Cardiac Stem Cells for Myocardial Regeneration: They Are Not Alone

Stem cell-based therapy for fibrotic diseases: mechanisms and pathways

Fibrosis is a pathological process, that could result in permanent scarring and impairment of the physiological function of the affected organ; this condition which is categorized under the term organ failure could affect various organs in different situations. The involvement of the major organs, such as the lungs, liver, kidney, heart, and skin, is associated with a high rate of morbidity and mortality across the world. Fibrotic disorders encompass a broad range of complications and could be traced to various illnesses and impairments; these could range from simple skin scars with beauty issues to severe rheumatologic or inflammatory disorders such as systemic sclerosis as well as idiopathic pulmonary fibrosis. Besides, the overactivation of immune responses during any inflammatory condition causing tissue damage could contribute to the pathogenic fibrotic events accompanying the healing response; for instance, the inflammation resulting from tissue engraftment could cause the formation of fibrotic scars in the grafted tissue, even in cases where the immune system deals with hard to clear infections, fibrotic scars could follow and cause severe adverse effects. A good example of such a complication is post-Covid19 lung fibrosis which could impair the life of the affected individuals with extensive lung involvement. However, effective therapies that halt or slow down the progression of fibrosis are missing in the current clinical settings. Considering the immunomodulatory and regenerative potential of distinct stem cell types, their application as an anti-fibrotic agent, capable of attenuating tissue fibrosis has been investigated by many researchers. Although the majority of the studies addressing the anti-fibrotic effects of stem cells indicated their potent capabilities, the underlying mechanisms, and pathways by which these cells could impact fibrotic processes remain poorly understood. Here, we first, review the properties of various stem cell types utilized so far as anti-fibrotic treatments and discuss the challenges and limitations associated with their applications in clinical settings; then, we will summarize the general and organ-specific mechanisms and pathways contributing to tissue fibrosis; finally, we will describe the mechanisms and pathways considered to be employed by distinct stem cell types for exerting anti-fibrotic events.

Large animal models for cardiac remuscularization studies: A methodological review

Myocardial infarction is the most common cause of heart failure, one of the most fatal non-communicable diseases worldwide. The disease could potentially be treated if the dead, ischemic heart tissues are regenerated and replaced with viable and functional cardiomyocytes. Pluripotent stem cells have proven the ability to derive specific and functional cardiomyocytes in large quantities for therapy. To test the remuscularization hypothesis, the strategy to model the disease in animals must resemble the pathophysiological conditions of myocardial infarction as in humans, to enable thorough testing of the safety and efficacy of the cardiomyocyte therapy before embarking on human trials. Rigorous experiments and in vivo findings using large mammals are increasingly important to simulate clinical reality and increase translatability into clinical practice. Hence, this review focus on large animal models which have been used in cardiac remuscularization studies using cardiomyocytes derived from human pluripotent stem cells. The commonly used methodologies in developing the myocardial infarction model, the choice of animal species, the pre-operative antiarrhythmics prophylaxis, the choice of perioperative sedative, anaesthesia and analgesia, the immunosuppressive strategies in allowing xenotransplantation, the source of cells, number and delivery method are discussed.

In Search of the Holy Grail: Stem Cell Therapy as a Novel Treatment of Heart Failure with Preserved Ejection Fraction

Heart failure, a leading cause of hospitalizations and deaths, is a major clinical problem. In recent years, the increasing incidence of heart failure with preserved ejection fraction (HFpEF) has been observed. Despite extensive research, there is no efficient treatment for HFpEF available. However, a growing body of evidence suggests stem cell transplantation, due to its immunomodulatory effect, may decrease fibrosis and improve microcirculation and therefore, could be the first etiology-based therapy of the disease. In this review, we explain the complex pathogenesis of HFpEF, delineate the beneficial effects of stem cells in cardiovascular therapy, and summarize the current knowledge concerning cell therapy in diastolic dysfunction. Furthermore, we identify outstanding knowledge gaps that may indicate directions for future clinical studies.

Cardiac inducing colonies halt fibroblast activation and induce cardiac/endothelial cells to move and expand via paracrine signaling

Myocardial fibrosis (MF), a common event that develops after myocardial infarction, initially is a reparative process but eventually leads to heart failure and sudden cardiac arrest. In MF, the infarct area is replaced by a collagenous-based scar induced by "excessive" collagen deposition from activated cardiac fibroblasts. The scar prevents ventricular wall thinning; however, over time it expands to noninfarcted myocardium. Therapies to prevent fibrosis include reperfusion, anti-fibrotic agents, and ACE inhibitors. Paracrine factor (PF)/stem cell research has recently gained significance as a therapy. We consistently find that cardiac inducing colonies (CiCs) (derived from human germline pluripotent stem cells) secrete PFs at physiologically relevant concentrations that suppress cardiac fibroblast activation and excessive extracellular matrix protein secretion. These factors also affect human cardiomyocytes and endothelial cells by inducing migration/proliferation of both populations into a myocardial wound model. Finally, CiC factors modulate matrix turnover and proinflammation. Taking the results together, we show that CiCs could help tip the balance from fibrosis toward repair.

Atypically Shaped Cardiomyocytes (ACMs): The Identification, Characterization and New Insights into a Subpopulation of Cardiomyocytes

In the adult mammalian heart, no data have yet shown the existence of cardiomyocyte-differentiable stem cells that can be used to practically repair the injured myocardium. Atypically shaped cardiomyocytes (ACMs) are found in cultures of the cardiomyocyte-removed fraction obtained from cardiac ventricles from neonatal to aged mice. ACMs are thought to be a subpopulation of cardiomyocytes or immature cardiomyocytes, most closely resembling cardiomyocytes due to their spontaneous beating, well-organized sarcomere and the expression of cardiac-specific proteins, including some fetal cardiac gene proteins. In this review, we focus on the characteristics of ACMs compared with ventricular myocytes and discuss whether these cells can be substitutes for damaged cardiomyocytes. ACMs reside in the interstitial spaces among ventricular myocytes and survive under severely hypoxic conditions fatal to ventricular myocytes. ACMs have not been observed to divide or proliferate, similar to cardiomyocytes, but they maintain their ability to fuse with each other. Thus, it is worthwhile to understand the role of ACMs and especially how these cells perform cell fusion or function independently in vivo. It may aid in the development of new approaches to cell therapy to protect the injured heart or the clarification of the pathogenesis underlying arrhythmia in the injured heart.

Tailoring Cardiac Synthetic Transcriptional Modulation Towards Precision Medicine

Molecular and genetic differences between individual cells within tissues underlie cellular heterogeneities defining organ physiology and function in homeostasis as well as in disease states. Transcriptional control of endogenous gene expression has been intensively studied for decades. Thanks to a fast-developing field of single cell genomics, we are facing an unprecedented leap in information available pertaining organ biology offering a comprehensive overview. The single-cell technologies that arose aided in resolving the precise cellular composition of many organ systems in the past years. Importantly, when applied to diseased tissues, the novel approaches have been immensely improving our understanding of the underlying pathophysiology of common human diseases. With this information, precise prediction of regulatory elements controlling gene expression upon perturbations in a given cell type or a specific context will be realistic. Simultaneously, the technological advances in CRISPR-mediated regulation of gene transcription as well as their application in the context of epigenome modulation, have opened up novel avenues for targeted therapy and personalized medicine. Here, we discuss the fast-paced advancements during the recent years and the applications thereof in the context of cardiac biology and common cardiac disease. The combination of single cell technologies and the deep knowledge of fundamental biology of the diseased heart together with the CRISPR-mediated modulation of gene regulatory networks will be instrumental in tailoring the right strategies for personalized and precision medicine in the near future. In this review, we provide a brief overview of how single cell transcriptomics has advanced our knowledge and paved the way for emerging CRISPR/Cas9-technologies in clinical applications in cardiac biomedicine.

Regenerative strategies for the consequences of myocardial infarction: Chronological indication and upcoming visions

Heart muscle injury and an elevated troponin level signify myocardial infarction (MI), which may result in defective and uncoordinated segments, reduced cardiac output, and ultimately, death. Physicians apply thrombolytic therapy, coronary artery bypass graft (CABG) surgery, or percutaneous coronary intervention (PCI) to recanalize and restore blood flow to the coronary arteries, albeit they were not convincingly able to solve the heart problems. Thus, researchers aim to introduce novel substitutional therapies for regenerating and functionalizing damaged cardiac tissue based on engineering concepts. Cell-based engineering approaches, utilizing biomaterials, gene, drug, growth factor delivery systems, and tissue engineering are the most leading studies in the field of heart regeneration. Also, understanding the primary cause of MI and thus selecting the most efficient treatment method can be enhanced by preparing microdevices so-called heart-on-a-chip. In this regard, microfluidic approaches can be used as diagnostic platforms or drug screening in cardiac disease treatment. Additionally, bioprinting technique with whole organ 3D printing of human heart with major vessels, cardiomyocytes and endothelial cells can be an ideal goal for cardiac tissue engineering and remarkable achievement in near future. Consequently, this review discusses the different aspects, advancements, and challenges of the mentioned methods with presenting the advantages and disadvantages, chronological indications, and application prospects of various novel therapeutic approaches.

From Spheroids to Organoids: The Next Generation of Model Systems of Human Cardiac Regeneration in a Dish

Organoids are tiny, self-organized, three-dimensional tissue cultures that are derived from the differentiation of stem cells. The growing interest in the use of organoids arises from their ability to mimic the biology and physiology of specific tissue structures in vitro. Organoids indeed represent promising systems for the in vitro modeling of tissue morphogenesis and organogenesis, regenerative medicine and tissue engineering, drug therapy testing, toxicology screening, and disease modeling. Although 2D cell cultures have been used for more than 50 years, even for their simplicity and low-cost maintenance, recent years have witnessed a steep rise in the availability of organoid model systems. Exploiting the ability of cells to re-aggregate and reconstruct the original architecture of an organ makes it possible to overcome many limitations of 2D cell culture systems. In vitro replication of the cellular micro-environment of a specific tissue leads to reproducing the molecular, biochemical, and biomechanical mechanisms that directly influence cell behavior and fate within that specific tissue. Lineage-specific self-organizing organoids have now been generated for many organs. Currently, growing cardiac organoid (cardioids) from pluripotent stem cells and cardiac stem/progenitor cells remains an open challenge due to the complexity of the spreading, differentiation, and migration of cardiac muscle and vascular layers. Here, we summarize the evolution of biological model systems from the generation of 2D spheroids to 3D organoids by focusing on the generation of cardioids based on the currently available laboratory technologies and outline their high potential for cardiovascular research.

Cardiac Repair With Echocardiography-Guided Multiple Percutaneous Left Ventricular Intramyocardial Injection of hiPSC-CMs After Myocardial Infarction

Objective: We investigated the potency of cardiac repair based on echocardiography-guided multiple percutaneous left ventricular intramyocardial injection of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) after myocardial infarction (MI).

Methods: Mice with surgically induced MI were randomly divided into three groups (n = 8 in each group) and subjected to echocardiography-guided percutaneous left ventricular infarcted border injection of hiPSC-CMs (single dose; 10 μl 3 × 10⁵ cells) or repeated injections of hiPSC-CMs at post-MI weeks 1 and 2 (multiple doses). The sham group of animals underwent all surgical procedures necessary for MI induction except for ligation. Then 4 weeks after MI, heart function was measured with transthoracic echocardiography. Engraftment was evaluated through the detection of human-specific cardiac troponin T. Infarct size and collagen volume were calculated with Sirius Red/Fast Green staining. Angiogenesis was evaluated with isolectin B4 staining. Cardiac remodeling was evaluated from the cardiomyocyte minimal fiber diameter in the infarcted border zone. Apoptosis was detected via TdT-mediated dUTP Nick-End Labeling (TUNEL) staining in cardiomyocytes from the infarcted border zone.

Results: No mice died after echocardiography-guided percutaneous left ventricular intramyocardial injection. hiPSC-CMs were about nine-fold higher in the multiple-dose group at week 4 compared to the single-dose group. Multiple-dose transplantation was associated with significant improvement in left ventricular function, infarct size, angiogenesis, cardiac remodeling, and cardiomyocyte apoptosis.

Conclusion: Echocardiography-guided multiple percutaneous left ventricular intramyocardial injection is a feasible, satisfactory, repeatable, relatively less invasive, and effective method of delivering cell therapy. The delivery of hiPSC-CMs indicates a novel therapy for MI.

3D bioprinting of stem cell-laden cardiac patch: A promising alternative for myocardial repair

Stem cell-laden three-dimensional (3D) bioprinted cardiac patches offer an alternative and promising therapeutic and regenerative approach for ischemic cardiomyopathy by reversing scar formation and promoting myocardial regeneration. Numerous studies have reported using either multipotent or pluripotent stem cells or their combination for 3D bioprinting of a cardiac patch with the sole aim of restoring cardiac function by faithfully rejuvenating the cardiomyocytes and associated vasculatures that are lost to myocardial infarction. While many studies have demonstrated success in mimicking cardiomyocytes' behavior, improving cardiac function and providing new hope for regenerating heart post-myocardial infarction, some others have reported contradicting data in apparent ways. Nonetheless, all investigators in the field are speed racing toward determining a potential strategy to effectively treat losses due to myocardial infarction. This review discusses various types of candidate stem cells that possess cardiac regenerative potential, elucidating their applications and limitations. We also brief the challenges of and an update on the implementation of the state-of-the-art 3D bioprinting approach to fabricate cardiac patches and highlight different strategies to implement vascularization and augment cardiac functional properties with respect to electrophysiological similarities to native tissue.

Human iPS-derived pre-epicardial cells direct cardiomyocyte aggregation expansion and organization in vitro

Epicardial formation is necessary for normal myocardial morphogenesis. Here, we show that differentiating hiPSC-derived lateral plate mesoderm with BMP4, RA and VEGF (BVR) can generate a premature form of epicardial cells (termed pre-epicardial cells, PECs) expressing WT1, TBX18, SEMA3D, and SCX within 7 days. BVR stimulation after Wnt inhibition of LPM demonstrates co-differentiation and spatial organization of PECs and cardiomyocytes (CMs) in a single 2D culture. Co-culture consolidates CMs into dense aggregates, which then form a connected beating syncytium with enhanced contractility and calcium handling; while PECs become more mature with significant upregulation of UPK1B, ITGA4, and ALDH1A2 expressions. Our study also demonstrates that PECs secrete IGF2 and stimulate CM proliferation in co-culture. Three-dimensional PEC-CM spheroid co-cultures form outer smooth muscle cell layers on cardiac micro-tissues with organized internal luminal structures. These characteristics suggest PECs could play a key role in enhancing tissue organization within engineered cardiac constructs in vitro.

The authors form pre-epicardial cells (PECs) from hiPSC-derived lateral plate mesoderm on treating with BMP4, RA and VEGF, and co-culture these PECs with cardiomyocytes, inducing cardiomyocyte aggregation, proliferation and network formation with more mature structures and improved beating/contractility.

Direct Reprogramming Induces Vascular Regeneration Post Muscle Ischemic Injury

Reprogramming non-cardiomyocytes (non-CMs) into cardiomyocyte (CM)-like cells is a promising strategy for cardiac regeneration in conditions such as ischemic heart disease. Here, we used a modified mRNA (modRNA) gene delivery platform to deliver a cocktail, termed 7G-modRNA, of four cardiac-reprogramming genes—Gata4 (G), Mef2c (M), Tbx5 (T), and Hand2 (H)—together with three reprogramming-helper genes—dominant-negative (DN)-TGFβ, DN-Wnt8a, and acid ceramidase (AC)—to induce CM-like cells. We showed that 7G-modRNA reprogrammed 57% of CM-like cells in vitro. Through a lineage-tracing model, we determined that delivering the 7G-modRNA cocktail at the time of myocardial infarction reprogrammed ∼25% of CM-like cells in the scar area and significantly improved cardiac function, scar size, long-term survival, and capillary density. Mechanistically, we determined that while 7G-modRNA cannot create de novo beating CMs in vitro or in vivo, it can significantly upregulate pro-angiogenic mesenchymal stromal cells markers and transcription factors. We also demonstrated that our 7G-modRNA cocktail leads to neovascularization in ischemic-limb injury, indicating CM-like cells importance in other organs besides the heart. modRNA is currently being used around the globe for vaccination against COVID-19, and this study proves this is a safe, highly efficient gene delivery approach with therapeutic potential to treat ischemic diseases.

Stem Cells and Their Cardiac Derivatives for Cardiac Tissue Engineering and Regenerative Medicine

Significance: Heart failure is among the leading causes of morbidity worldwide with a 5-year mortality rate of ∼50%. Therefore, major efforts are invested to reduce heart damage upon injury or maintain and at best restore heart function. Recent Advances: In clinical trials, acellular constructs succeeded in improving cardiac function by stabilizing the infarcted heart. In addition, strategies utilizing stem-cell-derived cardiomyocytes have been developed to improve heart function postmyocardial infarction in small and large animal models. These strategies range from injection of cell-laden hydrogels to unstructured hydrogel-based and complex biofabricated cardiac patches. Importantly, novel methods have been developed to promote differentiation of stem-cell-derived cardiomyocytes to prevascularized cardiac patches. Critical Issues: Despite substantial progress in vascularization strategies for heart-on-the-chip technologies, little advance has been made in generating vascularized cardiac patches with clinically relevant dimensions. In addition, proper electrical coupling between engineered and host tissue to prevent and/or eliminate arrhythmia remains an unresolved issue. Finally, despite advanced approaches to include hierarchical structures in cardiac tissues, engineered tissues do not generate forces in the range of native adult cardiac tissue. Future Directions: It involves utilizing novel materials and advancing biofabrication strategies to generate prevascularized three-dimensional multicellular constructs of clinical relevant size; inclusion of hierarchical structures, electroconductive materials, and biologically active factors to enhance cardiomyocyte differentiation for optimized force generation and vascularization; optimization of bioreactor strategies for tissue maturation. Antioxid. Redox Signal. 35, 143-162.

Dystrophin Deficiency Causes Progressive Depletion of Cardiovascular Progenitor Cells in the Heart

Duchenne muscular dystrophy (DMD) is a devastating condition shortening the lifespan of young men. DMD patients suffer from age-related dilated cardiomyopathy (DCM) that leads to heart failure. Several molecular mechanisms leading to cardiomyocyte death in DMD have been described. However, the pathological progression of DMD-associated DCM remains unclear. In skeletal muscle, a dramatic decrease in stem cells, so-called satellite cells, has been shown in DMD patients. Whether similar dysfunction occurs with cardiac muscle cardiovascular progenitor cells (CVPCs) in DMD remains to be explored. We hypothesized that the number of CVPCs decreases in the dystrophin-deficient heart with age and disease state, contributing to DCM progression. We used the dystrophin-deficient mouse model (mdx) to investigate age-dependent CVPC properties. Using quantitative PCR, flow cytometry, speckle tracking echocardiography, and immunofluorescence, we revealed that young mdx mice exhibit elevated CVPCs. We observed a rapid age-related CVPC depletion, coinciding with the progressive onset of cardiac dysfunction. Moreover, mdx CVPCs displayed increased DNA damage, suggesting impaired cardiac muscle homeostasis. Overall, our results identify the early recruitment of CVPCs in dystrophic hearts and their fast depletion with ageing. This latter depletion may participate in the fibrosis development and the acceleration onset of the cardiomyopathy.

Stem cell-based therapies for cardiac diseases: The critical role of angiogenic exosomes

Finding effective treatments for cardiac diseases is among the hottest subjects in medicine; cell-based therapies have brought great promises for managing a broad range of life-threatening heart complications such as myocardial infarction. After clarifying the critical role of angiogenesis in tissue repair and regeneration, various stem/progenitor cell were utilized to accelerate the healing of injured cardiac tissue. Embryonic, fetal, adult, and induced pluripotent stem cells have shown the appropriate proangiogenic potential for tissue repair strategies. The capability of stem cells for differentiating into endothelial lineages was initially introduced as the primary mechanism involved in improving angiogenesis and accelerated heart tissue repair. However, recent studies have demonstrated the leading role of paracrine factors secreted by stem cells in advancing neo-vessel formation. Genetically modified stem cells are also being applied for promoting angiogenesis regarding their ability to considerably overexpress and secrete angiogenic bioactive molecules. Yet, conducting further research seems necessary to precisely identify molecular mechanisms behind the proangiogenic potential of stem cells, including the signaling pathways and regulatory molecules such as microRNAs. In conclusion, stem cells' pivotal roles in promoting angiogenesis and consequent improved cardiac healing and remodeling processes should not be ignored, especially in the case of stem cell-derived extracellular vesicles.

Acoustic Droplet Vitrification Method for High-Efficiency Preservation of Rare Cells

Cryopreservation is a key step for current translational medicine including reproductive medicine, regenerative medicine, and cell therapy. However, it is challenging to preserve rare cells for practical applications due to the difficulty in handling low numbers of cells as well as the lack of highly efficient and biocompatible preservation protocols. Here, we developed an acoustic droplet vitrification method for high-efficiency handling and preservation of rare cells. By employing an acoustic droplet ejection device, we can encapsulate rare cells into water-in-air droplets with a volume from ∼pL to ∼nL and deposit these cell-containing droplets into a droplet array onto a substrate. By incorporating a cooling system into the droplet array substrate, we can vitrify hundreds to thousands of rare cells at an ultrafast speed (about ∼2 s) based on the high surface to volume ratio of the droplets. By optimizing this method with three different cell lines (a human lung cancer cell line, A549 cells, a human liver cell line, L02 cells, and a mouse embryonic fibroblast cell line, 3T3-L1 cells), we developed an effective protocol with excellent cell viability (e.g., >85% for days, >70% for months), proliferation, and adhesion. As a proof-of-concept application, we demonstrated that our method can rapidly handle and efficiently preserve rare cells, highlighting its broad applications in species diversity, basic research, and clinical medicine.

Stem cell therapy in the heart: Biomaterials as a key route

Cardiovascular diseases are one of the main concerns, nowadays causing a high rate of mortality in the world. The majority of conventional treatment protects the heart from failure progression. As a novel therapeutic way, Regenerative medicine in the heart includes cellular and noncellular approaches. Despite the irrefutable privileges of noncellular aspects such as administration of exosomes, utilizing of miRNAs, and growth factors, they cannot reverse necrotic or ischemic myocardium, hence recruiting of stem cells to help regenerative therapy in the heart seems indispensable. Stem cell lineages are varied and divided into two main groups namely pluripotent and adult stem cells. Not only has each of which own regenerative capacity, benefits, and drawbacks, but their turnover also close correlates with the target organ and/or tissue as well as the stage and level of failure. In addition to inefficient tissue integration due to the defects in delivering methods and poor retention of transplanted cells, the complexity of the heart and its movement also make more rigorous the repair process. Hence, utilizing biomaterials can make a key route to tackle such obstacles. In this review, we evaluate some natural products which can help stem cells in regenerative medicine of the cardiovascular system.

The Potential Properties of Natural Compounds in Cardiac Stem Cell Activation: Their Role in Myocardial Regeneration

Cardiovascular diseases (CVDs), which include congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, and many other cardiac disorders, cause about 30% of deaths globally; representing one of the main health problems worldwide. Among CVDs, ischemic heart diseases (IHDs) are one of the major causes of morbidity and mortality in the world. The onset of IHDs is essentially due to an unbalance between the metabolic demands of the myocardium and its supply of oxygen and nutrients, coupled with a low regenerative capacity of the heart, which leads to great cardiomyocyte (CM) loss; promoting heart failure (HF) and myocardial infarction (MI). To date, the first strategy recommended to avoid IHDs is prevention in order to reduce the underlying risk factors. In the management of IHDs, traditional therapeutic options are widely used to improve symptoms, attenuate adverse cardiac remodeling, and reduce early mortality rate. However, there are no available treatments that aim to improve cardiac performance by replacing the irreversible damaged cardiomyocytes (CMs). Currently, heart transplantation is the only treatment being carried out for irreversibly damaged CMs. Hence, the discovery of new therapeutic options seems to be necessary. Interestingly, recent experimental evidence suggests that regenerative stem cell medicine could be a useful therapeutic approach to counteract cardiac damage and promote tissue regeneration. To this end, researchers are tasked with answering one main question: how can myocardial regeneration be stimulated? In this regard, natural compounds from plant extracts seem to play a particularly promising role. The present review will summarize the recent advances in our knowledge of stem cell therapy in the management of CVDs; focusing on the main properties and potential mechanisms of natural compounds in stimulating and activating stem cells for myocardial regeneration.

Effect of cellular and ECM aging on human iPSC-derived cardiomyocyte performance, maturity and senescence

Cardiovascular diseases are the leading cause of death worldwide and their occurrence is highly associated with age. However, lack of knowledge in cardiac tissue aging is a major roadblock in devising novel therapies. Here, we studied the effects of cell and cardiac extracellular matrix (ECM) aging on the induced pluripotent stem cell (iPSC)-derived cardiomyocyte cell state, function, as well as response to myocardial infarction (MI)-mimicking stress conditions in vitro. Within 3-weeks, young ECM promoted proliferation and drug responsiveness in young cells, and induced cell cycle re-entry, and protection against stress in the aged cells. Adult ECM improved cardiac function, while aged ECM accelerated the aging phenotype, and impaired cardiac function and stress defense machinery of the cells. In summary, we have gained a comprehensive understanding of cardiac aging and highlighted the importance of cell-ECM interactions. This study is the first to investigate the individual effects of cellular and environmental aging and identify the biochemical changes that occur upon cardiac aging.

Therapeutic advances in cardiac targeted drug delivery: from theory to practice

The most commonly used administration methods in clinics and life are oral administration, intravenous injection, and other systemic administration methods. Targeted administration must be an essential long-term development direction due to the limited availability and a high incidence of systemic side effects. Cardiovascular diseases (CVD) are the leading cause of death all over the world. Targeted drug delivery (TDD) methods with the heart as the target organ have developed rapidly and are diversified. This article reviews the research progress of various TDD methods around the world with a heart as the target organ. It is mainly divided into two parts: the targeting vector represented by nanoparticles and various TDD methods such as intracoronary injection, ventricular wall injection, pericardial injection, and implantable medical device therapy and put forward some suggestions on the development of targeting. Different TDD methods described in this paper have not been widely used in clinical practice, and some have not even completed preclinical studies. Targeted drug delivery still requires long-term efforts by many researchers to realize the true meaning of the heart. HIGHLIGHTS Targeted administration can achieve a better therapeutic effect and effectively reduce the occurrence of adverse reactions. Parenteral administration or medical device implantation can be used for targeted drug delivery. Combined with new dosage forms or new technologies, better-targeted therapy can be achieved. Clinical trials have confirmed the safety and effectiveness of several administration methods.

Dose-Independent Therapeutic Benefit of Bone Marrow Stem Cell Transplantation after MI in Mice

Several cell populations derived from bone marrow (BM) have been shown to possess cardiac regenerative potential. Among these are freshly isolated CD133⁺ hematopoietic as well as culture-expanded mesenchymal stem cells. Alternatively, by purifying CD271⁺ cells from BM, mesenchymal progenitors can be enriched without an ex vivo cultivation. With regard to the limited available number of freshly isolated BM-derived stem cells, the effect of the dosage on the therapeutic efficiency is of particular interest. Therefore, in the present pre-clinical study, we investigated human BM-derived CD133⁺ and CD271⁺ stem cells for their cardiac regenerative potential three weeks post-myocardial infarction (MI) in a dose-dependent manner. The improvement of the hemodynamic function as well as cardiac remodeling showed no therapeutic difference after the transplantation of both 100,000 and 500,000 stem cells. Therefore, beneficial stem cell transplantation post-MI is widely independent of the cell dose and detrimental stem cell amplification in vitro can likely be avoided.

Adaptation within embryonic and neonatal heart environment reveals alternative fates for adult c-kit+ cardiac interstitial cells

Cardiac interstitial cells (CICs) perform essential roles in myocardial biology through preservation of homeostasis as well as response to injury or stress. Studies of murine CIC biology reveal remarkable plasticity in terms of transcriptional reprogramming and ploidy state with important implications for function. Despite over a decade of characterization and in vivo utilization of adult c-Kit+ CIC (cCIC), adaptability and functional responses upon delivery to adult mammalian hearts remain poorly understood. Limitations of characterizing cCIC biology following in vitro expansion and adoptive transfer into the adult heart were circumvented by delivery of the donated cells into early cardiogenic environments of embryonic, fetal, and early postnatal developing hearts. These three developmental stages were permissive for retention and persistence, enabling phenotypic evaluation of in vitro expanded cCICs after delivery as well as tissue response following introduction to the host environment. Embryonic blastocyst environment prompted cCIC integration into trophectoderm as well as persistence in amniochorionic membrane. Delivery to fetal myocardium yielded cCIC perivascular localization with fibroblast-like phenotype, similar to cCICs introduced to postnatal P3 heart with persistent cell cycle activity for up to 4 weeks. Fibroblast-like phenotype of exogenously transferred cCICs in fetal and postnatal cardiogenic environments is consistent with inability to contribute directly toward cardiogenesis and lack of functional integration with host myocardium. In contrast, cCICs incorporation into extra-embryonic membranes is consistent with fate of polyploid cells in blastocysts. These findings provide insight into cCIC biology, their inherent predisposition toward fibroblast fates in cardiogenic environments, and remarkable participation in extra-embryonic tissue formation.

Deterministic paracrine repair of injured myocardium using microfluidic-based cocooning of heart explant-derived cells

While encapsulation of cells within protective nanoporous gel cocoons increases cell retention and pro-survival integrin signaling, the influence of cocoon size and intra-capsular cell-cell interactions on therapeutic repair are unknown. Here, we employ a microfluidic platform to dissect the impact of cocoon size and intracapsular cell number on the regenerative potential of transplanted heart explant-derived cells. Deterministic increases in cocoon size boosted the proportion of multicellular aggregates within cocoons, reduced vascular clearance of transplanted cells and enhanced stimulation of endogenous repair. The latter being attributable to cell-cell stimulation of cytokine and extracellular vesicle production while also broadening of the miRNA cargo within extracellular vesicles. Thus, by tuning cocoon size and cell occupancy, the paracrine signature and retention of transplanted cells can be enhanced to promote paracrine stimulation of endogenous tissue repair.

Dimethyl sulfoxide-free cryopreservation for cell therapy: A review

Cell-based therapeutics promise to transform the treatment of a wide range of diseases including cancer, genetic and degenerative disorders, or severe injuries. Many of the commercial and clinical development of cell therapy products require cryopreservation and storage of cellular starting materials, intermediates and/or final products at cryogenic temperature. Dimethyl sulfoxide (Me₂SO) has been the cryoprotectant of choice in most biobanking situations due to its exceptional performance in mitigating freezing-related damages. However, there is concern over the toxicity of Me₂SO and its potential side effects after administration to patients. Therefore, there has been growing demand for robust Me₂SO-free cryopreservation methods that can improve product safety and maintain potency and efficacy. This article provides an overview of the recent advances in Me₂SO-free cryopreservation of cells having therapeutic potentials and discusses a number of key challenges and opportunities to motivate the continued innovation of cryopreservation for cell therapy.

Engineered M13 Peptide Carrier Promotes Angiogenic Potential of Patient-Derived Human Cardiac Progenitor Cells and In Vivo Engraftment

BACKGROUND

Despite promising advances in stem cell-based therapy, the treatment of ischemic cardiovascular diseases remains a big challenge due to both the insufficient in vivo viability of transplanted cells and poor angiogenic potential of stem cells. The goal of this study was to develop therapeutic human cardiac progenitor cells (hCPCs) for ischemic cardiovascular diseases with a novel M13 peptide carrier.

METHOD

In this study, an engineered M13 peptide carrier was successfully generated using a QuikChange Kit. The cellular function of M13 peptide carrier-treated hCPCs was assessed using a tube formation assay and scratch wound healing assay. The in vivo engraftment and cell survival bioactivities of transplanted cells were demonstrated by immunohistochemistry after hCPC transplantation into a myocardial infarction animal model.

RESULTS

The engineered M13^RGD+SDKP peptide carrier, which expressed RGD peptide on PIII site and SDKP peptide on PVIII site, did not affect morphologic change and proliferation ability in hCPCs. In contrast, hCPCs treated with M13^RGD+SDKP showed enhanced angiogenic capacity, including tube formation and migration capacity. Moreover, transplanted hCPCs with M13^RGD+SDKP were engrafted into the ischemic region and promoted in vivo cell survival.

CONCLUSION

Our present data provides a promising protocol for CPC-based cell therapy via short-term cell priming of hCPCs with engineered M13^RGD+SDKP before cell transplantation for treatment of cardiovascular disease.

Cardiovascular progenitor cells and tissue plasticity are reduced in a myocardium affected by Becker muscular dystrophy

Abstract

We describe the association of Becker muscular dystrophy (BMD) derived heart failure with the impairment of tissue homeostasis and remodeling capabilities of the affected heart tissue. We report that BMD heart failure is associated with a significantly decreased number of cardiovascular progenitor cells, reduced cardiac fibroblast migration, and ex vivo survival.

Background

Becker muscular dystrophy belongs to a class of genetically inherited dystrophin deficiencies. It affects male patients and results in progressive skeletal muscle degeneration and dilated cardiomyopathy leading to heart failure. It is a relatively mild form of dystrophin deficiency, which allows patients to be on a heart transplant list. In this unique situation, the explanted heart is a rare opportunity to study the degenerative process of dystrophin-deficient cardiac tissue. Heart tissue was excised, dissociated, and analyzed. The fractional content of c-kit⁺/CD45⁻ cardiovascular progenitor cells (CVPCs) and cardiac fibroblast migration were compared to control samples of atrial tissue. Control tissue was obtained from the hearts of healthy organ donor’s during heart transplantation procedures.

Results

We report significantly decreased CVPCs (c-kit⁺/CD45⁻) throughout the heart tissue of a BMD patient, and reduced numbers of phase-bright cells presenting c-kit positivity in the dystrophin-deficient cultured explants. In addition, ex vivo CVPCs survival and cardiac fibroblasts migration were significantly reduced, suggesting reduced homeostatic support and irreversible tissue remodeling.

Conclusions

Our findings associate genetically derived heart failure in a dystrophin-deficient patient with decreased c-kit⁺/CD45⁻ CVPCs and their resilience, possibly hinting at a lack of cardioprotective capability and/or reduced homeostatic support. This also correlates with reduced plasticity of the explanted cardiac tissue, related to the process of irreversible remodeling in the BMD patient’s heart.

Agonist Antibody Converts Stem Cells into Migrating Brown Adipocyte-Like Cells in Heart

We present data showing that Iodotyrosine Deiodinase (IYD) is a dual-function enzyme acting as a catalyst in metabolism and a receptor for cooperative stem cell differentiation. IYD is present both in thyroid cells where it is critical for scavenging iodine from halogenated by-products of thyroid hormone production and on hematopoietic stem cells. To close the cooperative loop, the mono- and di-Iodotyrosine (MIT and DIT) substrates of IYD in the thyroid are also agonists for IYD now acting as a receptor on bone marrow stem cells. While studying intracellular combinatorial antibody libraries, we discovered an agonist antibody, H3 Ab, of which the target is the enzyme IYD. When agonized by H3 Ab, IYD expressed on stem cells induces differentiation of the cells into brown adipocyte-like cells, which selectively migrate to mouse heart tissue. H3 Ab also binds to IYD expressed on human myocardium. Thus, one has a single enzyme acting in different ways on different cells for the cooperative purpose of enhancing thermogenesis or of regenerating damaged heart tissue.

The Importance of HLA Assessment in "Off-the-Shelf" Allogeneic Mesenchymal Stem Cells Based-Therapies

The need for more effective therapies of chronic and acute diseases has led to the attempts of developing more adequate and less invasive treatment methods. Regenerative medicine relies mainly on the therapeutic potential of stem cells. Mesenchymal stem cells (MSCs), due to their immunosuppressive properties and tissue repair abilities, seem to be an ideal tool for cell-based therapies. Taking into account all available sources of MSCs, perinatal tissues become an attractive source of allogeneic MSCs. The allogeneic MSCs provide "off-the-shelf" cellular therapy, however, their allogenicity may be viewed as a limitation for their use. Moreover, some evidence suggests that MSCs are not as immune-privileged as it was previously reported. Therefore, understanding their interactions with the recipient's immune system is crucial for their successful clinical application. In this review, we discuss both autologous and allogeneic application of MSCs, focusing on current approaches to allogeneic MSCs therapies, with a particular interest in the role of human leukocyte antigens (HLA) and HLA-matching in allogeneic MSCs transplantation. Importantly, the evidence from the currently completed and ongoing clinical trials demonstrates that allogeneic MSCs transplantation is safe and seems to cause no major side-effects to the patient. These findings strongly support the case for MSCs efficacy in treatment of a variety of diseases and their use as an "off-the-shelf" medical product.

Human Wharton's Jelly-Derived Mesenchymal Stem Cells Minimally Improve the Growth Kinetics and Cardiomyocyte Differentiation of Aged Murine Cardiac c-kit Cells in In Vitro without Rejuvenating Effect

Cardiac c-kit cells show promise in regenerating an injured heart. While heart disease commonly affects elderly patients, it is unclear if autologous cardiac c-kit cells are functionally competent and applicable to these patients. This study characterised cardiac c-kit cells (CCs) from aged mice and studied the effects of human Wharton’s Jelly-derived mesenchymal stem cells (MSCs) on the growth kinetics and cardiac differentiation of aged CCs in vitro. CCs were isolated from 4-week- and 18-month-old C57/BL6N mice and were directly co-cultured with MSCs or separated by transwell insert. Clonogenically expanded aged CCs showed comparable telomere length to young CCs. However, these cells showed lower Gata4, Nkx2.5, and Sox2 gene expressions, with changes of 2.4, 3767.0, and 4.9 folds, respectively. Direct co-culture of both cells increased aged CC migration, which repopulated 54.6 ± 4.4% of the gap area as compared to aged CCs with MSCs in transwell (42.9 ± 2.6%) and CCs without MSCs (44.7 ± 2.5%). Both direct and transwell co-culture improved proliferation in aged CCs by 15.0% and 16.4%, respectively, as traced using carboxyfluorescein succinimidyl ester (CFSE) for three days. These data suggest that MSCs can improve the growth kinetics of aged CCs. CCs retaining intact telomere are present in old hearts and could be obtained based on their self-renewing capability. Although these aged CCs with reduced growth kinetics are improved by MSCs via cell–cell contact, the effect is minimal.

Engineering Functional Cardiac Tissues for Regenerative Medicine Applications

PURPOSE OF REVIEW

Tissue engineering has expanded into a highly versatile manufacturing landscape that holds great promise for advancing cardiovascular regenerative medicine. In this review, we provide a summary of the current state-of-the-art bioengineering technologies used to create functional cardiac tissues for a variety of applications in vitro and in vivo.

RECENT FINDINGS

Studies over the past few years have made a strong case that tissue engineering is one of the major driving forces behind the accelerating fields of patient-specific regenerative medicine, precision medicine, compound screening, and disease modeling. To date, a variety of approaches have been used to bioengineer functional cardiac constructs, including biomaterial-based, cell-based, and hybrid (using cells and biomaterials) approaches. While some major progress has been made using cellular approaches, with multiple ongoing clinical trials, cell-free cardiac tissue engineering approaches have also accomplished multiple breakthroughs, although drawbacks remain. This review summarizes the most promising methods that have been employed to generate cardiovascular tissue constructs for basic science or clinical applications. Further, we outline the strengths and challenges that are inherent to this field as a whole and for each highlighted technology.

A new structure from cardiac cells cultured in vitro: Cardiomyocyte-annulation of neonatal rats

To explore the formation, morphological characteristics, cell composition, and differentiation potential of cardiomyocyte annulation (cardio-annulation) during in vitro culture of cardiac cells. Cardiac cells were isolated and cultured. A live-cell imaging system was used to observe cardio-annulation. Cardiac troponin-T (cTnT) and vimentin were labeled with double immunofluorescence staining, and coexpressions of cTnT and connexin43 (Cx43), cTnT and nanog, c-kit and nanog, and c-kit and stem cell antigen (sca-1) were detected. The location of various types of cells within the cardio-annulation structure was observed. Adipogenic- and osteogenic-inducing fluids were used separately for in situ induction to detect the multidirectional differentiation potential of cells during the annulation process. After 3 to 6 days, cardiac cells migrated and formed an open or closed annulus with a diameter of 800 to 3500 μm. The annulus wall comprised the medial, middle, and lateral regions. The cells in the medial region were small, abundant, and laminated, while those in the middle region were larger with fewer layers, and those in the lateral region were less abundant, and loosely arranged in a single layer. Cardiomyocytes were distributed mainly on the surface of the medial region; nanog⁺ , c-kit⁺ , and sca-1⁺ cells were located mainly at the bottom of the annulus wall and fibroblasts were located mainly between these layers. The annulus cavity contained a large number of small, round cells, and telocytes. Cx43 was expressed in all cell types, and nanog, c-kit, and sca-1 were coexpressed in the cardio-annulation cells, which possess adipogenic and osteogenic differentiation potential. Cardio-annulation was discovered during an in vitro culture of cardiac cells. The structure contains cardiomyocytes, fibroblasts, telocytes, and abundant stem cells. These results provide insight into the relationship among cardiac cells in vitro.

Cellular Therapy for Ischemic Heart Disease: An Update

Ischemic heart disease (IHD), which includes heart failure (HF) induced by heart attack (myocardial infarction, MI), is a significant cause of morbidity and mortality worldwide (Benjamin, et al. Circulation 139:e56-e66, 2019). MI occurs at an alarmingly high rate in the United States (approx. One case every 40 seconds), and the failure to repair damaged myocardium is the leading cause of recurrent heart attacks, heart failure (HF), and death within 5 years of MI (Benjamin, et al. Circulation 139:e56-e66, 2019). At present, HF represents an unmet need with no approved clinical therapies to replace the damaged myocardium. As the population ages, the number of heart failure patients is projected to increase, doubling the annual cost by 2030 (Benjamin, et al. Circulation 139:e56-e66, 2019). In the past decades, stem cell therapy has become a promising strategy for cardiac regeneration. However, stem cell-based therapy yielded modest success in human clinical trials. This chapter examines the types of cells examined in cardiac therapy in the setting of IHD, with a brief introduction to ongoing research aiming at enhancing the therapeutic potential of transplanted cells.

Mesenchymal stem cells facilitate cardiac differentiation in Sox2-expressing cardiac C-kit cells in coculture

Stem cell therapy offers hope to reconstitute injured myocardium and salvage heart from failing. A recent approach using combinations of derived Cardiac-derived c-kit expressing cells (CCs) and mesenchymal stem cells (MSCs) in transplantation improved infarcted hearts with a greater functional outcome, but the effects of MSCs on CCs remain to be elucidated. We used a novel two-step protocol to clonogenically amplify colony forming c-kit expressing cells from 4- to 6-week-old C57BL/6N mice. This method yielded highly proliferative and clonogenic CCs with an average population doubling time of 17.2 ± 0.2, of which 80% were at the G1 phase. We identified two distinctly different CC populations based on its Sox2 expression, which was found to inversely related to their nkx2.5 and gata4 expression. To study CCs after MSC coculture, we developed micron-sized particles of iron oxide-based magnetic reisolation method to separate CCs from MSCs for subsequent analysis. Through validation using the sex and species mismatch CC-MSC coculture method, we confirmed that the purity of the reisolated cells was greater than 85%. In coculture experiment, we found that MSCs prominently enhanced Ctni and Mef2c expressions in Sox2 ^pos CCs after the induction of cardiac differentiation, and the level was higher than that of conditioned medium Sox2 ^pos CCs. However, these effects were not found in Sox2 ^neg CCs. Immunofluorescence labeling confirmed the presence of cardiac-like cells within Sox2 ^pos CCs after differentiation, identified by its cardiac troponin I and α-sarcomeric actinin expressions. In conclusion, this study shows that MSCs enhance CC differentiation toward cardiac myocytes. This enhancement is dependent on CC stemness state, which is determined by Sox2 expression.

Bioactive scaffolds in stem-cell-based therapies for cardiac repair: protocol for a meta-analysis of randomized controlled preclinical trials in animal myocardial infarction models

BACKGROUND

Acute myocardial infarction (MI) remains one of the leading causes of death worldwide with no curative therapy available. Stem cell therapies have been gaining interest as a means to repair the cardiac tissue after MI and prevent the onset of heart failure. Many in vivo reports suggest that the use of stem cells is promising, yet clinical trials suggest that the cells fail to integrate into the native tissue, resulting in limited improvements in cardiac function and repair. To battle this limitation, the combination of using stem cells embedded in a bioactive scaffold that promotes cell retention is growing in interest. Yet, a systematic review of the literature on the use of stem cells embedded in bioactive scaffolds for cardiac repair has not yet been performed. In this protocol, we outline a systematic review and meta-analysis of preclinical trials in animal MI models that utilize stem cell-embedded scaffolds for cardiac repair and compare their effects to stem cell-treated animals without the use of a scaffold.

METHODS/DESIGN

We will search the following electronic databases: Cochrane Library, MEDLINE, Embase, PubMed, Scopus and Web of Science, and gray literature: Canadian Agency for Drugs and Technologies in Health and Google Scholar. We will only include randomly controlled preclinical trials that have directly investigated the effects of stem cells embedded in a scaffold for cardiac repair in an animal MI model. Two investigators will independently review each article included in the final analysis. The primary endpoint that will be investigated is left ventricular ejection fraction. Secondary endpoints will include infarct size, end systolic volume, end diastolic volume, fractional shortening and left ventricular wall thickness. Pooled analyses will be conducted using the DerSimonian-Laird random effects and Mantel-Haenszel fixed-effect models. Between-studies heterogeneity will be quantified and determined using the Tau2 and I2 statistics. Publication bias will be assessed using visual inspection of funnel plots and complemented by Begg's and Egger's statistical tests. Possible sources of heterogeneity will be assessed using subgroup-meta analysis and meta-regression.

DISCUSSION

To date, the use of scaffolds in myocardial repair has not yet been systematically reviewed. The results of this meta-analysis will aid in determining the efficacy of stem cell-embedded scaffolds for cardiac repair and help bring this therapy to the clinic.

Impaired adhesion of induced pluripotent stem cell-derived cardiac progenitor cells (iPSC-CPCs) to isolated extracellular matrix from failing hearts

We tested the hypothesis that induced pluripotent stem cell-derived cardiac progenitor cells (iPSC-CPCs) are less able to adhere to the extracellular matrix (ECM) derived from failing human hearts with dilated cardiomyopathy compared to nonfailing human heart ECM. We also hypothesized that morphological development, cell beating rates, and mRNA levels of Nkx2.5 and cardiac troponin T would be altered after culturing the iPSC-CPCs on the failing heart ECM under cardiomyocyte differentiation conditions. We used microscopy to distinguish between adhered and unadhered cells, and to determine morphological development and cell beating. We used qPCR to determine mRNA levels. iPSC-CPCs show a significantly reduced ability to adhere to the ECM of failing hearts and higher expression of Nkx2.5 mRNA. However, morphological development, cell beating rates, and cardiac troponin T levels were not significantly altered in the cells cultured on the failing heart ECM. Our study shows that the failing heart ECM from patients with dilated cardiomyopathy impairs initial iPSC-CPC adhesion and may have a modest effect on the ability of the cells to transdifferentiate into cardiomyocytes.

Therapeutic approaches for cardiac regeneration and repair

Ischaemic heart disease is a leading cause of death worldwide. Injury to the heart is followed by loss of the damaged cardiomyocytes, which are replaced with fibrotic scar tissue. Depletion of cardiomyocytes results in decreased cardiac contraction, which leads to pathological cardiac dilatation, additional cardiomyocyte loss, and mechanical dysfunction, culminating in heart failure. This sequential reaction is defined as cardiac remodelling. Many therapies have focused on preventing the progressive process of cardiac remodelling to heart failure. However, after patients have developed end-stage heart failure, intervention is limited to heart transplantation. One of the main reasons for the dramatic injurious effect of cardiomyocyte loss is that the adult human heart has minimal regenerative capacity. In the past 2 decades, several strategies to repair the injured heart and improve heart function have been pursued, including cellular and noncellular therapies. In this Review, we discuss current therapeutic approaches for cardiac repair and regeneration, describing outcomes, limitations, and future prospects of preclinical and clinical trials of heart regeneration. Substantial progress has been made towards understanding the cellular and molecular mechanisms regulating heart regeneration, offering the potential to control cardiac remodelling and redirect the adult heart to a regenerative state.

Effect of transplantation of cardiac stem cells overexpressing integrin-linked kinase on cardiac function of rats with acute myocardial infarction

In the present study, we aimed to investigate the effect of transplantation of cardiac stem cells (CSCs) overexpressing integrin-linked kinase (ILK) on cardiac function of rats with acute myocardial infarction (MI). A total of 60 rats were randomly divided into normal saline (NS) group (n=20), green fluorescent protein (GFP)-CSC group (n=20) and ILK-CSC group (n=20). In the ILK-CSC group, CSCs in rats were transfected with GFP adenovirus vector overexpressing ILK. The rat model of MI was established. The cardiac function 4 weeks after transplantation was detected via echocardiography, and the exhaustive swimming experiment was performed to observe the exercise load capacity. Moreover, Ki-67 and P-H3 proteins in myocardial tissues of rats were detected via immunohistochemistry, and the expression of GFP was observed under a fluorescence microscope. Cells in the GFP-CSC group were transfected with the empty GFP adenovirus, while those in NS group were not transfected, and other treatments in these two groups were the same as those in the ILK-CSC group. Four weeks after transplantation, left ventricular end-systolic diameter (LVESD) and left ventricular end-diastolic diameter (LVEDD) of rats in the ILK-CSC group were smaller than those in the GFP-CSC group, but left ventricular ejection fraction (LVEF) (69.88±5.61 mm) was higher than that in the GFP-CSC group (P<0.05). The exercise time in the ILK-CSC group (12.69±0.58 min) was longer than that in the GFP-CSC and NS groups (P<0.05). The expression levels of Ki-67 and P-H3 proteins in myocardial cells of rats in the ILK-CSC group were higher than those in the GFP-CSC and NS groups (P<0.05). The number of transplanted cells retained around the infarct region in the ILK-CSC group 3 days after transplantation was obviously larger than that in the GFP-CSC group (P<0.001). Intramyocardial injection of CSCs overexpressing ILK immediately after the establishment of rat model of MI can promote myocardial cell proliferation, improve cardiac function and increase exercise capacity of rats.

[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.

Imatinib mesylate-induced cardiomyopathy involves resident cardiac progenitors

Cardiovascular complications are included among the systemic effects of tyrosine kinase inhibitor (TKI)-based therapeutic strategies. To test the hypothesis that inhibition of Kit tyrosine kinase that promotes cardiac progenitor cell (CPC) survival and function may be one of the triggering mechanisms of imatinib mesylate (IM)-related cardiovascular effects, the anatomical, structural and ultrastructural changes in the heart of IM-treated rats were evaluated. Cardiac anatomy in IM-exposed rats showed a dose-dependent, restrictive type of remodeling and depressed hemodynamic performance in the absence of remarkable myocardial fibrosis. The effects of IM on rat and human CPCs were also assessed. IM induced rat CPC depletion, reduced growth and increased cell death. Similar effects were observed in CPCs isolated from human hearts. These results extend the notion that cardiovascular side effects are driven by multiple actions of IM. The identification of cellular mechanisms responsible for cardiovascular complications due to TKIs will enable future strategies aimed at preserving concomitantly cardiac integrity and anti-tumor activity of advanced cancer treatment.