[Hematopoietic stem cell grafts.]

The number of stem cell transplantations have greatly increased in the treatment of primary bone marrow disorders and as a rescue therapy following highdose chemoradiofherapy for various malignancies. Hematopoietic stem cells can be mobilized from bone marrow by hematopoietic growth factors enabling their sampling from peripheral blood. Peripheral blood stem cell transplantation is gradually replacing autologous bone marrow transplantation and is increasingly used in allogeneic settings. Transplantation using umbilical cord blood derived stem cells are also well described.

To standardize the in vitro methods necessary for the evaluation of stem cell grafts using umbilical cord blood mononuclear cells.

Mononuclear cells (MNC) were isolated from 57 umbilical cord blood samples. The proportion of hematopoietic stem cells (CD34+) was determined by flow cytometry. The number of clonogenic cells (BFU-E, CFU-GM) was determined by culturing MNC in methylcellulose and agar. The number of clonogenic cells was compared before and after freezing in liquid nitrogen.

The mean volume of collected cord blood was 43.8 ml and the number of MNC's was 102.7x10" cells of which 0.93% were CD34+. The number of CFU-GM was 23 8/105 MNC and BFU-E 506/105 MNC. After freezing and thawing the MNC, the viability was 94.9% and the number of clonogenic cells was slightly decreased when compared to prefreezing values, the difference being not statistically significant. The purity of CD34+ cells after selection with magnetic beads was over 95%.

In vitro methods, neccessary for evaluation of hematopoietic stem cell grafts, have been standardized using umbilical cord blood derived stem cells.