Diabetes and stem cell researchers turn to the lowly spleen.

The spleen gets no respect. Long seen as superfluous, the adult spleen of the mouse has recently been shown to hold stem cells that, in diabetic mice or genetically altered mice that lack a pancreas, effectively regenerate insulin-producing islet cells of the pancreas. Stem cells of the spleen express Hox11, a highly conserved transcription factor that plays a major role in the development of organs in vertebrate and invertebrate embryos. Hox11 and other members of the Hox family of genes may give stem cells of the spleen the capacity to mature into cell types other than islet cells, including neurons and bone cells. Multilineage splenic stem cells may trace to the embryogenesis and possible persistence into adulthood of a fetal stem cell region called the aorta-gonad-mesonephros (AGM). This Perspective calls for reappraisal of the lowly spleen for treating diabetes and other diseases of aging.