Cellular, but not direct, adenoviral delivery of vascular endothelial growth factor results in improved left ventricular function and neovascularization in dilated ischemic cardiomyopathy

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

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

Regenerative Therapy for Stroke

Stroke remains a leading cause of death and disability worldwide. An increasing number of animal studies and preclinical trials have, however, provided evidence that regenerative cell-based therapies can lead to functional recovery in stroke patients. Stem cells can differentiate into neural lineages to replace lost neurons. Moreover, they provide trophic support to tissue at risk in the penumbra surrounding the infarct area, enhance vasculogenesis, and help promote survival, migration, and differentiation of the endogenous precursor cells after stroke. Stem cells are highly migratory and seem to be attracted to areas of brain pathology such as ischemic regions. The pathotropism may follow the paradigm of stem cell homing to bone marrow and leukocytes migrating to inflammatory tissue. The molecular signaling therefore may involve various chemokines, cytokines, and integrins. Among these, stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor-4 (CXCR4) signaling is required for the interaction of stem cells and ischemia-damaged host tissues. SDF-1 is secreted primarily by bone marrow fibroblasts and is required for BMSC homing to bone marrow. Overexpression of SDF-1 in ischemic tissues has been found to enhance stem cell recruitment from peripheral blood and to induce neoangiogenesis. Furthermore, SDF-1 expression in the lesioned area peaked within 7 days postischemia, in concordance with the time window of G-CSF therapy for stroke. Recent data have shown that SDF-1 expression is directly proportional to reduced tissue oxygen tension. SDF-1 gene expression is regulated by hypoxic-inducible factor-1 (HIF-1), a hypoxia-dependent stabilization transcription factor. Thus, ischemic tissue may recruit circulating progenitors regulated by hypoxia through differential expression of HIF-1α and SDF-1. In addition to SDF-1, β2-integrins also play a role in the homing of hematopoietic progenitor cells to sites of ischemia and are critical for their neovascularization capacity. In our recent report, increased expression of β1-integrins apparently contributed to the local neovasculization of the ischemic brain as well as its functional recovery. Identification of the molecular pathways involved in stem cell homing into the ischemic areas could pave the way for the development of new treatment regimens, perhaps using small molecules, designed to enhance endogeneous mobilization of stem cells in various disease states, including chronic stroke and other neurodegenerative diseases. For maximal functional recovery, however, regenerative therapy may need to follow combinatorial approaches, which may include cell replacement, trophic support, protection from oxidative stress, and the neutralization of the growth-inhibitory components for endogenous neuronal stem cells.

Enhanced angiogenesis in ischemic skeletal muscle after transplantation of cell sheets from baculovirus-transduced adipose-derived stromal cells expressing VEGF165

Introduction

Cell therapy using adipose-derived stromal cells (ADSC) is an intensively developing approach to promote angiogenesis and regeneration. Administration technique is crucial and among others minimal constructs - cell sheets (CS) have certain advantages. Delivery of CS allows transplantation of cells along with matrix proteins to facilitate engraftment. Cells’ therapeutic potential can be also increased by expression of proangiogenic factors by viral transduction. In this work we report on therapeutic efficacy of CS from mouse ADSC transduced to express human vascular endothelial growth factor 165 a/a isoform (VEGF165), which showed potency to restore perfusion and protect tissue in a model of limb ischemia.

Methods

Mouse ADSC (mADSC) isolated from C57 male mice were expanded for CS formation (10⁶cells per CS). Constructs were transduced to express human VEGF165 by baculoviral (BV) system. CS were transplanted subcutaneously to mice with surgically induced limb ischemia and followed by laser Doppler perfusion measurements. At endpoint animals were sacrificed and skeletal muscle was evaluated for necrosis and vessel density; CS with underlying muscle was stained for apoptosis, proliferation, monocytes and blood vessels.

Results

Using BV system and sodium butyrate treatment we expressed human VEGF165 in mADSC (production of VEGF165 reached ≈ 25-27 ng/ml/10⁵ cells) and optimized conditions to ensure cells’ viability after transduction. Implantation of mock-transduced CS resulted in significant improvement of limb perfusion, increased capillary density and necrosis reduction at 2 weeks post-surgery compared to untreated animals. Additional improvement of blood flow and angiogenesis was observed after transplantation of VEGF165-expressing CS indicating enhanced therapeutic potential of genetically modified constructs. Moreover, we found delivery of mADSC as CS to be superior to equivalent dose of suspended cells in terms of perfusion and angiogenesis. Histology analysis of extracted CS detected limited proliferation and approximately 10 % prevalence of apoptosis in transplanted mADSC. Significant vascularization of CS and infiltration by monocytes were found in both – BV-transduced and control CS indicating graft and host interaction after transplantation.

Conclusions

Delivery of ADSC by subcutaneous transplantation of CS is effective for stimulation of angiogenesis and tissue protection in limb ischemia with a potential for efficacy improvement by BV transduction to express VEGF165.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0199-6) contains supplementary material, which is available to authorized users.

Autoantibodies in dilated cardiomyopathy induce vascular endothelial growth factor expression in cardiomyocytes

BACKGROUND

Autoantibodies have been identified as major predisposing factors for dilated cardiomyopathy (DCM). Patients with DCM show elevated serum levels of vascular endothelial growth factor (VEGF) whose source is unknown. Besides its well-investigated effects on angiogenesis, evidence is present that VEGF signaling is additionally involved in fibroblast proliferation and cardiomyocyte hypertrophy, hence in cardiac remodeling. Whether autoimmune effects in DCM impact cardiac VEGF signaling needs to be elucidated.

METHODS

Five DCM patients were treated by the immunoadsorption (IA) therapy on five consecutive days. The eluents from the IA columns were collected and prepared for cell culture. Cardiomyocytes from neonatal rats (NRCM) were incubated with increasing DCM-immunoglobulin-G (IgG) concentrations for 48 h. Polyclonal IgG (Venimmun N), which was used to restore IgG plasma levels in DCM patients after the IA therapy was additionally used for control cell culture purposes.

RESULTS

Elevated serum levels of VEGF decreased significantly after IA (Serum VEGF (ng/ml); DCM pre-IA: 45 ± 9.1 vs. DCM post-IA: 29 ± 6.7; P < 0.05). In cell culture, pretreatment of NRCM by DCM-IgG induced VEGF expression in a time and dose dependent manner. Biologically active VEGF that was secreted by NRCM significantly increased BNP mRNA levels in control cardiomyocytes and induced cell-proliferation of cultured cardiac fibroblast (Fibroblast proliferation; NRCM medium/HC-IgG: 1 ± 0.0 vs. NRCM medium/DCM-IgG 100 ng/ml: 5.6 ± 0.9; P < 0.05).

CONCLUSION

The present study extends the knowledge about the possible link between autoimmune signaling in DCM and VEGF induction. Whether this observation plays a considerable role in cardiac remodeling during DCM development needs to be further elucidated.

The Effect of CXCR4 Overexpression on Mesenchymal Stem Cell Transplantation in Ischemic Stroke

There is no doubt that the therapeutic efficacy of mesenchymal stem cells (MSCs) needs improvement. SDF-1 (chemokine for MSC homing) and its receptor CXCR4 play a critical role in the migration of MSCs in ischemia. We investigated the effects of the therapeutic application of MSCs transfected to overexpress CXCR4 using an adenoviral construct in the rat stroke model. Both flow cytometry and Western blot analysis indicated that the level of CXCR4 expression was low in naive hMSCs but was consistently high in CXCR4-hMSCs. In vivo migration test using the transwell system showed that the degree of migration was increased in CXCR4-hMSCs compared with the naive hMSCs and was completely blocked by treatment with AMD3100, an antagonist of the CXCR4 receptor. Compared with rats that received naive MSCs, behavioral recovery was more pronounced in rats that received CXCR4-hMSCs (p = 0.023). An immunohistochemistry study using human nuclear antibody (NuMA) showed that the migration of hMSCs in the ischemic boundary zone was increased after 3 days of injection of CXCR4-hMSCs compared with after injection of naive hMSCs. In addition, polymerase chain reaction was performed to assess the biodistribution of human-specific DNA outside the brain after intravenous injection of hMSCs. The expression of human-specific DNA was increased in the lungs of rats receiving naive MSCs, whereas the human-specific DNA expression was increased in the brain of rats receiving CXCR4-hMSCs. Our results indicate that MSCs transfected with the CXCR4 gene expression cassette may be useful in the treatment of cerebral infarction and may represent a new strategy to enhance the efficacy of MSC therapy.

Non-hypoxic stabilization of HIF-Iα during coordinated interaction between Akt and angiopoietin-1 enhances endothelial commitment of bone marrow stem cells

We previously reported that mesenchymal stem cells (MSC) co-expressing Akt and angiopoietin-1 (Ang-1) preserved infarcted heart function via angiomyogenesis. The present study determined the mechanism of co-overexpression of Akt and Ang-1 in promoting endothelial commitment of MSC. The cells were transduced with vectors encoding for Akt ((Akt)MSC), Ang-1 ((Ang-1)MSC), and both Akt and Ang-1 ((AA)MSC) using Empty vector transduced MSC ((Emp)MSC) as control. Molecular studies indicated a coordinated interaction between Akt and Ang-1 in (AA)MSC and led to non-hypoxic stabilization of hypoxia inducible factor-1α (HIF-Iα) which accentuated under 4-h anoxia. We also observed HIF-Iα dependent induction of hemeoxygenase-1, endothelial specific markers and VEGF in (AA)MSC. Vascular commitment of (AA)MSC was confirmed by immunostaining, Western blotting and flow cytometry for endothelial specific early and late markers including Flt1, Flk1, Tie2, VCAM-1, and von Willebrand Factor-VIII (vWF-VIII) in HIF-Iα dependent fashion besides exhibiting higher emigrational activity and angiogenesis in vitro. (AA)MSC transplanted into rat model of myocardial infarction showed higher Flk1 and Flt1 positivity and also promoted intrinsic Flk1(+) and Flt1(+) cell mobilization into the infarcted heart. Given the ease of availability of MSC and simplicity of approach to co-overexpress Ang-1 and Akt to enhance their endothelial commitment, the strategy will be significant for cellular angiogenesis to treat ischemic heart.

Percutaneous adventitial delivery of allogeneic bone marrow-derived stem cells via infarct-related artery improves long-term ventricular function in acute myocardial infarction

Acute myocardial infarction (AMI) results in ischemic damage and death of cardiomyocytes and loss of vasculature. Stem cell therapy has emerged as a potentially promising strategy for maximizing cardiac function following ischemic injury. Issues of cell source, delivery, and quantification of response have challenged development of clinically viable strategies. In this study we investigate the effects of a well-defined bone marrow-derived allogeneic cell product delivered by catheter directly to the myocardium via the infarct-related vessel on global and regional measures of left ventricular (LV) function in a porcine model of anterior wall myocardial infarction. Multipotent adult progenitor cells (MAPCs) were derived and expanded from the bone marrow of a donor Yorkshire pig. Anterior wall myocardial infarction (AMI) was induced by 90 min of mid-LAD occlusion using a balloon catheter. Two days after AMI was induced, either vehicle (Plasma Lyte-A, n = 7), low-dose (20 million, n = 6), or high-dose (200 million, n = 6) MAPCs were delivered directly to the myocardium via the infarct-related vessel using a transarterial microsyringe catheter-based delivery system. Echocardiography was used to measure LV function as a function of time after AMI. Animals that received low-dose cell treatment showed significant improvement in regional and global LV function and remodeling compared to the high-dose or control animals. Direct myocardial delivery of allogeneic MAPCs 2 days following AMI through the vessel wall of the infarct-related vessel is safe and results in delivery of cells throughout the infarct zone and improved cardiac function despite lack of long-term cell survival. These data further support the hypothesis of cell-based myocardial tissue repair by a paracrine mechanism and suggest a clinically translatable strategy for delivering cells at any time after AMI to modulate cardiac remodeling and function.

IGF-1Ea induces vessel formation after injury and mediates bone marrow and heart cross-talk through the expression of specific cytokines

The aim of this study was to investigate whether supplemental IGF-1Ea transgene expression induces activation of local cardiac and bone marrow stem cell population to mediate mammalian heart repair. In physiologic conditions, cardiac overexpression of the IGF-1Ea propeptide is associated with an enrichment of c-Kit/Sca-1 positive side population cells in the bone marrow and the occurrence of an endothelial-primed CD34 positive side population in the heart. This cellular profile is shown here to correlate with the expression of cytokines involved in stem cell mobilization and vessel formation. This molecular and cellular interplay favored IGF-1Ea-mediated vessel formation in injured hearts. The physiologic and pathologic connection between cytokines and stem cells in response to IGF-1Ea may represent an important model to understand how to elicit endogenous reparative signaling.

Ablation of TNF-alpha receptors influences mesenchymal stem cell-mediated cardiac protection against ischemia

Mesenchymal stem cell (MSC) infusion may reduce myocardial ischemic injury. TNF-alpha is a proinflammatory cytokine produced in large quantities during myocardial ischemia that can exert beneficial or detrimental effects on MSC function by binding to a 55-kd receptor (TNFR1) or a 75-kd receptor (TNFR2) on MSCs. We investigated whether genetic modification with ablation of TNFR1 and/or TNFR2 affects MSC-mediated protection against myocardial ischemic injury. The MSCs were harvested from wild-type mice (WT-MSCs) and knockout mice with ablation of TNFR1 and/or TNFR2 (TNFR1KO, TNFR2KO, and TNFR1/R2KO MSCs). After anesthesia was initiated via inhalation of isoflurane, myocardial ischemia was induced in rats via coronary artery ligation. Hearts were then injected with vehicle or MSCs (1 x 10 cells/mL). Myocardial function was assessed 28 days postsurgery with 2-dimensional echocardiograms and isolated heart perfusion. Myocardial tissue was collected for cytokine analysis and infarct measurements. We found that MSC treatment offered significant protection against myocardial ischemia, namely by decreasing infarct size, improving heart function, and decreasing ventricular remodeling compared with vehicle. Compared with WT-MSCs, TNFR1KO MSCs conferred increased cardiac protection, although TNFR2KO and TNFR1/R2KO MSCs conferred less cardiac protection. In addition, treatment with TNFR1KO MSCs was associated with decreased levels of proinflammatory cytokines and an increased level of vascular endothelial growth factor in the myocardium, whereas treatment with TNFR2KO or TNFR1/R2KO MSCs was associated with increased levels of proinflammatory cytokines and a decreased level of vascular endothelial growth factor compared with treatment with WT-MSCs. We conclude that MSC TNFR1 and TNFR2 play important roles in MSC-mediated cardiac protection after myocardial ischemia.

Gene therapy for ischemic heart disease

Current pharmacologic therapy for ischemic heart disease suffers multiple limitations such as compliance issues and side effects of medications. Revascularization procedures often end with need for repeat procedures. Patients remain symptomatic despite maximal medical therapy. Gene therapy offers an attractive alternative to current pharmacologic therapies and may be beneficial in refractory disease. Gene therapy with isoforms of growth factors such as VEGF, FGF and HGF induces angiogenesis, decreases apoptosis and leads to protection in the ischemic heart. Stem cell therapy augmented with gene therapy used for myogenesis has proven to be beneficial in numerous animal models of myocardial ischemia. Gene therapy coding for antioxidants, eNOS, HSP, mitogen-activated protein kinase and numerous other anti apoptotic proteins have demonstrated significant cardioprotection in animal models. Clinical trials have demonstrated safety in humans apart from symptomatic and objective improvements in cardiac function. Current research efforts are aimed at refining various gene transfection techniques and regulation of gene expression in vivo in the heart and circulation to improve clinical outcomes in patients that suffer from ischemic heart disease. In this review article we will attempt to summarize the current state of both preclinical and clinical studies of gene therapy to combat myocardial ischemic disease. This article is part of a Special Section entitled "Special Section: Cardiovascular Gene Therapy".

Toll-like receptor 2 mediates mesenchymal stem cell-associated myocardial recovery and VEGF production following acute ischemia-reperfusion injury

Toll-like receptor 2 (TLR2), a key component of the innate immune system, is linked to inflammation and myocardial dysfunction after ischemia-reperfusion injury (I/R). Treatment of the heart with mesenchymal stem cells (MSCs) is known to improve myocardial recovery after I/R in part by paracrine factors such as VEGF. However, it is unknown whether TLR2 activation on the MSCs affects MSC-mediated myocardial recovery and VEGF production. We hypothesized that the knockout of TLR2 on the MSCs (TLR2KO MSCs) would 1) improve MSC-mediated myocardial recovery and 2) increase myocardial and MSC VEGF release. With the isolated heart perfusion system, Sprague-Dawley rat hearts were subjected to I/R and received one of three intracoronary treatments: vehicle, male wild-type MSCs (MWT MSCs), or TL2KO MSCs. All treatments were performed immediately before ischemia, and heart function was measured continuously. Postreperfusion, heart homogenates were analyzed for myocardial VEGF production. Contrary to our hypothesis, only MWT MSC treatment significantly improved the recovery of left ventricular developed pressure and the maximal positive and negative values of the first derivative of pressure. In addition, VEGF production was greatest in hearts treated with MWT MSCs. To investigate MSC production of VEGF, MSCs were activated with TNF in vitro and the supernatants collected for ELISA. In vitro basal levels of MSC VEGF production were similar. However, with TNF activation, MWT MSCs produced significantly more VEGF, whereas activated TLR2KO MSC production of VEGF was unchanged. Finally, we observed that MWT MSCs proliferated more rapidly than TLR2KO MSCs. These data indicate that TLR2 may be essential to MSC-mediated myocardial recovery and VEGF production.

Stem cell therapy: pieces of the puzzle

Acute ischemic injury and chronic cardiomyopathies can cause irreversible loss of cardiac tissue leading to heart failure. Cellular therapy offers a new paradigm for treatment of heart disease. Stem cell therapies in animal models show that transplantation of various cell preparations improves ventricular function after injury. The first clinical trials in patients produced some encouraging results, despite limited evidence for the long-term survival of transplanted cells. Ongoing research at the bench and the bedside aims to compare sources of donor cells, test methods of cell delivery, improve myocardial homing, bolster cell survival, and promote cardiomyocyte differentiation. This article reviews progress toward these goals.

IL-18 binding protein-expressing mesenchymal stem cells improve myocardial protection after ischemia or infarction

IL-18 is a proinflammatory cytokine known to cause tissue injury by inducing inflammation and cell death. Increased levels of IL-18 are associated with myocardial injury after ischemia or infarction. IL-18-binding protein (IL-18BP), the naturally occurring inhibitor of IL-18 activity, decreases the severity of inflammation in response to injury. In the present study, mesenchymal stem cells (MSCs) derived from mice transgenic for over expression of human IL-18BP were tested in rat models of global myocardial ischemia and acute myocardial infarction. Improved myocardial function is associated with production of VEGF, and in vitro, IL-18BP MSCs secreted higher levels of constitutive VEGF compared to wild-type MSCs. Whereas IL-18 increased cell death and reduced VEGF in wild-type MSCs, IL-18BP MSCs were protected. In an isolated heart model, intracoronary infusion of IL-18BP MSCs before ischemia increased postischemic left ventricular (LV) developed pressure to 79.5 + or - 9.47 mmHg compared to 59.3 + or - 7.8 mmHg in wild-type MSCs and 37.8 + or - 5 mmHg in the vehicle group. Similarly, using a coronary artery ligation model, intramyocardial injection of IL-18BP MSCs improved LV ejection fraction to 67.8 + or - 1.76% versus wild-type MSCs (57.4 + or - 1.33%) and vehicle (39.2 + or - 2.07%), increased LV fractional shortening 1.25-fold over wild-type MSCs and 1.95-fold over vehicle, decreased infarct size to 38.8 + or - 2.16% compared to 46.4 + or - 1.92% in wild-type MSCs and 60.7 + or - 2.2% in vehicle, reduced adverse ventricular remodeling, increased myocardial VEGF production, and decreased IL-6 levels. This study provides the concept that IL-18BP genetically modified stem cells improve cardioprotection over that observed with unmodified stem cells.

Heart failure management: the present and the future

Clinical heart failure has been defined for a long time as a clinical syndrome with symptoms and signs including shortness of breath, cyanosis, ascites, and edema. However, in recent years, with the thought of promoting early diagnosis and heart-failure prevention, the concept of heart failure has often been defined simply as a subject with severe LV dysfunction and a dilated left ventricle, or by some, defined by evidence of increased circulating levels of molecular markers of cardiac dysfunction, such as ANP and BNP. Heart failure has been considered an irreversible clinical end point. Current medical management for heart failure only relieves symptoms, slows deterioration, and prolongs life modestly. However, in the recent years, rejuvenation of the failing myocardium began to seem possible as the accumulating preclinical studies demonstrated that rejuvenating the myocardium at the molecular and cellular level can be achieved by gene therapy or stem cell transplantation. Here, we review selected novel modalities that have been shown in preclinical studies to exert beneficial effects in animal models of severe LV dysfunction and seem to have the potential to make an impact in the clinical practice of heart-failure management.

Cell-based therapy for heart failure: skeletal myoblasts

Satellite cells are committed precursor cells residing in the skeletal muscle. These cells provide an almost unlimited regeneration potential to the muscle, contrary to the heart, which, although proved to contain cardiac stem cells, possesses a very limited ability for self-renewal. The idea that myoblasts (satellite cell progenies) may repopulate postinfarction scar occurred around the mid-1990s. Encouraging results of preclinical studies triggered extensive research, which led to the onset of clinical trials. These trials have shown that autologous skeletal myoblast transplantation to cure heart failure is feasible and relatively safe (observed incidences of arrhythmia). Because most of the initial studies on myoblast application into postischemic heart have been carried out as an adjunct to routine surgical procedures, the true clinical outcome of such therapy in regard to cell implantation is blurred and requires to be elucidated. The mechanism by which implantation of skeletal myoblast may improve heart function is not clear, especially in the light of inability of these cells to couple electromechanically with a host myocardium. Successful myoblast therapy depends on a number of factors, including: delivery to the target tissue, long-term survival, efficacious engraftment, differentiation into cardiomyocytes, and integration into the new, unique microenvironment. All these steps constitute a potential goal for cell manipulation aiming to improve the overall outcome of such therapy. Precise understanding of the mechanism by which cells improve cardiac function is essential in giving the sensible direction of further research.

Panoramic view of the Fifth International Symposium on Stem Cell Therapy and Applied Cardiovascular Biotechnology, April 2008, Madrid (Spain)

The Fifth International Symposium on Stem Cell Therapy and Applied Cardiovascular Biotechnology was held on April 24th-25th, 2008, at the Auditorium of the High Council of Scientific Research of Spain (CSIC) in Madrid, as a continuation of a series of yearly meetings, organized in an attempt to encourage translational research in this field and facilitate a positive interaction among experts from several countries, along with industry representatives and journalists. In addition, members of the Task Force of the European Society concerning the clinical investigation of the use of autologous adult stem cells for repair of the heart gathered and discussed an update of the previous consensus, still pending of publication. In this article, we summarize some of the main topics of discussion, the state-of-the-art and latest advances in this field, and new challenges brought up for the near future.

Update on therapeutic vascularization strategies

The ability to exploit angiogenesis and vascularization as a therapeutic strategy will be of enormous benefit to a wide range of medical and tissue-engineering applications. Angiogenic growth factor and cell-based therapies have thus far failed to produce a robust healing response in clinical trials for a variety of ischemic diseases, while engineered tissue substitutes are still size-limited by a lack of vascularization. The purpose of this review is to investigate current research advances in therapeutic vascularization strategies applied to ischemic disease states, tissue engineering and regenerative medicine. Recent advances are discussed that focus on better regulation of growth factor delivery and attempts to better mimic natural processes by delivering combinations of multiple growth factors, cells and bioactive materials in the right spatial and temporal setting. Some unconventional approaches and novel therapeutic targets that hold significant potential are also discussed.

Adult stem cells and their trans-differentiation potential--perspectives and therapeutic applications

Stem cells are self-renewing multipotent progenitors with the broadest developmental potential in a given tissue at a given time. Normal stem cells in the adult organism are responsible for renewal and repair of aged or damaged tissue. Adult stem cells are present in virtually all tissues and during most stages of development. In this review, we introduce the reader to the basic information about the field. We describe selected stem cell isolation techniques and stem cell markers for various stem cell populations. These include makers for endothelial progenitor cells (CD146/MCAM/MUC18/S-endo-1, CD34, CD133/prominin, Tie-2, Flk1/KD/VEGFR2), hematopoietic stem cells (CD34, CD117/c-Kit, Sca1), mesenchymal stem cells (CD146/MCAM/MUC18/S-endo-1, STRO-1, Thy-1), neural stem cells (CD133/prominin, nestin, NCAM), mammary stem cells (CD24, CD29, Sca1), and intestinal stem cells (NCAM, CD34, Thy-1, CD117/c-Kit, Flt-3). Separate section provides a concise summary of recent clinical trials involving stem cells directed towards improvement of a damaged myocardium. In the last part of the review, we reflect on the field and on future developments.

Disruption of protein kinase A interaction with A-kinase-anchoring proteins in the heart in vivo: effects on cardiac contractility, protein kinase A phosphorylation, and troponin I proteolysis

Protein kinase A (PKA)-dependent phosphorylation is regulated by targeting of PKA to its substrate as a result of binding of regulatory subunit, R, to A-kinase-anchoring proteins (AKAPs). We investigated the effects of disrupting PKA targeting to AKAPs in the heart by expressing the 24-amino acid regulatory subunit RII-binding peptide, Ht31, its inactive analog, Ht31P, or enhanced green fluorescent protein by adenoviral gene transfer into rat hearts in vivo. Ht31 expression resulted in loss of the striated staining pattern of type II PKA (RII), indicating loss of PKA from binding sites on endogenous AKAPs. In the absence of isoproterenol stimulation, Ht31-expressing hearts had decreased +dP/dtmax and -dP/dtmin but no change in left ventricular ejection fraction or stroke volume and decreased end diastolic pressure versus controls. This suggests that cardiac output is unchanged despite decreased +dP/dt and -dP/dt. There was also no difference in PKA phosphorylation of cardiac troponin I (cTnI), phospholamban, or ryanodine receptor (RyR2). Upon isoproterenol infusion, +dP/dtmax and -dP/dtmin did not differ between Ht31 hearts and controls. At higher doses of isoproterenol, left ventricular ejection fraction and stroke volume increased versus isoproterenol-stimulated controls. This occurred in the context of decreased PKA phosphorylation of cTnI, RyR2, and phospholamban versus controls. We previously showed that expression of N-terminal-cleaved cTnI (cTnI-ND) in transgenic mice improves cardiac function. Increased cTnI N-terminal truncation was also observed in Ht31-expressing hearts versus controls. Increased cTnI-ND may help compensate for reduced PKA phosphorylation as occurs in heart failure.

Characterization of the paracrine effects of human skeletal myoblasts transplanted in infarcted myocardium

BACKGROUND

The discrepancy between the functional improvements yielded experimentally by skeletal myoblasts (SM) transplanted in infarcted myocardium and the paucity of their long-term engraftment has raised the hypothesis of cell-mediated paracrine mechanisms.

METHODS AND RESULTS

We analyzed gene expression and growth factors released by undifferentiated human SM (CD56(+)), myotubes (SM cultured until confluence) and fibroblasts-like cells (CD56(-)). Gene expression revealed up-regulation of pro-angiogenic (PGF), anti-apoptotics (BAG-1, BCL-2), heart development (TNNT2, TNNC1) and extracellular matrix remodelling (MMP-2, MMP-7) genes in SM. In line with the gene expression profile, the analysis of culture supernatants of SM by ELISA identified the release of growth factors involved in angiogenesis (VEGF, PIGF, angiogenin, angiopoietin, HGF and PDGF-BB) as well as proteases involved in matrix remodelling (MMP2, MMP9 and MMP10) and their inhibitors (TIMPs). Culture of smooth muscle cells (SMC), cardiomyocytes (HL-1) and human umbilical vein endothelial cells (HUVECs) with SM-released conditioned media demonstrated an increased proliferation of HUVEC, SMC and cardiomyocytes (p<0.05) and a decrease in apoptosis of cardiomyocytes (p<0.05). Analysis of nude rats transplanted with human SM demonstrated expression of human-specific MMP-2, TNNI3, CNN3, PGF, TNNT2, PAX7, TGF-beta, and IGF-1 1 month after transplant.

CONCLUSIONS

Our data support the paracrine hypothesis whereby myoblast-secreted factors may contribute to the beneficial effects of myogenic cell transplantation in infarcted myocardium.

Genetic enhancement of stem cell engraftment, survival, and efficacy

Cell-based therapies for the prevention and treatment of cardiac dysfunction offer the potential to significantly modulate cardiac function and improve outcomes in patients with cardiovascular disease. To date several clinical studies have suggested the potential efficacy of several different stem cell types; however, the benefits seen in clinical trials have been inconsistent and modest. In parallel, preclinical studies have identified key events in the process of cell-based myocardial repair, including stem cell homing, engraftment, survival, paracrine factor release, and differentiation that need to be optimized to maximize cardiac repair and function. The inconsistent and modest benefits seen in clinical trials combined with the preclinical identification of mediators responsible for key events in cell-based cardiac repair offers the potential for cell-based therapy to advance to cell-based gene therapy in an attempt to optimize these key events in the hope of maximizing clinical benefit. Below we discuss potential key events in cardiac repair and the mediators of these events that could be of potential interest for genetic enhancement of stem cell-based cardiac repair.

Direct delivery of syngeneic and allogeneic large-scale expanded multipotent adult progenitor cells improves cardiac function after myocardial infarct

BACKGROUND

Multipotent adult progenitor cells (MAPC) comprise interesting candidates for myocardial regeneration because of a broad differentiation ability and immune privilege. We aimed to compare the improvement of cardiac function by syngeneic and allogeneic MAPC produced on a large scale using a platform optimized from MAPC research protocols.

METHODS

Myocardial infarction was induced in Lewis rats by direct left anterior descending ligation followed immediately by direct injection into the infarct border zone of either Sprague-Dawley or Lewis MAPC from large-scale expansions. Echocardiography was performed to evaluate improvement in cardiac function, and immunohistochemistry was performed to identify MAPC within the infarct zone.

RESULTS

Significant increases were observed in functional performance in animals transplanted with expanded MAPC compared with saline controls, with no significant differences between the syngeneic and allogeneic groups. Immunostaining demonstrated significant engraftment of expanded MAPC at 1 day after acute myocardial infarction, with <10% of either syngeneic or allogeneic cells remaining at 6 weeks. At this point there was no evidence of myocardial regeneration. However, a significant increase in vascular density within the infarct zone in MAPC-transplanted animals was observed, and MAPC were found to produce high levels of VEGF in culture.

DISCUSSION

These findings support a model in which delivery of expanded MAPC following acute myocardial infarction results in improvement in cardiac function because of paracrine effects resulting in vascular density increases, as well as potentially other trophic effects, supporting newly injured cardiac myocytes. Thus transplantation with MAPC may represent a promising therapeutic strategy with application in the stimulation of neovascularization in ischemic heart disease.

Umbilical cord blood-derived progenitor cells enhance muscle regeneration in mouse hindlimb ischemia model

Progenitor cell therapy is a potential new treatment option for ischemic conditions in the myocardium and skeletal muscles. However, it remains unclear whether umbilical cord blood (UCB)-derived progenitor cells can provide therapeutic effects in ischemic muscles and whether ex vivo gene transfer can be used for improving the effect. In this study, the use of a lentiviral vector led to efficient transduction of both UCB-derived hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). Our method resulted in a long-term transgene expression and did not alter the differentiation potential of either HSCs or MSCs. In addition, we studied the therapeutic potential of CD133(+) and MSC progenitor cells transduced ex vivo with lentiviruses encoding the mature form of vascular endothelial growth factor D (VEGF-D(DeltaNDeltaC)) or the enhanced green fluorescent protein (eGFP) marker gene in a nude mouse model of skeletal muscle ischemia. Progenitor cells enhanced the regeneration of ischemic muscles without a detectable long-term engraftment of either CD133(+) or MSC progenitor cells. Our results show that, rather than directly participating in angiogenesis or skeletal myogenesis, UCB-derived progenitor cells indirectly enhance the regenerative capacity of skeletal muscle after acute ischemic injury. However, VEGF-D gene transfer of progenitor cells did not improve the therapeutic effect in ischemic muscles.

Cardiovascular Molecular Imaging

The goal of this review is to highlight how molecular imaging will impact the management and improved understanding of the major cardiovascular diseases that have substantial clinical impact and research interest. These topics include atherosclerosis, myocardial ischemia, myocardial viability, heart failure, gene therapy, and stem cell transplantation. Traditional methods of evaluation for these diseases will be presented first, followed by methods that incorporate conventional and molecular imaging approaches.

SDF-1 expression by mesenchymal stem cells results in trophic support of cardiac myocytes after myocardial infarction

Stem cell transplantation at the time of acute myocardial infarction (AMI) improves cardiac function. Whether the improved cardiac function results from regeneration of cardiac myocytes, modulation of remodeling, or preservation of injured tissue through paracrine mechanisms is actively debated. Because no specific stem cell population has been shown to be optimal, we investigated whether the benefit of stem cell transplantation could be attributed to a trophic effect on injured myocardium. Mesenchymal stem cells secrete SDF-1 and the interaction of SDF-1 with its receptor, CXCR4, increases survival of progenitor cells. Therefore, we compared the effects of MSC and MSC engineered to overexpress SDF-1 on cardiac function after AMI. Tail vein infusion of syngeneic MSC and MSC:SDF-1 1 day after AMI in the Lewis rat led to improved cardiac function by echocardiography by 70.7% and 238.8%, respectively, compared with saline controls 5 wk later. The beneficial effects of MSC and MSC:SDF-1 transplantation were mediated primarily through preservation, not regeneration of cardiac myocytes within the infarct zone. The direct effect of SDF-1 on cardiac myocytes was due to the observation that, between 24 and 48 h after AMI, SDF-1-expressing MSC increased cardiac myocyte survival, vascular density (18.2+/-4.0 vs. 7.6+/-2.3 vessels/mm2, P<0.01; SDF-1:MSC vs. MSC), and cardiac myosin-positive area (MSC: 49.5%; mSC:SDF-1: 162.1%) within the infarct zone. There was no evidence of cardiac regeneration by the infused MSC or endogenous cardiac stem cells based on lack of evidence for cardiac myocytes being derived from replicating cells. These results indicate that stem cell transplantation may have significant beneficial effects on injured organ function independent of tissue regeneration and identify SDF-1:CXCR4 binding as a novel target for myocardial preservation.

Effect of cell-based intercellular delivery of transcription factor GATA4 on ischemic cardiomyopathy

Recent loss-of-function studies highlight the importance of the transcription factor GATA4 in the myocardial response to injury in the adult heart. However, the potential effects of gain-in-function of GATA4 overexpression, and transcription factors in general, is hindered by the fact that transcription factors are neither secreted nor taken up by cells. Chimeric proteins incorporating motifs of cell-penetrating proteins are secreted from cells and internalized by surrounding cells. We engineered a chimeric protein consisting of GATA4 and the cell-penetrating protein VP22. Cardiac fibroblasts stably transfected with the GATA4:VP22, GFP:VP22, or green fluorescent protein (GFP) constructs were transplanted into Lewis rats 1 month after left anterior descending ligation. GATA4:VP22 expression in the border zone was associated with increased cardiac myosin expression and cardiac myocyte size (30 mum versus 19 mum, P<0.01). Compared with the GFP:VP22 control group, 6 weeks after cardiac fibroblast transplantation (10 weeks after myocardial infarction), animals that received GATA4:VP22-expressing cardiac fibroblasts demonstrated increased cardiac function and less negative remodeling. These data demonstrate a novel strategy for transcription factor delivery to injured myocardium and indicate that the delivery of GATA4 locally to the infarct border zone induces multiple local effects in the border zone cardiac myocytes resulting in beneficial ventricular remodeling and improved global left ventricular function.

Hind Limb Ischemia-Reperfusion in the Leptin Receptor Deficient (db/db) Mouse

BACKGROUND

Diabetic patients have high incidence of peripheral vascular disease and limb loss after acute extremity injury. Experiments were designed to test the hypothesis that acute tissue injury in leptin receptor deficient (Db) diabetic (type2) mice would be more severe than in non-diabetic mice.

METHODS

Db and wild type (Wt) mice were subjected to 3 h of ischemia followed by either 4 or 24 h of reperfusion (3/4 IR, 3/24 IR). Muscle analyzed for tissue viability (mitochondrial activity), cytokines (KC-murine equivalent of human IL-8, TNFalpha, IL-6), growth factor, and histological evaluation (neutrophils/uninjured muscle fibers). Tissue perfusion was detected during basal and reperfusion conditions using laser Doppler imaging.

RESULTS

Mitochondrial activity and histological evaluation for tissue injury did not differ in the Db versus Wt mice at the time intervals studied. When compared with their respective sham animals, both Db and Wt mice had similarly increased levels of KC, IL-6, and VEGF after 3/24 IR. TNFalpha levels increased in Db but not Wt mice after IR. Although absolute increases in TNFalpha and KC were higher in Db mice, VEGF levels were actually lower in the Db mice.

CONCLUSION

The patterns of tissue perfusion, cytokines, and growth factors were different in Db versus Wt mice. At the acute time intervals studied, these differences did not correlate with an expected greater degree of acute muscle injury in Db mice.

Ex vivo delivered stromal cell-derived factor-1alpha promotes stem cell homing and induces angiomyogenesis in the infarcted myocardium

We aimed to optimize non-viral transfection of human stromal cell derived factor (SDF-1alpha) gene into skeletal myoblasts (SkM) and, transplant these cells to establish transient SDF-1alpha gradient to favor extra-cardiac stem cell translocation into infarcted heart. Optimized conditions for transfection of SDF-1alpha gene into syngenic SkM were achieved using FuGene6/phSDF-1alpha (3:2v/w, 4 h transfection) with 125 microM ZnCl(2) (p<0.001). After characterization for transgene overexpression by immunostaining, ELISA and PCR, the cells were transplanted in female rat model of myocardial infarction. Thirty-six rats were grouped (n=12/group) to receive 70 microl DMEM without cells (group-1) or containing 1.5 x 10(6) non-transfected (group-2) or SDF-1alpha transfected SkM (group-3). On day 4 post-transplantation (in 4 animals/group), marked expression of SDF-1alpha/sry-gene (p=0.003), total Akt, phospho-Akt and Bcl2 was observed in group-3. The number of CD31(+), C-kit(+) and CD34(+) cells was highest in group-3 hearts (p<0.01). Blood vessel density in group-3 was higher in both scar and peri-scar regions (p<0.001) as compared with other groups. Echocardiography showed improved indices of left ventricle contractile function and remodeling in group-3 (p<0.05) as compared with groups-1 and -2. We conclude that ex vivo SDF-1alpha transgene delivery promotes stem and progenitor cell migration to the heart, activates cell survival signaling and enhances angiomyogenesis in the infarcted heart.

Stem cell therapy enhances electrical viability in myocardial infarction

Clinical studies suggest increased arrhythmia risk associated with cell therapy for myocardial infarction (MI); however, the underlying mechanisms are poorly understood. We hypothesize that the degree of electrical viability in the infarct and border zone associated with skeletal myoblast (SKMB) or mesenchymal stem cell (MSC) therapy will determine arrhythmia vulnerability in the whole heart. Within 24 h of LAD ligation in rats, 2 million intramyocardially injected SKMB (n=6), intravenously infused MSC (n=7), or saline (n=7) was administered. One month after MI, cardiac function was determined and novel optical mapping techniques were used to assess electrical viability and arrhythmia inducibility. Shortening fraction was greater in rats receiving SKMB (17.8%+/-5.3%, p=0.05) or MSC (17.6%+/-3.0%, p<0.01) compared to MI alone (10.1%+/-2.2%). Arrhythmia inducibility score was significantly greater in SKMB (2.8+/-0.2) compared to MI (1.4+/-0.5, p=0.05). Inducibility score for MSC (0.6+/-0.4) was significantly lower than SKMB (p=0.01) and tended to be lower than MI. Optical mapping revealed that MSC therapy preserved electrical viability and impulse propagation in the border zone, but SKMB did not. In addition, injected SKMBs were localized to discrete cell clusters where connexin expression was absent. In contrast, infused MSCs engrafted in a more homogeneous pattern and expressed connexin proteins. Even though both MSC and SKMB therapy improved cardiac function following MI in rat, SKMB therapy significantly increased arrhythmia inducibility while MSC therapy tended to lower inducibility. In addition, only MSC therapy was associated with enhanced electrical viability, diffuse engraftment, and connexin expression, which may explain the differences in arrhythmia inducibility.

Cell-based gene therapy for the prevention and treatment of cardiac dysfunction

A substantial need exists for new treatments to prevent and treat cardiac dysfunction. In the 1990s, there was great hope for gene therapy in this regard. Since that time, the focus has switched to cell therapy-in particular, therapy-with the aim of inducing myocardial regeneration. Individually, gene and cell therapies still have substantial promise. Ultimately, however, the convergence of both techniques might be necessary to achieve improvements in cardiac function and more successful clinical outcomes in patients with cardiac dysfunction. This approach has already been adopted for treatment of malignancies. Several gene products are currently being studied, including growth factors and chemokines that can modulate the survival and function of cardiac myocytes following an ischemic event and influence remodeling of the left ventricle. However, several issues remain, including the optimization and characterization of cell types, selection of vectors for gene transfer, and identification of appropriate strategies for delivery. Here, we review the potential and need for cell-based gene therapy for the prevention and treatment of cardiac dysfunction and attempt to discuss the unresolved issues.

Mechanical and Electrical Effects of Cell-Based Gene Therapy for Ischemic Cardiomyopathy Are Independent

Cell-based gene therapy to alter the myocardial tissue microenvironment has been shown to improve mechanical cardiac function, but little is known regarding its effects on arrhythmogenic risk. Clinical studies with skeletal myoblasts (SKMBs) have suggested a potential increase in arrhythmogenic risk. Therefore, we studied the functional mechanical and electrical effects of transient reestablishment of stem cell homing via transplantation of stromal-cell derived factor-1 (SDF-1)-expressing SKMBs. Eight weeks after anterior myocardial infarction, rats received in five divided doses into the periinfarct zone 1 million SKMBs transfected with AdSDF-1 (n=15) or AdGFP (n=8). Echocardiography was used to quantify changes in cardiac function, and optical mapping was used to determine the arrhythmogenic risk. Eight weeks after cell therapy, we observed a 54% (p=0.004) increase in shortening fraction in AdSDF-1:SKMB-treated rats, but only an 18.8% increase (p=not significant) with GFP:SKMB. SDF-1-treated hearts exhibited an increase in vascular density compared with control SKMBs (34.9+/-7.1 vs. 20.7+/-5.6 vessels/mm2; p<0.01). Optical mapping performed 8 weeks after cell therapy revealed that all animals that received SKMBs regardless of viral transfection had inducible ventricular tachycardia (VT) whereas only 50% of saline-treated animals had inducible VT (p<0.05). Transient reestablishment of stem cell homing via transplantation of modified SKMBs is sufficient to improve cardiac function. However, despite improved mechanical function, the risk of ventricular tachycardia increased. We propose that future studies on functional effects of cell-based gene therapies should address both mechanical and electrical consequences.

Monocyte chemotactic protein-3 is a myocardial mesenchymal stem cell homing factor

MSCs have received attention for their therapeutic potential in a number of disease states, including bone formation, diabetes, stem cell engraftment after marrow transplantation, graft-versus-host disease, and heart failure. Despite this diverse interest, the molecular signals regulating MSC trafficking to sites of injury are unclear. MSCs are known to transiently home to the freshly infarcted myocardium. To identify MSC homing factors, we determined chemokine expression pattern as a function of time after myocardial infarction (MI). We merged these profiles with chemokine receptors expressed on MSCs but not cardiac fibroblasts, which do not home after MI. This analysis identified monocyte chemotactic protein-3 (MCP-3) as a potential MSC homing factor. Overexpression of MCP-3 1 month after MI restored MSC homing to the heart. After serial infusions of MSCs, cardiac function improved in MCP-3-expressing hearts (88.7%, p < .001) but not in control hearts (8.6%, p = .47). MSC engraftment was not associated with differentiation into cardiac myocytes. Rather, MSC engraftment appeared to result in recruitment of myofibroblasts and remodeling of the collagen matrix. These data indicate that MCP-3 is an MSC homing factor; local overexpression of MCP-3 recruits MSCs to sites of injured tissue and improves cardiac remodeling independent of cardiac myocyte regeneration.

Progress and prospects: cell based regenerative therapy for cardiovascular disease

Experimental and clinical studies are progressing simultaneously to investigate the mechanisms and efficacy of progenitor cell treatment after an acute myocardial infarction and in chronic congestive heart failure. Multipotent progenitor cells appear to be capable of improving cardiac perfusion and/or function; however, the mechanisms still are unclear, and the issue of whether or not trans-differentiation occurs remains unsettled. Both experimentally and clinically, cells originating from different tissues have been shown capable of restoring cardiac function, but more recently multiple groups have identified resident cardiac progenitor cells that seem to participate in regenerating the heart after injury. Clinically, cells originating from blood or bone marrow have been proven to be safe whereas injection of skeletal myoblasts has been associated with the occurrence of ventricular arrhythmias. Myoblasts can transform into rapidly beating myotubes; however, thus far convincing evidence for electro-mechanical coupling between myoblasts and cardiomyocytes is lacking. Moving forward, mechanistic studies will benefit from the use of genetic markers and Cre/lox reporter systems that are less prone to misinterpretation than fluorescent antibodies, and a more convincing answer regarding therapeutic efficacy will come from adequately powered randomized placebo controlled trials.

Engineered cell therapy for sustained local myocardial delivery of nonsecreted proteins

Novel strategies for the treatment of congestive heart failure have taken the form of gene and cell therapy to induce angiogenesis, optimize calcium handling by cardiac myocytes, or regenerate damaged myocardial tissue. Arguably both gene- and cell-based therapies would be benefited by having the ability to locally deliver specific transcription factors and other usually nonsecreted proteins to cells in the surrounding myocardial tissue. The herpes simplex virus type 1 (HSV-1) tegument protein VP22 has been shown to mediate protein intercellular trafficking to mammalian cells and finally localize into the nucleus, which makes it a useful cargo-carrying functional protein in cell-based gene therapy. While VP22 has been studied as a means to modulate tumor growth, little is known about the distribution and transport kinetics of VP22 in the heart and its potential application in combination with autologous cell transplantation for the delivery of proteins to myocardial tissue. The aim of this study was to evaluate the efficacy of VP22 fusion protein intercellular trafficking combined with autologous cell transplantation in the heart. In an in vitro study untransfected rat heart cells were cocultured with stably transfected rat cardiac fibroblasts (RCF) with fusion constructs of VP22. The control experiment was untransfected rat heart cells co-plated with RCF stably transfected with enhanced green fluorescence protein (eGFP). The Lewis rat model was selected for in vivo study. In the in vitro studies there was a 14-fold increase in the number of GFP-positive cells 48 h after initiating coculture with VP22-eGFP RCF compared to eGFP RCF. In the rat model, transplantation of VP22-eGFP expressing RCF led to VP22-eGFP fusion protein delivery to an area of myocardial tissue that was 20-fold greater than that observed when eGFP RCF were transplanted. This area appeared to reach a steady state between 7 and 10 days after transplantation. The VP22-eGFP area consisted of eGFP-positive endothelium, smooth muscle cells, and cardiac myocytes with delivery to an area of approximately 1 mm2 of myocardial tissue. Our data suggest a viable strategy for the delivery of proteins that are not naturally secreted or internalized, and provide the first insight into the feasibility and effectiveness of cell-penetrating proteins combined with cell transplantation in the heart.

Skeletal muscle cells expressing VEGF induce capillary formation and reduce cardiac injury in rats

BACKGROUND

We tested a preemptive combined cell/gene therapy strategy of skeletal myoblasts transfected with Ad(5)RSVVEGF-165 in an ischemia/reperfusion rat model to increase collateral blood flow to nonischemic heart tissue.

METHODS

Lewis rats were injected with placebo (Control), 10(6) skeletal myoblasts (SkM), or 10(6) skeletal myoblasts transfected with Ad(5)RSVVEGF-165 (SkM(+)) into the left ventricle 1week before ischemia. Left ventricle end-diastolic pressure, scar area, and capillary density were assessed 4weeks later.

RESULTS

Local expression of human vascular endothelial growth factor was accompanied by an increase in capillary density in the SkM(+) group compared with that in the SkM and Control groups (700+/-40 vs. 289+/-18 and 318+/-59capillaries/mm(2), respectively; p<0.05). After 3weeks, the myocardial scar area was reduced in SkM(+) vs. Control (5.3+/-0.4% and 14.8+/-1.6%, p<0.05), while injected cells alone (SkM) did not cause improvement compared with Control (11.8+/-2.1% vs. 14.8+/-1.6%, p>0.05). The decrease in the scar area in SkM(+) was accompanied by an increase in the capillary density compared with that in SkM and Control 30days after cell injection (1005+/-108 vs. 524+/-16 and 528+/-26capillaries/mm(2), respectively; p<0.05). The scar areas were discrete (5.3-14.8%) and left ventricle end-diastolic pressure in all groups were comparable (p>0.05).

CONCLUSIONS

The combined cell/gene therapy strategy of genetically modified myoblast cells expressing angiogenic factors injected into the myocardium induced capillary formation and prevented the extension and development of cardiac damage associated with ischemia/reperfusion in rats.

Gene transfer for ischemic cardiovascular disease: is this the end of the beginning or the beginning of the end?

The past decade has represented a period of high expectations for cardiovascular gene transfer on the basis of the findings from preclinical experiments and promising early clinical results. Yet, randomized studies have not demonstrated similar results. Do these poor results mean that gene transfer for ischemic cardiovascular disease has failed in its promise, or do they merely signify the inherent challenges of a pioneering field? In this paper we briefly review the clinical experience of gene transfer for ischemic cardiovascular disease and propose future directions for research.

Optical mapping of late myocardial infarction in rats

Late myocardial infarction (MI) is associated with ventricular arrhythmias and sudden cardiac death. The exact mechanistic relationship between abnormal cellular electrophysiology, conduction abnormalities, and arrhythmogenesis associated with late MI is not completely understood. We report a novel, rapid dye superfusion technique to enable whole heart, high-resolution optical mapping of late MI. Optical mapping of action potentials was performed in normal rats and rats with anterior MI 7 days after left anterior descending artery ligation. Hearts from normal rats exhibited normal action potentials and impulse conduction. With the use of programmed stimulation to assess arrhythmia inducibility, 29% of hearts with late MI had inducible sustained ventricular tachycardia, compared with 0% in normal rats. A causal relationship between the site of infarction, abnormal action potential conduction (i.e., block and slow conduction), and arrhythmogenesis was observed. Optical mapping techniques can be used to measure high-resolution action potentials in a whole heart model of late MI. This experimental model reproduces many of the electrophysiological characteristics (i.e., conduction slowing, block, and ventricular tachycardia) associated with MI in patients. Importantly, the results of this study can enhance our ability to understand the interplay between cellular heterogeneity, conduction abnormalities, and arrhythmogenesis associated with MI.

Correlation of autologous skeletal myoblast survival with changes in left ventricular remodeling in dilated ischemic heart failure

OBJECTIVES

The effect of autologous skeletal myoblast transplantation has not been rigorously studied in the setting of end-stage ischemic heart failure free of concomitant coronary revascularization. The aims of the present study were to determine autologous skeletal myoblast survival and its effects on left ventricular function and remodeling in sheep with dilated ischemic heart failure.

METHODS

Ischemic heart failure (left ventricular ejection fraction, 30% +/- 2%; left ventricular end-systolic volume index, 82 +/- 9 mL/m2) was created in sheep (n = 11) with serial left circumflex coronary artery microembolizations. Instruments were inserted for the long-term determination of left ventricular global and regional dimensions, hemodynamics, and pressure-volume analysis after autologous skeletal myoblast transplantation (approximately 3.0 x 10(8) myoblasts; heart failure plus autologous skeletal myoblast group, n = 5) or without (heart failure-control group, n = 6). Measurements were performed in conscious animals.

RESULTS

Autologous skeletal myoblast-derived skeletal muscle was found in all injected animals at 6 weeks. In ischemic heart failure, autologous skeletal myoblast cardiomyoplasty failed to improve systolic (left ventricular ejection fraction, 29% +/- 4%; dP/dT(max), 2863 +/- 152 mm Hg/s; end-systolic elastance, 1.6 +/- 0.22) or diastolic (left ventricular end-diastolic pressure, 21 +/- 2 mm Hg; time constant of relaxation (Tau), 34 +/- 4 ms; dP/dT(min), -1880 +/- 68 mm Hg/s) function. There was, however, attenuation in the left ventricular dilatation after autologous skeletal myoblast transplantation (change in end-systolic volume index, 14% +/- 4% vs 32% +/- 6%; P < .05). The effects of autologous skeletal myoblast-derived skeletal muscle were exclusive to the left ventricular short-axis dimension and dependent on autologous skeletal myoblast survival (R2 = 0.59, P = .006, n = 11).

CONCLUSIONS

Autologous skeletal cardiomyoplasty was able to attenuate left ventricular remodeling in sheep with end-stage ischemic heart failure.

Current Status of Cellular Therapy for Ischemic Heart Disease

Cellular therapy for acute myocardial infarction and ischemic cardiomyopathy has entered clinical trials across the globe. Early promising results have now provided the justification for larger randomized and blinded trials to address the efficacy of cellular therapy. A variety of fresh or cultured autologous cells have been delivered by catheter-guided endocardial, catheter-guided intracoronary, catheter-guided transvenous, and direct epicardial routes. This review will summarize the clinical data and highlight salient basic science data that support the ongoing efforts to identify the optimal cellular therapy both for acute myocardial infarction and chronic ischemic cardiomyopathy patients.

An Overview of Myoblast Transplantation for Myocardial Regeneration

Regenerative medicine represents a new frontier in treatment of disease, particularly cardiovascular disease. The contractile elements of the heart, cardiomyocytes, lack the capacity for any postnatal proliferation or regeneration. Therefore, repair of heart damage can be achieved only by manipulating cardiomyocytes to regrow or by introducing exogenous cells with the capacity to restore function to the myocardium. Many attempts have been made with various cell types to repair the damaged myocardium. We will present here a summary of some of those studies and also present in detail studies utilizing a promising, near-term, and practical source of cells for treatment of heart disease: autologous skeletal myoblasts.

Unchain my heart: the scientific foundations of cardiac repair

In humans, the biological limitations to cardiac regenerative growth create both a clinical imperative--to offset cell death in acute ischemic injury and chronic heart failure--and a clinical opportunity; that is, for using cells, genes, and proteins to rescue cardiac muscle cell number or in other ways promote more efficacious cardiac repair. Recent experimental studies and early-phase clinical trials lend credence to the visionary goal of enhancing cardiac repair as an achievable therapeutic target.