Transdifferentiation is the act of changing a cell directly from one type to another, without having to first go through the process of producing induced pluripotent stem cells and then differentiating them into the desired final product. This shows some promise as a yet more effective way of producing cells to order for research and therapies: "Human skin cells can be converted directly into functional neurons in a period of four to five weeks with the addition of just four proteins ... The finding is significant because it bypasses the need to first create induced pluripotent stem cells, and may make it much easier to generate patient- or disease-specific neurons for study in a laboratory dish. It may also circumvent a recently reported potential problem with iPS cells, in which laboratory mice rejected genetically identical iPS cells - seemingly on the basis of the proteins used to render them pluripotent. The new research parallels that of the same Stanford group in 2010, which showed it was possible to change mouse skin cells directly into neurons with a similar combination of proteins. However, when done in human cells, the conversion of skin cells to neurons occurs less efficiently and more slowly. ... We are now much closer to being able to mimic brain or neurological diseases in the laboratory. We may perhaps even be able to one day use these cells for human therapies. ... The direct conversion of skin cells to neurons contrasts with similar research that first transforms skin cells to a pluripotent, or developmentally flexible, state and then coaxes them to become neurons or other specialized cells. ... The iPS cell approach is doable and has been shown to work. We need to keep working on both strategies. It's possible that the best approach may vary depending on the disease or the type of research being done."

Link: http://www.eurekalert.org/pub_releases/2011-05/sumc-ss052511.php