Blood Stem Cells
A small number of hematopoietic stem cells circulate in the bloodstream. These cells have the same properties as bone marrow stem cells and can be used as a substitute.
The circulating blood stem cells can be obtained from drawn blood, a less-invasive procedure than collecting bone marrow cells. Because they are few in number, however, collecting enough of them can be difficult.
![A syringe is used to withdraw blood from a woman’s arm and the cells are placed in a dish.](images/stem-cell-based-therapies-03.png)