Cell delivery routes for stem cell therapy to the heart: current and future approaches

The Application of Mesenchymal Stem Cells in Different Cardiovascular Disorders: Ways of Administration, and the Effectors

The heart is an organ with a low ability to renew and repair itself. MSCs have cell surface markers such as CD45-, CD34-, CD31-, CD4+, CD11a+, CD11b+, CD15+, CD18+, CD25+, CD49d+, CD50+, CD105+, CD73+, CD90+, CD9+, CD10+, CD106+, CD109+, CD127+, CD120a+, CD120b+, CD124+, CD126+, CD140a+, CD140b+, adherent properties and the ability to differentiate into cells such as adipocytes, osteoblasts and chondrocytes. Autogenic, allogeneic, normal, pretreated and genetically modified MSCs and secretomes are used in preclinical and clinical studies. MSCs and their secretomes (the total released molecules) generally have cardioprotective effects. Studies on cardiovascular diseases using MSCs and their secretomes include myocardial infraction/ischemia, fibrosis, hypertrophy, dilated cardiomyopathy and atherosclerosis. Stem cells or their secretomes used for this purpose are administered to the heart via intracoronary (Antegrade intracoronary and retrograde coronary venous injection), intramyocardial (Transendocardial and epicardial injection) and intravenous routes. The protective effects of MSCs and their secretomes on the heart are generally attributed to their differentiation into cardiomyocytes and endothelial cells, their immunomodulatory properties, paracrine effects, increasing blood vessel density, cardiac remodeling, and ejection fraction and decreasing apoptosis, the size of the wound, end-diastolic volume, end-systolic volume, ventricular myo-mass, fibrosis, matrix metalloproteins, and oxidative stress. The present review aims to assist researchers and physicians in selecting the appropriate cell type, secretomes, and technique to increase the chance of success in designing therapeutic strategies against cardiovascular diseases.

Stem cell therapy for cardiac regeneration: past, present, and future

Cardiac disorders remain the leading cause of mortality worldwide. Current clinical strategies, including drug therapy, surgical interventions, and organ transplantation offer limited benefits to patients without regenerating the damaged myocardium. Over the past decade, stem cell therapy has generated a keen interest owing to its unique self-renewal and immune privileged characteristics. Furthermore, the ability of stem cells to differentiate into specialized cell types, has made them a popular therapeutic tool against various diseases. This comprehensive review provides an overview of therapeutic potential of different types of stem cells in reference to cardiovascular diseases. Furthermore, it sheds light on the advantages and limitations associated with each cell type. An in-depth analysis of the challenges associated with stem cell research and the hurdles for its clinical translation and their possible solutions have also been elaborated upon. It examines the controversies surrounding embryonic stem cells and the emergence of alternative approaches, such as the use of induced pluripotent stem cells for cardiac therapeutic applications. Overall, this review serves as a valuable resource for researchers, clinicians, and policymakers involved in the field of regenerative medicine, guiding the development of safe and effective stem cell-based therapies to revolutionize patient care.

Organ-Specific Differentiation of Human Adipose-Derived Stem Cells in Various Organs of Xenotransplanted Rats: A Pilot Study

Adipose-derived stem cells (ADSCs) are potential therapeutics considering their self-renewal capacity and ability to differentiate into all somatic cell types in vitro. The ideal ADSC-based therapy is a direct injection into the relevant organs. The objective of this study was to investigate the viability and safety of intra-organ human ADSC (h-ADSC) xenotransplants in vivo. Subcutaneous adipose tissue from the abdominal area of 10 patients was sampled. h-ADSCs were isolated from adipose tissue samples and identified using immunofluorescence antibodies. Multi-differentiation potential assays for adipocytes, osteocytes, and chondrocytes were performed. Cultured h-ADSCs at passage 4 were transplanted into multiple organs of 17 rats, including the skin, subcutaneous layer, liver, kidney, pancreas, and spleen. The h-ADSC-injected organs excised after 100 days were examined, and the survival of h-ADSCs was measured by quantitative real-time polymerase chain reaction (qRT-PCR) using specific human and rat target genes. h-ADSCs confirmed by stem cell phenotyping were induced to differentiate into adipogenic, osteogenic, and chondrogenic lineages in vitro. All rats were healthy and exhibited no side effects during the study; the transplanted h-ADSCs did not cause inflammation and were indiscernible from the native organ cells. The presence of transplanted h-ADSCs was confirmed using qRT-PCR. However, the engrafted survival rates varied as follows: subcutaneous fat (70.6%), followed by the liver (52.9%), pancreas (50.0%), kidney (29.4%), skin (29.4%), and spleen (12.5%). h-ADSCs were successfully transplanted into a rat model, with different survival rates depending on the organ.

Microneedle-based technology for cell therapy: current status and future directions

With the growing technological innovations in medical treatments, cell-based therapies hold great potential as efficient tools against various previously incurable diseases by restoring or altering the function of certain sets of cells. Along this line, an essential factor to determine the success of cell therapy is the choice of cell delivery strategy. In recent years, a novel trend is blooming in the application of microneedle systems, which are based on the miniaturization of multiple needles within a patch to the micrometer dimensions, aimed at the delivery of therapeutic cells to the target site with high efficiency and in a minimally invasive manner. This review aims to demonstrate the advantages of exploiting microneedle-based technology as a new tool for cell therapy. The advancements of microneedle-based strategies for cell delivery are summarized in terms of two categories: cell-free and cell-loaded microneedle systems. The majority of research on microneedle-based cell therapy has shown promising results for tissue regeneration, cancer immunotherapy, skin immune monitoring and targeted cell delivery. Finally, current challenges and future perspectives toward the development and application of microneedles for cell therapy are also discussed.

Optimal Delivery Route of Mesenchymal Stem Cells for Cardiac Repair: The Path to Good Clinical Practice

Research has shown that mesenchymal stem cells (MSCs) could be a promising therapy for treating progressive heart disease. However, translation into clinics efficiently and successfully has proven to be much more complicated. Many questions remain for optimizing treatment. Application method influences destiny of MSCs and afterwards impacts results of procedure, yet there is no general agreement about most suitable method of MSC delivery in the clinical setting. Herein, we explain principle of most-frequent MSCs delivery techniques in cardiology. This chapter summarizes crucial translational obstacles of clinical employment of MSCs for cardiac repair when analysed trough a prism of latest research centred on different techniques of MSCs application.

Locoregional delivery of stem cell-based therapies

Interventional regenerative medicine (IRM) uses image-guided, minimally invasive procedures for the targeted delivery of stem cell-based therapies to regenerate, replace, or repair damaged organs. Although many cellular therapies have shown promise in the preclinical setting, clinical results have been suboptimal. Most intravenously delivered cells become trapped in the lungs and reticuloendothelial system, resulting in little therapy reaching target tissues. IRM aims to increase the efficacy of cell-based therapies by locoregional stem cell delivery via endovascular, endoluminal, or direct injection into tissues. This review highlights routes of delivery, disease states, and mechanisms of action involved in the targeted delivery of stem cells.

Stem cell therapy for heart failure: Medical breakthrough, or dead end?

Heart failure continues to be one of the leading causes of morbidity and mortality worldwide. Myocardial infarction is the primary causative agent of chronic heart failure resulting in cardiomyocyte necrosis and the subsequent formation of fibrotic scar tissue. Current pharmacological and non-pharmacological therapies focus on managing symptoms of heart failure yet remain unable to reverse the underlying pathology. Heart transplantation usually cannot be relied on, as there is a major discrepancy between the availability of donors and recipients. As a result, heart failure carries a poor prognosis and high mortality rate. As the heart lacks significant endogenous regeneration potential, novel therapeutic approaches have incorporated the use of stem cells as a vehicle to treat heart failure as they possess the ability to self-renew and differentiate into multiple cell lineages and tissues. This review will discuss past, present, and future clinical trials, factors that influence stem cell therapy outcomes as well as ethical and safety considerations. Preclinical and clinical studies have shown a wide spectrum of outcomes when applying stem cells to improve cardiac function. This may reflect the infancy of clinical trials and the limited knowledge on the optimal cell type, dosing, route of administration, patient parameters and other important variables that contribute to successful stem cell therapy. Nonetheless, the field of stem cell therapeutics continues to advance at an unprecedented pace. We remain cautiously optimistic that stem cells will play a role in heart failure management in years to come.

All Roads Lead to Rome (the Heart): Cell Retention and Outcomes From Various Delivery Routes of Cell Therapy Products to the Heart

In the past decades, numerous preclinical studies and several clinical trials have evidenced the feasibility of cell transplantation in treating heart diseases. Over the years, different delivery routes of cell therapy have emerged and broadened the width of the field. However, a common hurdle is shared by all current delivery routes: low cell retention. A myriad of studies confirm that cell retention plays a crucial role in the success of cell-mediated cardiac repair. It is important for any delivery route to maintain donor cells in the recipient heart for enough time to not only proliferate by themselves, but also to send paracrine signals to surrounding damaged heart cells and repair them. In this review, we first undertake an in-depth study of primary theories of cell loss, including low efficiency in cell injection, "washout" effects, and cell death, and then organize the literature from the past decade that focuses on cell transplantation to the heart using various cell delivery routes, including intracoronary injection, systemic intravenous injection, retrograde coronary venous injection, and intramyocardial injection. In addition to a recapitulation of these approaches, we also clearly evaluate their strengths and weaknesses. Furthermore, we conduct comparative research on the cell retention rate and functional outcomes of these delivery routes. Finally, we extend our discussion to state-of-the-art bioengineering techniques that enhance cell retention, as well as alternative delivery routes, such as intrapericardial delivery. A combination of these novel strategies and more accurate assessment methods will help to address the hurdle of low cell retention and boost the efficacy of cell transplantation to the heart.

Engineered cell-degradable poly(2-alkyl-2-oxazoline) hydrogel for epicardial placement of mesenchymal stem cells for myocardial repair

Epicardial placement of mesenchymal stromal cells (MSCs) is a promising strategy for cardiac repair post-myocardial infarction, but requires the design of biomaterials to maximise the retention of donor cells on the heart surface and control their phenotype. To this end, we propose the use of a poly(2-alkyl-2-oxazoline) (POx) derivative, based on 2-ethyl-2-oxazoline and 2-butenyl-2-oxazoline. This POx polymer can be cured rapidly (less than 2 min) via photo-irradiation due to the use of di-cysteine cell degradable peptides. We report that the cell-degradable properties of the resulting POx hydrogels enables the regulation of cell protrusion in corresponding 3D matrices and that this, in turn, regulates the secretory phenotype of MSCs. In particular, the expression of pro-angiogenic genes was upregulated in partially cell-degradable POx hydrogels. Improved angiogenesis was confirmed in an in vitro microfluidic assay. Finally, we confirmed that, owing to the excellent tissue adhesive properties of thiol-ene crosslinked hydrogels, the epicardial placement of MSC-loaded POx hydrogels promoted the recovery of cardiac function and structure with reduced interstitial fibrosis and improved neovascular formation in a rat myocardial infarction model. This report demonstrates that engineered synthetic hydrogels displaying controlled mechanical, cell degradable and bioactive properties are particularly attractive candidates for the epicardial placement of stem cells to promote cardiac repair post myocardial infarction.

Human amniotic membrane as a delivery vehicle for stem cell-based therapies

Stem cell-based therapy is known as a regenerative approach for a variety of diseases and tissue injuries. These cells exert their therapeutic effects through paracrine secretions namely extracellular vesicles. To achieve higher therapeutic potential, a variety of delivery routes have been tested in clinical and preclinical studies. Direct cell injection, intra-venous administration, and intra-arterial infusion are widely used methods of stem cells delivery but these methods are associated with several complications. As one of the most popular biological delivery systems, amniotic membrane has been widely utilized to support cell proliferation and differentiation therefore facilitating tissue regeneration without endangering the stem cells' viability. It is composed of several extracellular matrix components and growth factors. Due to these characteristics, amniotic membrane can mimic the stem cell's niche and can be an ideal carrier for stem cell transplantation. Here, we provide an overview of the recent progress, challenges, and future perspectives in the use of amniotic membrane as a delivery platform for stem cells.

Therapeutic approach for global myocardial injury using bone marrow-derived mesenchymal stem cells by cardiac support device in rats

Bone marrow-derived mesenchymal stem cells (BMSCs) have been considered a promising therapeutic approach to cardiovascular disease. This study intends to compare the effect of BMSCs through a standard active cardiac support device (ASD) and intravenous injection on global myocardial injury induced by isoproterenol. BMSCs were cultured in vitro, and the transplanted cells were labeled with a fluorescent dye CM-Dil. Isoproterenol (ISO) was injected into the rats; 2 weeks later, the labeled cells were transplanted into ISO-induced heart-jury rats through the tail vein or ASD device for 5 days. The rats were sacrificed on the first day, the third day, and the fifth day after transplantation to observe the distribution of cells in the myocardium by fluorescence microscopy. The hemodynamic indexes of the left ventricle were measured before sacrificing. H&E staining and Masson's trichrome staining were used to evaluate the cardiac histopathology. In the ASD groups, after 3 days of transplantation, there were a large number of BMSCs on the epicardial surface, and after 5 days of transplantation, BMSCs were widely distributed in the ventricular muscle. But in the intravenous injection group, there were no labeled-BMSCs distributed. In the ASD + BMSCs-three days treated group and ASD + BMSCs -five days-treated group, left ventricular systolic pressure (LVSP), the maximum rate of left ventricular pressure rise (+dP/dt), the maximum rate of left ventricular pressure decline (-dP/dt) increased compared with model group and intravenous injection group (P < 0.05). By giving BMSCs through ASD device, cells can rapidly and widely distribute in the myocardium and significantly improve heart function.

Systemic and local delivery of mesenchymal stem cells for heart renovation: Challenges and innovations

In the beginning stage of heart disease, the blockage of blood flow frequently occurs due to the persistent damage and even death of myocardium. Cicatricial tissue developed after the death of myocardium can affect heart function, which ultimately leads to heart failure. In recent years, several studies carried out about the use of stem cells such as embryonic, pluripotent, cardiac and bone marrow-derived stem cells as well as myoblasts to repair injured myocardium. Current studies focus more on finding appropriate measures to enhance cell homing and survival in order to increase paracrine function. Until now, there is no universal delivery route for mesenchymal stem cells (MSCs) for different diseases. In this review, we summarize the advantages and challenges of the systemic and local pathways of MSC delivery. In addition, we also describe some advanced measures of cell delivery to improve the efficiency of transplantation. The combination of cells and therapeutic substances could be the most reliable method, which allows donor cells to deliver sufficient amounts of paracrine factors and provide long-lasting effects. The cardiac support devices or tissue engineering techniques have the potential to facilitate the controlled release of stem cells on local tissue for a sustained period. A novel promising epicardial drug delivery system is highlighted here, which not only provides MSCs with a favorable environment to promote retention but also increases the contact area and a number of cells recruited in the heart muscle.

Cardioprotective effects of erythropoietin in diabetic rats determined by CD34 and vascular endothelial growth factor levels

Introduction

In this study, the effects of diabetes mellitus on the cardiovascular system were investigated by assessing the stem cell levels in serum and heart and compared with the normal population. Additionally, efficacy of erythropoietin, which is known to increase stem cells, was studied in diabetic rats.

Material and methods

Twenty-five male Sprague Dawley rats were divided into three groups as a control group (group 1), diabetic group (group 2) and erythropoietin induced diabetic group (group 3). A diabetes model was created with streptozocin. In group 3 rats received 3000 U/kg of erythropoietin. At the end of 1 month blood reticulocyte levels, degree of tissue fibrosis and immunohistochemical assessment of reliable stem cell markers, CD34 and vascular endothelial growth factor (VEGF), were analyzed.

Results

The increase in the blood glucose levels resulted in a significant decrease in reticulocyte levels in group 2. The increase in blood glucose levels resulted in a statistically significant increase in tissue level of fibrosis, CD34 and VEGF. When the rats in groups 1 and 2 were compared, the fibrosis, CD34 and VEGF levels were found to increase significantly. When group 2 and group 3 were compared, the amount of fibrosis was lower and the levels of CD34 and VEGF were significantly higher in group 3 than group 2.

Conclusions

The results of our study indicated that the amount of CD34 and VEGF which function in cellular protection and tissue regeneration may be enhanced with safely applicable erythropoietin leading to increase in reticulocyte levels in serum, and CD34 and VEGF levels in right atrium, right ventricle, left atrium, and left ventricle as a protective mechanism in diabetic rats.

Designing Microfluidic Devices to Sort Haematopoietic Stem Cells Based on Their Mechanical Properties

Aim

Few haematopoietic stem cells (HSCs) injected systemically for therapeutic purposes actually reach sites of injury as the vast majority become entrapped within pulmonary capillaries. One promising approach to maintain circulating HSC numbers would be to separate subpopulations with smaller size and/or greater deformability from a heterogeneous population. This study tested whether this could be achieved using label-free microfluidic devices.

Methods

2 straight (A-B) and 3 spiral (C-E) devices were fabricated with different dimensions. Cell sorting was performed at different flow rates after which cell diameter and stiffness were determined using micromanipulation. Cells isolated using the most efficient device were tested intravitally for their ability to home to the mouse injured gut.

Results

Only straight Device B at a high flow rate separated HSCs with different mechanical properties. Side outlets collected mostly deformable cells (nominal rupture stress/σ_R = 6.81 kPa; coefficient of variation/CV = 0.31) at a throughput of 2.3 × 10⁵ cells/min. All spiral devices at high flow rates separated HSCs with different stiffness and size. Inner outlets collected mostly deformable cells in Devices C (σ_R = 25.06 kPa; CV = 0.26), D (σ_R = 22.21 kPa; CV = 0.41), and E (σ_R = 29.26 kPa; CV = 0.27) at throughputs of 2.3 × 10⁵ cells/min, 1.5 × 10⁵ cells/min, and 1.6 × 10⁵ cells/min, respectively. Since Device C separated cells with higher efficiency and throughput, it was utilized to test the homing ability of separated cells in vivo. Significantly more deformable cells were observed trafficking through the injured gut—interestingly, increased retention was not observed.

Conclusion

This study applied microfluidics to separate subpopulations from one stem cell type based on their intrinsic mechanical heterogeneity. Fluid dynamics within curved devices most effectively separated HSCs. Such devices may benefit cellular therapy.

On-site fabrication of Bi-layered adhesive mesenchymal stromal cell-dressings for the treatment of heart failure

Mesenchymal stromal/stem cell (MSC)-based therapy is a promising approach for the treatment of heart failure. However, current MSC-delivery methods result in poor donor cell engraftment, limiting the therapeutic efficacy. To address this issue, we introduce here a novel technique, epicardial placement of bi-layered, adhesive dressings incorporating MSCs (MSC-dressing), which can be easily fabricated from a fibrin sealant film and MSC suspension at the site of treatment. The inner layer of the MSC dressing, an MSC-fibrin complex, promptly and firmly adheres to the heart surface without sutures or extra glues. We revealed that fibrin improves the potential of integrated MSCs through amplifying their tissue-repair abilities and activating the Akt/PI3K self-protection pathway. Outer collagen-sheets protect the MSC-fibrin complex from abrasion by surrounding tissues and also facilitates easy handling. As such, the MSC-dressing technique not only improves initial retention and subsequent maintenance of donor MSCs but also augment MSC's reparative functions. As a result, this technique results in enhanced cardiac function recovery with improved myocardial tissue repair in a rat ischemic cardiomyopathy model, compared to the current method. Dose-dependent therapeutic effects by this therapy is also exhibited. This user-friendly, highly-effective bioengineering technique will contribute to future success of MSC-based therapy.

Cancer metastasis versus stem cell homing: Role of platelets

One of the major obstacles in achieving a successful stem cell therapy is insufficient homing of transplanted cells. To overcome this obstacle, understanding the underlying mechanisms of stem cell homing is of obvious importance. Central to this review is the concept that cancer metastasis can be viewed as a role model to build up a comprehensive concept of stem cell homing. In this novel perspective, the prosurvival choices of the cancerous cells in the bloodstream, their arrest, extravasation, and proliferation at the secondary site can be exploited in favor of targeted stem cell homing. To date, tumor cells have been found to employ a wide variety of strategies to promote metastasis. One of these strategies is through their ability to activate platelets and subsequently activated platelets serve cancer cell survival and metastasis. Accordingly, in the first part of this review the roles of platelets in cancer metastasis as well as stem cell homing are discussed. Next, we provide some lessons learned from cancer metastasis in favor of developing strategies for improvement of stem cell homing with emphasis on the role of platelets. Based on direct or indirect evidence from metastasis, strategies such as manipulation of stem cells to enhance interaction with platelets, preconditioning-pretreatment of stem cells with platelets in vitro, and coinjection of both stem cells and platelets are proposed to improve stem cell homing.

Fibrin Glue-aided, Instant Epicardial Placement Enhances the Efficacy of Mesenchymal Stromal Cell-Based Therapy for Heart Failure

Transplantation of mesenchymal stromal cells (MSCs) is a promising new therapy for heart failure. However, the current cell delivery routes result in poor donor cell engraftment. We therefore explored the role of fibrin glue (FG)-aided, instant epicardial placement to enhance the efficacy of MSC-based therapy in a rat ischemic cardiomyopathy model. We identified a feasible and reproducible method to instantly produce a FG-MSC complex directly on the heart surface. This complex exhibited prompt, firm adhesion to the heart, markedly improving initial retention of donor MSCs compared to intramyocardial injection. In addition, maintenance of retained MSCs was enhanced using this method, together contributing the increased donor cell presence. Such increased donor cell quantity using the FG-aided technique led to further improved cardiac function in association with augmented histological myocardial repair, which correlated with upregulation of tissue repair-related genes. We identified that the epicardial layer was eliminated shortly after FG-aided epicardial placement of MSCs, facilitating permeation of the donor MSC's secretome into the myocardium enabling myocardial repair. These data indicate that FG-aided, on-site, instant epicardial placement enhances MSC engraftment, promoting the efficacy of MSC-based therapy for heart failure. Further development of this accessible, advanced MSC-therapy is justified.

Cell therapy for heart disease after 15 years: Unmet expectations

Over the past two decades cardiac cell therapy (CCT) has emerged as a promising new strategy to cure heart diseases at high unmet need. Thousands of patients have entered clinical trials for acute or chronic heart conditions testing different cell types, including autologous or allogeneic bone marrow (BM)-derived mononuclear or selected cells, BM- or adipose tissue-derived mesenchymal cells, or cardiac resident progenitors based on their potential ability to regenerate scarred or dysfunctional myocardium. Nowadays, the original enthusiasm surrounding the regenerative medicine field has been cushioned by a cumulative body of evidence indicating an inefficient or modest efficacy of CCT in improving cardiac function, along with the continued lack of indisputable proof for long-term prognostic benefit. In this review, we have firstly comprehensively outlined the positive and negative results of cell therapy studies in patients with acute myocardial infarction, refractory angina and chronic heart failure. Next, we have discussed cell therapy- and patient-related variables (e.g. cell intrinsic and extrinsic characteristics as well as criteria of patient selection and proposed methodologies) that might have dampened the efficacy of past cell therapy trials. Finally, we have addressed critical factors to be considered before embarking on further clinical trials.

Intravenous Administration of Adipose-Derived Stem Cell Protein Extracts Improves Neurological Deficits in a Rat Model of Stroke

Treatment of adipose-derived stem cell (ADSC) substantially improves the neurological deficits during stroke by reducing neuronal injury, limiting proinflammatory immune responses, and promoting neuronal repair, which makes ADSC-based therapy an attractive approach for treating stroke. However, the potential risk of tumorigenicity and low survival rate of the implanted cells limit the clinical use of ADSC. Cell-free extracts from ADSC (ADSC-E) may be a feasible approach that could overcome these limitations. Here, we aim to explore the potential usage of ADSC-E in treating rat transient middle cerebral artery occlusion (tMCAO). We demonstrated that intravenous (IV) injection of ADSC-E remarkably reduces the ischemic lesion and number of apoptotic neurons as compared to other control groups. Although ADSC and ADSC-E treatment results in a similar degree of a long-term clinical beneficial outcome, the dynamics between two ADSC-based therapies are different. While the injection of ADSC leads to a relatively mild but prolonged therapeutic effect, the administration of ADSC-E results in a fast and pronounced clinical improvement which was associated with a unique change in the molecular signature suggesting that potential mechanisms underlying different therapeutic approach may be different. Together these data provide translational evidence for using protein extracts from ADSC for treating stroke.

Cell Size Critically Determines Initial Retention of Bone Marrow Mononuclear Cells in the Heart after Intracoronary Injection: Evidence from a Rat Model

Intracoronary injection of bone marrow mononuclear cells (BMMNC) is an emerging treatment for heart failure. Initial donor cell retention in the heart is the key to the success of this approach, but this process remains insufficiently characterized. Although it is assumed that cell size of injected cells may influence their initial retention, no scientific evidence has been reported. We developed a unique model utilizing an ex-vivo rat heart perfusion system, enabling quantitative assessment of retention of donor cells after intracoronary injection. The initial (5 minutes after intracoronary injection) retention rate of BMMNC was as low as approximately 20% irrespective of donor cell doses injected (1×10⁶, 8×10⁶, 4×10⁷). Quantitative cell-size assessment revealed a positive relationship between the size of BMMNC and retention ratio; larger subpopulations of BMMNC were more preferentially retained compared to smaller ones. Furthermore, a larger cell type—bone marrow-derived mesenchymal stromal cells (median size = 11.5μm versus 7.0μm for BMMNC)—had a markedly increased retention rate (77.5±1.8%). A positive relationship between the cell size and retention ratio was also seen in mesenchymal stromal cells. Flow-cytometric studies showed expression of cell-surface proteins, including integrins and selectin-ligands, was unchanged between pre-injection BMMNC and those exited from the heart, suggesting that biochemical interaction between donor cells and host coronary endothelium is not critical for BMMNC retention. Histological analyses showed that retained BMMNC and mesenchymal stromal cells were entrapped in the coronary vasculature and did not extravasate by 60 minutes after transplantation. Whilst BMMNC did not change coronary flow after intracoronary injection, mesenchymal stromal cells reduced it, suggesting coronary embolism, which was supported by the histological finding of intravascular cell-clump formation. These data indicate that cell-size dependent, passive (mechanical), intravascular entrapment is responsible for the initial donor cell retention after intracoronary injection of BMMNC in the heart having normal vasculatures (at least).

Engineered Biomaterials to Enhance Stem Cell-Based Cardiac Tissue Engineering and Therapy

Cardiovascular disease is a leading cause of death worldwide. Since adult cardiac cells are limited in their proliferation, cardiac tissue with dead or damaged cardiac cells downstream of the occluded vessel does not regenerate after myocardial infarction. The cardiac tissue is then replaced with nonfunctional fibrotic scar tissue rather than new cardiac cells, which leaves the heart weak. The limited proliferation ability of host cardiac cells has motivated investigators to research the potential cardiac regenerative ability of stem cells. Considerable progress has been made in this endeavor. However, the optimum type of stem cells along with the most suitable matrix-material and cellular microenvironmental cues are yet to be identified or agreed upon. This review presents an overview of various types of biofunctional materials and biomaterial matrices, which in combination with stem cells, have shown promises for cardiac tissue replacement and reinforcement. Engineered biomaterials also have applications in cardiac tissue engineering, in which tissue constructs are developed in vitro by combining stem cells and biomaterial scaffolds for drug screening or eventual implantation. This review highlights the benefits of using biomaterials in conjunction with stem cells to repair damaged myocardium and give a brief description of the properties of these biomaterials that make them such valuable tools to the field.

Directing and Potentiating Stem Cell-Mediated Angiogenesis and Tissue Repair by Cell Surface E-Selectin Coating

Stem cell therapy has emerged as a promising approach for treatment of a number of diseases, including delayed and non-healing wounds. However, targeted systemic delivery of therapeutic cells to the dysfunctional tissues remains one formidable challenge. Herein, we present a targeted nanocarrier-mediated cell delivery method by coating the surface of the cell to be delivered with dendrimer nanocarriers modified with adhesion molecules. Infused nanocarrier-coated cells reach to destination via recognition and association with the counterpart adhesion molecules highly or selectively expressed on the activated endothelium in diseased tissues. Once anchored on the activated endothelium, nanocarriers-coated transporting cells undergo transendothelial migration, extravasation and homing to the targeted tissues to execute their therapeutic role. We now demonstrate feasibility, efficacy and safety of our targeted nanocarrier for delivery of bone marrow cells (BMC) to cutaneous wound tissues and grafted corneas and its advantages over conventional BMC transplantation in mouse models for wound healing and neovascularization. This versatile platform is suited for targeted systemic delivery of virtually any type of therapeutic cell.

Stem cell death and survival in heart regeneration and repair

Cardiovascular diseases are major causes of mortality and morbidity. Cardiomyocyte apoptosis disrupts cardiac function and leads to cardiac decompensation and terminal heart failure. Delineating the regulatory signaling pathways that orchestrate cell survival in the heart has significant therapeutic implications. Cardiac tissue has limited capacity to regenerate and repair. Stem cell therapy is a successful approach for repairing and regenerating ischemic cardiac tissue; however, transplanted cells display very high death percentage, a problem that affects success of tissue regeneration. Stem cells display multipotency or pluripotency and undergo self-renewal, however these events are negatively influenced by upregulation of cell death machinery that induces the significant decrease in survival and differentiation signals upon cardiovascular injury. While efforts to identify cell types and molecular pathways that promote cardiac tissue regeneration have been productive, studies that focus on blocking the extensive cell death after transplantation are limited. The control of cell death includes multiple networks rather than one crucial pathway, which underlies the challenge of identifying the interaction between various cellular and biochemical components. This review is aimed at exploiting the molecular mechanisms by which stem cells resist death signals to develop into mature and healthy cardiac cells. Specifically, we focus on a number of factors that control death and survival of stem cells upon transplantation and ultimately affect cardiac regeneration. We also discuss potential survival enhancing strategies and how they could be meaningful in the design of targeted therapies that improve cardiac function.

Cell surface glycoengineering improves selectin-mediated adhesion of mesenchymal stem cells (MSCs) and cardiosphere-derived cells (CDCs): Pilot validation in porcine ischemia-reperfusion model

Promising results are emerging in clinical trials focused on stem cell therapy for cardiology applications. However, the low homing and engraftment of the injected cells to target tissue continues to be a problem. Cellular glycoengineering can address this limitation by enabling the targeting of stem cells to sites of vascular injury/inflammation. Two such glycoengineering methods are presented here: i. The non-covalent incorporation of a P-selectin glycoprotein ligand-1 (PSGL-1) mimetic 19Fc[FUT7(+)] via lipid-protein G fusion intermediates that intercalate onto the cell surface, and ii. Over-expression of the α(1,3)fucosyltransferse FUT7 in cells. Results demonstrate the efficient coupling of 19Fc[FUT7(+)] onto both cardiosphere-derived cells (CDCs) and mesenchymal stem cells (MSCs), with coupling being more efficient when using protein G fused to single-tailed palmitic acid rather than double-tailed DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine). This non-covalent cellular modification was mild since cell proliferation and stem-cell marker expression was unaltered. Whereas coupling using 19Fc[FUT7(+)] enhanced cell capture on recombinant P-selectin or CHO-P cell surfaces, α(1,3)fucosylation was necessary for robust binding to E-selectin and inflamed endothelial cells under shear. Pilot studies confirm the safety and homing efficacy of the modified stem cells to sites of ischemia-reperfusion in the porcine heart. Overall, glycoengineering with physiological selectin-ligands may enhance stem cell engraftment.

Bone marrow-derived mesenchymal stem cells for the treatment of heart failure

Heart failure remains a major cause of death and disability, requiring rapid development of new therapies. Bone marrow-derived mesenchymal stem cell (MSC)-based therapy is an emerging approach for the treatment of both acute and chronic heart failure. Following successful experimental studies in a range of models, more than 40 clinical trials of MSC-based therapy for heart failure have now been registered, and the results of completed clinical trials so far have shown feasibility and safety of this approach with therapeutic potential suggested (though preliminarily). However, there appear to be several critical issues to be solved before this treatment could become a widespread standard therapy for heart failure. In this review, we comprehensively and systemically summarize a total of 73 preclinical studies and 11 clinical trial reports published to date. By analyzing the data in these reports, (1) improvement in the cell delivery method to the heart in order to enhance donor cell engraftment, (2) elucidation of mechanisms underpinning the therapeutic effects of the treatment differentiation and/or treatment secretion, and (3) validation of the utility of allogeneic MSCs which could enhance the efficacy and expand the application/indication of this therapeutic approach are highlighted as future perspectives. These important respects are further discussed in this review article with referencing latest scientific and clinical information.

VEGF165Amicrosphere therapy for myocardial infarction suppresses acute cytokine release and increases microvascular density but does not improve cardiac function

Angiogenesis induced by growth factor-releasing microspheres can be an off-the-shelf and immediate alternative to stem cell therapy for acute myocardial infarction (AMI), independent of stem cell yield and comorbidity-induced dysfunction. Reliable and prolonged local delivery of intact proteins such as VEGF is, however, notoriously difficult. Our objective was to create a platform for local angiogenesis in human-sized hearts, using polyethylene-glycol/polybutylene-terephthalate (PEG-PBT) microsphere-based VEGF165Adelivery. PEG-PBT microspheres were biocompatible, distribution was size dependent, and a regimen of 10 × 10615-μm microspheres at 0.5 × 106/min did not induce cardiac necrosis. Efficacy, studied in a porcine model of AMI with reperfusion rather than chronic ischemia used for most reported VEGF studies, shows that microspheres were retained for at least 35 days. Acute VEGF165Arelease attenuated early cytokine release upon reperfusion and produced a dose-dependent increase in microvascular density at 5 wk following AMI. However, it did not improve major variables for global cardiac function, left ventricular dimensions, infarct size, or scar composition (collagen and myocyte content). Taken together, controlled VEGF165Adelivery is safe, attenuates early cytokine release, and leads to a dose-dependent increase in microvascular density in the infarct zone but does not translate into changes in global or regional cardiac function and scar composition.

Intramyocardial Autologous Bone Marrow-derived Stem Cells Injection for Ischemic Heart Disease Ineligible for Revascularization: A Systematic Review and Meta-analysis

BACKGROUND AND AIMS

Intramyocardial autologous bone marrow-derived stem cells injection (IM-BMCs) has been used in patients with ischemic heart disease (IHD) who are ineligible for revascularization; however, the procedure has yielded mixed results. The objective of this meta-analysis was to evaluate the safety and therapeutic benefits of this treatment on a relatively large scale.

METHODS

PubMed, EMBASE, and Cochrane Library databases through September 2014 were searched for randomized clinical trials (RCTs) of IM-BMCs to treat IHD. Outcome measures were defined as mortality after treatment, change in left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV) and left ventricular end-diastolic volume (LVEDV). Weighted mean differences for the changes were estimated with a random-effects model.

RESULTS

Nine RCTs were eligible for inclusion. IM-BMCs significantly reduced the risk of mortality (RR, 0.33; 95% CI, 0.17-0.65; p = 0.001). IM-BMCs significantly improved LVEF by 2.57% (95% CI, 0.34-4.80%; p = 0.02) and reduced LVESV by 9.67 mL (95% CI, -16.43 mL to -2.91 mL; p = 0.005). No significant improvement in LVEDV (WMD = 4.73 mL; 95% CI, -7.22 mL to 16.68 mL; p = 0.44) was detected in patients who received IM-BMC therapy.

CONCLUSIONS

IM-BMC therapy showed clinical safety while being used as stand-alone treatment in IHD with no option of revascularization. The therapeutic efficacy requires further confirmation in large well-powered trials with long-term follow-up.

Matrix-specific anchors: a new concept for targeted delivery and retention of therapeutic cells

Biomedical strategies for tissue engineering and repair utilize specific cells, scaffolds, and growth factors to reconstruct elements of damaged tissue. The cellular element of these strategies is limited, however, by poor efficiency of delivery and retention of therapeutic cells in target sites. We propose that the presence of a cellular anchor that is able to specifically bind a defined element of target tissue will facilitate efficient binding and retention of therapeutic cells, thereby promoting repair of the target site. To do so, we engineered an artificial collagen-specific anchor (ACSA) that is able to specifically bind collagen I. The ACSA was engineered by creating a construct comprising rationally designed consecutive domains. The binding specificity of the ACSA was achieved by employing variable regions of a monoclonal antibody that recognizes a unique epitope present in human collagen I. Meanwhile, cell membrane localization of the ACSA was provided by the presence of a transmembrane domain. We determined that the ACSA was localized within cell membranes and interacted with its intended target, that is, collagen I. We have demonstrated that, in comparison to the control, the cells expressing the ACSA attached better to collagen I and exhibited improved retention in sites of seeding. We have also demonstrated that the presence of the ACSA did not interfere with cell proliferation, the biosynthesis of endogenous collagen I, or the biological functions of native collagen receptors. Since the presented cell delivery system utilizes a common characteristic of major connective tissues, namely the presence of collagen I, the findings described here could have a broad positive impact for improving the repair processes of tendon, ligament, bone, intervertebral disc, skin, and other collagen I-rich connective tissues. If successful, the ACSA approach to deliver cells will serve as an outline for developing cell delivery methods that target other elements of extracellular matrices, including other collagen types, laminins, and fibronectins.

Infrared fluorescent protein 1.4 genetic labeling tracks engrafted cardiac progenitor cells in mouse ischemic hearts

Stem cell therapy has a potential for regenerating damaged myocardium. However, a key obstacle to cell therapy’s success is the loss of engrafted cells due to apoptosis or necrosis in the ischemic myocardium. While many strategies have been developed to improve engrafted cell survival, tools to evaluate cell efficacy within the body are limited. Traditional genetic labeling tools, such as GFP-like fluorescent proteins (eGFP, DsRed, mCherry), have limited penetration depths in vivo due to tissue scattering and absorption. To circumvent these limitations, a near-infrared fluorescent mutant of the DrBphP bacteriophytochrome from Deinococcus radiodurans, IFP1.4, was developed for in vivo imaging, but it has yet to be used for in vivo stem/progenitor cell tracking. In this study, we incorporated IFP1.4 into mouse cardiac progenitor cells (CPCs) by a lentiviral vector. Live IFP1.4-labeled CPCs were imaged by their near-infrared fluorescence (NIRF) using an Odyssey scanner following overnight incubation with biliverdin. A significant linear correlation was observed between the amount of cells and NIRF signal intensity in in vitro studies. Lentiviral mediated IFP1.4 gene labeling is stable, and does not impact the apoptosis and cardiac differentiation of CPC. To assess efficacy of our model for engrafted cells in vivo, IFP1.4-labeled CPCs were intramyocardially injected into infarcted hearts. NIRF signals were collected at 1-day, 7-days, and 14-days post-injection using the Kodak in vivo multispectral imaging system. Strong NIRF signals from engrafted cells were imaged 1 day after injection. At 1 week after injection, 70% of the NIRF signal was lost when compared to the intensity of the day 1 signal. The data collected 2 weeks following transplantation showed an 88% decrease when compared to day 1. Our studies have shown that IFP1.4 gene labeling can be used to track the viability of transplanted cells in vivo.

Superparamagnetic iron oxide nanoparticles function as a long-term, multi-modal imaging label for non-invasive tracking of implanted progenitor cells

The purpose of this study was to determine the ability of superparamagnetic iron oxide (SPIO) nanoparticles to function as a long-term tracking label for multi-modal imaging of implanted engineered tissues containing muscle-derived progenitor cells using magnetic resonance imaging (MRI) and X-ray micro-computed tomography (μCT). SPIO-labeled primary myoblasts were embedded in fibrin sealant and imaged to obtain intensity data by MRI or radio-opacity information by μCT. Each imaging modality displayed a detection gradient that matched increasing SPIO concentrations. Labeled cells were then incorporated in fibrin sealant, injected into the atrioventricular groove of rat hearts, and imaged in vivo and ex vivo for up to 1 year. Transplanted cells were identified in intact animals and isolated hearts using both imaging modalities. MRI was better able to detect minuscule amounts of SPIO nanoparticles, while μCT more precisely identified the location of heavily-labeled cells. Histological analyses confirmed that iron oxide particles were confined to viable, skeletal muscle-derived cells in the implant at the expected location based on MRI and μCT. These analyses showed no evidence of phagocytosis of labeled cells by macrophages or release of nanoparticles from transplanted cells. In conclusion, we established that SPIO nanoparticles function as a sensitive and specific long-term label for MRI and μCT, respectively. Our findings will enable investigators interested in regenerative therapies to non-invasively and serially acquire complementary, high-resolution images of transplanted cells for one year using a single label.

Induced pluripotent stem cells for post-myocardial infarction repair: remarkable opportunities and challenges

Coronary artery disease with associated myocardial infarction continues to be a major cause of death and morbidity around the world, despite significant advances in therapy. Patients who have large myocardial infarctions are at highest risk for progressive heart failure and death, and cell-based therapies offer new hope for these patients. A recently discovered cell source for cardiac repair has emerged as a result of a breakthrough reprogramming somatic cells to induced pluripotent stem cells (iPSCs). The iPSCs can proliferate indefinitely in culture and can differentiate into cardiac lineages, including cardiomyocytes, smooth muscle cells, endothelial cells, and cardiac progenitors. Thus, large quantities of desired cell products can be generated without being limited by cellular senescence. The iPSCs can be obtained from patients to allow autologous therapy or, alternatively, banks of human leukocyte antigen diverse iPSCs are possible for allogeneic therapy. Preclinical animal studies using a variety of cell preparations generated from iPSCs have shown evidence of cardiac repair. Methodology for the production of clinical grade products from human iPSCs is in place. Ongoing studies for the safety of various iPSC preparations with regard to the risk of tumor formation, immune rejection, induction of arrhythmias, and formation of stable cardiac grafts are needed as the field advances toward the first-in-man trials of iPSCs after myocardial infarction.

Preconditioning stem cells for in vivo delivery

Stem cells have emerged as promising tools for the treatment of incurable neural and heart diseases and tissue damage. However, the survival of transplanted stem cells is reported to be low, reducing their therapeutic effects. The major causes of poor survival of stem cells in vivo are linked to anoikis, potential immune rejection, and oxidative damage mediating apoptosis. This review investigates novel methods and potential molecular mechanisms for stem cell preconditioning in vitro to increase their retention after transplantation in damaged tissues. Microenvironmental preconditioning (e.g., hypoxia, heat shock, and exposure to oxidative stress), aggregate formation, and hydrogel encapsulation have been revealed as promising strategies to reduce cell apoptosis in vivo while maintaining biological functions of the cells. Moreover, this review seeks to identify methods of optimizing cell dose preparation to enhance stem cell survival and therapeutic function after transplantation.

Ultrasound-guided transthoracic intramyocardial injection in mice

Murine models of cardiovascular disease are important for investigating pathophysiological mechanisms and exploring potential regenerative therapies. Experiments involving myocardial injection are currently performed by direct surgical access through a thoracotomy. While convenient when performed at the time of another experimental manipulation such as coronary artery ligation, the need for an invasive procedure for intramyocardial delivery limits potential experimental designs. With ever improving ultrasound resolution and advanced noninvasive imaging modalities, it is now feasible to routinely perform ultrasound-guided, percutaneous intramyocardial injection. This modality efficiently and reliably delivers agents to a targeted region of myocardium. Advantages of this technique include the avoidance of surgical morbidity, the facility to target regions of myocardium selectively under ultrasound guidance, and the opportunity to deliver injectate to the myocardium at multiple, predetermined time intervals. With practiced technique, complications from intramyocardial injection are rare, and mice quickly return to normal activity on recovery from anesthetic. Following the steps outlined in this protocol, the operator with basic echocardiography experience can quickly become competent in this versatile, minimally invasive technique.

Epicardial placement of mesenchymal stromal cell-sheets for the treatment of ischemic cardiomyopathy; in vivo proof-of-concept study

Transplantation of bone marrow mesenchymal stromal cells (MSCs) is an emerging treatment for heart failure. We have reported that epicardial placement of MSC-sheets generated using temperature-responsive dishes markedly increases donor MSC survival and augments therapeutic effects in an acute myocardial infarction (MI) model, compared to intramyocardial (IM) injection. This study aims to expand this knowledge for the treatment of ischemic cardiomyopathy, which is likely to be more difficult to treat due to mature fibrosis and chronically stressed myocardium. Four weeks after MI, rats underwent either epicardial MSC-sheet placement, IM MSC injection, or sham treatment. At day 28 after treatment, the cell-sheet group showed augmented cardiac function improvement, which was associated with over 11-fold increased donor cell survival at both days 3 and 28 compared to IM injection. Moreover, the cell-sheet group showed improved myocardial repair, in conjunction with amplified upregulation of a group of reparative factors. Furthermore, by comparing with our own previous data, this study highlighted similar dynamics and behavior of epicardially placed MSCs in acute and chronic stages after MI, while the acute-phase myocardium may be more responsive to the stimuli from donor MSCs. These proof-of-concept data encourage further development of the MSC-sheet therapy for ischemic cardiomyopathy toward clinical application.

Maximum efficacy of mesenchymal stem cells in rat model of renal ischemia-reperfusion injury: renal artery administration with optimal numbers

Backgrounds

Despite the potential therapeutic benefits, cell therapy in renal ischemia-reperfusion (I/R) injury is currently limited by low rates of cell engraftment after systemic delivery. In this study, we investigate whether locally administration through renal artery can enhance the migration and therapeutic potential of mesenchymal stem cells (MSCs) in ischemic kidney.

Methods

The model of renal I/R injury was induced by 45 min occlusion of the left renal pedicle and right nephrectomy in rat. Followed by reperfusion, graded doses of CM-Dil labeled MSCs were implanted via three routes: tail vein (TV), carotid artery (CA), and renal artery (RA). Renal blood flow was evaluated by color and spectral Doppler ultrasound at 1 h and 24 h post-I/R. All the samples were collected for analysis at 24 h post-I/R.

Results

After injection of 1×10⁶ MSCs, RA group showed obviously increased renal retention of grafted MSCs compared with TV and CA group; however, the renal function was even further deteriorated. When graded doses of MSCs, the maximal therapeutic efficiency was achieved with renal artery injection of 1×10⁵ MSCs, which was significantly better than TV and CA group of 1×10⁶ MSCs. In addition, further fluorescent microscopic and ultrasonic examination confirmed that the aggravated renal dysfunction in RA group was due to renal hypoperfusion caused by cell occlusion.

Conclusion

Administration route and dosage are two critical factors determining the efficiency of cell therapy and 1×10⁵ MSCs injected through renal artery produces the most dramatic improvement in renal function and morphology in rat model of renal I/R injury.

Tracking the Fate of Muscle-derived Stem Cells: an Insight into the Distribution and Mode of Action

Purpose:

To examine the fate of muscle-derived stem cells (MDSC) after injection into different host conditions and provide an insight for their mechanism of action.

Materials and Methods:

MDSCs differentiated in vitro towards the endothelial lineage and transfected with lentivirus tagged with green fluorescent protein (GFP) were injected into two animal models mimicking vascular diseases: hindlimb ischemia and carotid injury models. Injected cells were tracked at the site of injection and in remote organs by harvesting the respective tissues at different time intervals and performing immunofluorescent histological analyses. Stem cell survival was quantified at the site of injection for up to 4 weeks.

Results:

MDSCs were successfully tagged with fluorescent material GFP and showed successful implantation into the respective injection sites. These cells showed a higher affinity to implant in blood vessel walls as shown by double fluorescent co-stain with CD31. Quantification of stem cell survival showed a timede pendent decrease from day 3 to 4 weeks (survival rate normalized against day 3 was 72.0% at 1 week, 26.8% at 2 weeks and 2.4% at 4 weeks). Stem cells were also found in distant organs, especially the kidneys and liver, which survived up to 4 weeks.

Conclusion:

MDSCs were successfully tracked in different vascular disease models, and their fate was assessed in terms of cell survival and distribution. Better understanding of the donor cell properties, including their interaction with the host conditions and their mechanism of action, are needed to enhance cell survival and achieve improved outcomes.

Diminishing impairments in glucose uptake, mitochondrial content, and ADP-stimulated oxygen flux by mesenchymal stem cell therapy in the infarcted heart

A constant provision of ATP is of necessity for cardiac contraction. As the heart progresses toward failure following a myocardial infarction (MI), it undergoes metabolic alterations that have the potential to compromise the ability to meet energetic demands. This study evaluated the efficacy of mesenchymal stem cell (MSC) transplantation into the infarcted heart to minimize impairments in the metabolic processes that contribute to energy provision. Seven and twenty-eight days following the MI and MSC transplantation, MSC administration minimized cardiac systolic dysfunction. Hyperinsulinemic-euglycemic clamps, coupled with 2-[(14)C]deoxyglucose administration, were employed to assess systemic insulin sensitivity and tissue-specific, insulin-mediated glucose uptake 36 days following the MI in the conscious, unrestrained, C57BL/6 mouse. The improved systolic performance in MSC-treated mice was associated with a preservation of in vivo insulin-stimulated cardiac glucose uptake. Conserved glucose uptake in the heart was linked to the ability of the MSC treatment to diminish the decline in insulin signaling as assessed by Akt phosphorylation. The MSC treatment also sustained mitochondrial content, ADP-stimulated oxygen flux, and mitochondrial oxidative phosphorylation efficiency in the heart. Maintenance of mitochondrial function and density was accompanied by preserved peroxisome proliferator-activated receptor-γ coactivator-1α, a master regulator of mitochondrial biogenesis. These studies provide insight into mechanisms of action that lead to an enhanced energetic state in the infarcted heart following MSC transplantation that may assist in energy provision and dampen cardiac dysfunction.

Mesenchymal stem cell transplantation for the infarcted heart: therapeutic potential for insulin resistance beyond the heart

Background

This study aimed to evaluate the efficacy of mesenchymal stem cell (MSC) transplantation to mitigate abnormalities in cardiac-specific and systemic metabolism mediated by a combination of a myocardial infarction and diet-induced insulin resistance.

Methods

C57BL/6 mice were high-fat fed for eight weeks prior to induction of a myocardial infarction via chronic ligation of the left anterior descending coronary artery. MSCs were administered directly after myocardial infarction induction through a single intramyocardial injection. Echocardiography was performed prior to the myocardial infarction as well as seven and 28 days post-myocardial infarction. Hyperinsulinemic-euglycemic clamps coupled with 2-[¹⁴C]deoxyglucose were employed 36 days post-myocardial infarction (13 weeks of high-fat feeding) to assess systemic insulin sensitivity and insulin-mediated, tissue-specific glucose uptake in the conscious, unrestrained mouse. High-resolution respirometry was utilized to evaluate cardiac mitochondrial function in saponin-permeabilized cardiac fibers.

Results

MSC administration minimized the decline in ejection fraction following the myocardial infarction. The greater systolic function in MSC-treated mice was associated with increased in vivo cardiac glucose uptake and enhanced mitochondrial oxidative phosphorylation efficiency. MSC therapy promoted reductions in fasting arterial glucose and fatty acid concentrations. Additionally, glucose uptake in peripheral tissues including skeletal muscle and adipose tissue was elevated in MSC-treated mice. Enhanced glucose uptake in these tissues was associated with improved insulin signalling as assessed by Akt phosphorylation and prevention of a decline in GLUT4 often associated with high-fat feeding.

Conclusions

These studies provide insight into the utility of MSC transplantation as a metabolic therapy that extends beyond the heart exerting beneficial systemic effects on insulin action.

Choice of cell-delivery route for successful cell transplantation therapy for the heart

The cell-delivery route is one of the major factors influencing the therapeutic effect and complications of cell transplantation therapy for cardiac diseases. There are four major clinically practical routes, with each method having its own advantages and disadvantages. First, intramyocardial injection allows targeted cell delivery into the areas of interest, although this induces mechanical injury, inflammation and islet-like donor cell clusters, leading to limited donor cell survival and arrhythmogenicity. Second, intracoronary injection is less likely to induce inflammation, whereas poor initial cell retention in the heart is a concern. Third, intravenous injection is easy and economical, but cell recruitment into the heart is not frequent. Finally, epicardial placement of 'cell sheets' enables higher efficiency of cell engraftment, but poor integration into the myocardium may be an issue. This review summarizes up-to-date clinical and preclinical knowledge regarding these cell-delivery methods. We further discuss the ways to refine these methods towards optimizing cell transplantation therapy for the heart.