Hematopoietic Stem Cells and Hematopoiesis

Clayton Smith, MD


Cancer Control. 2003;10(1) 

In This Article

Abstract and Introduction

Background: The highly orchestrated process of blood cell development and homeostasis is termed "hematopoiesis." Understanding the biology of hematopoietic stem cells as well as hematopoiesis is important to developing improved treatments for hematologic malignancies, congenital disorders, chemotherapy-related cytopenias, and blood and marrow transplants.
Methods: The author reviews the current state of the art regarding hematopoietic stem cells and hematopoiesis.
Results: Several new concepts, including stem cell plasticity, suggest the possibility that stem cells may have the ability to differentiate into other tissues in addition to blood cells.
Conclusions: While much is known about hematopoietic stem cells and hematopoiesis, much remains to be clarified about the environmental and genetic processes that govern the growth and development of the blood system. In addition, careful studies remain to be conducted to determine whether hematopoietic stem cells can differentiate into extra-hematopoietic tissues.

Each day the human body produces billions of new white blood cells, red blood cells, and platelets to replace blood cells lost to normal cell turnover processes as well as to illness or trauma. A variety of homeostatic mechanisms allow blood cell production to respond quickly to stresses such as bleeding or infection and then return to normal levels when the stress is resolved. The highly orchestrated process of blood cell production and homeostasis is termed hematopoiesis. An understanding of the principal mechanisms in hematopoiesis, as well as our current understanding of the processes central to hematopoiesis, is important to the practice of oncology for a variety of reasons. Disorders of hematopoiesis underlie a number of hematologic malignancies and other disorders such as leukemia, aplastic anemia, lymphoma, myelodysplasia, myeloproliferative disorders, and inborn errors of metabolism. Chemotherapy-induced cytopenia is one of the primary causes of morbidity and mortality in the treatment of cancer.

Studying the biology of hematopoiesis has identified several growth factors, including G-CSF and GMCSF, that may shorten the period of posttreatment neutropenia and may improve treatment outcomes. Under-standing the biology of hematopoiesis and the regeneration of immunity may result in decreased morbidity, mortality, and expense of autologous and allogeneic blood and marrow transplants. Delineating the processes that control hematopoiesis may also point the way to developing conditions that expand the numbers of blood cells available for transplant. This could lead to safer and simpler transplants for patients with a variety of cancers and other diseases.