By Levi Clancy for Student Reader on
Stem cell enrichment is an experimental technique developed by Stanford's Dr. Weissman and his colleagues to isolate stem cells from bone marrow tissue.
They developed antibodies that were specific for differentiation antigens present on mature white and red blood cells but not present on stem cells. After soaking bone marrow tissue with these antibodies, flow cytometry isolated stem cells (which did not fluoresce). Remaining cells were soaked with antibodies specific for differentiation antigens present on cells in the early stages of hematopoiesis, followed by flow cytometry to remove such cells. Next, cells treated with an antibody for stem cell antigen 1 (Sca-1) that allowed isolation of the most undifferentiated stem cells.
As few as 30 to 100 of these highly purified stem cells can restore hematopoiesis (and therefore viability) in mice treated with radiation to kill all of their stem cells. H. Nakauchi refined this procedure, creating a technique so effective that a single stem cell enriched from bone marrow can restore both myeloid and lymphoid lineages. On a similar note, CD34 is a marker found on stem cells (and other cells); inoculating an irradiated mouse with a culture enriched for CD34 cells can restore hematopoiesis.