Heart failure is the most important cardiovascular health problem worldwide. It is a common end result of multiple diseases such as hypertension, coronary artery disease, diabetes and obesity. In the United States alone, it afflicts 5 million patients and a substantially larger number of asymptomatic subjects have an evidence of left ventricular dysfunction. In addition, as discussed above, at least 60-70 million people suffer from diseases that render them susceptible to development of HF. The disease imposes an economic burden of more than 25 billion dollars every year. The clinical syndrome of heart failure is characterized by relentless progression of disease and in spite of significant medical advances the prognosis of advanced HF has not improved. Before this cardiovascular scourge evolves into an epidemic, we need to start a two-pronged strategy; identify predisposed early to prevent the progression of disease, and develop newer methodology to salvage the failing myocardium. Newer strategies for empowering failing myocardium include human embryonic stem cells (hESC) injections in the heart muscle so that these cells could proliferate to assume the characteristics of heart muscle cells. However, we propose that we should move away from the orthodox attempts of transforming hESC to heart muscle before they are seeded into the myocyte-deficient regions. Instead, we would focus primarily on revitalizing withered heart muscle cells.
In heart failure, the inexorable decline of LV function, of many pathogenetic mechanisms, has been attributed to an interrupted suicidal process (called apoptosis). During this process, the power houses of the muscle (called mitochondria) are depleted of intermediates involved in energy production. Hence heart failure is considered energy-deficient state. We propose that revitalization of mitochondria is necessary to provide energy to failing heart muscle cells and that HESC can be used as the source of new mitochondria. Such mitochondrial transfer to failing cells may result in partial alleviation of heart failure. We propose that preparation of extra-nuclear part of human embryonic stem (hES) cells and its delivery to withered myocytes will replenish these cells. The hybrid cells thus will be formed in the heart muscle with new mitochondria from the stem cells.
Statement of Benefit to California:
Heart failure is the most important cardiovascular health problem worldwide. Various cardiovascular diseases such as hypertension, coronary artery disease, diabetes and obesity, eventually lead to heart failure. Approximately 5 million patients suffer from heart failure in US alone and a substantially larger number of asymptomatic subjects have an evidence of left ventricular dysfunction. In addition, as discussed above, at least 60-70 million people suffer from diseases that render them susceptible to development of HF. The disease imposes an economic burden of more than 25 billion dollars every year. California has the lowest death adjusted death rate for heart failure compared to other states but yet carries one of the largest heart failure loads in the country (based on the ICD-9; 428.0-428.9). The clinical syndrome of heart failure is characterized by relentless progression of disease and in spite of significant medical advances the prognosis of advanced HF has not improved. We need to develop newer methodology to salvage the failing myocardium.
Recently some revolutionary newer strategies have been proposed for empowering failing myocardium such as myocardial injection of human embryonic stem cells (hESC) so that these cells could proliferate to assume the characteristics of heart muscle cells. However, we propose that we should move away from the orthodox attempts of transforming hESC to heart muscle before they are seeded. Instead, we would focus primarily on revitalizing withered heart muscle cells, by mere mitochondrial transfer from the stem cells.
California is the pioneering state that allows the jusdicious use of embryonic stem cells for research. This project promises not only the new hope for heart failure but may also allow a new paradigm in the management of various chronic degenerative diseases wherein energy production is limited. It is expected that if the proof of principle is demonstrated by the proposed experiment, such a technology would be immediately translated into the clinical experiment. Use of embryonic stem cells without the nucleus would preclude the potential devastating malignant transformations. Management of chronic debilitating diseases with virtually no side effects would result in quantitative and qualitative improvement in health. This should also offer an improvement in effective manpower within the state.
The PI proposes work directed at re-energizing a failing or acutely damaged myocardium using transfer of mitochondria from hESCs to the heart in a rodent model. The specific aims are (1) to create enucleated hESC or hESC cytoplasts as mitochondrial donors; (2) to prepare two cell lines H9C2 (which is a cardiomyocyte line) and C2C12 (which is NOT a cardiomyocyte line) as mitochondrial recipients; (3) to optimize conditions for cytoplast transfer to rodent myocardiocytes in culture; (4) to create a post-infarct model for cytoplast transfer; and (5) to develop optical imaging techniques for identification of the transferred fluorescent mitochondria.
INNOVATION AND SIGNIFICANCE: The signficance of the proposal lies in its long term goal of laying the groundwork for human ES cell-derived, cell-based therapy for heart disease. The strategy is based on the concept that enhancing the mitochondrial pool of existing cardiac cells with mitochondria derived from human ES cells might prove beneficial. This is a very unusual concept. The idea of re-energizing mitochondria of acutely or chronically failing heart muscle has appeal, but is independent of hESC biology.
STRENGTHS: The strength of the proposal is in the PI's experience with rodent models of heart failure and specialized imaging techniques that could be applied. The environment for studies of mitochondrial related disorders and diseases at UCI is surperb.
WEAKNESSES: The PI is an expert in the role of apoptosis in heart disease and the failing heart, and in imaging techniques to monitor apoptosis in the heart, but not a mitochondria expert. Doug Wallace, a leading expert in mitochondria at UCI, is listed as a collaborator but without a letter of support.
Unfortunately the PI has picked exactly the wrong cell to use as a mitochondrial donor. Undifferentiated hESCs have a paucity of mitochondria, but with differentiation they undergo mitochondrial biogenesis. Many other cells with richer mitochondrial supplies would be better suited to the experiment.
Why is aim 2 necessary in the light of aim 3?
Aim 4 already has been done in the lab. Aim 5 seems to be part of already funded work, optimization is not unique to this proposal.
It is also surprising that the C2C12 line is called a cardiomyocyte line. It is most certainly not a cardiomyocyte line, but rather a skeletal muscle stem cell line.
The citations on creation of cytoplasts have no information about the efficiency of such protocols, giving very little confidence, given the poor source of mitochondria, that these studies will yield any useful information.
1) The use of human ES cells is not compelling in this proposal as other donor cells could easily be used
2) The fundamental assumption is unproven and there is a quite a bit of circumstantial evidence to suggest that mitochondria are generators or cell death signals and free radicals that can cause cardiac injury instead of preventing it.
3) Ideal cell for the cytoplast transfer is still unclear, effects of adult stem cells in heart repair have been modest at best, and in several cased negative.
4) Efficency of cytoplast transfer invivo may become an issue.