Transplantation Of Fetal Cardiomyocytes Research Articles

Embryonic Stem Cell Transplantation

Cardiovascular diseases remain the leading cause of death worldwide, and the burden is equally shared between men and women around the globe. Cardiomyocytes that die in response to disease processes or aging are replaced by scar tissue instead of new muscle cells. Although recent reports suggest an intrinsic capacity for the mammalian myocardium to regenerate via endogenous stem/progenitor cells, the magnitude of such a response appears to be minimal and has yet to be realized fully in cardiovascular patients. Despite the advances in pharmacotherapy and new biomedical technologies, the prognosis for patients diagnosed with end-stage heart failure appears to be grave. While heart transplantation is a viable option, this life-saving intervention suffers from an acute shortage of cardiac organ donors. In view of these existing issues, donor cell transplantation is emerging as a promising strategy to regenerate diseased myocardium. Studies from multiple laboratories have shown that transplantation of donor cells (e.g. fetal cardiomyocytes, skeletal myoblasts, smooth muscle cells, and adult stem cells) can improve the function of diseased hearts over a short period of time (1-4 weeks). While long-term follow-up studies are warranted, it is generally perceived that the beneficial effects of transplanted cells are mainly due to increased angiogenesis or favorable scar remodeling in the engrafted myocardium. Although skeletal myoblasts and bone marrow stem cells hold the highest potential for implementation of autologous therapies, initial results from phase I trials are not promising. In contrast, transplantation of fetal cardiomyocytes has been shown to confer protection against the induction of ventricular tachycardia in experimental myocardial injury models. Furthermore, results from multiple laboratories suggest that fetal cardiomyocytes can couple functionally with host myocytes, stimulate formation of new blood vessels, and improve myocardial function. While it is neither practical nor ethical to test the potential of fetal cardiomyocytes in clinical trials, embryonic stem (ES) cells serve as a novel source for generation of unlimited quantities of cardiomyocytes for myocardial repair. The initial success in the application of ES cells to partially repair and improve myocardial function in experimental models of heart disease has been quite promising. However, multiple hurdles need to be crossed before the potential benefits of ES cells can be translated to the clinic. In this review, we summarize the current knowledge of cardiomyocyte derivation and enrichment from ES-cell cultures and provide a brief survey of factors increasing cardiomyogenic induction in both mouse and human ES cultures. Subsequently, we summarize the current state of research using mouse and human ES cells for the treatment of heart disease in various experimental models. Furthermore, we discuss the challenges that need to be overcome prior to the successful clinical utilization of ES-derived cardiomyocytes for the treatment of end-stage heart disease. While we are optimistic that the researchers in this field will sail across the hurdles, we also suggest that a more cautious approach to the validation of ES cardiomyocytes in experimental models would certainly prevent future disappointments, as seen with skeletal myoblast studies.

A Paradigm Shift in Cardiac Pacing Therapy?

Artificial pacemakers have been continuously improved since 1949, when Jack Hopps, from the National Research Council of Canada in Ottawa, first assembled an external generator for Wilfred Bigelow and John Callaghan in the basement of the Banting Institute at the University of Toronto.1 Although Hopps’ device was not the first artificial pacemaker,2–4 the presentation by Callaghan at the 1950 American College of Surgeons meeting in Boston, Mass, stimulated a surge of experimentation that quickly led to demonstration of the utility of cardiac pacing in humans and subsequent manufacture of implantable devices.3 Since that time, remarkable advances in lead design, battery duration, programming capability, and electronic circuitry have given rise to one of the most successful and accepted life-saving, palliative therapies in modern medicine.3,5 Furthermore, medical indications for pacing therapy have expanded beyond the management of symptomatic bradycardia to include treatments for hypertrophic cardiomyopathy, neurocardiogenic syncope, ventricular tachyarrhythmia, congestive heart failure, and atrial fibrillation.6,7 Nevertheless, in spite of the fact that pacemakers represent a state-of-the-art technology, there are significant problems associated with long-term cardiac pacing. Articles pp 992 and 1000 The permanent implantation of an electronic pacemaker device is associated with complications that “…vary in clinical significance from benign to life-threatening.”7 These include the need for replacement of generators (primarily attributable to limited battery life) and leads (because of fracture, displacement, inappropriate stimulation, loss of insulating material, or tissue perforation). These problems are often exacerbated in pediatric patients owing to their size and the demands imposed by growth. Other complications include infection, thrombosis, valve dysfunction, maladaptive cardiac remodeling, and a lack of autonomic neurohumoral responsiveness. Thus, pacing therapy, although effective, continues to have important limitations. Although further refinements in the longevity and size of devices, lead biomaterials, and microprocessors seem inevitable, on the basis of …

Biological pacemaker created by fetal cardiomyocyte transplantation

The aim of this study was to investigate the feasibility of an alternative approach to electronic pacemaker by using spontaneously excitable cell grafts as a biological pacemaker in a large animal model of complete atrioventricular block. Dissociated male human atrial cardiomyocytes including sinus nodal cells were grafted into the free wall of the left ventricle in five female pigs. Three weeks after the injection of cell-grafted solution/control medium the pigs underwent catheter ablation of the atrioventricular node (AV-node). After complete AV block was created, the idioventricular beat rate was more rapid in cell-grafted pigs than that in control pigs (86+/-21 vs. 30+/-10 bpm; P<0.001). Administering of isoprenalin significantly increased idioventricular rate from 86+/-21 to 117+/-18 bpm in the cell-grafted animals (P<0.01). Electrophysiological mapping studies demonstrated that the idioventricular rhythm originated from the cell-injection site. Polymerase chain reaction verifying the existence of SRY DNA in the cell injection site indicated that the grafted male cells were survived. Furthermore, the connexin-43 and N-cadherin positive junctions between donor cardiomyocytes and host cells were identified. Xenografted fetal human atrial cardiomyocytes are able to survive and integrate into the host myocardium, and show a pacing function that can be modulated by autonomic agents.

Administration of Vascular Endothelial Growth Factor Adjunctive to Fetal Cardiomyocyte Transplantation and Improvement of Cardiac Function in the Rat Model

The functional impact of cellular transplantation and the potential role of the addition of angiogenic factors for survival of engrafts remain controversial. Vascular endothelial growth factor (VEGF) (25 ng/mL) was added to cultured fetal cardiomyocytes labeled with bromodeoxyuridine (BrDU), which was injected into the border zones of myocardial infarction 4 weeks after coronary occlusion in rat hearts. Group 1 (n = 12) received cells plus VEGF protein (100 ng), group 2 (n = 12) received cells without VEGF, group 3 (n = 10) received VEGF without cells, and group 4 (n = 12) received pure culture medium. Cardiac function was then assessed by transthoracic two-dimensional echocardiography and Langendorff perfusion system. In situ hybridization for Y chromosomes of transplanted cells, detection of BrDU-labeled cells, and platelet/endothelial cell adhesion molecule-1 (PECAM-1) staining for endothelial cells was performed. Echocardiography revealed smaller end-diastolic left ventricular dimensions in transplanted hearts in group 1 (0.83 +/- 0.13 cm 4 weeks after coronary occlusion before transplantation and 0.69 +/- 0.14 cm 2 months after transplantation, P < .05) and in group 2 (0.88 +/- 0.09 cm after coronary occlusion before transplantation and 0.76 +/- 0.08 cm 2 months after transplant), and increases in fractional shortening (34.2% +/- 8.53% before transplant and 45.3% +/- 10.9% after [P < .05] in group 1; 26.9% +/- 6.02% before transplant and 37.15% +/-8.08% after [P < .005] in group 2), whereas groups 3 and 4 showed a decrease in fractional shortening. Transplanted hearts developed higher pressures at rest (group 1, 96.8 +/- 20.8 mm Hg; group 2, 98.6 +/- 21.9 mm Hg) compared with controls (group 4, 70.9 +/- 25 mm Hg) (P < .05) and during inotropic stimulation (group 1, 111 +/- 19.5 mm Hg and group 2, 113.3 +/- 32.6 vs group 4, 80.7 +/- 31.6 mm Hg, P < .05). Histologic analysis demonstrated the presence of transplanted cells in border zones of infarcted host myocardium with neovascularization in all transplanted hearts. Transplantation of fetal cardiomyocytes results in improvement of left ventricular function. The addition of VEGF does not contribute to further improvement of left ventricular function and angiogenesis in the present model.

Recovery of contractile function of cryodamaged rat myocardium after transplantation of fetal cardiomyocytes and predifferentiated bone marrow stromal stem cells

The effect of cell transplantation into cryodamaged rat myocardium was studied on isolated hearts by increasing functional load to the left ventricle. Transplantation of allogeneic fetal cardiomyocytes improved the function of the left ventricle under conditions of considerably increased preload. Transplantation of autologous mesenchymal stem cells repaired left-ventricular function under conditions of increased pre- and afterload.

Recovery of contractile function of cryodamaged rat myocardium after transplantation of fetal cardiomyocytes and predifferentiated bone marrow stromal stem cells

Recovery of contractile function of cryodamaged rat myocardium after transplantation of fetal cardiomyocytes and predifferentiated bone marrow stromal stem cells

Recovery of contractile function of cryodamaged rat myocardium after transplantation of fetal cardiomyocytes and predifferentiated bone marrow stromal stem cells

Recovery of contractile function of cryodamaged rat myocardium after transplantation of fetal cardiomyocytes and predifferentiated bone marrow stromal stem cells

Stem Cells and Myocardial Repair

Myocardial ischemia sends a warning signal to subtended cardiomyocytes that can both promote protection by preconditioning and result in contractile dysfunction or stunning. If the ischemic period is brief ( 20 minutes), cardiomyocytes survive, contractile function recovers, and the myocardium becomes relatively resistant to subsequent ischemic insult. With prolonged periods of ischemia, cardiomyocyte death occurs by either apoptosis or necrosis, resulting in myocardial infarction. For 75 years, infarcted myocardium has been perceived as irreparable. Surgeons have focused therapeutic attention at the potentially salvageable (but narrow) periinfarction rim, where cardiac cells become hypertrophic to compensate for the functional loss within a zone of infarction. Hyperdynamic cells at the infarct border zone are further challenged by regional deficiency in oxygen-substrate delivery, resulting in cardiac remodeling (pathologic ventricular dilatation). Consequent expansion of the infarct area is caused by enhanced myocyte apoptosis, tissue fibrosis, and heart failure. Traditional dogma suggests that hypoxia controls this entire sequence. The standard surgical approach to cardiac ischemic injury is to acknowledge the loss of the infarcted muscle and to revascularize the rest of the heart in the hope of averting further damage. Compelling evidence has now been presented that all myocardial cells might not be terminally differentiated. A subset of cardiac cells might be able to replicate and form new blood vessels, permitting repopulation of portions of the infarct zone. IS THERE A SELF-RENEWING SOURCE OF CARDIOMYOCYTES? During embryogenesis, the heart grows through cellular division of cardiomyocytes. At birth, cardiomyocytes enter a postmitotic state (Go), and further heart growth occurs by hypertrophy of existing cardiomyocytes. This developmental schema works well during conditions of normoxia, but during ischemia, the myocardium is limited in its capacity to regenerate injured areas by cellular replication. Indeed, the heart attempts to compensate for cardiomyocyte loss after myocardial infarction by further hypertrophy of viable cells, but this maladaptive response frequently results in pathologic ventricular remodeling. Compared with other species, human myocardium has a disproportionately high number of nuclei with increased ploidy. Over 50% of human cardiomyocytes are tetraploid (having two complete sets of chromosomes), so it appears that cellular division in cardiomyocytes is programmed to cease after DNA replication has already occurred. The cellular signals that halt cellular division of postnatal cardiomyocytes are poorly understood. Because fetal cardiomyocytes are capable of replication, attempts have been made to use them as a potential source of cells to repair infarcted myocardium. Several challenges must be overcome for this exciting new therapy to be realized. Implanted cells must be able to survive in the hostile, inflammatory environment of the infarct, and then, to increase myocardial function, they must differentiate into phenotypically mature cells that form intercalated discs and gap junctions with the host myocardium. Recent evidence suggests that limitation of infarct progression can occur after fetal cell transplant even in the absence of ultrastructural connection with the host myocardium. In rodents, fetal and neonatal cardiac cells injected into infarcted myocardium survive within host myocardium and incorporate through intercalated discs and gap junctions. Transplantation of fetal cardiomyocytes into myocardial infarcts of rats improves heart function. On the other hand, Etzion and colleagues No competing interests declared.

Combined Procedure of Surgical Repair and Cell Transplantation for Left Ventricular Aneurysm: An Experimental Study

This study was designed to investigate the efficacy of the combined procedure of left ventricular (LV) repair and fetal cardiomyocyte transplantation (CM-TX) in a rat myocardial infarction model. A moderate-sized LV aneurysm was created by proximal ligation of the left coronary artery in 47 Lewis rats. Four weeks later, they were underwent another operation and received culture medium injection (n=10; group I), fetal CM-TX (n=10; group II), purse-string LV repair with culture medium injection (n=14; group III), or LV repair with fetal CM-TX (n=13; group IV). They were echocardiographically followed-up during the subsequent 4 weeks, and cardiac catheterization was performed in the final week. In the late period, LV dimension in group IV was smaller than that in group III (end-diastolic dimension, 0.92+/-0.02 versus 1.01+/-0.03 cm, P=0.0090; end-systolic dimension, 0.62+/-0.02 versus 0.74+/-0.04 cm, P=0.0093; at the fourth week), although they initially showed similar decreases in both groups. At the final week, end-systolic elastance was higher in group IV than in groups I, II, or III (0.61+/-0.10 versus 0.19+/-0.03, 0.30+/-0.09, 0.33+/-0.07 mm Hg/ micro L, P=0.0002, 0.0037, and 0.0042, respectively). Fetal CM-TX exerted preventive effects against late LV dilation and dysfunction after LV repair in the rat model. The results suggest that repair surgery combined with fetal CM-TX may enhance the surgical benefits for patients with LV aneurysm in the long term.

Prevascularization with gelatin microspheres containing basic fibroblast growth factor enhances the benefits of cardiomyocyte transplantation

Objective: The effects of cell transplantation on the ischemic failing heart have already been documented. However, the area in and around infarct regions is not a good environment for cells to survive in because they are exposed to poor conditions in which certain requirements cannot be adequately supplied. We therefore designed a study to investigate the efficacy of prevascularization in ischemic regions before cell transplantation. Methods: Rats with myocardial infarction were randomized into 4 groups: 11 rats received a culture medium injection to the left ventricular wall (control group), 11 received fetal cardiomyocyte transplantation (TX group), 11 received gelatin hydrogel microspheres incorporating basic fibroblast growth factor (FGF group), and 11 received basic fibroblast growth factor pretreatment sequentially, followed by cardiomyocyte transplantation (FGF-TX group). Four weeks later, left ventricular function was assessed by means of echocardiography and cardiac catheterization. Results: In the FGF and FGF-TX groups neovascularization was found in the scar tissue 1 week later. The TX, FGF, and FGF-TX groups showed better fractional shortening than the control group (TX, FGF, FGF-TX, and control: 28% ± 4.4%, 24% ± 8.6%, 27% ± 7.3%, and 17% ± 4.6%, respectively; P <.01). Left ventricular maximum time-varying elastance was higher in the FGF-TX group than in the TX and FGF groups (FGF-TX, TX, and FGF: 0.52 ± 0.23, 0.30 ± 0.08, and 0.27 ± 0.20 mm Hg/μL, respectively; P <.01). Histologically, more transplanted cells survived in the FGF-TX group than in the TX group. Conclusions: Prevascularization with basic fibroblast growth factor-incorporated microspheres enhances the benefits of cardiomyocyte transplantation. We expect that this system will contribute to regeneration medicine through its extensive application to other growth factors.J Thorac Cardiovasc Surg 2002;124:50-6

Cardiomyocyte transplantation does not reverse cardiac remodeling in rats with chronic myocardial infarction

Background. Several reports have documented the potential benefits of cell transplantation as an alternative to cardiac transplantation. This study was designed to investigate whether cardiomyocyte transplantation is effective in rats with chronic myocardial infarction. Methods. Syngeneic Lewis rats were used in this study. Chronic myocardial infarction was induced in rats by ligating the left anterior descending artery. Four weeks later, after left ventricular (LV) dysfunction with akinetic regions was confirmed by echocardiography, the rats were randomized into two groups: a group that received fetal cardiomyocyte transplantation (TX group; n = 11); and a group that received an intramyocardial injection of culture medium only (control group; n = 12). Results. Four weeks after treatment, the TX group had smaller end-systolic dimension (LVDs) (7.5 ± 0.9 vs 8.9 ± 0.8 mm, p < 0.01) and better fractional shortening (FS) (26.2 ± 5.9 vs 17.7% ± 5.1%, p < 0.01) than the control group. However, there were no differences in LV end-diastolic dimension, LVDs, and FS between baseline and post-treatment values in the TX group. In addition, plasma levels of atrial natriuretic peptide were not significantly different between the two groups 4 weeks after treatment. In microscopic examination, small amounts of transplanted cardiomyocytes were found only in the periinfarct area, not in the center of scar area, and a thicker ventricular wall in the infract area was detected in the TX group. Conclusions. Fetal cardiomyocyte transplantation prevented, but did not reverse, cardiac remodeling that was accompanied with heart failure in myocardial infarction rats. Further investigation is warranted for optimal clinical application to the failing heart.

Comparison of the effects of fetal cardiomyocyte and skeletal myoblast transplantation on postinfarction left ventricular function

Objectives: Transplantation of fetal cardiomyocytes improves function of infarcted myocardium but raises availability, immunologic, and ethical issues that justify the investigation of alternate cell types, among which skeletal myoblasts are attractive candidates. Methods: Myocardial infarction was created in rats by means of coronary artery ligation. One week later, the animals were reoperated on and intramyocardially injected with culture growth medium alone (controls, n = 15), fetal cardiomyocytes (5 × 10 6 cells, n = 11), or neonatal skeletal myoblasts (5 × 10 6 cells, n = 16). The injections consisted of a 150-μL volume and were made in the core of the infarct, and the animals were immunosuppressed. Left ventricular function was assessed by echocardiography immediately before transplantation and 1 month thereafter. Myoblast-transplanted hearts were then immunohistologically processed for the expression of skeletal muscle–specific embryonic myosin heavy chain and cardiac-specific connexin 43. Results: The left ventricular ejection fraction markedly increased in the fetal and myoblast groups from 39.3% ± 3.9% to 45% ± 3.4% ( P = .086) and from 40.4% ± 3.6% to 47.3% ± 4.4% ( P = .034), respectively, whereas it decreased in untreated animals from 40.6% ± 4% to 36.7% ± 2.7%. Transplanted myoblasts could be identified in all animals by the positive staining for skeletal muscle myosin. Conversely, clusters of connexin 43 were not observed on these skeletal muscle cells. Conclusions: These results support the hypothesis that skeletal myoblasts are as effective as fetal cardiomyocytes for improving postinfarction left ventricular function. The clinical relevance of these findings is based on the possibility for skeletal myoblasts to be harvested from the patient himself. (J Thorac Cardiovasc Surg 2000;119:1169-75)

Autologous porcine heart cell transplantation improved heart function after a myocardial infarction

Objective: Fetal cardiomyocyte transplantation improved heart function after cardiac injury. However, cellular allografts were rejected despite cyclosporine (INN: ciclosporin) therapy. We therefore evaluated autologous heart cell transplantation in an adult swine model of a myocardial infarction. Methods: In 16 adult swine a myocardial infarction was created by occlusion of the distal left anterior descending coronary artery by an intraluminal coil. Four weeks after infarction, technetium 99m–sestamibi single photon emission tomography showed minimal perfusion and viability in the infarcted region. Porcine heart cells were isolated and cultured from the interventricular septum at the time of infarction and grown in vitro for 4 weeks. Through a left thoracotomy, either cells (N = 8) or culture medium (N = 8) was injected into the infarct zone. Results: Four weeks after cell transplantation, technetium 99m–sestamibi single photon emission tomography demonstrated greater wall motion scores in the pigs receiving transplantation than in control animals (P = .01). Pigs receiving transplantation were more likely to have an improvement in perfusion scores (P = .03). Preload recruitable stroke work (P = .009) and end-systolic elastance (P = .02) were greater in the pigs receiving transplantation than in control animals. Scar areas were not different, but scar thickness was greater (P = .02) in pigs receiving transplantation. Cells labeled with bromodeoxyuridine in vitro could be identified in the infarct zone 4 weeks after transplantation. Swine receiving transplantation gained more weight than control animals (P = .02). Conclusion: Autologous porcine heart cell transplantation improved regional perfusion and global ventricular function after a myocardial infarction. (J Thorac Cardiovasc Surg 2000;119:62-8)

Fetal cell transplantation: A comparison of three cell types

Objective: We have previously reported that fetal cardiomyocyte transplantation into myocardial scar improves heart function. The mechanism by which this occurs, however, has not been elucidated. To investigate possible mechanisms by which cell transplantation may improve heart function, we compared cardiac function after transplantation of 3 different fetal cell types: cardiomyocytes, smooth muscle cells (nonstriated muscle cells), and fibroblasts (noncontractile cells). Methods: A left ventricular scar was created by cryoinjury in adult rats. Four weeks after injury, cultured fetal ventricular cardiomyocytes (n = 13), enteric smooth muscle cells (n = 10), skin fibroblasts (n = 10), or culture medium (control, n = 15 total) were injected into the myocardial scar. All rats received cyclosporine A (INN: ciclosporin). Four weeks after transplantation, left ventricular function was evaluated in a Langendorff preparation. Results: The implanted cells were identified histologically. All transplanted cell types formed tissue within the myocardial scar. At an end-diastolic volume of 0.2 mL, developed pressures in cardiomyocytes group were significantly greater than smooth muscle cells and skin fibroblasts groups (cardiomyocytes, 134% ± 22% of control; smooth muscle cells, 108% ± 14% of control; skin fibroblasts, 106% ± 17% of control; P = .0001), as were +dP/dt max (cardiomyocytes, 119% ± 37% of control; smooth muscle cells, 98% ± 18% of control; skin fibroblasts, 92% ± 11% of control; P = .0001) and –dP/dt max (cardiomyocytes, 126% ± 29% of control; smooth muscle cells, 108% ± 19% of control; skin fibroblasts, 99% ± 16% control; P = .0001). Conclusions: Fetal cardiomyocytes transplanted into myocardial scar provided greater contractility and relaxation than fetal smooth muscle cells or fetal fibroblasts. The contractile and elastic properties of transplanted cells determine the degree of improvement in ventricular function achievable with cell transplantation. (J Thorac Cardiovasc Surg 1999;118:715-25)