Every therapy has toxic and therapeutic windows, and defining the side effects of any new therapeutic modality is the first order of business in the development of a treatment. With transformative therapies such as cell-based approaches, treatment side effects can be unpredictable and unanticipated. In some cases, experimental data raise serious concerns that must be appropriately managed. In the face of the promise and enthusiasm for cell-based therapy for heart disease, results from rodent experiments have consistently raised the specter of a dreaded side effect– can the use of stem cells lead to cancer, either directly or through promotion of existing early stage neoplasms?
Mesenchymal stem cells (MSCs) are a multipotent immunotolerant cell source that can be readily expanded into therapeutic quantities from a variety of tissues such as the bone marrow, cord blood and fat, and as such their use in cell-based therapeutic strategies holds great promise.1 With regard to heart disease, accumulating preclinical2-11 and clinical studies12-15 demonstrate that MSCs-transplantation may be salutary for both acute myocardial infarction and cardiomyopathy with an acceptable risk profile.
The translational development of cell-based therapy has required rigorous large animal experimentation, recognizing inhered limitations to rodent experimentation. In this context, more than 500 large animals (swine, canine and sheep) have been tested to assess the safety and efficacy of MSC therapeutics for treating heart disease with the results demonstrating that MSC transplantation is a safe and durable approach that appears more effective than bone marrow mononuclear cells.16 Importantly, large animal work provides a phenotyping opportunity not available in rodents, and rigorous cardiac magnetic resonance imaging (CMR) and histological analysis in porcine hearts supported the regenerative effects subsequently demonstrated in the adult human heart.12, 15 The mechanism of action appears multifaceted, involving direct differentiation of MSCs into cardiomyocytes and vessels,2, 11 but to a greater extent stimulation of the hearts’ own cardiac stem cells to form new cardiac muscle.11