Basic Biology IV
Blood stem cells have already been used in the clinic to treat patients suffering from blood cancers or inherited blood disorders. However, only a fraction of patients can be treated as there are not enough compatible bone marrow donors, and it has not been possible to create more blood stem cells in culture by using expansion protocols, or by generating them from undifferentiated pluripotent stem cells. The limited success in creating blood stem cells in culture stems from our incomplete understanding of the regulatory mechanisms that protect their unique properties. This is especially challenging in human, as there is insufficient knowledge of how to identify human blood stem cells, and as there have not been good experimental models to manipulate human blood stem cells or their niche cells for mechanistic studies. We have overcome these bottlenecks and identified a human HSC surface protein GPI80 that allows purification of blood stem cells during human fetal development from multiple blood forming tissues. Our data also indicate that GPI80 is necessary for blood stem cell self-renewal and interaction with their niche cells. With these findings and the tools we have established, we are in a unique position to define the key pathways active in GPI80+ blood stem cells that maintain their unique properties. Identification of these factors will ultimately help us create more blood stem cells in culture for therapeutic applications.
Statement of Benefit to California:
The goal of this proposal is to identify regulatory molecules that could be used in the future to help expand hematopoietic stem cells in culture, or even to generate them from pluripotent stem cells. Thus, the results of this work could help develop better treatment for patients in California suffering from various blood diseases such as leukemia and inherited blood/immune disorders. This study may also lead to the development of commercial applications for molecules that could be used for future clinical HSC culture protocols, and thereby this work may boost the biotech industry in California. This work will also serve as an outstanding training tool for students and post-doctoral fellows in California who aim to learn human hematopoietic stem cell manipulation and state of the art assays to investigate their function and molecular regulation. This training will provide an outstanding foundation for a career in either academia or biotech industry.
The goal of the proposed research is to identify factors and understand mechanisms involved in the expansion of hematopoietic stem cells (HSCs) in culture. In preliminary research, the applicant identified a surface protein on human HSCs, GPI80, that serves as a marker for transplantable HSCs and is required for HSC maintenance. Proposed studies will focus on the role of this protein. The first specific aim will be to further examine the effects of altered expression of GPI80 on HSC function in vivo and identify cellular pathways affected by changes in the protein’s level. The second specific aim is to identify and validate components functioning downstream of GPI80 to facilitate HSC maintenance. The third aim is to identify stromal (cell niche) factors that support HSC expansion. Significance and Innovation - The proposed study could provide new insights into HSC-niche interactions and lead to the identification of novel factors that facilitate HSC expansion. - Reviewers expressed doubts that the results of the proposed studies, which are focused on fetal liver cells, would be applicable to adult HSCs. - Although the focus on GPI80 was recognized as novel, the central importance of this component for HSC maintenance and expansion was unclear. - One reviewer questioned the project’s rationale and suggested that the need for expansion of autologous HSCs for therapeutic purposes is fairly limited, although another reviewer considered HSC expansion to be a key clinical problem. Feasibility and Experimental Design - The application includes sufficient and compelling preliminary data that support the proposed investigation. - The proposed experimental approaches are straightforward, build upon the preliminary data and are designed to yield useful results. - The applicant did not address possible off-target effects in knock-down or over-expression experiments or provide adequate discussion of alternative plans. - Reviewers were concerned that there was little indication about how work on new components identified in the study would be prioritized, and it may result in an unfocused and open-ended project. Principal Investigator (PI) and Research Team - The PI is an excellent, established investigator with much expertise HSC biology. - The proposed research team has sufficient experience and expertise to perform the proposed research. Responsiveness to the RFA - The proposed research is fully responsive to the RFA.