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RN1-00532-1: Identification of hESC-mediated molecular mechanism that positively regulates the regenerative capacity of post-natal tissues
Recommendation: Recommended for funding
Scientific Score: 83
First Year Funds Requested: $449,317
Total Funds Requested: $2,246,020
Public Abstract (provided by applicant)
The tissue regenerative capacity deteriorates with age in animals and in humans, leading to the loss of organ function, which is well exemplified in skeletal muscle, but is poorly understood in molecular terms. Our recent work uncovered that factors produced by human embryonic stem cells have a unique ability to enhance the regenerative responses of organ stem cells, dedicated for tissue maintenance and repair, be they young or old and located in young or old organism. This proposal seeks to understand the molecular mechanism of this novel phenomenon, which is two-fold important: in expanding our knowledge of the stem cell biology and in developing entirely novel embryonic stem cell-based therapeutic applications that do not have the side-effects associated with immune rejection. Importantly, this uncovered enhancement of tissue repair is conserved between mice and humans , which allows use of an animal model for identifying these therapeutically-relevant human factors and greatly facilitates the pre-clinical data collection, interpretation and translation to clinic.
The main goals of this Proposal are to identify the embryonic pro-regenerative factors, to understand their mode of action and to validate their efficiency for enhancing and rejuvenating repair of injured and pathological tissues in an animal model. Notably, using the infrastructure of [REDACTED] the data generated by this work will be quickly disseminated to [REDACTED] clinicians and will be applied through Clinical Affiliates Program for clinical studies and human trials.
Identifying these embryonic stem cell-produced pro-regenerative factors will help counter the loss of tissue maintenance and repair in the old, generally and not just in skeletal muscle, and will be of immediate therapeutic value without a need for “humanization” and without the risk of immune rejection. Additionally, for muscle wasting caused by diabetes and immobility, and in Duchenne/Becker and Limb-Girdle myopathies, these factors will boost the performance of satellite cells struggling to repair continuous myofiber deterioration, thus countering degeneration and improving organ function.
Statement of Benefit to California (provided by applicant)
Degenerative diseases in which the bodies capacity to regenerate new tissue can no longer keep up with tissue death is a major problem for society in general and for State of California in particular. The lack of tissue repair that eventually leads to the loss of organ function is undeniable and devastating trait of aging that causes many degenerative disorders, exemplified by Parkinson’s, Alzheimer’s and muscle atrophy. Therefore, Californians with life-long skills, expertise and invaluable knowledge can no longer contribute to society and do not enjoy life fully. In recent years biologists and clinicians realized that practical therapies would only emerge when the balance between the regenerative and the degenerative processes were properly understood in biomedical terms. Comprehensively, the proposed research seeks to uncover novel evolutionary conserved molecular regulation that is mediated by human embryonic stem cells and promotes regenerative capacity of postnatal stem cells (likely, generally and not just in skeletal muscle). Qualified scientists from underrepresented minorities will be involved with this academic and translational stem cell project, hence allowing expand the representation of all Californians in the cutting-edge biomedical research. This proposal describes steps to rejuvenate stem cell responses in the old and to rescue tissue repair in people suffering from debilitating degenerative diseases. The outcomes of this work will insure that the health prognosis is significantly improved for older Californians, especially those afflicted with degenerative disorders, and that the results of these studies are translated as rapidly as possible to the clinical setting where their practical benefit can be fully utilized. Thus this work seeks not only to improve the quality of life for our older citizens, but also to reduce the health-cost associated with treating currently incurable degenerative diseases. The developing therapies will be immediately applicable for all Californians irregardless of their ethnic background, gender or age.
Review
SYNOPSIS: This project focuses on the repair of injured and pathological muscle in animal models, and on a potential pro-regenerative effect derived from human embryonic stem cells (hESCs). Specifically, the principal investigator (PI) is interested in the role that hESCs may play in promoting adult stem cell differentiation. Adult stem cells are inhibited from differentiating by the tissue in which they reside, but hESCs can overcome this inhibition. The applicant has shown that factors isolated from hESC cultures can overcome this inhibition, and the proposed research will explore these findings in a systematic manner. The particular targets to be investigated are muscle and the muscle satellite stem cells. The applicant will determine the effects of any identified factors on genetic models of muscular degenerative diseases.
STRENGTHS AND WEAKNESSES OF THE RESEARCH PLAN: This is an intriguing hypothesis which could have very important implications for our understanding of the repair and maintenance of adult tissues. The lack of adequate tissue repair leading to degeneration and loss of organ function is a devastating trait of aging. Why older tissues do not engage in repair as do younger embryonic tissues is an important question that this project attempts to address. The possibilities include among others that aged tissues have a reduced number of adult organ-specific or broad pluripotent stem cells; that aged stem cells have acquired intrinsic dysfunction; or that the microenvironment in the aging organ (due to age or through injury response mechanisms) inhibits or blocks the repair by functionally normal stem cells. In the context of this project, it is also important to think about the possibility that repair mechanisms and their responses to aging may be different in different organ systems. Novel preliminary findings by this investigator demonstrate the possibility that there is a dysfunctional aged environment which prevents stem cells from reaching their developmental potential, and that this may be overcome by a protein factor from hESCs. Ultimately hESCs are being used in this proposal as a means to discover a protein factor that could be administered to patients to rejuvenate old muscle.
Overall, this is a well-written proposal from a first-rate investigator at a top institution who plans to follow up on a novel and potentially important finding. The experiments are well-planed and systematic, and propose to test novel ideas on hESC properties and their roles in tissue regeneration. The results could have wide-ranging implications in human regenerative medicine. The proposal is focused on bioactive molecules and could potentially lead to novel discoveries. Therapies based on proven bioactive small molecules are clearly those most readily adopted by manufacturers for delivery to large numbers of patients. There is a high degree of enthusiasm for experiments aimed at characterizing hESC-produced factors that can regulate the regenerative responses of muscle stem cells, and for testing these factors in animal models of muscular dystrophy.
There are few weaknesses. Based on the preliminary data presented, it is not entirely clear that the effect the applicant is observing is a pro-regenerative activity of undifferentiated hESCs in vitro; an alternative interpretation of the data is that there is a factor produced by another cell type and differentiated hESCS that inhibits satellite muscle differentiation. The proposal suffers somewhat from the absence of a clear mechanistic hypothesis with regard to precisely which of a short list of factors might be responsible. Given that this is a short list already, it may be worth testing growth factors empirically rather than using the shotgun approach of gene expression profiling proposed. In that sense, if one or two key signaling molecules can be identified, it is not clear that the proposed gene expression profiling experiments (which are costly) would be entirely necessary. A relative weakness is the lack of emphasis of functional improvement of muscle strength and agility and the reliance on phenotypic changes and muscle fiber numbers. There might be some concern that the murine muscular dystrophy models will be an allogeneic immunocompetent transplant model, in which case rejection of transplanted cells may confound their results. It would be interesting to see if such hESC-derived pro-regenerative ability could impact other adult stem cell systems. This is not considered or proposed.
A potential caveat for the purification of the identified factors is – will there be enough material for the proposed studies, or will this require a large scale-up of hESC cultures and is the investigator prepared to do this? Purification of factors from hESC cultures, in and of itself, will likely take two to three years to complete but is an important aim. Challenges exist with the proposed confirmation of identified candidate molecules, and these methods would need significant validation. There is no preliminary data or experience of the investigator to support this work and it may be more difficult than expected.
Despite these considerations, reviewers felt that this is a first rate proposal from a first rate candidate and institution, with tremendous mentorship and institutional support.
QUALIFICATIONS AND POTENTIAL OF THE PRINCIPAL INVESTIGATOR: Reviewers agreed that this is an extremely well-qualified candidate with a superlative track record, trained and doing research at top-flight academic institutions. The applicant has been involved in stem cell research for many years. S/he is a faculty mentor for the CIRM Training Grant at his/her institution, and is heavily involved in student teaching and in the committee for the embryonic stem cell core facility committee.
The outstanding investigator has an excellent publication record and has published important papers in high impact journals including Science, Cell, and Nature. S/he has existing NIH and other extramural funding for muscle stem cell research. The investigator has recruited several strong collaborators, and several reviewers noted that there is high quality support in the areas newest to the PI. There is an excellent mentoring plan in the institution and the applicant will have guidance from eminent scientists.
The applicant’s career development plan is well outlined and s/he intends to develop new skills and expertise in interdisciplinary approaches to stem cell research, including tissue engineering, material science, and synthetic biology. S/he also intends to develop additional expertise in translation to clinical trials, although this is fairly premature with regard to this particular project.
A reviewer commented that the PI has significant knowledge in the field of research. The postdoctoral worker recruited to the project appears to have some hES cell experience, but there may be need for additional support on adaptation of the hES cells to feeder-free culture.
In progressing research from ageing to bioengineering, there is a clear pathway for the PI to establish a role as a high quality leader. The PI has solid and growing publications in the area of the proposal and an increasing presence in the stem cell field. The PI also has a good level of base funding to build upon.
INSTITUTIONAL COMMITMENT TO PRINCIPAL INVESTIGATOR: There is a good level of institutional commitment and support for this applicant, and significant developments are planned to enhance stem cell science locally. The host institute’s Dean has assured support “during the period of the grant,” which is supportive but does not imply significant ongoing development of the position. Regular meetings with the Dean are planned and there are very good lab facilities for the basic work.
It is clear that the investigator and associated colleagues are in a rich and nurturing environment for development of preclinical research. There is commitment from local technology platforms and facilities, with attached letters confirming this support, which is impressive. Further professor posts and a stem cell core facility will be moved on site, with local collaborators to support on new developments. The institute has a stem cell centre and plans a core stem cell facility.
There are certainly some potential near-term applications of this proposal that could be tested in large animal preclinical models if confirmed for muscle stem cells. On this front, there seems to be interaction through a collaborating institution with clinical investigators at other top tier research facilities, which could provide an avenue for further preclinical development of potential therapies derived from these or future findings. One reviewer commented that it is unfortunate, however, that the clinical links are not in place already, although a program for clinical affiliates is intended.
DISCUSSION: Reviewers felt that this was one of the better projects in this round of applications. It is a strong proposal scientifically with novel preliminary data, an interesting hypothesis, and potential clinical applicability. The concept that factors from hESCs can improve differentiation of muscle stem cells/satellite cells in older tissue is intriguing. Experiments to characterize hESC-derived factors that can regulate the regenerative responses of muscle stem cells, and for testing these factors in genetic models of degeneration, are particularly strong. Reviewers agreed that the experiments proposed will help identify molecules with potential for clinical use. The PI is excellent, with a strong publication record, a good biongineering team, and good collaborations. The institution and the PI’s career development plan are very good.
Few weaknesses were identified in this application, and most of them were considered minor. Gene profiling experiments were considered less strong, as reviewers felt that gene expression profiling to compare undifferentiated and differentiated hESCs will be expensive and might yield too much data to be useful, and the follow-up experiments will be difficult to interpret. One reviewer was concerned that the PI proposes experiments in a single cell line. Finally, reviewers commented that identified factors would not be useful for treating diseases caused by genetic defects in muscle.
Overall, reviewers were enthusiastic about this proposal based on the strength of the PI and his/her commitment to stem cell research, the novel preliminary results, and the interesting scientific hypothesis.
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:
- Bonner-Weir, Susan
- Wagers, Professor Amy
- Orkin, Stuart