Understanding hESC-based Hematopoiesis for Therapeutic Benefit

Understanding hESC-based Hematopoiesis for Therapeutic Benefit

Funding Type: 
Comprehensive Grant
Grant Number: 
Award Value: 
Stem Cell Use: 
Embryonic Stem Cell
Public Abstract: 
Statement of Benefit to California: 
Progress Report: 

Year 1

We made good progress during the 08-09 funding period. We finished the critical work of screening 8 independent hESC lines for their ability to generate hematopoietic cells. This included 6 non-NIH-approved lines, studies that could only be performed through the innovative mechanism of CIRM funding, not through federal funding mechanisms. Interestingly, we found no meaningful differences among the lines, and are now able to focus on a single line. As a key part of achieving our goals, we generated a robust data set of miRNAs expressed in 3 different hESC lines and 4 independent human HSC samples. These data are now being scrutinized to identify possible miRNA candidates to test for their role in the development of HSCs from hESCs as well as the development/use of our more global miRNA screen. Regarding the larger miRNA screen, we now have a library that we think efficiently expresses miRNAs in hESCs, which was achieved by changing the promoter in our prior library. We are very optimistic about the new library; virus stocks are being made and will be tested in the near term. We also established and extensively characterized our mouse transplant model using human HSCs, and in the second half of the year performed many transplants of hESC-derived cells. To date we have not succeeded in identifying an engrafted HSC, but we have a number of ideas to try in year 3 to help us overcome this obstacle. We knew that this would be a huge hurdle, so while the lack of success in the transplants to date is not what we wished to have seen, it is not a major surprise. Nonetheless, we hope to overcome this problem with new ideas and studies that will be performed in funding year 3.

Year 2

We continue to focus on understanding the role of microRNAs in the development of hematopoietic stem cells from human embryonic stem cells. Progress is slow, but present. We now understand that cells we expected to have hematopoietic stem cell potential appear to have a greater potential for becoming cells that line the blood vessels (endothelial cells). We are now trying to comb through our microRNA data to see if it can inform us as to how to push such cells more towards hematopoietic stem cells. We do know that these two cell types are very closely linked during mammalian development. We are also investigating new ways to develop cells from embryonic stem cells to help our chance of finding/developing the elusive hematopoietic stem cell.

Year 3

Our focus in this proposal was to understand the role of miRNAs in the development of hematopoietic stem cells from human embryonic stem cells. Our work, and that of other over the past few years has demonstrated how difficult it is to generate hematopoietic stem cells from human embryonic stem cells. In fact, to date, nobody in the world has achieved that goal. However, along the way, we have come to realize that our system can help us identify and understand miRNAs involved in the critical developmental 'fork in the road' that leads to hematopoietic vs. cells that line blood vessels (endothelial cells). We worked in 2010-2011 to identify those miRNAs. Because of the difficulty in generating hematopoietic stem cells from human embryonic stem cells, we stepped back and worked to established better reagents for understanding hematopoietic stem cell development from human embryonic stem cells. To that end, we have used homologous recombination to directly insert a reporter gene into the genome of a human embryonic stem cell. We have been characterizing this cell line, and we hope that it will help advance the field of hematopoietic stem cell development from human embryonic stem cells, both to serve our needs and those of other embryonic stem cell researchers. Using similar sophisticated techniques, we have removed (targeted) from human embryonic stem cells a critical gene required for blood development to provide yet another tool to help us understand this process. We hope that these new reagents will further our understanding of hematopoietic development.

© 2013 California Institute for Regenerative Medicine