Bone marrow stromal cells improve cardiac performance in healed infarcted rat hearts

In Situ Maturated Early-Stage Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes Improve Cardiac Function by Enhancing Segmental Contraction in Infarcted Rats

The scant ability of cardiomyocytes to proliferate makes heart regeneration one of the biggest challenges of science. Current therapies do not contemplate heart re-muscularization. In this scenario, stem cell-based approaches have been proposed to overcome this lack of regeneration. We hypothesize that early-stage hiPSC-derived cardiomyocytes (hiPSC-CMs) could enhance the cardiac function of rats after myocardial infarction (MI). Animals were subjected to the permanent occlusion of the left ventricle (LV) anterior descending coronary artery (LAD). Seven days after MI, early-stage hiPSC-CMs were injected intramyocardially. Rats were subjected to echocardiography pre-and post-treatment. Thirty days after the injections were administered, treated rats displayed 6.2% human cardiac grafts, which were characterized molecularly. Left ventricle ejection fraction (LVEF) was improved by 7.8% in cell-injected rats, while placebo controls showed an 18.2% deterioration. Additionally, cell-treated rats displayed a 92% and 56% increase in radial and circumferential strains, respectively. Human cardiac grafts maturate in situ, preserving proliferation with 10% Ki67 and 3% PHH3 positive nuclei. Grafts were perfused by host vasculature with no evidence for immune rejection nor ectopic tissue formations. Our findings support the use of early-stage hiPSC-CMs as an alternative therapy to treat MI. The next steps of preclinical development include efficacy studies in large animals on the path to clinical-grade regenerative therapy targeting human patients.

Acute Myocardial Infarction Reduces Respiration in Rat Cardiac Fibers, despite Adipose Tissue Mesenchymal Stromal Cell Transplant

Adipose-derived mesenchymal stromal cell (AD-MSC) administration improves cardiac function after acute myocardial infarction (AMI). Although the mechanisms underlying this effect remain to be elucidated, the reversal of the mitochondrial dysfunction may be associated with AMI recovery. Here, we analyzed the alterations in the respiratory capacity of cardiomyocytes in the infarcted zone (IZ) and the border zone (BZ) and evaluated if mitochondrial function improved in cardiomyocytes after AD-MSC transplantation. Female rats were subjected to AMI by permanent left anterior descending coronary (LAD) ligation and were then treated with AD-MSCs or PBS in the border zone (BZ). Cardiac fibers were analyzed 24 hours (necrotic phase) and 8 days (fibrotic phase) after AMI for mitochondrial respiration, citrate synthase (CS) activity, F₀F₁-ATPase activity, and transmission electron microscopy (TEM). High-resolution respirometry of permeabilized cardiac fibers showed that AMI reduced numerous mitochondrial respiration parameters in cardiac tissue, including phosphorylating and nonphosphorylating conditions, respiration coupled to ATP synthesis, and maximal respiratory capacity. CS decreased in IZ and BZ at the necrotic phase, whereas it recovered in BZ and continued to drop in IZ over time when compared to Sham. Exogenous cytochrome c doubled respiration at the necrotic phase in IZ. F₀F₁-ATPase activity decreased in the BZ and, to more extent, in IZ in both phases. Transmission electron microscopy showed disorganized mitochondrial cristae structure, which was more accentuated in IZ but also important in BZ. All these alterations in mitochondrial respiration were still present in the group treated with AD-MSC. In conclusion, AMI led to mitochondrial dysfunction with oxidative phosphorylation disorders, and AD-MSC improved CS temporarily but was not able to avoid alterations in mitochondria function over time.

Short-Term Heart Retention and Distribution of Intramyocardial Delivered Mesenchymal Cells within Necrotic or Intact Myocardium

Cell therapy with bone marrow mesenchymal stem cells (BMSCs) is a new strategy for treating ischemic heart failure, but data concerning the distribution and retention of transplanted cells remain poor. We investigated the short-term myocardial retention of BMSCs when these cells are directly injected within necrotic or intact myocardium. 111Indium-oxine-labeled autologous BMSCs were injected within either 1-month-old infarction (n = 6) or normal myocardium (n = 6) from rats. Serial in vivo pinhole scintigraphy was scheduled during 1 week in order to track the implanted cells. The myocardial retention of BMSCs was definitely higher in myocardial infarction than in normal myocardial area (estimated percent retention at 2 h: 63 ± 3% vs. 25 ± 4%, p < 0.001) and the estimated cardiac retention values were unchanged in both groups along the 7 days of follow-up. On heart sections at day 7, labeled BMSCs were still around the injection site and appeared confined to the scarred tissue corresponding either to the infarct area or to the myocardium damaged by needle insertion. BMSCs have a higher retention when they are injected in necrotic than in normal myocardial areas and these cells appear to stay around the injection site for at least a 7-day period.

Sustained IGF-1 Secretion by Adipose-Derived Stem Cells Improves Infarcted Heart Function

The mechanism by which stem cell-based therapy improves heart function is still unknown, but paracrine mechanisms seem to be involved. Adipose-derived stem cells (ADSCs) secrete several factors, including insulin-like growth factor-1 (IGF-1), which may contribute to myocardial regeneration. Our aim was to investigate whether the overexpression of IGF-1 in ADSCs (IGF-1-ADSCs) improves treatment of chronically infarcted rat hearts. ADSCs were transduced with a lentiviral vector to induce IGF-1 overexpression. IGF-1-ADSCs transcribe100- to 200-fold more IGF-1 mRNA levels compared to nontransduced ADSCs. IGF-1 transduction did not alter ADSC immunophenotypic characteristics even under hypoxic conditions. However, IGF-1-ADSCs proliferate at higher rates and release greater amounts of growth factors such as IGF-1, vascular endothelial growth factor (VEGF), and hepatocyte growth factor (HGF) under normoxic and hypoxic conditions. Importantly, IGF-1 secreted by IGF-1-ADSCs is functional given that Akt-1 phosphorylation was remarkably induced in neonatal cardiomyocytes cocultured with IGF-1-ADSCs, and this increase was prevented with phosphatidylinositol 3-kinase (PI3K) inhibitor treatment. Next, we tested IGF-1-ADSCs in a rat myocardial infarction (MI) model. MI was performed by coronary ligation, and 4 weeks after MI, animals received intramyocardial injections of either ADSCs (n = 7), IGF-1-ADSCs (n = 7), or vehicle (n = 7) into the infarcted border zone. Left ventricular function was evaluated by echocardiography before and after 6 weeks of treatment, and left ventricular hemodynamics were assessed 7 weeks after cell injection. Notably, IGF-1-ADSCs improved left ventricular ejection fraction and cardiac contractility index, but did not reduce scar size when compared to the ADSC-treated group. In summary, transplantation of ADSCs transduced with IGF-1 is a superior therapeutic approach to treat MI compared to nontransduced ADSCs, suggesting that gene and cell therapy may bring additional benefits to the treatment of MI.

Bone marrow mesenchymal stem cell transplantation retards the natural senescence of rat hearts

Bone marrow mesenchymal stem cells (BMSCs) have been shown to offer a wide variety of cellular functions including the protective effects on damaged hearts. Here we investigated the antiaging properties of BMSCs and the underlying mechanism in a cellular model of cardiomyocyte senescence and a rat model of aging hearts. Neonatal rat ventricular cells (NRVCs) and BMSCs were cocultured in the same dish with a semipermeable membrane to separate the two populations. Monocultured NRVCs displayed the senescence-associated phenotypes, characterized by an increase in the number of β-galactosidase-positive cells and decreases in the degradation and disappearance of cellular organelles in a time-dependent manner. The levels of reactive oxygen species and malondialdehyde were elevated, whereas the activities of antioxidant enzymes superoxide dismutase and glutathione peroxidase were decreased, along with upregulation of p53, p21(Cip1/Waf1), and p16(INK4a) in the aging cardiomyocytes. These deleterious alterations were abrogated in aging NRVCs cocultured with BMSCs. Qualitatively, the same senescent phenotypes were consistently observed in aging rat hearts. Notably, BMSC transplantation significantly prevented these detrimental alterations and improved the impaired cardiac function in the aging rats. In summary, BMSCs possess strong antisenescence action on the aging NRVCs and hearts and can improve cardiac function after transplantation in aging rats. The present study, therefore, provides an alternative approach for the treatment of heart failure in the elderly population.

Bone marrow mesenchymal cells improve muscle function in a skeletal muscle re-injury model

Skeletal muscle injury is the most common problem in orthopedic and sports medicine, and severe injury leads to fibrosis and muscle dysfunction. Conventional treatment for successive muscle injury is currently controversial, although new therapies, like cell therapy, seem to be promise. We developed a model of successive injuries in rat to evaluate the therapeutic potential of bone marrow mesenchymal cells (BMMC) injected directly into the injured muscle. Functional and histological assays were performed 14 and 28 days after the injury protocol by isometric tension recording and picrosirius/Hematoxilin & Eosin staining, respectively. We also evaluated the presence and the fate of BMMC on treated muscles; and muscle fiber regeneration. BMMC treatment increased maximal skeletal muscle contraction 14 and 28 days after muscle injury compared to non-treated group (4.5 ± 1.7 vs 2.5 ± 0.98 N/cm2, p<0.05 and 8.4 ± 2.3 vs. 5.7 ± 1.3 N/cm2, p<0.05 respectively). Furthermore, BMMC treatment increased muscle fiber cross-sectional area and the presence of mature muscle fiber 28 days after muscle injury. However, there was no difference in collagen deposition between groups. Immunoassays for cytoskeleton markers of skeletal and smooth muscle cells revealed an apparent integration of the BMMC within the muscle. These data suggest that BMMC transplantation accelerates and improves muscle function recovery in our extensive muscle re-injury model.

Myocardial regeneration of the failing heart

Human heart failure (HF) is one of the leading causes of morbidity and mortality worldwide. Currently, heart transplantation and implantation of mechanical devices represent the only available treatments for advanced HF. Two alternative strategies have emerged to treat patients with HF. One approach relies on transplantation of exogenous stem cells (SCs) of non-cardiac or cardiac origin to induce cardiac regeneration and improve ventricular function. Another complementary strategy relies on stimulation of the endogenous regenerative capacity of uninjured cardiac progenitor cells to rebuild cardiac muscle and restore ventricular function. Various SC types and delivery strategies have been examined in the experimental and clinical settings; however, neither the ideal cell type nor the cell delivery method for cardiac cell therapy has yet emerged. Although the use of bone marrow (BM)-derived cells, most frequently exploited in clinical trials, appears to be safe, the results are controversial. Two recent randomized trials have failed to document any beneficial effects of intracardiac delivery of autologous BM mononuclear cells on cardiac function of patients with HF. The remarkable discovery that various populations of cardiac progenitor cells (CPCs) are present in the adult human heart and that it possesses limited regeneration capacity has opened a new era in cardiac repair. Importantly, unlike BM-derived SCs, autologous CPCs from myocardial biopsies cultured and subsequently delivered by coronary injection to patients have given positive results. Although these data are promising, a better understanding of how to control proliferation and differentiation of CPCs, to enhance their recruitment and survival, is required before CPCs become clinically applicable therapeutics.

Concise review: skeletal muscle stem cells and cardiac lineage: potential for heart repair

Valuable and ample resources have been spent over the last two decades in pursuit of interventional strategies to treat the unmet demand of heart failure patients to restore myocardial structure and function. At present, it is clear that full restoration of myocardial structure and function is outside our reach from both clinical and basic research studies, but it may be achievable with a combination of ongoing research, creativity, and perseverance. Since the 1990s, skeletal myoblasts have been extensively investigated for cardiac cell therapy of congestive heart failure. Whereas the Myoblast Autologous Grafting in Ischemic Cardiomyopathy (MAGIC) trial revealed that transplanted skeletal myoblasts did not integrate into the host myocardium and also did not transdifferentiate into cardiomyocytes despite some beneficial effects on recipient myocardial function, recent studies suggest that skeletal muscle-derived stem cells have the ability to adopt a cardiomyocyte phenotype in vitro and in vivo. This brief review endeavors to summarize the importance of skeletal muscle stem cells and how they can play a key role to surpass current results in the future and enhance the efficacious implementation of regenerative cell therapy for heart failure.

Clinical trials of cardiac repair with adult bone marrow- derived cells

The past decade has witnessed a marked increase in the number of clinical trials of cardiac repair with adult bone marrow cells (BMCs). These trials included patients with acute myocardial infarction (MI) as well as chronic ischemic heart disease (IHD) and utilized different types of BMCs with variable numbers, routes of administration, and timings after MI. Given these differences in methods, the outcomes from these trials have been often disparate and controversial. However, analysis of pooled data suggests that BMC injection enhances left ventricular function, reduces infarct scar size, and improves remodeling in patients with acute MI as well as chronic IHD. BMC therapy also improves clinical outcomes during follow-up without any increase in adverse effects. Although the underlying mechanisms of heart repair are difficult to elucidate in human studies, valuable insights may be gleaned from subgroup analysis of key variables. This information may be utilized to design future randomized controlled trials to carefully determine the long-term safety and benefits of BMC therapy.

The impact of stem cells on electron fluxes, proton translocation, and ATP synthesis in kidney mitochondria after ischemia/reperfusion

Tissue damage by ischemia/reperfusion (I/R) results from a temporary cessation of blood flow followed by the restoration of circulation. The injury depresses mitochondrial respiration, increases the production of reactive oxygen species (ROS), decreases the mitochondrial transmembrane potential, and stimulates invasion by inflammatory cells. The primary objective of this work was to address the potential use of bone marrow stem cells (BMSCs) to preserve and restore mitochondrial function in the kidney after I/R. Mitochondria from renal proximal tubule cells were isolated by differential centrifugation from rat kidneys subjected to I/R (clamping of renal arteries followed by release of circulation after 30 min), without or with subcapsular administration of BMSCs. Respiration starting from mitochondrial complex II was strongly affected following I/R. However, when BMSCs were injected before ischemia or together with reperfusion, normal electron fluxes, electrochemical gradient for protons, and ATP synthesis were almost completely preserved, and mitochondrial ROS formation occurred at a low rate. In homogenates from cultured renal cells transiently treated with antimycin A, the coculture with BMSCs induced a remarkable increase in protein S-nitrosylation that was similar to that found in mitochondria isolated from I/R rats, evidence that BMSCs protected against both superoxide anion and peroxynitrite. Labeled BMSCs migrated to damaged tubules, suggesting that the injury functions as a signal to attract and host the injected BMSCs. Structural correlates of BMSC injection in kidney tissue included stimulus of tubule cell proliferation, inhibition of apoptosis, and decreased inflammatory response. Histopathological analysis demonstrated a score of complete preservation of tubular structures by BMSCs, associated with normal plasma creatinine and urinary osmolality. These key findings shed light on the mechanisms that explain, at the mitochondrial level, how stem cells prevent damage by I/R. The action of BMSCs on mitochondrial functions raises the possibility that autologous BMSCs may help prevent I/R injuries associated with transplantation and acute renal diseases.

Bone marrow-derived cell therapy in chagasic cardiac disease: a review of pre-clinical and clinical results

Chagas disease is caused by a protozoan parasite Trypanosoma cruzi, which infects people through blood sucking insects. It is endemic in Latin America and the disease is being spread to developed countries as a result of the migration of infected individuals. In its chronic stage, Chagas disease can lead to a severe cardiomyopathy for which there is currently no cure. End-stage patients require heart transplantation, thus demanding new therapeutic modalities. Cell-based therapy has been proposed as an alternative for various forms of heart disease. Here we review the experimental evidence that led to the use of bone marrow-derived cells in putative therapy for chronic chagasic cardiomyopathy in animal models and in clinical trials, discussing the reasons for failure of the translation of results from mice to men.

Adipose-derived stem-cell treatment of skeletal muscle injury

BACKGROUND

The aim of the present study was to investigate whether adipose-derived stem cells could contribute to skeletal muscle-healing.

METHODS

Adipose-derived stem cells of male rats were cultured and injected into the soleus muscles of female rats. Two and four weeks after injections, muscles were tested for tetanic force (50 Hz). Histological analysis was performed to evaluate muscle collagen deposition and the number of centronucleated muscle fibers. In order to track donor cells, chimerism was detected with use of real-time polymerase chain reaction targeting the male sex-determining region Y (SRY) gene.

RESULTS

Two weeks after cell injection, tetanus strength and the number of centronucleated regenerating myofibers, as well as the number of centronucleated regenerating myofibers, were higher in the treated group than they were in the control group (mean and standard error of the mean, 79.2 ± 5.0% versus 58.3 ± 8.1%, respectively [p < 0.05]; and 145 ± 36 versus 273 ± 18 per 10³ myofibers, respectively [p < 0.05]). However, there were no significant differences at four weeks. Treatment did not decrease collagen deposition. Male gene was not detected in female host tissue at two and four weeks after engraftment by polymerase chain reaction analysis.

CONCLUSIONS

Adipose-derived stem-cell therapy increased muscle repair and force at two weeks, but not four weeks, after injection, suggesting that adipose-derived stem-cell administration may accelerate muscle repair; however, the rapid disappearance of injected cells suggests a paracrine mechanism of action.

Empowering adult stem cells for myocardial regeneration

Treatment strategies for heart failure remain a high priority for ongoing research due to the profound unmet need in clinical disease coupled with lack of significant translational progress. The underlying issue is the same whether the cause is acute damage, chronic stress from disease, or aging: progressive loss of functional cardiomyocytes and diminished hemodynamic output. To stave off cardiomyocyte losses, a number of strategic approaches have been embraced in recent years involving both molecular and cellular approaches to augment myocardial structure and performance. Resultant excitement surrounding regenerative medicine in the heart has been tempered by realizations that reparative processes in the heart are insufficient to restore damaged myocardium to normal functional capacity and that cellular cardiomyoplasty is hampered by poor survival, proliferation, engraftment, and differentiation of the donated population. To overcome these limitations, a combination of molecular and cellular approaches must be adopted involving use of genetic engineering to enhance resistance to cell death and increase regenerative capacity. This review highlights biological properties of approached to potentiate stem cell-mediated regeneration to promote enhanced myocardial regeneration, persistence of donated cells, and long-lasting tissue repair. Optimizing cell delivery and harnessing the power of survival signaling cascades for ex vivo genetic modification of stem cells before reintroduction into the patient will be critical to enhance the efficacy of cellular cardiomyoplasty. Once this goal is achieved, then cell-based therapy has great promise for treatment of heart failure to combat the loss of cardiac structure and function associated with acute damage, chronic disease, or aging.

Soluble factors from multipotent mesenchymal stromal cells have antinecrotic effect on cardiomyocytes in vitro and improve cardiac function in infarcted rat hearts

The mechanisms underlying the functional improvement after injection of multipotent mesenchymal stromal cells (MSCs) in infarcted hearts remain incompletely understood. The aim of this study was to investigate if soluble factors secreted by MSCs promote cardioprotection. For this purpose, conditioned medium (CM) was obtained after three passages from MSC cultures submitted to 72 h of conditioning in serum-free DMEM under normoxia (NCM) or hypoxia (HCM) conditions. CM was concentrated 25-fold before use (NCM-25X, concentrated normoxia conditioned medium; HCM-25X, concentrated hypoxia conditioned medium). The in vitro cardioprotection was evaluated in neonatal ventricular cardiomyocytes by quantifying apoptosis after 24 h of serum deprivation associated with hypoxia (1% O(2)) in the absence or presence of NCM and HCM (nonconcentrated and 25-fold concentrated). The in vivo cardioprotection of HCM was tested in a model of myocardial infarction (MI) induced in Wistar male rats by permanent left coronary occlusion. Intramyocardial injection of HCM-25X (n = 14) or nonconditioned DMEM (n = 16) was performed 3 h after coronary occlusion and cardiac function was evaluated 19-21 days after medium injection. Cardiac function was evaluated by electro- and echocardiogram, left ventricular catheterization, and treadmill test. The in vitro results showed that HCM was able to decrease cardiomyocyte necrosis. The in vivo results showed that HCM-25X administered 3 h after AMI was able to promote a significant reduction (35%) in left ventricular end-diastolic pressure and improvement of cardiac contractility (15%) and relaxation (12%). These results suggest that soluble factors released in vitro by MSCs are able to promote cardioprotection in vitro and improve cardiac function in vivo.

Adipose-derived stromal cell therapy improves cardiac function after coronary occlusion in rats

Recent studies have identified adipose tissue as a new source of mesenchymal stem cells for therapy. The purpose of this study was to investigate the therapy with adipose-derived stromal cells (ASCs) in a rat model of healed myocardial infarction (MI). ASCs from inguinal subcutaneous adipose tissue of male Wistar rats were isolated by enzymatic digestion and filtration. Cells were then cultured until passage 3. Four weeks after ligation of the left coronary artery of female rats, a suspension of either 100 µl with phosphate-buffered saline (PBS) + Matrigel + 2 × 10(6) ASCs labeled with Hoechst (n = 11) or 100 µl of PBS + Matrigel (n = 10) was injected along the borders of the ventricular wall scar tissue. A sham-operated group (n = 5) was submitted to the same surgical procedure except permanent ligation of left coronary artery. Cardiac performance was assessed by electro- and echocardiogram. Echo was performed prior to injections (baseline, BL) and 6 weeks after injections (follow-up, FU), and values after treatment were normalized by values obtained before treatment. Hemodynamic measurements were performed 6 weeks after injections. All infarcted animals exhibited cardiac function impairment. Ejection fraction (EF), shortening fractional area (SFA), and left ventricular akinesia (LVA) were similar between infarcted groups before treatment. Six weeks after therapy, ASC group showed significant improvement in all three ECHO indices in comparison to vehicle group. In anesthetized animals dp/dt(+) was also significantly higher in ASCs when compared to vehicle. In agreement with functional improvement, scar area was diminished in the ASC group. We conclude that ASCs improve cardiac function in infarcted rats when administered directly to the myocardium.

Therapeutic angiogenesis for myocardial ischemia revisited: basic biological concepts and focus on latest clinical trials

Therapeutic angiogenesis is based on the premise that the development of new blood vessels can be augmented by exogenous administration of the appropriate growth factors. Over the last years, successful preclinical studies and promising results of early clinical trials have created great excitement about the potential of therapeutic angiogenesis for patients with advanced ischemic heart disease. The authors provide an overview of the biology of angiogenesis, the basic characteristics of angiogenic factors, and the different routes of their delivery. They discuss experimental studies in animal models of myocardial ischemia and outline available clinical studies on therapeutic angiogenesis for myocardial ischemia. Related safety issues are also addressed followed by a critical perspective about the future of proangiogenic therapies for ischemic cardiovascular disorders. Despite the established proof of concept and reasonable safety, however, results of the latest trials on therapeutic angiogenesis for myocardial ischemia have provided inconsistent results and the definite means of inducing clinically useful therapeutic angiogenesis remain elusive. More studies are required to gain further insights into the biology of angiogenesis and address pharmacological limitations of current approaches of angiogenic therapy. The authors hope and envisage that in the not-too-distant future, these investigative efforts will lead to important new strategies for treatment of myocardial ischemic syndromes. Means of non-invasive individualized pharmacological therapeutic neovascularization may be the next major advance in the treatment of ischaemic heart disease.

Paracrine interaction between bone marrow-derived stem cells and renal epithelial cells

BACKGROUND/AIMS

Renal tubular cells are the main target of ischemic insult associated with acute renal injury. Low oxygen and nutrient supplies result in ATP depletion, leading to cell death and loss of renal function. A possible mechanism by which bone marrow-derived cells support renal tissue regeneration relies on the capacity of mononuclear cells (BMMC), particularly mesenchymal stem cells (MSC), to secrete paracrine factors that mediate support for kidney regeneration.

METHODS

BMMC/MSC and renal cells (LLC-PK(1) from pig and IRPTC from rat) were co-cultured under stressful conditions (ATP depletion and/or serum free starvation), physically separated by a microporous membrane (0.4 μm), was used to determine whether bone marrow-derived cells can interact with renal cells in a paracrine manner.

RESULTS

This interaction resulted in stimulation of renal cell proliferation and the arrest of cell death. MSC elicit effective responses in renal cells in terms of stimulating proliferation and protection. Such effects are observed in renal cells co-cultured with rat BMMC/MSC, an indication that paracrine mechanisms are not entirely species-specific.

CONCLUSION

The paracrine action of BMMC/MSC was influenced by a renal cell stimulus released during stress, indicating that cross-talk with injured cells is required for renal regeneration supported by bone marrow-derived cells.

Cell-based therapy in Chagas disease

Chagas disease was first described one century ago, yet the mechanisms underlying chagasic cardiomyopathy remain elusive. Disease progression often leads to heart failure and patients with this infectious cardiomyopathy have a poor prognosis. Treatment options for heart failure due to Chagas disease are not different from standard therapy. Over the past decade, cell-based therapies have emerged as a new alternative in the treatment of this disease, not only because of the possibility of replacing lost vessels and cardiomyocytes but also because these cells could potentially influence the microenvironmental changes that perpetuate the disease. In this chapter, we will review current knowledge on cell-based therapies for the treatment of Chagas disease.

Granulocyte-colony stimulating factor treatment of chronic myocardial infarction

PURPOSE

The aim of this study was to investigate the impact of granulocyte-colony stimulating factor (G-CSF) administration on cardiac function of rats with chronic myocardial infarction through two different protocols: high dose short term and low dose long term protocols.

METHODS

Wistar rats were submitted to MI surgery and after 4 weeks they received recombinant human G-CSF (Filgrastim) or vehicle subcutaneously. We tested the classical protocol (50 microg/kg/day during 7 days) and the long term low dose treatment (four cycles of 5 days of 10 microg/kg/day). Cardiac performance was evaluated before, 4 and 6 weeks after G-CSF injections by electro- and echocardiography, hemodynamic and treadmill exercise test.

RESULTS

All infarcted groups exhibited impaired function compared to sham operated animals. Moreover, all cardiac functional parameter were not different between G-CSF and Vehicle group at resting conditions as well as after treadmill exercise stress test, despite intense white blood cell mobilization in both protocols at all time points. Hypertrophy was not different and infarct size was similar in histological analysis

CONCLUSIONS

These data clearly show that G-CSF treatment was unable to restore cardiac function impaired by myocardial infarction either with classical approach or long term low dose administration.

Pushing the envelope in biomaterial research: initial results of prosthetic coating with stem cells in a rat model

BACKGROUND

Coating prosthetic for hernia repair with a patient's own cells could improve biocompatibility by decreasing inflammation and adhesion formation and by increasing tissue ingrowth and resistance to infection. The objective of this study was to prove the feasibility of prosthetic coating with stem cells and to assess its resistance to adhesion formation when implanted in an animal model.

METHODS

Adult Lewis rat bone marrow stem cells were harvested and cultured. Stem cells were then implanted on three different prosthetics. The prosthetic with the best stem cell adherence was implanted intraperitoneally into six adult rats. Untreated prosthetic was implanted in control animals (n = 12). After 2 weeks, intra-abdominal adhesions were graded using an adhesion scoring scale by two surgeons who were blinded to the animal group. Data were analyzed using the Wilcoxon rank-sum test.

RESULTS

Stem cells demonstrated the best adherence and growth on polyglactin prosthetics. After implantation, the stem cell-coated polyglactin prosthetic had <25% of its surface area covered with adhesions in five (83%) samples, whereas the control polyglactin group had only one sample (8.3%) with <25% adhesions, and seven of its samples (58.3%) had >50% surface area adhesions (p < 0.05).

CONCLUSIONS

The feasibility of hernia prosthetic coating with stem cells was demonstrated. Furthermore, stem-cell coated polyglactin prosthetic exhibited improved biocompatibility by decreasing adhesion formation in an animal model. Further study is needed to determine the factors that promote stem cell adherence to prosthetics and the in vivo prosthetic biomechanics after stem cell coating. This work is underway in our laboratory.

Differential effect of myocardial matrix and integrins on cardiac differentiation of human mesenchymal stem cells

Dysregulation of matrix synthesis during myocardial fibrosis in post-infarct ventricular remodeling contributes to ventricular dysfunction. Bone marrow stem cell transplantation prevents functional deterioration following myocardial infarction. However, effect of myocardial extracellular matrix (ECM) on stem cell differentiation is poorly understood. We investigate the role of collagen matrices and integrin system in cardiac differentiation and engraftment of stem cells in infarcted myocardium. Sternum-derived bone marrow mesenchymal stem cells (MSCs) were differentiated into cardiomyocyte-like cells (CLCs). They were characterized using RT-PCR, immunofluorescence, flow cytometry and functional integrin neutralization assays. CLCs were injected into peri-infarct borders of injured myocardium of Wistar rats one week following left anterior descending (LAD) artery ligation. Cardiac function was analyzed via pressure-volume relationships. Cardiac differentiated CLCs displayed collagen V specificity, which was absent in undifferentiated MSCs. Collagen V, but not collagen I matrix, promoted attachment, proliferation and cardiac differentiation of CLCs. In contrast to beta(1), alpha(v) integrin contributed minimally in the attachment of CLCs on collagen matrices. However, inhibition of alpha(v)beta(3,) but not alpha(2)beta(1) integrin, selectively attenuated troponin T, sarcomeric alpha-actin and ryanodine 2 receptor gene expression in CLCs. Both MSC and CLC transplantation prevented chamber dilatation and improved contractile function. However, systolic activity in MSC transplanted animals was accompanied by heightened wall stress as demonstrated by elevated myocardial end-diastolic pressure and prolonged tissue relaxation time. Localization of CLCs in the vicinity of collagen V-expressing myofibers promoted their integration into cardiac syncytium. CLCs may facilitate hemodynamic recovery by preserving tissue elasticity in the peri-infarct borders that sustains contractile efficiency for functional recovery in an actively remodeling infarcted myocardium.

Connexin43 promotes survival of mesenchymal stem cells in ischaemic heart

The involvement of connexins in regulating cell growth and death has recently been reported. We have investigated whether Cx43 (connexin43) contributes to MSC (mesenchymal stem cell) survival and improves therapeutic efficacy in MI (myocardial infarction). Genetically modified Cx43 MSCs were exposed to hypoxic conditions or injected intramyocardially into a rat MI model. MSCs overexpressing Cx43, with more Bcl-2 and phosphorylated Akt, but less Bax, were relatively tolerant to hypoxic injury. After transplantation, this Cx43 overexpression enhanced cell survival and reduced infarct size, improving contractile performance. Cx43 inhibition by SiRNA reversed the effects of Cx43 overexpression. Therefore, Cx43 may act as a potential target for improving the therapeutic efficacy of MSCs in ischaemic heart disease.

Human umbilical cord blood cells in infarcted rats

Therapy with bone marrow-derived cells has been used in ischemic patients with reported success. The aim of this study was to determine the therapeutic efficacy of fresh and frozen human umbilical cord blood cells (hUCB) in Wistar rats submitted to permanent occlusion of the left coronary artery. Three hours after myocardial infarction, 2 x 10(7) hUCB cells or vehicle were administered by intramyocardial injection. The animals were divided into five groups: control (N = 10), sham operated (N = 10), infarcted that received vehicle (N = 9), infarcted treated with cryopreserved hUCB (N = 7), and infarcted treated with fresh hUCB (N = 5). Cardiac function was evaluated by electrocardiogram (ECG) and echocardiogram (ECHO) before cell therapy, and by ECG, ECHO, cardiopulmonary test, and left ventricular pressure measurements 3 weeks later. After 3 weeks, both groups treated with hUCB still had Q wave present in L1, âQRS >90 degrees and reduced shortening fraction (less than 50%). In addition, cardiac indexes of left ventricular contractility and relaxation were 5484 +/- 875 and -4032 +/- 643 mmHg (cryopreserved hUCB) and 4585 +/- 955 and -2862 +/- 590 mmHg (fresh hUCB), respectively. These values were not statistically different from those of saline-treated animals. Cardiopulmonary exercise test profile was typical of infarcted hearts; exercise time was about 14 min and maximal VO2 was 24.77 +/- 5.00 mL.kg-1.min-1. These data show that hUCB therapy did not improve the cardiac function of infarcted animals or prevent cardiac remodeling.

Mesenchymal stem cell therapy for cardiac repair

Stem cell therapy for repair of damaged cardiac tissue is an attractive option to improve the health of the growing number of heart failure patients. Mesenchymal stem cells (MSCs) possess unique properties that may make them a better option for cardiac repair than other cell types. Unlike other adult stem cells, they appear to escape allorecognition by the immune system and they have immune-modulating properties, thus making it possible to consider them for use as an allogeneic cell therapy product. There is a large and growing body of preclinical and early clinical experience with MSC therapy that shows great promise in realizing the potential of stem cell therapy to effect repair of damaged cardiac tissue. This review discusses the mechanism of action of MSC therapy and summarizes the current literature in the field.

Mesenchymal Stem Cell Therapy for Nonmusculoskeletal Diseases: Emerging Applications

Mesenchymal stem cells are stem/progenitor cells originated from the mesoderm and can different into multiple cell types of the musculoskeletal system. The vast differentiation potential and the relative ease for culture expansion have established mesenchymal stem cells as the building blocks in cell therapy and tissue engineering applications for a variety of musculoskeletal diseases, including repair of fractures and bone defects, cartilage regeneration, treatment of osteonecrosis of the femoral head, and correction of genetic diseases such as osteogenesis imperfect. However, research in the past decade has revealed differentiation potentials of mesenchymal stem cells beyond lineages of the mesoderm, suggesting broader applications than originally perceived. In this article, we review the recent developments in mesenchymal stem cell research with respect to their emerging properties and applications in nonmusculoskeletal diseases.

Cardiac repair with adult bone marrow-derived cells: the clinical evidence

On the basis of strong evidence from animal studies, numerous clinical trials of cardiac repair with adult bone marrow-derived cells (BMC) have been completed. These relatively smaller studies employed different BMC types with highly variable numbers, routes, and timings of transplantation, and included patients with acute myocardial infarction (MI), chronic ischemic heart disease (IHD), as well as ischemic cardiomyopathy. Although the outcomes have been predictably disparate, analysis of pooled data indicates that BMC therapy in patients with acute MI and chronic IHD results in modest improvements in left ventricular function and infarct scar size without any increase in untoward effects. However, the precise mechanisms underlying these benefits remain to be ascertained, and the specific advantages of one BMC type over another remain to be determined. The long-term benefit and safety issues with different BMC types are currently being evaluated critically in larger randomized controlled trials with a view to applying this novel therapeutic strategy to broader patient populations. The purpose of this review is to summarize the available clinical evidence regarding the efficacy and safety of therapeutic cardiac repair with different types of adult BMCs, and to discuss the key variables that need optimization to further enhance the benefits of BMC therapy.

The antiapoptotic effect of mesenchymal stem cell transplantation on ischemic myocardium is enhanced by anoxic preconditioning

BACKGROUND

Cardiomyocyte apoptosis takes place at an early stage after myocardial infarction (MI). Therapy with mesenchymal stem cells (MSCs) is reported to reduce apoptosis.

OBJECTIVES

To determine whether anoxic preconditioning (AP) could enhance the antiapoptotic effect of MSCs.

METHODS

Cultured cardiomyocytes were treated with Dulbecco's modified Eagle's medium (as a control), MSCs or AP-MSCs, and were exposed to hypoxia/reoxygenation. Apoptotic cardiomyocytes were stained with Annexin V fluorescein isothiocyanate (BioVision, USA), visualized by fluorescence microscopy and analyzed by flow cytometry. In vivo, MI was produced in Sprague-Dawley rats by permanent ligation of the left anterior descending coronary artery and the left ventricles were randomly injected with Dulbecco's modified Eagle's medium, MSCs or AP-MSCs one week after MI. The cardiomyocyte apoptotic rate in peri-infarcted areas was assessed by terminal deoxynucleotidyltransferase- mediated 2'-deoxyuridine 5'-triphosphate nick end labelling assay one week after transplantation. Cardiac function was assessed by echocardiography four weeks after transplantation. Infarct size was measured by hematoxylin and eosin staining one and four weeks after transplantation. The expression of Bcl-2, Bax protein and cleaved cysteine-aspartic acid protease-3 was ana-lyzed by Western blot techniques.

RESULTS

Cardiomyocyte apoptosis (both induced by hypoxia/ reoxygenation and MI) was significantly reduced by treating with MSCs and AP-MSCs, the Bcl-2 to Bax protein ratio was increased and cleaved cysteine-aspartic acid protease-3 was decreased. AP-MSCs were superior to MSCs.

CONCLUSIONS

MSCs protected the infarcted heart by preventing cardio-myocyte apoptosis and AP enhanced the cardioprotective effects of MSCs.

Cell therapy attenuates cardiac dysfunction post myocardial infarction: effect of timing, routes of injection and a fibrin scaffold

Background

Cell therapy approaches for biologic cardiac repair hold great promises, although basic fundamental issues remain poorly understood. In the present study we examined the effects of timing and routes of administration of bone marrow cells (BMC) post-myocardial infarction (MI) and the efficacy of an injectable biopolymer scaffold to improve cardiac cell retention and function.

Methodology/Principal Findings

^99mTc-labeled BMC (6×10⁶ cells) were injected by 4 different routes in adult rats: intravenous (IV), left ventricular cavity (LV), left ventricular cavity with temporal aorta occlusion (LV⁺) to mimic coronary injection, and intramyocardial (IM). The injections were performed 1, 2, 3, or 7 days post-MI and cell retention was estimated by γ-emission counting of the organs excised 24 hs after cell injection. IM injection improved cell retention and attenuated cardiac dysfunction, whereas IV, LV or LV* routes were somewhat inefficient (<1%). Cardiac BMC retention was not influenced by timing except for the IM injection that showed greater cell retention at 7 (16%) vs. 1, 2 or 3 (average of 7%) days post-MI. Cardiac cell retention was further improved by an injectable fibrin scaffold at day 3 post-MI (17 vs. 7%), even though morphometric and function parameters evaluated 4 weeks later displayed similar improvements.

Conclusions/Significance

These results show that cells injected post-MI display comparable tissue distribution profile regardless of the route of injection and that there is no time effect for cardiac cell accumulation for injections performed 1 to 3 days post-MI. As expected the IM injection is the most efficient for cardiac cell retention, it can be further improved by co-injection with a fibrin scaffold and it significantly attenuates cardiac dysfunction evaluated 4 weeks post myocardial infarction. These pharmacokinetic data obtained under similar experimental conditions are essential for further development of these novel approaches.

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Chagas disease which is caused by the parasite Trypanosoma cruzi is an important cause of cardiomyopathy in Latin America. In later stages chagasic cardiomyopathy is associated with congestive heart failure which is often refractory to medical therapy. In these individuals heart transplantation has been attempted. However, this procedure is fraught with many problems attributable to the surgery and the postsurgical administration of immunosuppressive drugs. Studies in mice suggest that the transplantation of bone-marrow-derived cells ameliorates the inflammation and fibrosis in the heart associated with this infection. Cardiac magnetic resonance imaging reveals that bone marrow transplantation ameliorates the infection induced right ventricular enlargement. On the basis of these animal studies the safety of autologous bone marrow transplantation has been assessed in patients with chagasic end-stage heart disease. The initial results are encouraging and more studies need to be performed.

Transdifferentiation of stem cells: a critical view

Recently a large amount of new data on the plasticity of stem cells of various lineages have emerged, providing new perspectives especially for the therapeutic application of adult stem cells. Previously unknown possibilities of cell differentiation beyond the known commitment of a given stem cell have been described using keywords such as "blood to liver," or "bone to brain." Controversies on the likelihood, as well as the biological significance, of these conversions almost immediately arose within this young field of stem cell biology. This chapter will concentrate on these controversies and focus on selected examples demonstrating the technical aspects of stem cell transdifferentiation and the evaluation of the tools used to analyze these events.

Comparative study of mesenchymal stem cells from C57BL/10 and mdx mice

Background

Human mesenchymal stem cells (MSCs) have been studied and applied extensively because of their ability to self-renew and differentiate into various cell types. Since most human diseases models are murine, mouse MSCs should have been studied in detail. The mdx mouse – a Duchenne muscular dystrophy model – was produced by introducing a point mutation in the dystrophin gene. To understand the role of dystrophin in MSCs, we compared MSCs from mdx and C57BL/10 mice, focusing particularly on the aspects of light and electron microscopic morphology, immunophenotyping, and differentiation potential.

Results

Our study showed that at passage 10, mdx-MSCs exhibited increased heterochromatin, larger vacuoles, and more lysosomes under electron microscopy compared to C57BL/10-MSCs. C57BL/10-MSCs formed a few myotubes, while mdx-MSCs did not at the same passages. By passage 21, mdx-MSCs but not C57BL/10-MSCs had gradually lost their proliferative ability. In addition, a significant difference in the expression of CD34, not Sca-1 and CD11b, was observed between the MSCs from the 2 mice.

Conclusion

Our current study reveals that the MSCs from the 2 mice, namely, C57BL/10 and mdx, exhibit differences in proliferative and myogenic abilities. The results suggest that the changes in mouse MSC behavior may be influenced by lack of dystrophin protein in mdx mouse.

Time course of echocardiographic and electrocardiographic parameters in myocardial infarct in rats

In animal models the evaluation of myocardial infarct size in vivo and its relation to the actual lesion found post mortem is still a challenge. The purpose of the current study was to address if the conventional electrocardiogram (ECG) and/or echocardiogram (ECHO) could be used to adequately predict the size of the infarct in rats. Wistar rats were infarcted by left coronary ligation and then ECG, ECHO and histopathology were performed at 1, 7 and 28 days after surgery. Correlation between infarct size by histology and Q wave amplitude in lead L1 was only found when ECGs were performed one day post-surgery. Left ventricular diastolic and systolic dimensions correlated with infarct size by ECHO on day 7 post-infarction. On days 7 and 28 post-infarction, ejection indexes estimated by M-mode also correlated with infarct size. In summary we show that conventional ECG and ECHO methods can be used to estimate infarct size in rats. Our data suggest that the 7-day interval is actually the most accurate for estimation of infarct size by ECHO.

Thyroid function disturbance and type 3 iodothyronine deiodinase induction after myocardial infarction in rats a time course study

In humans, there is a significant decrease in serum T(3) and increase in rT(3) at different time points after myocardial infarction, whereas serum TSH and T(4) remain unaltered. We report here a time course study of pituitary-thyroid function and thyroid hormone metabolism in rats subjected to myocardial infarction by left coronary ligation (INF). INF- and sham-operated animals were followed by serial deiodination assays and thyroid function tests, just before, and 1, 4, 8, and 12 wk after surgery. At 4 and 12 wk after INF, liver type 1 deiodinase activity was significantly lower, confirming tissue hypothyroidism. Type 3 deiodinase (D3) activity was robustly induced 1 wk after INF only in the infarcted myocardium. Reminiscent of the consumptive hypothyroidism observed in patients with large D3-expressing tumors, this induction of cardiac D3 activity was associated with a decrease in both serum T(4) ( approximately 50% decrease) and T(3) (37% decrease), despite compensatory stimulation of the thyroid. Thyroid stimulation was documented by both hyperthyrotropinemia and radioiodine uptake. Serum TSH increased by 4.3-fold in the first and 3.1-fold in the fourth weeks (P < 0.01), returning to the basal levels thereafter. Thyroid sodium/iodide-symporter function increased 1 wk after INF, accompanying the increased serum TSH. We conclude that the acute decrease in serum T(4) and T(3) after INF is due to increased thyroid hormone catabolism from ectopic D3 expression in the heart.

Therapeutic myocardial angiogenesis

Armed with an improved understanding of the mediators of angiogenesis, physicians and scientists have made significant efforts at harnessing this naturally occurring process in order to treat patients with a variety of peripheral vascular and coronary ischemic syndromes. There is a growing population of patients with end-stage coronary artery disease (CAD) who are no longer candidates for mechanical revascularization, yet suffer from chronic myocardial ischemia who may benefit from regeneration of the depleted microvasculature.

Role of renin-angiotensin system in development of heart failure induced by myocardial infarction in rats

We investigated the morphologic and functional changes of infarcted rat hearts under a paradigm of angiotensinconverting enzyme inhibition. Myocardial infarction was induced by left coronary artery ligation and a control group (SHAM) underwent sham-operation. Infarcted rats received normal drinking water with (CAP group) or without (INF group) captopril. Functional assessment was performed by electro (ECG) and echocardiogram (ECHO) just before and 21 days after surgery. The ECG of INF and CAP showed similar values and resembled healed infarct after surgery. The most outstanding differences between INF and CAP were the prevention of the increase of P-wave and attenuation both in rightward deviation of the QRS axis and Q-wave amplitude in CAP compared with INF. The ECHO showed that captopril treatment improved the diastolic filling more than systolic performance. Cardiac dilatation and left congestive heart failure were observed only in INF. Both infarcted groups showed a scar tissue in the left ventricular wall, but the INF showed a higher scar area than CAP (49.7 ± 5.24 vs. 22.33 ± 6.19 respectively). These data suggest that the renin-angiotensin system induces morphologic and functional changes in post-infarcted rat hearts and which can be assessed by non-invasive exams.

Cellular therapy in Chagas' disease: potential applications in patients with chronic cardiomyopathy

Nearly a century after its discovery, Chagas' disease, caused by the protozoan Trypanosoma cruzi, remains a major health problem in Latin America. Although efforts in transmission control have contributed to a decrease in the number of new cases, approximately a third of chronic Chagasic individuals have or will develop the symptomatic forms of the disease, mainly cardiomyopathy. Chagas' disease is a progressively debilitating disease, which, at the final stages, there are no currently available treatments other than heart transplantation. In this scenario, cellular therapy is being tested as an alternative for millions of patients with heart dysfunction due to Chagas' disease. In this article, we review the studies of cellular therapy in animal models and in patients with Chagasic cardiomyopathy and the possible mechanisms by which cellular therapy may act in this disease.

Mechanisms of action of mesenchymal stem cells in cardiac repair: potential influences on the cardiac stem cell niche

Clinical and basic studies of cell-based myocardial therapy have proceeded at a rapid pace. Cell therapy could lead to successful cardiac regeneration or repair by any of three general mechanisms: differentiation of the administered cells into all of the cellular constituents of the heart; release of factors capable of paracrine signaling from the administered cells; and fusion of the administered cells with the existing constituents of the heart. Here, we argue that a fourth general mechanism could be operative: stimulation of endogenous repair by injected cells, which and might cause the regeneration of stem cell niches. In a porcine model of myocardial infarction, allogeneic mesenchymal stem cells stimulated substantial improvement in the ejection fraction, reduction of infarct size, and the growth of a rim of new cardiac tissue in the region in which the mesenchymal stem cells were injected. These effects occurred in the absence of definitive cardiac myocyte differentiation. After myocardial infarction, porcine hearts exhibit evidence of cardiac myocytes that have entered the cell cycle, neovascularization, and reduced levels of apoptosis. These data, in addition to new insights regarding the presence of endogenous cardiac stem cells, strongly support the concept that the heart could contain stem cell niches. Effective cell therapy could lead to restoration of these niches through multifaceted cell-cell interactions.

Cellular cardiomyoplasty in large myocardial infarction: can the beneficial effect be enhanced by ACE-inhibitor therapy?

BACKGROUND

Cellular cardiomyoplasty with bone marrow derived stromal (MSC) and mononuclear (BMNC) cells has been shown to improve performance of infarcted hearts. We performed a comparative study with MSC and BMNC and tested the hypothesis that captopril treatment could enhance the beneficial effect of cell therapy in large myocardial infarctions.

METHODS

Male syngeneic Wistar rats underwent experimental infarction and were randomized to receive 1-3 x 10(6) MSC, 10(8) BMNC or vehicle (BSS group). Two additional groups were treated with captopril and received 1-3 x 10(6) MSC (Cap.MSC) or vehicle (Cap).

RESULTS

The ejection fraction (EF%) of MSC and BMNC-treated rats was higher than in the BSS rats, eight weeks after transplantation (33.0+/-4.0, 34.0+/-2.0 and 20.0+/-2.0% respectively, P<0.01). Both captopril-treated groups improved EF% similarly. But only captopril plus MSC treatment almost restored cardiac function to control levels, 8 weeks after injection (60.50+/-5.40% vs. 41.00+/-4.50% in Cap.MSC and Cap respectively, P<0.05). Many DAPI-labelled cells were found in the scar tissue of the left ventricle only in the Cap.MSC group.

CONCLUSIONS

Cell transplantation with both MSC and BMNC produced a similar stabilisation of heart function, but the success of the cell engraftment and the recovery of cardiac performance were dependent on concomitant treatment with captopril.

Transplantation of embryonic stem cell-derived cardiomyocytes improves cardiac function in infarcted rat hearts

BACKGROUND

Post-infarct congestive heart failure is one of the leading causes of morbidity and mortality in industrialized countries. The main purpose of this study was to investigate whether transplantation of embryonic stem cell-derived cardiomyocytes (ESCM) directly into the infarcted myocardium could improve cardiac function in rats.

METHODS

Cell culture medium with or without ESCM was injected into the borders of cardiac scar tissue 1 week after experimental infarction. Cardiac performance was evaluated 4 weeks later by means of echocardiography after ESCM (n=16) or medium (n=12) injection.

RESULTS

ESCM implantation significantly improved fractional shortening (31.5+/-3. 8%) compared with medium-treated hearts (21.3+/-5.2%; P<0.05) and preserved left ventricular structure. Co-localization of 4',6-diamidino-2-phenylindole-labeled nuclei of transplanted cells with cardiomyocyte markers for cardiac troponin T and connexin-43, as detected by immunofluorescent microscopy, indicated the regeneration of damaged myocardium and the formation of gap junctions between grafted and host cells. However, intra-myocardial teratomas were observed in the hearts of two of the 16 grafted animals, at the fourth week after ESCM transplantation.

DISCUSSION

Our results suggest that, although ESCM implantation can improve the function of infarcted myocardium, strategies to prevent tumorigenesis should be developed.

G-CSF does not improve systolic function in a rat model of acute myocardial infarction

OBJECTIVE

Granulocyte colony-stimulating factor (G-CSF) has been reported to improve cardiac performance by increasing the number of bone marrow stem cell in the peripheral circulation. The aim of this study was to investigate the impact of G-CSF administration on cardiac function in a rat model of acute myocardial infarction.

METHODS

Recombinant human G-CSF (Filgrastim, 100 microg/kg, sc) twice a day during seven consecutive days (G-CSF group, n=13) or vehicle (control group, n=10) was administrated three hours after left anterior coronary artery ligation. Cardiac performance was evaluated 19-21 days after myocardial infarction by electro- and echocardiography, hemodynamic and treadmill exercise test.

RESULTS

Both infarcted groups exhibit impaired cardiac function compared to sham-operated rats. Moreover, all cardiac functional parameters were not statistically different between G-CSF and infarcted group at resting conditions as well as after treadmill exercise stress test. There was no sign of cardiac regeneration and infarct size was not different on histological analysis between groups.

CONCLUSIONS

These data clearly shows that G-CSF treatment was unable to prevent cardiac remodeling or to improve cardiovascular function in a rat model of acute myocardial infarction, by permanent LAD ligation, despite bone marrow stem cell mobilization.

Human umbilical cord derived stem cells for the injured heart

The limited ability of the heart to regenerate damaged tissue following a myocardial infarct results in progressive dysfunctions and consequently leads to heart failure. Cell therapy with stem cells for cardiac repair is emerging as an alternative strategy and demonstrates promising results. Recent advances suggest human umbilical cord may be a new source for stem cells. Human umbilical cords are easy to obtain and umbilical cord derived stem cells can be easily extracted and cryopreserved, allowing for individuals to store their own samples for possible future autologous use even if there were no immediate indication that stem cell therapy would be required. Therefore, we hypothesize that human umbilical cord derived stem cells may be the new cell source for the injured heart.

Feasibility of in vivo dual-energy myocardial SPECT for monitoring the distribution of transplanted cells in relation to the infarction site

PURPOSE

Cell therapy using bone marrow mesenchymal stem cells (BMSCs) shows promise in the treatment of myocardial infarction (MI) but accurate cell delivery within MI areas remains critical. In the present study, we tested the feasibility of in vivo pinhole SPECT imaging for monitoring the sites of intramyocardial implanted BMSCs in relation to targeted MI areas in rats.

METHODS

BMSCs were labelled with (111)In-oxine and injected within the fibrotic areas of 3-month-old MI in ten rats. Two days later, dual (111)In/(99m)Tc-sestamibi pinhole SPECT was recorded for localisation of (111)In-BMSCs on a 15-segment left ventricular (LV) division. Additional (99m)Tc-sestamibi pinhole SPECT had been performed 1 month earlier and on the day before transplantation. In vitro counting on histological sections was used to validate the pinhole SPECT determination of (111)In-BMSC activity within LV segments.

RESULTS

The underperfused MI area (segments with <70% uptake) was stable between the (99m)Tc-sestamibi SPECT study recorded at 1 month (4.6+/-1.9 segments) and at 1 day (4.7+/-2.3 segments) before transplantation. (111)In-BMSCs were detected by dual-energy SPECT in 56 segments: 33 (59%) were underperfused MI segments but 23 (41%) were not (14 adjacent and nine remote segments). Finally, (111)In-labelled BMSCs were not detected in 14 out of the 47 (30%) underperfused MI segments.

CONCLUSION

When BMSCs are injected within MI areas in rats, sites of early cell retention do not always match the targeted MI areas. The dual-energy pinhole SPECT technique may be used for monitoring the sites of early retention of implanted BMSCs and the data obtained may have critical importance when analysing the effects of cardiac cell therapy.

Ectopic ossification in the scar tissue of rats with myocardial infarction

We describe the occurrence of bone-like formations in the left ventricular wall of infarcted rats treated or not with bone marrow cells injected systemically or locally into the myocardium. The incidence of ectopic calcification in hearts has been reported in rare cases in children with infarcts without previous coronary artery disease. Recently, ventricular calcification has been correlated with unselected bone marrow cell transplantation into infarcted rat hearts. Echocardiographic analysis of large infarction in rats frequently reveals the presence of echogenic structures in the left ventricular wall, sometimes projecting to the lumen of the chamber. The histological examination of these echogenic structures exhibited bone, cartilage, and marrow-like formations extending from the collagen-rich matrix of the ventricle wall. Microanalytical techniques verified the presence of hydroxyapatite in the mineral phase. Ossification was found in 25 out of 30 hearts evaluated 90 days postinfarct, being observed in 14 out of 17 animals submitted to cell therapy and in 11 out of 13 infarcted rats not submitted to cell therapy. Our study indicates that chondro-osteogenic differentiation can take place in the pathological rat heart independent of animal treatment with marrow cells.