Integrin ligation in human ESC (hESC) proliferation and fate determination

Funding Type: 
SEED Grant
Grant Number: 
ICOC Funds Committed: 
Stem Cell Use: 
Embryonic Stem Cell
Public Abstract: 
The potential of human embryonic stem cells (hESC) to be used to treat devastating diseases has raised a significant level of expectation among the scientific community and patient groups as well. hESC are pluripotent cells, that is these cells have the potential to differentiate to any cell type and to self-renew. hESC cells are presently viewed as promising cell sources not only for disease treatment, but for regenerative medicine. Nonetheless, there are ethical and political questions about the use of human embryos in medical research that have made international news headlines and shifted some of the focus from the promise of the research to the legal battles that are presently being waged. As the field of hESC research matures, it is being realized that many areas of investigation need greater emphasis to develop and understand the true potential of hESC and their capacity to be used in disease treatment and regenerative medicine. Importantly, integrins are a class of functional proteins found on the cell surface of hESC, and many other cell as well, that are involved in cell-cell and cell-surrounding tissue (the extracellular matrix, ECM) communication that control important cellular process including cell division and cell shape determination. The integrin class of proteins has been greatly understudied in the hESC field. Integrins are closely linked to processes involved in cell migration and differentiation. hESC need to be characterized in terms of their integrin content and the role of integrins in hESC differentiation and pathway determination and this is the focus of the present application. We have been studying integrins on cancer cells for a number of years and now wish to apply our expertise to the study of hESC integrins and their interactions with the ECM. We have used proteins called disintegrins, which are integrin antagonists, to block integrin function. We will utilize the disintegrins and several other techniques designed to block integrin function or to block their intracellular production. These techniques will enable us to determine the importance of integrins to hESC proliferation and fate determination. Further, our studies will help to develop procedures that could control hESC cell fate determination. Thus, by appropriate blockage of integrin pathways, we could alter the fate of hESC by forcing the cells to differentiate, for example, into a muscle cell or a brain cell. As a specific illustration we will induce the generation of blood vessels by hESC using different ECM matrices and determine integrin involvement in this process by selective use of integrin antagonists. Previous work with mouse ESC showed an integrin-antagonist of a specific integrin known to be important to the process of vessel formation, inhibited this process. Thus, integrins apparently play important roles in cell fate determination and we seek to be able to selectively control integrin function, thereby controlling cell fate determination.
Statement of Benefit to California: 
A significant number of Californians have family members suffering from serious medical conditions that can potentially be addressed by stem cell therapies. These conditions include cancer, diabetes, heart disease, Alzheimer’s, Parkinson’s, spinal cord injuries, along with nearly 100 other diseases and conditions. Recent advances in medicine have addressed the abilities of stem cells to potentially treat these conditions. Californians deserve the best possible medical care, and the federal government’s reluctance to fund the vital hESC research limits advances in this important area of medical science. The research proposed here would provide the medical community with mechanisms to control cell differentiation and force the hESC along the desired differentiation pathway. This would represent a significant breakthrough for cell based therapies for a specific disease or for regenerative medicine based procedures. The research proposed in this application is directed to identifying cell surface proteins that are involved in hESC propagation and differentiation; the studies we propose should lead to an understanding of the role of integrins in hESC proliferation and fate determination. Since this may ultimately lead to the ability to control cell fate by turning off or antagonizing a specific subset of integrins, we may be able to direct cell fate determination, that is control hESC differentiation. The integrin receptors on hESC surfaces provide adhesive ability and migration potential to the cells, as well as being involved in a number of important signal transduction pathways. When the ability of these surface proteins to bind to external factors is modulated, there is a dramatic effect on cell proliferation and differentiation potential. The ability to modulate these proteins and thereby control or alter the fate of hESC would be a powerful tool in using stem cells as therapeutics for people in the State of California with any of the diseases enumerated above. The ability to modulate integrin function would be most beneficial when advancing therapies for specific diseases or developing regenerative medicine procedures, and would provide physicians the capacity to specifically control the differentiation fate of hESC being employed for these procedures.
Progress Report: 
  • A central goal of our CIRM SEED proposal was to use innovative unbiased approaches to discover novel proteins that turn genes on or off in pluripotent stem cells. An understanding of what are these proteins that act as genetic switches and how they function is of significant importance to efforts to use pluripotent stem cells to model disease states in the lab or to provide a source of cells of therapeutic interest for transplantation. We have been successful in our efforts, in that we identified a novel protein that appears to play an unexpected role in the regulation of gene activity in pluripotent stem cells. In addition, we have identified another protein that is critical to maintain the DNA of pluripotent stem cells is a state accessible to other proteins. Our research is therefore providing an integrated picture of what are the genetic switches that turn genes on or off in pluripotent stem cells, what genes do they regulate, and how is their access to DNA regulated. Some of our results have recently been published, while other research is ongoing. In parallel, we have been very successful at transferring expertise to the biotechnology sector in California. In particular, two highly qualified lab members accepted senior scientist positions at top biotechnology firms in California (iPierian and Genentech).
  • A central goal of our CIRM SEED proposal was to use innovative approaches to discover genes that control human embryonic stem cells, with the idea that this knowledge may lead to improved methods for growth and/or differentiation of human pluripotent stem cells in a clinical setting. In the past year we have continued to make significant progress on these efforts. We have found a factor that acts to turn other genes on or off and is active in embryonic stem cells. We have put a considerable amount of effort into optimizing methods to identify exactly what genes this factor controls. Our results show that this factor directly regulates pluripotency-associated genes. This is remarkable, since this factor had not to date been implicated in the regulation of pluripotency. These results put us in a position to characterize the function of this factor in embryonic stem cells in greater detail. In addition, we are applying knowledge gained from our studies to develop methods to enhance the ease with which human pluripotent stem cells are propagated. Human pluripotent stem cells, including embryonic stem cells and induced pluripotent stem cells, are notoriously more difficult to grow than their mouse counterparts, and this has significantly hampered the ability to use existing human pluripotent stem cells to model disease. We have developed conditions that facilitate the propagation of human pluripotent stem cells in a state that resembles mouse ES cells, where they are easier to propagate and grow more rapidly. These findings, while preliminary, suggest that we have the opportunity to explore a transition of human pluripotent stem cells to a state that is easier to culture and manipulate genetically. Thus, the CIRM SEED award has allowed us to discover a novel regulator of pluripotency genes, and to develop conditions that may lead to improved culture and manipulation of human pluripotent stem cells.

© 2013 California Institute for Regenerative Medicine