Pattern of cytokine expression by rat liver epithelial cells supporting long-term culture of human CD34(+) umbilical cord blood cells

Fetal liver is the main site of haematopoiesis during mid-gestation. The ad ult liver still provides a favourable environment for extramedullary haemat opoiesis, Nevertheless, regulation of liver haematopoiesis by cell-cell con tacts or by cytokines remains poorly understood. Recently, me have shown th at rat liver epithelial cells (RLECs) support long-term survival and multil ineage differentiation of adult human CD34(+) and CD34(+)/CD38(-) haematopo ietic cells obtained from granulocyte-colony stimulating factor mobilized p eripheral blood and from bone marrow respectively, In addition, the importa nce of physical proximity between haematopoietic cells and RLECs mas clearl y demonstrated. Here, our findings give evidence that RLECs belonging to th e epithelial but non-parenchymal liver compartment also sustain the long-te rm production of progenitors from human CD34(+) umbilical cord blood cells, Moreover, to better analyse the regulation of haematopoiesis in this RLEC coculture model, we have investigated the cytokine expression by RLECs alon e and by RLECs coming from coculture with CD34(+) cells from umbilical cord blood. We demonstrated that a broad spectrum of cytokines acting at differ ent stages of haematopoiesis is produced by RLECs. Interestingly, an upregu lation of leukemia inhibitory factor expression by RLECs in presence of CD3 4(+) haematopoietic cells was observed. These data suggest an important rol e of cell-cell interactions in the regulation of haematopoiesis. (C) 2000 A cademic Press.