Chemokines and chemokine receptors in stem cell circulation.

Stem cells are rare, pluripotent, self-renewing cells that give rise to all mature cells during development and adult life. Due to their proliferative capabilities and their ability to home and contribute to the regeneration of damage tissue, stem cells can be transformed into established tumors. Stem cells can function as a double-edged sword--they have the ability to circulate and migrate throughout the developing and mature adult organism, which is essential for their normal function; however, transformed stem cells are also endowed with the machinery to metastasize into various organs. Chemokine and chemokine receptors play a critical role in directing the trafficking of these cells. It is therefore evident that understanding the role of chemokines and their receptors in stem cell circulation is critical for the successful use of these cells in therapy for a wide variety of pathological conditions.