Scientific Resources

Human cord blood (CB)-derived CD133+ cells carry characteristics of primitive hematopoietic cells and proffer an alternative for CD34+ cells in hematopoietic stem cell (HSC) transplantation. To characterize the CD133+ cell population on a genetic level,a global expression analysis of CD133+ cells was performed using oligonucleotide microarrays. CD133+ cells were purified from four fresh CB units by immunomagnetic selection. All four CD133+ samples showed significant similarity in their gene expression pattern,whereas they differed clearly from the CD133- control samples. In all,690 transcripts were differentially expressed between CD133+ and CD133- cells. Of these,393 were increased and 297 were decreased in CD133+ cells. The highest overexpression was noted in genes associated with metabolism,cellular physiological processes,cell communication,and development. A set of 257 transcripts expressed solely in the CD133+ cell population was identified. Colony-forming unit (CFU) assay was used to detect the clonal progeny of precursors present in the studied cell populations. The results demonstrate that CD133+ cells express primitive markers and possess clonogenic progenitor capacity. This study provides a gene expression profile for human CD133+ cells. It presents a set of genes that may be used to unravel the properties of the CD133+ cell population,assumed to be highly enriched in HSCs. View Publication

Although significant advances have been made over the last decade with respect to our understanding of stem cell biology,progress has been limited in the development of successful techniques for clinically significant ex vivo expansion of hematopoietic stem and progenitor cells. We here describe the effect of Notch ligand density on induction of Notch signaling and subsequent cell fate of human CD34+CD38- cord blood progenitors. Lower densities of Delta1(ext-IgG) enhanced the generation of CD34+ cells as well as CD14+ and CD7+ cells,consistent with early myeloid and lymphoid differentiation,respectively. However,culture with increased amounts of Delta1(ext-IgG) induced apoptosis of CD34+ precursors resulting in decreased cell numbers,without affecting generation of CD7+ cells. RNA interference studies revealed that the promotion of lymphoid differentiation was primarily mediated by Delta1 activation of Notch1. Furthermore,enhanced generation of NOD/SCID repopulating cells was seen following culture with lower but not higher densities of ligand. These studies indicate critical,quantitative aspects of Notch signaling in affecting hematopoietic precursor cell-fate outcomes and suggest that density of Notch ligands in different organ systems may be an important determinant in regulating cell-fate outcomes. Moreover,these findings contribute to the development of methodology for manipulation of hematopoietic precursors for therapeutic purposes. View Publication

The coding region determinant-binding protein/insulin-like growth factor II mRNA-binding protein (CRD-BP/IMP1) is an RNA-binding protein specifically recognizing c-myc,leader 3' IGF-II and tau mRNAs,and the H19 RNA. CRD-BP/IMP1 is predominantly expressed in embryonal tissues but is de novo activated and/or overexpressed in various human neoplasias. To address the question of whether CRD-BP/IMP1 expression characterizes certain cell types displaying distinct proliferation and/or differentiation properties (i.e. stem cells),we isolated cell subpopulations from human bone marrow,mobilized peripheral blood,and cord blood,all sources known to contain stem cells,and monitored for its expression. CRD-BP/IMP1 was detected only in cord blood-derived CD34(+) stem cells and not in any other cell type of either adult or cord blood origin. Adult BM CD34(+) cells cultured in the presence of 5'-azacytidine expressed de novo CRD-BP/IMP1,suggesting that epigenetic modifications may be responsible for its silencing in adult non-expressing cells. Furthermore,by applying the short interfering RNA methodology in MCF-7 cells,we observed,subsequent to knocking down CRD-BP/IMP1,decreased c-myc expression,increased IGF-II mRNA levels,and reduced cell proliferation rates. These data 1) suggest a normal role for CRD-BP/IMP1 in pluripotent stem cells with high renewal capacity,like the CB CD34(+) cells,2) indicate that altered methylation may directly or indirectly affect its expression in adult cells,3) imply that its de novo activation in cancer cells may affect the expression of c-Myc and insulin-like growth factor II,and 4) indicate that the inhibition of CRD-BP/IMP1 expression might affect cancer cell proliferation. View Publication

Bone marrow-derived mesenchymal stem cells (MSC) have been defined as primitive,undifferentiated cells,capable of self-renewal and with the ability to give rise to different cell lineages,including adipocytes,osteocytes,fibroblasts,chondrocytes,and myoblasts. MSC are key components of the hematopoietic microenvironment. Several studies,including some from our own group,suggest that important quantitative and functional alterations are present in the stroma of patients with myelodysplasia (MDS). However,in most of such studies the stroma has been analyzed as a complex network of different cell types and molecules,thus it has been difficult to identify and characterize the cell(s) type(s) that is (are) altered in MDS. In the present study,we have focused on the biological characterization of MSC from MDS. As a first approach,we have quantified their numbers in bone marrow,and have worked on their phenotypic (morphology and immunophenotype) and cytogenetic properties. MSC were obtained by a negative selection procedure and cultured in a MSC liquid culture medium. In terms of morphology,as well as the expression of certain cell markers,no differences were observed between MSC from MDS patients and those derived from normal marrow. In both cases,MSC expressed CD29,CD90,CD105 and Prolyl-4-hydroxylase; in contrast,they did not express CD14,CD34,CD68,or alkaline phosphatase. Interestingly,in five out of nine MDS patients,MSC developed in culture showed cytogenetic abnormalities,usually involving the loss of chromosomal material. All those five cases also showed cytogenetic abnormalities in their hematopoietic cells. Interestingly,in some cases there was a complete lack of overlap between the karyotypes of hematopoietic cells and MSC. To the best of our knowledge,the present study is the first in which a pure population of MSC from MDS patients is analyzed in terms of their whole karyotype and demonstrates that in a significant proportion of patients,MSC are cytogenetically abnormal. Although the reason of this is still unclear,such alterations may have an impact on the physiology of these cells. Further studies are needed to assess the functional integrity of MDS-derived MSC. View Publication

Murine hematopoietic stem and progenitor cells (HSPCs) home to bone marrow in part by rolling on P-selectin and E-selectin expressed on endothelial cells. Human adult CD34(+) cells,which are enriched in HSPCs,roll on endothelial selectins in bone marrow vessels of nonobese diabetic/severe combined immune deficiency (NOD/SCID) mice. Many human umbilical cord blood (CB) CD34(+) cells do not roll in these vessels,in part because of an uncharacterized defect in binding to P-selectin. Selectin ligands must be alpha1-3 fucosylated to form glycan determinants such as sialyl Lewis x (sLe(x)). We found that inadequate alpha1-3 fucosylation of CB CD34(+) cells,particularly CD34(+)CD38(-/low) cells that are highly enriched in HSPCs,caused them to bind poorly to E-selectin as well as to P-selectin. Treatment of CB CD34(+) cells with guanosine diphosphate (GDP) fucose and exogenous alpha1-3 fucosyltransferase VI increased cell-surface sLe(x) determinants,augmented binding to fluid-phase P- and E-selectin,and improved cell rolling on P- and E-selectin under flow. Similar treatment of CB mononuclear cells enhanced engraftment of human hematopoietic cells in bone marrows of irradiated NOD/SCID mice. These observations suggest that alpha1-3 fucosylation of CB cells might be a simple and effective method to improve hematopoietic cell homing to and engraftment in bone marrows of patients receiving CB transplants. View Publication

Human umbilical cord blood (UCB) contains high numbers of endothelial progenitors cells (EPCs) characterized by coexpression of CD34 and CD133 markers. Prior studies have shown that CD34+/CD133+ EPCs from the cord or peripheral blood (PB) can give rise to endothelial cells and induce angiogenesis in ischemic tissues. In the present study,it is shown that freshly isolated human cord blood CD34+ cells injected into ischemic adductor muscles gave rise to endothelial and,unexpectedly,to skeletal muscle cells in mice. In fact,the treated limbs exhibited enhanced arteriole length density and regenerating muscle fiber density. Under similar experimental conditions,CD34- cells did not enhance the formation of new arterioles and regenerating muscle fibers. In nonischemic limbs CD34+ cells increased arteriole length density but did not promote formation of new muscle fibers. Endothelial and myogenic differentiation ability was maintained in CD34+ cells after ex vivo expansion. Myogenic conversion of human cord blood CD34+ cells was also observed in vitro by coculture onto mouse myoblasts. These results show that human cord blood CD34+ cells differentiate into endothelial and skeletal muscle cells,thus providing an indication of human EPCs plasticity. The full text of this article is available online at http://www.circresaha.org. View Publication

Hematopoiesis depends on the association of hematopoietic stem cells with stromal cells that constitute the hematopoietic microenvironment. The in vitro development of the endothelial cell from umbilical cord blood (UCB) is not well established and has met very limited success. In this study,UCB CD34(+) cells were cultured for 5 weeks in a stroma-free liquid culture system using thrombopoietin,flt3 ligand,and granulocyte-colony stimulating factor. By week 4-5,we found that firmly adherent fibroblast-like cells were established. These cells showed characteristics of endothelial cells expressing von Willebrand factor,human vascular cell adhesion molecule-1,human intracellular adhesion molecule-1,human CD31,E-selectin,and human macrophage. Furthermore,when comparing an ex vivo system without an established endothelial monolayer to an ex vivo system with an established endothelial monolayer,better expansion of total nucleated cells,CD34(+) cells,and colony-forming units (CFUs)-granulocyte-macrophage and CFUs-granulocyte-erythroid-megakaryocyte-macrophage were found during culture. This phenomenon was in part due to the fact that a significant reduction of apoptotic fractions was found in the CD34(+) cells,which were cultured on the adherent monolayer for up to 5 weeks. To gather quantitative data on the number of endothelial cells derived from a given number of CD34 cells,we performed limiting dilution assay by using Poisson distribution: the number of tested cells (linear scale) producing a 37% negative culture (logarithmic scale) is the number of cells containing one endothelial cell. By this method,one endothelial cell may be found from 314 CD34(+) cells after 5 weeks of culture. These results suggest that the UCB CD34(+) cell fraction contains endothelial cell precursors,establishing the hematopoietic microenvironment and providing the beneficial effects through downregulating apoptosis on UCB expansion protocols. These observations may provide insight for future cellular therapy or graft engineering. View Publication

Umbilical cord blood (UCB) preparation needs to be optimized in order to develop more simplified procedures for volume reduction,as well as to reduce the amount of contaminating cells within the final stem cell transplant. We evaluated a novel filter device (StemQuick((TM))E) and compared it with our routine buffy coat (BC) preparation procedure for the enrichment of hematopoietic progenitor cells (HPCs). Two groups of single or pooled UCB units were filtered (each n = 6),or equally divided in two halves and processed by filtration and BC preparation in parallel (n = 10). The engraftment capacity of UCB samples processed by whole blood (WB) preparation was compared with paired samples processed by filtration in the nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse animal model. Filtration of UCB units in the two groups with a mean volume of 87.8 and 120.7 ml,respectively,and nucleated cell (NC) content of 9.7 and 23.8 x 10(8) resulted in a sufficient mean cell recovery for mononucleated cells ([MNCs] 74.2%-77.5%),CD34(+) cells (76.3%-79.0%),and colony-forming cells (64.1%-86.3%). Moreover,we detected a relevant depletion of the transplants for RBCs (89.2%-90.0%) and platelets ([PLTs] 77.5%-86.1%). In contrast,the mean depletion rate using BC processing proved to be significantly different for PLTs (10%,p = 0.03) and RBCs (39.6%,p textless 0.01). The NC composition showed a highly significant increase in MNCs and a decrease in granulocytes after filtration (p textless 0.01),compared with a less significant MNC increase in the BC group (p textless 0.05). For mice transplanted with WB-derived progenitors,we observed a mean of 15.3% +/- 15.5% of human CD45(+) cells within the BM compared with 19.9% +/- 16.8% for mice transplanted with filter samples (p = 0.03). The mean percentage of human CD34(+) cells was 4.2% +/- 3.1% for WB samples and 4.5% +/- 3.2% for filter samples (p = 0.68). As the data of NOD/SCID mice transplantation demonstrated a significant engraftment capacity of HPCs processed by filtration,no negative effect on the engraftment potential of filtered UCB cells versus non-volume-reduced cells from WB transplants was found. The StemQuick((TM))E filter devices proved to be a useful tool for Good Manufacturing Practices conform enrichment of HPCs and MNCs out of UCB. Filtration enables a quick and standardized preparation of a volume-reduced UCB transplant,including a partial depletion of granulocytes,RBCs,and PLTs without the need for centrifugation. Therefore,it seems very probable that filter-processed UCB transplants will also result in sufficient hematopoietic reconstitution in humans. View Publication

Cord blood (CB) cells are a useful source of hematopoietic cells for transplantation. The hematopoietic activities of CB cells are different from those of bone marrow and peripheral blood (PB) cells. Platelet recovery is significantly slower after transplantation with CB cells than with cells from other sources. However,the cellular mechanisms underlying these differences have not been elucidated. We compared the surface marker expression profiles of PB and CB hematopoietic cells. We focused on two surface markers of hematopoietic cell immaturity,i.e.,CD34 and AC133. In addition to differences in surface marker expression,the PB and CB cells showed nonidentical differentiation pathways from AC133(+)CD34(+) (immature) hematopoietic cells to terminally differentiated cells. The majority of the AC133(+)CD34(+) PB cells initially lost AC133 expression and eventually became AC133(-)CD34(-) cells. In contrast,the AC133(+)CD34(+) CB cells did not go through the intermediate AC133(-)CD34(+) stage and lost both markers simultaneously. Meanwhile,the vast majority of megakaryocyte progenitors were of the AC133(-)CD34(+) phenotype. We conclude that the delayed recovery of platelets after CB transplantation is due to both subpopulation distribution and the process of differentiation from AC133(+)CD34(+) cells. View Publication

Ectopic retroviral expression of homeobox B4 (HOXB4) causes an accelerated and enhanced regeneration of murine hematopoietic stem cells (HSCs) and is not known to compromise any program of lineage differentiation. However,HOXB4 expression levels for expansion of human stem cells have still to be established. To test the proposed hypothesis that HOXB4 could become a prime tool for in vivo expansion of genetically modified human HSCs,we retrovirally overexpressed HOXB4 in purified cord blood (CB) CD34+ cells together with green fluorescent protein (GFP) as a reporter protein,and evaluated the impact of ectopic HOXB4 expression on proliferation and differentiation in vitro and in vivo. When injected separately into nonobese diabetic-severe combined immunodeficient (NOD/SCID) mice or in competition with control vector-transduced cells,HOXB4-overexpressing cord blood CD34+ cells had a selective growth advantage in vivo,which resulted in a marked enhancement of the primitive CD34+ subpopulation (P =.01). However,high HOXB4 expression substantially impaired the myeloerythroid differentiation program,and this was reflected in a severe reduction of erythroid and myeloid progenitors in vitro (P textless.03) and in vivo (P =.01). Furthermore,HOXB4 overexpression also significantly reduced B-cell output (P textless.01). These results show for the first time unwanted side effects of ectopic HOXB4 expression and therefore underscore the need to carefully determine the therapeutic window of HOXB4 expression levels before initializing clinical trials. View Publication

BACKGROUND: Ex vivo expansion of cord blood (CB) hematopoietic stem and progenitor cells increases cell dose and may reduce the severity and duration of neutropenia and thrombocytopenia after transplantation. This study's purpose was to establish a clinically applicable culture system by investigating the use of cytokines,serum-free media,and autologous plasma for the expansion of CB cells and the engraftment of expanded product in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. STUDY DESIGN AND METHODS: Enriched CB CD34+ cells were cultured in four media (Iscove's modified Dulbecco's medium with FCS,Gibco; X-Vivo-10,BioWhittaker; QBSF-60,Quality Biological; and StemSpan SFEM,Stem Cell Technologies) with four cytokine combinations (thrombopoietin [TPO],SCF,Flt-3 ligand [FL] with and without G-CSF,and/or IL-6). The effect of autologous CB plasma was also investigated. The read-out measures were evaluated on Days 8 and 12. After expansion at the optimized condition,cultured cells were transplanted into sublethally irradiated NOD/SCID mice. The engraftment of human CD45+ cells and subsets in the bone marrow,spleen,and peripheral blood was determined. RESULTS: QBSF-60 or StemSpan SFEM supported high yields of early progenitors (CD34+ cells,textlessor= 64.8-fold; CD34+CD38- cells,330-fold; CFU-granulocyte erythroid macrophage megakaryocyte [GEMM],248-fold) and CFUs of the myeloid (CFU-GM,407-fold) and erythroid (BFU/CFU-E,144-fold) lineages. The expansion of the megakaryocytic lineage was consistently higher in X-Vivo-10 (CFU-megakaryocyte,684-fold). Autologous plasma promoted colony formation but reduced CD34+ cells and CFU-GEMM. The addition of G-CSF or IL-6 improved cell yields; G-CSF was more effective for committed progenitors. Expansion products from cultures in QBSF-60 with the cytokines engrafted and differentiated into the myeloid and lymphoid lineages in NOD/SCID mice. CONCLUSION: The data supported the strategy of expansion. The optimized condition may be applicable to clinical expansion for the abrogation or reduction of posttransplant cytopenia. View Publication