Reduction of Myocardial Scar Size after Implantation of Mesenchymal Stem Cells in Rats: What Is the Mechanism?

A Polypyrrole-Polycarbonate Polyurethane Elastomer Alleviates Cardiac Arrhythmias via Improving Bio-Conductivity

Myocardial fibrosis, resulting from myocardial infarction (MI), significantly alters cardiac electrophysiological properties. As fibrotic scar tissue forms, its resistance to incoming action potentials increases, leading to cardiac arrhythmia, and eventually sudden cardiac death or heart failure. Biomaterials are gaining increasing attention as an approach for addressing post-MI arrhythmias. The current study investigates the hypothesis that a bio-conductive epicardial patch can electrically synchronize isolated cardiomyocytes in vitro and rescue arrhythmic hearts in vivo. A new conceived biocompatible, conductive, and elastic polyurethane composite bio-membrane, referred to as polypyrrole-polycarbonate polyurethane (PPy-PCNU), is developed, in which solid-state conductive PPy nanoparticles are distributed throughout an electrospun aliphatic PCNU nanofiber patch in a controlled manner. Compared to PCNU alone, the resulting biocompatible patch demonstrates up to six times less impedance, with no conductivity loss over time, as well as being able to influence cellular alignment. Furthermore, PPy-PCNU promotes synchronous contraction of isolated neonatal rat cardiomyocytes and alleviates atrial fibrillation in rat hearts upon epicardial implantation. Taken together, epicardially-implanted PPy-PCNU could potentially serve as a novel alternative approach for the treatment of cardiac arrhythmias.

Transmural myocardial repair with engineered heart muscle in a rat model of heterotopic heart transplantation - A proof-of-concept study

Engineered heart muscle (EHM) can be implanted epicardially to remuscularize the failing heart. In case of a severely scarred ventricle, excision of scar followed by transmural heart wall replacement may be a more desirable application. Accordingly, we tested the hypothesis that allograft (rat) and xenograft (human) EHM can also be administered as transmural heart wall replacement in a heterotopic, volume-loaded heart transplantation model. We first established a novel rat model model to test surgical transmural left heart wall repair. Subsequently and in continuation of our previous allograft studies, we tested outcome after implantation of contractile engineered heart muscle (EHM) and non-contractile engineered connective tissue (ECT) as well as engineered mesenchymal tissue (EMT) allografts as transmural heart wall replacement. Finally, proof-of-concept for the application of human EHM was obtained in an athymic nude rat model. Only in case of EHM implantation, remuscularization of the surgically created transmural defect was observed with palpable graft vascularization. Taken together, feasibility of transmural heart repair using bioengineered myocardial grafts could be demonstrated in a novel rat model of heterotopic heart transplantation.

Extracellular Vesicles Derived From Human Umbilical Cord Mesenchymal Stem Cells Protect Against DOX-Induced Heart Failure Through the miR-100-5p/NOX4 Pathway

The end result of a variety of cardiovascular diseases is heart failure. Heart failure patients’ morbidity and mortality rates are increasing year after year. Extracellular vesicles (EVs) derived from human umbilical cord mesenchymal stem cells (HucMSC-EVs) have recently been discovered to be an alternative treatment for heart failure, according to recent research. In this study, we aimed to explore the underlying mechanisms in which HucMSC-EVs inhibited doxorubicin (DOX)-induced heart failure in AC16 cells. An miR-100-5p inhibitor and an miR-100-5p mimic were used to transfect HucMSCs using Lipofectamine 2000. HucMSC-EVs were isolated and purified using the ultracentrifugation method. AC16 cells were treated with DOX combined with HucMSC-EVs or an EV miR-100-5-p inhibitor or EV miR-100-5-p mimic. ROS levels were measured by a flow cytometer. The levels of LDH, SOD, and MDA were measured by biochemical methods. Apoptotic cells were assessed by a flow cytometer. Cleaved-caspase-3 and NOX4 protein expression were determined by Western blot. The experiment results showed that HucMSC-EVs inhibited DOX-induced increased levels of ROS, LDH, and MDA, and decreased levels of SOD which were reversed by an EV miR-100-5-p inhibitor, while EV miR-100-5-p mimic had a similar effect to HucMSC-EVs. At the same time, HucMSC-EV-inhibited DOX induced the increases of apoptotic cells as well as NOX4 and cleaved-caspase-3 protein expression, which were reversed by an EV miR-100-5-p inhibitor. Furthermore, the NOX4 expression was negatively regulated by miR-100-5p. Overexpression of NOX4 abolished the effects in which HucMSC-EVs inhibited DOX-induced ROS, oxidative stress, and apoptosis increases. In conclusion, these results indicate that HucMSC-EVs inhibit DOX-induced heart failure through the miR-100-5p/NOX4 pathway.

Anti-fibrotic mechanisms of exogenously-expanded mesenchymal stromal cells for fibrotic diseases

Most chronic diseases involving inflammation have a fibrotic component that involves remodeling and excess accumulation of extracellular matrix components. Left unchecked, fibrosis leads to organ failure and death. Mesenchymal stromal cells (MSCs) are emerging as a potent cell-based therapy for a wide spectrum of fibrotic conditions due to their immunomodulatory, anti-inflammatory and anti-fibrotic properties. This review provides an overview of known mechanisms by which MSCs mediate their anti-fibrotic actions and in relation to animal models of pulmonary, liver, renal and cardiac fibrosis. Recent MSC clinical trials results in liver, lung, skin, kidney and hearts are discussed and next steps for future MSC-based therapies including pre-activated or genetically-modified cells, or extracellular vesicles are also considered.

Stem Cell and Advanced Nano Bioceramic Interactions

Bioceramics are type of biomaterials generally used for orthopaedic applications due to their similar structure with bone. Especially regarding to their osteoinductivity and osteoconductivity, they are used as biodegradable scaffolds for bone regeneration along with mesenchymal stem cells. Since chemical properties of bioceramics are important for regeneration of tissue, physical properties are also important for cell proliferation. In this respect, several different manufacturing methods are used for manufacturing nano scale bioceramics. These nano scale bioceramics are used for regeneration of bone and cartilage both alone or with other types of biomaterials. They can also act as carrier for the delivery of drugs in musculoskeletal infections without causing any systemic toxicity.

Mesenchymal Stem Cells and the Treatment of Cardiac Disease

The ischemia-induced death of cardiomyocytes results in scar formation and reduced contractility of the ventricle. Several preclinical and clinical studies have supported the notion that cell therapy may be used for cardiac regeneration. Most attempts for cardiomyoplasty have considered the bone marrow as the source of the “repair stem cell(s),” assuming that the hematopoietic stem cell can do the work. However, bone marrow is also the residence of other progenitor cells, including mesenchymal stem cells (MSCs). Since 1995 it has been known that under in vitro conditions, MSCs differentiate into cells exhibiting features of cardiomyocytes. This pioneer work was followed by many preclinical studies that revealed that ex vivo expanded, bone marrow–derived MSCs may represent another option for cardiac regeneration. In this work, we review evidence and new prospects that support the use of MSCs in cardiomyoplasty.

Novel therapeutic strategies targeting fibroblasts and fibrosis in heart disease

Our understanding of the functions of cardiac fibroblasts has moved beyond their roles in heart structure and extracellular matrix generation and now includes their contributions to paracrine, mechanical and electrical signalling during ontogenesis and normal cardiac activity. Fibroblasts also have central roles in pathogenic remodelling during myocardial ischaemia, hypertension and heart failure. As key contributors to scar formation, they are crucial for tissue repair after interventions including surgery and ablation. Novel experimental approaches targeting cardiac fibroblasts are promising potential therapies for heart disease. Indeed, several existing drugs act, at least partially, through effects on cardiac connective tissue. This Review outlines the origins and roles of fibroblasts in cardiac development, homeostasis and disease; illustrates the involvement of fibroblasts in current and emerging clinical interventions; and identifies future targets for research and development.

Extracellular Vesicles from MSC Modulate the Immune Response to Renal Allografts in a MHC Disparate Rat Model

Application of mesenchymal stromal cells (MSC) has been proposed for solid organ transplantation based on their potent immunomodulatory effects. Since side effects from the injection of large cells cannot be excluded, the hypothesis rises that extracellular vesicles (EV) may cause immunomodulatory effects comparable to MSC without additional side effects. We used MSC-derived EV in a rat renal transplant model for acute rejection. We analysed peripheral blood leukocytes (PBL), kidney function, graft infiltrating cells, cytokines in the graft, and alloantibody development in animals without (allo) and with EV application (allo EV). There was no difference in kidney function and in the PBL subpopulation including Tregs between allo and allo EV. In the grafts T- and B-cell numbers were significantly higher and NK-cells lower in the allo EV kidneys compared to allo. TNF-α transcription was lower in allo EV grafts compared to allo; there was no difference regarding IL-10 and in the development of alloantibodies. In conclusion, the different cell infiltrates and cytokine transcription suggest distinct immunomodulatory properties of EV in allotransplantation. While the increased T- and B-cells in the allo EV grafts may represent a missing or negative effect on the adaptive immune system, EV seem to influence the innate immune system in a contrary fashion.

Biomechanical Screening of Cell Therapies for Vocal Fold Scar

Candidate cell sources for vocal fold scar treatment include mesenchymal stromal cells from bone marrow (BM-MSC) and adipose tissue (AT-MSC). Mechanosensitivity of MSC can alter highly relevant aspects of their behavior, yet virtually nothing is known about how MSC might respond to the dynamic mechanical environment of the larynx. Our objective was to evaluate MSC as a potential cell source for vocal fold tissue engineering in a mechanically relevant context. A vibratory strain bioreactor and cDNA microarray were used to evaluate the similarity of AT-MSC and BM-MSC to the native cell source, vocal fold fibroblasts (VFF). Posterior probabilities for each of the microarray transcripts fitting into specific expression patterns were calculated, and the data were analyzed for Gene Ontology (GO) enrichment. Significant wound healing and cell differentiation GO terms are reported. In addition, proliferation and apoptosis were evaluated with immunohistochemistry. Results revealed that VFF shared more GO terms related to epithelial development, extracellular matrix (ECM) remodeling, growth factor activity, and immune response with BM-MSC than with AT-MSC. Similarity in glycosaminoglycan and proteoglycan activity dominated the ECM analysis. Analysis of GO terms relating to MSC differentiation toward osteogenic, adipogenic, and chondrogenic lineages revealed that BM-MSC expressed fewer osteogenesis GO terms in the vibrated and scaffold-only conditions compared to polystyrene. We did not evaluate if vibrated BM-MSC recover osteogenic expression markers when returned to polystyrene culture. Immunostaining for Ki67 and cleaved caspase 3 did not vary with cell type or mechanical condition. We conclude that VFF may have a more similar wound healing capacity to BM-MSC than to AT-MSC in response to short-term vibratory strain. Furthermore, BM-MSC appear to lose osteogenic potential in the vibrated and scaffold-only conditions compared to polystyrene, potentially attenuating the risk of osteogenesis for in vivo applications.

Injection of mesenchymal stromal cells into a mechanically stimulated in vitro model of cardiac fibrosis has paracrine effects on resident fibroblasts

BACKGROUND AIMS

Myocardial infarction results in the formation of scar tissue populated by myofibroblasts, a phenotype characterized by increased contractility and matrix deposition. Mesenchymal stromal cells (MSC) delivered to the myocardium can attenuate scar growth and restore cardiac function, though the mechanism is unclear.

METHODS

This study describes a simple yet robust three-dimensional (3D) in vitro co-culture model to examine the paracrine effects of implanted MSC on resident myofibroblasts in a controlled biochemical and mechanical environment. The fibrosis model consisted of fibroblasts embedded in a 3D collagen gel cultured under defined oxygen tensions and exposed to either cyclic strain or interstitial fluid flow. MSC were injected into this model, and the effect on fibroblast phenotype was evaluated 48 h after cell injection.

RESULTS

Analysis of gene and protein expression of the fibroblasts indicated that injection of MSC attenuated the myofibroblast transition in response to reduced oxygen and mechanical stress. Assessment of vascular endothelial growth factor and insulin-like growth factor-1 levels demonstrated that their release by fibroblasts was markedly upregulated in hypoxic conditions but attenuated by strain or fluid flow. In fibroblast-MSC co-cultures, vascular endothelial growth factor levels were increased by hypoxia but not affected by mechanical stimuli, whereas insulin-like growth factor-1 levels were generally low and not affected by experimental conditions.

CONCLUSIONS

This study demonstrates how a 3D in vitro model of the cardiac scar can be used to examine paracrine effects of MSC on the phenotype of resident fibroblasts and therefore illuminates the role of injected progenitor cells on the progression of cardiac fibrosis.

Isogeneic MSC application in a rat model of acute renal allograft rejection modulates immune response but does not prolong allograft survival

Application of mesenchymal stromal cells (MSCs) has been proposed for solid organ transplantation based on their potent immuno-modulatory effects in vitro and in vivo. We investigated the potential of MSCs to improve acceptance of kidney transplants in an MHC-incompatible rat model including isogeneic kidney transplantation (RTx) as control. MSCs were administered i.v. or i.a. at time of transplantation. No immunosuppression was applied. Renal function was monitored by serum-creatinine, histopathology, immunochemistry for graft infiltrating cells and expressions of inflammatory genes. We demonstrated the short-term beneficial effects of MSC injection. In the long term, however, MSC-related life-threatening/shortening events (thrombotic microangiopathy, infarctions, infections) were evident despite decreased T- and B-cell infiltration, lower interstitial inflammation and downregulated inflammatory genes particularly after i.a. MSC injection. We conclude that i.a. MSC administration provides efficient immunomodulation after allogeneic RTx, although timing and co-treatment strategies need further fine-tuning to develop the full potential of powerful cell therapy in solid organ transplantation.

Mesenchymal stem cells overexpressing integrin-linked kinase attenuate cardiac fibroblast proliferation and collagen synthesis through paracrine actions

Mesenchymal stem cells (MSCs) transfected by integrin-linked kinase (ILK) transplantation may improve the function and compliance of the post-infarct cardiac ventricle. We investigated the effect of ILK-modified MSC contiditioned medium (ILK-MSC-CM) on the proliferation of cardiac fibroblasts (CFBs) and collagen synthesis in vitro and in vivo. Myocardial infarction (MI)-induced animals received mesenchymal stem cell conditioned medium (MSC-CM), ILK-MSC-CM, or complete medium alone, subepicardially. A group of animals with MI and no other former intervention served as controls. ILK-MSC-CM inhibited CFB proliferation, reduced the gene expression of type I (Col1a1) and type III collagen (Col3a1), tissue inhibitors of metalloproteinase‑1 (TIMP-1) and ‑2 (TIMP-2), α smooth muscle actin (α-SMA), and connective tissue growth factor (CTGF). It also increased the gene expression of matrix metalloproteinase‑2 (MMP‑2) and -9 (MMP‑9), as measured by qRT-PCR. Four weeks after the left anterior descending (LAD) coronary artery ligation, echocardiographic analysis demonstrated preserved cardiac geometry and contractility in the ILK-MSC-CM treated animals. Decreased infarct size and reduced fibrosis were observed in the ILK-MSC-CM group. Overexpression of ILK regulates paracrine actions of MSCs, and ILK-MSC-CM attenuates CFB proliferation and collagen synthesis through paracrine actions in vitro and in vivo.

Platelet lysate suppresses the expression of lipocalin-type prostaglandin D2 synthase that positively controls adipogenic differentiation of human mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have been shown to display a considerable therapeutic potential in cellular therapies. However, harmful adipogenic maldifferentiation of transplanted MSCs may seriously threaten the success of this therapeutic approach. We have previously demonstrated that using platelet lysate (PL) instead of widely used fetal calf serum (FCS) diminished lipid accumulation in adipogenically stimulated human MSCs and identified, among others, lipocalin-type prostaglandin D2 synthase (L-PGDS) as a gene suppressed in PL-supplemented MSCs. Here, we investigated the role of PL and putatively pro-adipogenic L-PGDS in human MSC adipogenesis. Next to strongly reduced levels of L-PGDS we show that PL-supplemented MSCs display markedly decreased expression of adipogenic master regulators and differentiation markers, both before and after induction of adipocyte differentiation. The low adipogenic differentiation capability of PL-supplemented MSCs could be partially restored by exogenous addition of L-PGDS protein. Conversely, siRNA-mediated downregulation of L-PGDS in FCS-supplemented MSCs profoundly reduced adipocyte differentiation. In contrast, inhibiting endogenous prostaglandin synthesis by aspirin did not reduce differentiation, suggesting that a mechanism such as lipid shuttling but not the prostaglandin D2 synthase activity of L-PGDS is critical for adipogenesis. Our data demonstrate that L-PGDS is a novel pro-adipogenic factor in human MSCs which might be of relevance in adipocyte metabolism and disease. L-PGDS gene expression is a potential quality marker for human MSCs, as it might predict unwanted adipogenic differentiation after MSC transplantation.

Mesenchymal stem cells for cardiac regeneration: translation to bedside reality

Cardiovascular disease (CVD) is the leading cause of death worldwide. According to the World Health Organization (WHO), an estimate of 17.3 million people died from CVDs in 2008 and by 2030, the number of deaths is estimated to reach almost 23.6 million. Despite the development of a variety of treatment options, heart failure management has failed to inhibit myocardial scar formation and replace the lost cardiomyocyte mass with new functional contractile cells. This shortage is complicated by the limited ability of the heart for self-regeneration. Accordingly, novel management approaches have been introduced into the field of cardiovascular research, leading to the evolution of gene- and cell-based therapies. Stem cell-based therapy (aka, cardiomyoplasty) is a rapidly growing alternative for regenerating the damaged myocardium and attenuating ischemic heart disease. However, the optimal cell type to achieve this goal has not been established yet, even after a decade of cardiovascular stem cell research. Mesenchymal stem cells (MSCs) in particular have been extensively investigated as a potential therapeutic approach for cardiac regeneration, due to their distinctive characteristics. In this paper, we focus on the therapeutic applications of MSCs and their transition from the experimental benchside to the clinical bedside.

A toxicity study of multiple-administration human umbilical cord mesenchymal stem cells in cynomolgus monkeys

Therapies based on stem cells have shown very attractive potential in many clinical studies. However, the data about the safety of stem cells application remains insufficient. The present study was designed to evaluate the overall toxicology of human umbilical cord mesenchymal stem cells (hUC-MSCs) in cynomolgus monkeys with repeated administrations. hUC-MSCs were administered by intravenous injection once every 2 weeks for 6 weeks. The dose levels employed in this study were 2×10(6), 1×10(7) cells/kg body weight. Toxicity was evaluated by clinical observations (body weight, body temperature, and ophthalmology exams), pathology (blood cell counts, clinical biochemistry, urinalysis, and bone marrow smears), immunologic consequences (lymphoproliferation assay, the secretion of interferon-γ and interleukin-4, the percentage of CD3, CD4, CD8 T cells, and the ratio of CD4 and CD8 T cells) and anatomic pathology. Pharmacodynamics in blood and distribution of hUC-MSCs in the tissues of cynomolgus monkeys were measured by real-time polymerase chain reaction. All animals survived until scheduled euthanasia. No stem cells transplantation-related toxicity was found in this study. hUC-MSCs could be found in the blood of cynomolgus monkeys beyond 8 h. The findings of this 6-week toxicity study showed that the transplantation of hUC-MSCs did not affect the general health of cynomolgus monkeys.

Advances in bone marrow-derived cell therapy: CD31-expressing cells as next generation cardiovascular cell therapy

In the past few years, bone marrow (BM)-derived cells have been used to regenerate damaged cardiovascular tissues post-myocardial infarction. Recent clinical trials have shown controversial results in recovering damaged cardiac tissue. New progress has shown that the underlying mechanisms of cell-based therapy relies more heavily on humoral and paracrine effects rather than on new tissue generation. However, studies have also reported the potential of new endothelial cell generation from BM cells. Thus, efforts have been made to identify cells having higher humoral or therapeutic effects as well as their surface markers. Specifically, BM-derived CD31+ cells were isolated by a surface marker and demonstrated high angio-vasculogenic effects. This article will describe recent advances in the therapeutic use of BM-derived cells and the usefulness of CD31+ cells.

Mesenchymal stem cells: from experiment to clinic

There is currently much interest in adult mesenchymal stem cells (MSCs) and their ability to differentiate into other cell types, and to partake in the anatomy and physiology of remote organs. It is now clear these cells may be purified from several organs in the body besides bone marrow. MSCs take part in wound healing by contributing to myofibroblast and possibly fibroblast populations, and may be involved in epithelial tissue regeneration in certain organs, although this remains more controversial. In this review, we examine the ability of MSCs to modulate liver, kidney, heart and intestinal repair, and we update their opposing qualities of being less immunogenic and therefore tolerated in a transplant situation, yet being able to contribute to xenograft models of human tumour formation in other contexts. However, such observations have not been replicated in the clinic. Recent studies showing the clinical safety of MSC in several pathologies are discussed. The possible opposing powers of MSC need careful understanding and control if their clinical potential is to be realised with long-term safety for patients.

Mesenchymal stromal cells: main factor or helper in regenerative medicine?

Mesenchymal stromal cells (mSCs) are presently studied for the prophylaxis and therapy of a variety of diseases such as acute graft-versus-host disease after allogeneic stem cell transplantation, cardiac indications, bone degeneration, Crohn's disease, and organ rejection, as well as prevention of acute renal failure in high-risk situations. mSCs appear to function through paracrine mechanisms that exert immunosuppressive, anti-inflammatory, anti-apoptotic, mitogenic, and other organ-protective and repair-stimulating actions. mSCs are either cultured in the presence of fetal calf serum (FCS) or platelet lysate (PL). PL lysate-generated mSCs exhibit faster doubling times, different gene expression profiles, and more potent immunosuppressive activity compared with FSC-generated mSCs. The utility of mSCs in the treatment of chronic inflammatory diseases is being evaluated in prospective studies.

Capturing the stem cell paracrine effect using heparin-presenting nanofibres to treat cardiovascular diseases

The mechanism for stem cell-mediated improvement following acute myocardial infarction has been actively debated. We support hypotheses that the stem cell effect is primarily paracrine factor-linked. We used a heparin-presenting injectable nanofibre network to bind and deliver paracrine factors derived from hypoxic conditioned stem cell media to mimic this stem cell paracrine effect. Our self-assembling peptide nanofibres presenting heparin were capable of binding paracrine factors from a medium phase. When these factor-loaded materials were injected into the heart following coronary artery ligation in a mouse ischaemia-reperfusion model of acute myocardial infarction, we found significant preservation of haemodynamic function. Through media manipulation, we were able to determine that crucial factors are primarily < 30 kDa and primarily heparin-binding. Using recombinant VEGF- and bFGF-loaded nanofibre networks, the effect observed with conditioned media was recapitulated. When evaluated in another disease model, a chronic rat ischaemic hind limb, our factor-loaded materials contributed to extensive limb revascularization. These experiments demonstrate the potency of the paracrine effect associated with stem cell therapies and the potential of a biomaterial to bind and deliver these factors, pointing to a potential therapy based on synthetic materials and recombinant factors as an acellular therapy.

Mesenchymal stromal cell and mononuclear cell therapy in heart disease

Despite progress in percutaneous coronary intervention, bypass surgery and drug therapy, rates of mortality and morbidity after acute coronary syndrome are high due to ventricular remodeling and heart failure. Mesenchymal stromal cells (MSCs) from adult bone marrow or adipose tissue are considered potential candidates for therapeutic regenerative treatment in cardiovascular disease. Recent animal studies have demonstrated that MSCs can induce neovascularization and improve myocardial function in postinfarction myocardial ischemic hearts. This review will focus on the present preclinical and clinical knowledge about the use of mononuclear cells and MSCs for cardiac regenerative medicine, the source of MSCs for clinical use and problems to consider when conducting clinical MSC therapy.

LAD-ligation: a murine model of myocardial infarction

Research models of infarction and myocardial ischemia are essential to investigate the acute and chronic pathobiological and pathophysiological processes in myocardial ischemia and to develop and optimize future treatment. Two different methods of creating myocardial ischemia are performed in laboratory rodents. The first method is to create cryo infarction, a fast but inaccurate technique, where a cryo-pen is applied on the surface of the heart (1-3). Using this method the scientist can not guarantee that the cryo-scar leads to ischemia, also a vast myocardial injury is created that shows pathophysiological side effects that are not related to myocardial infarction. The second method is the permanent ligation of the left anterior descending artery (LAD). Here the LAD is ligated with one single stitch, forming an ischemia that can be seen almost immediately. By closing the LAD, no further blood flow is permitted in that area, while the surrounding myocardial tissue is nearly not affected. This surgical procedure imitates the pathobiological and pathophysiological aspects occurring in infarction-related myocardial ischemia. The method introduced in this video demonstrates the surgical procedure of a mouse infarction model by ligating the LAD. This model is convenient for pathobiological and pathophysiological as well as immunobiological studies on cardiac infarction. The shown technique provides high accuracy and correlates well with histological sections.

Cell therapy with bone marrow cells for myocardial regeneration

Cell therapy has tremendous potential for the damaged heart, which has limited self-renewing capability. Bone marrow (BM) cells are attractive for cell therapy, as they contain diverse stem and progenitor cell populations that can give rise to various cell types, including cardiomyocytes, endothelial cells, and smooth muscle cells. Studies have shown BM cells to be safe and efficacious in the treatment of myocardial infarction. Possible therapeutic mechanisms mediated by both host and transplanted cells include cardiomyogenesis, neovascularization, and attenuation of adverse remodeling. In this review, different stem and progenitor cells in the bone marrow and their application in cell therapy are reviewed, and evidence for their therapeutic mechanisms is discussed.

Cardiac stem cell research: an elephant in the room?

Heart disease is the leading cause of death in the industrialized world, and stem cell therapy seems to be a promising treatment for injured cardiac tissue. To reach this goal, the scientific community needs to find a good source of stem cells that can be used to obtain new myocardium in a very period range of time. Since there are many ethical and technical problems with using embryonic stem cells as a source of cells with cardiogenic potential, many laboratories have attempted to isolate potential cardiac stem cells from several tissues. The best candidates seem to be cardiac "progenitor" and/or "stem" cells, which can be isolated from subendocardial biopsies from the same patient or from embryonic and/or fetal myocardium. Regardless of the technique used to isolate and characterize these cells, it appears that the different cells isolated from adult myocardium to date are all phenotypic variations of a unique cell type that expresses several markers, such as c-Kit, CD34, MDR-1, Sca-1, CD45, nestin, or Isl-1, in various combinations.

Cell tracking and therapy evaluation of bone marrow monocytes and stromal cells using SPECT and CMR in a canine model of myocardial infarction

BACKGROUND

The clinical application of stem cell therapy for myocardial infarction will require the development of methods to monitor treatment and pre-clinical assessment in a large animal model, to determine its effectiveness and the optimum cell population, route of delivery, timing, and flow milieu.

OBJECTIVES

To establish a model for a) in vivo tracking to monitor cell engraftment after autologous transplantation and b) concurrent measurement of infarct evolution and remodeling.

METHODS

We evaluated 22 dogs (8 sham controls, 7 treated with autologous bone marrow monocytes, and 7 with stromal cells) using both imaging of 111Indium-tropolone labeled cells and late gadolinium enhancement CMR for up to12 weeks after a 3 hour coronary occlusion. Hearts were also examined using immunohistochemistry for capillary density and presence of PKH26 labeled cells.

RESULTS

In vivo Indium imaging demonstrated an effective biological clearance half-life from the injection site of ~5 days. CMR demonstrated a pattern of progressive infarct shrinkage over 12 weeks, ranging from 67-88% of baseline values with monocytes producing a significant treatment effect. Relative infarct shrinkage was similar through to 6 weeks in all groups, following which the treatment effect was manifest. There was a trend towards an increase in capillary density with cell treatment.

CONCLUSION

This multi-modality approach will allow determination of the success and persistence of engraftment, and a correlation of this with infarct size shrinkage, regional function, and left ventricular remodeling. There were overall no major treatment effects with this particular model of transplantation immediately post-infarct.

Stem cells as a potential future treatment of pediatric intestinal disorders

All surgical disciplines encounter planned and unplanned ischemic events that may ultimately lead to cellular dysfunction and death. Stem cell therapy has shown promise for the treatment of a variety of ischemic and inflammatory disorders where tissue damage has occurred. As stem cells have proven beneficial in many disease processes, important opportunities in the future treatment of gastrointestinal disorders may exist. Therefore, this article will serve to review the different types of stem cells that may be applicable to the treatment of gastrointestinal disorders, review the mechanisms suggesting that stem cells may work for these conditions, discuss current practices for harvesting and purifying stem cells, and provide a concise summary of a few of the pediatric intestinal disorders that could be treated with cellular therapy.

Different cardiovascular potential of adult- and fetal-type mesenchymal stem cells in a rat model of heart cryoinjury

Efficacy of adult (bone marrow, BM) versus fetal (amniotic fluid, AF) mesenchymal stem cells (MSCs) to replenish damaged rat heart tissues with new cardiovascular cells has not yet been established. We investigated on the differentiation potential of these two rat MSC populations in vitro and in a model of acute necrotizing injury (ANI) induced by cryoinjury. Isolated BM-MSCs and AF-MSCs were characterized by flow cytometry and cytocentrifugation and their potential for osteogenic, adipogenic, and cardiovascular differentiation assayed in vitro using specific induction media. The left anterior ventricular wall of syngeneic Fisher 344 (n = 48) and athymic nude (rNu) rats (n = 6) was subjected to a limited, nontransmural epicardial ANI in the approximately one third of wall thickness without significant hemodynamic effects. The time window for in situ stem cell transplantation was established at day 7 postinjury. Fluorochrome (CMTMR)-labeled BM-MSCs (2 x 10(6)) or AF-MSCs (2 x 10(6)) were injected in syngeneic animals (n = 26) around the myocardial lesion via echocardiographic guidance. Reliability of CMTMR cell tracking in this context was ascertained by transplanting genetically labeled BM-MSCs or AF-MSCs, expressing the green fluorescent protein (GFP), in rNu rats with ANI. Comparison between the two methods of cell tracking 30 days after cell transplantation gave slightly different values (1420,58 +/- 129,65 cells/mm2 for CMTMR labeling and 1613.18 +/- 643.84 cells/mm2 for genetic labeling; p = NS). One day after transplantation about one half CMTMR-labeled AF-MSCs engrafted to the injured heart (778.61 +/- 156.28 cells/mm2) in comparison with BM-MSCs (1434.50 +/- 173.80 cells/mm2, p < 0.01). Conversely, 30 days after cell transplantation survived MSCs were similar: 1275.26 +/- 74.51/mm2 (AF-MSCs) versus 1420.58 +/- 129.65/mm2 for BM-MSCs (p = NS). Apparent survival gain of AF-MSCs between the two time periods was motivated by the cell proliferation rate calculated at day 30, which was lower for BM-MSCs (6.79 +/- 0.48) than AF-MSCs (10.83 +/- 3.50; p < 0.01), in the face of a similar apoptotic index (4.68 +/- 0.20 for BM-MSCs and 4.16 +/- 0.58 for AF-MSCs; p = NS). These cells were also studied for their expression of markers specific for endothelial cells (ECs), smooth muscle cells (SMCs), and cardiomyocytes (CMs) using von Willebrand factor (vWf), smooth muscle (SM) alpha-actin, and cardiac troponin T, respectively. Grafted BM-MSCs or AF-MSCs were found as single cell/small cell clusters or incorporated in the wall of microvessels. A larger number of ECs (227.27 +/- 18.91 vs. 150.36 +/- 24.08 cells/mm2, p < 0.01) and CMs (417.91 +/- 100.95 vs. 237.43 +/- 79.99 cells/mm2, p < 0.01) originated from AF-MSCs than from BM-MSCs. Almost no SMCs were seen with AF-MSCs, in comparison to BM-MSCs (98.03 +/- 40.84 cells/mm2), in concordance with lacking of arterioles, which, instead, were well expressed with BM-MSCs (71.30 +/- 55.66 blood vessels/mm2). The number of structurally organized capillaries was slightly different with the two MSCs (122.49 +/- 17.37/mm2 for AF-MSCs vs. 148.69 +/- 54.41/mm2 for BM-MSCs; p = NS). Collectively, these results suggest that, in the presence of the same postinjury microenvironment, the two MSC populations from different sources are able to activate distinct differentiation programs that potentially can bring about a myocardial-capillary or myocardial-capillary-arteriole reconstitution.

Mesenchymal stem cells and cardiac repair

Accumulating clinical and experimental evidence indicates that mesenchymal stem cells (MSCs) are promising cell types in the treatment of cardiac dysfunction. They may trigger production of reparative growth factors, replace damaged cells and create an environment that favours endogenous cardiac repair. However, identifying mechanisms which regulate the role of MSCs in cardiac repair is still at work. To achieve the maximal clinical benefits, ex vivo manipulation can further enhance MSC therapeutic potential. This review focuses on the mechanism of MSCs in cardiac repair, with emphasis on ex vivo manipulation.

An in vivo multimodal imaging study using MRI and PET of stem cell transplantation after myocardial infarction in rats

PURPOSE

The purpose of the study is to track iron-oxide nanoparticle-labelled adult rat bone marrow-derived stem cells (IO-rBMSCs) by magnetic resonance imaging (MRI) and determine their effect in host cardiac tissue using 2-deoxy-2-[F-18]fluoro-D: -glucose-positron emission tomography (FDG-PET).

PROCEDURES

Infarcted rats were randomised to receive (1) live IO-rBMSCs by direct local injection, or (2) dead IO-rBMSCs as controls; (3) sham-operated rats received live IO-rBMSCs. The rats were then imaged from 2 days to 6 weeks post-cell implantation using both MRI at 9.4T and FDG-PET.

RESULTS

Implanted IO-rBMSCs were visible in the heart by MRI for the duration of the study. Histological analysis confirmed that the implanted IO-rBMSCs were present for up to 6 weeks post-implantation. At 1 week post-IO-rBMSC transplantation, PET studies demonstrated an increase in FDG uptake in infarcted regions implanted with live IO-rBMSC compared to controls.

CONCLUSIONS

Noninvasive multimodality imaging allowed us to visualise IO-rBMSCs and establish their affect on cardiac function in a rat model of myocardial infarction (MI).

Seeding bioreactor-produced embryonic stem cell-derived cardiomyocytes on different porous, degradable, polyurethane scaffolds reveals the effect of scaffold architecture on cell morphology

A successful regenerative therapy to treat damage incurred after an ischemic event in the heart will require an integrated approach including methods for appropriate revascularization of the infarct site, mechanical recovery of damaged tissue, and electrophysiological coupling with native cells. Cardiomyocytes are the ideal cell type for heart regeneration because of their inherent electrical and physiological properties, and cardiomyocytes derived from embryonic stem cells (ESCs) represent an attractive option for tissue-engineering therapies. An important step in developing tissue engineering-based approaches to cardiac cell therapy is understanding how scaffold architecture affects cell behavior. In this work, we generated large numbers of ESC-derived cardiomyocytes in bioreactors and seeded them on porous, 3-dimensional scaffolds prepared using 2 different techniques: electrospinning and thermally induced phase separation (TIPS). The effect of material macro-architecture on the adhesion, viability, and morphology of the seeded cells was determined. On the electrospun scaffolds, cells were elongated in shape, a morphology typical of cultured ESC-derived cardiomyocytes, whereas on scaffolds fabricated using TIPS, the cells retained a rounded morphology. Despite these gross phenotypic and physiological differences, sarcomeric myosin and connexin 43 expression was evident, and contracting cells were observed on both scaffold types, suggesting that morphological changes induced by material macrostructure do not directly correlate to functional differences.

Bone marrow-derived mesenchymal stem cells for treatment of heart failure: is it all paracrine actions and immunomodulation?

Despite significant advances in medical and surgical management of heart failure, mostly of ischaemic origin, the mortality and morbidity associated with it continue to be high. Pluripotent stem cells are being evaluated for treatment of heart failure. Bone marrow-derived mesenchymal stem cells (MSCs) have been extensively studied. Emerging evidence suggests that locally delivered MSCs can lead to an improvement in ventricular function, but the cellular and molecular mechanisms involved remain unclear. Myocardial regeneration, as proposed by many researchers as the underlying mechanism, has failed to convince the scientific community. Recently some authors have ascribed improvement in ventricular function to paracrine actions of MSCs.A lot has been written about the host immune response triggered by embryonic stem cells and the consequent need for immunosuppression. Not enough work has been done on immune interactions involving allogeneic bone marrow cells. Full potential of stem cell therapy can be realised only when we are able to use allogeneic cells. The potential use of MSCs in cellular therapy has recently prompted researchers to look into their interaction with the host immune response. MSCs have immunomodulatory properties. They cause suppression of proliferation of alloreactive T cells in a dose-dependent manner.Tissue injury causes inflammation and release of several chemokines, cytokines and growth factors. They can cause recruitment of bone marrow-derived MSCs to the injured area. We review the literature on paracrine actions and immune interactions of allogeneic MSCs.

Early improvement in cardiac tissue perfusion due to mesenchymal stem cells

The underlying mechanism(s) of improved left ventricular function (LV) due to mesenchymal stem cell (MSC) administration after myocardial infarction (MI) remains highly controversial. Myocardial regeneration and neovascularization, which leads to increased tissue perfusion, are proposed mechanisms. Here we demonstrate that delivery of MSCs 3 days after MI increased tissue perfusion in a manner that preceded improved LV function in a porcine model. MI was induced in pigs by 60-min occlusion of the left anterior descending coronary artery, followed by reperfusion. Pigs were assigned to receive intramyocardial injection of allogeneic MSCs (200 million, approximately 15 injections) (n = 10), placebo (n = 6), or no intervention (n = 8). Resting myocardial blood flow (MBF) was serially assessed by first-pass perfusion magnetic resonance imaging (MRI) over an 8-wk period. Over the first week, resting MBF in the infarct area of MSC-treated pigs increased compared with placebo-injected and untreated animals [0.17 +/- 0.03, 0.09 +/- 0.01, and 0.08 +/- 0.01, respectively, signal intensity ratio of MI to left ventricular blood pool (LVBP); P < 0.01 vs. placebo, P < 0.01 vs. nontreated]. In contrast, the signal intensity ratios of the three groups were indistinguishable at weeks 4 and 8. However, MSC-treated animals showed larger, more mature vessels and less apoptosis in the infarct zones and improved regional and global LV function at week 8. Together these findings suggest that an early increase in tissue perfusion precedes improvements in LV function and a reduction in apoptosis in MSC-treated hearts. Cardiac MRI-based measures of blood flow may be a useful tool to predict a successful myocardial regenerative process after MSC treatment.

Human mesenchymal stem cells stimulated by TNF-alpha, LPS, or hypoxia produce growth factors by an NF kappa B- but not JNK-dependent mechanism

Understanding the mechanisms by which adult stem cells produce growth factors may represent an important way to optimize their beneficial paracrine and autocrine effects. Components of the wound milieu may stimulate growth factor production to promote stem cell-mediated repair. We hypothesized that tumor necrosis factor-alpha (TNF-alpha), endotoxin (LPS), or hypoxia may activate human mesenchymal stem cells (MSCs) to increase release of vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), insulin-like growth factor 1 (IGF-1), or hepatocyte growth factor (HGF) and that nuclear factor-kappa B (NF kappa B), c-Jun NH2-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) mediates growth factor production from human MSCs. To study this, human MSCs were harvested, passaged, divided into four groups (100,000 cells, triplicates) and treated as follows: 1) with vehicle; 2) with stimulant alone [24 h LPS (200 ng/ml), 24 h TNF-alpha (50 ng/ml), or 24 h hypoxia (1% O2)]; 3) with inhibitor alone [NF kappa B (PDTC, 1 mM), JNK (TI-JIP, 10 microM), or ERK (ERK Inhibitor II, 25 microM)]; and 4) with stimulant and the various inhibitors. After 24 h incubation, MSC activation was determined by measuring supernatants for VEGF, FGF2, IGF-1, or HGF (ELISA). TNF-alpha, LPS, and hypoxia significantly increased human MSC VEGF, FGF2, HGF, and IGF-1 production versus controls. Stem cells exposed to injury demonstrated increased activation of NF kappa B, ERK, and JNK. VEGF, FGF2, and HGF expression was significantly reduced by NF kappa B inhibition (50% decrease) but not ERK or JNK inhibition. Moreover, ERK, JNK, and NF kappa B inhibitor alone did not activate MSC VEGF expression over controls. Various stressors activate human MSCs to increase VEGF, FGF2, HGF, and IGF-1 expression, which depends on an NFkB mechanism.

STEM CELL MECHANISMS AND PARACRINE EFFECTS

Heart disease remains the leading cause of death in the industrialized world. Stem cell therapy is a promising treatment modality for injured cardiac tissue. A novel mechanism for this cardioprotection may include paracrine actions. Cardiac surgery represents the unique situation where preischemia and postischemia treatment modalities exist that may use stem cell paracrine protection. This review (1) recalls the history of stem cells in cardiac disease and the unraveling of its mechanistic basis for protection, (2) outlines the pathways for stem cell-mediated paracrine protection, (3) highlights the signaling factors expressed, (4) explores the potential of using stem cells clinically in cardiac surgery, and (5) summarizes all human stem cell studies in cardiac disease to date.

In vivo magnetic resonance imaging of iron oxide-labeled, arterially-injected mesenchymal stem cells in kidneys of rats with acute ischemic kidney injury: detection and monitoring at 3T

PURPOSE

To evaluate MRI for a qualitative and quantitative in vivo tracking of intraaortal injected iron oxide-labeled mesenchymal stem cells (MSC) into rats with acute kidney injury (AKI).

MATERIALS AND METHODS

In vitro MRI and R2* measurement of nonlabeled and superparamagnetic iron oxide (SPIO)-labeled MSC (MSC(SPIO)) was performed in correlation to cellular iron content and cytological examination (Prussian blue, electron microscopy). In vivo MRI and R2* evaluation were performed before and after ischemic/reperfusion AKI (N = 14) and intraaortal injection of 1.5 x 10(6) MSC(SPIO) (N = 7), fetal calf serum (FCS) (medium, N = 6), and SPIO alone (N = 1) up to 14 days using a clinical 3T scanner. Signal to noise ratios (SNR), R2* of kidneys, liver, spleen, and bone marrow, renal function (creatinine [CREA], blood urea nitrogen [BUN]), and kidney volume were measured and tested for statistical significance (Student's t-test, P < 0.05) in comparison histology (hematoxylin and eosin [H&E], Prussian blue, periodic acid-Schiff [PAS], CD68).

RESULTS

In vitro, MSC(SPIO) showed a reduction of SNR and T2* with R2* approximately number of MSC(SPIO) (R2 = 0.98). In vivo MSC(SPIO) administration resulted in a SNR decrease (35 +/- 15%) and R2* increase (101 +/- 18.3%) in renal cortex caused by MSC(SPIO) accumulation in contrast to control animals (P < 0.01). Liver, spleen, and bone marrow (MSC(SPIO)) showed a delayed SNR decline/R2* increase (P < 0.05) resulting from MSC(SPIO) migration. The increase of kidney volume and the decrease in renal function (P < 0.05) was reduced in MSC-treated animals.

CONCLUSION

Qualitative and quantitative in vivo cell-tracking and monitoring of organ distribution of intraaortal injected MSC(SPIO) in AKI is feasible in MRI at 3T.

Stem Cell Therapy: A Hope for Dying Hearts

The restoration of functional myocardium following heart failure still remains a formidable challenge among researchers. Irreversible damage caused by myocardial infarction is followed by left ventricular remodeling. The current pharmacologic and interventional strategies fail to regenerate dead myocardium and are usually insufficient to meet the challenge caused by necrotic cardiac myocytes. There is growing evidence, suggesting that the heart has the ability to regenerate through the activation of resident cardiac stem cells or through the recruitment of a stem cell population from other tissues such as bone marrow. These new findings belie the earlier conception about the poor regenerating ability of myocardial tissue. Stem cell therapy is a promising new approach for myocardial repair. However, it has been limited by the paucity of cell sources for functional human cardiomyocytes. Moreover, cells isolated from different sources exhibit idiosyncratic characteristics including modes of isolation, ease of expansion in culture, proliferative ability, characteristic markers, etc., which are the basis for several technical manipulations to achieve successful engraftment. Clinical trials show some evidence for the successful integration of stem cells of extracardiac origin in adult human heart with an improved functional outcome. This may be attributed to the discrepancies in the methods of detection, study subject selection (early or late post transplantation), presence of inflammation, and false identification of infiltrating leukocytes. This review discusses these issues in a comprehensive manner so that their physiological significance in animal as well as in human studies can be better understood.

Accelerated and safe expansion of human mesenchymal stromal cells in animal serum-free medium for transplantation and regenerative medicine

Human bone marrow mesenchymal stromal cells (hMSC) are currently investigated for a variety of therapeutic applications. However, most expansion protocols still use fetal calf serum (FCS) as growth factor supplement which is a potential source of undesired xenogeneic pathogens. We established an expansion protocol for hMSC based on the use of GMP-produced basic medium LP02 supplemented with 5% of platelet lysate (PL) obtained from human thrombocyte concentrates. Compared to FCS-supplemented culture conditions, we found a significant increase in both colony forming unit-fibroblast (CFU-F) as well as cumulative cell numbers after expansion. This accelerated growth is optimized by pooling of at least 10 thrombocyte concentrates. A minimal requirement is the use of 5% of PL with an optimal platelet concentration of 1.5 x 10(9)/ml, and centrifugation of thawed lysate at high speed. Cells expanded by this protocol meet all criteria for mesenchymal stromal cells (MSCs), e.g. plastic adherence, spindle-shaped morphology, surface marker expression, lack of hematopoietic markers, and differentiation capability into three mesenchymal lineages. MSC at passage 6 were cytogenetically normal and retained their immune-privileged potential by suppressing allogeneic reaction of T-cells. Additionally, gene expression profiles show increased mRNA levels of genes involved in cell cycle and DNA replication and downregulation of developmental and differentiation genes, supporting the observation of increased MSC-expansion in PL-supplemented medium. In summary, we have established a GMP-compatible protocol for safe and accelerated expansion of hMSC to be used in cell and tissue therapy.

The role of biomaterials in stem cell differentiation: applications in the musculoskeletal system

The capabilities of stem cells continue to be revealed, leading to excitement regarding potential new therapies. Regenerative medicine is an area in which stem cells hold great promise for overcoming the challenge of limited cell sources for tissue repair. Biomaterials play an important role in directing tissue growth and may provide another tool to manipulate and control stem cell behavior. Biomaterials are made from natural or synthetic polymers and can be processed into three-dimensional scaffolds designed to promote cell proliferation and/or differentiation that ultimately produces new tissue. Stem cells will have a significant impact on the fields of regenerative medicine and tissue engineering as a powerful cell source that will work, in conjunction with biomaterials, to treat tissue and organ loss. Herein, we survey our latest research on applying embryonic stem (ES) cells to hydrogel biomaterials for engineering musculoskeletal tissues, emphasizing the unique biomaterial requirements of ES cells for differentiation and tissue development.

Transplantation of a novel cell line population of umbilical cord blood stem cells ameliorates neurological deficits associated with ischemic brain injury

Umbilical cord blood (UCB) is a rich source of hematopoetic stem cells (HSCs). We have isolated a novel cell line population of stem cells from human UCB that exhibit properties of self-renewal, but do not have cell-surface markers that are typically found on HSCs. Analysis of transcripts revealed that these cells express transcription factors Oct-4, Rex-1, and Sox-2 that are typically expressed by stem cells. We refer to these novel cells as nonhematopoietic umbilical cord blood stem cells (nh-UCBSCs). Previous studies have shown that the intravenous infusion of UCBCs can ameliorate neurological deficits arising from ischemic brain injury. The identity of the cells that mediate this restorative effect, however, has yet to be determined. We postulate that nh-UCBSCs may be a source of the UCB cells that can mediate these effects. To test this hypothesis, we intravenously injected one million human nh-UCBSCs into rats 48 h after transient unilateral middle cerebral artery occlusion. Animals in other experimental groups received either saline injections or injections of RN33b neural stem cells. Animals were tested for neurological function before the infusion of nh-UCBSCs and at various time periods afterwards using a battery of behavioral tests. In limb placement tests, animals treated with nh-UCBSCs exhibited mean scores that were significantly better than animals treated with RN33b neural stem cells or saline. Similarly, in stepping tests, nh-UCBSC-treated animals again exhibited significantly better performance than the other experimental groups of animals. Analysis of infarct volume revealed that ischemic animals treated with nh-UCBSCs exhibited a 50% reduction in lesion volume in comparison to saline-treated controls. Histological analysis of brain tissue further revealed the presence of cells that stained for human nuclei. Some human nuclei-positive cells were also co-labeled for NeuN, indicating that the transplanted cells expressed markers of a neuronal phenotype. Cells expressing the human nuclei marker within the brain, however, were rather scant, suggesting that the restorative effects of nh-UCBSCs may be mediated by mechanisms other than cell replacement. To test this hypothesis, nh-UCBSCs were directly transplanted into the brain parenchyma after ischemic brain injury. Sprouting of nerve fibers from the nondamaged hemisphere into the ischemically damaged side of the brain was assessed by anterograde tracing using biotinylated dextran amine (BDA). Animals with nh-UCBSC transplants exhibited significantly greater densities of BDA-positive cells in the damaged side of the brain compared to animals with intraparenchymal saline injections. These results suggest that restorative effects observed with nh-UCBSC treatment following ischemic brain injury may be mediated by trophic actions that result in the reorganization of host nerve fiber connections within the injured brain.

Stem cells for the ischaemic heart

The discovery of adult progenitor cells capable of generating new vascular and myocardial tissue offers the promise of salvage of ischaemically threatened or irreversibly damaged cardiac tissue. Not surprisingly, great interest has focused on the use of a variety of cell types to treat both acute myocardial infarction and chronic ischaemic heart disease. This review focuses on the treatment of these two categories of disease, the cell types being considered, our understanding of timing and methods of cellular administration, and possible mechanisms of myocardial salvage.

Gene Transfer into Rat Mesenchymal Stem Cells: A Comparative Study of Viral and Nonviral Vectors

Mesenchymal stem cells (MSCs) have been proposed for use in combinatorial gene and cell therapy protocols for the treatment of disease and promotion of repair. The efficacy of such a therapeutic approach depends on determination of which vectors give maximal transgene expression with minimal cell death. The study was carried out on bone-marrow derived rat MSCs, and a range of vectors was tested on the same stem cell preparation. Adenovirus, adeno-associated virus (AAV; serotypes 1, 2, 4, 5, and 6), lentivirus, and nonviral vectors were compared. Lentivirus proved to be most effective with transduction efficiencies of up to 95%, concurrent with low levels of cell toxicity. Adenovirus also proved effective, but a significant increase in cell death was seen with increasing viral titer. Rat MSCs remained refractory to transduction by all AAV serotypes, in contrast to rabbit MSCs tested at the same time. Lipofection of plasmid DNA gave moderate transfection levels but was also accompanied by cell death. Electroporative gene transfer proved ineffective at the parameters tested and resulted in high cell death. High and moderate levels of cell transduction using lentivirus vectors did not affect the ability of the cells to differentiate down the adipogenic pathway.

Stem cells in the umbilical cord

Stem cells are the next frontier in medicine. Stem cells are thought to have great therapeutic and biotechnological potential. This will not only to replace damaged or dysfunctional cells, but also rescue them and/or deliver therapeutic proteins after they have been engineered to do so. Currently, ethical and scientific issues surround both embryonic and fetal stem cells and hinder their widespread implementation. In contrast, stem cells recovered postnatally from the umbilical cord, including the umbilical cord blood cells, amnion/placenta, umbilical cord vein, or umbilical cord matrix cells, are a readily available and inexpensive source of cells that are capable of forming many different cell types (i.e., they are "multipotent"). This review will focus on the umbilical cord-derived stem cells and compare those cells with adult bone marrow-derived mesenchymal stem cells.