Stem cell biology and its applications to cell-based therapies, since its inception 30 years ago, has been hindered by the immunological considerations of rejection of non-autologous cells in patients, as well as by ethical concerns. The generation of pluripotent cells from a patient’s own somatic cells has therefore been the holy grail of regenerative medicine. A variety of techniques have been used to attempt nuclear ‘reprogramming’ including transfer of somatic nuclei into oocytes (SCNT) that led to cloning of the sheep ‘Dolly’. A recent breakthrough was the demonstration by Yamanaka and colleagues that the introduction of only four molecular factors into skin fibroblasts could generate induced pluripotent cells (iPS cells), with potential similar to ES cells in their ability to generate all of the germ layers. iPS cells have an unparalled potential for cell based therapies as they overcome the immunological and ethical concerns as well as provide a means to obtain cellular disease models from patients as invaluable tools for disease characterization and drug screening. However, before their clinical applications can be realized, it is of utmost importance (a) to characterize reprogramming of iPS cells at a molecular level and (b) to use this information to increase the efficiency of iPS cell generation. Our proposed studies take advantage of a novel cell-fusion based system that we have developed, in which reprogramming is initiated rapidly and efficiently. Such studies are of fundamental importance in increasing our understanding of how to direct and maintain cell fate. In addition, they will benefit the production of iPS cells and advance the entire field of regenerative medicine.
The state of California is the front-runner in stem cell research, having gathered not only private investments, as demonstrated by the numerous biotechnology companies that are developing innovative tools, but also extensive public funds via Prop 71, that allows the state, through CIRM to sponsor stem cell research in public and private institutions. In order to preserve its leadership position and encourage research on stem cells, the CIRM is calling for research proposals that could lead to significant breakthroughs or the development of technologies useful for studying stem cells in order to improve human health. We propose here to develop a platform that will enhance our understanding of the basic biology of stem cells and establish a molecular understanding of the phenomenon of iPS cell generation, a breakthrough that has taken the stem cell world by storm in the last few years. California is fortunate to be the home for the laboratory of Shinya Yamanaka, who pioneered this technique. Yet, the study of pluripotency is a field in its infancy and a better understanding of iPS cell biology, especially of the molecular events that allow a skin cell from any human being to be turned into an iPS cell (akin to an embryonic stem cell in its potential) is greatly needed before the potential of iPS cells can be fully realized. Our proposed studies are based on an innovative use of cell fusion to study reprogramming as a complimentary approach to iPS cells with the aim of enhancing our understanding of the process of nuclear reprogramming to iPS cells and making their derivation much more efficient. These studies will contribute substantially to all types of stem cell research, including human embryonic stem cells and induced pluripotent stem cells advancing the entire field of regenerative medicine.
The goal of this proposal is to elucidate the molecular events that underlie reprogramming of adult somatic cells towards a stem cell fate and to use this knowledge to develop improved methods for inducing pluripotency in adult cells. To achieve these ends, the applicants propose a novel cell fusion strategy in which reprogramming is initiated rapidly and efficiently. By using state of the art genomic profiling techniques, the applicants propose to monitor the earliest changes that take place and identify the critical factors that lead to reprogramming of the human transcriptome. For the second aim, the applicants will use loss of function experiments to validate the role of the factors that were identified in Aim 1. Finally, the applicants propose to test these candidates for their ability to enhance and accelerate the derivation of induced pluripotent cells (iPSC).
The reviewers were extremely enthusiastic about the potential for this effort to advance the field of stem cell biology, praising both the novelty and the utility of the fusion-based approach. Several key advantages were discussed including rapid access to the earliest of reprogramming events and a more efficient and synchronous environment by which specific pluripotency mechanisms could be uncovered. While one reviewer was not convinced that any newly identified factors would offer more than an incremental impact on reprogramming efficiency, all agreed that this is nonetheless a worthwhile endeavor that could further our mechanistic understanding of the reprogramming process. The impact of such findings could ultimately lead to new approaches and potentially expedite the translation of iPSC-based technologies to the clinic.
The reviewers considered the research plan to be logical, straightforward and based on sound rationale. The preliminary data was praised for supporting both the feasibility of the fusion approach as well as the transcriptome profiling methodologies upon which the success of this entire effort hinges. Some minor criticisms were raised, including the lack of preliminary data to support the usefulness of secondary iPSC lines for validating the effects of reprogramming candidates. In addition, several reviewers would have appreciated clarification as to how potential hits would be prioritized for subsequent investigation. While additional information about the partially reprogrammed iPSC would have been useful, the reviewers were satisfied that the overall approach and experimental design were technically and practically achievable.
Reviewers uniformly praised the PI as a pioneer in the field with a uniquely qualifying expertise and a demonstrated level of commitment to this project. In addition to an outstanding track record, the PI has assembled a highly qualified team of collaborators. The research environment was characterized as outstanding and supportive.
Overall, the reviewers were uniformly enthusiastic about this proposal. They appreciated its novel approach, feasible strategy, and strongly supportive preliminary data. Despite some minor concerns about the experimental design, the reviewers were optimistic that this effort would lead to insights that could substantially impact the field of stem cell biology.