Systemic delivery of bone marrow-derived mesenchymal stem cells (BM-MSCs) is an attractive approach for myocardial repair. We aimed to test this strategy in a rat model after myocardial infarction ...(MI).
BM-MSCs were obtained from rat bone marrow, expanded in vitro to a purity of >50%, and labeled with 99mTc exametazime, fluorescent dye, LacZ marker gene, or bromodeoxyuridine. Rats were subjected to MI by transient coronary artery occlusion or to sham MI. 99mTc-labeled cells (4x10(6)) were transfused into the left ventricular cavity of MI rats either at 2 or 10 to 14 days after MI and were compared with sham-MI rats or MI rats treated with intravenous infusion. Gamma camera imaging and isolated organ counting 4 hours after intravenous infusion revealed uptake of the 99mTc-labeled cells mainly in the lungs, with significantly smaller amounts in the liver, heart, and spleen. Delivery by left ventricular cavity infusion resulted in drastically lower lung uptake, better uptake in the heart, and specifically higher uptake in infarcted compared with sham-MI hearts. Histological examination at 1 week after infusion identified labeled cells either in the infarcted or border zone but not in remote viable myocardium or sham-MI hearts. Labeled cells were also identified in the lung, liver, spleen, and bone marrow.
Systemic intravenous delivery of BM-MSCs to rats after MI, although feasible, is limited by entrapment of the donor cells in the lungs. Direct left ventricular cavity infusion enhances migration and colonization of the cells preferentially to the ischemic myocardium.
...all known genetic predispositions will be available and, depending on the data sharing policy, accessible to a wide range of researchers and, possibly, the public at large--this, at a time when we ...are still seeking to understand the social, clinical, and personal implications of genetic information. More research and policy analysis on the issues associated with data release is clearly needed, including an analysis of the actual harms and benefits resulting from publicly accessible data; the implications for family members and relevant communities; the appropriate balance between public access and individual privacy interests; and considerations regarding compensation for research-related injury resulting from participation in personal genome research.
OBJECTIVES
The effects of direct intramyocardial injection of the plasmid encoding vascular endothelial growth factor (phVEGF165) in the border zone of myocardial infarct tissue in rat hearts were ...investigated.
BACKGROUND
Controversy exists concerning the ability of VEGF to induce angiogenesis and enhance coronary flow in the myocardium.
METHODS
Sprague-Dawley rats received a ligation of the left coronary artery to induce myocardial infarction (MI). At 33.1 ± 6.5 days, the rats were injected with phVEGF165 at one location and control plasmid at a second location (500 μg DNA, n = 24) or saline (n = 16). After 33.1 ± 5.7 days, the hearts were excised for macroscopic and histologic analysis. Regional blood flow ratios were measured in 18 rats by radioactive microspheres.
RESULTS
phVEGF165-treated sites showed macroscopic angioma-like structures at the injection site while control DNA and saline injection sites did not. By histology, 21/24 phVEGF165-treated hearts showed increased focal epicardial blood vessel density and angioma-like formation. Quantitative morphometric evaluation in 20 phVEGF165-treated hearts revealed 44.4 ± 10.5 vascular structures per field in phVEGF165-treated hearts versus 21.4 ± 4.7 in control DNA injection sites (p < 0.05). Regional myocardial blood flow ratios between the injection site and noninfarcted area did not demonstrate any difference between phVEGF165-treated hearts (0.9 ± 0.2) and saline-treated hearts (0.7 ± 0.1).
CONCLUSIONS
Injection of DNA for VEGF in the border zone of MI in rat hearts induced angiogenesis. Angioma formation at the injection sites did not appear to contribute to regional myocardial blood flow, which may be a limitation of gene therapy for this application.
Unlike skeletal myocytes, mammalian adult cardiomyocytes cannot regenerate after injury. A possible strategy to increase viability and augment ventricular function after myocardial injury is fetal ...myocardial tissue transplantation. The engrafted fetal cells are a potential source of growth factors and can be used for cardiomyocyte-based gene therapy. The purpose of our study was to test the feasibility and efficiency of fetal cardiomyocyte transplantation into a model of myocardial infarction.
We subjected rats after myocardial infarction to three protocols of therapy. In the first protocol, tissue fragments of cultured human fetal ventricles were injected into the scar 7 to 24 days after infarction. The rats were treated with intraperitoneal injections of 12.5 mg.kg-1.d-1 cyclosporine. In the second protocol, fragments of cultured fetal rat ventricles were injected into the scar 9 to 17 days after infarction. A third group of animals with myocardial infarction was treated with injection of saline into the scar (control). After 7 to 65 days post-transplantation, hearts were harvested and processed for electron microscopy and alpha-actin immunohistochemistry. Toluidine blue staining and electron microscopy revealed the presence of engrafted human and rat cardiomyocytes in the infarcted myocardium up to 14 and 65 days after transplantation, respectively. The morphology was similar to that of cultured fetal cardiomyocytes. The engrafted fetal tissues were also stained positive for alpha-actin, which is unusual for the adult rat myocardium. Examination of control hearts detected infarcted tissue only, and alpha-actin staining was limited to vessel walls.
Fetal cardiomyocyte tissue can be implanted and survive in the infarcted myocardium. This experimental approach may provide a therapeutic strategy for cardiomyocyte-based gene therapy for introduction of therapeutic proteins into myocardial infarction.
S. Etzion, A. Battler, I. M. Barbash, E. Cagnano, P. Zarin, Y. Granot, L. H. Kedes, R. A. Kloner and J. Leor. Influence of Embryonic Cardiomyocyte Transplantation on the Progression of Heart Failure ...in a Rat Model of Extensive Myocardial Infarction. Journal of Molecular and Cellular Cardiology (2001) 33, 0000–0000. Cell transplantation has been proposed as a future therapy for various myocardial diseases. It is unknown, however, whether the encouraging results obtained in animal models of ischemia and reperfusion, cryoinjury or cardiomyopathy can be reproduced in the setting of permanent coronary artery occlusion and extensive myocardial infarction (MI). Embryonic cardiac cells were isolated and cultured for 3 days to confirm viability, morphology and to label cells with BrdU or the reporter gene LacZ. Seven days after extensive MI, rats were randomized to cell (1.5×106) transplantation (n=11) or culture medium injection (n=16) into the myocardial scar. Echocardiography study was performed before and 53±3 days after implantation to assess left ventricular (LV) remodeling and function. During follow-up, there was no mortality among cell-treated rats v 4 of 16 control rats (P=0.12). X-gal staining, BrdU and α -SMA immunohistochemistry identified the engrafted cells 1 week, 4 weeks and 8 weeks after transplantation, respectively. Antibodies against α -SMA, connexin-43, fast and slow myosin heavy chain revealed grafts in various stages of differentiation in 10 of 11 cell-treated hearts. Many of them, however, kept their embryonic phenotype and were isolated from the host myocardium by scar tissue. Serial echocardiography studies revealed that cell transplantation prevented scar thinning, LV dilatation and dysfunction while control animals developed scar thinning, significant LV dilatation accompanied by progressive deterioration in LV contractility. Transplantation of embryonic cardiomyocytes after extensive MI in a rat model attenuate LV dilatation, infarct thinning, and myocardial dysfunction. Still, many grafts remain isolated and do not differentiate into an adult phenotype, even when studied 2 months after grafting
Objectives. –
The purpose of this study was to determine the long-term outcome of fetal cell transplantation into myocardial infarction on left ventricular (LV) function and remodeling.
Background. –
...While neonatal cell transplantation improved function for acute myocardial infarction, long-term data on the effects of cell-transplant therapy using a more primitive cell on ventricular remodeling and function are needed.
Methods. –
Therefore, we injected 4 × 10
6 Fischer 344 fetal cardiac cells or medium into 1-week old infarcts in adult female Fischer rats to assess long-term outcome.
Results. –
Ten months after transplantation histologic analysis showed that cell implants were readily visible within the infarct scar. Infarct wall thickness was greater in cell-treated at 0.69 ± 0.05 mm (
n = 11) vs. medium-treated hearts at 0.33 ± 0.01 mm (
n = 19;
P = 0.0001). Postmortem LV volume was 0.41 ± 0.04 ml in cell-treated vs. 0.51 ± 0.03 ml in medium-treated hearts (
P < 0.04). Ejection fraction assessed by LV angiography was 0.40 ± 0.02 in cell-treated (
n = 16) vs. 0.33 ± 0.02 in medium-treated hearts (
n = 24;
P < 0.03) with trends towards smaller in vivo end-diastolic and end-systolic volumes in cell-treated vs. medium-treated hearts. Polymerase chain reaction analysis of the Sry gene of the Y chromosome was positive in four of five cell-treated and zero of five medium-treated hearts confirming viability of male cells in female donors.
Conclusion. –
Over the course of 10 months, fetal cardiac cell transplantation into infarcted hearts increased infarct wall thickness, reduced LV dilatation, and improved LV ejection fraction. Thus, fetal cell-transplant therapy mitigated the longer-term adverse effects of LV remodeling following a myocardial infarction.
Cell transplantation is a novel experimental strategy to treat heart disease, such as myocardial infarction and heart failure. Its beneficial effects may include active contribution of transplanted ...cells to contractile function, passive improvement of the mechanics of the heart, induction of neoangiogenesis or other indirect influences on the biology of the heart. Several cell types have been used for cardiac cell transplantation including cardiac cells from fetal or newborn animals and cardiac muscle cell lines, skeletal myoblasts and skeletal muscle cell lines, smooth muscle cells, and a variety of stem cells, either adult or embryonic. With many of these cells, encouraging results in experimental ischemic and nonischemic heart disease have been obtained including successful cell survival after transplantation, integration into the host myocardium, and improvement of the function of diseased hearts. Most of these studies found cardiac contractility improved and some found enhanced angiogenesis. However, the mechanisms of these effects remain obscure, and the impact of dosage (cell number) on functional response is completely unclear. In addition, not enough comparative studies were performed to allow preference of one cell type over the other. The current data suggest that whatever cell species is used, the best survival and integration may be accomplished if immature and undifferentiated cells are used. Any kind of stem cell has obvious advantages in terms of endless reproducibility and plasticity, but the complete differentiation and maturation into cardiac myocytes still needs to be proven. At present several clinical studies are exploring the therapeutic benefits of cellular cardiomyoplasty in patients with ischemic heart disease, but it has to be noted that there are many issues that need to be addressed before this strategy will add to the therapeutic options for patients with heart disease.
Current technologies make it possible to study thousands of genes simultaneously in the same biological sample — an approach termed gene expression profiling. Several techniques, including (i) ...differential display, (ii) serial analysis of gene expression (SAGE), (iii) subtractive hybridization and (iv) gene microarrays (Gene Chips), have been developed. Recently, gene profiling was applied in studying the mechanisms of ischemic injury and ischemic preconditioning. In the case of reversible ischemia caused by one or several brief transient episodes of complete coronary occlusion (as with ischemic preconditioning), or with a more prolonged but partial coronary ligation, many up-regulated genes were related to the “cell survival program”. Protective genes included mitogen-activated protein kinase-activated protein kinase 3 (MAPKAPK 3), heat shock proteins 70, 27, 22, B-crystalline, vascular endothelial growth factor, inducible nitric oxide synthase and plasminogen activator inhibitors 1 and 2. With permanent coronary occlusion lasting from 24 h to several weeks, and resulting in a true myocardial infarction (MI), the list of up-regulated genes included those related to remodeling (e.g., collagens I and III, fibronectin, laminin) and apoptosis (
Bax), while many down-regulated genes were related to major energy-generating pathways in the heart, namely, fatty acid metabolism. Gene expression profiling experiments have resulted in the discovery of two different genetic programs in the heart, namely, a protective program activated upon brief episodes of transient ischemia and an injury-related one activated in response to irreversible ischemic injury. Searching for factors turning on protective genes, and turning down injury-related ones, is a justifiable approach in developing new therapeutic strategies aimed to fight ischemic heart disease.
The muscle-specific MyoD family of transcription factors function as master genes that are able to prompt myogenesis in a variety of cells. The purpose of our study was to determine whether MyoD ...could induce primary cardiac fibroblasts, isolated from infarcted myocardium or pericardium, to undergo myogenic conversion in a clinically relevant approach.
Primary rat fibroblasts from 7-day-old infarcted myocardium or normal pericardium were transfected by an E1/E3-deleted adenoviral vector carrying both a human MyoD cDNA driven by a CMV promoter and a green fluorescent protein (GFP) reporter gene driven by a second CMV promoter. Expression of MyoD caused myogenic differentiation of cultured fibroblasts, as defined by elongation and fusion into multinucleated myotubes, typical cross striation as identified by electron microscopy, and positive immunostaining for sarcomeric actin, fast myosin heavy chain (MHC), and actinin. The myogenic cells (1.5x10(6)) were transplanted into the infarcted myocardium 7 days after coronary artery occlusion. By 1 month after transplantation, the converted fibroblasts gave rise to a cluster of myogenic cells that in a few hearts occupied a large part of the scar with positive immunostaining for the myogenic proteins fast-MHC and sarcomeric actin. A few cells expressed the gap junction protein connexin 43 in a disorganized manner. There was no positive staining in the control hearts treated with injections of untreated fibroblasts or culture medium.
Our work shows that it is possible to exploit the unique capacity of MyoD to activate myogenesis in fibroblasts ex vivo and to create a vast source of autologous myogenic cells for transplantation.
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