by Jennifer Chain, Ph.D.
Hematopoietic progenitor cells (HPCs) are stem cells that develop into all the cells circulating in the blood—both red and white blood cell types. Red blood cells carry oxygen from the lungs to all the tissues of the body. White blood cells make up the body’s immune system to defend against bacteria, viruses, fungi, parasites, and cancer. HPCs are found in the bone marrow. When they receive specific signals from surrounding cells, they can develop into B cells, NK cells, dendritic cells, macrophages, neutrophils, basophils, eosinophils, or megakaryocytes. In some cases, HPCs migrate out of the bone marrow into the blood and to an organ called the thymus, where they develop into T cells. Although HPCs are primarily found in the bone marrow, they can also be found in very small numbers in the blood of adults. The immune system is still under development in newborn babies, therefore, many HPCs can be found in the blood within the umbilical cord (cord blood). HPCs are easily identified by their expression of a molecule on their surface called CD34. This molecule helps the cells attach to surfaces inside the bone marrow, blood vessels, and the thymus. CD34 also helps scientists isolate HPCs from blood and bone marrow to use for stem cell transplants.
When a patient needs to replenish their immune system after cancer treatment, they will receive a stem cell transplant. These transplants contain HPCs from themselves (if obtained before chemotherapy treatment) or from a typed-matched donor. Historically, only whole bone marrow containing HPCs was used for transplant. Significant advances have been made to the standard bone marrow transplantation technique. First, a drug called Filgrastim is used to stimulate the HPCs to come out of the bone marrow and into the blood. In this case, HPC-rich blood is collected and transplanted. Also, cord blood donated by mothers following the birth of their children is also becoming a reliable source of HPCs for transplant. Since scientists can isolate HPCs by the CD34 molecule on their surface, studies are underway to test the safety and efficacy of transplanting only the HPCs and none of the other immune cells found in the blood and bone marrow.
Oklahoma Blood Institute is assisting in all areas of stem cell transplantation. Oklahoma Blood Institute collects HPC-rich blood products for the National Marrow Donor Program, which is used for typed-match stem cell transplants. Oklahoma Blood Institute is also establishing the first public cord blood bank in Oklahoma to provide another needed source of HPCs for stem cell transplants. It is also participating in a national clinical trial to isolate CD34+ HPCs to be used for transplantation.
In addition to collecting and processing clinical products to be used for stem cell transplants, we are also collecting and processing HPC-rich blood and bone marrow for research projects. Oklahoma Blood Institute is currently recruiting donors for these research projects. If you would like to participate in research by donating blood or bone marrow, sign up at Bio-Linked.org.