissue engineering. Mouse is a good model to be studied for pre-clinical research.

METHODS

In this study, we successfully established enhanced green fluorescent protein mouse-derived amniotic fluid stem cells (EGFP-mAFSCs) and investigated whether EGFP-mAFSCs possess the ability to differentiate into cardiomyocytes by in vitro culture. We evaluated stem-cell differentiation using immunofluorescence.

RESULTS

This study showed that EGFP-mAFSCs can give rise to spontaneously beating cardiomyocyte-like cells expressing the specific markers c-kit, myosin heavy chain, and cardiac troponin I.

CONCLUSIONS

We demonstrated that mAFSCs have the in vitro propensity to acquire a cardiomyogenic phenotype and to a certain extent cardiomyocytes; however the process efficiency which gives rise to cardiomyocyte-like cells remains quite low (2 out of 10 were found).

KEY WORDS

Amniotic fluid; Cardiomyocytes; In vitro differentiation; Stem cells.

Role of adipose-derived stem cells in wound healing

Impaired wound healing remains a challenge to date and causes debilitating effects with tremendous suffering. Recent advances in tissue engineering approaches in the area of cell therapy have provided promising treatment options to meet the challenges of impaired skin wound healing such as diabetic foot ulcers. Over the last few years, stem cell therapy has emerged as a novel therapeutic approach for various diseases including wound repair and tissue regeneration. Several different types of stem cells have been studied in both preclinical and clinical settings such as bone marrow-derived stem cells, adipose-derived stem cells (ASCs), circulating angiogenic cells (e.g., endothelial progenitor cells), human dermal fibroblasts, and keratinocytes for wound healing. Adipose tissue is an abundant source of mesenchymal stem cells, which have shown an improved outcome in wound healing studies. ASCs are pluripotent stem cells with the ability to differentiate into different lineages and to secrete paracrine factors initiating tissue regeneration process. The abundant supply of fat tissue, ease of isolation, extensive proliferative capacities ex vivo, and their ability to secrete pro-angiogenic growth factors make them an ideal cell type to use in therapies for the treatment of nonhealing wounds. In this review, we look at the pathogenesis of chronic wounds, role of stem cells in wound healing, and more specifically look at the role of ASCs, their mechanism of action and their safety profile in wound repair and tissue regeneration.

Chromosomal Instability but Lack of Transformation in Human Myoblast Preparations

Genetic alterations have recently been described as emerging during the culture of embryonic stem cells or induced pluripotent stem cells, raising concerns about their safety in future clinical use. Myoblasts are adult stem cells with important therapeutic potential that have been used in clinical trials for almost 20 years, but their genome integrity has not yet been established. Here we produced 10 human myoblast preparations and investigated their genomic stability. At the third passage, half of the preparations had a normal karyotype and half showed one to four alterations/30 metaphases. Chromosome 2 trisomy was found in 1–2/30 meta-phases and/or 2/100 nuclei by FISH in 3/10 samples, and there was no other recurrent anomaly. When prolonging cultures, these erratic abnormalities were never associated with a growth advantage. Cellular senescence was manifested in all samples by growth arrest before passage 15. Expression of TERT was always negative. Molecular analysis of individual p53 transcripts did not reveal tumorigenic mutations. CGH array (10 samples) and exome sequencing (one sample) failed to detect copy number variations or accumulation of mutations, respectively. Myoblasts did not grow either in soft agar or in vivo after injection in immunodeficient mice. Hence, occasional genomic abnormalities may occur during myoblast culture but are not associated with risk of transformation.

Mechanisms of therapeutic activity of multipotent cells in heart diseases

Analysis of our findings and published reports on possible mechanisms of therapeutic activity of stem/progenitor cell transplantation in cardiovascular pathologies is presented.

Combinatorial biomatrix/cell-based therapies for restoration of host tissue architecture and function

This Progress Report reviews recent advances in the utility of extracellular matrix (ECM)-mimic biomaterials in presenting and delivering therapeutic cells to promote tissue healing. This overview gives a brief introduction of different cell types being used in regenerative medicine and tissue engineering while addressing critical issues that must be overcome before cell-based approaches can be routinely employed in the clinic. A selection of five commonly used cell-associated, biomaterial platforms (collagen, hyaluronic acid, fibrin, alginate, and poly(ethylene glycol)) are reviewed for treatment of a number of acute injury or diseases with emphasis on animal models and clinical trials. This article concludes with current challenges and future perspectives regarding foreign body host response to biomaterials and immunological reactions to allogeneic or xenogeneic cells, vascularization and angiogenesis, matching mechanical strength and anisotropy of native tissues, as well as other non-technical issues regarding the clinical translation of biomatrix/cell-based therapies.

Autologous bone marrow-derived stem cell therapy in heart disease: discrepancies and contradictions

BACKGROUND

Autologous bone marrow stem cell therapy is the greatest advance in the treatment of heart disease for a generation according to pioneering reports. In response to an unanswered letter regarding one of the largest and most promising trials, we attempted to summarise the findings from the most innovative and prolific laboratory.

METHOD AND RESULTS

Amongst 48 reports from the group, there appeared to be 5 actual clinical studies ("families" of reports). Duplicate or overlapping reports were common, with contradictory experimental design, recruitment and results. Readers cannot always tell whether a study is randomised versus not, open-controlled or blinded placebo-controlled, or lacking a control group. There were conflicts in recruitment dates, criteria, sample sizes, million-fold differences in cell counts, sex reclassification, fractional numbers of patients and conflation of competitors' studies with authors' own. Contradictory results were also common. These included arithmetical miscalculations, statistical errors, suppression of significant changes, exaggerated description of own findings, possible silent patient deletions, fractional numbers of coronary arteries, identical results with contradictory sample sizes, contradictory results with identical sample sizes, misrepresented survival graphs and a patient with a negative NYHA class. We tabulate over 200 discrepancies amongst the reports. The 5 family-flagship papers (Strauer 2002, STAR, IACT, ABCD, BALANCE) have had 2665 citations. Of these, 291 citations were to the pivotal STAR or IACT-JACC papers, but 97% of their eligible citing papers did not mention any discrepancies. Five meta-analyses or systematic reviews covered these studies, but none described any discrepancies and all resolved uncertainties by undisclosed methods, in mutually contradictory ways. Meta-analysts disagreed whether some studies were randomised or "accepter-versus-rejecter". Our experience of presenting the discrepancies to journals is that readers may remain unaware of such problems.

CONCLUSIONS

Modern reporting of clinical research can still be imperfect. The scientific literature absorbs such reports largely uncritically. Even meta-analyses seem to resolve contradictions haphazardly. Discrepancies communicated to journals are not guaranteed to reach the scientific community. Journals could consider prioritising systematic reporting of queries even if seemingly minor, and establishing a policy of "habeas data".

The use of cell-sheet technique eliminates arrhythmogenicity of skeletal myoblast-based therapy to the heart with enhanced therapeutic effects

BACKGROUND

Clinical application of skeletal myoblast transplantation has been curtailed due to arrhythmogenicity and inconsistent therapeutic benefits observed in previous studies. However, these issues may be solved by the use of a new cell-delivery mode. It is now possible to generate "cell-sheets" using temperature-responsive dishes without artificial scaffolds. This study aimed to validate the safety and efficacy of epicardial placement of myoblast-sheets (myoblast-sheet therapy) in treating heart failure.

METHODS AND RESULTS

After coronary artery ligation in rats, the same numbers of syngeneic myoblasts were transplanted by intramyocardial injection or cell-sheet placement. Continuous radio-telemetry monitoring detected increased ventricular arrhythmias, including ventricular tachycardia, after intramyocardial injection compared to the sham-control, while these were abolished in myoblast-sheet therapy. This effect was conjunct with avoidance of islet-like cell-cluster formation that disrupts electrical conduction, and with prevention of increased arrhythmogenic substrates due to exaggerated inflammation. Persistent ectopic donor cells were found in the lung only after intramyocardial injection, strengthening the improved safety of myoblast-sheet therapy. In addition, myoblast-sheet therapy enhanced cardiac function, corresponding to a 9.2-fold increase in donor cell survival, compared to intramyocardial injection. Both methods achieved reduced infarct size, decreased fibrosis, attenuated cardiomyocyte hypertrophy, and increased neovascular formation, in association with myocardial upregulation of a group of relevant molecules. The pattern of these beneficial changes was similar between two methods, but the degree was more substantial after myoblast-sheet therapy.

CONCLUSION

The cell-sheet technique enhanced safety and therapeutic efficacy of myoblast-based therapy, compared to the current method, thereby paving the way for clinical application.

In vivo differentiation of human amniotic epithelial cells into cardiomyocyte-like cells and cell transplantation effect on myocardial infarction in rats: comparison with cord blood and adipose tissue-derived mesenchymal stem cells

Human amniotic epithelial cells (h-AECs), which have various merits as a cell source for cell therapy, are known to differentiate into cardiomyocytes in vitro. However, the ability of h-AECs to differentiate into cardiomyocytes in vivo and their cell transplantation effects on myocardial infarction are still unknown. In this study, we assessed whether h-AECs could differentiate into cardiomyocytes in vivo and whether h-AECs transplantation can decrease infarct size and improve cardiac function, in comparison to transplantation of cord blood-derived mesenchymal stem cells (MSCs) or adipose tissue-derived MSCs. For our study, we injected h-AECs, cord blood-derived MSCs, adipose tissue-derived MSCs, and saline into areas of myocardial infarction in athymic nude rats. After 4 weeks, 3% of the surviving h-AECs expressed myosin heavy chain, a marker specific to the myocardium. Compared with the saline group, all cell-implanted groups showed a higher ejection fraction, lower infarct area by positron emission tomography and histology, and more abundant myocardial gene and protein expression in the infarct area. We showed that h-AECs can differentiate into cardiomyocyte-like cells, decrease infarct size, and improve cardiac function in vivo. The beneficial effects of h-AECs were comparable to those of cord blood and adipose tissue-derived MSCs. These results support the need for further studies of h-AECs as a cell source for myocardial regeneration due to their plentiful availability, low immunity, and lack of ethical issues related to their use.

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.

Extracorporeal shockwave myocardial revascularization improves clinical symptoms and left ventricular function in patients with refractory angina

BACKGROUND

Medical therapy for refractory angina is limited and the prognosis is poor. Experimental data suggest that the use of extracorporeal shockwave myocardial revascularization (ESMR) can contribute to angiogenesis and improve symptoms of angina and left ventricular (LV) function. The objective of this study was to examine the effects of ESMR on clinical symptoms as well as LV function as assessed by cardiac MRI in patients with refractory angina.

METHODS

Patients with Canadian Cardiovascular Society (CCS) class III-IV angina despite medical therapy and ischemia documented on thallium or echo-dobutamine were eligible for the study. ESMR therapy was applied with a commercially available cardiac shockwave generator system under echocardiographic guidance. LV function was assessed before and 6 months after therapy by cardiac MRI.

RESULTS

Twenty patients (four women, 16 men; mean age 64 years, range 45-83) were included in the study. The CCS class after treatment improved in all patients (16 patients angina pectoris CCS from III to II and four patients from IV to III). The use of sublingual nitroglycerin was significantly reduced as well. There was a significant improvement in LV ejection fraction as assessed by blinded MRI following therapy in the overall population (51 vs. 59%, P<0.05).

CONCLUSION

This study demonstrates the potential efficacy of ESMR for the treatment of refractory angina pectoris. The patients showed both a significant clinical response as well as improved LV ejection fraction on serial MRI imaging. Larger studies are needed to adequately define the clinical utility of this novel therapy.

[Embryonic stem cells in the treatment of severe cardiac insufficiency]

The experience accumulated in cardiac cell therapy suggests that regeneration of extensively necrotic myocardial areas is unlikely to be achieved by the sole paracrine effects of the grafted cells but rather requires the conversion of these cells into cardiomyocytes featuring the capacity to substitute for those which have been irreversibly lost. In this setting, the use of human pluripotent embryonic stem cells has a strong rationale. The experimental results obtained in animal models of myocardial infarction are encouraging. However, the switch to clinical applications still requires to address some critical issues, among which optimizing cardiac specification of the embryonic stem cells, purifying the resulting progenitor cells so as to graft a purified population devoid from any contamination by residual pluripotent cells which carry the risk of tumorigenesis and controlling the expected allogeneic rejection by clinically acceptable methods. If the solution to these problems is a pre-requisite, the therapeutic success of this approach will also depend on the capacity to efficiently transfer the cells to the target tissue, to keep them alive once engrafted and to allow them to spatially organize in such a way that they can contribute to the contractile function of the heart.

Embryonic stem cells for severe heart failure: why and how?

The experience accumulated in cardiac cell therapy suggests that regeneration of extensively necrotic myocardial areas is unlikely to be achieved by the sole paracrine effects of the grafted cells but rather requires the conversion of these cells into cardiomyocytes featuring the capacity to substitute for those which have been irreversibly lost. In this setting, the use of human pluripotent embryonic stem cells has a strong rationale. The experimental results obtained in animal models of myocardial infarction are encouraging. However, the switch to clinical applications still requires to address some critical issues, among which the optimization of the cardiac specification of the embryonic stem cells, the purification of the resulting progenitor cells so as to graft a purified population devoid from any contamination by residual pluripotent cells which carry the risk of tumorigenesis, and the control of the expected allogeneic rejection by clinically acceptable methods. If the solution to these problems is a prerequisite, the therapeutic success of this approach will also depend on the capacity to efficiently transfer the cells to the target tissue, to keep them alive once engrafted, and to allow them to spatially organize in such a way that they can contribute to the contractile function of the heart.

Amniotic fluid-derived stem cells in regenerative medicine research

The stem cells isolated from amniotic fluid present an exciting possible contribution to the field of regenerative medicine and amniotic fluid-derived stem (AFS) cells have significant potential for research and therapeutic applications. AFS cells are multipotent, showing the ability to differentiate into cell types from all three embryonic germ layers. They express both embryonic and adult stem cell markers, expand extensively without feeder cells, double in 36 h, and are not tumorigenic. The AFS cells can be maintained for over 250 population doublings and preserve their telomere length and a normal karyotype. They differentiate easily into specific cell lineages and do not require human embryo tissue for their isolation, thus avoiding the current controversies associated with the use of human embryonic stem (ES) cells. The discovery of the AFS cells has been recent, and a great deal of work remains to be performed on the characterization and use of these cells. This review describes the various differentiated lineages that AFS cells can form and the future of these promising new stem cells in regenerative medicine research.

In vitro and in vivo cardiomyogenic differentiation of amniotic fluid stem cells

Cell therapy has developed as a complementary treatment for myocardial regeneration. While both autologous and allogeneic uses have been advocated, the ideal candidate has not been identified yet. Amniotic fluid-derived stem (AFS) cells are potentially a promising resource for cell therapy and tissue engineering of myocardial injuries. However, no information is available regarding their use in an allogeneic context. c-kit-sorted, GFP-positive rat AFS (GFP-rAFS) cells and neonatal rat cardiomyocytes (rCMs) were characterized by cytocentrifugation and flow cytometry for the expression of mesenchymal, embryonic and cell lineage-specific antigens. The activation of the myocardial gene program in GFP-rAFS cells was induced by co-culture with rCMs. The stem cell differentiation was evaluated using immunofluorescence, RT-PCR and single cell electrophysiology. The in vivo potential of Endorem-labeled GFP-rAFS cells for myocardial repair was studied by transplantation in the heart of animals with ischemia/reperfusion injury (I/R), monitored by magnetic resonance imaging (MRI). Three weeks after injection a small number of GFP-rAFS cells acquired an endothelial or smooth muscle phenotype and to a lesser extent CMs. Despite the low GFP-rAFS cells count in the heart, there was still an improvement of ejection fraction as measured by MRI. rAFS cells have the in vitro propensity to acquire a cardiomyogenic phenotype and to preserve cardiac function, even if their potential may be limited by poor survival in an allogeneic setting.

Stem cell therapy for chronic heart failure: lessons from a 15-year experience

Although cell therapy has entered the clinical arena since 2000, its benefits are still controversial. This is partly due to a shift of the whole paradigm from the mere provision of new cells intended to replenish the pool of dead cardiomyocytes to the exploitation of the cell's paracrine effects to activate host-associated cytoprotective signalling pathways, particularly those involved in angiogenesis, prevention of apoptosis and possibly recruitment of endogenous cells capable to mature into functional cardiomyocytes. This review will discuss how these two basic mechanisms (direct donor cell-derived myocardial regeneration versus paracrine signalling) underlie the rational selection of cells in light of the target clinical indication, with a particular focus on chronic heart failure, and will emphasize the importance of optimizing cell delivery and survival to fully exploit the potential benefits of this novel approach to acute and chronic heart diseases.

Adipose-derived stromal cells: Their identity and uses in clinical trials, an update

In adults, adipose tissue is abundant and can be easily sampled using liposuction. Largely involved in obesity and associated metabolic disorders, it is now described as a reservoir of immature stromal cells. These cells, called adipose-derived stromal cells (ADSCs) must be distinguished from the crude stromal vascular fraction (SVF) obtained after digestion of adipose tissue. ADSCs share many features with mesenchymal stem cells derived from bone marrow, including paracrine activity, but they also display some specific features, including a greater angiogenic potential. Their angiogenic properties as well as their paracrine activity suggest a putative tumor-promoting role for ADSCs although contradictory data have been published on this issue. Both SVF cells and ADSCs are currently being investigated in clinical trials in several fields (chronic inflammation, ischemic diseases, etc.). Apart from a phase III trial on the treatment of fistula, most of these are in phase I and use autologous cells. In the near future, the end results of these trials should provide a great deal of data on the safety of ADSC use.

[Use of adipose tissue in regenerative medicine]

Adipose tissue is abundant and well known for its involvement in obesity and associated metabolic disorders. Its uses in regenerative medicine recently attracted many investigators, as large amounts of this tissue can be easily obtained using liposuction and it contains several populations of immature cells. The largest pool of such cells corresponds to immature stromal cells, called adipose-derived stromal cells (ADSCs). These cells are purified after proteolytic digestion of adipose tissue and selection by an adherent step. ADSCs display many common features with mesenchymal stem cells derived from bone marrow, including paracrine activity, but with some specific features, among which a greater angiogenic potential. This potential is now investigating at clinical level to treat critical ischemic hindlimb by autologous cells. Other potentials are also investigated and the treatment of fistula associated or not with Crohn's disease is reaching now phase III level.

Distinction between two populations of islet-1-positive cells in hearts of different murine strains

Islet-1 expression identifies populations of progenitor cells in embryonic, fetal, and newborn murine hearts that are able to give rise to all cardiac cell lineages ex vivo and in vivo. Using systematic immunohistochemistry, we investigated whether islet-1-positive cells are present in adult mouse heart from the perspective of their potential therapeutic utility. The presence, localization, and nature of islet-1-positive cells were assessed in mice of different strains, ages, and conditions. Islet-1-positive cells were present in mouse heart from postnatal day 1 to young adulthood. Depending on the strain, these cells were organized in either 1 or 2 types of clusters localized to restricted areas, at a distance of 6%-35% of the heart length from the base. The first type of cluster was present in all strains and consisted of neural crest-derived cells that formed cardiac ganglia. The number of cells remained stable (a few hundred) from neonatal up to adult ages, and variations were noted between strains regarding their long-term persistency. The second type of cluster was essentially present in 129SvJ or Balb/C strains and absent from the other strains tested (C57BL/6J, C3H, SJL). It consisted of cells expressing highly ordered sarcomeric actin, consistent with their having cardiomyocyte identity. These cells disappeared in animals older than 4 months. Neither the number nor the type of islet-1-positive cells varied with time in a mouse model of dilated cardiomyopathy. Our studies demonstrate that islet-1-positive cells are relatively few in number in adult murine heart, being localized in restricted and rather inaccessible areas, and can represent both neural crest and cardiomyocyte lineages.

Control of autocrine and paracrine myocardial signals: an emerging therapeutic strategy in heart failure

A growing body of evidence supports the hypothesis that autocrine and paracrine mechanisms, mediated by factors released by the resident cardiac cells, could play an essential role in the reparative process of the failing heart. Such signals may influence the function of cardiac stem cells via several mechanisms, among which the most extensively studied are cardiomyocyte survival and angiogenesis. Moreover, besides promoting cytoprotection and angiogenesis, paracrine factors released by resident cardiac cells may alter cardiac metabolism and extracellular matrix turnover, resulting in more favorable post-injury remodeling. It is reasonable to believe that critical intracellular signals are activated and modulated in a temporal and spatial manner exerting different effects, overall depending on the microenvironment changes present in the failing myocardium. The recent demonstration that chemically, mechanically or genetically activated cardiac cells may release peptides to protect tissue against ischemic injury provides a potential route to achieve the delivery of specific proteins produced by these cells for innovative pharmacological regenerative therapy of the heart. It is important to keep in mind that therapies currently used to treat heart failure (HF) and leading to improvement of cardiac function fail to induce tissue repair/regeneration. As a matter of facts, if specific autocrine/paracrine cell-derived factors that improve cardiac function will be identified, pharmacological-based therapy might be more easily translated into clinical benefits than cell-based therapy. This review will focus on the recent development of potential pharmacologic targets to promote and drive at molecular level the cardiac repair/regeneration in HF.

Implantation of mouse embryonic stem cell-derived cardiac progenitor cells preserves function of infarcted murine hearts

Stem cell transplantation holds great promise for the treatment of myocardial infarction injury. We recently described the embryonic stem cell-derived cardiac progenitor cells (CPCs) capable of differentiating into cardiomyocytes, vascular endothelium, and smooth muscle. In this study, we hypothesized that transplanted CPCs will preserve function of the infarcted heart by participating in both muscle replacement and neovascularization. Differentiated CPCs formed functional electromechanical junctions with cardiomyocytes in vitro and conducted action potentials over cm-scale distances. When transplanted into infarcted mouse hearts, CPCs engrafted long-term in the infarct zone and surrounding myocardium without causing teratomas or arrhythmias. The grafted cells differentiated into cross-striated cardiomyocytes forming gap junctions with the host cells, while also contributing to neovascularization. Serial echocardiography and pressure-volume catheterization demonstrated attenuated ventricular dilatation and preserved left ventricular fractional shortening, systolic and diastolic function. Our results demonstrate that CPCs can engraft, differentiate, and preserve the functional output of the infarcted heart.

Cardiac cell therapy: lessons from clinical trials

Cardiac cell therapy has now been in clinical use since 10 years. Both autologous skeletal myoblasts and bone marrow-derived different cell subsets (mononuclear cells, hematopoietic progenitors, mesenchymal stem cells) have been investigated in different settings (acute myocardial infarction, refractory angina and chronic heart failure). Despite the huge variability in cell processing techniques, dosing, timing of delivery and route for cell transfer, some lessons can yet be drawn, primarily from randomized controlled trials and summarized as follows: Techniques used for cell preparation are reasonably well controlled although better standardization and improvement in scale-up procedures remain necessary; cell therapy is overall safe, with the caveat of ventricular arrhythmias which still require careful scrutinization; the cell type needs to be tailored to the primary clinical indication, whereas the paracrine effects of bone marrow cells may be therapeutically efficacious for limitation of remodelling or relief of angina, only cells endowed with a true cardiomyogenic differentiation potential are likely to effect regeneration of chronic scars; autologous cells are primarily limited by their variable and unpredictable functionality, thereby calling attention to banked, consistent and readily available allogeneic cell products provided the immunological issues inherent in their use can be satisfactorily addressed; regardless of the cell type, a meaningful and sustained therapeutic benefit is unlikely to occur until cell transfer and survival techniques are improved to allow greater engraftment rates; and trial end points probably need to be reassessed to focus on mechanistic issues or hard end points depending on whether new or already extensively used cells are investigated. Hopefully, these lessons may serve as a building block whose incorporation in the design of second-generation trials will help making them more clinically successful. This article is part of a special issue entitled, "Cardiovascular Stem Cells Revisited".

General overview of the Sixth International Symposium on Stem Cell Therapy and Cardiovascular Innovations

Being one of the main stem cell therapy meetings of the year, the Sixth International Symposium on Stem Cell Therapy and Cardiovascular Innovations was held on April 23rd-24th, 2009, at the Auditorium of the High Council of Scientific Research of Spain (CSIC) in Madrid. Gathering the most prestigious basic researchers and clinical experts in the field of cardiovascular regenerative medicine, the aim of the meeting was to discuss the available evidence and the recent contributions from preclinical investigators, cardiologists, and cardiac surgeons in a participative translational fashion. The role of young "clinician scientists" was reinforced with a special poster session and three awards. The main conclusions of the symposium were (1) that standardization, larger clinical trials, and true translational research are needed, and (2) that new-allogeneic-stem cell products, biotechnological devices, and cell-based bioartificial organs are potentially exciting options for the future.

A strategy for single nucleotide polymorphism analysis of chimerism for somatic cell therapy

BACKGROUND AIMS

Chimerism is an important outcome measure in hematopoietic cell transplantation as well as somatic cell therapy. Commonly used methods to estimate chimerism are restricted by either gender or inefficient sensitivity. In principle, real-time polymerase chain reaction (PCR)-based assays can be used to assess single nucleotide polymorphisms (SNP), which are a vast resource of molecular markers, and such assays demonstrate a substantially higher sensitivity (0.001%), but the specificity is unclear because of a low-level signal from mismatched sequences.

METHODS

In this study, we cloned 14 pairs of SNP selected from the SNP HapMap database and examined the specificity and sensitivity of their detection by real-time PCR using two primer/fluorescent probe pairs to allow genotyping of the two possible variant alleles. Clinical donor-recipient pairs from 18 families were used to explore the efficacy of using SNP assays to measure chimerism.

RESULTS

We found that the polymorphic nucleotide influences the ability to distinguish the signal generated by the target and mismatched sequences. Moreover, the specific fluorescent reporter probe can affect the difference in signal intensity between the target and mismatched sequences. Real-time PCR SNP assays can attain a sensitivity of 0.1-0.5% with 100% specificity. When comparing possible clinical donor-recipient pairs, we found an average 3.3 out of 14 SNP were informative.

CONCLUSIONS

By optimal selection of the polymorphic sequences and fluorescent reporter, the real-time PCR SNP assay is superior to the short-tandem repeat chimerism assay and broadly applicable. This strategy may be applied in future clinical trials of bone marrow cell therapy.

Results of intracoronary stem cell therapy after acute myocardial infarction

To assess the effect of autologous bone-marrow cell (BMC) therapy in patients with acute myocardial infarction in a rigorous double-blind, randomized, placebo-controlled trial. Patients with reperfusion >6 hours after symptom onset were randomly assigned in a 2:1 ratio to receive intracoronary BMC or placebo therapy 5 to 7 days after symptom onset. The patients were stratified according to age, acute myocardial infarction localization, and left ventricular (LV) function. Rigorous double-blinding was ensured using autologous erythrocytes for the placebo preparation that was visually indistinguishable from the active treatment. Serial cardiac magnetic resonance imaging studies were performed before study therapy and after 1, 3, and 6 months. The primary end point was the difference in the LV ejection fraction from baseline to 6 months. The secondary end points included changes in the LV end-diastolic and end-systolic volume indexes and infarct size. A total of 42 patients were enrolled (29 in the BMC group and 13 in the placebo group) in the integrated pilot phase. A mean of 381 x 10(6) mononuclear BMCs were administered. The baseline clinical and cardiac magnetic resonance imaging parameters did not differ. Compared to baseline, the difference in LV ejection fraction for the placebo group versus BMC group was 1.7 +/- 6.4% versus -0.9 +/- 5.5% at 1 month, 3.1 +/- 6.0% versus 1.9 +/- 4.3% at 3 months, and 5.7 +/- 8.4% versus 1.8 +/- 5.3% at 6 months (primary end point; not significant). No difference was found in the secondary end points between the 2 groups, including changes in infarct size or LV end-diastolic and end-systolic volume indexes. In conclusion, in this rigorous double-blind, randomized, placebo-controlled trial, we did not observe an evidence for a positive effect for intracoronary BMC versus placebo therapy with respect to LV ejection fraction, LV volume indexes, or infarct size.

Drug delivery systems: Advanced technologies potentially applicable in personalized treatments

Advanced drug delivery systems (DDS) present indubitable benefits for drug administration. Over the past three decades, new approaches have been suggested for the development of novel carriers for drug delivery. In this review, we describe general concepts and emerging research in this field based on multidisciplinary approaches aimed at creating personalized treatment for a broad range of highly prevalent diseases (e.g., cancer and diabetes). This review is composed of two parts. The first part provides an overview on currently available drug delivery technologies including a brief history on the development of these systems and some of the research strategies applied. The second part provides information about the most advanced drug delivery devices using stimuli-responsive polymers. Their synthesis using controlled-living radical polymerization strategy is described. In a near future it is predictable the appearance of new effective tailor-made DDS, resulting from knowledge of different interdisciplinary sciences, in a perspective of creating personalized medical solutions.

Bone marrow mononuclear stem cells: potential in the treatment of myocardial infarction

Despite advances in the management of myocardial infarction, congestive heart failure following myocardial infarction continues to be a major worldwide medical problem. Mononuclear cells from bone marrow are currently being studied as potential candidates for cell-based therapy to repair and regenerate damaged myocardium, with mixed results. The success of this strategy requires structural repair through both cardiomyogenesis and angiogenesis but also functional repair. However, pre-clinical and clinical studies with the intracoronary administration of cells indicate limited cardiomyogenesis and cell survival, controversial functional benefit and suggest paracrine effects mediated by the administered cells. Further investigations for optimizing therapeutic benefit focus on the requirement for stable cell engraftment and the involvement of cytokines in this process. This includes a large and varied range of strategies including cell or heart pre-treatment, tissue engineering and protein therapy. Although cell-based therapy holds promise in the future treatment of myocardial infarction, its current use is significantly hampered by biological and technological challenges.

Induced pluripotent stem cells: advances to applications

Induced pluripotent stem cell (iPS) technology has enriched the armamentarium of regenerative medicine by introducing autologous pluripotent progenitor pools bioengineered from ordinary somatic tissue. Through nuclear reprogramming, patient-specific iPS cells have been derived and validated. Optimizing iPS-based methodology will ensure robust applications across discovery science, offering opportunities for the development of personalized diagnostics and targeted therapeutics. Here, we highlight the process of nuclear reprogramming of somatic tissues that, when forced to ectopically express stemness factors, are converted into bona fide pluripotent stem cells. Bioengineered stem cells acquire the genuine ability to generate replacement tissues for a wide-spectrum of diseased conditions, and have so far demonstrated therapeutic benefit upon transplantation in model systems of sickle cell anemia, Parkinson’s disease, hemophilia A, and ischemic heart disease. The field of regenerative medicine is therefore primed to adopt and incorporate iPS cell-based advancements as a next generation stem cell platforms.

COMPARE-AMI trial: comparison of intracoronary injection of CD133+ bone marrow stem cells to placebo in patients after acute myocardial infarction and left ventricular dysfunction: study rationale and design

Stem cell therapy has emerged as a promising approach to improve healing of the infarcted myocardium, to treat or prevent cardiac failure, and to restore lost cardiac function. Despite initial excitement, recent clinical trials using nonhomogenous human stem cells preparations showed variable results, raising concerns about the best cell type to transplant. Selected CD133(+) hematopoietic stem cells are promising candidate cells with great potential. COMPARE-acute myocardial infarction (AMI) study is a phase II, randomized, double-blind, placebo-controlled trial evaluating the safety and effectiveness of intracoronary CD133(+)-enriched hematopoietic bone marrow stem cells in patients with acute myocardial infarction and persistent left ventricular dysfunction. Patients who underwent successful percutaneous coronary intervention and present a persistent left ventricular ejection fraction <50% will be eligible to have bone marrow aspiration and randomized for intracoronary injection of selected CD 133(+) bone marrow cells vs placebo. The primary end point is a composite of a safety and efficacy end points evaluating the change at 4 months in the coronary atherosclerotic burden progression proximal and distal to the coronary stent in the infarct related artery; and the change in global left ventricular ejection fraction at 4 months relative to baseline as measured by magnetic resonance imaging. The secondary end point will be the occurrence of a major adverse cardiac event. To date, 14 patients were successfully randomized and treated without any protocol-related complication. COMPARE-AMI trial will help identify the effect of a selected population of the bone marrow stem cells on cardiac recovery of infarcted myocardium.

Cardiac renewing: interstitial Cajal-like cells nurse cardiomyocyte progenitors in epicardial stem cell niches

Recent studies suggested that various cell lineages exist within the subepicardium and we supposed that this area could host cardiac stem cell niches (CSCNs). Using transmission electron microscopy, we have found at least 10 types of cells coexisting in the subepicardium of normal adult mice: adipocytes, fibroblasts, Schwann cells and nerve fibres, isolated smooth muscle cells, mast cells, macrophages, lymphocytes, interstitial Cajal-like cells (ICLCs) and cardiomyocytes progenitors (CMPs). The latter cells, sited in the area of origin of coronary arteries and aorta, showed typical features of either very immature or developing cardiomyocytes. Some of these cells were connected to each other to form columns surrounded by a basal lamina and embedded in a cellular network made by ICLCs. Complex intercellular communication occurs between the ICLCs and CMPs through electron-dense nanostructures or through shed vesicles. We provide here for the first time the ultrastructural description of CSCN in the adult mice myocardium, mainly containing ICLCs and CMPs. The existence of resident CMPs in different developmental stages proves that cardiac renewing is a continuous process. We suggest that ICLCs might act as supporting nurse cells of the cardiac niches and may be responsible for activation, commitment and migration of the stem cells out of the niches. Briefly, not only resident cardiac stem cells but also ICLCs regulate myocyte turnover and contribute to both cardiac cellular homeostasis and endogenous repair/remodelling after injuries.