The process of new blood vessel formation is essential for repair of damaged or diseased tissues and organs. Regeneration of the heart is an important goal in modern medicine. Ideally, new therapies should give patients long-term normalization of the heart. Embryonic stem cells could be induced to form heart muscle cells and cells that line the blood vessels known as endothelial cells. Here we propose to use a natural hormone-like protein known as leptin, to stimulate embryonic stem cells to form cardiac muscle and endothelial cells. In our laboratory, we have done early experiments using organized stem cell clusters known as embryoid bodies treated with leptin. Our early studies showed that leptin can induce the formation of primitive blood vessels and contractile heart muscle cells. Based on our findings, we propose that leptin is important to stimulate human embryonic stem cells to form heart muscle and endothelial cells. Furthermore, we also think that the presence of primitive blood vessels in embryoid bodies can facilitate or be required for the formation of mature cardiac muscle cells. It is possible that blood vessel formation in response to leptin (or similar proteins) supplies a blood vessel network providing an appropriate environment where stem cells can then become heart muscle cells. Therefore, we propose three objectives: (I) To characterize the effect of leptin treatment on embryoid bodies cultures; (II)To optimize the conditions under which leptin (and possibly other related substances) induce formation of cells from the cardiovascular system thus increasing the number of endothelial and heart muscle cells in the cultures; and (III)To test the function of the endothelial and heart muscle cells formed in the cultures by using them in an experimental animal model of heart attack (myocardial infarction). We will also study the molecular aspects of the response to leptin. In addition, we will use specific markers to ascertain the endothelial and cardiac muscle character of the cells formed. Finally, we will separate the endothelial and heart muscle cells from the cultures and then use them to study if heart muscle cells benefit from the presence of endothelial cells. These cells will also be given to mice of the myocardial infarction model to prove their repair potential in the injured heart. To see if leptin can always induce formation of endothelial and heart muscle cells, we will use four different human embryonic stem cell lines, including a new cell line. The use of a new line has advantages to meet the strict regulatory requirements of the Food and Drug Administration (FDA) for therapeutic use in humans. Knowledge derived from the proposed studies will contribute to understand how human embryonic stem cells become mature functional cells. Moreover, these studies may result in optimized experimental conditions leading to the large scale production of heart muscle and endothelial cells for therapeutic applications.
Statement of Benefit to California:
Heart disease is the number one cause of death in California and in the United States. In California alone, heart disease accounts for 39% of all deaths and it is a major cause of disability and poor quality of life. The economic impact of heart disease is astonishing. In California, the health care costs and loss of productivity due to heart disease is approximately $30 billion per year. The yearly cost of coronary heart disease alone is at least $15 billion in the State. These expenditures account for one tenth of the total cost burden in the entire nation. In addition, type II diabetes and obesity are well-known risk factors for coronary heart disease. These two diseases are increasing at alarming rates every year and consequently contributing to the rising incidence of heart disease. The people of California made an important choice by voting to pass Proposition 71. Embryonic stem cells are likely to be unique tools in the treatment of genetic and neurological diseases. However, their potential use for effective therapeutic repair and regeneration of the heart could be life-saving for millions of individuals suffering from heart disease. In this regard, our research proposal seeks not only to advance our current understanding of the coordinate development of a complex tissue from stem cells, but most importantly, to focus on the translational aspect of this knowledge inasmuch as it provides a means to solve a major medical challenge, namely the repair of injured or damaged heart tissue with cells derived from human embryonic stem cells. In the long term, effective therapies to repair the myocardium, coupled with a comprehensive package of preventive health policies instituted statewide, would undoubtedly translate into significant savings to the State. The magnitude of such savings in heart disease costs alone is likely to surpass or at least return the investment made by California when Proposition 71 was passed.