| Only two years ago, in the fall of 2007, two teams | | | | of four genes - Sox2, c-Myc, Oct-4, and Klf4. These |
| of researchers reported the successful | | | | genes were inserted into virus particles and the virus |
| reprogramming of an adult human cell back to an | | | | was used to transfect adult skin cells. Activation of |
| original state of pluripotency. Such a reprogrammed | | | | these genes within the adult skin cell leads to the |
| cell - termed an induced pluripotent stem cell (iPS cell) | | | | expression of specific transcription factors. These |
| - has the ability to differentiate into any type of cell. | | | | proteins activate other genes within the skin cell |
| iPS cells have the ability to become specialized cells | | | | which cause the cell to return to a pluripotent state. |
| such as pancreatic islet cells which produce insulin, | | | | The breakthrough was front-page news in The New |
| intestinal lining cells which produce digestive enzymes, | | | | York Times, but many aspects of the procedure |
| kidney cells, heart cells, nerve cells, skin cells, and | | | | needed to refined and revised. Use of a virus to |
| muscle, ligament, cartilage, and bone cells. Under the | | | | introduce the transforming genes is problematic. Viral |
| right conditions iPS cells could produce specific cells, | | | | genetic material is transfected as well, and there may |
| tissues, and organs for use in treating disease and/or | | | | be many unanticipated results such as causing the cell |
| transplantation. | | | | to become cancerous. Viral RNA or DNA would |
| Reprogramming adult cells opens up entire new fields | | | | become a permanent part of the cell line - any cells, |
| of medical research. If iPS cells are found to be similar | | | | tissues, or organs derived from the original iPS cell |
| to embryonic stem cells (ESCs), the possibility of | | | | would contain that viral genetic information. Using viral |
| reprogramming will significantly impact the | | | | delivery systems on a large scale would result in |
| controversy surrounding ESC research. | | | | transformation of the human genetic heritage, with |
| Reprogramming uses adult cells rather than ESCs, and | | | | unforeseen and probably disastrous consequences. |
| much of regenerative medicine might be able to | | | | Research has been ongoing since 2007 to derive |
| proceed without the necessity for destruction of | | | | non-viral methods of introducing the transformative |
| embryos. | | | | genes. Dr. Rudolf Jaenisch, at the Whitehead Institute |
| The two teams, led by Dr. Shinya Yamanaka at | | | | for Biomedical Research in Cambridge, MA, leads one |
| Kyoto University in Japan and Dr. James Thomson at | | | | of the teams working worldwide to solve these |
| the University of Wisconsin, used similar methods to | | | | challenges. His team recently identified a small protein |
| reprogram adult human skin cells. Years of research | | | | molecule which is able to replace Klf4, one of the |
| led to the identification of several specific genes | | | | genes used to reprogram adult cells. If all the genes |
| which would induce a cell to return to a pluripotent | | | | can be successfully replaced by small molecules, a |
| state. Dr. Yamanaka initially worked with a set of 24 | | | | viral delivery system would not be necessary. Such a |
| genes, attempting to identify the most effective | | | | development would fully launch the field of |
| candidates. Research led to the selection of a group | | | | regenerative medicine. |