Discovery news says that a group of mice genetically engineered to age rapidly and grow telemerase when exposed to estrogen tend to recover their youth when exposed to estrogen. Already visions of a technological fountain of youth dance in many a journalist's head. Especially because telemerase is something easily obtainable that you could probably inject yourself with as early as tomorrow if you ordered it this morning.
Ah, but not so fast cowboy. The article also points out that this may be a quirk of the rapid aging genes. So maybe it might help someone with a rapid aging condition, but not provide boundless youth to whoever wants it. Even so, this is a remarkable piece of medicine going on here.