Autologous heart cell transplantation improves cardiac function after myocardial injury

A review on experimental surgical models and anesthetic protocols of heart failure in rats

Heart failure (HF) is a serious health and economic burden worldwide, and its prevalence is continuously increasing. Current medications effectively moderate the progression of symptoms, and there is a need for novel preventative and reparative treatments. The development of novel HF treatments requires the testing of potential therapeutic procedures in appropriate animal models of HF. During the past decades, murine models have been extensively used in fundamental and translational research studies to better understand the pathophysiological mechanisms of HF and develop more effective methods to prevent and control congestive HF. Proper surgical approaches and anesthetic protocols are the first steps in creating these models, and each successful approach requires a proper anesthetic protocol that maintains good recovery and high survival rates after surgery. However, each protocol may have shortcomings that limit the study's outcomes. In addition, the ethical regulations of animal welfare in certain countries prohibit the use of specific anesthetic agents, which are widely used to establish animal models. This review summarizes the most common and recent surgical models of HF and the anesthetic protocols used in rat models. We will highlight the surgical approach of each model, the use of anesthesia, and the limitations of the model in the study of the pathophysiology and therapeutic basis of common cardiovascular diseases.

Development of a bioreactor system for pre-endothelialized cardiac patch generation with enhanced viscoelastic properties by combined collagen I compression and stromal cell culture

Treatment of terminal heart failure still poses a significant clinical problem. Cardiac tissue engineering could offer autologous solutions for the replacement of nonfunctional myocardial tissue. So far, soft matrix construction and missing large-scale prevascularization prevented the application of sizeable cardiac repair patches. We developed a novel bioreactor system for semi-automatic compression of a collagen I hydrogel applying 16 times higher pressure than in previous studies. Resistance towards compression stress was investigated for multiple cardiac-related cell types. For scaffold prevascuarization, a tubular cavity was imprinted during the compaction process. Primary cardiac-derived endothelial cells (ECs) were isolated from human left atrial appendages (HLAAs) and characterized by fluorescence-activated cell sorting (FACS) and immunocytology. EC were then seeded into the preformed channel with dermal fibroblasts as interstitial cell component of the fully cellularized patch. After 8 days of constant perfusion culture within the same bioreactor, scaffold dynamic modulus and cell viability were analyzed. Endothelial proliferation and vessel maturation were examined by immunohistochemistry and transmission electron microscopy. Our design allowed for scaffold production and dynamic culture in a one-stop-shop model. Enhanced compression and cell-mediated matrix remodeling induced a significant increase in scaffold stiffness while ensuring excellent cell survival. For the first time, we could isolate HLAA-derived EC with proliferative potential. ECs within the central channel proliferated during flow culture, continuously expressing endothelial markers (CD31) and displaying basal membrane synthesis (collagen IV, ultrastructural analysis). After 7 days of culture, a complete endothelial monolayer could be observed. Covering cells aligned themselves in flow direction and developed mature cell-cell contacts.

Human Serum for Culture of Articular Chondrocytes

In the field of cell and tissue engineering, culture expansion of human cells in monolayer plays an important part. Traditionally, cell cultures have been supplemented with serum to support attachment and proliferation, but serum is a potential source of foreign protein contamination and viral protein transmission. In this study, we evaluated the use of human serum for experimental human articular chondrocyte expansion and to develop a method for preparation of large volumes of high-quality human serum from healthy blood donors. Human autologous serum contained high levels of epidermal-derived growth factor and platelet-derived growth factor-AB and supported proliferation up to 7 times higher than FCS in primary chondrocyte cultures. By letting the coagulation take place in a commercially available transfusion bag overnight, up to 250 ml of growth factor-rich human serum could be obtained from one donor. The allogenic human serum supported high proliferation rate without loosing expression of cartilage-specific genes. The expanded chondrocytes were able to redifferentiate and form cartilage matrix in comparable amounts to autologous serums. In conclusion, the transfusion bags allow preparation of large volumes of growth factor-rich human serum with the capacity to support in vitro cell expansion. The data further indicate that by controlling the coagulation process there are possibilities of optimizing the release of growth factors for other emerging cell therapies.

Long-Term Cell Survival and Hemodynamic Improvements after Neonatal Cardiomyocyte and Satellite Cell Transplantation into Healed Myocardial Cryoinfarcted Lesions in Rats

Cell engraftment is a new strategy for the repair of ischemic myocardial lesions. The hemodynamic effectiveness of this strategy, however, is not completely elucidated yet. In a rat model of cryothermia-induced myocardial dysfunction, we investigated whether syngeneic transplantation of neonatal cardiomyocytes or satellite cells is able to improve left ventricular performance. Myocardial infarction was induced in female Lewis rats by a standardized cryolesion to the obtuse margin of the left ventricle. After 4 weeks, 5 × 106 genetically male neonatal cardiomyocytes (n= 16) or satellite cells (n = 16) were engrafted into the myocardial scar. Sham-transplanted animals (n = 15) received injections with cell-free medium. Sham-operated animals (n = 15) served as controls. Left ventricular performance was analyzed 4 months after cell engraftment. Chimerism after this sex-mismatched transplantation was evaluated by detection of PCR-amplified DNA of the Y chromosome. The average heart weight of the infarcted animals significantly exceeded that of controls (p < 0.05). In sham-transplanted animals, mean aortic pressure, left ventricular systolic pressure, aortic flow (indicator of cardiac output), and left ventricular systolic reserve were significantly lower (p < 0.05) compared with sham-operated controls. This was associated with deterioration of ventricular diastolic function (maximal negative dP/dt, time constants of isovolumic relaxation; p < 0.05). Transplantation of satellite cells was found more effective than transplantation of neonatal cardiomyocytes, resulting in i) normalization of mean aortic pressure compared with sham-operated controls, and ii) significantly improved left ventricular systolic pressure and aortic flow (p < 0.05) compared with sham-transplanted animals. Left ventricular systolic reserve and diastolic function, however, were improved by neither satellite cell nor neonatal cardiomyocyte transplantation. Analysis of male genomic DNA revealed 3.98 ± 2.70 ng in hearts after neonatal cardiomyocyte engraftment and 6.16 ± 4.05 ng in hearts after satellite cell engraftment, representing approximately 103 viable engrafted cells per heart. Our study demonstrates i) long-term survival of both neonatal cardiomyocytes and satellite cells after transplantation into cryoinfarcted rat hearts, ii) slight superiority of satellite cells over neonatal cardiomyocytes in improving global left ventricular pump performance, and iii) no effect of both transplant procedures on diastolic dysfunction.

Building A New Treatment For Heart Failure-Transplantation of Induced Pluripotent Stem Cell-derived Cells into the Heart

Advanced cardiac failure is a progressive intractable disease and is the main cause of mortality and morbidity worldwide. Since this pathology is represented by a definite decrease in cardiomyocyte number, supplementation of functional cardiomyocytes into the heart would hypothetically be an ideal therapeutic option. Recently, unlimited in vitro production of human functional cardiomyocytes was established by using induced pluripotent stem cell (iPSC) technology, which avoids the use of human embryos. A number of basic studies including ours have shown that transplantation of iPSC-derived cardiomyocytes (iPSC-CMs) into the damaged heart leads to recovery of cardiac function, thereby establishing “proof-of-concept” of this iPSC-transplantation therapy. However, considering clinical application of this therapy, its feasibility, safety, and therapeutic efficacy need to be further investigated in the pre-clinical stage. This review summarizes up-to-date important topics related to safety and efficacy of iPSC-CMs transplantation therapy for cardiac disease and discusses the prospects for this treatment in clinical studies.

Cell-Based Therapies in Lower Urinary Tract Disorders

Cell-based therapy for the bladder has its beginnings in the 1990s with the successful isolation and culture of bladder smooth muscle cells. Since then, several attempts have been made to artificially implant native cell types and stem cell-derived cells into damaged bladders in the form of single-cell injectables or as grafts seeded onto artificial extracellular matrix. We critically examined in the literature the types of cells and their probable role as an alternative to non-drug-based, non-bowel-based graft replacement therapy in disorders of the urinary bladder. The limitations and plausible improvements to these novel therapies have also been discussed, keeping in mind an ideal therapy that could suit most bladder abnormalities arising out of varied number of disorders. In conclusion, muscle-derived cell types have consistently proven to be a promising therapy to emerge in the coming decade. However, tissue-engineered constructs have yet to prove their success in preclinical and long-term clinical setting.

Prevention of remodeling in congestive heart failure due to myocardial infarction by blockade of the renin–angiotensin system

Ventricular remodeling subsequent to myocardial infarction (MI) is a complex process and is considered to be a major determinant of the clinical course of congestive heart failure (CHF). Emerging evidence suggests that activation of the renin-angiotensin system (RAS) plays an important role in post-MI ventricular remodeling; however, it is becoming clear that this is one of several neurohumoral systems that are activated in CHF. Blockade of RAS by angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor antagonists attenuates the ventricular dysfunction, but the effects of individual drugs in reducing the morbidity and mortality in CHF patients are variable. Furthermore, there is a difference of opinion as to the time of initiation of therapy with RAS blockers after the onset of MI. Since blockade of RAS partially improves cardiac function, it is suggested that a combination therapy involving RAS blockers (angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor antagonists) and agents that affect other neurohumoral systems may prove useful for improved treatment of CHF. Although activation of RAS has been shown to promote oxidative stress in experimental studies, the use of antioxidant therapy in CHF patients is controversial. Recent experimental studies have shown that ventricular remodeling in CHF is associated with remodeling of subcellular organelles such as sarcolemma, sarcoplasmic reticulum, myofibrils and extracellular matrix in terms of their molecular structure and composition. Since attenuation of remodeling in one and/or more subcellular organelles by different agents may prevent the progression of CHF, it is a challenge to develop specific drugs affecting molecular mechanisms associated with subcellular remodeling for the improved therapy of CHF.

Does pretreatment of bone marrow mesenchymal stem cells with 5-azacytidine or double intravenous infusion improve their therapeutic potential for dilated cardiomyopathy?

BACKGROUND

This study was designed to investigate whether pretreatment of bone marrow mesenchymal stem cells (BMSCs) with 5-azacytidine (5-aza) or double intravenous infusion could enhance their therapeutic potential for dilated cardiomyopathy (DCM).

MATERIAL/METHODS

BMSCs were cultured for 2 weeks in the presence or absence of 5-aza and DCM serum. The cultured BMSCs (Groups 1 and 2), 5-aza-induced BMSCs (Groups 3 and 4), and medium alone (model control) were transplanted into 80 female Wistar rats by intravenous tail vein injection. Double infusion of BMSCs with 1-day time-interval was carried out in Groups 2 and 4. Postmortem histological analysis and evaluation of heart function were performed at 4 weeks post-transplantation.

RESULTS

Some transplanted BMSCs engrafted into myocardial tissue and were positive for cardiac marker troponin T. The hearts containing transplanted BMSCs secreted a larger amount of vascular endothelial growth factor. Cardiac function parameters and serum level of brain natriuretic peptide (BNP) did not differ among Groups 1, 3, and the model control. As compared with model control, BMSC transplantation in Groups 2 and 4 significantly decreased the serum level of BNP and improved cardiac contractile function, as evidenced by reduced left ventricular end-diastolic and end-systolic diameter, elevated ejection fraction, and fractional shortening.

CONCLUSIONS

BMSC transplantation is a promising strategy for the treatment of DCM. Pretreatment of BMSCs with 5-aza and DCM serum does not enhance their therapeutic efficacy, and the double intravenous BMSC infusion method is superior to single infusion for preserving cardiac contractile function in a rat model of DCM.

Cell therapy in the heart

Cell therapy is emerging as a new strategy to circumvent the adverse effects of heart disease. Many experimental and clinical studies investigating the transplantation of cells into the injured myocardium have yielded promising results. Moreover, data from these reports show that transplanted stem cells can engraft within the myocardium, differentiate into major cardiac cell types, and improve cardiac function. However, results from clinical trials show conflicting results. These trials demonstrate significant improvements in cardiac function for up to 6 months. However, these improved functions were diminished when examined at 18 months. In this review, we will discuss the current literature available on cell transplantation, covering studies ranging from animal models to clinical trials.

Vascularized atrial tissue patch cardiomyoplasty with omentopexy improves cardiac performance after myocardial infarction

BACKGROUND

The tissue-engineered cardiac patch can alleviate ventricular remodeling and improve functional recovery in experimental myocardial infarction. However, the size of the engineered patch is limited due to insufficient vascularization. This study evaluated the effects of autologous atrial tissue patch cardiomyoplasty and omentopexy in rats with myocardial infarction.

METHODS

Myocardial infarction was induced by left coronary artery ligation in Sprague-Dawley rats. Three weeks later, either a patch of left atrium (A group) or omentum (O group) or both (OA group) were placed over the infarct zone. The atrial tissue patch was harvested from the autologous left atrial appendage along its long axis. The rats in the Control group received rethoracotomy only. After 4 weeks, the survival of the transplanted atrial tissue patch, ventricular remodeling, and cardiac performance were examined.

RESULTS

After 4 weeks, surviving myocardium was only detected in the OA group, as indicated by immunolabeling of cardiac troponin-I. Compared with the Control group, only animals in the OA group showed improved heart function assessed by left ventricular ejection fraction (57.9% ± 5.8% vs 47.5% ± 4.5%, p < 0.05) and left ventricular fractional shortening (25.2% ± 3.6% vs 20.7% ± 2.0%, p < 0.05). The histologic analysis demonstrated increased scar thickness in the OA group. This was accompanied by increased angiogenesis of the border zone but decreased expression and activity of matrix metalloproteinase and endothelin-1 levels.

CONCLUSIONS

The omentopexy supported the survival of the autologous atrial tissue patch, which resulted in attenuated ventricular remodeling and restoration of heart function in rats with myocardial infarction. Our findings might represent a novel therapeutic strategy for heart failure.

Mesenchymal stem cells for cardiovascular regeneration

Despite recent studies suggesting that the heart has instrinsic mechanisms of self-regeneration following myocardial infarction, it cannot regenerate itself to an optimal level. Mesenchymal stem cells (MSCs) are currently being investigated for regeneration of mesenchyme-derived tissues, such as bone, cartilage and tendon. In vitro evidence suggests that MSCs can also differentiate into cardiomyogenic and vasculogenic lineages, offering another cell source for cardiovascular regeneration. In vivo, MSCs may contribute to the re-growth and protection of vasculature and cardiomyocytes, mediated by paracrine actions, and/or persist within the myocardium in a differentiated state; although proof of cardiomyocytic phenotype and functional integration remains elusive. Herein, we review the evidence of MSCs as a cell source for cardiovascular regeneration, as well as their limitations that may prevent them from being effectively used in the clinic.

Terminal differentiation is not a major determinant for the success of stem cell therapy - cross-talk between muscle-derived stem cells and host cells

We have found that when muscle-derived stem cells (MDSCs) are implanted into a variety of tissues only a small fraction of the donor cells can be found within the regenerated tissues and the vast majority of cells are host derived. This observation has also been documented by other investigators using a variety of different stem cell types. It is speculated that the transplanted stem cells release factors that modulate repair indirectly by mobilizing the host's cells and attracting them to the injury site in a paracrine manner. This process is loosely called a 'paracrine mechanism', but its effects are not necessarily restricted to the injury site. In support of this speculation, it has been reported that increasing angiogenesis leads to an improvement of cardiac function, while inhibiting angiogenesis reduces the regeneration capacity of the stem cells in the injured vascularized tissues. This observation supports the finding that most of the cells that contribute to the repair process are indeed chemo-attracted to the injury site, potentially through host neo-angiogenesis. Since it has recently been observed that cells residing within the walls of blood vessels (endothelial cells and pericytes) appear to represent an origin for post-natal stem cells, it is tempting to hypothesize that the promotion of tissue repair, via neo-angiogenesis, involves these blood vessel-derived stem cells. For non-vascularized tissues, such as articular cartilage, the regenerative property of the injected stem cells still promotes a paracrine, or bystander, effect, which involves the resident cells found within the injured microenvironment, albeit not through the promotion of angiogenesis. In this paper, we review the current knowledge of post-natal stem cell therapy and demonstrate the influence that implanted stem cells have on the tissue regeneration and repair process. We argue that the terminal differentiation capacity of implanted stem cells is not the major determinant of the cells regenerative potential and that the paracrine effect imparted by the transplanted cells plays a greater role in the regeneration process.

Heme oxygenase-1 induction enhances cell survival and restores contractility to unvascularized three-dimensional adult cardiomyocyte grafts implanted in vivo

Autologous adult cardiomyocytes are not utilized for heart repair strategies because of their rapid apoptosis after implantation. We examined whether induction of heme oxygenase-1 (HO-1), a mediator of preconditioning, could enhance early postimplant myocyte survival. Three-dimensional 5×5 mm patches of full-thickness adult murine atrial wall, including cardiomyocytes, capillary networks, and extracellular matrix, were cultured with or without HO-1 inducer cobalt protoporphyrin (CoPP), or the HO-1 inhibitor, tin protoporphyrin (SnPP), or both. Patches were then implanted subcutaneously. Freshly procured atrial wall patches implanted without preculturing served as additional controls. By 14 days postimplant, graft cardiomyocyte content was significantly greater in CoPP-treated patches than in either control group (p<0.02). Adult cardiomyocytes did not contract in culture or immediately after implantation. However, by 14 days postimplant, spontaneous contraction had recovered in 47% of CoPP-treated patches, but in only 6% of precultured patches without CoPP, 0% of SnPP-treated patches, and 0% of uncultured patches (p<0.03). CoPP-treated adult cardiomyocyte patches were also observed to remodel spontaneously into endothelial-lined chambers that pumped nonclotting blood. These findings demonstrate that adult cardiomyocytes have more plasticity and capacity for functional recovery than previously recognized and could have application as an autologous cardiomyocyte source for tissue engineering.

Evaluation of the efficacy of granulocyte colony-stimulating factor for the treatment of experimental myocardial destruction in mice

We studied the effects of recombinant granulocytic CSF on heart remodeling in BALB/c mice after cryodestruction. Administration of granulocytic CSF was started 1 day after cryodestruction (subcutaneously, 10 μg/kg/day, for 4 days). As early as after the first injection, leukocytosis in the peripheral blood started to develop, leukocyte count peaked on days 4-6 and returned to normal on day 14. Treatment with granulocytic CSF significantly increased the content of progenitor cells in the bone marrow and led to rapid development of the inflammatory reaction and myocardium infiltration with mononuclear cells. Injections of granulocytic CSF did not reduce scar area, but provided significantly less pronounced heart hypertrophy, which attests to its better functional properties. By day 30 after cryodestruction, control animals and animals receiving granulocytic CSF exhibited similar morphological picture at the site of damage. Thus, our regimen of granulocytic CSF administration produced a mobilizing effect on bone marrow progenitor cells and postinfarction heart remodeling. Direct effects of granulocytic CSF on the heart have to be established for its use in the treatment of myocardial infarction.

Embryonic stem cells overexpressing Pitx2c engraft in infarcted myocardium and improve cardiac function

This study investigated the effects on cardiomyocyte differentiation of embryonic stem cells by the overexpression of the transcription factor, Pitx2c, and examined the effects of transplantation of these differentiated cells on cardiac function in a mouse model of myocardial infarction. Pitx2c overexpressing embryonic stem cells were characterized for cardiac differentiation by immunocytochemistry, RNA analysis, and electrophysiology. Differentiated cells were transplanted by directed injection into the infarcted murine myocardium and functional measurements of blood pressure, contractility, and relaxation were performed. Histochemistry and FISH analysis performed on these mice confirmed the engraftment and cardiac nature of the transplanted cells. Pitx2c overexpressing embryonic stem cells robustly differentiated into spontaneously contracting cells which acquired cardiac protein markers and exhibited action potentials resembling that of cardiomyocytes. These cells could also be synchronized to an external pacemaker. Significant improvements (P < 0.01) in blood pressure (56%), contractility (57%), and relaxation (59%) were observed in infarcted mice with transplants of these differentiated cells but not in mice which were transplanted with control cells. The Pitx2c overexpressing cells secrete paracrine factors which when adsorbed onto a heparinated gel and injected into the infarcted myocardium produce a comparable and significant (P < 0.01) functional recovery. Pitx2c overexpression is a valuable method for producing cardiomyocytes from embryonic stem cells, and transplantation of these cardiomyocytes into infracted myocardium restores cardiac function through multiple mechanisms.

Fabrication and characterization of bio-engineered cardiac pseudo tissues

We report on fabricating functional three-dimensional (3D) tissue constructs using an inkjet based bio-prototyping method. With the use of modified inkjet printers, contractile cardiac hybrids that exhibit the forms of the 3D rectangular sheet and even the 'half heart' (with two connected ventricles) have been fabricated by arranging alternate layers of biocompatible alginate hydrogels and mammalian cardiac cells according to pre-designed 3D patterns. In this study, primary feline adult and H1 cardiomyocytes were used as model cardiac cells. Alginate hydrogels with controlled micro-shell structures were built by spraying cross-linkers in micro-drops onto un-gelled alginic acid. The cells remained viable in constructs as thick as 1 cm due to the programmed porosity. Microscopic and macroscopic contractile functions of these cardiomyocyte constructs were observed in vitro. These results suggest that the inkjet bio-prototyping method could be used for hierarchical design of functional cardiac pseudo tissues, balanced with porosity for mass transport and structural support.

Cell therapy enhances function of remote non-infarcted myocardium

Cell transplantation improves cardiac function after myocardial infarction; however, the underlying mechanisms are not well-understood. Therefore, the goals of this study were to determine if neonatal rat cardiomyocytes transplanted into adult rat hearts 1 week after infarction would, after 8-10 weeks: 1) improve global myocardial function, 2) contract in a Ca2+ dependent manner, 3) influence mechanical properties of remote uninjured myocardium and 4) alter passive mechanical properties of infarct regions. The cardiomyocytes formed small grafts of ultrastructurally maturing myocardium that enhanced fractional shortening compared to non-treated infarcted hearts. Chemically demembranated tissue strips of cardiomyocyte grafts produced force when activated by Ca2+, whereas scar tissue did not. Furthermore, the Ca2+ sensitivity of force was greater in cardiomyocyte grafts compared to control myocardium. Surprisingly, cardiomyocytes grafts isolated in the infarct zone increased Ca2+ sensitivity of remote uninjured myocardium to levels greater than either remote myocardium from non-treated infarcted hearts or sham-operated controls. Enhanced calcium sensitivity was associated with decreased phosphorylation of cTnT, tropomyosin and MLC2, but not changes in myosin or troponin isoforms. Passive compliance of grafts resembled normal myocardium, while infarct tissue distant from grafts had compliance typical of scar. Thus, cardiomyocyte grafts are contractile, improve local tissue compliance and enhance calcium sensitivity of remote myocardium. Because the volume of remote myocardium greatly exceeds that of the grafts, this enhanced calcium sensitivity may be a major contributor to global improvements in ventricular function after cell transplantation.

Paracrine effects of cell transplantation: strategies to augment the efficacy of cell therapies

Within the last few years, it has become evident that the beneficial effect of cell transplantation on ventricular function and myocardial perfusion is in large part mediated through paracrine effects on the host myocardium. Studies in which medium conditioned by cultured cells, usually mesenchymal stem cells, were injected into infarcted animal hearts have provided definitive evidence of this mechanism of action. Paracrine effects of the donor cells include but are not limited to angiogenesis, mobilization of both circulating and bone-marrow-derived stem cells, activation of cardiac-resident stem cells (CRSCs), and stabilization of the extracellular matrix (ECM). These paracrine effects can be augmented by transplantation of cells modified to express therapeutically useful transgenes, or by preconditioning through hypoxic or pharmacologic means. Strategies to enhance the paracrine effects of cell transplantation may thus be employed in the next generation of cell therapies, with greater functional benefit.

Myocardial repair achieved by the intramyocardial implantation of adult cardiomyocytes in combination with bone marrow cells

Various cytokines produced by bone marrow cells can protect adult cardiomyocytes against apoptosis. Thus, we investigated the feasibility of implanting adult cardiomyocytes in combination with bone marrow cells for myocardial repair. Ventricular cardiomyocytes were isolated from adult rats and cocultured with bone marrow cells. Using a rat model of doxorubicin-induced cardiomyopathy, we injected 6 x 10(5) adult cardiomyocytes, 3 x 10(7) bone marrow cells, or both into damaged hearts, for myocardial repair. Coculture of the cardiomyocytes with the bone marrow cells enhanced the expression of integrin-beta1D and focal adhesion kinase in cardiomyocytes, resulting in increased survival and decreased apoptosis of the cardiomyocytes after 7 days of culture. Compared with the baseline levels, cardiac function was preserved by the implantation of bone marrow cells alone and by the implantation of cardiomyocytes in combination with bone marrow cells, but it was decreased significantly 28 days after the implantation of cardiomyocytes alone. Furthermore, apoptosis of the host cardiomyocytes was decreased significantly after the implantation of bone marrow cells alone, or in combination with cardiomyocytes, compared with that after the implantation of cardiomyocytes alone (p < 0.01). Interestingly, the implantation of adult cardiomyocytes in combination with bone marrow cells resulted in a dramatic increase in the survival of donor cardiomyocytes, and induced the myogenic differentiation of donor bone marrow stem cells. Our findings indicate that cardiomyocytes and bone marrow cells can assist and compliment each other; thus, the implantation of adult cardiomyocytes in combination with bone marrow cells shows promise as a feasible new strategy for myocardial repair.

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

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

Similarities and differences in design considerations for cell therapy and pharmacologic cardiovascular clinical trials

Cell therapies hold the potential for suppression, modification, or cure of disease. Several unique challenges have been recognized as this field has developed. Many of these involve considerations of trial design. This paper summarizes the discussion and suggestions constructed during the 8th Cardiovascular Clinical Trialists Workshop, a meeting involving cardiovascular clinical trialists, biostatisticians, National Institutes of Health scientists, European and United States regulators, and pharmaceutical industry scientists. Investigators must adapt research methods to accommodate the scientific advances associated with cell therapy. Safety and efficacy of cell therapy for cardiovascular indications should be evaluated with the same degree of scientific rigor required of pharmacologic agents, and the same fundamental regulatory requirements and scientific processes apply to both. Clinical trials for these indications should also meet standards similar to those set for drug therapies. Safety should be determined throughout development, dose responsiveness should be established and, while surrogate endpoints are important development tools, the ultimate demonstration of efficacy must rely on clinical benefit. The establishment of a global safety database for cell therapy would significantly advance the field. Efforts to discover innovative therapies must be balanced by a commitment to comprehensively evaluate the safety and efficacy of the new treatments.

Burning Questions in Heart Failure Management: Why Do Surgeons and Interventional Cardiologists Talk of Regenerative Cell Therapy?

That cardiac regeneration is remotely feasible elicits thoughts of curing one of the most debilitating of human diseases. The term stem cell brings to the surface many hopes, and concerns, among physicians and the public alike, both of which have come to expect frequent advances in medical therapeutics. The evolution of public opinion toward embryonic stem cell research is clear and positive, and, unfortunately, overshadows, even confuses, that of adult stem cells, despite their use in essentially all clinical studies of cardiovascular disease to date. Strange, perhaps, that the voices of cardiovascular specialists are not to be heard.

Donor cell transplantation for myocardial disease: does it complement current pharmacological therapies?This paper is one of a selection of papers published in this Special Issue, entitled Young Investigators' Forum

Heart failure secondary to ischemic heart disease, hypertension, and myocardial infarction is a common cause of death in developed countries. Although pharmacological therapies are very effective, poor prognosis and shorter life expectancy of heart disease patients clearly indicate the need for alternative interventions to complement the present therapies. Since the progression of heart disease is associated with the loss of myocardial cells, the concept of donor cell transplantation into host myocardium is emerging as an attractive strategy to repopulate the damaged tissue. To this end, a number of donor cell types have been tested for their ability to increase the systolic function of diseased hearts in both experimental and clinical settings. Although initial clinical trials with bone marrow stem cells are encouraging, long-term consequences of such interventions are yet to be rigorously examined. While additional laboratory studies are required to address several issues in this field, there is also a clear need for further characterization of drug interactions with donor cells in these interventions. Here, we provide a brief summary of current pharmacological and cell-based therapies for heart disease. Further, we discuss the potential of various donor cell types in myocardial repair, mechanisms underlying functional improvement in cell-based therapies, as well as potential interactions between pharmacological and cell-based therapies.

Homing of intravenously infused embryonic stem cell-derived cells to injured hearts after myocardial infarction

OBJECTIVE

The present study was designed to test whether intravenously infused embryonic stem cell-derived cells could translocate to injured myocardium after myocardial infarction and improve cardiac function.

METHODS

Cultured embryonic stem cell-derived cells were transfected with green fluorescent protein. Embryonic stem cell-derived cells were administered through the tail vein (approximately 10(7) cells in 1 mL of medium for each rat) every other day for 6 days in 45 rats after myocardial infarction. Six weeks after myocardial infarction and cell infusion, cardiac function, blood flow, and the numeric density of arterioles were measured to test the benefits of cell therapy. An in vitro Transwell assay was performed to evaluate the embryonic stem cell migration.

RESULTS

Ventricular function, regional blood flow, and arteriole density were significantly increased in rats receiving intravenously infused embryonic stem cell-derived cells compared with control rats after myocardial infarction. Histologic analysis demonstrated that infused embryonic stem cell-derived cells formed green fluorescent protein-positive grafts in infarcted myocardium. Additionally, positive immunostaining for cardiac troponin I was found in hearts after myocardial infarction receiving embryonic stem cell-derived cell infusion that corresponded to the green fluorescent protein-positive staining. The Transwell migration assay indicated that cultured neonatal rat cardiomyocytes with overexpression of tumor necrosis factor alpha induced greater migration of embryonic stem cells compared with cardiomyocytes without tumor necrosis factor alpha expression.

CONCLUSIONS

Our data demonstrate that intravenously infused embryonic stem cell-derived cells homed to the infarcted heart, improved cardiac function, and enhanced regional blood flow at 6 weeks after myocardial infarction. The in vitro migration assay suggested that such a homing mechanism could be associated with locally released cytokines, such as tumor necrosis factor alpha, that are upregulated in the setting of acute myocardial infarction and heart failure.

Realizing the cardiac stem cell promise: a case for trophism

Recent advances in stem cell biology have given rise the new field of cardiac regenerative medicine. Specifically, the development of cardiac stem cell science now offers the promise of novel cardiovascular therapies based on a dynamic body of basic and translational research. Importantly, the potential wide-spread clinical application of this technology will require that therapies be optimized for individuals with potential impairments in cardiac stem cell function. To this end, the previous experience of hematopoietic stem cell therapies can provide important guidance in the development and maturation of the young cardiac stem cell field. Parallel to the impact that exogenous growth factors have made in the field of hematopoietic therapies, the discovery and potential application of the factor(s) that govern cardiac regeneration may speed the progression of cardiac stem cell technology into an assessable and potent clinical therapy.

Artificial Matrix Helps Neonatal Cardiomyocytes Restore Injured Myocardium in Rats

The purpose of this study was to investigate whether an artificial matrix can help neonatal cardiomyocytes restore an injured heart in a rat model of myocardial infarction (MI). The left coronary arteries of female Sprague Dawley (SD) rats were ligated to create MI models. Ventricular cardiomyocytes from 1- to 3-day-old SD rats (both sexes) were isolated, cultured, and labeled. Three weeks after MI, the animals were randomized into four groups: (i) group cell plus matrix (n = 12); (ii) group cell (n = 12); (iii) group matrix (n = 12); and (iv) group control (n = 11). Four weeks after transplantation, echocardiography and the Langerdoff model were used to assess heart function. Immunohistochemical staining and polymerase chain reaction (PCR) were performed to track the implanted cardiomyocytes and detect the sex-determining region Y gene on the Y chromosome. Histology study and PCR showed that transplanted cardiomyocytes survived, formed condensed tissue, and produced connected protein in group cell plus matrix. Heart function assessment indicated transplantation of cardiomyocytes plus matrix preserved left ventricle wall thickness, fraction shortening, and end-systolic internal diameter most effectively.

Haematopoietic stem cells and repair of the ischaemic heart

HSCs (haematopoietic stem cells) are multipotent stem cells that give rise to all cells of the blood cell lineage. In recent years, it has been proposed that bone marrow serves as a reservoir for cardiomyogenic precursors and that, following cardiac injury, these stem cells circulate to the site of injury where they contribute to myocardial repair and regeneration. This concept of stem cell plasticity has been controversial and, in fact, several key studies on the cardiomyogenic potential of HSCs have not been reproducible in the hands of independent investigators. Despite this controversy, the clinical community has pushed forward with clinical trials of bone marrow transplantation for the treatment of ischaemic heart disease. The following review summarizes the mechanistic underpinnings of bone marrow transplantation into ischaemic myocardium, focusing on the basic science that forms the foundation of this field, and highlights the controversies and new avenues for research that have emerged. It also describes the current state of the art in clinical trials of bone marrow transplantation for heart failure.

N-Cadherin: structure, function and importance in the formation of new intercalated disc-like cell contacts in cardiomyocytes

N-Cadherin belongs to a superfamily of calcium-dependent transmembrane adhesion proteins. It mediates adhesion in the intercalated discs at the termini of cardiomyocytes thereby serving as anchor for myofibrils at cell-cell contacts. A large body of data on the molecular structure and function of N-cadherin exists, however, little is known concerning spatial and temporal interactions between the different junctional structures during formation of the intercalated disc and its maturation in postnatal development. The progression of compensated left ventricular hypertrophy to congestive left heart failure is accompanied by intercalated disc remodeling and has been demonstrated in animal models and in patients. The long-term culture of adult rat cardiomyocytes allows to investigate the development of de novo intercalated disc-like structures. In order to analyze the dynamics of the cytoskeletal redifferentiation in living cells, we used the expression of chimeric proteins tagged with the green fluorescent protein reporter. This technique is becoming a routine method in basic research and complements video time-lapse and confocal microscopy. Cultured cardiomyocytes have been used for a variety of studies in cell biology and pharmacology. Their ability to form an electrically coupled beating tissue-like network in culture possibly allows reimplantation of such cells into injured myocardium, where they eventually will form new contacts with the healthy muscle tissue. Several groups have already shown that cardiomyocytes can be grafted successfully into sites of myocardial infarcts or cryoinjuries. Autologous adult cardiomyocyte implantation, might indeed contribute to cardiac repair after infarction, thanks to advances in tissue engineering.

Functional properties of human embryonic stem cell-derived cardiomyocytes

Regeneration of the diseased myocardium by cardiac cell transplantation is an attractive therapeutic modality. Yet, because the transplanted cardiomyocytes should functionally integrate within the diseased myocardium, it is preferable that their properties resemble those of the host. To determine the functional adaptability of human embryonic stem cell-derived cardiomyocytes (hESC-CM) to the host myocardium, the authors investigated the excitation-contraction (E-C) coupling and the responsiveness to common physiological stimuli. The main findings are: (1) hESC-CM readily respond to electrical pacing and generate corresponding [Ca(2+)](i) transients (measured by fura-2 fluorescence) and contractions (measured by video edge detector). (2) In contrast to the mature myocardium, hESC-CM display negative force-frequency relations. (3) The hESC-CM contraction is dependent on [Ca(2+)](o) and blocked by verapamil. (4) Surprisingly, ryanodine, the sarcoplasmic-endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin, and caffeine do not affect the [Ca(2+)](i) transient or contraction. Collectively, these results indicate that at the developmental stage of 45 to 60 days, the contraction is largely dependent on [Ca(2+)](o) rather than on sarcoplasmic reticulum (SR) Ca(2+) stores. The results show for the first time that the E-C coupling properties of hESC-CM differ from the adult myocardium, probably due to immature SR function. Based on these findings, genetic manipulation of hESC-CM toward the adult myocardium should be considered.

Left Ventricular Functional Recovery with Percutaneous, Transvascular Direct Myocardial Delivery of Bone Marrow-Derived Cells

BACKGROUND

The potential for cellular cardiomyoplasty to provide functional left ventricular recovery in the chronically injured heart remains unclear.

METHODS

Yorkshire swine (n = 10; 35-50 kg) had anterolateral myocardial infarction (MI) induced by coil embolization of the left anterior descending artery. Approximately 5 weeks post-MI, a composite, intravascular ultrasound-guided catheter system (TransAccess) was used to deliver an autologous, labeled, bone marrow-derived cell sub-population (approximately 3 x 10(8) cells) or saline control (approximately 50 injections/arm) through coronary veins directly into infarct and peri-infarct myocardium. Two months post-transplant, the animals had blinded endocardial and epicardial left ventricular electrical scar mapping and biventricular electrical stimulation. Coronary angiography and quantitative biplane ventriculography were performed at baseline, transplant, and sacrifice time-points.

RESULTS

Robust, viable, predominantly desmin-negative cell grafts were demonstrated post-mortem in all treatment animals. Baseline and pre-transplant global and regional wall motion was similar between groups. The cell treatment group demonstrated functional recovery with a left ventricular ejection fraction of 38.1% at the time of transplant increasing to 48.5% (p = 0.005) at sacrifice, whereas the control arm was unchanged (38.0% vs 34.3%, respectively; p = NS). The regional improvement corresponded with a reduction in percentage of hypokinetic (52.1%-42.9%, p = 0.002) and percentage of akinetic (24.8%-17.7%, p = 0.04) segments in the cell-treated animals. Epicardial scar area was not different (37 cm2 vs 23 cm2, p = 0.37) between groups.

CONCLUSIONS

Percutaneous, transvascular, direct intramyocardial bone marrow cell transplantation is safe and feasible in chronically infarcted tissue. In this pilot study, cell therapy improved overall left ventricular systolic function by recruiting previously hypokinetic or akinetic myocardial tissue.

Cardiac remodeling and failure: from molecules to man (Part III)

Given the lack of a unified theory of heart failure, future research efforts will be required to unify and synthesize our current understanding of the multiple mechanisms that control remodeling in the failing heart. Matrix remodeling and the associated activation of inflammatory cytokines and MMPs have emerged as key pathways in the development of heart failure. As such, attempts to understand the integrated control of ECM homeostasis with the bioactivation of inflammatory cytokines may be of particular relevance to the development of effective anti-remodeling approaches. Notably, the implantation of isolated populations of cells in failing myocardium has a profound and consistent anti-remodeling effect that limits the progression to CHF. These observations were consistently identified in numerous studies using diverse experimental animal models and varied cell types. Accordingly, multicenter clinical trials are underway, and the preliminary data in patients with CHF are encouraging. Despite the enormous promise of cell transplantation to restore and regenerate failing myocardium, the mechanisms underlying these profound biological effects are not understood. An improved understanding of the myocardial response to cell implantation, particularly on parameters of matrix remodeling, may help unify our current understanding of the progression of heart failure and optimize the development of this technique for its evolving therapeutic use. The following review outlines recent advances in medical and surgical approaches to control the remodeling process that underlies the progression of heart failure.

Cell Transplantation Improves Ventricular Function After a Myocardial Infarction

Background— Cell transplantation offers the promise in the restoration of ventricular function after an extensive myocardial infarction, but the optimal cell type remains controversial. Human unrestricted somatic stem cells (USSCs) isolated from umbilical cord blood have great potential to differentiate into myogenic cells and induce angiogenesis. The present study evaluated the effect of USSCs on myocardial regeneration and improvement of heart function after myocardial infarction in a porcine model.

Method and Results— The distal left anterior descending artery of Yorkshire pigs (30 to 35 kg) was occluded by endovascular implantation of a coil. Four weeks after infarction, single-photon emission computed tomography technetium 99m sestamibi scans (MIBI) and echocardiography were performed. USSCs (100×10 6 ) or culture media were then directly injected into the infarcted region (n=8 per group). Pigs were immunosuppressed by daily administration of cyclosporin A. At 4 weeks after transplantation, MIBI and echocardiography were repeated and heart function was also assessed with a pressure-volume catheter. The infarcted myocardium and implanted cells were studied histologically. MIBI showed improved regional perfusion ( P <0.05) and wall motion ( P <0.05) of the infarct region in the transplant group compared with the control. Ejection fraction evaluated by both MIBI and echocardiography decreased in the control group but increased in the transplant group ( P <0.01). Scar thickness of the transplant group was higher than the control. The grafted cells were detected 4 weeks after transplantation by both immunohistochemistry and in situ hybridization.

Conclusion— Engrafted USSCs were detected in the infarct region 4 weeks after cell transplantation, and the implanted cells improved regional and global function of the porcine heart after a myocardial infarction. This study suggests that the USSC implantation will be efficacious for cellular cardiomyoplasty.

Cellular cardiomyoplasty: development of a technique to culture human myoblasts for clinical transplantation

Some recent studies have demonstrated that epicardial injection of autologous myoblasts, obtained from satellite cells of skeletal muscle, in association to coronary artery bypass graft surgery (CABG) in patients with decreased left ventricular function secondary to ischaemic disease could be of some utility to get a better recovery of ventricular function due to the ability of these cells to grow and generate new muscle fibers over the previous fibrotic scar. The aims are the setting up of a process for the collection of the cellular cardiomyoplasty in samples of multiorganic donations and to carry out this technique in the same surgical moment as the revascularisation is performed in two patients. For this purpose we obtained muscle through biopsy of 15 human multiorgan donors and of two patients. Separation of fatty tissue, minced, and further digestion with collagenase type I (1.5 mgr/ml/2 gr by weight) and trypsin 1 x. Filtration of the cellular suspension, centrifugation and sowing of this suspension in culture medium, with 20% of human serum. Culture for three weeks until obtainment of between 200-300 million cells. Inmunohistochemistry and flow cytometry for the identification of the myoblasts was carried out. The results were obtained through flow cytometry, using CD56 as an indicator of the presence of myoblasts, between 70 and 80% of these types of cells were obtained after three weeks of culture. By inmunohistochemistry analyses, different markers were analyzed: desmin and myogenin. The results indicated the presence of a great number of positive cells with these markers, possibly myoblasts. Skeletal myoblast implant was not associated with adverse effects. The culture of autologous myoblasts is a rapid and simple technique where after three weeks of culture a great number of cells for implantation are obtained. In patients with old myocardial infarction, treatment with skeletal myoblast in conjunction with coronary artery bypass is safe and feasible. and it is easy to obtain myoblasts from muscle tissue for transplant into patients.

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.

Human bone marrow-derived mesenchymal stem cells transplanted into damaged rabbit heart to improve heart function

OBJECTIVE

The present study was designed to test whether transplantation of human bone marrow-derived mesenchymal stem cells (hMSCs) in New Zealand rabbits with myocardial infarction can improve heart function; and whether engrafted donor cells can survive and transdifferentiated into cardiomyocytes.

METHODS

Twenty milliliters bone marrow was obtained from healthy men by bone biopsy. A gradient centrifugation method was used to separate bone marrow cells (BMCs) and red blood cells. BMCs were incubated for 48 h and then washed with phosphate-buffered saline (PBS). The culture medium was changed twice a week for 28 d. Finally, hematopoietic cells were washed away to leave only MSCs. Human MSCs (hMSCs) were premarked by BrdU 72 h before the transplantation. Thirty-four New Zealand rabbits were randomly divided into myocardial infarction (MI) control group and cell treated group, which received hMSCs (MI+MSCs) through intramyocardial injection, while the control group received the same volume of PBS. Myocardial infarction was induced by ligation of the left coronary artery. Cell treated rabbits were treated with 5 x 10(6) MSCs transplanted into the infarcted region after ligation of the coronary artery for 1 h, and the control group received the same volume of PBS. Cyclosporin A (oral solution; 10 mg/kg) was provided alone, 24 h before surgery and once a day after MI for 4 weeks. Echocardiography was measured in each group before the surgery and 4 weeks after the surgery to test heart function change. The hearts were harvested for HE staining and immunohistochemical studies after MI and cell transplantation for 4 weeks.

RESULTS

Our data showed that cardiac function was significantly improved by hMSC transplantation in rabbit infarcted hearts 4 weeks after MI (ejection fraction: 0.695+/-0.038 in the cell treated group (n=12) versus 0.554+/-0.065 in the control group (n=13) (P<0.05). Surviving hMSCs were identified by BrdU positive spots in infarcted region and transdifferentiated into cardiomyocytes characterized with a positive cardiac phenotype: troponin I.

CONCLUSION

Transplantation of hMSCs could transdifferentiate into cardiomyocytes and regenerate vascular structures, contributing to functional improvement.

Injectable self-assembling peptide nanofibers create intramyocardial microenvironments for endothelial cells

BACKGROUND

Promoting survival of transplanted cells or endogenous precursors is an important goal. We hypothesized that a novel approach to promote vascularization would be to create injectable microenvironments within the myocardium that recruit endothelial cells and promote their survival and organization.

METHODS AND RESULTS

In this study we demonstrate that self-assembling peptides can be injected and that the resulting nanofiber microenvironments are readily detectable within the myocardium. Furthermore, the self-assembling peptide nanofiber microenvironments recruit progenitor cells that express endothelial markers, as determined by staining with isolectin and for the endothelial-specific protein platelet-endothelial cell adhesion molecule-1. Vascular smooth muscle cells are recruited to the microenvironment and appear to form functional vascular structures. After the endothelial cell population, cells that express alpha-sarcomeric actin and the transcription factor Nkx2.5 infiltrate the peptide microenvironment. When exogenous donor green fluorescent protein-positive neonatal cardiomyocytes were injected with the self-assembling peptides, transplanted cardiomyocytes in the peptide microenvironment survived and also augmented endogenous cell recruitment.

CONCLUSIONS

These experiments demonstrate that self-assembling peptides can create nanofiber microenvironments in the myocardium and that these microenvironments promote vascular cell recruitment. Because these peptide nanofibers may be modified in a variety of ways, this approach may enable injectable tissue regeneration strategies.

Administration of vascular endothelial growth factor adjunctive to fetal cardiomyocyte transplantation and improvement of cardiac function in the rat model

BACKGROUND

The functional impact of cellular transplantation and the potential role of the addition of angiogenic factors for survival of engrafts remain controversial.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Stimulation of Paracrine Pathways With Growth Factors Enhances Embryonic Stem Cell Engraftment and Host-Specific Differentiation in the Heart After Ischemic Myocardial Injury

Background— Growth factors play an essential role in organogenesis. We examine the potential of growth factors to enhance cell engraftment and differentiation and to promote functional improvement after transfer of undifferentiated embryonic stem cells into the injured heart.

Methods and Results— Green fluorescent protein (GFP)–positive embryonic stem cells derived from 129sv mice were injected into the ischemic area after left anterior descending artery ligation in allogenic (BALB/c) mice. Fifty nanograms of recombinant mouse vascular endothelial growth factor, fibroblast growth factor (FGF), and transforming growth factor (TGF) was added to the cell suspension. Separate control groups were formed in which only the growth factors were given. Echocardiography was performed 2 weeks later to evaluate heart function (fractional shortening [FS]), end-diastolic diameter, and left ventricular wall thickness). Hearts were harvested for histology (connexin 43, α-sarcomeric actin, CD3, CD11c, major histocompatability complex class I, hematoxylin-eosin). Degree of restoration (GFP-positive graft/infarct area ratio), expression of cardiac markers, host response, and tumorigenicity were evaluated. Cell transfer resulted in improved cardiac function. TGF-β led to better restorative effect and a stronger expression of connexin 43, α-sarcomeric actin, and major histocompatability complex class I. TGF-β and FGF retained left ventricular diameter. FS was better in the TGF-β, FGF, and embryonic stem cells-only group compared with left anterior descending artery-ligated controls. Growth factors with cells (TGF-β, FGF) resulted in higher FS and smaller end-diastolic diameter than growth factors alone.

Conclusions— Growth factors can promote in vivo organ-specific differentiation of early embryonic stem cells and improve myocardial function after cell transfer into an area of ischemic lesion. TGF-β should be considered as an adjuvant for myocardial restoration with the use of embryonic stem cells.

Insulin-like growth factor promotes engraftment, differentiation, and functional improvement after transfer of embryonic stem cells for myocardial restoration

Insulin-like growth factor-1 (IGF-1) promotes myocyte proliferation and can reverse cardiac abnormalities when it is administered in the early fetal stage. Supplementation of a mouse embryonic stem cell (ESC) suspension with IGF-1 might enhance cellular engraftment and host organ-specific differentiation after injection in the area of acute myocardial injury. In the study reported here, we sought to enhance the restorative effect of ESCs in the injured heart by adding IGF-1 to the injected cell population. Green fluorescent protein (GFP)-labeled sv129 ESCs (2.5 x 10(5)) were injected into the ischemic area after left anterior descending (LAD) artery ligation in BalbC mice. Recombinant mouse IGF-1 (25 ng) was added to the cell suspension prior to the injection (n = 5). Echocardiography was performed before organ harvest 2 weeks later. The degree of restoration (ratio of GFP+ to infarct area), expression of cardiac markers by GFP+ cells, inflammatory response, and tumorigenicity were evaluated. Mice with LAD ligation only (n = 5) and ESC transfer without IGF-1 (n = 5) served as controls. ESCs formed viable grafts and improved cardiac function. Left ventricular wall thickness was higher in the IGF-1 group (p = .025). There was a trend toward higher fractional shortening in the IGF-treated group. Histological analysis demonstrated that IGF-1 promoted expression of alpha-sarcomeric actin (p = .015) and major histocompatibility complex class I (p = .01). IGF did not affect the cellular response to the donor cells or tumorigenicity. IGF-1 promotes expression of cardiomyocyte phenotype in ESCs in vivo. It should be considered as an adjuvant to cell transfer for myocardial restoration.

Reprogramming autologous skeletal myoblasts to express cardiomyogenic function. Challenges and possible approaches

Cell transplantation therapy is emerging as a promising mode of treatment following myocardial infarction. Of the various cell types that can potentially be used for transplantation, autologous skeletal myoblasts appear particularly attractive, because this would avoid issues of immunogenicity, tumorigenesis, ethics and donor availability. Additionally, skeletal myoblasts display much higher levels of ischemic tolerance and graft survival compared to other cell types. There is some evidence for improvement in heart function with skeletal myoblast transplantation. However, histological analysis revealed that transplanted myoblasts do not transdifferentiate into functional cardiomyocytes in situ. This is evident by the lack of expression of cardiac-specific antigens, and the absence of intercalated disc formation. Instead, there is differentiation into myotubes that are not electromechanically coupled to neighboring cardiomyocytes. This could in turn limit the clinical efficacy of treatment. This review would therefore examine the various challenges faced in attempting to reprogram autologous skeletal myoblast to express cardiomyogenic function, together with the various possible strategies that could be employed to achieve this objective.

Percutaneous trans-coronary-venous transplantation of autologous skeletal myoblasts in the treatment of post-infarction myocardial contractility impairment: the POZNAN trial†

AIMS

Several experimental studies and the initial clinical experience have shown that autologous skeletal myoblast transplantation into the area of post-infarction left ventricular injury results in an increase in segmental contractile performance. This phase I clinical trial was designed to assess the feasibility and safety of autologous skeletal myoblast transplantation performed via a percutaneous trans-coronary-venous approach in patients with post-infarction left ventricular dysfunction.

METHODS AND RESULTS

Ten patients with heart failure and presence of an akinetic or a dyskinetic post-infarction injury with no viable myocardium were included in the study. Skeletal myoblasts were obtained from a biopsy specimen and grown in cell culture. Patients were treated with prophylactic amiodarone infusion before and during the procedure, except one patient. Skeletal myoblast transplantations were performed uneventfully in nine patients using the TransAccess catheter system under fluoroscopic and intravascular ultrasound guidance. In one patient, the procedure was not performed because of the inability of appropriate coronary sinus guiding wire positioning across venous valve. In five patients, the anterior interventricular vein and in four patients, the middle cardiac vein were used to access the myocardium. Two to four intramyocardial injections 1.5-4.5 cm deep were performed in each patient, delivering up to 100 million cells in 0.4-2.5 mL of saline. During 6 months follow-up, New York Heart Association class improved in all patients and ejection fraction increased 3-8% in six out of nine cases.

CONCLUSION

These data suggest the feasibility and procedural safety of myoblast transplantation performed via the trans-coronary-venous approach using the TransAccess catheter system.

Autologous Skeletal Myoblasts for Myocardial Regeneration

We overview the current knowledge about the use of skeletal myoblasts in regeneration of infarcted myocardium. Myoblasts are attractive candidates for cell source for cardiomyoplasty in chronic postmyocardial injury as indicated by experimental and initial clinical experience. We also review the recent developments in skeletal myoblasts transplantation techniques with special attention to percutaneous transvenous approach to deliver therapeutic agents into myocardium from the lumen of coronary veins under intravascular guidance.

A novel sub-population of bone marrow-derived myocardial stem cells: potential autologous cell therapy in myocardial infarction

BACKGROUND

Several studies have identified beta2-microglobulin-negative (beta2M(-)) cells as a potential stem cell fraction in the bone marrow of rats and humans. We studied the ability of bone marrow-derived beta2M(-) cells to differentiate into cardiomyocytes and reconstitute the myocardium in a model of myocardial infarction.

METHODS

beta2M(-) cells were purified from bone marrow of Lewis rats using a magnetic activated cell-sorting technique. beta2M(-) cells, 2.5 x 10(6) cells in 100 microl of phosphate-buffered saline (PBS), were transplanted 7 days after infarction into a transmural myocardial scar induced by cryoinjury in Lewis rats (n = 9). Control Group 1(n = 10) received a 100-microl injection of PBS, and Control Group 2 (n = 15) received no injection. The beta2M(-) cells were labeled before transplantation, using the membrane fluorescent intercalated dye, PKH26. Repopulation was examined at 6 and 8 weeks after transplantation. Differentiation of beta2M(-) cells into cardiac myocytes was determined by the colocalization of troponin and PKH26 to the same cell, utilizing immunohistochemistry, ultraviolet photomicroscopy and fluorescence microscopy on 6-microm serial sections. Area of engraftment within the scar was calculated by planimetry.

RESULTS

The treatment group had multiple islands of de novo-formed myocardium within the fibrous matrix of the transmural scar (mean area 35 +/- 4.2% of scar area at 6 and 8 weeks). These cells colocalized cardiac-specific troponin and PKH26. Using these techniques, no myocardial islands were seen in the control groups. Before transplantation, beta2M(-) cells were troponin-negative.

CONCLUSIONS

This study demonstrates that beta2M(-) cells represent a novel sub-population of bone marrow-derived stem cells capable of successful and substantial engraftment in areas of transmural myocardial scar, with de novo formation of cardiac myocytes. The functional significance of this observation is being studied.

Autologous skeletal myoblast transplantation for the treatment of postinfarction myocardial injury: phase I clinical study with 12 months of follow-up

BACKGROUND

Experimental studies have shown that skeletal myoblast transplantation into an area of postinfarction left ventricular injury results in an increase of segmental contractile performance that could be related to transplanted myoblasts. Initial experience with autologous skeletal myoblast transplantation in patients with postinfarction myocardial injury has also been obtained.

METHODS

Patients who survived an acute myocardial infarction and were scheduled to undergo coronary artery bypass grafting were screened by means of dobutamine stress echocardiography and included into the study when no contractility changes within akinetic/dyskinetic segments were observed. Ten patients who gave informed consent were enrolled, and autologous myoblasts (satellite cells) were isolated from the skeletal muscle biopsy. Myoblast injections into the akinetic/dyskinetic area were performed after constriction of the anastomoses during the coronary artery bypass grafting procedure.

RESULTS

Myoblast transplantations were performed after 3 weeks of in vitro culture in all patients. One patient died of a recent infarction at day 7 postoperatively because of a recent infarction in a remote area of the left ventricle. The left ventricular ejection fraction increased from 25% to 40% (mean, 35.2%) before the procedure to 29% to 47% (mean, 42.0%) during the 4-month visit (P <.05), and the effect was maintained throughout 12 months of follow-up. Sustained ventricular tachycardia was observed in 2 patients in the early postoperative period and in the other 2 patients after 2 weeks of follow-up. Prophylactic amiodarone infusion was used in the remaining 8 patients and prevented sustained ventricular tachycardia episodes.

CONCLUSIONS

Autologous skeletal myoblast transplantation for the treatment of postinfarction heart failure is feasible. Our initial observations justify further research to validate this method in a clinical practice.

Acute effects of direct cell implantation into the heart: a pressure–volume study to analyze cardiac function

BACKGROUND

To safely implant cells into the myocardium, we must establish a volume that prevents compromising cardiac performance. We studied pressure-volume (PV) to investigate the adverse effects of direct cell implantation in the acute phase.

METHODS

We used 21 minipigs. In the normal heart model, we studied PV by measuring various parameters (including end-systolic pressure, end-systolic elastance, dp/dtmax, end-diastolic volume, and time constant of isovolumetric left ventricular pressure fall [Tau]). We injected solutions into the left ventricular free wall (15 cm(2)). Sampling points were at baseline and after injection of saline (Group I, n = 4) or of blood (Group II, n = 4) at volumes of 1 ml and 10 ml up to 30 minutes after injection. In Group II, we injected additional blood (10 ml) 4 times. In the ischemic heart model, 1 month after ligating the left anterior descending artery, we injected 1 ml saline (Group III, n = 4), bone marrow mononuclear cells (10(8) cells/1 ml; Group IV, n = 4), or bone marrow stromal cells (10(8) cells/1 ml; Group V, n = 3). We studied PV before and after injection.

RESULTS

In Group I, we found no significant changes in parameters. In Group II, end-diastolic volume after 10-ml injection (24.4 +/- 3.6 ml) was smaller than end-diastolic volume at baseline (29.5 +/- 5.8 ml, p < 0.01). Tau after 10-ml injection (39.4 +/- 5.3 msec) was greater than at baseline (35.6 +/- 4.0 msec, p < 0.01). One pig died of ventricular fibrillation after a 20-ml injection of blood. We observed no detrimental effects in Groups III, IV, and V.

CONCLUSIONS

More than 10 ml cell suspension compromised diastolic function. We safely performed direct injection of bone marrow cells (1 x 10(8)/1 ml).