Quantitative immunophenotypic characterization, cryopreservation, and enrichment of second- and third-trimester human fetal cord blood hematopoietic stem cells (progenitor cells)

OBJECTIVE: The aims of this study were (1) to assess the hematopoietic stem cell (progenitor cell) contents of umbilical cord blood samples from second-trimester and early-third-trimester fetuses versus term fetuses and (2) to determine the feasibility of cryopreservation and enrichment of cord blood from fetuses of different gestational ages. STUDY DESIGN: Cord blood between 13 and 42 weeks' gestation (n = 31) was sampled after delivery or fetal expulsion. Fluorescence-activated cell sorting was used to measure CD34(+) and CD34(+)CD38(-) cell numbers. Samples were cryopreserved with 10% dimethylsulfoxide, and CD34(+) enrichment was performed by magnetically activated cell sorting with the MiniMACS system (Miltenyi Biotech, Bergisch Gladbach, Germany). Kruskal-Wallis analysis of variance and the Mann-Whitney U test were used for analysis of data. RESULTS: CD34(+) and CD34(+)CD38(-) cell contents were significantly higher in second- and early third-trimester fetuses than in term fetuses (CD34(+) 2.57% +/- 0.38%, 1.48% +/- 0.31%, and 0.7% +/- 0.13%, respectively, P = .0067; CD34(+)CD38(-) 0.72% +/- 0.26%, 0.18% +/- 0.05%, and 0.06% +/- 0.02%, respectively, P = .0132). Mononuclear cell recovery, viability, and CD34(+) cell purity after cryopreservation and enrichment were similar among different gestational ages. CONCLUSION: Cord blood stem cell content decreases significantly from the second trimester to term. Cryopreservation and enrichment of these cells from earlier gestational ages is feasible. This might be especially useful for allogeneic stem cell transplantation and for in utero gene therapy.