There’s a lovely review by Thomas Rando in Nature’s recent Insight on stem cells.

The review turns one standard assumption in the field on its head, or at least holds it by its ankles and shakes it a bit. We think of stem cell technology as potentially forming the basis of a living pharmacopoeia of lifespan extension, i.e., of stem cells as having value as a means of intervening in age-related decline in tissue function. But what about the information flow in the other direction?

The possibility that stem cells could have therapeutic applications in the context of normal ageing raises two related questions. First, what is the effect of ageing on stem cells themselves? Second, to what extent can the functional decline of a tissue be attributed to a limited (and perhaps declining) capacity of the resident stem cells to maintain normal tissue structure and function?

In other words, if stem cells are dependent on a youthful tissue environment in order to serve a regenerative function, they might have a tough time living up to our expectations, at least in a naive “add stem cells and behold the miraculous Cure For Everything” paradigm.

A deeper understanding of the relationship between tissue environment and stem cell function, as well as the impact of aging on the microenvironment itself, is clearly needed.