RESUMO
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.
Assuntos
Endotélio Vascular/metabolismo , Trombopoetina/metabolismo , Veias Umbilicais/metabolismo , Sequência de Bases , Northern Blotting , Western Blotting , Células Cultivadas , Meios de Cultivo Condicionados , Primers do DNA , Endotélio Vascular/citologia , Humanos , RNA Mensageiro/genética , Trombopoetina/genética , Veias Umbilicais/citologiaRESUMO
CD40 ligand (CD40L)/CD40 interactions play a central role in T-cell-dependent B-cell activation as previously shown by in vitro studies, the phenotype of CD40L knockout mice and the defective expression of CD40L in patients who have X-linked immunodeficiency with hyper-IgM. The distribution of CD40 in cells other than of myeloid and lymphoid lineages has suggested additional functions for this receptor/ligand couple. Here we show that CD40L stimulates myelopoiesis with a noticeable effect on megakaryocytopoiesis in cocultures of hematopoietic progenitor cells and bone marrow stromal cells. These results suggest a mechanism by which T-cell or platelet-associated or soluble CD40L may regulate myelopoiesis. (Blood. 2000;95:3758-3764)
Assuntos
Endotélio Vascular/fisiologia , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/fisiologia , Leucopoese/fisiologia , Glicoproteínas de Membrana/farmacologia , Proteínas de Membrana/biossíntese , Trombopoetina/biossíntese , Animais , Células da Medula Óssea/citologia , Ligante de CD40 , Células COS , Células Cultivadas , Técnicas de Cocultura , Ensaio de Unidades Formadoras de Colônias , Endotélio Vascular/citologia , Feminino , Sangue Fetal/citologia , Células-Tronco Hematopoéticas/efeitos dos fármacos , Humanos , Recém-Nascido , Leucopoese/efeitos dos fármacos , Camundongos , Camundongos Knockout , Gravidez , Veias UmbilicaisRESUMO
Interferon alpha (IFN-alpha) is used to treat chronic myelogenous leukaemia (CML) patients. However, its target(s) remain(s) unknown. One possibility is that there is a differing sensitivity of the leukaemic from the normal colony-forming cell (CFC) compartments to IFN-alpha. Co-cultures of progenitors with stromal cells provide a valuable tool to dissect direct and indirect activities of IFN-alpha. In this study, we have used endothelial cells (EC) as a source of stromal cells. In co-cultures of normal progenitors with EC, IFN-alpha increased the generation of clonogenic cells, mainly via an increased production of flt3 ligand (FL) by EC. In contrast, in co-cultures of CML progenitors with EC, IFN-alpha inhibited the generation of clonogenic cells, mainly by direct inhibition on the progenitors, the up-regulation of FL production by stromal cells being unable to compensate for the direct inhibitory effects of IFN-alpha. These data provide evidence for a differential effect of IFN-alpha on the growth of CML and normal CFC cells in a stromal context and suggest that an alteration in the response of CML progenitor cells to FL is important in the explanation of this differential effect.
