To achieve high-level human cell engraftment in the xenograft model, TBI as preconditioning has been nearly exclusively used however, the administration of TBI in our facility results in substantial mortality. To further develop this model for gene therapy applications, several remaining issues require further study, including optimal conditioning, HSC source, cell dose, graft composition, and the lack of significant human erythroid output observed to date. When human HSCs are transplanted into these strains after low-dose total body irradiation (TBI), T, B, and NK cells of human origin are easily detectable in the circulation. These mice have no lymphocyte or NK cell activity and demonstrate impaired dendritic cell function. Another similar strain of mice, NOD/Shi-scid/IL2rγ null, with a truncated or complete null γC mutation, has also been reported.
Third-generation NOD/LtSz- scid/IL2Rγ null (NOD/SCID/ IL2Rγ null) mice were subsequently established to overcome these issues. In this strain, efficient human cell engraftment was observed however, human T cells were not detected in high numbers. To reduce residual NK cell activity in recipient xenograft mice, a new strain, the NOD/SCID/β2m null mouse, was established. NOD/SCID mice have long been the standard for xenografting human HSCs, but the remaining natural killer (NK) cell activity interfered with efficient human cell engraftment. HSC xenotransplantation in NOD/SCID mice has proven a useful tool in gaining a better understanding of HSC behavior in vivo. Transplantation of human HSCs into immunodeficient mice has been used as a surrogate HSC assay. The creation of humanized mice that carry partial or complete human physiological systems may overcome some of these obstacles. Large animals model human HSCs activity better, yet they are cumbersome, costly, and outbred, yielding high variability. S TEM C ELLS 2009 27:175–182ĭespite the development of sophisticated in vitro assays for primitive hematopoietic stem cells (HSCs), transplantation assays remain the gold standard for HSC enumeration. This long evasive model should prove valuable for the study of human erythroid cells. When human Tf was administered singly or in combination with anti-CD122 antibody and human cytokines, up to 0.1% human RBCs were detectable in the peripheral blood.
Recipient mouse-derived human HSCs had the capacity to form erythroid colonies in vitro at various time points post-transplant in the presence of human transferrin (Tf). Transfused human red cells persisted in the chimeric mice for up to 3 days an accompanying rise in total bilirubin suggested hemolysis as a contributing factor to their clearance. At 8 weeks, all leukocyte subsets were detected, yet human red blood cells (RBCs) were not observed. CB CD34+ group achieved significantly higher levels of engraftment than mobilized CD34+-enriched peripheral blood (PB CD34+). Beyond 5 weeks, CD34+-enriched products produced and sustained superior engraftment rates compared with unselected grafts (CB CD34+, 65.8% ± 5.35%, vs. Terminally differentiated B and T lymphocytes made up most of the human CD45+ cells observed during the initial 5 weeks post-transplant when unselected cord blood (CB) products were infused, suggesting derivation from existing mature elements rather than HSCs. Busulfan led to dose-dependent human HSC engraftment in NOD/LtSz- scid/IL2Rγ null mice, with marked improvement in survival rates. In this work, we examined the use of parenteral busulfan as an alternative conditioning agent. Xenografting immunodeficient mice after low-dose irradiation has been used as a surrogate human hematopoietic stem cell (HSC) assay however, irradiation requires strict and meticulous animal support and can produce significant mortality rates, limiting the usefulness of this model.
0 kommentar(er)
