Induced pluripotent stem (iPS) cells repair and regenerate infarcted myocardium

Transplanted induced pluripotent stem cells mitigate oxidative stress and improve cardiac function through the Akt cell survival pathway in diabetic cardiomyopathy

Recent evidence suggests transplanted stem cells improve left ventricular function in diabetic induced cardiomyopathy (DICM). However, little is known about the mechanisms by which induced pluripotent stem (iPS) cells or factors released from these cells inhibit adverse cardiac remodeling in DICM. The present study was designed to determine molecular mediators and pathways regulated by transplanted iPS cells and their conditioned media (CM) in DICM. Animals were divided into four experimental groups such as control, streptozotocin (STZ), STZ+iPS-CM, and STZ+iPS cells. Experimental diabetes was induced in C57BL/6 mice by intraperitoneal STZ injections (100 mg/kg body weight for 2 consecutive days). Following STZ injections, iPS cells or CM was given intravenously for 3 consecutive days. Animals were humanely killed, and hearts were harvested at D14. Animals transplanted with iPS cells or CM demonstrated a significant reduction in apoptosis, mediated by Akt upregulation and ERK1/2 downregulation, and inhibition of interstitial fibrosis via MMP-9 suppression compared with the STZ group. Oxidative stress was significantly hindered in iPS cell and CM groups as evidenced by diminished pro-oxidant expression and enhanced antioxidant (catalase and MnSOD) concentration. Echocardiography data suggest a significant improvement in cardiac function in cells and CM groups in comparison to STZ. In conclusion, our data strongly suggest that iPS cells and CM attenuate oxidative stress and associated apoptosis and fibrosis. Moreover, we also suggest that increased antioxidant levels, decreased adverse cardiac remodeling, and improved cardiac function is mediated by iPS CM and cells in DICM through multiple autocrine and paracrine mechanisms.

Intramyocardial Injection of Pig Pluripotent Stem Cells Improves Left Ventricular Function and Perfusion: A Study in a Porcine Model of Acute Myocardial Infarction

Induced pluripotent stem (iPS) cells have the potential to differentiate to various types of cardiovascular cells to repair an injured heart. The potential therapeutic benefits of iPS cell based treatment have been established in small-animal models of myocardial infarction (MI). We hypothesize that porcine iPS (piPS) cell transplantation may be an effective treatment for MI. After a 90-minute occlusion of the left anterior descending artery in a porcine model, undifferentiated piPS cells or PBS were injected into the ischemic myocardium. Cardiac function, myocardial perfusion and cell differentiation were investigated. One week after piPS cell delivery, global left ventricular ejection fraction (LVEF) significantly decreased in both the iPS group and the PBS group compared to the Sham group (p<0.05, respectively). Six weeks after piPS cell delivery, LVEF of the iPS group significantly improved compared to the PBS group (56.68% vs. 50.93%, p = 0.04) but was still lower than the Sham group. Likewise, the piPS cell transplantation improved the regional perfusion compared to the PBS injection (19.67% vs. 13.67%, p = 0.02). The infarct area was significantly smaller in the iPS group than the PBS group (12.04% vs. 15.98% p = 0.01). PiPS cells engrafted into the myocardium can differentiate into vessel cells, which result in increased formation of new vessels in the infarcted heart. Direct intramyocardial injection of piPS cells can decrease infarct size and improve left ventricular function and perfusion for an immunosuppressed porcine AMI model.

Inactivation of Klf5 by zinc finger nuclease downregulates expression of pluripotent genes and attenuates colony formation in embryonic stem cells

Recent studies suggest that Klf5 is required to maintain embryonic stem (ES) cells in an undifferentiated state. However, whether Klf5 can be inactivated by novel fusion technology of zinc finger nucleases (ZFN) has never before been examined. Therefore, we used ZFN technology to target the Klf5 gene in mouse ES cells, and examined the effects of the Klf5 gene on the expression of pluripotency-related genes, Oct3/4, Nanog, and Sox2 and on the self-renewal of ES cells. In Klf5-ZFN-transfected cells, expression of the Klf5 mRNA was downregulated by ~80% compared to the control. Furthermore, expression of the Oct3/4 and Nanog mRNAs was significantly decreased in the Klf5-ZFN-targeted cells. RT-PCR analysis, however, showed no significant change in the level of Sox2 mRNA, but a decreased trend was evident in the Klf5-ZFN-targeted cells. Moreover, we observed the spontaneous differentiation of Klf5-ZFN-transfected cells and quantitative analysis revealed a significant decrease in colony formation in Klf5-ZFN-transfected cells. In conclusion, our data suggest that ZFN methodology is an effective approach to target the Klf5 gene and that Klf5 plays an important role in the maintenance of ES cell self-renewal.

Induced pluripotent stem cell intervention rescues ventricular wall motion disparity, achieving biological cardiac resynchronization post-infarction

Dyssynchronous myocardial motion aggravates cardiac pump function. Cardiac resynchronization using pacing devices is a standard-of-care in the management of heart failure. Post-infarction, however, scar tissue formation impedes the efficacy of device-based therapy. The present study tests a regenerative approach aimed at targeting the origin of abnormal motion to prevent dyssynchronous organ failure. Induced pluripotent stem (iPS) cells harbour a reparative potential, and were here bioengineered from somatic fibroblasts reprogrammed with the stemness factors OCT3/4, SOX2, KLF4, and c-MYC. In a murine infarction model, within 30 min of coronary ligation, iPS cells were delivered to mapped infarcted areas. Focal deformation and dysfunction underlying progressive heart failure was resolved prospectively using speckle-tracking imaging. Tracked at high temporal and spatial resolution, regional iPS cell transplantation restored, within 10 days post-infarction, the contractility of targeted infarcted foci and nullified conduction delay in adjacent non-infarcted regions. Local iPS cell therapy, but not delivery of parental fibroblasts or vehicle, prevented or normalized abnormal strain patterns correcting the decrease in peak strain, disparity of time-to-peak strain, and pathological systolic stretch. Focal benefit of iPS cell intervention translated into improved left ventricular conduction and contractility, reduced scar, and reversal of structural remodelling, protecting from organ decompensation. Thus, in ischaemic cardiomyopathy, targeted iPS cell transplantation synchronized failing ventricles, offering a regenerative strategy to achieve biological resynchronization.

Systematic Review of Induced Pluripotent Stem Cell Technology as a Potential Clinical Therapy for Spinal Cord Injury

Transplantation therapies aimed at repairing neurodegenerative and neuropathological conditions of the central nervous system (CNS) have utilized and tested a variety of cell candidates, each with its own unique set of advantages and disadvantages. The use and popularity of each cell type is guided by a number of factors including the nature of the experimental model, neuroprotection capacity, the ability to promote plasticity and guided axonal growth, and the cells' myelination capability. The promise of stem cells, with their reported ability to give rise to neuronal lineages to replace lost endogenous cells and myelin, integrate into host tissue, restore functional connectivity, and provide trophic support to enhance and direct intrinsic regenerative ability, has been seen as a most encouraging step forward. The advent of the induced pluripotent stem cell (iPSC), which represents the ability to “reprogram” somatic cells into a pluripotent state, hails the arrival of a new cell transplantation candidate for potential clinical application in therapies designed to promote repair and/or regeneration of the CNS. Since the initial development of iPSC technology, these cells have been extensively characterized in vitro and in a number of pathological conditions and were originally reported to be equivalent to embryonic stem cells (ESCs). This review highlights emerging evidence that suggests iPSCs are not necessarily indistinguishable from ESCs and may occupy a different “state” of pluripotency with differences in gene expression, methylation patterns, and genomic aberrations, which may reflect incomplete reprogramming and may therefore impact on the regenerative potential of these donor cells in therapies. It also highlights the limitations of current technologies used to generate these cells. Moreover, we provide a systematic review of the state of play with regard to the use of iPSCs in the treatment of neurodegenerative and neuropathological conditions. The importance of balancing the promise of this transplantation candidate in the light of these emerging properties is crucial as the potential application in the clinical setting approaches. The first of three sections in this review discusses (A) the pathophysiology of spinal cord injury (SCI) and how stem cell therapies can positively alter the pathology in experimental SCI. Part B summarizes (i) the available technologies to deliver transgenes to generate iPSCs and (ii) recent data comparing iPSCs to ESCs in terms of characteristics and molecular composition. Lastly, in (C) we evaluate iPSC-based therapies as a candidate to treat SCI on the basis of their neurite induction capability compared to embryonic stem cells and provide a summary of available in vivo data of iPSCs used in SCI and other disease models.

Epigenetics and cardiovascular disease

A commonly-assumed paradigm holds that the primary genetic determinant of cardiovascular disease resides within the DNA sequence of our genes. This paradigm can be challenged. For example, how do sequence changes in the non-coding region of the genome influence phenotype? Why are all diseases not shared between identical twins? Part of the answer lies in the fact that the environment or exogenous stimuli clearly influence disease susceptibility, but it was unclear in the past how these effects were signalled to the static DNA code. Epigenetics is providing a newer perspective on these issues. Epigenetics refers to chromatin-based mechanisms important in the regulation of gene expression that do not involve changes to the DNA sequence per se. The field can be broadly categorized into three areas: DNA base modifications (including cytosine methylation and cytosine hydroxymethylation), post-translational modifications of histone proteins, and RNA-based mechanisms that operate in the nucleus. Cardiovascular disease pathways are now being approached from the epigenetic perspective, including those associated with atherosclerosis, angiogenesis, ischemia-reperfusion damage, and the cardiovascular response to hypoxia and shear stress, among many others. With increasing interest and expanding partnerships in the field, we can expect new insights to emerge from epigenetic perspectives of cardiovascular health. This paper reviews the principles governing epigenetic regulation, discusses their presently-understood importance in cardiovascular disease, and considers the growing significance we are likely to attribute to epigenetic contributions in the future, as they provide new mechanistic insights and a host of novel clinical applications.

Stem cell transplantation as a therapy for cardiac fibrosis

Cardiac fibrosis is a fundamental constituent of most cardiac pathologies and represents the upshot of nearly all types of cardiac injury. Generally, fibrosis is a scarring process, characterized by accumulation of fibroblasts and deposition of increasing amounts of extracellular matrix (ECM) proteins in the myocardium. Therapeutic approaches that control fibroblast activity and evade maladaptive processes could represent a potential strategy to attenuate progression towards heart failure. Currently, cell therapy is actively perceived as an alternative to traditional pharmacological management of myocardial infarction (MI). The majority of the studies applying stem cell therapy following MI have demonstrated a decline in fibrosis. However, it was not clearly recognized whether the decline in cardiac fibrosis was due to replacement of dead cardiomyocytes or because of the direct effects of paracrine factors released from the transplanted stem cells on the ECM. Therefore, the main focus of this review is to discuss the impact of different types of stem cells on cardiac fibrosis and associated cardiac remodelling in a variety of experimental models of heart failure, particularly MI.

Heart extracellular matrix supports cardiomyocyte differentiation of mouse embryonic stem cells

We have evaluated the effect of heart extracellular matrix (ECM) on the cardiomyocyte differentiation of mouse embryonic stem cells (ES cells) using de-cellularized heart tissue. Several lines of evidence indicate that ECM plays significant roles in cell proliferation, cell death and differentiation, but role of ECM possessing a 3D structure in differentiation has not been studied in detail. We found that there are substantial differences in the quantitative protein profiles of ECM in SDS-treated heart tissue compared to that of liver tissue, as assessed by iTRAQ™ quantitative proteomics analysis. When mouse ES cells were cultured on thin (60 μm) sections of de-cellularized tissue, the expression of cardiac myosin heavy chain (cMHC) and cardiac troponin I (cTnI) was high in ES cells cultured on heart ECM compared with those cultured on liver ECM. In addition, the protein expression of cMHC and cTnI was detected in cells on heart ECM after 2 weeks, which was not detectable in cells on liver ECM. These results indicate that heart ECM plays a critical role in the cardiomyocyte differentiation of ES cells. We propose that tissue-specific ECM induced cell lineage specification through mechano-transduction mediated by the structure, elasticity and components of ECM.

Human pluripotent stem cell-derived cardiomyocytes: response to TTX and lidocain reveals strong cell to cell variability

Stem cell derived cardiomyocytes generated either from human embryonic stem cells (hESC-CMs) or human induced pluripotent stem cells (hiPSC-CMs) hold great promise for the investigation of early developmental processes in human cardiomyogenesis and future cell replacement strategies. We have analyzed electrophysiological properties of hESC-CMs (HES2) and hiPSC-CMs, derived from reprogrammed adult foreskin fibroblasts that have previously been found to be highly similar in terms of gene expression. In contrast to the similarity found in the expression profile we found substantial differences in action potentials (APs) and sodium currents at late stage (day 60) of in vitro differentiation with higher sodium currents in hiPSC-CMs. Sensitivity to lidocain was considerably reduced in hESC-CMs as compared to hiPSC-CMs, and the effect could not be explained by differences in beating frequency. In contrast, sensitivity to tetrodotoxin (TTX) was higher in hESC-CMs suggesting different contributions of TTX-sensitive and TTX-resistant sodium channels to AP generation. These data point to physiological differences that are not necessarily detected by genomics. We conclude that novel pharmacological screening-assays using hiPSC-CMs need to be applied with some caution.

Functional multipotency of stem cells: what do we need from them in the heart?

After more than ten years of human research in the field of cardiac regenerative medicine, application of stem cells in different phases of ischemic heart disease has come to age. Randomized clinical trials have demonstrated that stem cell therapy can improve cardiac recovery after the acute phase of myocardial ischemia and in patients with chronic ischemic heart disease, and several efficacy phase III trials with clinical endpoints are on their way. Nevertheless, a complete knowledge on the mechanisms of action of stem cells still remains elusive. Of the three main mechanisms by which stem cells could exert their benefit, paracrine signaling from the administered cells and stimulation of endogenous repair are nowadays the most plausible ones. However, in this review we will define and discuss the concept of stem cell potency and differentiation, will examine the evidence available, and will depict future directions of research.

Regenerating functional heart tissue for myocardial repair

Heart disease is one of the leading causes of death worldwide and the number of patients with the disease is likely to grow with the continual decline in health for most of the developed world. Heart transplantation is one of the only treatment options for heart failure due to an acute myocardial infarction, but limited donor supply and organ rejection limit its widespread use. Cellular cardiomyoplasty, or cellular implantation, combined with various tissue-engineering methods aims to regenerate functional heart tissue. This review highlights the numerous cell sources that have been used to regenerate the heart as well as cover the wide range of tissue-engineering strategies that have been devised to optimize the delivery of these cells. It will probably be a long time before an effective regenerative therapy can make a serious impact at the bedside.

Cell therapy in the heart

Cell therapy is emerging as a new strategy to circumvent the adverse effects of heart disease. Many experimental and clinical studies investigating the transplantation of cells into the injured myocardium have yielded promising results. Moreover, data from these reports show that transplanted stem cells can engraft within the myocardium, differentiate into major cardiac cell types, and improve cardiac function. However, results from clinical trials show conflicting results. These trials demonstrate significant improvements in cardiac function for up to 6 months. However, these improved functions were diminished when examined at 18 months. In this review, we will discuss the current literature available on cell transplantation, covering studies ranging from animal models to clinical trials.

Stem cell mediated cardiovascular repair

Recent increase in the interest in stem and progenitor cells may be attributed to their behavioural characteristics. A consensus has been reached that embryonic or adult stem cells have therapeutic potential. As cardiovascular health issues are still the major culprits in many developed countries, stem and progenitor cell driven approaches may give the clinicians a new arsenal to tackle many significant health issues. However, stem and progenitor cell mediated cardiovascular regeneration can be achieved via complex and dynamic molecular mechanisms involving a variety of cells, growth factors, cytokines, and genes. Functional contributions of transplanted cells on target organs and their survival are still critical problems waiting to be resolved. Moreover, the regeneration of contracting myocardial tissue has controversial results in human trials. Thus, moderately favourable clinical results should be interpreted carefully. Determining the behavioural programs, genetic and transcriptional control of stem cells, mechanisms that determine cell fate, and functional characteristics are the primary targets. In addition, ensuring the long-term follow-up of cells with efficient imaging techniques in human clinical studies may provide a resurgence of the initial enthusiasm, which has faded over time. Here, we provide a brief historical perspective on stem cell driven cardiac regeneration and discuss cardiac and vascular repair in the context of translational science.

Preconditioning approach in stem cell therapy for the treatment of infarcted heart

Nearly two decades of research in regenerative medicine have been focused on the development of stem cells as a therapeutic option for treatment of the ischemic heart. Given the ability of stem cells to regenerate the damaged tissue, stem-cell-based therapy is an ideal approach for cardiovascular disorders. Preclinical studies in experimental animal models and clinical trials to determine the safety and efficacy of stem cell therapy have produced encouraging results that promise angiomyogenic repair of the ischemically damaged heart. Despite these promising results, stem cell therapy is still confronted with issues ranging from uncertainty about the as-yet-undetermined "ideal" donor cell type to the nonoptimized cell delivery strategies to harness optimal clinical benefits. Moreover, these lacunae have significantly hampered the progress of the heart cell therapy approach from bench to bedside for routine clinical applications. Massive death of donor cells in the infarcted myocardium during acute phase postengraftment is one of the areas of prime concern, which immensely lowers the efficacy of the procedure. An overview of the published data relevant to stem cell therapy is provided here and the various strategies that have been adopted to develop and optimize the protocols to enhance donor stem cell survival posttransplantation are discussed, with special focus on the preconditioning approach.