Proliferation and Differentiation of Myeloid

Endothelial cells are a major component of the bone marrow (BM) microenvironment that regulate the trafficking and homing of hematopoietic progenitor and stem cells. In this paper, we provide evidence that BM endothelial cells (BMECs) also support multilineage hematopoiesis by elabo-ration of soluble cytokines. Hematopoietic progenitor cells incubated in direct contact with BMEC monolayers, or physi-cally separated by microporous membrane, expanded five-fold to sevenfold at 7 days, in the absence of exogenous cytokines. Plow cytometric analysis of proliferating progeni-tor cells grown in the presence of BMEC monolayers showed that by day 14 of coculture, 70 % to 80 % of hematopoietic cells were myeloid, expressing CD15 or CD14, and 14 % to HE BONE MARROW (BM) microenvironment is a complex three-dimensional structure where hemato