SYNOPSIS: The goal of this project is to gain a better understanding of how adult and embryonic human embryonic stem cells (hESCs) integrate and survive in the retina, and to repair the retinal pigment epithelium (RPE) in mouse models. The proposal explores the potential of stem cells to treat retinal degeneration, and compares adult and embryonic stem cells as a source of cells that are capable of delaying or diminishing neuronal loss in the retina.
In the first aim, the applicant proposes to test the hypothesis that minimally differentiated hESC-derived RPE will migrate less well than fully- or more differentiated hESC-derived RPE cells, and that migration will depend not only on the differentiation status of the cell type involved but will also depend on the site of administration and level of expression of CXCR4. In this and subsequent aims, the project plans to determine the relative efficiency by which human bone marrow-derived CD34+ cells are able to home to the RPE layer in an injury model and contribute to endogenous regeneration in this model and to compare results to these using hESC-derived RPE cells. The applicant is interested in the role that CXCR4 may play on migration and will measure this on differentiating hESCs using laser scanning cytometry. Much of this work will be done in the NOD/SCID/MPSII mouse which will both tolerate xenografts and also has photoreceptor degeneration.
In Aim 2, the applicant plans to test the hypothesis that more fully-differentiated hESCs will have better long-term integration and retinal regeneration than adult stem cells and minimally differentiated hESCs.
In Aim 3, the plan is to test the hypothesis that xenorecognition in an immunocompetent environment will inhibit tracking, integration and long-term survival of the transplanted hESC-derived RPE. In the third Specific Aim he will explore the immune response(s) to stem cell transplant and the effects this might have on migration, differentiation and survival of transplanted cells.
This proposal explores the potential for stem cells to treat retinal degeneration, and compares adult and embryonic stem cells as a source of cells that are capable of delaying or diminishing neuronal loss in the retina. The principal investigator (PI) is particularly interested in isolating retinal pigments epithelial (RPE) cells as a cell that can provide key trophic support for photoreceptors. Loss of the RPE in age-related macular degeneration and retinitis pigmentosa and replacement of these cells is the target of this proposal. He will compare human embryonic stem cells (hESCs) at different stages of development with human adult bone marrow. He is particularly interested in their migration to the retina and will explore different routes of administration. He is interested in the role that CXCR4 may play on migration and will measure this on differentiating HECs using laser scanning cytometry. Much of this work will be done in the NOD/SCID/MPSII mouse which will both tolerate xenografts and also has photoreceptor degeneration. In the third Specific Aim he will explore the immune response(s) to stem cell transplant and the effects this might have on migration, differentiation and survival of transplanted cells.
STRENGTHS AND WEAKNESSES OF THE RESEARCH PLAN: These studies aim to contribute to the development of stem cell therapies for diseases such as age related macular degeneration (AMD) and retinitis pigmentosa. It is thus an interesting proposal in a clinically relevant area.
The major strengths of this proposal are that the candidate has the potential to become a well-qualified scientist/clinician, he is working with a strong group of colleagues, and the clinical target is of major importance.
Unfortunately, the research plan suffers from a number of weaknesses. Although the hypothesis and goals are well articulated, the experiments are poorly designed. In many cases, it is not clear what model system is being used for which experiments, and precise quantitative endpoints are not identified. It is apparent that the investigator has little direct experience with these model systems, as the comparisons between hESC-derived and adult stem cell derived cells are unclear at times. In addition, in the use of abbreviations and model systems there is an unwarranted assumption of knowledge and gene products, and the background material related to model systems and gene products are not provided in enough detail for the reviewer to gain an appreciation of the rationale behind certain experiments and methodologies. For example, it appears that the use of the MPS VII mice bred to be an immunodeficient background which possesses the GUSB mutation will allow human beta glucoronidase expressing human cells to be detected where host cells will not be detected in this system. However, this was not precisely described and the nature of this model is assumed to be known. In addition, what is the RCS rat? Some preliminary data is shown in the NOD\SCID\MPS VII mouse model using human CD34+ cells but there is essentially no data with HESC-derived RPE cells. Therefore, the preliminary data are quite limited in their ability to support the proposed studies. A question could also be raised about whether the RPE might be the best cell to replace. One reviewer commented that there is no evidence to date that these cells are useful in neuroprotection, as noted by the applicant. The reviewer also noted that , in the clinical scenario, delivery or transplantation of cells designed to give rise to RPE might be too late.
The PI is relatively untested scientifically to take on such a large series of ambitious experiments, and has a limited scientific background. Some of the data presented in the preliminary data seems to parallel similar experiments published by Li, et. al, Investigative Ophthalmology and Visual Science, 2007 and 2006, and results of Atmaca-Sonmez, et. al, Experimental Eye Research 2006, yet it is interesting that the PI does not reference these papers. There also appears to be significant other literature reporting transplantation of neural progenitor cells to replace the RPE, yet most of these references are not cited and this potential cell type derived from hESCs to repair the retinal epithelium is not considered in this project.
The experiments evaluating the role of CXCR4 in determining the ability of stem cells to migrate or home to the RPE are not well-designed. They are based on the premise that hypoxia will upregulate CXCR4 expression. Of course, hypoxia may induce many other changes other than CXCR4 expression which may affect migration and therefore these experiments are not designed in a way that will determine a precise roll of CXCR4 in homing and migration to the RPE. Also, in Aim 1 it is proposed that PEDF expression would be used as a maturational marker. Although the literature appears to suggest that PEDF is a signaling molecule that can increases RPE maturation, it is not clear which cells express this factor or that increased expression would indicate a more mature state of the RPE itself (i.e.—although it is expressed doe not necessarily indicate the maturational effects of PEDF have been achieved. Also in this aim, the investigators propose to select cells expressing RPE65 in differentiating cultures and that these cells would be sorted and purified. However, the feasibility of this is not described. Although his colleagues are working on these cells, more detail of how they are obtained, sorted, etc., would have been appropriate. In many cases, the experimental endpoints are descriptive, nonquantitative, and based on histology and immunostaining.
On a minor note, there were several spelling mistakes/typos in this proposal- in a five page application there really should be none. Furthermore, consideration of and reference to studying humans in human clinical trials within the context of the application is really beyond the scientific and funding scope of the project
Thus, this is a clinical scientist with good potential addressing a clinically-important question in ophthalmology within a strong visual sciences department. He appears to be establishing strong basic science mentorship relationships, but has a limited scientific background at present. The research proposal is poorly organized, imprecisely written and contains non-quantitative, poorly defined endpoints. The preliminary data is weak and does not reassure reviewers that the project is feasible.
QUALIFICATIONS AND POTENTIAL OF THE PRINCIPAL INVESTIGATOR: Dr. Telander is a young clinical investigator with good training and background. He completed his MD/PhD and ophthalmology residency at the University of Minnesota and just recently completed a vitreo-retinal surgery eye fellowship at the Jules Stein Eye Institute in Los Angeles. From 2003 to 2005 he was involved with clinical ophthalmology as an attending physician in Los Angeles. From 2003 to 2005 he was involved with clinical ophthalmology as an attending physician in Los Angeles. Since 2005, he has been an Assistant Professor of Clinical Ophthalmology at UC-Davis Medical Center Department of Ophthalmology and Vision Science. He has received awards for teaching and has been heavily involved in medical school activities while publishing several clinical papers. A concern could be raised about his scientific expertise and training to take on the proposed research. He will rely heavily on his colleagues here, from whom he has garnered a number of letters of support. He has no experience in culturing ES cells as of yet. His mentoring plans seem appropriate. He has strong letters of support from the UC Davis Executive Associate Dean and senior colleagues working in stem cells and vision upon whom he will be reliant.
The investigator completed his MD/PhD and ophthalmology residency at the University of Minnesota and just recently completed a vitreo-retinal surgery eye fellowship at the Jules Stein Eye Institute in Los Angeles. From 2003 to 2005 he was involved with clinical ophthalmology as an attending physician in Los Angeles. Since 2005, he has been an Assistant Professor of Clinical Ophthalmology at UC-Davis Medical Center Department of Ophthalmology and Vision Science. He has received awards for teaching and has been heavily involved in medical school activities while publishing several clinical papers.
INSTITUTIONAL COMMITMENT TO PRINCIPAL INVESTIGATOR:
The institution has a strong institutional stem cell core group of investigators and facilities. There is a strong stem cell research program and visual science group at UC-Davis with numerous stem cell faculty and a commitment on the university’s part to building infrastructure core, resource development and recruiting new faculty. In the ophthalmology group, there are 20 vision scientists with 16 NIH-funded grants. Significant stem cell core facilities are available at UC-Davis through the established stem cell program including FACS sorting core, immunodeficient mouse core, human ESC karyotyping and teratoma services, and plans to build a new state of the art GMP facility. In addition, vector core and auto MACS technologies are available. A significant amount of CIRM funding is already in place at UC-Davis through CIRM Comprehensive Research Grants, CIRM Shared Research Laboratory grants and the CIRM’s Stem Cell Training Program, in addition to other CIRM-funded investigators at UC-Davis including Drs. Zern, Yamoah, and Reddi.The infrastructure in his lab and the core facility at Davis all seem appropriate to carry out the work.
The applicant has a limited amount of extramural funding currently, but letters demonstrate a strong commitment to his development as a clinician-scientist from his institution. An NIH-K30- mentored clinical research training program is potentially available to Dr. Telander as formal mentorship training, conditional on his receipt of CIRM funding.
It is not apparent that independent lab space is available to Dr. Telander, and institutional resources may be controlled by other investigators. At the moment, it appears he has been provided research space in the labs of Drs. Hjelmelend and Nolta. In addition to these two basic science mentors, he has established clinical mentors in Drs. Morse and Keltner. Additional lab space for Dr. Telander may be assigned in the new state-of-the-art GMP facility that is scheduled to be completed in 2008. There appears to be a commitment to expand stem cell research at UC-Davis both through recruiting new faculty (adding to an already-strong, 110 stem cell investigator-rich program) and new building infrastructure.
DISCUSSION: Reviewers commented that this is an accomplished physician in a strong environment with good institutional support, doing research on a clinically-important problem. Unfortunately, the applicant does not have the research background to undertake this ambitious proposal, and the research proposal suffers from lack of scientific rigor. For instance, the CXCR4 experiments are poorly designed - hypoxia does many things other than increase CXCR4. Use of murine bone marrow stem cells is problematic as it is unlikely to yield any useful output; it isn’t always clear why the applicant used both adult and embryonic cells; and the experiments as designed will not elucidate the role of chemokines in homing, which was seen by reviewers as an interesting question. Failure to reference the literature contributed to the feeling that the candidate was very new to the field. Finally, the proposal was poorly written and organized, heavy in acronyms, and had typographical errors, all of which made it difficult to read.
On the whole, the panel was supportive of the applicant and the idea being addressed in this application, and felt that the proposal deseved to be re-written with more preliminary data and more careful advice from scientific mentors.
