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RS1-00167-1: Characterization of Immune Responses in Human Embryonic Stem Cells

Recommendation: Not recommended for funding

Public Abstract (provided by applicant)

Human embryonic stem cells (hESC) provide a promising future therapeutic approach for replacement of diseased or damaged tissue. This proposal addresses the development of therapeutic strategies that can specifically aid two different neurological disorders. Multiple sclerosis (MS) is a chronic condition which affects the brain and spinal cord. In patients with this condition, the myelin sheaths that cover nerve fibers are erroneously destroyed by the body’s own immune system. In spinal cord injuries, the resulting inflammation causes severe damage to myelin-producing cells. The goal of this proposal is to determine if stem cells, at various phases of differentiation to myelin-producing cells, have characteristics which could not only replenish the lost myelin, but also confer a healing microenvironment. The focus will be on two beneficial immune-based processes. First specific aim will determine molecular signaling pathways involved in innate immune responses in hESC and establish if these processes provide a microenvironment conducive to tissue regeneration. Innate-immune responses have been shown to underlie tissue repair gene expression by dying cells. Our preliminary experiments have identified that components of this pathway are present in human embryonic stem cells (hESC), particularly at the later phases of differentiation to mature myelin-producing cells. Levels of factors involved in this process will be evaluated in hESC. To further establish the potential of the hESC to create a regenerative microenvironment for damaged cells, inserts of stressed and dying cells will be co-cultured with hESC. Cell viability, with or without co-exposure to hESC, will be determined using a commercially available cell cytotoxicity assay. The hypothesis to be tested is that hESC can provide a restorative microenvironment for stressed or dying cells and this involves up-regulation of innate immune responses. In the second specific aim, we will evaluate whether hESC can down regulate harmful inflammatory immune responses by a process used by fetal cells to escape the maternal immune response. This process is called ‘immune tolerance. To determine if hESC have the ability to provide an immune privileged microenvironment (similar to the fetus) components of this response will be determined in hESC. The hypothesis to be tested is that hESC can subvert destructive immune responses by processes similar to those that underlie immune tolerance. The long term objective of these studies is to design oligodendrocyte populations derived from hESC that provide an ideal microenvironment for promotion of cell survival, regeneration, and immune tolerance. These can eventually be used therapeutically in chronic demyelinating diseases such as MS or acute traumatic spinal cord injuries with minimal chances of host rejection.

Statement of Benefit to California (provided by applicant)

The proposed research will benefit California and its citizens in several ways. First, the results may aid in the design of effective therapies based on hESC that can benefit patients with multiple sclerosis or spinal cord injury. For the citizens of California who are suffering from these disorders, the development of these stem cell-based therapies will alleviate some of the pain and hardships associated with their condition. Second, successful development of stem-cell based therapies will lighten the economic burden for the state of California, which provides health care services to its citizens. Third, the results gained from the studies proposed may lead to intellectual property rights which can be used as a foundation for creating new biotechnology companies. This will not only create jobs but will also contribute to the economic growth of the state of California.

Review

SYNOPSIS: This Principal Investigator (PI) proposes to determine whether and how human embryonic stem cell (hESC) implants can provide a “healing microenvironment”. This proposal is designed to test whether oligodendrocytes derived from hESC can influence the pathologic microenvironment into which they are transplanted based on their effects on the immune response. In the first part of the work, the applicant will explore innate immune responses in hESC at different stages of differentiation. The contributions of a particular molecular signaling pathway will be measured, and the ability of hESC to create a regenerative microenvironment will be tested using neurons pre-exposed to a toxic pro-inflammatory stimulus. Secondly, the PI will ascertain whether hESC are “immune-tolerant” by looking for specific cytokines to test the hypothesis that hESC may subvert destructive immune responses by processes similar to those that induce immune tolerance. The “long-term objective” of the studies is to design oligodendrocyte populations derived from hESC that not only remyelinate but provide “an ideal microenvironment” for promoting cell survival, regeneration, and immune tolerance.

SIGNIFICANCE AND INNOVATION: This is an innovative and original proposal that presents interesting and novel ideas. The ability of cells, in this case oligodendrocytes, that are derived from hESC to both remyelinate axons and influence the microenvironment in a positive way is intriguing. The proposed experiments might also help address other questions that are presently being asked about the possibility of transplanted neural stem cells influencing the inflammatory background into which they are transplanted and the immune response.

STRENGTHS: This is a thoughtful proposal which asks interesting questions and which has some preliminary data to support the hypotheses. The subject of immune effects of hESC cells is very important, and the proposed experiments are feasible.

WEAKNESSES: The experimental plan may not work in part as the pro-inflammatory stimulus to be used is unlikely to damage neurons because neurons do not usually express the molecular factors which are essential for its activity. This is a serious and significant technical concern. Also, the fact that cytokine release from hESC was undetectable by Enzyme-Linked ImmunoSorbent Assays (ELISA) is concerning. More importantly, the proposal contains few definitive experiments that would test some of the novel ideas proposed. It is of interest to determine what cytokines are produced by hESC but few details are provided concerning how the hESC will be prepared. The applicant does not seem to have much experience with cell culture and particularly stem cells. There are great ideas presented, but more details of the experiments should be given since it is not clear that the ideas will be tested rigorously. The PI might consider using known compounds that will damage neurons. In addition, before moving to protein-based assays for cytokines, which is perhaps ever more difficult, the applicant could begin by determining expression levels.

DISCUSSION: There was no discussion further following the reviewers’ comments.

The following Working Group members had a conflict of interest with this application and were therefore recused from participating in review of, discussion of, and voting on the application:

• None