When the production of induced pluripotent stem cells (iPSCs) was achieved about five years ago, it seemed they might provide a good alternative to working with embryonic stem cells, in both research and clinical applications. Then problems showed up, such as potential tumorigenicity, inadvertent DNA damage, and incompatibilities with the source’s immune system. More recently, the alternative of “reprogramming” adult cells directly from one type (such as skin) to another type (such as neurons) has been achieved. But this newer technique has problems of its own.
The discovery of induced pluripotent stem cells (iPSC) in 2006 opened the door to promising research and therapeutic techniques, such as the generation of disease models and the potential to replace cells damaged by neurodegenerative diseases like Parkinson’s. Derived from fetal or adult cells, iPSC strategies avoided the ethical issues surrounding embryonic stem cells. But they retained one critical drawback—the propensity for tumor formation. In the last 18 months, however, researchers have discovered a new reprogramming technique that could avoid that problem altogether: the direct conversion of one differentiated cell type to another.
Several potential problems with reprogramming are discussed in the article. One is that adult cells have limited ability to divide before becoming senesecent. This makes it hard to produce enough cells for practical applications. A more serious potential problem is that current techniques for reprogramming cells uses viral vectors to activate necessary genes. This was a problem early on with iPSCs, because it could introduce cancer-causing mutations. Subsequently, better techniques were developed for producing iPSCs, but haven’t yet been explored for cell reprogramming.
It’s not clear that iPSCs themselves are out of the picture yet, either. Very recent research claims to show that they can be produced to be very, very close in important respects to actual embryonic stem cells. (As reported here.)