Bone Marrow Endothelial Cell-Derived Factors Inhibit the Growth of Marrow CFU-F

The present study investigated the effects of the serum-free conditioned media of the bone marrow endothelial cells on CFU-F for potential mechanisms upon which hematopoiesis may be regulated by them within the bone marrow microenvironment. After obtaining the serum-free conditioned media of human and murine purified bone marrow endothelial cells (hBMEC-CM and mBMEC-CM) in vitro, MW > 10 kD, 3 - 10 kD and < 3 kD components were sifted out from these media by means of serial ultrafiltration. Assays of CFU-F were performed to test the effects of BMEC-CM and their ultrafiltrated components. The results showed that every one of hBMEC-CM, mBMEC-CM and their MW < 3 kD components exerted a suppressive effect on the proliferation of corresponding CFU-F but MW > 10 kD and 3 - 10 kD components. The BMEC-CM and MW < 3 kD components decreased the number as well as the size of CFU-F. There were the markedly negative concentration-dependent relations between the concentrations of MW < 3 kD component and the numbers of CFU-F. These findings suggested that bone marrow endothelial cells in culture could secrete at least a humoral factor (molecular weight less than 3 kD) which has an inhibitory effect on the growth of CFU-F.