Cell transplantation in non-ischemic dilated cardiomyopathy. A novel biological approach for ventricular restoration

Cardiovascular surgery for realization of regenerative medicine

Regenerative medicine is emerging as a new approach to the treatment of severe cardiovascular diseases that are resistant to conventional therapies. Although the type of cell transplanted (e.g., pluripotent stem cells, bone marrow-derived stem cells, skeletal myoblasts, or cardiac stem cells) influences the outcome of stem cell transplantation, the method of transplantation is also important, as the efficiency of engraftment after simple needle injection is poor. Scaffold-free cell sheet transplantation technology is one of the most promising methods in this regard. Although the results of clinical trials of stem cell therapy have been marginal to date, further elucidation of the actual mechanisms of cardiac repair following cell therapy would enhance the potential for full-scale implementation of stem cell therapy. In addition to stem cell therapy, the field of cardiovascular regenerative medicine includes interspecific chimera technology, drug delivery systems using biodegradable materials, and gene therapy. Integration of these new modalities with conventional therapies will be important to realize the goal of cardiovascular regenerative medicine tailored to the condition of each individual patient. Cardiovascular surgery would be an excellent means of carrying out this strategy and could potentially resolve the health problems of the increasing number of advanced cardiovascular patients. Herein, we review the recent basic and clinical research associated with the realization of regenerative medicine in the field of cardiovascular surgery.

Paracrine effects of cell transplantation: modifying ventricular remodeling in the failing heart

Structural ventricular remodeling determines the clinical progression of heart failure and has emerged as an important target for the development of novel medical and surgical therapeutic strategies. Cell transplantation is an innovative biologic therapy that may restore myocardial structure and function in failing hearts. With current forms of cell transplant therapy, true myocardial regeneration has been limited. However, cell transplantation can predictably limit maladaptive ventricular remodeling through multiple synergistic paracrine mechanisms. Some of the paracrine factors released by transplanted cells have been defined. These paracrine signals may provide beneficial effects by stimulating angiogenesis, limiting matrix disruption, and preventing apoptosis. In addition, cell transplantation may induce mobilization and homing of endogenous repair cells to injured myocardium through paracrine signals. Paracrine mediators released from transplanted cells work through multiple, diverse, and interrelated molecular pathways resulting in synergistic effects on the remodeling process. Although true myocardial regeneration remains the ultimate goal of cell therapy, the anti-remodeling abilities of cell transplantation can be harnessed to complement our contemporary surgical approaches for patients with myocardial injury at risk of congestive heart failure.

Cellular cardiomyoplasty for myocardial regeneration

The evolving challenge of managing patients with congestive heart failure is the need to develop new therapeutic strategies. The cellular, molecular, and genetic approaches investigated aim to reinforce the weak, failing heart muscle while restoring its functional potential. This approach is principally cellular therapy (i.e. cellular cardiomyoplasty), the preferred therapeutic choice because of its clinical applicability and regenerative capacity. Different stem cells: bone marrow cells, skeletal and smooth muscle cells, vascular endothelial cells, mesothelial cells, adipose tissue stroma cells, dental stem cells, and embryonic and fetal cells, have been proposed for regenerative medicine and biology. Stem cell mobilization with G-CSF cytokine was also proposed as a single therapy for myocardial infarction. We investigated the association of cell therapy with electrostimulation (dynamic cellular cardiomyoplasty), the use of autologous human serum for cell cultures, and a new catheter for simultaneous infarct detection and cell delivery. Our team conducted cell-based myogenic and angiogenic clinical trials for chronic ischemic heart disease. Cellular cardiomyoplasty constitutes a new approach for myocardial regeneration; the ultimate goal is to avoid the progression of ventricular remodeling and heart failure for patients presenting with ischemic and non-ischemic cardiomyopathies.

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.

Restoration and regeneration of failing myocardium with cell transplantation and tissue engineering

Cell transplantation and the creation of bioengineered cardiovascular tissues are novel biologic approaches to restore and regenerate failing myocardium. These rapidly evolving therapies may complement and enhance other mechanical and surgical interventions for patients with congestive heart failure, providing cardiac surgeons with a wider range of treatments for patients at risk of congestive heart failure. Proof-of-concept studies have been performed in several experimental animal models of human cardiovascular disease, such as myocardial infarction and dilated cardiomyopathy. Although the exact mechanisms are unclear, cell transplantation restores cardiac function and limits ventricular dilatation. Clinical cell transplantation has been performed in a limited number of patients with encouraging preliminary results. In contrast, bioengineered muscle grafting is largely experimental but offers the promise of myocardial regeneration by replacing irreversibly damaged myocardium with healthy autologous tissue to facilitate more extensive ventricular remodeling surgery.