Pluripotent Stem CellńBased Therapy for Heart Disease
Five million people in the U.S. suffer with heart failure, resulting in ~60,000 deaths/year at a cost of $30 billion/year. Heart failure occurs when the heart is damaged and becomes unable to meet the demands placed on it. Unlike other organs, the heart is unable to fully repair itself after injury. One of the common causes for the development of heart damage is a heart attack. After a myocardial infarction (heart attack), irreversible loss of contracting heart muscle cells occurs, resulting in scar formation and subsequently heart failure. Current therapies designed to treat heart attack patients in the acute setting include medical therapies and catheter-based technologies that aim to open the blocked coronary arteries with the hope of salvaging as much of the jeopardized heart muscle cells as possible.
Unfortunately, despite advances over the past 2 decades, it is rarely possible to rescue the at-risk heart muscle cells from some degree of irreversible injury and death. Attention has turned to new methods of treating heart attack and heart failure patients in both the acute and chronic settings after their event. Heart transplantation remains the ultimate approach to treating end-stage heart failure patients but this therapy is invasive, costly, some patients are not candidates for transplantation given their other co-morbidities, and most importantly, there are not enough organs for transplanting the increasing number of patients who need this therapy. As such, newer therapies are needed to treat the millions of patients with debilitating heart conditions. Recently, it has been discovered that stem cells may hold therapeutic potential for these patients. Experimental studies in animals have revealed encouraging results when pluripotent stem cells are introduced into the heart around areas of myocardial infarction. These therapies appear to result in improvement in the contractile function of the heart.
However, numerous questions remain unanswered concerning the use of pluripotent stem cells as therapy for patients with heart attack and heart failure. Human embryonic stem (ES) cells and induced pluripotent stem (iPS) cells grow and divide indefinitely while maintaining the potential to develop into many tissues of the body, including heart muscle. They provide an unprecedented opportunity to both study human heart muscle in culture in the laboratory, and advance the possibility of their use in therapy for damaged heart muscle. We have developed methods for identifying and isolating specific types of human ES and iPS cells, stimulating them to become human heart muscle cells, and delivering these into the hearts of rodents that have had a heart attack. This research will refine and advance such approaches in small and large animals, develop clinical grade cells for use, and ultimately initiate clinical trials for patients suffering from heart disease.
Dr. Srivastava presents a lecture at UCSF on the genetics of heart disease
CIRM Shared Human Embryonic Stem Cell Core Laboratory
The CIRM Shared Human Embryonic Stem Cell Core Laboratory will provide shared research facilities for use by California scientists. This laboratory will be hosted by a research institution focused on basic research into three of the most important medical problems of modern times: cardiovascular disease, AIDS, and neurodegenerative disorders. Each of these research areas addresses promising targets for regenerative medicine. We propose to develop a laboratory (1108 sq ft) for hESC tissue culture with specialized microscopy, and an animal holding and procedure space (500 sq ft) for in vivo pre-clinical studies of hESCs in mouse models of disease. The proposed laboratory will also help to train students from a nearby college be become laboratory technicians. This facility will contain advanced equipment for analyses of hESCs and complement existing space and incorporate hESC work provided by other core laboratories such as the genomics and flow cytometry cores that serve a broad community of researchers.
The host institution is renowned for the quality and administration of its extensive core facilities. Highly productive cores have always been at the heart of this institutionís culture and this continues to be a priority. Five years ago, the host institution founded an embryonic stem cell core, which allows investigators not familiar with ESC research to obtain training, expertise and knowledge regarding embryoid bodies and ESC differentiation. As a result, two-thirds of the current investigators have incorporated some aspect of stem cell research in their portfolio. The host institution is also located in close proximity to a major biomedical university, so that all stem cell services are being coordinated to provide the best possible array of services to all stem cell investigators.
The research interests of our investigators that are related to stem cells can be grouped into three areas: cardiovascular development and disease, neurodegeneration and repair, and mechanisms that control the genetic stability of the cells while they divide and develop. This research involves the creation of genetically altered ESCs that require maintenance, expansion, and characterization. To aid in the analysis of the cellular phenotypes, we propose to use advanced high-content microscopy equipment. Several leading laboratories that apply this technology to basic cell biological analysis are close to Gladstone. An important next step will be to examine the behavior, survival, and interactions of hESCs once they have been implanted into mice. Visualization of the cells in live animals will be greatly enhanced by the proposed imagining instrument that will allow us to examine living cells within animals by light signals transmitted from the implanted cells. This program represents a comprehensive basic approach to how stem cells develop into other kinds of cells and will form the foundation for future preclinical studies.
MicroRNA Regulation of Cardiomyocyte Differentiation from Human Embryonic Stem Cells
Regenerative therapies could be particularly beneficial for heart disease, which is the leading killer of adults in the U.S, and is responsible for the 5 million Americans with insufficient cardiac function. At the other end of the age spectrum, malformations of the heart involving abnormal cell lineage or morphogenetic decisions are the leading noninfectious cause of death in children. Unfortunately, since adult heart cells cannot multiply after birth, the heart has almost no regenerative capacity after injury or in response to malformations. Deciphering the secrets of heart formation might lead to novel approaches to repair or regenerate damaged heart muscle using embryonic stem cells (ESCs) and progenitor cells. Our research is focused on determining what causes ESCs to specialize into cells that belong to the mesodermal, or middle, layer of an embryo, which develops into blood, muscle, and bone, among other cells, with a specific focus on cues that stimulate cardiac and skeletal muscle formation. Small RNA molecules called microRNAs have emerged as an elegant and novel mechanism nature uses to titrate dosage of critical proteins by regulating the flow of genetic information as it is translated into proteins. microRNAs are active dynamically and specifically in developing cardiac and skeletal muscle during muscle formation. In mice and flies, microRNAs regulate the balance of muscle formation vs. expansion of progenitor cells. We have evidence that microRNAs can control mouse embryonic stem cells (mESCs) and can promote formation of mesoderm and inhibit formation of other cell types such as brain or gut cells. This may be true in human ESCs also. However, NIH-approved human ESC (hESC) lines are contaminated with mouse feeder cells, are difficult to disperse into single cells and do not grow robustly enough to generate homogeneous pools of genetically altered cells. This has made it difficult to generate homogenous population of cells that could be used for discovery and future potential therapeutic applications. The aims of this grant will use non-NIH approved lines to meet these objectives and are not fundable by the NIH. We hypothesize that specific microRNAs influence early mesoderm commitment and later steps of myogenic expansion or formation from hESCs by controlling other key regulatory events. To test this hypothesis, we propose three specific aims: 1) Determine if microRNAs can promote mesoderm formation and subsequent decisions of cardiac muscle proliferation or differentiation in hESCs; 2) Determine if specific microRNAs repress other lineages in hESCs; 3) Determine the mechanisms by which microRNAs regulate mesoderm commitment, muscle differentiation and proliferation. The tools and understanding developed here will ultimately be used to generate myocytes either directly or through subsequent screens for drugs targeted at the pathways discovered by the proposed work.
