(Cross-posted from Ouroboros: Research in the biology of aging ) One major barrier to the therapeutic use of pluripotent and totipotent cells is that by the time a patient needs them, their body has become less able to use them. The stem cell niche (i.e., those factors in the tissue microenvironment that stem cells require in order to function normally) changes with age, and not for the better: for example, embryonic stem cells lose proliferative capacity when confronted with aged niches. This appears to be a general problem in metazoans, and is conserved between humans and relations as distant as arthropods — fortunately for us, because it means that the tools and genius of the Drosophila community can be brought to bear on the problem. In the fruit fly, age-related changes in the stem cell niche are well-documented, especially in the reproductive system, and the molecular players are starting to be individually identified (see our previous post on Dpp , this one on BMP , unpaired and cadherins , and this nice review of the whole story). There are one or two tissues in which stem cells actually become more numerous with age, but the consensus seems to be that the aged microenvironment is generally not beneficial for stem cells. At least in the fly. (cont.) Category: Health & Medicine Year: General ...