|A colony of iPS cells generated from skin (courtesy of Kathrin Plath, UCLA)|
Groups who oppose embryonic stem cell research have argued that since both types of stem cells can form all cell types of the body, embryonic stem cells are no longer needed. Focusing entirely on iPS cells would eliminate the creation of new embryonic stem cell lines, most of which come from 4-5 day old embryos left over at in vitro fertilization clinics.
One thing to remember is that the embryos used to create embryonic stem cells were created by people using IVF procedures to start a family. When their family is complete, people have a choice to make about what to do with the excess 4-5 day old embryos being stored at the IVF clinics. Some people choose to simply discard the extra embryos. Others choose to donate those embryos to other infertile couples, and some couples choose to donate those embryos to medical research including the creation of new embryonic stem cell lines.
Those embryonic stem cells can form all the cells of the body, as can iPS cells, which are created from adult cells. However, there are some significant differences between the two cells types (as we chronicle in previous posts here and here). Right now, there are a handful of clinical trials just starting to test whether cells created from embryonic stem cells can treat two forms of blindness, one called macular degeneration and one called Stargardt’s disease. There are so far no trials testing therapies based on iPS cells, though a few are expected to begin in the next few years.
Betting on one cell type over the other is like betting on a horse before the race starts. People do it, but it’s a gamble. In the case of new therapies, betting on one cell type over another is really like betting on hundreds of races all at once – one race for blindness, one race for Parkinson’s disease, one race for Lou Gehrig’s disease, and another race for diabetes. For all we know, one cell type might be best for creating cells needed in people with diabetes, while a completely different cell type will be best for repairing hearts. We won’t know until we do the research.
Yamanaka himself has been concerned that his work is being used to argue against ongoing research using embryonic stem cells. He co-wrote a paper in Cell Stem Cells titled “New advances in iPS cell research do not obviate the need for human embryonic stem cells.”
Other experts agree. A panel of scientists brought together by the U.S. National Academy of Sciences agreed that the use of human embryonic stem cells is still necessary. As the expert panel, chaired by Richard Hynes of the Massachusetts Institute of Technology stated “It is far from clear at this point which types of cell types will prove to be the most useful for regenerative medicine, and it is likely that each will have some utility.” (Here’s a link to that report.)
We agree. That’s why we fund research using all stem cell types. You can see a break down of funding to different cell types and to different diseases on our web site. Here’s a list of all our awards, which total $190 million, to researchers creating or using iPS cells. You can also read our story about why embryonic stem cells remain the gold standard against which other stem cells are compared.
In this race, we’re betting on the best science not preconceived ideas about which approach will work. We are also betting on the patients who are waiting for the results of that research.