Expansion ex vivo des cellules hematopoiétiques : concept et utilité clinique

A new discipline was born and grew up over the last 4 decades of 20th century: Experimental Hematology. In addition to yield the concept of Stemness, a paradigm later applied for the other tissues than hematopoietic one, it provided the results allowing a preclinical development and a therapeutic exploitation. The concept of ex vivo expansion of hematopoietic cells for transplantation is directly issued from this knowledge. It enabled us to realize that a critical quantity of different sub-populations of stem and progenitor cells are necessary to obtain a rapid and sustained hematopoietic reconstitution. These principles, transposed to human cells (originating from: bone marrow, peripheral blood, cord blood) required some important technological innovations (conception of the specific media, recombinant technology of cytokine production...), to achieve, after several attempts, the first efficient clinical trials (at the moment for cells mobilized in peripheral blood). This goal remains to be achieved for cord blood cells too. The developments in this field as well as its actual state are the subjects of this review.