Pluripotent stem cells have been differentiated into cardiomyocytes (CMs), and in small animal models have been reported to improve cardiac contractile function. However, the PI suggests that the assessment and prevention of post-transplantation arrhythmias after stem cell transplantation remains poorly understood. This gap in knowledge is targeted by this proposal. The central hypothesis is that directed cardiac differentiation and maturation of pluripotent cells will generate fully functional CMs (presumably more mature) that will not cause arrhythmias and thus be more suitable for cell-based therapeutics. The plan of attack consists of several approaches to drive differentiation and maturation of CMs. Once the optimal cells for transplantation are established, large animal models will be used to establish efficacy. Another goal will be to drive differentiation and maturation of patient-derived pluripotent cells to CMs to create in vitro human heart disease models for use in therapeutic development.
Reviewers felt that the overall proposal suffered from a poorly coordinated mix of aims that reflect the overly broad scope of the proposed concept(s) in the context of the applicant’s relative lack of a substantive track record to date. The disease target was not clearly articulated in the proposal. The application is titled as if directed towards the treatment of cardiac arrhythmias by stem cell therapies, whereas better stem cell therapy for heart failure is also a therapeutic target. The reviewers noted that a severe limitation of the proposal to treat arrhythmias would be the relative implausibility that any cell therapy will be workable within the five year horizon for first-in-human studies, as required by the terms of the present RFA. Another reviewer noted that pacemaker therapy already exists for treatment of arrhythmias. Finally, even in the better-posed case of cell therapy for heart failure, reviewers felt the concept focus was relatively immature.
A significant portion of the proposal is to optimize the derivation of pluripotent-cell derived cardiomyocytes to minimize their potential to create iatrogenic arrhythmias. Reviewers felt a weakness with the proposed strategy is that while obtaining CMs from pluripotent cells is a relatively simple endeavor, the basic science of the timing, transitioning to progenitors, and the differential electrical activity remains very poorly understood. Another concern was that while the proposal emphasized safety, much of the proposed work will be done with a class of pluripotent cells which were perceived by reviewers to be the least safe cell at this time for therapeutic use. Two strengths of the concept were the clinically-relevant existing large animal models and the on-site facility (including GMP) in which these studies could be conducted. These characteristics of the project would facilitate reaching the research goals, but could not overcome concerns about the lack of focus of the proposal.
While noting that a strength of the proposal was having a cardiologist as PI, reviewers also noted that the PI’s productivity and track record in the subject matter of the proposal do not match the overly-ambitious scope of the project.
The planning approach centered around four proposed aims, but reviewers felt they were but poorly characterized with overlap among different aims. Although there are a number of strengths in the participating team, the requisite technologies have not yet coalesced convincingly.
In summary, the panel felt that the proposal suffered from a lack of focus, and that the concept had insufficient maturity. Coupled with the PI’s lack of sufficient experience and expertise in the area of the proposal, the panel was not confident that this broad-scoped project could be brought to fruition in five years.
Human embryonic stem cells (hESCs) have been shown to be able to differentiate into cardiomyocytes (CMs), and in small animal models have shown improvements of cardiac contractile function. However, the PI suggests that the assessment and prevention of arrhythmia following transplantation of stem cells remains poorly understood. This gap in knowledge is targeted by this proposal. The central hypothesis is that directed cardiac differentiation and full maturation of hESCs or induced pluripotent cells (iPSCs) will generate better quality CMs that will be more suitable for cell-based therapeutics by facilitating the contribution of fully functional transplanted cells into recipient hearts.
Reviewer One Comments
• Preliminary data has apparently established that hESC-derived CMs are electrically, contractively, and structurally immature. Thus, the mission here is to define conditions for hESC/iPSC cardiomyocyte differentiation and maturation to make better quality CMs for transplantation.
• A multi-disciplinary team with expertise from different fields is proposed, including: stem cell biologist, cellular electrophysiologists, expert in biophotonics physicists, and cardio electrophysiologists and cardiologists. The plan of attack consists of genetic and pharmacological approaches in which combinatorial chemical and peptide libraries will be screened for small molecules that promote pluripotency or drive maturation of CMs. Once the optimal cells are established, large animal model(s) will be used to establish efficacy.
• Another goal will be to drive differentiation and maturation of patient-derived iPSC to CMs to create in vitro human heart disease models for therapeutic development.
• Since UC Davis is the home of respected veterinary school and non-human primate center, the use of larger mammals in pre-clinical models will be facilitated.
• The time from beginning to successful outcome is estimated at 5 years.
• While obtaining CMs from hESCs is a relatively simple endeavor, the basic science of the timing, transitioning to progenitors, and the differential electrical activity remains very poorly understood, and thus the concept is immature for a disease team approach
• The PI has committed 5% effort.
• The PI’s productivity does not match the over-ambitious aspect of the project, based on the quantity and quality of publication.
• In addition to the PI, the other members of the team are Dr. Ronald Li UCD, cell engineering and differentiation with no salary requested; Dr. Thomas Huser, Associate Professor, UC Davis Center for Biophotonics Science and Technology; Dr. Kit Lam, Chief Division of Hematology Oncology, providing expertise in combinatorial chemistry and the libraries; Dr. Jan Nolta, director of UCD stem cell program, will be a consultant of translating aspects of basic research.
• The environment appears to be adequate to support the proposed studies.
• The hypothesis proposed to be tested here is that both hESCs and iPSCs (reprogrammed somatic cells toward pluripotent cells) can be guided to generate useful CMs (presumably more mature) which are more suitable for transplantation than ones currently available.
• Four specific aims are proposed, but poorly characterized with overlap among different aims. The first specific aim is the peptide and compound screens in order to screen for small molecules that maintain pluripotency or drive maturation of hESCs/iPSCs-CMs. H1, H9, HESC2, 3, 4 in addition to Korean and Chinese lines (in my opinion, not very well characterized).
• Aim 2 is the same as Aim 1, except that patients’ iPSCs will be generated, with a goal of developing patient-specific cells to use as in vitro models for therapeutic development. This is a high-risk aim, as conversion of iPSCs to CM is very poorly characterized and with tremendous variability depending on the state of the somatic cell used to reprogram.
• Aim 3 is to check in vivo safety and functionality of the hESC/iPSC CMs in swine and non-human primates.
• Finally, Aim 4 is to translate these findings for human trial.
Reviewer Two Comments
• Devise a protocol that allows differentiation directly into mature cardiac myocytes that should have a better performance and especially less arrhythmic potential.
• Another disease specified is sinus node dysfunction which appears not to be standard target disease since disease is treatable by conventional treatment
• Strength is the already established animal models (monkey and pig which appear to be very appropriate models)
• Another strength is having GMP facility at hand
• The proposal emphasizes safety, but the concept is mainly based on the least safe stem cells, the iPS cells
• The applicant institution has established multiple programs including training grants and a center that should allow smooth integration of proposed research into the environment
• Interesting is multidisciplinary team (Figure 1: from Atom to non-human primate concept) and Figure: all projects relate to a central hypothesis
• co-investigators are both very strong investigators with some experience in the field of ES cell differentiation
• major strength for potential application: cardiologist as PI
• however no plans for cardiac surgeon, which would be necessary for planning a trial
• specific aims describe experimental timelines in the range of 3-6 month, which is both unrealistic, and not consistent with what is required by this RFA
Reviewer Three Comments
The application is entitled as if directed towards the treatment of cardiac arrhythmias by stem cell therapies. If so, the most severe limitation of the proposal would be the relative implausibility that any cell therapy will be workable within the five horizon for first-in-human studies, as required by the terms of the present grant competition. There is simply no cogent reason to think so.
However, the title is an odd misnomer, as the main substance is devoted instead to optimizing the electrophysiological properties of hESC-derived and iPS-derived cardiomyocytes, to minimize their potential to create iatrogenic arrhythmias. Even in the better-posed case of cell therapy for heart failure, where at least a few human studies have been done (with other cell types), it can be questioned whether hESCs are far enough along in the translational pipeline, given many unsolved questions (more uniform differentiation, purification of cardiomyocytes without genetic markers, tumor risk, immune rejection) and the lack of a coordinated plan to overcome the latter aspects. Conversely, iPSCs warrant attention as they overcome the transplantation issue, but with current technologies require genetic manipulations and hence all the known hazards of insertional mutagenesis or gene therapy sui generis.
In addition, the combined genetic and pharmacological screen has extremely weak scientific underpinnings, by comparison to screening activities proposed at other centers for lower-hanging targets, and the goal of functional maturation is unusually complex and premature for a grant competition aimed at workable human studies within 5 years. Does maturation require 1, 2, 10, or 20 “hits”? Are the intermediate phenotypes adequately defined for a truly high-throughput mode? There is not a sufficient basis for reasonable expectation that timely human trials would be achieved.
The PI, Nipavan Chianvimonvat, is Professor of Medicine at UC Davis and a good research electrophysiologist, with roughly 30 published manuscripts, often at the level of Circulation Research. However, the PI has not yet a substantive track record in the realm of the proposal, and the depth of scientific leadership is significantly less than in more competitive applications.
Although there are a number of strengths in the participating team, the requisite technologies have not yet coalesced convincingly. For example, the non-human primate facility is a potential asset, but the applicants do not yet have a cogent case that this would be required or even valuable, by comparison to more routinely accessible large-mammal models. The overall proposal suffers from a poorly coordinated mix of aims that reflect the applicants’ weak background in stem cell biology and the highly premature status of the team.