The potential for use of stem cells in regenerative medicine has produced considerable excitement. While most of the current research in the area has focused on defining media components that control stem cell differentiation, relatively little attention has been paid to the problem of generating ideal in-vitro culture systems for optimal growth, and expansion of stem cells and their specific progenitors, for practical regenerative medicine applications. In addition, methods for expansion and propagation of stem cells and their progenies, available to date, collectively lack features to produce only a specific cell type either by a) Generation of specific lineage or cell types for harvest (subject of this proposal), and/or b) “Filtering” and separation of specific progenitors from all other cell types (not subject of this proposal, current in-house R&D). The overall objective of this project is to develop and demonstrate feasibility of a prototype bioreactor, modeling the in-vivo stem cell niche, for production of progenitor cells which are expanded and differentiated into specific tissue lineages (in the bioreactor) while maintaining a stable pool of stem cells for long-term production. Tools and technologies developed based on the proposed feasibility demonstration studies will provide the foundation required for development of new bioreactor based cell separation and purification methodologies for effective harvest of differentiated cell types away from undifferentiated cells (i.e. pivotal for safe and efficacious cell therapy and FDA approval). In addition, our commercialization strategies in partnership with larger “research tool” companies (currently in-progress) will generate commercial products for different sectors of this field, following successful accomplishment of the proposed studies.
Statement of Benefit to California:
The potential for use of stem cells in regenerative medicine has produced considerable excitement. While most of the current research in the area has focused on defining media components that control stem cell differentiation, relatively little attention has been paid to the problem of generating ideal in-vitro culture systems for optimal growth, and expansion of stem cells and their specific progenitors, for practical regenerative medicine applications.
Benefits for the state of California and its citizens:
1) Tools and technologies developed based on the proposed studies will provide the foundation required for upscale production of safe and efficacious cells for therapies facilitating translation to the clinic and FDA approval.
2) Our commercialization strategies in partnership with larger “research tool” companies (currently in-progress) will generate commercial products for different sectors of this field, advancing research and development enabling new regenerative cell therapies for uncured diseases.
The overall goal of the proposed research is to develop a 3D bioreactor system that models stem cell niches for the production of pluripotent stem cells and lineage-restricted progenitors derived from them. The bioreactor is a customized version of a commercially available system. The applicants propose to initially develop a co-culture system that includes a mouse stromal cell line and "cord blood embryonic-like stem cells" (CBE) to demonstrate the feasibility of the bioreactor. The applicants also intend to expand the study to develop a 3D niche-like microenvironment for the culture of human embryonic stem cells (hESCs).
Reviewers agreed that improved methods for large-scale expansion of various stem cells, including hESCs, without inducing differentiation, would have significant utility. Similarly, methods to reproducibly generate and harvest lineage-restricted stem or progenitor cells from large-scale (bioreactor) pluripotent cell cultures would be potentially of significant value, especially for clinical applications. However, reviewers felt that the proposed research program does not provide a clear path to these goals.
Although the second aim was found to be more straight-forward – to culture an established hESC registry line in the bioreactor using a hydrogel system and no feeder cells – it does not represent a step that completely overcomes a major roadblock in stem cell biology. If successful, it could have ultimate value in clinical applications. However, the ability to differentiate the hESCs quantitatively in the bioreactor towards a specified lineage and to isolate the differentiated cells free of potentially tumorigenic undifferentiated stem cells will require a more sophisticated strategy. The applicants acknowledge the need for a more comprehensive approach to the problem of scale-up, but the plan presented to overcome it is incomplete. The probability that the results of this work will move the field significantly forward was thought to be low.
Reviewers found the application to be written in a rather confusing manner that made it difficult to ascertain specific experiments contemplated at each proposed step. Reviewers noted that the cell types utilized in the first specific aim are not ideally suited to the research. The proposed cells are either transformed and/or non-human cell lines that are not appropriate for clinical translation or for the ultimate production of clinically useful human cells. Moreover, reviewers found that the applicants are rather unclear about what specific niche they wish to produce. If the niche is for hematopoietic stem cells then the choice of "ES-like" cells from umbilical cord blood is not the optimal choice, according to one reviewer. Reviewers also noted that a cord blood stem cell is not universally acknowledged to be embryonic-like and therefore may not be a suitable prototype for extending the studies to hESCs. Furthermore, reviewers felt that the rationale and advantages for using CBEs in the first aim versus hESCs in the second aim are not explained.
The aim of expanding hESCs in hydrogels was more clearly presented. However, the reviewers criticized their approach to simply adapt previously published work to the context of a bioreactor, rather than working refine and improve the culture environment. Consequently, reviewers were unconvinced that the work will generate important new information about stem cell niches, maintenance of "stemness", or regulation of lineage restriction. The technological problems that remain in isolation of specific, desired lineage-restricted derivatives from pluripotent (potentially tumorigenic, in the case of hES cells) are not clearly addressed and the discussion of ‘safe and efficacious therapy and FDA approval’ issues did not give reviewers comfort with the design of the studies. In general, reviewers found the logic of the proposal difficult to follow.
The PI trained at top universities and has biotechnology industry experience. Reviewers found no track record for the PI of leadership in the stem cell field or in the development of novel bioreactor systems. The rather large team includes individuals with strong publication and track records, but the letter of support from the consultant with most expertise in hESCs appeared to be an incomplete draft. The plan relies heavily on scattered consultants, which may be problematic. Reviewers were further concerned that the budget of nearly $1 MM for 2 years is excessive.