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RS1-00217-1: Instructive Biomaterials for Stem Cell Differentiation

Recommendation: Not recommended for funding

Public Abstract (provided by applicant)

Embryonic stem cells (hESCs) have the potential to differentiate into all adult cell types and will have profound applications in tissue engineering and regenerative medicine. However, a thorough understanding of how to control stem cells so that a wide range of different cells, bone, muscle, nerve, etc. can be obtained is not known. It is proposed to simulate conditions in the human body by combining for the first time both mechanical and biological control in the differentiation of stem cell. Using state of the art polymer chemistry, cell scaffolds which combine all of these features will be prepared and the right conditions for each type of stem cells determined. Due to the huge range of possible variables we will also take advantage of highly parallel arrays of scaffolds which will allow thousands of different conditions to be evaluated at the same time, greatly increasing the speed of discovery.This interdisciplinary represents a new paradigm that will be used to screen for conditions that reproducibly and specifically generate all cell types from a single parent source of stem cells.

Statement of Benefit to California (provided by applicant)

The ability to produce desired cells lines for the treatment and study of disease is of paramount importance for California from both a social and economic viewpoint. In this proposal we will initially design arrays of synthetic polymer scaffolds that will be used to control the differentiation of retinal cells that are useful in treating Age-related macular Degeneration as well as Parkinson’s disease. Both of these diseases are particularly relevant for California’s population due to climate and population demographics. The techniques that will be developed to optimize these polymer scaffolds will allow thousands of different conditions to be examined at the same time which represents a new approach in this field that will allow the differentiation of stem cells into virtually any other cell to be accurately controlled and predicted. This represents a significant business opportunity for California and the implications for tissue engineering to repair traumatic injury and treat disease is profound.

Review

SYNOPSIS: The applicant is a director of the materials research laboratory and proposes growing hESC on 3-dimensional synthetic biomaterials (hydrogels containing peptide sequences from biological molecules) and combinations of developmentally regulated factors (such as growth factors and inhibitors) with the goal of generating cells that would be applicable for retinal repair (photoreceptors, retinal ganglionic cells, and retinal pigmented epithelium).

SIGNIFICANCE AND INNOVATION: This is an important area of research that where the combination of ideas presented is unique. 3-dimensional hydrogels, growth factors, and cell adhesion molecules are all known to affect differentiation and behavior of embryonic stem cells. Hydrogel arrays of scaffolding materials will be developed for high throughput screening. In most cases, these factors are studied individually but most investigators have not attempted to combine all of these factors into a series of systematic studies of cell differentiaton.

The PI proposes that specific arrays for 3-dimensional materials seeded with specific growth factors can be used to direct hESC to particular pathways of retinal cell differentiation. This is a novel hypothesis and proposes to use innovative chemistry to generate 3-dimensional substrates.

STRENGTHS: This is a proposal in an important area of investigation that systematically assesses effects of hydrogels, cell adhesion molecules, growth factors, and other molecular regulators of differention, on hESC differentiation. There is an emphasis on high-throughput analyses; this is necessary to generate numerical data that will be needed to assess differentiation patterns of cells.

The focus on differentiation of the cells towards retinal photoreceptors, ganglionic cells, and pigmented epithelium is likely to generate cells for an important class of diseases. Recent data suggest that embryonic stem cells that have been differentiated to particular stages can repair retinal cells.

The Principal Investigator (PI) has extensive experience with the development of novel chemistry for generating cell substrates, has trained in hESC techniques over the past year, and has experience with various methodologies required to assess differentiation of hESC cells. The PI has established numerous collaborations, including one colleague who is an expert on retinal development and diseases, another collague who is director of a stem cell biology laborator and a well-trained investigator who recently completed a PhD and has already published 6 peer-reviewed papers, and with another colleague who confirmed his/her collaboration in an enthusiastic letter that stated that he/she will be an Adjunct Professor at the PI’s institution.

WEAKNESSES: There is no evidence from either hESC or any model developmental system that supports the hypothesis. This project is considered by a reviewer to be a shot in the dark. Some preliminary data from some model system (or embryonic stem cells) should be included to show that this novel idea has some hope of success. Although this is a well-written application that proposes a feasible approach to a very important problem, to be done in collaboration with several of the top scientists in the field, a weakness of the application is that it may be too ambitious and comprehensive in scope to be carried out during the time-frame of the grant proposal; some prioritization of the different molecules and approaches that will be used would have been helpful.

Although high-throughput methodologies were proposed, it is not clear that these methods will be in place and will generate sufficient data for the investigator to identify the specific conditions needed to generate the target cells.

DISCUSSION: One reviewer commented that there is no reliable way to make cells that are useful for retinal repair, and the PI is an expert in creating well-defined hydrogel arrays for high throughput screening. Another reviewer noted that while the PI is a fantastic chemist, this application is not suited to this RFA or to the differentiation of hESCs. There is no evidence that what the PI intends to do would direct differentiation. Would this work create downstream benefits to advance medicine more broadly? More specifically, a reviewer questions how the applicant will know that they have pigmented cells since this was not discussed, and there was not a lot of detail provided on how this work would be done. There was also discussion about whether there was evidence for cross-species transplantation, which there appears to be (from mouse to pig) within this immunologically-privileged site. Therefore, photoreceptor transplantation studies should be possible.

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:

• Steindler, Dennis
• Lansing, Sherry