What is GCSF and its relevance to Stem Cells?

A fellow blogger asked me what GCSF is in a previous entry. Sorry I didn't clarify before, please see my explanation below.
GCSF = human Granulocyte Colony Stimulating Factor (several manufacturers but product marketed by Amgen is Neupogen*)

GCSF is a growth factor or a cytokine (body's signal) which is produced naturally in the human body by different tissues to stimulate the bone marrow to produce white blood cells. In the process, blood progenitor cells are also mobilized (moved) into the circulating blood stream.

It is already well understood that mobilized blood progenitor cells are able to engraft (stick to marrow and re- grow) rapidy in patients given high dose chemotherapy and thus restore the blood system in its entirety. These mobilized stem cells have been shown to be transplantable and maintain their function with the same proliferative potential as stem cells from the bone marrow.

Thus, instead of bone marrow harvesting (requires operation suite) to collect stem cells, patients can now undergo stimulation by GCSF and harvest their stem cells safely via an arm vein. This has enabled much greater convenience for stem cell donors worldwide to collect stem cells for their own present (or future use) or to donate to someone in need.

*NEUPOGEN® is indicated for the mobilization of hematopoietic progenitor cells into the peripheral blood for collection by leukapheresis. Mobilization allows for the collection of increased numbers of progenitor cells capable of engraftment compared with collection by leukapheresis without mobilization or bone marrow harvest. After myeloablative chemotherapy‚ the transplantation of an increased number of progenitor cells can lead to more rapid engraftment‚ which may result in a decreased need for supportive care.