Reconstitution of Human Immune Cells with Co-transplantation of Fetal Liver/Thymus Tissues and Cultured Umbilical Cord Blood-derived Hematopoietic Stem Cells in Rag2(-/-)gamma(c)(-/-) Mice

ABSTRACT

PURPOSE: Many researchers have tried to develop animal models that mimic the human immune system, e.g. a humanized mouse model, to improve the engraftment of hematopoietic stem cells and develop human immune cells in an animal model. This study evaluated the feasibility of the cultured human umbilical cord blood (hUCB)-derived CD34(+) cells for cell expansion, in Rag2(-/-)gamma(c)(-/-) mice, and establish co-transplantation with human fetal thymus/liver tissue (Thy/Liv) under the kidney capsule. METHODS: Co-transplantation of hUCB-derived CD34(+) cells with Thy/Liv was performed. The hUCB-derived CD34(+) cells were prepared by freshly thawing (G1) and culturing for 7 days with two types of cytokine combinations (G2, G3). The CD45(+) cell populations were measured at 6, 8, 10 and 16 weeks in the peripheral blood. The splenocytes were cultured with mitogenic stimuli (PHA -L or IL-2) at 20 weeks post- transplantation, and the proliferation of human immune cells was evaluated. RESULTS: There were no significant differences in the human CD45(+) cell populations at 6, 8, 10 and 16 weeks post-transplantation between the groups. In the cultured splenocytes at 20 weeks post-transplant with PHA-L or IL-2, there was remarkable expansion of CD3(+) cells in the three groups. Although no CD19(+) cells were detected in the spleen, human Ig G was detected in the sera of these mice. CONCLUSION: The cultured and expanded hUCB-derived cells with cytokine combinations might be a feasible cell source in humanized mouse modeling. In addition, human immune cells can be reconstituted from the co-transplantation of Thy/Liv and cultured hUCB-derived CD34(+) cells.