High doses of CD34 cells from umbilical cord blood, bone marrow and mobilized peripheral blood result in comparable myeloid engraftment in the nod/scid mice

Abstract

Abstract Different engraftment kinetics have been observed after transplantation of bone marrow (BM), G-CSF-mobilized peripheral blood (mPB) and umbilical cord blood (UCB). This may not only result from qualitative but also from qualitative differences in these grafts. We studied the repopulating potential of increasing numbers of CD34 + cells from UCB, BM, and mPB in NOD/SCID mice. CD34 + cells were selected by immunomagnetic cell selection (93 ± 5% purity within life gate). Mice (n = 66) were sublethally irradiated (3.5 Gy) and transplanted with increasing numbers (0.1–4 × 10 6 ) of CD34 + cells isolated from UCB, BM or mPB. After 6–8 weeks the mice were sacrificed and blood, BM, and organs were harvested. Single cell suspensions were made and analyzed by flow cytometry with anti-human CD45, CD34, CD2, CD4, CD8, CD19, CD20, CD14, CD15 and CD33. After transplantation of 0.1-0.3-0.5-0.7 × 10 6 CD34 + BM or mPB cells no engraftment was observed. In contrast, after transplantation of a relatively low dose (0.3 × 10 6 ) of UCB CD34 + cells, 40-85% of cells in the BM of recipient mice were of human origin. Grafts containing more than 1 × 10 6 BM or mPB CD34 + cells resulted in measurable engraftment of human cells (CD45 + ) in the BM. Human cells found in BM of the NOD/SCID mice transplanted with 6 UCB CD34 + cells were mainly of B cell origin (81–97%). After transplantation of ≥1 × 10 6 CD34 + UCB cells, the percentage of B cells in the bone marrow was significantly lower (45–85%) concommittant with an increase in the percentage of myeloid cells (20–55%). A similar ratio between lymphoid and myeloid cells in the bone marrow was observed after transplantation of ≥ 1 × 10 6 CD34 + cells derived from BM or mPB. We suggest that 1). The frequency of early progenitor cells preferentially developing into B cells, is higher in UCB CD34 + transplants than in BM or mPB grafts. 2) The frequency of progenitor cells developing into myeloid cells is similar in CD34 + cell population derived from UCB, BM and mPB.