[Hematopoietic stem cells: source, indications and perspectives].

The haematopoietic stem cell (HSC) has been first described in the mouse and now identify in human as well. Exposed to a cocktail of growth factor, this HSC can self re-new and/or differentiate into the three lineages we have in the peripheral blood. These HSC are of major importance in the clinics since they can be used for some marrow (or stem cell) transplantation, and lead to the cure of a number of malignant and non malignant hemopathies. We have today three sources of HSC: the bone marrow, the mobilized peripheral blood stem cell and the cord blood. Bone marrow used to be the classical source of HSC after harvesting by aspirations in the iliac crest. However, this approach is now supplanted by the recovery of HSC in peripheral blood using a cell separation after four days of G-CSF administration. These are several advantages of this technique, but the most important one is the more rapid hematopoietic recovery after transplantation, reducing the risk of infection and transfusion. A recent source of HSC is the umbilical cord blood. At the moment of delivery, the cord blood is extremely enriched in HSC due to the migration of these cells from the liver to the bone marrow stroma, where they will persist after birth. We have learned that the marrow stroma display a major role in the regulation of hematopoiesis and the pathogenesis of several malignant hemopathies can be explained by disturbance in the function of stromal cell. We have particularly studied the patho-genesis of chronic lymphocytic leukaemia. We have also observed that a subpopulation of stromal cells, the mesenchymal cells are of major importance in the microenvironment. In addition, the plasticity of these cells is demonstrated in vitro and we have currently a research program investigating its differentiation in neural cells. All these observations bring new promises in the treatment of hemopathies but also in some other neurological degenerative diseases.