Conditions that enable human hematopoietic stem cell engraftment in all NOD-SCID mice

Background Transplantation of human hematopoietic stem cells is the only tr ue test of their long-term repopulation potential. Models are readily avail able to evaluate murine hematopoietic stem cells, but few exist that allow reliable quantification of human stem cells. The non-obese diabetic-severe combined immunodeficient (NOD-SCID) mouse model enables quantification of h uman hematopoietic stem cells, but the conditions that permit human engraft ment in all animals have yet to be defined. The aims of the project were, t herefore, to describe the variables that allow human engraftment in the NOD -SCID mouse model and the techniques that accurately quantify this engraftm ent, Methods. NOD-SCID mice that had or had not received 250, 325, or 400 cGy ir radiation received cord blood (CB) mononuclear or CD34(+) cells i.v. or i.p , Mice were killed 6 weeks after transplantation, and the bone marrow, sple en, and thymus were harvested. Four-color flow cytometric analysis, semi-qu antitative PCR, myeloid and erythroid progenitor, and stem cell assays were used to monitor human engraftment. Results, A 250 or 325 cGy and i.v, injection of CB mononuclear or CD34(+) c ells is required to detect multilineage human engraftment in the bone marro w, spleen, or thymus of NOD-SCID mice, Four-color flow cytometric analysis and semi-quantitative PCR enable accurate detection of 0.1% human cells. Pr ogenitor and stem cell assays provide functional information about the engr afted cells. Conclusions. Successful development of the NOD-SCID mouse model and techniq ues to assess human. engraftment now allow it to be used reliably to analyz e the effects of short-term cytokine exposure on the long-term repopulating capacity of CB stem cells.