Identification of haemopoietic stem cells

Stem cells: From embryology to cellular therapy? An appraisal of the present state of art

ABTRACT: A series of publications has dealt in the last years with topics as the isolation, properties and applications of animal stem cells (Weissman 2000. Cell 100: 157-168; Weissman 2002. N. Engl. J. Med. 346: 1567-1579; Lovell-Badge 2001. Nature 414: 88-91; Marshak et al. 2001. Stem Cell Biology. Cold Spring Harbor Laboratory Press, New york; Eridani 2002. J. Roy. Soc. Med. 95: 5-8; Borge and Evers 2003. Cytotechnology 41: 59-68; Sgaramella 2003. Cytotechnology 41: 69-73), however, the bonanza of experimental data recently accumulating have raised such an amount of controversial views and discussions that time perhaps has come for a reassessment of the basic facts in this peculiar area of research and an evaluation of possible, not unrealistic, implications.

Versatile stem cells, young and old. A review

Both embryonic and somatic stem cells have been studied in recent years with particular regard to their differentiation potential. In vitro studies allow a considerable amplification of such cells in culture as well as the induction of commitment in different directions under proper stimulating factors. Moreover, a surprising versatility has been discovered,which makes possible a ;reprogramming' of stem cells into a lineage pathway which may be completely different from the expected direction: for instance, a production of brain cells from blood progenitors has been obtained. It is thus possible to envisage methods of producing in culture sufficient amounts of stem cells, committed to a certain pathway, which can be transplanted in vivo to replace damaged tissues and organs.

Cytokine effect on ex vivo expansion of haemopoietic stem cells from different human sources

Human pluripotential stem cells (PSC) are currently the target for transplantation attempts and genetic manipulation. We have therefore investigated the frequency and the expansion potential of PSC's in different types of blood samples. CD 34+ cells were thus obtained from human bone marrow (BM), as well as from peripheral blood (PB) and cord blood (CB) samples. After immuno-magnetic separation the highest yields of CD 34+ cells were from BM (1.08-2.25%) and CB (0.42-1.32%) while PB samples gave much lower values. Suspension cultures of PSC's from the three sources were then set up, in the presence of combinations of haemopoietic growth factors. A remarkable amplification of the nucleated cell pool was observed reaching a maximum between 10 and 15 days of culture; earliest and maximum expansion (up to 220-fold) was achieved when Erythropoietin (Epo) was added to the culture medium, but this resulted in reduction of colony-forming cells and differentiation into erythroid progenitors. Clonogenic tests for BFU-E's derived colonies showed a peak value at 5 days of liquid culture. Further studies are advisable to establish the best cytokine combination for a valuable ex vivo expansion, coupled with preservation of stem cell properties.