Comparative in vitro analysis of different hematopoietic cell populations from human cord blood: in search of the best option for clinically oriented ex vivo cell expansion

BACKGROUND: Ex vivo expansion of hematopoietic stem and progenitor cells has become a priority in the experimental hematology arena. In this study we have obtained different hematopoietic cell populations from umbilical cord blood and simultaneously assessed their proliferation and expansion kinetics. Our main goal was to determine which one of these cell populations would be more suitable for clinical-grade ex vivo expansion. STUDY DESIGN AND METHODS: By using immunomagnetic-negative selection and cell sorting, five cell populations were obtained: unseparated mononuclear cells (MNCs; I); two lineage-negative cell populations, one enriched for CD34+ CD38+ cells (II) and the other enriched for CD34+ CD38 cells (III); and two CD34+ cell fractions purified by fluorescence-activated cell sorting, one containing CD34+ CD38+ cells (IV) and the other containing CD34+ CD38 cells (V). The kinetics of such populations were analyzed in both relative and absolute terms. RESULTS: No expansion was observed in Population I; in contrast, significant increments in the numbers of both progenitor and stem cells were observed in cultures of Populations II to V. Population V (reaching 12,800-fold increase in total cells; 1280-fold increase in CD34+ cells; 490-fold increase in colony-forming cells; and 12-fold increase in long-term cultureinitiating cells) showed the highest proliferation and expansion potentials. CONCLUSION: Our study suggests that the cell fraction containing greater than 98% CD34+ CD38 cells would be the ideal one for large-scale ex vivo expansion; however, based on our data, it seems that, except for MNCs, all other cell populations could also be used as input cell fractions.