Funding opportunities

Role of the microenvironment in human iPS and NSC fate and tumorigenesis

Funding Type: 
Basic Biology II
Grant Number: 
RB2-01496
Principle Investigator: 
Funds requested: 
$1 284 921
Funding Recommendations: 
Recommended
Grant approved: 
Yes
Public Abstract: 
Multipotent Neural Stem Cells (NSC) can be derived from adult central nervous system (CNS) tissue, embryonic stem cells (ESC), or iPSC and provide a partially committed cell population that has not exhibited evidence of tumorigenesis after long term CNS transplantation. Transplantation of NSC from these different sources has been shown by multiple investigators in different CNS injury and disease paradigms to promote recovery or ameliorate disease. Additionally, both {REDACTED} groups have shown that human NSCs transplanted in the subacute period after spinal cord injury promote functional recovery. While the role of the host immune response has been considered in the context of immune-rejection, predominantly regarding the T-cell response, the consequence of an ongoing inflammatory response within the context of the tissue microenvironment for cell fate, migration, and integration/efficacy has been largely overlooked. Critically, the tumorigeneis, fate, migration, and integration/repair potential of a stem cell is driven by: 1) the intrinsic properties of cell programming, e.g., the type and source of cell / means used to derive the cell, and maintenance/differentiation of the cell in vitro; and 2) the extrinsic factors the cell encounters. Variations in the intrinsic properties of the cell may affect the potential of that cell for uncontrolled proliferation or the response of the cell to extrinsic factors that it later encounters, defining its fate, migration, and integration/repair potential. The {REDACTED} group has demonstrated that iPS-derived neurospheres (iPS-NS) exhibit a surprisingly large degree of variation in tumorigenesis potential after CNS transplantation, which is correlated with tissue source as well as differentiation and NS forming capacity. Moreover, the intrinsic properties of hNSC populations derived from different cell sources have not been broadly characterized; in fact, {REDACTED} has published the first data in the field demonstrating the differences in fate and integration/repair potential between primary and secondary neurospheres generated via in vitro differentiation of mouse or human ESC and iPSC. In parallel, {REDACTED} has shown profound differences in the response of NSC derived from human tissue versus hESC to extrinsic signals. Together, these data suggest that both characterization of the intrinsic properties of NSCs derived from different sources is essential for our understanding of the basic biology of these cells. Investigation of molecules and signaling pathways directing hNSC fate choices in the injured CNS microenvironment will yield new insight into the mechanisms of fate and migration decisions in these cell populations.
Statement of Benefit to California: 
Multipotent Neural Stem Cells (NSC) can be derived from adult central nervous system (CNS) tissue, embryonic stem cells (ESC), or induced pluripotent cells (iPSC) and provide a partially committed cell population that has not exhibited evidence of tumorigenesis after long term CNS transplantation. Transplantation of NSC from these different sources has been shown by multiple investigators in different CNS injury and disease paradigms to promote recovery or ameliorate disease. Accordingly, stem cell based therapeutics such as these have the potential to treat a variety of traumatic, congenital, and acquired human conditions. However, while much progress has been made, translational research with human stem cell populations will remain limited by the progress of the fundamental understanding of the basic biology of these cells. The {REDACTED} group has pioneered understanding the critical role of timing in considering cell transplantation therapies. More recently, this group has focused on the neural induction of mouse- and human-derived iPSC and tested the potential of these cell populations for spinal cord injury treatment in animal models. {REDACTED} has established the NOD-scid mouse as a model for experimental neurotransplantation for xenograft studies, characterizing the relationship between transplant timing, engraftment outcome, cell fate, host remyelination, and functional recovery. Recently, this group has focused on how the innate inflammatory response influences cell fate and migration. In this collaborative proposal, researchers from California and Japan propose to combine their expertise to characterize and investigate some of the most fundamental aspects of the intrinsic properties of, and extrinsic factors influencing, human induced pluripotent (hiPSC) and human embryonic (hESC) stem cells, pooling knowledge and expertise in stem cell and animal model paradigms. The experiments proposed investigate the basic cellular and molecular mechanisms underlying the role of the host environment in stem cell fate regulation, and the relationship between reprogramming and tumorigenic/fate potential of hiPS-NSC in vitro and after transplantation, and key to this collaborative effort, the interface of these two aspects of basic stem cell biology. Critically, this international collaboration combines the expertise of two of the most advanced laboratories in translational stem cell biology to address several key unresolved questions in the control of cell fate, and will promote sharing of resources, data, and techniques between these labs to advance the field. Ultimately, the collaborative work proposed may permit the development of strategies to refine cellular reprogramming techniques, alter in vitro differentiation strategies, or manipulate the microenvironment to maximize the window for potential stem cell-based neurotherapeutics.
Review Summary: 
EXECUTIVE SUMMARY This proposal examines how the stem cell source and inflammatory microenvironment influence the repair potential of human neural stem cells (hNSCs) in spinal cord injury (SCI). The applicant presents data suggesting that the starting stem cell line as well as the timing of implantation can affect hNSC differentiation, tumorigenicity and the extent of functional recovery from SCI. In Aim 1, the applicant proposes to perform extensive characterization and comparison of hNSCs derived from multiple induced pluripotent stem cell (iPSC) and human embryonic stem cell (hESC) lines in terms of their differentiation potential, epigenetic status and tumorigenicity following transplantation. In Aim 2, the applicant will examine the effects of inflammatory cells on these hNSCs in vitro, including effects on their capacity to differentiate, migrate and proliferate. Finally, in Aim 3, the applicant proposes to assess the role of the inflammatory microenvironment in the differentiation, engraftment, migration and tumorigenicity of transplanted hNSC in vivo, and on hNSC-mediated functional recovery following SCI in an animal model. The reviewers found this proposal to be innovative and highly significant. They agreed that it addresses an important question of how cell-intrinsic and -extrinsic factors function together to determine the fate and efficacy of transplanted cells. Reviewers found the rationale for the proposed studies to be well-developed and well-supported. They also felt that the proposal could have a major impact on the development of treatments for SCI and other central nervous system injuries with NSCs. Reviewers agreed that the proposal’s experimental design is sound and its specific aims are logical and achievable. They appreciated the strong and compelling preliminary data, particularly data suggesting that the time period between injury and hNSC transplantation affects cell fate and functional recovery. Reviewers did raise a number of minor concerns regarding the research plan. They commented that there is little rationale provided for the selection of cell lines, especially given published data from the collaborating laboratory which compared the tumorigenicity of NSCs derived from different iPSC lines. With regard to Aim 2, reviewers questioned the ability of in vitro studies to model the in vivo inflammatory environment. They also suggested the applicant consider the roles of resident astrocytes or microglia, in addition to infiltrating leukocytes, in the inflammatory response. Reviewers further noted that a recent paper from Kigerl, et al. describes two distinct types of macrophages in the injured spinal cord, a finding that should be considered by the applicant when modeling macrophage response in vitro. One reviewer noted that while inflammatory cells produce a plethora of soluble factors, the applicant proposes to study only four, without providing a rationale for the choices. This reviewer suggested first confirming that hNSCs express or upregulate receptors to these proposed factors. Another reviewer recommended isotype control antibodies for all neutralizing antibody experiments. Reviewers were enthusiastic about the principal investigator (PI) and assembled research team. They commented that the PI has been productive with multiple papers published in relevant subject areas. They praised the Funding Partner PI and co-investigators, and were impressed by the synergistic and collaborative nature of the proposal. Reviewers noted that the PI and co-investigator have the appropriate expertise and are dedicating significant effort to the project. The Partner PI’s team is highly experienced in neuronal differentiation and includes a world leader in this field. Overall, the reviewers agreed that this innovative proposal has the potential to have a major impact on the development of hNSC transplantation therapies. They raised a number of concerns about the experimental design, but the high quality of the assembled research team convinced them of the project’s feasibility.
Conflicts: 

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