BACKGROUND Humanized mouse models are still under development, and various protocols exist to improve human cell engraftment and function. METHODS Fourteen NOD/SCID/IL-2Rγnull (NSG) mice (4‒5 wk old) were conditioned with busulfan and injected with human umbilical cord blood (hUCB)-derived CD34(+) hematopoietic stem cells (HSC) via retro-orbital sinuses. The bone marrow (BM), spleen, and peripheral blood (PB) were analyzed 8 and 12 weeks after HSC transplantation. RESULTS Most of the NSG mice tolerated the regimen well. The percentage of hCD45(+) and CD19(+) cells rose significantly in a time-dependent manner. The median percentage of hCD45(+)cells in the BM was 55.5% at week 8, and 67.2% at week 12. The median percentage of hCD45(+) cells in the spleen at weeks 8 and 12 was 42% and 51%, respectively. The median percentage of hCD19(+) cells in BM at weeks 8 and 12 was 21.5% and 39%, respectively (P=0.04). Similarly, the median percentage of hCD19(+) cells in the spleen at weeks 8 and 12 was 10% and 24%, respectively (P=0.04). The percentage of hCD19(+) B cells in PB was 23% at week 12. At week 8, hCD3(+) T cells were barely detectable, while hCD7(+) was detected in the BM and spleen. The percentage of hCD3(+) T cells was 2‒3% at week 12 in the BM, spleen, and PB of humanized NSG mice. CONCLUSION We adopted a simplified protocol for establishing humanized NSG mice. We observed a higher engraftment rate of human CD45(+) cells than earlier studies without any significant toxicity. And human CD45(+) cell engraftment at week 8 was comparable to that of week 12.

The effector potential of NK cells is counterbalanced by their sensitivity to inhibition by self" MHC class I molecules in a process called "education." In humans�

Umbilical cord blood (CB) represents a main source of circulating endothelial progenitor cells (cEPCs). In view of their clinical use, in either the autologous or allogeneic setting, cEPCs should likely be expanded from CB kept frozen in CB banks. In this study, we compared the expansion, functional features, senescence pattern over culture, and in vivo angiogenic potential of cEPCs isolated from fresh or cryopreserved CB (cryoCB). cEPCs could be isolated in only 59% of cryoCB compared to 94% for fresh CB, while CB units were matched in terms of initial volume, nucleated and CD34(+) cell number. Moreover, the number of endothelial colony-forming cells was significantly decreased when using cryoCB. Once cEPCs culture was established, the proliferation, migration, tube formation, and acetylated-LDL uptake potentials were similar in both groups. In addition, cEPCs derived from cryoCB displayed the same senescence status and telomeres length as that of cEPCs derived from fresh CB. Karyotypic aberrations were found in cells obtained from both fresh and cryoCB. In vivo, in a hind limb ischemia murine model, cEPCs from fresh and cryoCB were equally efficient to induce neovascularization. Thus, cEPCs isolated from cryoCB exhibited similar properties to those of fresh CB in vitro and in vivo. However, the low frequency of cEPCs colony formation after cryopreservation shed light on the need for specific freezing conditions adapted to cEPCs in view of their future clinical use.