Phenotypic characterization of immunomagnetically purified umbilical cord blood CD34+ cells

Humanized mouse model: Hematopoietic stemcell transplantation and tracking using short tandem repeat technology

Introduction

Models of mice carrying a human immune system, so‐called humanized mice, are used increasingly as preclinical models to bridge the gap between model organisms and human beings. Challenges of the humanized mouse model include finding suitable sources for human hematopoietic stem cells (HSC) and reaching sufficient engraftment of these cells in immunocompromised mice.

Methods

In this study, we compared the use of CD34⁺ HSC from cord blood (CB) vs HSC from adult mobilized peripheral blood. Furthermore, we developed a simple and highly specific test for donor identification in humanized mice by applying the detection method of short tandem repeats (STR).

Results

It was found that, in vitro, CB‐derived and adult HSC show comparable purity, viability, and differentiation potential in colony‐forming unit assays. However, in vivo, CB‐derived HSC engrafted to a significantly higher extent in NOD.Cg‐Prkdc^scidIL2rγ^tm1Wjl/SzJ (NSG) mice than adult HSC. Increasing the cell dose of adult HSC or using fresh cells without cryopreservation did not improve the engraftment rate. Interestingly, when using adult HSC, the percentage of human cells in the bone marrow was significantly higher than that in the peripheral blood. Using the STR‐based test, we were able to identify and distinguish human cells from different donors in humanized mice and in a humanized allogeneic transplantation model.

Conclusion

From these findings, we conclude that adult mobilized HSC are less suitable for generating a humanized immune system in mice than CB‐derived cells.

Characteristics of hematopoietic stem cells of umbilical cord blood

Umbilical cord blood collected from the postpartum placenta and cord is a rich source of hematopoietic stem cells (HSCs) and is an alternative to bone marrow transplantation. In this review we wanted to describe the differences (in phenotype, cytokine production, quantity and quality of cells) between stem cells from umbilical cord blood, bone marrow and peripheral blood. HSCs present in cord blood are more primitive than their counterparts in bone marrow or peripheral blood, and have several advantages including high proliferation. With using proper cytokine combination, HSCs can be effectively developed into different cell lines. This process is used in medicine, especially in hematology.

Unique monoclonal antibodies specifically bind surface structures on human fetal erythroid blood cells

BACKGROUND

Continuing efforts in development of non-invasive prenatal genetic tests have focused on the isolation of fetal nucleated red blood cells (NRBCs) from maternal blood for decades. Because no fetal cell-specific antibody has been described so far, the present study focused on the development of monoclonal antibodies (mAbs) to antigens that are expressed exclusively on fetal NRBCs.

METHODS

Mice were immunized with fetal erythroid cell membranes and hybridomas screened for Abs using a multi-parameter fluorescence-activated cell sorting (FACS). Selected mAbs were evaluated by comparative FACS analysis involving Abs known to bind erythroid cell surface markers (CD71, CD36, CD34), antigen-i, galactose, or glycophorin-A (GPA). Specificity was further confirmed by extensive immunohistological and immunocytological analyses of NRBCs from umbilical cord blood and fetal and adult cells from liver, bone marrow, peripheral blood, and lymphoid tissues.

RESULTS

Screening of 690 hybridomas yielded three clones of which Abs from 4B8 and 4B9 clones demonstrated the desired specificity for a novel antigenic structure expressed on fetal erythroblast cell membranes. The antigenic structure identified is different from known surface markers (CD36, CD71, GPA, antigen-i, and galactose), and is not present on circulating adult erythroid cells, except for occasional detectability in adult bone marrow cells.

CONCLUSIONS

The new mAbs specifically bind the same or highly overlapping epitopes of a surface antigen that is almost exclusively expressed on fetal erythroid cells. The high specificity of the mAbs should facilitate development of simple methods for reliable isolation of fetal NRBCs and their use in non-invasive prenatal diagnosis of fetal genetic status.

Immunophenotyping of hematopoietic progenitor cells: Comparison between cord blood and adult mobilized blood grafts

AIM

To study the immunophenotype of hematopoietic progenitor cells from cord blood (CB) grafts (n = 39) in comparison with adult apheresis grafts (AG, n = 229) and pre-apheresis peripheral blood (PAPB) samples (n = 908) using flow cytometry analysis.

METHODS

First, we performed a qualitative analysis of CD34+ cell sub-populations in both CB and PAPB grafts using the standardized ISHAGE protocol and a wide panel of 20 monoclonal antibodies. Next, we studied some parameters, such as the age of mothers and the weight of newborns, which can influence the quality and the quantity of CD34+ cells from CB.

RESULTS

We found that the percentage of apoptotic cells was high in CB in comparison to PAPB (PAPB: 4.6% ± 2.6% vs CB: 53.4% ± 5.2%, P < 0.001). In CB, the weight of newborn and the age of the mother have the influence on CD34+ cells. The follow-up of Ag CD133 in the ISHAGE double platform protocol in association with CD45, CD34 and the 7'AAD shows an equal rate between the two cell populations CD133+CD45+CD34+ high and CD34+CD45+ high with a higher percentage. So, is the inclusion of Ac CD133 necessary in the present panel included in the ISHAGE method? Last part, we showed a significant presence of interferon γ in CB in comparison to PAPB, the annexin showing the high number of apoptotic cells in CB.

CONCLUSION

This study demonstrates that many different obstetric factors must be taken into account when processing and cryo-banking umbilical CB units for transplantation.

When pigs fly: immunomagnetic separation facilitates rapid determination of Pig-a mutant frequency by flow cytometric analysis

In vivo mutation assays based on the Pig-a null phenotype, that is, the absence of cell surface glycosylphosphatidylinositol (GPI) anchored proteins such as CD59, have been described. This work has been accomplished with hematopoietic cells, most often rat peripheral blood erythrocytes (RBCs) and reticulocytes (RETs). The current report describes new sample processing procedures that dramatically increase the rate at which cells can be evaluated for GPI anchor deficiency. This new method was applied to blood specimens from vehicle, 1,3-propane sultone, melphalan, and N-ethyl-N-nitrosourea treated Sprague Dawley rats. Leukocyte- and platelet-depleted blood samples were incubated with anti-CD59-phycoerythrin (PE) and anti-CD61-PE, and then mixed with anti-PE paramagnetic particles and Counting Beads (i.e., fluorescent microspheres). An aliquot of each specimen was stained with SYTO 13 and flow cytometric analysis was performed to determine RET percentage, RET:Counting Bead ratio, and RBC:Counting Bead ratio. The major portion of these specimens were passed through ferromagnetic columns that were suspended in a magnetic field, thereby depleting each specimen of wild-type RBCs (and platelets) based on their association with anti-PE paramagnetic particles. The eluates were concentrated via centrifugation and the resulting suspensions were stained with SYTO 13 and analyzed on the flow cytometer to determine mutant phenotype RET:Counting Bead and mutant phenotype RBC:Counting Bead ratios. The ratios obtained from pre- and post-column analyses were used to derive mutant phenotype RET and mutant phenotype RBC frequencies. Results from vehicle control and genotoxicant-treated rats are presented that indicate the scoring system is capable of returning reliable mutant phenotype cell frequencies. Using this wild-type cell depletion strategy, it was possible to interrogate ≥ 3 million RETs and ≥ 100 million RBCs per rat in approximately 7 min. Beyond considerably enhancing the throughput capacity of the analytical platform, these blood-processing procedures were also shown to enhance the precision of the measurements.

Methods in cell separations

Research in the field of cell biology and biomedicine relies on technologies that fractionate cell populations and isolate rare cell types to high purity. A brief overview of methods and commercially available products currently used in cell separations is presented. Cell fractionation by size and density and highly selective affinity-based technologies such as affinity chromatography, fluorescence-activated cell sorting (FACS) and magnetic cell sorting are discussed in terms of throughput, yield, and purity.

Optimization of immunomagnetic separation for cord blood-derived hematopoietic stem cells

BACKGROUND

There is a growing interest in cord blood as a source of primitive stem cells with the capacity for multilineage differentiation. Pure cell fractions are needed for the characterization and in vitro expansion of stem cells as well as for their use in preclinical research. However, enrichment of stem cells is challenging due to the lack of stem cell-specific markers and gentle protocols for the isolation of highly pure stem cell fractions. Protocols developed for the enrichment of peripheral blood-derived stem cells have been found to be suboptimal for cord blood.

RESULTS

In this study, immunomagnetic cell sorting protocols to purify CD34+, CD133+ and Lin- cells from fresh and cryopreserved cord blood were optimized. Reproducible purities of up to 97% were reached. The selected cells were highly viable having substantial colony-forming potential.

CONCLUSION

The optimized protocols enable rapid enrichment of highly pure hematopoietic stem cells from both fresh and cryopreserved cord blood.

Immunophenotype of hematopoietic stem cells from placental/umbilical cord blood after culture

Identification and enumeration of human hematopoietic stem cells remain problematic, since in vitro and in vivo stem cell assays have different outcomes. We determined if the altered expression of adhesion molecules during stem cell expansion could be a reason for the discrepancy. CD34+CD38- and CD34+CD38+ cells from umbilical cord blood were analyzed before and after culture with thrombopoietin (TPO), FLT-3 ligand (FL) and kit ligand (KL; or stem cell factor) in different combinations: TPO + FL + KL, TPO + FL and TPO, at concentrations of 50 ng/mL each. Cells were immunophenotyped by four-color fluorescence using antibodies against CD11c, CD31, CD49e, CD61, CD62L, CD117, and HLA-DR. Low-density cord blood contained 1.4 +/- 0.9% CD34+ cells, 2.6 +/- 2.1% of which were CD38-negative. CD34+ cells were isolated using immuno-magnetic beads and cultured for up to 7 days. The TPO + FL + KL combination presented the best condition for maintenance of stem cells. The total cell number increased 4.3 +/- 1.8-fold, but the number of viable CD34+ cells decreased by 46 +/- 25%. On the other hand, the fraction of CD34+CD38- cells became 52.0 +/- 29% of all CD34+ cells. The absolute number of CD34+CD38- cells was expanded on average 15 +/- 12-fold when CD34+ cells were cultured with TPO + FL + KL for 7 days. The expression of CD62L, HLA-DR and CD117 was modulated after culture, particularly with TPO + FL + KL, explaining differences between the adhesion and engraftment of primary and cultured candidate stem cells. We conclude that culture of CD34+ cells with TPO + FL + KL results in a significant increase in the number of candidate stem cells with the CD34+CD38- phenotype.

Different steroids co-regulate long-term expansion versus terminal differentiation in primary human erythroid progenitors

Outgrowth, long-term self-renewal, and terminal maturation of human erythroid progenitors derived from umbilical cord blood in serum-free medium can be modulated by steroid hormones. Homogeneous erythroid cultures, as characterized by flow cytometry and dependence on a specific mixture of physiologic proliferation factors, were obtained within 8 days from a starting population of mature and immature mononuclear cells. Due to previous results in mouse and chicken erythroblasts, the proliferation-promoting effect of glucocorticoids was not unexpected. Surprisingly, however, androgen had a positive effect on the sustained expansion of human female but not male erythroid progenitors. Under optimal conditions, sustained proliferation of erythroid progenitors resulted in a more than 10(9)-fold expansion within 60 days. Terminal erythroid maturation was significantly improved by adding human serum and thyroid hormone (3,5,3'-triiodothyronine [T3]) to the differentiation medium. This resulted in highly synchronous differentiation of the cells toward enucleated erythrocytes within 6 days, accompanied by massive size decrease and hemoglobin accumulation to levels comparable to those in peripheral blood erythrocytes. Thus, obviously, different ligand-activated nuclear hormone receptors massively influence the decision between self-renewal and terminal maturation in the human erythroid compartment.

Induction of various immune modulatory molecules in CD34+hematopoietic cells

Lipopolysaccharide (LPS) has been shown to induce proliferation of human T-lymphocytes only in the presence of monocytes and CD34(+) hematopoietic cells (HCs) from peripheral blood. This finding provided evidence of an active role of CD34(+) HCs during inflammation and immunological events. To investigate mechanisms by which CD34(+) HCs become activated and exert their immune-modulatory function, we used the human CD34(+) acute myeloid leukemia cell line KG-1a and CD34(+) bone marrow cells (BMCs). We showed that culture supernatants of LPS-stimulated mononuclear cells (SUP(LPS)) as well as tumor necrosis factor alpha (TauNF-alpha), but not LPS alone, can activate nuclear factor-kappaB in KG-1a cells. By cDNA subtraction and multiplex polymerase chain reaction, we revealed differential expression of cellular inhibitor of apoptosis protein-1, inhibitor of kappaB (IkappaB)/IkappaBalpha (MAD-3), and intercellular adhesion molecule-1 (ICAM-1) in SUP(LPS)-stimulated KG-1a cells and up-regulation of interferon (IFN)-inducible T cell-chemoattractant, interleukin (IL)-8, macrophage-inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, RANTES, CD70, granulocyte macrophage-colony stimulating factor, and IL-1beta in stimulated KG-1a cells and CD34(+) BMCs. Although monokine induced by IFN-gamma, IFN-inducible protein 10, and IFN-gamma were exclusively up-regulated in KG-1a cells, differential expression of monocyte chemoattractant protein-1 (MCP-1), macrophage-derived chemokine, myeloid progenitor inhibitory factor-2, and IL-18 receptor was only detectable in CD34(+) BMCs. More importantly, CD34(+) BMCs stimulated by TNF-alpha also showed enhanced secretion of MCP-1, MIP-1alpha, MIP-1beta, and IL-8, and increased ICAM-1 protein expression could be detected in stimulated KG-1a cells and CD34(+) BMCs. Furthermore, we revealed that T cell proliferation can be induced by TNF-alpha-stimulated KG-1a cells, which is preventable by blocking anti-ICAM-1 monoclonal antibodies. Our results demonstrate that CD34(+) HCs have the potential to express a variety of immune-regulatory mediators upon stimulation by inflammatory cytokines including TNF-alpha, which may contribute to innate- and adaptive-immune processes.

Human stem-progenitor cells from neonatal cord blood have greater hematopoietic expansion capacity than those from mobilized adult blood

OBJECTIVE

In this study we compared the hematopoietic capacity of CD34+ cell preparations from neonatal cord blood (CB) vs adult mobilized peripheral blood (PBSC) before and after ex vivo culture.

METHODS

CD34+ cell preparations purified from CB or PBSC were cultured in serum-free medium containing FKT: FLT-3 ligand (FL), KIT ligand (KL), and thrombopoietin (TPO).

RESULTS

After 1-4 weeks ex vivo culture, CB CD34+ cell preparations had greatly increased numbers of total cells, CD34+ cells, and colony-forming cells (CFC). In contrast, ex vivo-cultured PBSC CD34+ cell preparations generated far less in vitro assessed hematopoietic capacity. Nonobese diabetic severe combined immunodeficient mouse (NOD/SCID) engrafting potential (SEP) was maintained in ex vivo-cultured CB CD34+ cell preparations, whereas ex vivo-cultured PBSC lost SEP. CB CD34+ cells continued to proliferate throughout 3 weeks ex vivo, whereas after 1 week, no additional cell divisions were detected in PBSC CD34+ cells. After 3 weeks in culture, the average CB CD34+ cell had divided more than 5 times, as compared to only 2 times for the average PBSC CD34+ cell.

CONCLUSION

CB CD34+ cell preparations generated massively increased in vitro assessed hematopoietic capacity and maintained SEP during 1- to 4-week ex vivo cultures. In contrast, ex vivo-cultured PBSC CD34+ cell preparations generated far less in vitro assessed hematopoietic capacity and decreased SEP. The differences in the in vitro proliferative indices of membrane dye-labeled CD34+ cells from CB vs PBSC correlated with these functional differences.

Both CD34+38+ and CD34+38- cells home specifically to the bone marrow of NOD/LtSZ scid/scid mice but show different kinetics in expansion

Human hemopoietic stem cells (HSC) have been shown to engraft, differentiate, and proliferate in the hemopoietic tissues of sublethally irradiated NOD/LtSZ scid/scid (NOD/SCID) mice. We used this model to study homing, survival, and expansion of human HSC populations from different sources or phenotype. We observed that CD34+ cells homed specifically to bone marrow (BM) and spleen, but by 3 days after injection, survived only in the BM. These BM-homed CD34+ cells proliferated intensively and gave rise to a 12-fold, 5.5-fold, and 4-fold expansion in 3 days for umbilical cord blood, adult mobilized peripheral blood, and adult BM-derived cells, respectively. By injection of purified subpopulations, it was demonstrated that both CD34+38+ and CD34+38- umbilical cord blood HSC homed to the BM and expanded. Importantly, kinetics of expansion were different: CD34+38+ cells started to increase in cell number from day 3 onwards, and by 4 wk after injection, virtually all CD34+ cells had disappeared. In contrast, CD34+38- cells remained quiescent during the first week and started to expand intensively from the third week on. In this paper, we have shown that homing, survival, and expansion of stem cells are three independent phenomena important in the early phase of BM engraftment and that kinetics of engraftment differ between CD34+38+ and CD34+38- cells.

A novel protocol that allows short-term stem cell expansion of both committed and pluripotent hematopoietic progenitor cells suitable for clinical use

To obtain long-term engraftment and hematopoiesis in myeloablated patients, the cell population used for hematopoietic reconstitution should include a sufficient number of early pluripotent hematopoietic stem cells (HSCs), along with committed cells from the various lineages. For this purpose, the small subset of CD34+ cells purified from different sources must be expanded ex vivo. Since cytokines may induce both proliferation and differentiation, expansion would provide a cell population comprising committed as well as uncommitted cells. Optimization of HSC expansion methods could be obtained by a combination of cytokines able to sustain renewal of pluripotent cells yet endowed with poor differentiation potential. We used variations of the combinations of cytokines described by Brugger et al. [W. Brugger, S. Heimfels, R. J. Berenson, R. Mertelsmann, and L. Kanz (1995) N. Engl. J. Med. 333, 283-287] and Piacibello et al. [W. Piacibello, F. Sanavio, L. Garetto, A. Severino, D. Bergandi, J. Ferrario, F. Fagioli, M. Berger, and M. Aglietta (1997) Blood 89, 2644-2653] to expand UCB CD34+ cells and monitored proliferation rate and phenotype after 14 days of culture. Several hematopoietic lineage-associated surface antigens were evaluated. Our data show that flt3L and thrombopoietin in combination with IL-3, while sustaining a high CD34+ proliferation rate, provide a relatively low enrichment in very early uncommitted CD34+/CD38- cells. Conversely, in the absence of IL-3, they are less effective in inducing proliferation yet significantly increase the number of CD34+/CD38- cells. A combination of the above protocols, applied simultaneously to aliquots of the same sample, would allow expansion of both committed and pluripotent HSC. This strategy may represent a significant improvement for clinical applications.

Umbilical cord blood transplants

With the establishment of cord blood banks, the number of related and unrelated umbilical cord blood transplants is increasing worldwide. Close links have been established with the cord blood banks. Available data showed that umbilical cord blood transplants offer overall results comparable to those obtained with related or unrelated bone marrow transplants. Several differences were found: engraftment with cord blood was delayed, resulting in an increased incidence of early transplant complications, and the incidence of acute and chronic graft-versus-host disease was significantly reduced with cord blood grafts, even in HLA-mismatched transplants and in adults. In patients with leukemia, the rate of relapse appeared to be similar to that documented in bone marrow transplant recipients. These data confirm the potential benefit of using umbilical cord blood hematopoietic stem cells for allogeneic transplants.

Fetal bone marrow as a source of stem cells for in utero or postnatal transplantation

We examined the potential of human fetal bone marrow (FBM) as a source of haematopoietic stem cells for transplantation. The median number of cells obtained between 20 and 24 weeks' gestation was 1.9 x 109 and a median 1.17 x 108 of these cells expressed CD34. Flow cytometry was also used to estimate the content of three different candidate stem cell populations in the tissues older than 20 weeks' gestation. A median 8.8 x 105 CD34++CD38- cells, 1.37 x 106 CD34++CD4+ cells and 2.20 x 106 CD34++CD90+ cells were detected. The content of colony-forming units culture (CFU-C) in the FBM ranged from 2.8 x 104 to 6.0 x 106 per fetus. The CFU-C content could be expanded 50-fold by culture for 1 week in serum-deprived medium and the growth factors kit ligand and granulocyte-macrophage colony-stimulating factor. Positive selection of FBM CD34+/++ cells was achieved using the Baxter Isolex 50 device. An average purity of 82% and yield of up to 19% of CD34+/++ cells was achieved. T cells were depleted by 99.84%. Analysis of candidate stem cell populations and primitive CFU-C suggested a preferential enrichment of these cells over the total population of CD34+/++ cells. All FBM samples were found to be free of microbial contamination at the time of harvest and after selection of CD34+/++ cells. Thus, FBM is a safe source of stem cells. The large number of progenitors and candidate stem cells that can be obtained from FBM makes it suitable for in utero and possibly postnatal transplantation.