Where do hematopoietic stem cells (HSCs) “live”? Scientists knew that these crucially important cells—responsible for forming the many types of cells found in blood—are found in the bone marrow but didn’t know exactly where. 
Now Paul S. Frenette, M.D., a professor of medicine (hematology) and of cell biology and chair and director of the Ruth L. and David S. Gottesman Institute for Stem Cell and Regenerative Medicine Research, and his colleagues report in an October online edition of Nature that non-dividing HSCs reside in the bone marrow’s small arterial blood vessels (arterioles). (By contrast, the researchers found that proliferating HSCs inhabit another type of blood vessel called sinusoids.)
The researchers found evidence that living inside arterioles keeps HSCs quiescent and protects them from injury. This means that arterioles might also serve as refuges for cancer stem cells.