Graduate Studies Faculty
William H. Fleming, M.D., Ph.D.
Programs:Cell & Developmental Biology
Program in Molecular & Cellular Biosciences
Research Interests:Hematopoietic stem cells, leukemia stem cells, angiogenesis
Preceptor RotationsDr. Fleming has not indicated availability for preceptor rotations at this time.
Faculty MentorshipDr. Fleming has not indicated availability as a mentor at this time.
Over the past several years, my laboratory has been interested in functional relationship between hematopoiesis and blood vessel formation. Recently, we have found that adult vascular endothelial cells are an important component of the hematopoietic microenvironment. Specifically, endothelial cells can produce signals that protect hematopoietic stem cells (HSCs) from radiation induced cell death. Classical studies in embryology demonstrated the existence of the hemangioblast, a stem cell that can give rise to both hematopoiesis and blood vessels. To address the question of whether bone marrow derived cells with hemangioblast activity exist in the adult, the vascular compartment of bone marrow transplanted mice and humans was carefully evaluated for the presence of donor derived cells. A similar frequency of bone marrow derived endothelial cells was detected in both mouse and human transplant recipients. A single HSC can give rise to both hematopoietic and endothelial cells in vivo providing direct evidence for the existence of an adult hemangioblast. Additional studies demonstrate that endothelial cells can arise from hematopoietic progenitors cells committed to the myelomonocytic cell lineages. These functional interactions between HSCs and blood vessels represent a new area of investigation that has important implications for our understanding of both normal and malignant hematopoiesis.