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RN1-00555-1: Building Cardiac Tissue from Stem Cells
Recommendation: Not recommended for funding
Public Abstract (provided by applicant)
Congestive heart failure afflicts 4.8 million people, with 400,000 new cases each year. Myocardial infarction (MI), also known as a “heart attack”, leads to a loss of cardiac tissue and impairment of left ventricular function. Because the heart does not contain a significant number of multiplying stem, precursor, or reserve cells, it is unable to effectively heal itself after injury and the heart tissue eventually becomes scar tissue. The subsequent changes in the workload of the heart may, if the scar is large enough, deteriorate further leading to congestive heart failure.
Many stem cell strategies are being explored for the regeneration of heart tissue, however; full cardiac tissue repair will only become possible when two critical areas of tissue regeneration are addressed: 1) the generation of a sustainable, purified source of functional cardiac progenitors and 2) employment of cell delivery methods leading to functional integration with host tissue. This proposal will explore both of these 2 critical areas towards the development of a living cardiac patch material that will enable the regeneration of scarred hearts.
Statement of Benefit to California (provided by applicant)
The research proposed here could result in new techniques and methodology for the differentiation of stem cell-derived cardiomyocytes and delivery methods optimal for therapeutic repair of scarred heart tissue after a heart attack. The citizens of California could benefit from this research in three ways. The most significant impact would be in the potential potential for new medical therapies to treat a large medical problem. The second benefit is in the potential for these technologies to bring new business ventures to the state of California. The third benefit is the education of the students involved in this study, especially in the [REDACTED].
Review
SYNOPSIS: This is an interesting project to develop strategies for cardiac regeneration following myocardial infarction (MI), with a goal of maximizing functional implantation and overcoming the scarring effect which can lead to heart failure. The idea is to integrate the generation of functional cardiac progenitors from embryonic stem cells (ESC) with the development of effective cell delivery mechanisms into the host tissue. The goal of the proposed work is to make cardiac patches starting from stem cells of three species. There are two aims:
1) Use a novel microarray approach to evaluate a limited number of biochemical and electrical stimulations to control and maximize the directed differentiation of hESC to functional cardiomyocytes (CM).
2) To develop a delivery vehicle in an infarct model for comparison of direct injection of cells with cells delivered in a natural extracellular matrix material. A large animal infarct model will be used, with or without endothelial cells.
STRENGTHS AND WEAKNESSES OF THE RESEARCH PLAN: The stated goals of this application are quite exciting: utilization of a combination of molecular and electrical signals to direct differentiation of hESCs into cardiac lineages, and the implantation of hESC-derived cells using a native tissue matrix to achieve cardiac repair. The aims are logical for achieving these goals. The first aim is to develop methodologies for derivation of functional cardiomyocytes by controlled and high-yield differentiation of hESCs. The second aim is to develop delivery vehicles for implantation of cardiomyocytes, either alone or in combination with endothelial cells.
The significance of deriving bona fide cardiomyocytes from hESCs and demonstrating their utility in an animal model of cardiac repair would be high. In particular, a cardiac patch could in principle provide major improvements in cell retention, increased viability, and enhanced integration with the host. The utilization of combined molecular and physical signaling for cardiac differentiation of hESCs is also novel. It is also a good idea to test the benefit of including functional endothelium. However, the experimental design, as explained below, does not give sufficient confidence that the stated research goals will be met, and that the potential significance and innovation will in fact be achieved. It is unclear what will be done, why and how. In summary, the proposal has a very high significance but is very poorly written and suffers from many scientific shortcomings, some of which are listed below.
All three reviewers had major concerns that embryonic cells from three species are used, and that it is totally unclear why these choices were made and how will methods be translated from one cell source to another. All three reviewers were skeptical that the protocols for derivation of cardiomyocytes from one species can be optimized as stated by extension of established protocols for vascular cells from another species.
The microarray platform for in vitro studies is neither described nor referenced, and one reviewer could not understand the specific design features that enable medium perfusion and electrical stimulation. There are statements that the PI has the capability to perfuse and stimulate cell cultures long term, but these statements are not documented in any way (published work, preliminary studies, detailed design).
A list of molecular agents includes six different factors to test for impact on differentiation to CM, but their selection, roles, concentrations and combinations are not specified. Electrical signals are not specified either, and the whole body of literature on electrical stimulation of individual cells and three-dimensional tissues is ignored.
The second aim describes an infarct model that will be carried out by the co-PI. The PI states that homologous ESC-CM (cardiomyocytes derived from ESC) will be used for this purpose, yet there is no indication these cells are available, how these cells will be derived, or whether ESC-CM are being tested at all in the first aim. One reviewer commented that they would like to see a discussion of how stem cells from this species differ from stem cells of the other two species under investigation. At another point the PI indicates that endothelial cells derived from ESCs from the other two species will be used, but it is not clear how either relates to the infarct model, and what compatibility issues should be considered. Overall, the transplant model studies were not clearly described, and priorities for translating the results from Aim1 with the transplant model were not discussed.
In summary, the research design is poorly developed, and reflects insufficient understanding of cardiac differentiation. Also, preliminary studies are limited to mouse vascular cells and the large animal model of cardiac repair, and do not establish the feasibility of the proposed work.
QUALIFICATIONS AND POTENTIAL OF THE PRINCIPAL INVESTIGATOR: The applicant was appointed an Assistant Professor in 2005. The applicant trained as a postdoctoral fellow and developed expertise with derivation of vascular cells from ES. S/he published 3 first author papers in solid specialty journals on his/her post-doctoral work. Since 2005, the PI has a modest publication record, with two articles on derivation of endothelial cells from murine embryonic stem cells.
The applicant is committed to develop tissue engineering approaches using ES cells integrated into animal disease models. The candidate is clearly able to carry out the ES work, is fully independent, and has recruited collaborators to assist with the technology platforms and animal models. Mentors, although limited at his/her institution, will assist in his/her development as a stem cell biologist. The career development plan is not particularly strong. Most of the description relates to the past experience during post-doctoral work, and very little to future plans.
INSTITUTIONAL COMMITMENT TO PRINCIPAL INVESTIGATOR: The institutional commitment is strong, but the institution is relatively new, so has a limited track record in supporting young faculty. The institution is able to provide most of necessary resources and centers to successfully execute the proposed specific aims. The applicant was provided with startup and 600 sq ft laboratory space with tissue culture facilities and small equipment, microscopes, etc. The animal work would be done at another institution in collaboration with the co-PI. The Dean commits to provide additional funds (10K per year) and teaching relief (1 course per year) in support of this application. There is a clear commitment to stem cell biology and so far several faculty are on campus. Additional mentorship can be recruited from outside.
DISCUSSION: Reviewers concurred that the research design is poorly developed. A major complication in this study was the lack of clarity and rationale for choosing specific cells for each study. It was not clear to reviewers which cells would be used in each experiment, and why.
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:
- Csete, Marie