Engraftment kinetics of human cord blood and murine fetal liver stem cells following in utero transplantation into immunodeficient mice.

This study was undertaken to evaluate the kinetics of engraftment after in utero transplantation of murine fetal liver and human cord blood stem cells in the nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse model. NOD/SCID fetuses were injected with murine fetal liver or human cord blood CD34+ cells at day 13.5 of gestation. Frequencies of donor cells were analyzed by flow cytometry up to 48 h post transplantation and 4-16 weeks postnatally. Hematopoietic multilineage reconstitution capacity was assessed. Both types of donor cells home rapidly. However, the frequency of human cord blood stem cells rapidly diminished while the murine fetal liver stem cells expanded over time, resulting in multilineage hematopoietic reconstitution. Differences in long-term reconstitution of allogeneic versus xenogeneic donor cells were ascribed to the inability of the human cells to self-renew and differentiate in the fetal mouse environment, demonstrating the limitations of this commonly used xenograph.