A few years ago, Tom Rando, MD, PhD, found that if the circulatory systems of a young and an old mouse were connected, something in the blood of the young mouse seemed to rejuvenate the old mouse's liver and muscle. And something in the old mouse's blood seemed to age the young mouse's equivalent organs and tissues. Rando taught Tony Wyss-Coray, PhD, the mouse-hookup technique, and last year the latter showed that factors in blood can similarly influence the robustness of stem cells in the brain, too. (This was the subject of a recent Stanford Medicine article.)
Meanwhile, Howard Chang, MD, PhD, and one or two other investigators in the research-osphere were showing the world that a whole lot of the DNA in each of our cells codes for not proteins but RNA molecules whose job it is to fire up or shut down the genes that do code for protein production. (For more, see this.)
In a just-out review article in the journal Cell, Rando and Chang raise the possibility of getting old cells to act younger. And not just any old cells, but the "adult" stem cells that reside in most if not all of our various tissues.
Most of us are more familiar with these cells' more publicized relatives, embryonic stem cells (eSCs). These superstars are famous for being able to perform two tricks. They can multiply indefinitely in a dish, and they can differentiate into any of the 200-odd cell types in our body. That's good and it's bad. Good, because they offer the promise of regenerative medicine: essentially, differentiating eSCs into the needed cell types and infusing them to rejuvenate worn-out or defective tissue. Bad, because on their way to becoming the right kind of cells, they could go wrong instead, and become tumors.
Unlike eSCs, tissue-resident cells already know what they want to be when they grow up: They want to be whatever type of cell within that particular tissue that happens to be in short supply. In other words, these adult stem cells are already committed to a given lineage. A nerve stem cell's not going to surprise you by turning into a fat stem cell.
Rando and Chang's review, and this Q-and-A session I conducted with Rando the other day, explore the prospects for restoring aging tissues' tiring stem cells to more-youthful activity levels. It might be possible to kickstart them with bloodborne factors isolated through experiments of the type I mentioned above - or, better, with pharmaceutical compounds that mimic the actions of those factors.
I feel younger already.