Early Translational I
Heart failure secondary to ischemic disease is a leading cause of morbidity and mortality in California and the developed world. As current therapies do little to rescue cardiac function, there is great interest in the promise of stem cell-based transplantation therapies to repair infarcted myocardium and reverse deterioration of cardiac function. However, there remain several bottlenecks to successful clinical application of stem cell transplantation in patients post myocardial infarction. Some bottlenecks which must be overcome are (1) to obtain a plentiful source of differentiated human ventricular cardiomyocytes (VCs); (2) to develop a method to deliver differentiated VCs to infarcted heart which allows cells to survive and integrate; and (3) to develop non-invasive quantitative imaging techniques to observe transplanted cells and their effects on heart function. To overcome these bottlenecks, we have assembled an interdisciplinary team of cardiovascular physician-scientists with expertise in animal models of cardiovascular disease, physiology, and cardiac inflammation; basic scientists studying cardiovascular disease, development, and stem cells; and bioengineers with expertise in tissue engineering, cardiac mechanics, and biomaterials for delivery of cells to infarcted myocardium. We have three experimental aims. Aim 1 will utilize new approaches for the differentiation and purification of human embryonic stem cell (hESC)-derived VCs. Success of these new methods will result in a high yield of purified VCs from hESCs which do not contain detectable pluripotent stem cells which might be tumorigenic. Aim 2 addresses the differentiation and yield of VCs transplanted into post-infarct heart by developing novel extracellular matrices that recapitulate the composition and physical properties of normal ventricular myocardium. Successful use of these optimized matrices to deliver hESC-derived VCs to post-infarct myocardium will result in restoration of 30% or more of of the infarct scar to functional ventricular muscle in a mouse myocardial infarction model. Aim 3 addresses the need for non-invasive methods to monitor the fate of transplanted cells and their physiological effects post infarct, and to address potential adverse teratogenic responses after transplantation. Successful completion of this aim will result in validation of new methods suitable for application in pre-clinical and clinical studies that can identify non-invasively cells with potential to develop tumors, the fate of differentiated transplanted VCs, and demonstrate sustained improvement in global and regional ventricular function following cell transplantation in post-infarct mice.
Statement of Benefit to California:
Atherosclerotic coronary artery disease continues to be the major cause of death in California and in the United States as a whole. The reduction, or complete cessation, of blood perfusion associated with subtotal or total coronary artery obstruction gives rise to myocardial dysfunction, potentially lethal arrhythmias, and ultimately cardiomyocyte death and regional infarction. Although a variety of medical, pharmacological and surgical interventions have been developed that attempt to inhibit adverse cardiac remodeling and ensuing heart failure, there remains a pressing need for a new strategy to repair damaged myocardium. Either partial repair, or outright regeneration, of myocardial cellular constituents, most importantly the cardiomyocytes, by cell transplantation provides for the promise of this repair. Our experiments will lead to a new plentiful source of appropriately differentiated human cardiomyocytes for use in cell transplant, a new delivery vehicle that promotes a high yield of surviving differentiated cardiomyocytes in infarcted muscle; and new non-invasive techniques for defining the fate of implanted cells and their impact on ventricular remodeling and function.
The applicant seeks to develop a number of technologies in preclinical models of ischemic cardiac disease that will ultimately facilitate the use of human embryonic stem cells (hESCs) for cardiac cell transplantation in patients. The application addresses some of the considerable bottlenecks to be overcome before hESC-based cell therapy for cardiac disease becomes a reality. This proposal addresses three translational problems by proposing methods to generate pure and plentiful ventricular cardiac myocytes using reporters and cell surface markers, to improve delivery and survival in mouse infarct models by incorporating ECM derivatives and small molecules, and to develop non-invasive imaging approaches to follow the transplanted cells. The application places emphasis on scalable and cost-effective strategies. The applicant has chosen important bottlenecks to address, and if successful, the project could have significant impact on developing strategies for hESC-derived cell transplants that have thus far not been very effective in experimental models. Ongoing clinical trials using adult stem cells show there is, at least, short-term evidence that stem cells and progenitors may benefit patients with myocardial infarction. Reviewers believed that the proposed biomatrix adjunct to cell therapy was promising but noted that the particular choice is not translatable, as the proposed biomatrix contains xeno-components. Another potential weakness is that the study is to be performed with an outcome oriented approach and is not hypothesis-driven; the latter approach was viewed as better suited to this stage of research. While new information may result from the proposed research, significant bottlenecks are unlikely to be overcome completely by the data generated in the proposed studies. For example, if there is a noteworthy improvement in the purification of ventricular cardiac myocytes using the transgenic reporter, it is unclear how this result will be translated to trials when such a reporter cannot be used. In this sense, one reviewer commented that the project appeared to comprise a strong basic science proposal rather than a bottleneck solution for translational research. Nonetheless, the application addressed significant problems, and the suggested approaches are based on solid scientific rationale. Reviewers expressed serious concerns about the project’s feasibility and identified numerous problems. For example, reviewers were not convinced that use of gadolinium-labeled immunomicelles was a viable approach, as relevant preliminary data were not included, this agent has a very low sensitivity for imaging, it is unclear how the micelles will taken up and cleared by transplanted cells, and the consumption of micelles by macrophages may obscure relevant localization data. The imaging studies rely heavily on a collaborator, and IP issues may arise as the collaborator has developed a novel method for atherosclerosis imaging. Reviewers also expressed skepticism and concern with the proposed differentiation procedures. A major concern was the likelihood that the protocol would result in a mixture of atrial and ventricular cells, not the pure population desired. Another concern was that the aims of the proposal are interdependent, so the failure of one will doom the entire project. Despite their many reservations about the application, reviewers praised the strong group of researchers assembled for the project. The applicant has an excellent record of accomplishment and is highly productive. Concern was expressed that the PI is already above 100% commitment, and so, it is not clear how time will be allotted to execute this project. The research environment is excellent and all the resources and equipment are in place. The deficiency in imaging expertise is supplemented by collaboration with a research group that is known for its advances in atherosclerosis imaging. In summary, the proposal is submitted by a highly respected and resourceful applicant and research team. Though this application addresses critical bottlenecks in translating a cell-based therapy into the clinic, fundamental components of the experimental design were deficient. These concerns severely limit prospects for the proposal’s feasibility, significantly lessening the potential impact of the research.