QUANTITATIVE IMMUNOPHENOTYPIC CHARACTERIZATION, CRYOPRESERVATION, ANDENRICHMENT OF 2ND-TRIMESTER AND 3RD-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 fe tuses and (2) to determine the feasibility of cryopreservation and enr ichment of cord blood from fetuses of different gestational ages. STUD Y DESIGN: Cord blood between 13 and 42 weeks' gestation (n = 31) was s ampled after delivery or fetal expulsion. Fluorescence-activated cell sorting was used to measure CD34(+) and CD34(+)CD38(-) cell numbers. S amples were cryopreserved with 10% dimethylsulfoxide, and CD34(+) enri chment was performed by magnetically activated cell sorting with the M iniMACS 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 w ere 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). Monon uclear cell recovery, viability, and CD34(+) cell purity after cryopre servation and enrichment were similar among different gestational ages . CONCLUSION: Cord blood stem cell content decreases significantly fro m the second trimester to term. Cryopreservation and enrichment of the se cells from earlier gestational ages is feasible. This might be espe cially useful for allogeneic stem cell transplantation and for in uter o gene therapy.