Stem cells for regenerative medicine--biological attributes and clinical application.

The place of stem cells in the therapeutic armamentarium is currently subject to intense scrutiny. One issue is the nature of the stem cells themselves, and their relationship to better-known stem cells, such as hematopoietic stem cells. Here it is argued that the stem cells we propose for therapeutic application may be more closely related to embryonic cells than are hematopoietic stem cells. A second issue is how the stem cells may best be manipulated for therapeutic use; this includes stem cell purification, amplification, fate selection, and suitability for clinical use.