Selection based on CD133 and high aldehyde dehydrogenase activity isolates long-term reconstituting human hematopoietic stem cells

The development of novel cell-based therapies requires understanding of distinct human hematopoietic stem and progenitor cell populations. We recently isolated reconstituting hematopoietic stem cells (HSCs) by lineage depletion and purification based on high aldehyde dehydrogenase activity (ALDH(hi)Lin- cells). Here, we further dissected the ALDH(hi)-Lin- population by selection for CD133, a surface molecule expressed on progenitors from hematopoietic, endothelial, and neural lineages. ALDH(hi)CD133+Lin- cells were primarily CD34+, but also included CD34-CD38-CD133+ cells, a phenotype previously associated with repopulating function. Both ALDH(hi)CD133-Lin- and ALDH(hi)CD133+Lin- cells demonstrated distinct clonogenic progenitor function in vitro, whereas only the ALDH(hi)CD133+Lin- population seeded the murine bone marrow 48 hours after transplantation. Significant human cell repopulation was observed only in NOD/SCID and NOD/SCID beta2M-null mice that received transplants of ALDH(hi)CD133+Lin- cells. Limiting dilution analysis demonstrated a 10-fold increase in the frequency of NOD/SCID repopulating cells compared with CD133+Lin- cells, suggesting that high ALDH activity further purified cells with repopulating function. Transplanted ALDH(hi)CD133+Lin- cells also maintained primitive hematopoietic phenotypes (CD34+CD38-) and demonstrated enhanced repopulating function in recipients of serial, secondary transplants. Cell selection based on ALDH activity and CD133 expression provides a novel purification of HSCs with long-term repopulating function and may be considered an alternative to CD34 cell selection for stem cell therapies.     

Cytokine treatment or accessory cells are required to initiate engraftment of purified primitive human hematopoietic cells transplanted at limiting doses into NOD/SCID mice

Little is known about the cell types or mechanisms that underlie the engraftment process. Here, we have examined parameters affecting the engraftment of purified human Lin-CD34+CD38- normal and AML cells transplanted at limiting doses into NOD/SCID recipients. Mice transplanted with 500 to 1000 Lin-CD34+CD38- cord blood (CB) or AML cells required the co-transplantation of accessory cells (ACs) or short-term in vivo cytokine treatment for engraftment, whereas transplantation of higher doses (>5000 Lin-CD34+CD38- cells) did not show these requirements suggesting that ACs are effective for both normal and leukemic stem cell engraftment in this model. Mature Lin+CD34- and primitive Lin-CD34+CD38+ cells were capable of acting as ACs even though no repopulating cells are present. Cytokine treatment of NOD/SCID mice could partially replace the requirement for co-transplantation of AC. Furthermore, no difference was seen between the percentage of engrafted mice treated with cytokines for only the first 10 days after transplant compared to those receiving cytokines for the entire time of repopulation. Surprisingly, no engraftment was detected in mice when cytokine treatment was delayed until 10 days posttransplant. Together, these studies suggest that the engraftment process requires pluripotent stem cells plus accessory cells or cytokine treatment which act early after transplantation. The NOD/SCID xenotransplant system provides the means to further clarify the processes underlying human stem cell engraftment.     

Engraftment potential into NOD/SCID mice of CD34+ cells derived from human fetal liver as compared to fetal bone marrow

BACKGROUND AND OBJECTIVES: We hypothesized that qualitative or quantitative differences in hematopoietic stem cells from fetal liver (FL) and fetal bone marrow (FBM) may be the cause of their organ specificity. DESIGN AND METHODS: To analyze possible differences in vivo, we compared the engraftment potential of equal numbers of CD34+ cells isolated from human FL or FBM into immunodeficient NOD/SCID mice. RESULTS: Mice showing engraftment following transplantation of CD34+ cells from FL demonstrated 14% (range 2-76%) CD45+ cells of human origin in the bone marrow compared to significantly lower levels of engraftment (4%, range 2-20%, p < 0.04) of FBM CD34+ cells. Likewise, the percentage of CD34+ CD38- cells in FBM was 4 times lower than the percentage in FL (1.4+/-0.9% and 5.6+/-0.7%, respectively). Similar organ distribution of engrafted human cells was found. Subset analysis of human cells in bone marrow of engrafted mice revealed identical distribution of the lymphoid, myeloid and erythroid lineages after transplantation of CD34+ cells from FL or FBM. INTERPRETATION AND CONCLUSIONS: The FL CD34+ cells showed a four-fold higher content of the CD34+ CD38- subset coinciding with a four-fold higher engraftment of CD34+ cells into NOD/SCID mice. Since the organ distribution and differentiation potential of the cells engrafted were similar, we concluded that CD34+ hematopoietic cells derived from FL and FBM have quantitatively different, but qualitatively the same potential for engraftment into NOD/SCID mice.     

Behavior of CD34+ cells isolated from patients with polycythemia vera in NOD/SCID mice

OBJECTIVE: We investigated if polycythemia vera (PV) peripheral blood (PB) CD34+ cells contain cells capable of engrafting nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice and if the JAK2V617F mutational burden of these cells alters their behavior in NOD/SCID mice. MATERIALS AND METHODS: CD34+ cells isolated from patients with PV, idiopathic myelofibrosis (IM), or granulocyte colony-stimulating factor-mobilized normal donors were transplanted into sublethally irradiated NOD/SCID mice. Cells engrafted into the NOD/SCID mice were analyzed flow cytometrically using lineage-specific antibodies. Genomic DNA was extracted from granulocytes, CD34+ cells, and sorted human CD45(+) cells purified from the bone marrow cells of these mice to examine their JAK2V617F mutational burdens. RESULTS: Multilineage human cell engraftment was observed in mice transplanted with CD34+ cells from mobilized normal volunteers, IM patients and PV patients with high JAK2V617F burden, but not in mice receiving grafts from PV patients with low JAK2V617F burden. The differentiation program of engrafting PV CD34+ cells with high JAK2V617F burden was remarkably different than that of IM CD34+ cells. The JAK2V617F allele frequency in the human CD45+ cells isolated from the mice receiving CD34+ cells was lower than that observed in the CD34+ cell grafts, indicating the persistence of a JAK2V617F negative compartment of stem cells. CONCLUSION: We conclude that PB CD34+ cells from PV patients with high JAK2V617F burden and patients with IM contain NOD/SCID repopulating cells, and that differentiation program of IM and PV CD34+ cells are dramatically different.     

Reconstitution of human haematopoiesis in non-obese diabetic/severe combined immunodeficient mice by clonal cells expanded from single CD34+CD38- cells expressing Flk2/Flt3

In the present study, we examined the expression of Flk2/Flt3, a tyrosine kinase receptor, on human cord blood CD34+ haematopoietic progenitor/stem cells. In flow cytometric analysis, Flk2/Flt3 was expressed on 80% of CD34+ cells and their immature subpopulations, CD34+CD33- and CD34+CD38- cells. Methycellulose clonal culture of sorted CD34+Flk2/Flt3+ and CD34+Flk2/Flt3- cells showed that most of myelocytic progenitors expressed Flk2/Flt3, but erythroid and haematopoietic multipotential progenitors were shared by both fractions. When 1 x 10(4) lineage marker-negative (Lin-)CD34+Flk2/Flt3- cells were transplanted into non-obese diabetic/severe combined immunodeficient (NOD/SCID) mice, none of the recipients possessed human CD45+ cells in bone marrow 11-12 weeks after the transplantation. In contrast, all recipients transplanted with 1 x 10(4) Lin-CD34+Flk2/Flt3+ cells showed successful engraftment. Furthermore, clonal cells expanded from single Lin-CD34+CD38-Flk2/Flt3+ cells in the culture with Flk2/Flt3 ligand, stem cell factor, thrombopoietin, and a complex of interleukin 6/soluble interleukin 6 receptor were individually transplanted into NOD/SCID mice. At 20 to 21 weeks after the transplantation, three out of 10 clones harvested at d 7 of culture, and three out of six clones at d 14 could reconstitute human haematopoiesis in recipient marrow. These results demonstrated that Flk2/Flt3 was expressed on a wide variety of human haematopoietic cells including long-term-repopulating haematopoietic stem cells.     

Functional characterization of highly purified human hematopoietic repopulating cells isolated according to aldehyde dehydrogenase activity

Human hematopoietic stem cells (HSCs) are commonly purified by the expression of cell surface markers such as CD34. Because cell phenotype can be altered by cell cycle progression or ex vivo culture, purification on the basis of conserved stem cell function may represent a more reliable way to isolate various stem cell populations. We have purified primitive HSCs from human umbilical cord blood (UCB) by lineage depletion (Lin(-)) followed by selection of cells with high aldehyde dehydrogenase (ALDH) activity. ALDH(hi)Lin(-) cells contained 22.6% +/- 3.0% of the Lin(-) population and highly coexpressed primitive HSC phenotypes (CD34(+) CD38(-) and CD34(+)CD133(+)). In vitro hematopoietic progenitor function was enriched in the ALDH(hi)Lin(-) population, compared with ALDH(lo)Lin(-) cells. Multilineage human hematopoietic repopulation was observed exclusively after transplantation of ALDH(hi)Lin(-) cells. Direct comparison of repopulation with use of the nonobese diabetic/severe combined immunodeficient (NOD/SCID) and NOD/SCID beta2 microglobulin (beta2M) null models demonstrated that 10-fold greater numbers of ALDH(hi)-Lin(-) cells were needed to engraft the NOD/SCID mouse as compared with the more permissive NOD/SCID beta2M null mouse, suggesting that the ALDH(hi)Lin(-) population contained committed progenitors as well as primitive repopulating cells. Cell fractionation according to lineage depletion and ALDH activity provides a viable and prospective purification of HSCs on the basis of cell function rather than cell surface phenotype.     

Similar myeloid recovery despite superior overall engraftment in NOD/SCID mice after transplantation of human CD34(+) cells from umbilical cord blood as compared to adult sources

Umbilical cord blood (UCB), bone marrow (BM) and mobilized peripheral blood (mPB) are used as sources of hematopoietic stem cells for transplantation. The NOD/SCID mouse model was used to compare the lineage-specific repopulating potential of CD34(+) cells derived from these sources. Six to 8 weeks after transplantation, blood, BM, spleen, liver and thymus, were harvested, and analyzed by flow cytometry using CD34, CD45, myeloid, and lymphoid lineage-specific antibodies. Fifty percent engraftment of human cells in bone marrow of mice was estimated to be reached with 0.55 x 10(6) CD34(+) UCB cells or with 7.9 x 10(6) CD34(+) cells from adult sources, illustrating a 10-fold superiority of UCB CD34(+) cells to engraft NOD/SCID mice. Lineage-specific characterization of engrafted human cells showed that the high engraftment potential of CD34(+) cells from UCB was due to a preferential B cell development (2-81%). In contrast, comparable percentages of myeloid cells were found following transplantation of CD34(+) cells from UCB, BM and mPB (1-38%), and occurred at significant levels only at relatively high doses. Since the CD34 content of UCB transplants is usually at least one log lower than of transplant from adult sources, these results correspond to the clinical findings with UCB transplantation showing a relatively high overall engraftment, but delayed myeloid recovery.     

Successful transplantation of haploidentically mismatched peripheral blood stem cells using CD133+-purified stem cells

OBJECTIVE: For recipients of haploidentically mismatched stem cell allografts, T-cell depletion is mandatory to prevent lethal graft-vs-host disease (GVHD). Prevention of GVHD can be accomplished by negative selection of T cells or positive selection of stem cells. Recently, a new method for positive selection of stem cells was introduced using monoclonal antibodies against CD133 antigen. We report five cases of successful application of immunomagnetic separation of CD133+ stem cells for haploidentically mismatched allogeneic stem cell transplantation. METHODS: Five patients with high-risk hematological malignancies, ages 7 to 63 years old (median, 17 years), underwent peripheral blood stem cell transplantation from haploidentically mismatched related donors. Conditioning protocol was tailored according to patient clinical situation and included combination of treosulfan/fludarabine/thiotepa/melphalan/Mabcampath. Two patients did not get thiotepa. One of them received a protocol that included infusion of 4.4 x 10(7) blood mononuclear cells from the donor (day -9), followed by a combination of fludarabine/cyclophosphamide/busulfex/MabCampath. Separation of CD133+ stem cells was done using CliniMACS with Miltenyi's CD133 reagent. RESULTS: The procedure was well tolerated by all patients. Early 3-lineage engraftment was documented and none exhibited immune-mediated rejection. Time to recovery of absolute neutrophils count above 0.5 x 10(9)/L and 1.0 x 10(9)/L was 10 to 15 days (median, 14) and 11 to 29 days (median, 15), respectively. Time for platelet recovery to values greater than 20 x 10(9)/L and greater than 50 x 10(9)/L ranged from 12 to 25 days (median, 13.5), and from 14 to 34 days (median, 16), respectively. Transplant-related mortality did not occur in any of the patients. CONCLUSION: Our successful pilot trial suggests that positive selection of CD133+ stem cells may be a useful method for safe transplantation with haploidentically mismatched stem cell allografts while avoiding lethal acute and chronic GVHD. Future studies will be required to assess the clinical benefits of stem cell purification with CD133+ in comparison with CD34+ stem cells.     

Human CD34+ cell preparations contain over 100-fold greater NOD/SCID mouse engrafting capacity than do CD34- cell preparations.

OBJECTIVE: The CD34 cell surface marker is used widely for stem/progenitor cell isolation. Since several recent studies reported that CD34(-) cells also have in vivo engrafting capacity, we quantitatively compared the engraftment potential of CD34(+) vs CD34(-) cell preparations from normal human placental/umbilical cord blood (CB), bone marrow (BM), and mobilized peripheral blood (PBSC) specimens, using the nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse model. METHODS: CD34(+) and CD34(-) cell preparations were purified by four different approaches in 14 individual experiments involving 293 transplanted NOD/SCID mice. In most experiments, CD34(+) cells were depleted twice (CD34(=)) in order to obtain efficient depletion of CD34(+) cells from the CD34(-) cell preparations. RESULTS: Dose-dependent levels of human hematopoietic cells were observed after transplantation of CD34(+) cell preparations. To rigorously assess the complementary CD34(-) cell preparations, cell doses 10- to 1000-fold higher than the minimum dose of the CD34(+) cell preparations necessary for engraftment were transplanted. Nevertheless, of 125 NOD/SCID mice transplanted with CD34(-) cell preparations purified from the same starting cells, only six mice had detectable human hematopoiesis, by flow cytometric or PCR assay. CONCLUSIONS: CD34(-) cells provide only a minor contribution to hematopoietic engraftment in this in vivo model system, as compared to CD34(+) cells from the same samples of noncultured human cells. Hematopoiesis derived from actual CD34(-) cells is difficult to distinguish from that due to CD34(+) cells potentially contaminating the preparations.     

Transplantation of a combination of CD133+ and CD34+ selected progenitor cells from alternative donors

Positive selected haematopoietic stem cells are increasingly used for allogeneic transplantation with the CD34 antigen employed in most separation techniques. However, the recently described pentaspan molecule CD133 appears to be a marker of more primitive haematopoietic progenitors. Here we report our experience with a new CD133-based selection method in 10 paediatric patients with matched unrelated (n = 2) or mismatched-related donors (n = 8). These patients received a combination of stem cells (median = 29.3 x 10(6)/kg), selected with either anti-CD34 or anti-CD133 coated microbeads. The proportion of CD133+ selected cells was gradually increased from patient to patient from 10% to 100%. Comparison of CD133+ and CD34+ separation procedures revealed similar purity and recovery of target populations but a lower depletion of T cells by CD133+ selection (3.7 log vs. 4.1 log, P < 0.001). Both separation procedures produced >90% CD34+/CD133+ double positive target cells. Engraftment occurred in all patients (sustained primary, n = 8; after reconditioning, n = 2). No primary acute graft versus host disease (GvHD) >/= grade II or chronic GvHD was observed. The patients showed a rapid platelet recovery (median time to independence from substitution = 13.5 d), whereas T cell regeneration was variable. Five patients are alive with a median follow-up of 10 months. Our data demonstrates the feasibility of CD133+ selection for transplantation from alternative donors and encourages further trials with total CD133+ separated grafts.     

Efficient transduction of human hematopoietic repopulating cells generating stable engraftment of transgene-expressing cells in NOD/SCID mice

In an attempt to develop efficient procedures of human hematopoietic gene therapy, retrovirally transduced CD34(+) cord blood cells were transplanted into NOD/SCID mice to evaluate the repopulating potential of transduced grafts. Samples were prestimulated on Retronectin-coated dishes and infected with gibbon ape leukemia virus (GALV)-pseudotyped FMEV vectors encoding the enhanced green fluorescent protein (EGFP). Periodic analyses of bone marrow (BM) from transplanted recipients revealed a sustained engraftment of human hematopoietic cells expressing the EGFP transgene. On average, 33.6% of human CD45(+) cells expressed the transgene 90 to 120 days after transplantation. Moreover, 11.9% of total NOD/SCID BM consisted of human CD45(+) cells expressing the EGFP transgene at this time. The transplantation of purified EGFP(+) cells increased the proportion of CD45(+) cells positive for EGFP expression to 57. 7% at 90 to 120 days after transplantation. At this time, 18.9% and 4.3% of NOD/SCID BM consisted of CD45(+)/EGFP(+) and CD34(+)/EGFP(+) cells, respectively. Interestingly, the transplantation of EGFP(-) cells purified at 24 hours after infection also generated a significant engraftment of CD45(+)/EGFP(+) and CD34(+)/EGFP(+) cells, suggesting that a number of transduced repopulating cells did not express the transgene at that time. Molecular analysis of NOD/SCID BM confirmed the high levels of engraftment of human transduced cells deduced from FACS analysis. Finally, the analysis of the provirus insertion sites by conventional Southern blotting indicated that the human hematopoiesis in the NOD/SCID BM was predominantly oligoclonal.     

Human multidrug resistance-1 gene transfer to long-term repopulating human mobilized peripheral blood progenitor cells

Mobilized peripheral blood progenitor cells (PBPC) are an attractive target for the retrovirus-mediated transfer of cytostatic drug resistance genes. We analyzed NOD/SCID mouse repopulating CD34+ PBPC from cancer patients following retroviral Transwell transduction in various cytokine combinations with the FMEV-based (Friend-mink cell focus forming/murine embryonic stem cell virus) hybrid vector SF-MDR carrying the human multidrug resistance-1 (MDR1) gene. Five to 10 weeks following transplantation of 2.0 x 10(6) CD34+ PBPC into NOD/SCID mice we observed medium to high levels of human cell engraftment with up to 33%. The extent of vector-marked human cells was assessed by a quantitative real-time polymerase chain reaction (PCR). SF-MDR gene transfer into long-term in vivo repopulating human hematopoietic cells was optimal in the presence of either IL-3/IL-6/SCF/FL or FL/TPO/SCF resulting in three-fold (12.4% +/- 1.7%) or four-fold (16.5% +/- 6.8%) higher average proportions of gene-marked human cells in NOD/SCID mice as compared to IL-3 alone (P < 0.01). In conclusion, we could optimize the engraftment capacity and the retroviral gene transfer to CD34+ PBPC using cocktails of early acting cytokines in combination with the recombinant fibronectin fragment CH-296. Our data suggest that the NOD/SCID model provides a valid assay to estimate the gene transfer efficiency to repopulating human PBPC that may be achievable in clinical autologous transplantation settings.     

Identification of a novel class of human adherent CD34- stem cells that give rise to SCID-repopulating cells

Here we describe the in vitro generation of a novel adherent cell fraction derived from highly enriched, mobilized CD133(+) peripheral blood cells after their culture with Flt3/Flk2 ligand and interleukin-6 for 3 to 5 weeks. These cells lack markers of hematopoietic stem cells, endothelial cells, mesenchymal cells, dendritic cells, and stromal fibroblasts. However, all adherent cells expressed the adhesion molecules VE-cadherin, CD54, and CD44. They were also positive for CD164 and CD172a (signal regulatory protein-alpha) and for a stem cell antigen defined by the recently described antibody W7C5. Adherent cells can either spontaneously or upon stimulation with stem cell factor give rise to a transplantable, nonadherent CD133(+)CD34(-) stem cell subset. These cells do not generate in vitro hematopoietic colonies. However, their transplantation into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice induced substantially higher long-term multilineage engraftment compared with that of freshly isolated CD34(+) cells, suggesting that these cells are highly enriched in SCID-repopulating cells. In addition to cells of the myeloid lineage, nonadherent CD34(-) cells were able to give rise to human cells with B-, T-, and natural killer-cell phenotype. Hence, these cells possess a distinct in vivo differentiation potential compared with that of CD34(+) stem cells and may therefore provide an alternative to CD34(+) progenitor cells for transplantation.     

Hematopoietic capability of CD34+ cord blood cells: a comparison with CD34+ adult bone marrow cells

The characteristics of hematopoietic progenitor and stem cell (HPC/HSC) populations in mammals vary according to their ontogenic stage. In humans, HPC/HSCs from umbilical cord blood (CB) are increasingly used as an alternative to HPC/HSCs from adult bone marrow (BM) for the treatment of various hematologic disorders. How the hematopoietic activity of progenitor and stem cells in CB differs from that in adult BM remains unclear, however. We compared CD34+ cells, a hematopoietic cell population, in CB with those in adult BM using phenotypic subpopulations analyzed by flow cytometry, the colony-forming activity in methylcellulose clonal cultures, and the repopulating ability of these cells in NOD/Shi-scid (NOD/SCID) mice. Although the proportion of CD34+ cells was higher in adult BM than in CB mononuclear cells, the more immature subpopulations, CD34+ CD33- and CD34+ CD38- cells, were present in higher proportions in CD34+ CB cells. Clonal culture assay showed that more multipotential progenitors were present in CD34+ CB cells. When transplanted into NOD/SCID mice. CD34+ adult BM cells could not reconstitute human hematopoiesis in recipient BM, but CD34+ CB cells achieved a high level of engraftment, indicating that CD34+ CB cells possess a greater repopulating ability. These results demonstrated that human hematopoiesis changes with development from fetus to adult. Furthermore, CD34+ CB cells contained a greater number of primitive hematopoietic cells, including HSCs, than did adult BM, suggesting the usefulness of CD34+ CB cells not only as a graft for therapeutic HSC transplantation but also as a target cell population for ex vivo expansion of transplantable HSCs and for gene transfer in gene therapy.     

CD34 expression by murine hematopoietic stem cells mobilized by granulocyte colony-stimulating factor

Controversy has existed about CD34 expression by hematopoietic stem cells. We recently reported that CD34 expression reflects the activation state of stem cells by using a murine transplantation model. It has been generally held that mobilized blood stem cells express CD34.However, it has also been reported that mobilized stem cells and progenitors are in G0/G1 phases of the cell cycle. To address the state of CD34 expression by the mobilized stem cells, we again used the mouse transplantation model. We prepared CD34(-) and CD34(+) populations of nucleated blood cells from granulocyte colony-stimulating factor-treated Ly-5.1 mice and assayed each population for long-term engrafting cells in lethally irradiated Ly-5.2 mice. The majority of the stem cells were in the CD34(+) population. The CD34 expression by mobilized stem cells was reversible because re-transplantation of Ly-5.1 CD34(-) marrow cells harvested from the Ly-5.2 recipients of CD34(+)-mobilized stem cells 8 months posttransplantation revealed long-term engraftment. These results may support the use of total CD34(+) cells in mobilized blood as a predictor for engraftment and CD34 selection for enrichment of human stem cells. (Blood. 2000;96:1989-1993)     

Transplantation of highly purified CD34+ progenitor cells from alternative donors in children with refractory severe aplastic anaemia

Without transplantation from a human leucocyte antigen-identical family donor, refractory severe aplastic anaemia (SAA) has an unfavourable prognosis. Conventional transplantation from a matched unrelated donor carries a high rate of mortality. We transplanted large numbers of highly purified CD34+ cells from matched unrelated (n = 4), mismatched unrelated (n = 4) and mismatched related (n = 1) donors into nine children with refractory SAA. The grafts consisted of granulocyte colony-stimulating factor-mobilized peripheral positively selected CD34+ cells. A median of 15.1 x 106/kg CD34+ stem cells and 11 x 103/kg CD3+ T-lymphocytes were infused. No additional pharmacological graft versus host disease (GVHD) prophylaxis was given. At a median follow-up of 47 (range 37-72) months, eight patients (89%) were in complete remission with >90% donor chimaerism and no evidence of GVHD. One patient died on day +238 as a consequence of GVHD. The use of highly purified mobilized CD34+ stem cells warrants further clinical exploration in children with refractory SAA.     

A large-scale method for T cell depletion: towards graft engineering of mobilized peripheral blood stem cells

We have investigated the feasibility and efficacy of large-scale T cell depletion from granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood stem cells (PBSC). The method is based on the use of a CD3 antibody conjugated to magnetic microbeads and magnetic activated cell sorting (Clinimacs). A total of eight large-scale experiments were performed. In four experiments, CD3(+) T cells were depleted from PBSC obtained from volunteers mobilized with G-CSF whereas, in four experiments, T cells were depleted from PBSC from stem cell donors, in which the CD34(+) stem cells had been removed for allogeneic transplantation by positive selection prior to T cell depletion. The mean number of processed mononuclear cells (MNCs) was 3.3 x 10(10) (range 1.5 x 10(10)-5.1 x 10(10)) with a mean T cell proportion of 35.8% (range 16.7-64.0%). After T cell depletion, the percentage of contaminating T cells was 0.15% (range 0.01-1.01%) with a mean log(10) depletion of 3.4 (range 2.8-4.1). The mean recovery of CD3-negative MNCs after depletion was 76% (range 52-100%). The mean recovery of CD34(+) stem cells in the four evaluable experiments was 82% (range 75-92%). In vitro colony assays and in vivo NOD/SCID repopulation assays showed that this large-scale T cell depletion method has no negative impact on the function of the hematopoietic precursor cells. Therefore, we conclude that this T cell depletion method is a valuable tool for further graft engineering strategies involving mobilized PBSCs.     

Enhanced engraftment of human cells in RAG2/gammac double-knockout mice after treatment with CL2MDP liposomes

OBJECTIVE: The ability of human cells to repopulate the bone marrow of nonobese diabetic immunodeficient mice (NOD/SCID) is commonly used as a standard assay to quantify the primitive human hematopoietic stem cell population. We studied the applicability of the immunodeficient RAG2(-/-)gammac(-/-) double-knockout mouse for this purpose. METHODS: RAG2(-/-)gammac(-/-) mice and NOD/SCID mice were injected intravenously (i.v.) with umbilical cord blood-derived CD34(+) cells and engraftment was quantified by determining the human CD45+ cell chimerism in bone marrow at several time points. RAG2(-/-)gammac(-/-) were pretreated with total-body irradiation and depleted of macrophages in liver, spleen, and bone marrow by i.v. injection of clodronate diphosphonate containing liposomes. RESULTS: We demonstrated that the frequency of chimerism and the level of engraftment in macrophage-depleted RAG2(-/-)gammac(-/-) largely resemble that in NOD/SCID mice. Also similar is the multilineage differentiation pattern in the two mouse strains at 7 weeks after transplantation, with a prominent outgrowth in RAG2(-/-)gammac(-/-) of CD19+ cells (88% +/- 10%). Cells of other lineages were clearly less frequent: 9% +/- 2% myeloid cells and 0.1% +/- 0.1% erythroid cells. As for immature progenitors, 6% +/- 1% of the human cells express the CD34 antigen and 0.4% +/- 0.1% have the CD34+,CD33,38,71(-) phenotype. The presence of human committed progenitors (i.e., CFU-GM/BFU-E) was evident. The persistence of human cells at 4 months after transplantation shows that the RAG2(-/-)gammac(-/-) support long-term maintenance of human hematopoiesis. CONCLUSION: Our findings indicate that macrophage-depleted RAG2(-/-)gammac(-/-) are a suitable model for studying human hematopoiesis including multipotential stem cells, and long-term repopulation.     

The modified International Prognostic Index can predict the outcome of localized primary intestinal lymphoma of both extranodal marginal zone B-cell and diffuse large B-cell histologies

This study aimed to assess the potential of human cord blood (CB) cells to engraft in the xenogenic non-obese diabetic/severe combined immunodeficient (NOD/SCID) mouse model after in vitro expansion culture. We also studied the quality of human haemopoiesis arising from the transplantation of fresh or expanded cells in this model. Cord blood CD34(+) cells were cultured for 3, 7 or 10 d with stem cell factor, Flt3, thrombopoietin, interleukin 3 (IL-3), IL-6 and granulocyte colony-stimulating factor, all at 10 ng/ml in serum-replete conditions. Transplantation of mice with fresh CB containing 3 x 10(4) CD34(+) cells and 1-2 SCID repopulating cells (SRC) resulted in a median of 7.4% (0.4%-76.8%) human engraftment. When mice received the expanded product of 1-2 SRC, the ability to repopulate NOD/SCID mice was maintained even after 10 d of in vitro culture. Serial dilution of the expanded cells suggested that in vitro expansion had increased SRC numbers two- to fourfold. Expanded SRC produced long-term culture-initiating cells, clonogenic cells and CD34(+) cells in the same proportions as fresh cells after successful engraftment. Therefore, expanded SRC were able to differentiate in the same way as fresh SRC. There was a trend towards lower levels of engraftment when d 7 cultured cells were transplanted (median engraftment 0.8%, range 0.0-24.0%) compared with 1-2 fresh SRC. Our data suggest that this is owing to reduced proliferation of cultured cells in vivo. By utilizing limiting numbers of CB SRC, we confirmed that the engraftment potential of SRC in the NOD/SCID model was preserved after in vitro expansion. Furthermore, dilution experiments strongly suggest two- to fourfold expansion of SRC in vitro. These studies are relevant for developing clinical stem cell expansion strategies.     

An assay for long-term engrafting human hematopoietic cells based on newborn NOD/SCID/beta2-microglobulin(null) mice

OBJECTIVE: Of various types of xenograft assays, the use of NOD/SCID mice has been the most popular method for quantitating candidate human stem cells. Limitations of the assay include low levels of engraftment, except when large numbers of cells are injected, and the development of thymic lymphoma, which precluded observation of long-term engraftment. In order to establish an assay that allows long-term in vivo engraftment and higher engraftment levels by a reasonable number of human cells, we tested a model based on "conditioned newborn" NOD/SCID or NOD/SCID/beta2-microglobulin(null) (BMG(null)) mice. MATERIALS AND METHODS: Using human cord blood mononuclear cells, we tested various nonradiation conditioning regimens and cell injection routes. Conditioning with a combination of 5-fluorouracil (5FU) and anti-mouse c-kit blocking antibody (Ack-2) or a combination of busulfan (BU) and cyclophosphamide (CY) and the use of facial vein for the cell injection route yielded the highest levels of multilineage engraftment. RESULTS: At 4-5 months posttransplantation, the median of engraftment level in bone marrow with 5FU/Ack-2 and BU/CY regimens were 0.9% (range: 0.2-40.5%) and 2.1% (range: 0.3-2.4%) in NOD/SCID mice, and 11.3% (range: 0.7-38%) and 14.1% (range: 0.8-52%) in NOD/SCID/BMG(null) mice, respectively. Multilineage engraftment was demonstrated by flow cytometry and by the growth of multilineage colonies in methylcellulose culture. Secondary transplantation of the isolated human CD45(+) cells, also performed at 4-5 months posttransplantation, revealed engraftment at the levels of 1.5 +/- 0.42% at 2 months after secondary transplantation. CONCLUSION: Our assay may provide a quantitative method for analysis of human hematopoietic stem cells.