These seem to be happening quite a lot, which must be good news. I’ll take you through this one slowly, in case you haven’t been paying much attention to stem cell research.
Once upon a time, there were two types of stem cells. Only embryonic stem cells were able to develop into any type of cell in the body (a trait called pluripotency), but they could only be acquired by destroying human embryos, which some people find distasteful. A more practical problem was that not many people donated embryos, so these pluripotent stem cells were pretty hard to come by. Adult stem cells were easier to obtain, but could only develop into a limited range of mature cell types.
In 2007, the picture changed a little. Scientists found a way of making mature adult cells pluripotent. They took human skin cells and used viruses to introduce four new genes, which successfully returned the cells to a state similar to embryonic stem cells. They called their creation ‘induced pluripotent stem cells’, or iPS cells for short.
Pluripotent stem cells derived from adult cells are a very useful prospect, since not only do they get around the problems with getting hold of embryonic stem cells, but they also mean that stem cell treatments could use cells taken from the patient who will receive the transplant, avoiding the risk of rejection. But there were problems with these iPS cells. The introduction of the foreign genes made them very likely to start dividing uncontrolably, producing tumours. Clearly they could not be used in treatments until this issue was resolved.
Two recent Nature papers and one in Science reported the creation of iPS cells by a method that did not use viruses, and allowed the inserted genes to be removed after the cells’ transformation. Another group used ‘excisable viruses’ to achieve the same thing.
Now scientists at the Scripps Research Institute in California have described the creation of iPS cells without any genetic manipulation at all. Instead they achieved the transformation simply by introducing a handful of proteins. This latest ‘breakthrough’ was published in the slightly stupidly named journal Cell Stem Cell.
Many more breakthroughs will be needed before iPS can fulfil their extraordinary therapeutic promise. For one thing, we will need to ensure that they are completely safe. This is not guaranteed, even when the cells have been manipulated without using genetic material – no method has produced cells identical to embryonic stem cells. ‘It will be important now to compare the different methods and go with the one that works the best,’ Konrad Hochedlinger of the Harvard Stem Cell Institute told Nature. Then there’s the matter of coaxing them into becoming the desired cell type for the particular treatment. Researchers will need to produce different cell types from iPS cells and see how they fare in the long run.
All the same, the field of induced pluripotent stem cells is making rapid progress, which can only be encouraging for the future of medical research.
Zhou, H., Wu, S., Joo, J., Zhu, S., Han, D., Lin, T., Trauger, S., Bien, G., Yao, S., & Zhu, Y. (2009). Generation of Induced Pluripotent Stem Cells Using Recombinant Proteins Cell Stem Cell DOI: 10.1016/j.stem.2009.04.005