Patients with leukemia, certain autoimmune diseases and genetic defects such as sickle-cell anemia can be treated with blood stem cells either from a donor's bone marrow or from cord blood - but the supply of effective stem cells often runs short.
Now, researchers in the lab of Whitehead Member Harvey Lodish have found a way to multiply in culture adult hematopoietic (blood- forming) stem cells from human cord blood 20-fold, a major milestone that offers promise for bone marrow transplants and perhaps even gene therapy. Cord blood can be easily collected and stored as a frozen product, making it readily available.
“Human cord blood is a rich source of stem cells, but offers too few of those cells to transplant into an adult,” says Lodish. “Previously we identified five growth factors that acting together in culture expanded mouse bone marrow hematopoietic stem cells 30-fold. Building on this research we've now identified five growth factors needed to stimulate human cord blood stem cells to divide in culture and make 20-fold as many stem cells.” The paper was pre-published online in Blood on January 17, 2008.
Two novel growth factors (angiopoietin-like 5 and IGFBP2) work in combination with three previously identified growth hormones (SCF (Stem Cell Factor), TPO (Thrombopoietin) and Flt3 ligand to stimulate the growth of these stem cells.
Known as hematopoietic stem cells, the cells give rise to oxygen-carrying red blood cells, white blood cells, and all of the cells that comprise the immune system. Previous efforts to grow human hematopoietic stem cells in culture have proven extraordinarily difficult because they rapidly differentiate into mature blood or immune cells.
“Our finding builds on previous work studying hematopoietic cells in which we discovered a novel cell population that when cultured in a dish with stem cells enabled them to multiply,” says Chengcheng Zhang, first author of the paper, formerly a postdoctoral researcher in the Lodish lab and now an assistant professor of physiology and developmental biology at the University of Texas Southwestern Medical Center in Dallas. “We searched for genes that were active in these and other stem cell supportive cells, and identified genes that encoded growth factors. We then added the growth factors to the isolated hematopoietic stem cells and increased the number of stem cells in culture.”