Embryonic stem (ES) cells are embryo-derived pluripotent cell lines that can give rise to each and every cell type in the body. As such, these cells are invaluable tools for research into the mechanisms of tissue formation and the development of disease, and provide a promising source of """"""""replacement cells"""""""" for tissue repair. However, research with embryo-derived ES cells, particularly with respect to their use as disease models or transplantable replacement cells, has been hampered by regulatory hurdles impeding the derivation of new lines and by difficulties in obtaining """"""""patient-specific"""""""", histocompatible cells. Exciting recent discoveries enabling direct """"""""reprogramming"""""""" of adult somatic cells to ES-like """"""""induced pluripotent (iPS) cells"""""""" appear to have lowered these hurdles, providing a facile mechanism for the production of patient-specific pluripotent cells for research and therapy. The revolutionarily development of iPS technology has opened many new opportunities perhaps the most exciting potential application being the use of patient-specific tissues for transplantation. However, currently the most efficient ways to reprogram somatic cells involve the introduction of cDNAs that encode four mammalian transcription factors into somatic cells via retroviral vectors. There is great concern regarding the safety of returning these manipulate cells to patients given the risk that virus- mediated insertional events can activate oncogenes or inactive tumor suppressors thus raising concern for the tumorigenicity of the reprogrammed cells. Thus, in response to the EUREKA initiative, we propose to develop a completely novel system to circumvent the issues associated with virally-generated iPS cells by reengineering specialized bacterial transkingdom secretion systems to deliver the iPS transforming proteins rather than virulence proteins directly into mammalian cells. This is an innovative and high risk approach that if successful would be a major advance in somatic reprogramming and would have tremendous impact on accelerating the delivery of iPS-based transplant therapies to patients as well as provide a new means of potentially increasing the efficiency of the generation of iPS cells.
A major breakthrough in stem cell biology has emerged with the demonstrated that differentiated somatic cells can be converted to pluripotent cells through the introduction of cDNAs into cells. These approaches hold tremendous potential for the patient-specific replacement based cell therapies, however currently a major roadblock in introducing replacement cells into patients is the possibility that the integration of DNA into the chromosomes of these cells can induce tumor formation. To circumvent this major roadblock in moving towards patient-specific therapies, we propose to develop a novel technology using re-engineered transkingdom bacterial secretion systems to directly introduce reprogramming proteins rather than the cDNAs that encode them into the differentiated cells.
|Reeves, Analise Z; Spears, William E; Du, Juan et al. (2015) Engineering Escherichia coli into a protein delivery system for mammalian cells. ACS Synth Biol 4:644-54|