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PubMed2001

Use of pathology-specific peripheral blood CD34 thresholds to predict leukapheresis CD34 content with optimal accuracy: a bicentric analysis of 299 leukaphereses.

CD34+ cell counts in peripheral blood (PB) and corresponding numbers of CD34+ cells and colony-forming units-granulocyte/macrophage (CFU-GM) in 299 leukapheresis products of 209 patients undergoing PB progenitor cell (PBPC) mobilization for autologous transplantation in two different centers were analyzed and compared according to diagnosis: non-Hodgkin lymphoma (NHL, 94 leukaphereses), multiple myeloma (MM, 75), Hodgkin's disease (HD, 37), solid tumors (35), and chronic myeloid leukemia (CML, 32). Without separating disease entities, correlations between PB CD34+ cell counts and leukapheresis content of CD34+ cells (r>0.83, P<0.01) and CFU-GM (r>0.81, P<0.01) were excellent. In both centers, a PB CD34 threshold ensuring a leukapheresis yield > 10(6) CD34/kg was determined. This threshold was higher in center 1 than in center 2, and its predictive accuracy (91.4%, i.e., prediction correct 91.4% of the time) was significantly lower than in center 2 (98.4%, P=0.02). When data were analyzed by pathology, PB CD34+ cell counts and leukapheresis content of CD34+ cells and CFU-GM remained well correlated, and in both centers PB CD34 thresholds predictive of a yield > 10(6) CD34/kg per leukapheresis could be determined for each pathology. For most patients, pathology-specific PB CD34 thresholds could be obtained directly from the equation of the PB CD34/leukapheresis CD34 correlation curve; they varied depending on both pathology and center (range: 7-20 x 10(6) CD34/l). Pathology-specific thresholds predicted a leukapheresis yield > or = 10(6) CD34/kg accurately 100% of the time for MM patients in center 2 and HD and solid tumor patients of both centers, resulting in overall rates of accurate prediction of sufficient graft CD34 content of 96.6% in center 1 and 98.9% in center 2.

Adolescent↗
PubMed1997

Cytokine mediated expansion of human umbilical cord blood CD34+ cells: comparison of the use of partially purified and pure CD34+ target cells.

To determine the optimal cell population for cytokine mediated expansion, we compared the use of Magnetic Cell Sorting (MACS) system enriched CD34+ human umbilical cord blood (HUCB) cells with that of MACS enriched, flow purified CD34+ HUCB cells. Both MACS enriched CD34+ cells and MACS enriched, flow purified CD34+ cells (mean starting purity of CD34+ SC 51.27 +/- 7.6% and 96.36 +/- 1.34% respectively n = 6) were incubated for seven days with Interleukin-1 (IL-1) + IL-3 + Stem Cell Factor (SCF) and showed a fold increase in the number of nucleated cells (10.02 +/- 2.6 and 18.23 +/- 4.73 respectively) and a reduction in the percentage of CD34+ cells (5.55 +/- 1.23% and 12.21 +/- 3.29% respectively). An increase in the absolute numbers of CD34+ cells (4.8 x 10(4) +/- 2.3 x 10(4)) was observed with MACS enriched CD34+ cells as compared to no change (1.3 x 10(5) +/- 8.8 x 10(4) with MACS enriched, flow purified CD34+ cells. An increase in IL-3 + GM-CSF + SCF responsive colony forming unit (CFU) (1.7 x 10(4) +/- 9.4 x 10(3) and 1.6 x 10(5) +/- 7.7 x 10(4) respectively) was also observed as compared with input values (1.5 x 10(4) +/- 1 x 10(4) and 2.3 x 10(4) +/- 8.9 x 10(3) respectively). We conclude that MACS enriched, flow sorted CD34+ HUCB cells have greater cytokine mediated expansion potential as measured by progenitor expansion, than MACS enriched CD34+ HUCB cells.

Antigens, CD34↗
PubMed1999

Increased DNA single-strand break joining activity in UV-irradiated CD34+ versus CD34- bone marrow cells.

The kinetics of UV-irradiation-induced (254 nm) DNA single-strand breaks (SSBs) were studied in single human hematopoietic cells using alkaline comet assay. Three cell populations were investigated: (i) Bone marrow mononuclear cells (BMMNCs) isolated by density gradient centrifugation, (ii) CD34- cells, and (iii) CD34+ cells. The two latter populations were purified from BMMNCs by negative and positive selection, respectively, using anti-CD34 immunobeads. SSBs were induced faster by 10 and 50 J/m2 than by 2 J/m2 and those caused by 2 J/m2 were joined faster that those caused by 10 or 50 J/m2. During the first 1.5 h after irradiation with a dose of 10 J/m2, CD34+ cells joined SSBs faster than did BMMNCs. The superior joining capacity of CD34+ cells was further substantiated with a higher UV dose. The comet lengths, indicating the extent of DNA repair, among 8/8 study subjects were shorter in CD34+ than in CD34- cells when assessed 24 h after a dose of 50 J/m2. Overall, the comet lengths at 24 h after irradiation were: CD34+ cells; 39+/-12 *m, and CD34- cells; 65+/-18 *m (8 subjects, 50 cells measured from each donor, mean+/-S.D.; p=0.0087, Mann-Whitney U-test). These results strongly suggest that nucleotide excision repair, the major mechanism responsible for the repair of UV-irradiation-induced DNA lesions in mammalian cells, is increased in CD34+ cells compared with CD34- cells and with BMMNCs. These results may have implications in stem cell purging, clinical chemotherapy and carcinogenesis.

Adolescent↗
PubMed2002

GATA transcription in a small rhodamine 123(low)CD34(+) subpopulation of a peripheral blood-derived CD34(-)CD105(+) mesenchymal cell line.

OBJECTIVE: Based on previous animal experiments that suggest the plasticity of peripheral blood-derived, CD34(-) stem cell lines, the aim of this study was to isolate CD34(-) stem cell lines from human peripheral blood cells and obtain evidence of their multipotency and plasticity. MATERIALS AND METHODS: Adherent growing cells were isolated from peripheral blood mononuclear cells from a healthy volunteer donor and different cell clones were established after SV40 large-T-antigen-mediated immortalization. The immunophenotype of the cell lines was investigated by flow cytometry. One particular cell clone, V54/2, was stained with rhodamine 123, and the Rh123(low) and Rh123(high) subpopulations were sorted for a reverse transcriptase polymerase chain reaction gene expression survey and distinct differences in morphology and biologic behavior. RESULTS: The peripheral blood-derived and fibroblast-like cell line V54/2 expressed high levels of CD10 and CD105 and showed only a very low level expression of CD34 (<1.0%) and CD117 (c-kit). Among the entire CD34(-)CD105(+) cell population that transcribed factors such as Myb, Tie-1, and VEGF, there was a small Rh123(low)CD34(+) subpopulation that transcribed significant levels of several members of the GATA family of transcription factors. The morphology of the Rh123(low)CD34(+) (also expressing the P-glycoprotein) was different compared to the Rh123(high)CD34(-) population. Mesenchymal differentiation into glial fibrillary acidic protein (GFAP)(+) glial cells could be shown from the entire CD34(-)CD105(+) cell population. CONCLUSIONS: The findings provide evidence that it is possible to isolate CD34(-)CD105(+) mesenchymal stem cell lines from human peripheral blood cells that contain a small subpopulation of CD34(+) and GATA-transcribing cells. Those cells are potential hematopoietic progenitors and can be recruited from the CD34(-) stem cell pool. The plasticity of stem cells seems to require essential molecular tools, such as a panel of transcription factors, to respond to the environmental demand within a biologic system.

Adult↗
PubMed1999

Transplantation of transduced nonhuman primate CD34+ cells using a gibbon ape leukemia virus vector: restricted expression of the gibbon ape leukemia virus receptor to a subset of CD34+ cells.

The transduction efficiencies of immunoselected rhesus macaque (Macaca mulatta) CD34+ cells and colony-forming progenitor cells based on polymerase chain reaction (PCR) analysis were comparable for an amphotropic Moloney murine leukemia virus (MLV) retroviral vector and a retroviral vector derived from the gibbon ape leukemia virus (GaLV) packaging cell line, PG13. On performing autologous transplantation studies using immunoselected CD34+ cells transduced with the GaLV envelope (env) retroviral vector, less than 1% of peripheral blood (PB) contained provirus. This was true whether bone marrow (BM) or cytokine-mobilized PB immunoselected CD34+ cells were reinfused. This level of marking was evident in two animals whose platelet counts never fell below 50,000/microliter and whose leukocyte counts had recovered by days 8 and 10 after having received 1.7 x 10(7) or greater of cytokine-mobilized CD34+ PB cells/kg. Reverse transcriptase(RT)-PCR analysis of CD34+ subsets for both the GaLV and amphotropic receptor were performed. The expression of the GaLV receptor was determined to be restricted to CD34+ Thy-1+ cells, and both CD34+ CD38+ and CD34+ CD38dim cells, while the amphotropic receptor was present on all CD34+ cell subsets examined. Our findings suggest that, in rhesus macaques, PG13-derived retroviral vectors may only be able to transduce a subset of CD34+ cells as only CD34+ Thy-1+ cells express the GaLV receptor.

ADP-ribosyl Cyclase↗
PubMed2001

Analysis of CD34+ cell subsets in stem cell harvests can more reliably predict rapidity and durability of engraftment than total CD34+ cell dose, but steady state levels do not correlate with bone marrow reserve.

In peripheral blood stem cell transplantation (PBSCT), the number of CD34+ cells transplanted has been shown to correlate well with both rapidity and durability of engraftment. However, it is clear that engraftment does not necessarily correlate with total CD34+ cell numbers in some patients. Consequently, there is increasing interest in evaluating the role of CD34+ subsets in haemopoietic recovery as a more accurate marker of harvest quality. We analysed the numbers of CD34+ cell subsets, namely Thy-1+, L-Selectin+ and CD38-, and correlated this with engraftment in 86 patients undergoing PBSCT. Adequate engraftment was defined as being a platelet count greater than 50 x 10(9)/l and a neutrophil count greater than 1.0 x 10(9)/l. CD34+L-Selectin+ provided the best prediction of engraftment rapidity, although the improvement over total CD34+ cell dose was minor. Only the dose of CD34+Thy-1+ cells transplanted correlated with durable engraftment. The probability of adequate 3-month engraftment increased with the dose of CD34+ cells transplanted, but 10% of patients receiving > 5 x 10(6)/kg still showed poor engraftment at 3 months. However, all patients receiving > 2.5 x 10(5)/kg CD34+Thy-1+ showed adequate engraftment at this time point. We also demonstrated that CD34+Thy-1+ progenitors were restricted to the bone marrow under normal conditions and, during stem cell mobilization, their kinetics generally paralleled total CD34+ numbers.

ADP-ribosyl Cyclase↗
PubMed1997

The chemokine SDF-1 is a chemoattractant for human CD34+ hematopoietic progenitor cells and provides a new mechanism to explain the mobilization of CD34+ progenitors to peripheral blood.

Hematopoietic progenitor cells migrate in vitro and in vivo towards a gradient of the chemotactic factor stromal cell-derived factor-1 (SDF-1) produced by stromal cells. This is the first chemoattractant reported for human CD34+ progenitor cells. Concentrations of SDF-1 that elicit chemotaxis also induce a transient elevation of cytoplasmic calcium in CD34+ cells. SDF-1-induced chemotaxis is inhibited by pertussis toxin, suggesting that its signaling in CD34+ cells is mediated by seven transmembrane receptors coupled to Gi proteins. CD34+ cells migrating to SDF-1 include cells with a more primitive (CD34+/CD38- or CD34+/DR-) phenotype as well as CD34+ cells phenotypically committed to the erythroid, lymphoid and myeloid lineages, including functional BFU-E, CFU-GM, and CFU-MIX progenitors. Chemotaxis of CD34+ cells in response to SDF-1 is increased by IL-3 in vitro and is lower in CD34+ progenitors from peripheral blood than in CD34+ progenitors from bone marrow, suggesting that an altered response to SDF-1 may be associated with CD34 progenitor mobilization.

ADP-ribosyl Cyclase↗
PubMed1994

Transplantation of enriched CD34-positive autologous marrow into breast cancer patients following high-dose chemotherapy: influence of CD34-positive peripheral-blood progenitors and growth factors on engraftment.

PURPOSE: To evaluate the capacity of enriched CD34-positive (CD34+) progenitor cells to reconstitute hematopoiesis in poor-prognosis breast cancer patients following administration of a high-dose alkylating agent chemotherapy regimen. PATIENTS AND METHODS: Forty-four breast cancer patients received high-dose chemotherapy followed by autologous bone marrow support (ABMS) with CD34+ hematopoietic progenitor cells in five sequentially treated cohorts. Following infusion of CD34+ marrow, cohort no. 1 received no growth factor, cohort no. 2 received granulocyte colony-stimulating factor (G-CSF), and cohort no. 3 received granulocyte-macrophage colony-stimulating factor (GM-CSF). Cohort no. 4 received the CD34+ fractions of both marrow and peripheral-blood progenitor cells (PBPCs) plus G-CSF. Cohort no. 5 received only the CD34+ PBPCs plus G-CSF. Immunohistochemical staining for breast cancer was performed on all hematopoietic cell products before and after the positive selection procedure, to assess quantitatively the level of tumor-cell contamination. RESULTS: Cohorts no. 1, 2, 3, 4, and 5 achieved a granulocyte count > or = 500 x 10(9)/L in a median of 23, 10, 16, 11, and 11 days, with a platelet count greater than 20,000 x 10(9)/L documented in a median of 22, 23, 32, 12, and 10 days, respectively. The time to granulocyte reconstitution was significantly shorter for patients who received CD34+ PBPCs alone (cohort no. 5), or in combination with CD34+ marrow (cohort no. 4), when compared with those who received only the CD34+ marrow fraction (P < .01). From 1 to greater than 4 logs of breast cancer cell depletion were documented after CD34-selection, for patients in whom tumor was initially detected. CONCLUSION: CD34+ marrow and/or PBPCs provide reliable and timely hematopoietic reconstitution in breast cancer patients receiving high-dose chemotherapy. Contamination of both marrow and PBPCs with breast cancer cells was reduced using this positive selection technique.

Adult↗
PubMed1996

When to harvest peripheral-blood stem cells after mobilization therapy: prediction of CD34-positive cell yield by preceding day CD34-positive concentration in peripheral blood.

PURPOSE: To evaluate whether the CD34+ yield from a single peripheral-blood stem-cell (PBSC) harvest could be predicted by measurement of the patient's circulating WBC and CD34+ cell concentrations on the day before harvest. PATIENTS AND METHODS: Thirty-nine patients with hematologic or nonhematologic malignancy underwent 41 stem-cell mobilization episodes with cytotoxic chemotherapy and/or granulocyte colony-stimulating factor (G-CSF), and a total of 63 leukapheresis procedures were performed. Peripheral-blood samples were analyzed for WBC and CD34+ cell concentration both on the day before and the day of leukapheresis. RESULTS: The median WBC and CD34+ concentrations on the day preceding leukapheresis were 10.0 x 10(9)/L (range, 0.4 to 44.4) and 24.9 x 10(6)/L (range, 0.1 to 349.4), respectively. On the day of harvest, the corresponding figures were 15.1 x 10(9)/L (range, 1.5 to 52.6) and 29.3 x 10(6)/L (range, 0.1 to 543.1), respectively. The median CD34+ cell number collected in a single leukapheresis was 2.6 x 10(6)/kg body weight (range, 0.1 to 26.1). Both the preceding day (r = .84, P < .001) and harvest day (r = .95, P < .001) CD34+ circulating concentrations correlated significantly with the number of CD34+ cells per kilogram collected at leukapheresis. The correlation between CD34+ cells per kilogram collected and harvest day WBC count was also significant (r = .43, P <.001), but with the preceding day WBC count was nonsignificant. CONCLUSION: The number of CD34+ cells harvested in a single leukapheresis can be predicted by measurement of the preceding day peripheral-blood circulating CD34+ concentration, and on the basis of these data a table of probable CD34+ cell yield has been constructed. This correlation may facilitate the efficient organization of leukapheresis procedures.

Antigens, CD34↗
PubMed2000

Relationships between total CD34+ cells reinfused, CD34+ subsets and engraftment kinetics in breast cancer patients.

BACKGROUND AND OBJECTIVE: The aim of the present study was to evaluate the correlation between the number of CD34+ cells transfused and the duration of hypoplasia, and the relationship between various CD34+ subsets (CD34+/33-; CD34+/38-; CD34+/ HLA-DR-; CD34+/Thy-1+) and engraftment kinetics in a series of patients with breast cancer treated with high doses of thiotepa and melphalan. DESIGN AND METHODS: We treated 42 consecutive patients: 19 in an adjuvant context (>= 4 positive axillary nodes) and 23 for metastatic disease. A combination of thiotepa 600 mg/m(2) and melphalan 140-160 mg/m(2) was administered as the conditioning regimen. All patients received peripheral blood progenitor cells (PBPC) and growth factors for hematopoietic rescue. RESULTS: In univariate analysis, we found a significant relationship between the number of CD34+ cells reinfused and the time to hematologic recovery and the duration of hospital stay. We observed an inverse correlation between the number of CD34+ cells reinfused and the units of platelets transfused. Cox multivariate analysis confirmed that the number of CD34+ cells reinfused is the most effective predictor of time to hematologic recovery. CFU-GM resulted to be a better predictor of the duration of hospitalization. INTERPRETATION AND CONCLUSIONS: We found a significant relationship between the number of PBPC reinfused and the time to hematologic recovery after high doses of thiotepa and melphalan. In our experience, the numbers of subsets of CD34+ cells infused did not give compared additional information to that provided by the total number of CD34+ cells infused.

Adult↗
PubMed1992

Up-regulation of surface CD34 is associated with protein kinase C-mediated hyperphosphorylation of CD34.

CD34 is a transmembrane sialoglycoprotein expressed by early hematopoietic progenitor cells as well as endothelial cells. Previously we found that CD34 is rapidly and stoichiometrically phosphorylated by activated protein kinase C (PKC) (Fackler, M.J., Civin, C.I., Sutherland, D.R., Baker, M.A., and May, W.S. (1990) J. Biol. Chem. 265, 11056-11061). In the present study, we find dose-dependent up-regulation of CD34 surface expression following treatment of normal human CD34+ bone marrow progenitor cells, cord blood-derived KMT-2, or KG1 a myeloid leukemia cells with the PKC activator 12-O-tetradecanoylphorbol-13-acetate. Up-regulation begins within 1 min of treatment, is maximal by 30 min, is maintained for at least 3 h, and is associated with CD34 hyperphosphorylation. A specific inhibitor of PKC, 2,6-diamino-N-(1[1-(1-oxotridecyl)-2-piperadinyl]methyl)h exan-amide (NPC 15437), blocks both up-regulation and hyperphosphorylation of CD34. CD34 up-regulation is independent of transcription and/or translation and results from the recruitment of preformed intracellular CD34. The endocytosis rate of surface CD34 is unaltered by 12-O-tetradecanoylphorbol-13-acetate. Thus, activation of PKC mediates increased surface expression of the CD34 molecule possibly as a result of phosphorylation of CD34.

Antigens, CD↗
PubMed2004

Detecting human CD34+ and CD34- hematopoietic stem and progenitor cells using a Sysmex automated hematology analyzer.

In clinical medicine, particularly in the newly developing stem cell therapies required to support the practice of regenerative medicine, the measurement of both CD34+ and CD34- hematopoietic stem cells (HSC)/hematopoietic progenitor cells (HPC) is important in obtaining more accurate information about the total HSC/HPC content in various stem/progenitor cell sources. We report the results of an investigation into methods of detecting CD34+ and CD34- HSC/HPC using the immature information (IMI) channel incorporated into the Sysmex XE-2100 and SE-9000 automated hematology analyzers. In this study, CD34+ and CD34- HSC/HPC were separated by immunologic methods and quantified by flow cytometry (FACScan) and IMI channel analysis. In addition, CD34-/CD133+ HSC were prepared by a sequential antibody-based positive selection strategy. These cells appeared in the same area as CD34+ cells in the IMI channel of the automated hematology analyzer. These findings confirmed that an automated hematology analyzer can be used to measure both CD34+ and CD34- HSC. These results may explain the difference in HSC/HPC counts sometimes observed between the automated hematology analyzer and flow cytometric methods for CD34+ measurement. The results of this study demonstrated the potential of automated cell counting methods for measuring HSC content in cellular products for both research and clinical applications.

AC133 Antigen↗
PubMed2006

The biological characteristics of CD34+ CD2+ adult acute promyelocytic leukemia and the CD34 CD2 hypergranular (M3) and microgranular (M3v) phenotypes.

BACKGROUND AND OBJECTIVES: Acute promyelocytic leukemia (APL) is characterized by leukemic cells blocked at the promyelocytic stage of granulocytic differentiation. To date, it is still not clear whether CD34 expression identifies a subset of APL patients with peculiar characteristics. We, therefore, conducted a detailed analysis of CD34 expression at diagnosis in 136 adults with de novo APL. DESIGN AND METHODS: We investigated 136 newly diagnosed APL patients from four Italian Institutions. All 136 cases were tested for CD34 and CD2 expression: 124 (91%) cases were classified as hypergranular (M3) and 12 (9%) as the hyporgranular M3 variant (M3v). The parameters considered were white blood cell (WBC) and platelet counts, hemoglobin levels, percentage of peripheral blood leukemic promyelocytes (PBLP), CD15, CD56 and HLA-DR expression, and the PML/RARalpha isoform, to assess their relationship with CD34 and CD2 expression. RESULTS: CD34 expression was associated with the M3v subtype and higher proportion of HLA-DR+ and CD2+ cases. Moreover, compared with CD34- APL patients, CD34+ APL patients had a significantly higher percentage of PBLP at presentation, were more frequently female and had a higher proportion of bcr3 expression. Among the 136 APL cases, 24 (17.6%) and 80 (58.8%) were identified as CD34+CD2+ and CD34-CD2-, respectively. The two groups showed statistically significant differences in terms of M3vfrequency, WBC and platelet counts, percentage of PBLP, and bcr3 expression. Moreover, the CD34+CD2+ group showed a higher proportion of CD34+ and bcr3 isoforms compared to the M3v cases. There were no differences between the two groups in terms of complete remission, overall survival and disease-free survival. INTERPRETATION AND CONCLUSIONS: Our findings suggest that immunophenotypic analysis can distinguish a subset of APL patients with different biological characteristics.

Adolescent↗
PubMed1995

Proliferation and differentiation of myelodysplastic CD34+ cells: phenotypic subpopulations of marrow CD34+ cells.

In a search for a mechanism to explain the impaired growth of progenitor cells in patients with myelodysplastic syndromes (MDS), marrow CD34+ cells were purified up to 94.9% +/- 4.2% for normal individuals and 88.1% +/- 17.6% for MDS patients, using monoclonal antibodies and immunomagnetic microspheres (MDS CD34+ cells). Phenotypic subpopulations of these CD34+ cells were analyzed for CD38, HLA-DR, CD33, CD13, CD14, CD41 and CD3 plus CD19, in association with proliferative and differentiative capacities. The 15 studies performed included 12 MDS patients. Coexpression rate of CD13 significantly increased in the MDS CD34+ cell population with a value of 91.4% +/- 11.6% and ranging from 60.3% to 100%, and exceeded 99% in four studies, whereas that of normal CD34+ cells was 49.9% +/- 15.8%, ranging from 28.2% to 70.1% (P < .001). Coexpression rate of CD38, HLA-DR, CD33, CD14, and CD3 plus CD19 in MDS CD34+ cells did not significantly differ from that of normal CD34+ cells. The total number of colonies and clusters grown from 100 normal marrow CD34+ cells was 40.4 +/- 8.6, the range being from 27.2 to 50.3; this varied in MDS marrow CD34+ cells with a value of 34.0 +/- 28.7, the range being 0 to 95.9. The lineage of colonies and clusters promoted by MDS marrow CD34+ cells was predominantly committed to nonerythroid with impaired differentiation in 13 of 15 studies (87%). CD13 is first expressed during hematopoiesis by colony-forming unit granulocyte-macrophage and is absent in erythroid progenitors. Therefore, this study provides direct evidence for the lineage commitment of MDS CD34+ cells to nonerythroid with impaired differentiation and explains the mechanism of nil or low colony expression of MDS progenitor cells to erythroid lineage.

Aged↗
PubMed1999

Maintenance of CD34 expression during proliferation of CD34+ cord blood cells on glycosaminoglycan surfaces.

Recent studies have indicated that glycosaminoglycan (GAG) interactions with hematopoietic progenitors play a significant role in the regulation of hematopoiesis. However, the details of these interactions are not clear. In this study, we examined the role of soluble and immobilized GAGs in the proliferation of CD34+ cells. Chitosan, a cationic polysaccharide, was used to immobilize GAGs in ionic complex membranes. The GAGs studied were heparin, hyaluronate, and chondroitin sulfates A, B, and C. CD34-enriched umbilical cord blood cells were seeded onto tissue culture plates coated with the GAG-chitosan complex membranes. Cultures were maintained in medium supplemented with stem cell factor and interleukin 3 for up to six weeks, during which total and CD34+ cell numbers were determined by flow cytometry. Total cell number expansion ranged from 25-fold to 40-fold after six weeks. However, only heparin and chondroitin sulfate B (CSB) surfaces retained a significant CD34+ fraction. All other surfaces exhibited declines in CD34 expression, with negligible CD34+ percentages remaining after four weeks. In contrast, heparin and CSB surfaces exhibited CD34+ fractions as high as 90% after four weeks. GAG desorption studies indicated that the observed effects were partly mediated by desorbed GAGs in a concentration dependent manner. Subsequent studies showed that sustained high (160 microg/ml) heparin levels had toxic effects, while the same concentration of CSB exhibited more rapid early proliferation of CD34+ cells. In conclusion, this culture system has demonstrated the ability to produce simultaneous proliferation and CD34+ cell enrichment of a partially purified cord blood population by controlling the nature and levels of GAG moieties to which the cells are exposed. The results indicate that specific GAGs can significantly influence the growth and differentiation characteristics of cultured CD34+ cells.

Animals↗
PubMed2000

Ex vivo expansion of CD34+/CD41+ late progenitors from enriched peripheral blood CD34+ cells.

In our experience, patients with neuroblastoma who undergo transplantation with CD34+ cells following high-dose chemotherapy have prolonged delays in platelet recovery. In vitro expansion of megakaryocyte (MK) cells may provide a complementary transplant product able to enhance platelet production in the recipient. We investigated the ability of a combination of various hematopoietic growth factors to generate ex vivo MK progenitors. Immunoselected CD34+ cells from peripheral blood stems cells (PBSCs) were cultured in media with or without serum, supplemented by IL-3, IL-6, IL-11, SCF, TPO, Flt-3 ligand, and MIP-1alpha. In terms of MK phenotypes, we observed a maximal expansion of CD61+, CD41+, and CD42a of 69-, 60-, and 69-fold, respectively, i.e., 8-10 times greater than the expansion of total cell numbers. Whereas the absolute increment of CD34+ cells was slightly elevated (fourfold) we showed increases of 163-, 212-, and 128-fold for CD34+/CD61+, CD34+/CD41+, and CD34+/CD42a+ cells, respectively. We obtained only a modest expansion of CFU-MKs after only 4 days of culture (fourfold) and similar levels of CFU-MKs were observed after 7 days (fivefold). Morphology and immunohistochemistry CD41+ analyses confirmed expansion of a majority of CD41+ immature cells on days 4 and 7, while on day 10 mature cells began to appear. These results show that primarily MK progenitors are expanded after 4 days of culture, whereas MK precursor expansion occurs after 7 days. When we compared the two culture media (with and without serum) we observed that increases of all specific phenotypes of the MK lineage were more elevated in serum-free culture than in medium with serum. This difference was especially marked for CD34+/CD61+ and CD34+/CD41+ (163 vs 42 and 212 vs 36, respectively). We contaminated CD34+ cells with a neuroblastoma cell line and we observed no expansion of malignant cells in our culture conditions (RT-PCR for tyrosine hydroxylase positive at day 4 and negative at day 7). With our combination of hematopoietic growth factors we are able to sufficiently expand ex vivo MK late progenitor cells to be used as complementary transplant products in neuroblastoma patients who undergo transplantation with CD34+ cells. It is possible that these committed MK late progenitors could accelerate short-term platelet recovery in the recipient until more primitive progenitor cells have had time to engraft.

Antigens, CD34↗
PubMed1997

Interaction of vesicular stomatitis virus-G pseudotyped retrovirus with CD34+ and CD34+ CD38- hematopoietic progenitor cells.

Retroviral vectors have had limited success in mediating gene transfer to hematopoietic stem cells, particularly in primates, due in part to low or absent expression of the amphotropic receptor (RAM-1). We have been interested in determining whether retrovirus pseudotyped with vesicular stomatitis virus G protein (VSV-G) would allow more efficient gene delivery to hematopoietic stem cells as the VSV-G receptors appear to be ubiquitously present phospholipids. However, we previously found that completion of retroviral vector reverse transcription does not occur in CD34+ CD38- hematopoietic stem cells that were exposed to VSV-G pseudotyped retrovirus. To determine at which stage the block to infection of CD34+ CD38- cells occurs, we confirmed by FACS analysis that VSV-G pseudotyped viral particles could bind to CD34+ CD38- cells. Virus binding to CD34+ cells was saturable at 4 degrees C but nonsaturable at 37 degrees C, up to a multiplicity of infection of 1080. This suggests that surface levels of phospholipid receptors available for viral binding are limiting on CD34+ cells. Cytokine stimulation increased virus binding to CD34+ cells. However, no increase in the level of surface phosphatidylserine (PS), a strong candidate for the VSV-G receptor, was seen as detected by the PS-specific reagent, annexin V. This suggests that another molecule is serving as the VSV-G receptor on CD34+ cells. Here, we show that once virus binding to cytokine-stimulated CD34+ CD38- cells has occurred, virus fusion proceeds efficiently as determined by octadecyl rhodamine (R18) fusion assays. Taken together with our previous observation that reverse transcription does not occur in CD34+ CD38- cells, we suggest that there are intracellular mechanisms leading to blockage of complete reverse transcription of the retrovirus in CD34+ CD38- cells. This has important implications for retrovirus-mediated gene transfer to quiescent stem cells.

ADP-ribosyl Cyclase↗
PubMed1998

Chronic myelogenous leukaemia CD34+ cells exit G0/G1 phases of cell cycle more rapidly than normal marrow CD34+ cells.

To investigate the mechanisms behind the leukaemic expansion of chronic myelogenous leukaemia (CML), we examined the cell cycle status and activation kinetics of purified subpopulations of CD34+ cells from normal and CML bone marrow (BM). Propidium iodide staining was used to assess cell cycle status of fresh cells or those stimulated with cytokines. Although the cell cycle status of fresh low-density cells from CML and normal BM was similar, a larger percentage of CML CD34+ cells were cycling than those from normal BM. The HLA-DR compartment of CML CD34+ cells, a fraction enriched for normal, non-leukaemic progenitors, contained a higher percentage of quiescent cells than the CD34+ HLA-DR+ fraction. When the activation of CD34+ cells was examined in response to SCF or IL-3 alone, or SCF+IL-3+IL-6, CML CD34+ cells exited GO/G1 more rapidly than normal CD34+ cells. Interestingly, although normal BM CD34+ cells failed to cycle in response to IL-6 alone, or in the absence of exogenous cytokines, 30% of CML cells cycled under these conditions. No differences in the degree of apoptosis were documented among CML and normal CD34+ cells in these cultures. These data suggest that enhanced cell cycle activation of CML CD34+ cells, by either autocrine stimuli or via enhanced sensitivity to exogenous stimuli, may be partially responsible for the pronounced cellular expansion characteristic of CML.

Adult↗