Credit: Image: Courtesy of the Salk Institute for Biological Studies
These fluorescent microscope images of testes from young (left) and old(right) fruit flies show the effect of aging on the stem cell niche (top center). The hub cells (red) that function as part of the stem cells' supporting niche express more of a microRNA known as let-7 (green) in aged flies, which changes the signaling properties of hub cells, leading to fewer stem cells surrounding the hub that are available for tissue maintenance.