Key Roles of RGD-Recognizing Integrins During Cardiac Development, on Cardiac Cells, and After Myocardial Infarction.

Cardiac cells interact with the extracellular matrix (ECM) proteins through integrin mechanoreceptors that control many cellular events such as cell survival, apoptosis, differentiation, migration, and proliferation. Integrins play a crucial role in cardiac development as well as in cardiac fibrosis and hypertrophy. Integrins recognize oligopeptides present on ECM proteins and are involved in three main types of interaction, namely with collagen, laminin, and the oligopeptide RGD (Arg-Gly-Asp) present on vitronectin and fibronectin proteins. To date, the specific role of integrins recognizing the RGD has not been addressed. In this review, we examine their role during cardiac development, their role on cardiac cells, and their upregulation during pathological processes such as heart fibrosis and hypertrophy. We also examine their role in regenerative and angiogenic processes after myocardial infarction (MI) in the peri-infarct area. Specific targeting of these integrins may be a way of controlling some of these pathological events and thereby improving medical outcomes.

Possible Treatment of Myocardial Infarct Based on Tissue Engineering Using a Cellularized Solid Collagen Scaffold Functionalized with Arg-Glyc-Asp (RGD) Peptide.

Currently, the clinical impact of cell therapy after a myocardial infarction (MI) is limited by low cell engraftment due to low cell retention, cell death in inflammatory and poor angiogenic infarcted areas, secondary migration. Cells interact with their microenvironment through integrin mechanoreceptors that control their survival/apoptosis/differentiation/migration and proliferation. The association of cells with a three-dimensional material may be a way to improve interactions with their integrins, and thus outcomes, especially if preparations are epicardially applied. In this review, we will focus on the rationale for using collagen as a polymer backbone for tissue engineering of a contractile tissue. Contractilities are reported for natural but not synthetic polymers and for naturals only for: collagen/gelatin/decellularized-tissue/fibrin/Matrigel™ and for different material states: hydrogels/gels/solids. To achieve a thick/long-term contractile tissue and for cell transfer, solid porous compliant scaffolds are superior to hydrogels or gels. Classical methods to produce solid scaffolds: electrospinning/freeze-drying/3D-printing/solvent-casting and methods to reinforce and/or maintain scaffold properties by reticulations are reported. We also highlight the possibility of improving integrin interaction between cells and their associated collagen by its functionalizing with the RGD-peptide. Using a contractile patch that can be applied epicardially may be a way of improving ventricular remodeling and limiting secondary cell migration.

Células madre mesenquimales de médula ósea y de cordón umbilical en el tratamiento de enfermedades cardiovasculares / Mesenchymal stem cells from bone marrow and umbilical cord for treating cardiovascular disease

Las células madre (CM) internacionalmente se dividen en embrionarias o fetales y somáticas, en dependencia de su origen. Las CM embrionarias son células pluripotenciales que generan todo tipo de células del organismo y no se emplean por problemas éticos y de lesgilaciones vigentes que prohíben su uso, además de la oposición de la iglesia. Las células somáticas, por el contrario, son las que se usan y ellas son multipotenciales, pero teóricamente solo generan un tipo de tejido específico

Stem cells (CM) are internationally divided into embryonic or fetal and somatic, depending on their origin. The embryonic CMs are pluripotent cells that generate all types of cells of the organism and are not used for ethical problems and current infractions that prohibit their use, in addition to the opposition of the church. Somatic cells, on the other hand, are the ones that are used and they are multipotential, but theoretically they only generate a specific type of tissue

Creating the bioartificial myocardium for cardiac repair: challenges and clinical targets.

The association of stem cells with tissue-engineered scaffolds constitutes an attractive approach for the repair of myocardial tissue with positive effects to avoid ventricular chamber dilatation, which changes from a natural elliptical to spherical shape in heart failure patients. Biohybrid scaffolds using nanomaterials combined with stem cells emerge as new therapeutic tool for the creation of 'bioartificial myocardium' and 'cardiac wrap bioprostheses' for myocardial regeneration and ventricular support. Biohybrids are created introducing stem cells and self-assembling peptide nanofibers inside a porous elastomeric membrane, forming cell niches. Our studies lead to the creation of semi-degradable 'ventricular support bioprostheses' for adaptative LV and/or RV wrapping, designed with the concept of 'helical myocardial bands'. The goal is to restore LV elliptical shape, and contribute to systolic contraction and diastolic filling (suction mechanism). Cardiac wrapping with ventricular bioprostheses may reduce the risk of heart failure progression and the indication for heart transplantation.

Development of cardiac support bioprostheses for ventricular restoration and myocardial regeneration.

OBJECTIVES: Ventricular constraint devices made of polyester and nitinol have been used to treat heart failure patients. Long-term follow-up has not demonstrated significant benefits, probably due to the lack of effects on myocardial tissue and to the risk of diastolic dysfunction. The goal of this experimental study is to improve ventricular constraint therapy by associating stem cell intrainfarct implantation and a cell-seeded collagen scaffold as an interface between the constraint device and the epicardium. METHODS: In a sheep ischaemic model, three study groups were created: Group 1: coronary occlusion without treatment (control group). Group 2: postinfarct ventricular constraint using a polyester device (Acorn CorCap). Group 3: postinfarct treatment with stem cells associated with collagen matrix and the polyester device. Autologous adipose mesenchymal stem cells cultured in hypoxic conditions were injected into the infarct and seeded into the collagen matrix. RESULTS: At 3 months, echocardiography showed the limitation of left ventricular end-diastolic volume in animals both treated with constraint devices alone and associated with stem cells/collagen. In Group 3 (stem cell + collagen treatment), significant improvements were found in ejection fraction (EF) and diastolic function evaluated by Doppler-derived mitral deceleration time. In this group, histology showed a reduction of infarct size, with focuses of angiogenesis and minimal fibrosis interface between CorCap and the epicardium due to the interposition of the collagen matrix. CONCLUSIONS: Myocardial infarction treated with stem cells associated with a collagen matrix and ventricular constraint device improves systolic and diastolic function, reducing adverse remodelling and fibrosis. The application of bioactive molecules and the recent development of nanobiotechnologies should open the door for the creation of a new semi-degradable ventricular support bioprosthesis, capable of controlled stability or degradation in response to physiological conditions of the left or right heart.

Development of bioartificial myocardium by electrostimulation of 3D collagen scaffolds seeded with stem cells.

Electrostimulation (ES) can be defined as a safe physical method to induce stem cell differentiation. The aim of this study is to evaluate the effectiveness of ES on bone marrow mesenchymal stem cells (BMSCs) seeded in collagen scaffolds in terms of proliferation and differentiation into cardiomyocytes. BMSCs were isolated from Wistar rats and seeded into 3D collagen type 1 templates measuring 25 × 25 × 6 mm. Bipolar in vitro ES was performed during 21 days. Electrical impedance and cell proliferation were measured. Expression of cardiac markers was assessed by immunocytochemistry. Viscoelasticity of collagen matrix was evaluated. Electrical impedance assessments showed a low resistance of 234±41 Ohms which indicates good electrical conductivity of collagen matrix. Cell proliferation at 570 nm as significantly increased in ES groups after seven day (ES 0.129±0.03 vs non-stimulated control matrix 0.06±0.01, P=0.002) and after 21 days, (ES 0.22±0.04 vs control 0.13±0.01, P=0.01). Immunocytoche mistry of BMSCs after 21 days ES showed positive staining of cardiac markers, troponin I, connexin 43, sarcomeric alpha-actinin, slow myosin, fast myosin and desmin. Staining for BMSCs marker CD29 after 21 days was negative. Electrostimulation of cell-seeded collagen matrix changed stem cell morphology and biochemical characteristics, increasing the expression of cardiac markers. Thus, MSC-derived differentiated cells by electrostimulation grafted in biological scaffolds might result in a convenient tissue engineering source for myocardial diseases.

Comparison of the effects of adenosine, inosine, and their combination as an adjunct to reperfusion in the treatment of acute myocardial infarction.

Adenosine and inosine are both key intracellular energy substrates for nucleotide synthesis by salvage pathways, especially during ischemic stress conditions. Additionally they both possess cell protective and cell repair properties. The objective of this study is to detect potential advantages of the combination of adenosine and inosine versus each drug alone, in terms of ventricular function, infarct size reduction and angiogenesis. Myocardial ischemia was created in rodents and treated with adenosine, inosine or their combination. Results of experiments showed that the combination of both drugs significantly reduced infarct size and improved myocardial angiogenesis and ventricular function. The two compounds, while chemically similar, use different intracellular pathways, allowing for complementary biological activities without overlapping. The drug combination at specific 1 : 5 adenosine : inosine dose ratio demonstrated positive cardiologic effects, deserving further evaluation as an adjunct to reperfusion techniques during and after acute coronary syndrome. The association of adenosine and inosine may contribute to reduce myocardial infarction morbidity and mortality rates.

Stem cells cardiac differentiation in 3D systems.

Cardiac regeneration requires a complex cascade of events. Stem cell therapy and tissue engineering are newly emerging tools with promising potential for recover or replace of damaged cardiac tissue. There are many factors, most of them still no clarified, that limit the effectiveness of these treatments and their translation to the clinic. Cells should graft, survive and functionally integrate to the target organ in order to have a chance to restore its function. As in original tissues, a complex and well defined set of signals, many of them coming from the extracellular matrix, is required for normal cell physiology. Biomaterials science gives us important tools to build this extracellular matrix. Functionalized 3D systems can provide the correct environment and act as a delivery system for genes or gene products, guiding the therapeutic cells to the functional phenotype.

Mesothelial cells vs. skeletal myoblasts for myocardial infarction.

Cell transplantation for the regeneration of ischemic myocardium is limited by poor graft viability and low cell retention. Omental flaps in association with growth factors and cell sheets have recently been used to increase the vascularization of ischemic hearts. This experimental study was undertaken to evaluate the hemodynamic evolution and histological modifications of infarcted myocardium treated with mesothelial cells, and to compare the results with those of hearts treated with skeletal myoblasts. Myocardial infarction was created by surgical ligature of 2 coronary branches in 34 sheep; 6 died immediately due to ventricular fibrillation. Mesothelial cells were isolated from greater omentum, and myoblasts from skeletal muscle. After expanding the cells for 3 weeks, infarcted areas were treated with culture medium (control group), mesothelial cells, or myoblasts. After 3 months, echocardiographic studies showed significant limitation of ventricular dilatation and improved ejection fractions in both cell-treated groups compared to the controls. In the mesothelial cell group, histological studies showed significantly more angiogenesis and arteriogenesis than in the control and skeletal myoblast groups. Mesothelial cells might be useful for biological revascularization in patients with ischemic heart disease.

3-dimensional structures to enhance cell therapy and engineer contractile tissue.

Experimental studies in animals and recent human clinical trials have revealed the current limitations of cellular transplantation, which include poor cell survival, lack of cell engraftment, and poor differentiation. Evidence in animals suggests that use of a 3-dimensional scaffold may enhance cell therapy and engineer myocardial tissue by improving initial cell retention, survival, differentiation, and integration. Several scaffolds of synthetic or natural origin are under development. Until now, contractility has been demonstrated in vitro only in biological scaffolds prepared from decellularized organs or tissue, or in collagenic porous scaffold obtained by crosslinking collagen fibers. While contractility of a cellularized collagen construct is poor, it can be greatly enhanced by tumor basement membrane extract. Recent advances in biochemistry have shown improved cell-matrix interactions by coupling adhesion molecules to achieve an efficient and safe bioartificial myocardium with no tumoral component. Fixation of adhesion molecules may also be a way to enhance cell homing and/or differentiation to increase local angiogenesis. Whatever the clinically successful combination ultimately proves to be, it is likely that cell therapy will require providing a supportive biochemical, physical, and spatial environment that will allow the cells to optimally differentiate and integrate within the target myocardial tissue.

Predifferentiated adult stem cells and matrices for cardiac cell therapy.

Stem cell therapy is a major field of research worldwide, with increasing clinical application, especially in cardiovascular pathology. However, the best stem cell source and type with optimal safety for functional engraftment remains unclear. An intermediate cardiac precommitted phenotype expressing some of the key proteins of a mature cardiomyocyte would permit better integration into the cardiac environment. The predifferentiated cells would receive signals from the environment, thus achieving gradual and complete differentiation. In cell transplantation, survival and engraftment within the environment of the ischemic myocardium represents a challenge for all types of cells, regardless of their state of differentiation. An alternative strategy is to embed cells in a 3-dimensional structure replicating the extracellular matrix, which is crucial for full tissue restoration and prevention of ventricular remodeling. The clinical translation of cell therapy requires avoidance of potentially harmful drugs and cytokines, and rapid off-the-shelf availability of cells. The combination of predifferentiated cells with a functionalized scaffold, locally releasing molecules tailored to promote in-situ completion of differentiation and improve homing, survival, and function, could be an exciting approach that might circumvent the potential undesired effects of growth factor administration and improve tissue restoration.

Genesis of myocardial repair with cardiac progenitor cells and tissue engineering.

BACKGROUND: There is mounting evidence to suggest that the heart has regenerative potential in the event of myocardial injury. Recent studies have shown that a resident population of cardiac progenitor cells (CPCs) in the heart contains both vasculogenic and myogenic lineages. CPCs are able to migrate to the site of injury in the heart for participation in the healing process. The resident CPCs in the heart may also be activated through outside pharmacological intervention to promote their participation in the intrinsic repair process. In the light of these characteristics, CPCs provide a logical source for the heart cell therapy. During the regenerative cardiac process, stem cell niches (a specialised environment surrounding stem cells) provide crucial support needed for their maintenance. DISCUSSION: Compromised niche function may lead to the selection of stem cells that no longer depend on self-renewal factors produced by its environment. The objective of stem cell transplantation associated with tissue-engineered approaches is to create a new modality in the treatment of heart failure. The use of efficient scaffolds will aid to re-establish a favourable microenvironment for stem cell survival, multiplication, differentiation and function. Cardiac tissue engineering using natural and/or synthetic materials in this regard provides a novel possibility in cardiovascular therapeutics.

Cardiac bioassist: results of the French multicenter cardiomyoplasty study.

The French multicenter experience (6 centers) of dynamic cardiomyoplasty was analyzed for long-term survival and functional outcome, the most important endpoints in congestive heart failure therapy. Cardiomyoplasty was performed in 212 patients with symptoms of chronic heart failure despite maximal pharmacological therapy. The etiology was ischemic (48%), idiopathic (45%) or other (7%). Cardiomyoplasty was performed using the latissimus dorsi muscle which was electrostimulated after surgery. During follow-up, 88% of patients improved clinically. Hospital death occurred in 29 (14%) patients and was related to the severity of preoperative heart failure symptoms. Late mortality occurred in 99 patients due to heart failure (44%), sudden death (37%), or noncardiac causes (18%). Combined dynamic cardiomyoplasty and implantation of a cardiac rhythm management system was safely achieved in 22 patients, and 26 underwent heart transplantation for recurrent heart failure. Long-term functional improvements were observed in most patients, and the best outcome was achieved in those with isolated right ventricular failure. Dynamic cardiomyoplasty can be considered as a destination therapy or a mid- to long-term biological bridge to heart transplantation.

The forgotten driving forces in right heart failure: new concept and device.

BACKGROUND: Right heart failure is a frequent hemodynamic disturbance in pediatric cardiac patients. Besides inotropic and chronotropic drugs, fluid administration and inhaled nitric oxide, right ventricular mechanical assistance remains difficult to perform. A circulatory assist device adapted for the right heart biophysics and physiology might be more efficient. MATERIALS AND METHODS: We are developing a prototype of a non-invasive cardiac assist device (CAD) for neonates and pediatrics. It is based on a pulsatile suit device covering and affecting all territories of the right heart circuit. It will be tested in a neonatal animal model of right ventricular (RV) failure. Experimental models will be matched and compared with control and sham groups. Expected results would be immediate hemodynamic improvement due to synchronized diastolic reduction of stagnant venous capacitance, increasing preload and contractility. On long term, increased shear stress with changing intrathoracic pressure in a phasic way would improve and remodel the pulmonary circulation. Future studies will be focused on: hemodynamic, biochemistry, endothelium function test, and angiogenesis. COMMENTS: A non-invasive CAD guarantees better hemodynamics and endothelial function preservation with low morbidity and mortality. This is a physiological approach, cost-effective method, and particularly interesting in neonates and pediatrics with RV failure.

Association of electrostimulation with cell transplantation in ischemic heart disease.

BACKGROUND: Until now, cell therapy has constituted a passive therapeutic approach; the only effects seem to be related to the reduction of the myocardial fibrosis and the limitation of the adverse ventricular remodeling. Cardiac resynchronization therapy is indicated in patients with heart failure to correct conduction disorders associated with chronic systolic and diastolic dysfunction. The association of electrostimulation with cellular cardiomyoplasty could be a way to transform passive cell therapy into "dynamic cellular support." Electrostimulation of ventricles following skeletal myoblast implantation should induce the contraction of the transplanted cells and a higher expression of slow myosin, which is better adapted for chronic ventricular assistance. The purpose of this study is to evaluate myogenic cell transplantation in an ischemic heart model associated with cardiac resynchronization therapy. METHODS: Twenty two sheep were included. All animals underwent myocardial infarction by ligation of 2 coronary artery branches (distal left anterior descending artery and D2). After 4 weeks, autologous cultured myoblasts were injected in the infarcted areas with or without pacemaker implantation. Atrial synchronized biventricular pacing was performed using epicardial electrodes. Echocardiography was performed at 4 weeks (baseline) and 12 weeks after infarction. RESULTS: Echocardiography showed a significant improvement in ejection fraction and limitation of left ventricular dilatation in cell therapy with cardiac resynchronization therapy as compared with the other groups. Viable cells were identified in the infarcted areas. Differentiation of myoblasts into myotubes and enhanced expression of slow myosin heavy chain was observed in the electrostimulated group. Transplantation of cells with cardiac resynchronization therapy caused an increase in diastolic wall thickening in the infarcted zone relative to cells-only group and cardiac resynchronization therapy-only group. CONCLUSIONS: Biventricular pacing seems to induce synchronous contraction of transplanted myoblasts and the host myocardium, thus improving ventricular function. Electrostimulation was related with enhanced expression of slow myosin and the organization of myoblasts in myotubes, which are better adapted at performing cardiac work. Patients with heart failure presenting myocardial infarct scars and indication for cardiac resynchronization therapy might benefit from simultaneous cardiac pacing and cell therapy.

Cellular cardiac regenerative therapy in which patients?

Cell-based myocardial regenerative therapy is undergoing experimental and clinical trials in order to limit the consequences of decreased contractile function and compliance of damaged ventricles owing to ischemic and nonischemic myocardial diseases. A variety of myogenic and angiogenic cell types have been proposed, such as skeletal myoblasts, mononuclear and mesenchymal bone marrow cells, circulating blood-derived progenitors, adipose-derived stromal cells, induced pluripotent stem cells, umbilical cord cells, endometrial mesenchymal stem cells, adult testis pluripotent stem cells and embryonic cells. Current indications for stem cell therapy concern patients who have had a left- or right-ventricular infarction or idiopathic dilated cardiomyopathies. Other indications and potential applications include patients with diabetic cardiomyopathy, Chagas heart disease (American trypanosomiasis), ischemic mitral regurgitation, left ventricular noncompacted myocardium and pediatric cardiomyopathy. Suitable sources of cells for cardiac implant will depend on the types of diseases to be treated. For acute myocardial infarction, a cell that reduces myocardial necrosis and augments vascular blood flow will be desirable. For heart failure, cells that replace or promote myogenesis, reverse apoptopic mechanisms and reactivate dormant cell processes will be useful. It is important to note that stem cells are not an alternative to heart transplantation; selected patients should be in an early stage of heart failure as the goal of this regenerative approach is to avoid or delay organ transplantation. Since the cell niche provides crucial support needed for stem cell maintenance, the most interesting and realistic perspectives include the association of intramyocardial cell transplantation with tissue-engineered scaffolds and multisite cardiac pacing in order to transform a passive regenerative approach into a 'dynamic cellular support', a promising method for the creation of 'bioartificial myocardium'.