Expression of thrombopoietin by umbilical vein endothelial cells

Current data suggest that the primary source of thrombopoietin (TPO) is the liver. Extra-hepatic sites for TPO production have been demonstrated essentially through the study of the expression of TPO mRNA. In this work, we report that TPO is expressed at low levels by endothelial cells (EC) derived from the umbilical vein (HUVEC). Both TPO mRNA and the protein are expressed and the protein is functional as assessed by biological assay. Expression of TPO by HUVEC may be useful to study the regulation of the production of this cytokine and to understand the apparent specific interactions between mature megakaryocytes and EC in the bone marrow.