EurekAlert! passes on an advance in the technology of reprogramming cells: "In the past few months, a slew of papers have indicated that the therapeutic potential of a promising type of stem cell, called induced pluripotent stem (iPS) cells, might be limited by reprogramming errors and genomic instability. iPS cells are engineered by reprogramming fully differentiated adult cells, often skin cells, back to a primitive, embryonic-like state. Given these problems, a team of researchers [wondered] if there might be a better way to regenerate lost tissue to treat conditions like heart disease and stroke. ... they outline a method to obtain a new kind of stem cell they call 'induced conditional self-renewing progenitor (ICSP) cells.' ... It's amazingly cool that we can dial adult cells all the way back to embryonic-like stem cells, but there are a lot of issues that still need to be addressed before iPS cells can be used to treat patients. So we wondered... if we just want to treat a brain disease, do we really have to start with a skin cell, which has nothing to do with the brain, and push it all the way back to the point that it has potential to become anything? In this study, we developed ICSP cells using a cell from the organ we're already interested in - the nervous system, in this case - and pushed it back just enough so it continued to divide, giving us a quantity that we were able to apply efficiently, safely and effectively to treat stroke injury in a rodent model. ... the [reprogramming gene] used here is conditionally expressed. This means that ICSP cells can only produce [the gene] when the researchers add a compound called tetracycline to laboratory cultures. When tetracycline is removed, the cells cease dividing and start differentiating. Then, once transplanted into to an animal model, ICSP cells are no longer exposed to tetracycline and take their growth and differentiation cues from their new environment."