Human umbilical cord blood (CB) has moved from the status of biological waste to that of a valuable source of haematopoietic stem (HS) cells. There are potentially three major clinical applications for HS cells and ex vivo-expanded HS cells: reconstitution of haematopoiesis in patients undergoing chemotherapy; gene therapy (e.g. in thalassaemia, sickle cell anaemia); and large-scale production of mature blood cells. Erythropoiesis is accomplished by highly complex interactions of haematopoietic progenitor cells, stromal cells and cytokines in the bone marrow. Among them, erythropoietin is the principal regulator. Ex vivo cell culture experiments to obtain mature red blood cells were the focus of this study. Attempts to elucidate appropriate medium components and amounts of haematopoietic growth factors were successful: enucleated and haemoglobin-filled erythroid cells were obtained from primitive HS cells. Dimethylsulphoxide (DMSO) was found to be of particular importance as an efficient differentiation inducer. The differentiation process was followed microscopically and by fluorescence-activated cell sorting (FACS). Using the micropipette aspiration technique, the elastic properties of erythroid cells were evaluated as erythropoiesis progressed. Discocyte-like cells, comprising reticulocytes and finally differentiated red blood cells, showed an about ten-fold higher membrane shear modulus compared with control cells.

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