Immature granulocyte fraction in the peripheral blood is a practical indicator for mobilization of CD34(+) cells

We propose a simple parameter that improves prediction of the number of CD34(+) cells in blood cells collected by apheresis for autologous peripheral blood stem cell (PBSC) transplantation following administration of granulocyte colony-stimulating factor. The percentage of immature granulocytes including myeloblasts, promyelocytes, myelocytes, and metamyelocytes (LSI for left-shift index) immediately prior to the start of each apheresis correlated with the number of CD34(+) cells in PBSC collections (r = 0.79, P < 0.0001, Y = 0.227X - 0.99, R(2) = 0.623) much better than did the white blood cell count (r = 0.07), currently the most commonly used predictor in deciding the initiation of apheresis. We then used receiver operating characteristic (ROC) curves to determine a cutoff point for LSI to prevent unnecessary apheresis. At LSI > 7.5, sensitivity and specificity of cutoff points in the probability of obtaining >1.0 x 10(6) CD34(+) cells/kg BW were 93.3% and 94.3% (95% CI, 91.4-100.0%), respectively. When LSI reaches 15.25, nearly 100% of apheresis will attain the target CD34(+) cell dose. These findings indicate that LSI is a useful and simple method for predicting the yield of CD34(+) cells before the start of PBSC collection and avoiding unnecessary apheresis.     

High-dose cyclophosphamide,etoposide and BCNU (CVB) with autologous stem cell rescue in malignant lymphomas

Abstract: Eighteen patients with malignant lymphoma, 10 non-Hodgkin's and 8 Hodgkin's, were treated with high-dose CVB (cyclophosphamide 4 × 1.5 g/m², etoposide 4 × 250–400 mg/m², carmustine 4 × 150–200 mg/m²), followed by autologous peripheral blood stem cells (PBSC, 13 patients) or bone marrow (BM, 5 patients) transplantation. At the time of autograft 6 patients were in complete remission (CR), 3 in partial remission (PR) and 5 in relapse (4 sensitive, 1 resistant), whereas 4 had progressive disease. All CR patients had poor prognostic features at presentation. PBSC were collected at the time of rapid hematologic recovery after intense chemotherapy by means of a cell separator. All patients engrafted. Median time to achieve ≥0.5 × 10⁹/1 polymorphonuclear cells (PMN) and ≥50 × 10⁹/1 platelets was 13 days for both cell types in PBSC autografted patients, versus 20 and 28 days respectively in BM autografted patients. A significant advantage of PBSC over BM was found in terms of time needed to recover either PMN ≥0.5 and PMN≥1 × 10⁹/1 (p = 0.01). Autograft-related toxicity consisted mainly of moderate severity interstitial pneumopathy (3 patients), and veno-occlusive disease (1 patient) that resolved completely. Of the 12 patients autografted with detectable disease, 6 (50%) obtained a CR. Seven out of 18 autografted patients (39%) had disease progression within 1 to 5 months of autograft. The projected progression-free survival is over 50% at 4 years and it was significantly longer in patients with sensitive disease than in those with resistant disease (p = 0.01). The efficacy and the low toxicity of CVB suggest that autograft with PBSC may be proposed for the primary treatment of poor prognosis malignant lymphomas.     

CD34~+ CD38~-细胞对异基因造血干细胞移植的影响研究

目的观察CD34+CD38-细胞对异基因造血干细胞移植术后造血重建和移植物抗宿主病(GVHD)的影响。方法分析2004年1月至2009年12月河南省人民医院血液科全相合异基因外周血干细胞造血干细胞移植78例,CD34+、CD34+CD38-细胞输入量与血缘全相合异基因外周血造血干细胞移植术后造血重建及GVHD发生率间的相关性。结果粒细胞、血小板恢复时间与CD34+CD38-细胞输入量呈负相关(r分别为-0.521、-0.448,P<0.01),与CD34+细胞输入量也呈负相关(r分别为-0.405、-0.371,P<0.05)。急性GVHD、慢性GVHD的发生与CD34+、CD34+CD38-、CD3+、CD4+、CD8+细胞输入量无相关性。结论输入高数量的CD34+CD38-细胞有利于移植术后的粒细胞、血小板快速恢复;对于预测术后造血恢复,CD34+CD38-细胞亚群输入量可能优于CD34+细胞总数。     

Autografting with CD34+ peripheral blood stem cells: retained engraftment capability and reduced tumour cell content

The efficacy of an immunomagnetic purging method and the Isolex 300 devices were assessed for selecting CD34+ cells from leukapheresis products of 29 patients with non-Hodgkin's lymphoma (NHL), 39 with multiple myeloma and 34 with breast cancer. The mean purity of the CD34+ cell population was 93.6% and the mean recovery was 67.7%. Following enzymatic cleavage by chymopapain the expression of Thy-1 and Leu-8 was significantly reduced without affecting haematological recovery. The population of selected CD34+ cells of 4/8 patients with follicular lymphoma became PCR-negative. A 2.5 log reduction of tumour cells could be achieved in four patients with multiple myeloma as shown by a quantitative PCR assay. There were no tumour cells detectable in any of the 19 CD34+ cell preparations of patients with breast cancer. In 64 patients who received 94 cycles of high-dose therapy, a mean number of 4.7x 10(6) CD34+ cells/kg were autografted. The time needed for platelet reconstitution was different when a comparison was made with 156 patients, who had received unmanipulated leukapheresis products (10 v 12 d, P = 0.006). No significant differences with regard to neutrophil recovery were noted. Five patients had a graft failure. Two of them died (on day 78 and 88 following PBSCT), and three patients were rescued with unmanipulated back-up transplants. In conclusion, the immunomagnetic selection of CD34+ cells provides autografts with reduced tumour cell content and an engraftment ability similar to that of unmanipulated autografts.     

Counting of leukocytes in samples from G-CSF mobilized donors, leukapheresis products, and cord blood: the performances of an analyzer with dedicated profiles

Introduction: Accurate white blood cell counting (WBC) and differential count by blood analyzers could allow a more informative characterization of granulocyte colony‐stimulating factor (G‐CSF) mobilized blood (MB), leukapheresis products (LP), and cord blood (CB). However, reliable counting by a blood cell analyzer in this setting is a major challenge owing to quali‐quantitative abnormalities of blood cells. Methods: We evaluated the performances of the analyzer Pentra DX 120 by Horiba ABX working with dedicated cell‐gating profiles, which generate three‐part differential counts in samples obtained from donors’ MB, LP, and CB. The results of the analyzer were compared to counts obtained by flow cytometry and manual counts, the latter performed for reference validation and in the case of discrepant results between study and reference counts. Results: Pentra DX 120 generated highly correlated counts (R > 0.91 in all cases) to those obtained by flow cytometry in all samples (MB, LP, and CB) with high degree of count accuracy in most cases and referred to WBC absolute count and differential count including lymphocytes (LYM) %, monocytes (MON) %, and polymorphonuclear leukocytes (PMN) %. Accuracy, judged by the difference between study and reference counts and expressed as percentage of reference count, ranged from 0.8% to 8.6%, and sporadic loss of accuracy occurred for MON % only in no more than 10% of CB samples. Conclusion: The ABX Pentra DX 120 provided accurate WBC count and differential count during MB, LP, and CB analyses and allowed a better characterization of donors’ hematologic status and graft composition.     

Factors which affect the CFU-GM content of the peripheral blood haemopoietic progenitor cell harvests in patients with acute myeloid leukaemia

Autologous peripheral blood haemopoietic stem cells (PBSC) were harvested from 30 patients with de novo acute leukaemia, 29 of whom had entered remission following standard chemotherapy. Correlation of CD34⁺ cells/kg to CFU-GM/kg in the harvests was good (correlation coefficient=0.72, P<0.001). We demonstrated significant associations between the CFU-GM content of the harvest and the following: time to platelets >50×10⁹/l post final induction course (P<0.0001), days to harvest from day 1 of intensification/mobilization (correlation coefficient=?0.73, P<0.001), platelets >20×10⁹/l at time of harvest (P=0.02), time to WBC >1.0×10⁹/l post intensification/mobilization (correlation coefficient=?0.70, P<0.001), and WBC on day of harvest (correlation coefficient=0.60, P<0.001). In contrast, we found no relationship between the CFU-GM content of the harvest and patient age up to 65 years, presence of absence of coexistent features of trilineage myelodysplasia at diagnosis, number of induction courses to remission or total number of courses of chemotherapy prior to intensification/mobilization. Haemopoietic recovery after reinfusion of PBSC was highly correlated to the number of CFU-GM infused (neutrophils >0.5×10⁹/l r_s=?0.72, P=0.001; platelets >20×10⁹/l unsupported r_s=?0.71, P=0.001). Our results show that the number of induction courses received, and thus exposure to cytotoxic agents received, made no significant difference to subsequent CFU-GM harvest content. We collected superior harvests from those patients with faster platelet recovery following mobilization therapy. We also found that faster platelet recovery following the final induction therapy was a better predictor of the CFU-GM harvest following mobilization than was the neutrophil recovery following final induction.     

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.     

Treatment of chronic myeloid leukaemia in first chronic phase with idarubicin and cytarabine: mobilization of Philadelphia-negative peripheral blood stem cells

Peripheral blood stem cell (PBSC) mobilization using idarubicin and cytarabine was investigated in 40 patients with chronic myeloid leukaemia in first chronic phase (CML CP1). Disease contamination was evaluated in harvests from 41/44 (93%) mobilization episodes. Using cytogenetics, 22/37 (59%) showed a complete or major response; Southern blot analysis demonstrated a complete or major response in 9/17 (53%). No harvests were RT-PCR negative. In the 41 evaluable episodes, more complete or major responses were seen when PBSC mobilization occurred within 24 months [17/23 (74%) versus 6/18 (33%); P  =0.02] and within 12 months of diagnosis [10/11 (91%) versus 13/30 (43%); P  = 0.018]. 20 patients underwent PBSC transplantation and 18/20 successfully engrafted. Post-transplant cytogenetic analysis was available on 15 cases, of whom five achieved a major cytogenetic response at 1–3 months, with five partial cytogenetic remissions. Two of 40 patients died during mobilization therapy (5%) and three of 20 after the transplant (15%). Overall mortality was high at five of 40 patients, and the procedural mortality was 20%. This study demonstrates that Ph-negative PBSCs can be mobilized in a significant proportion of patients with CML CP1, with the best results observed within a year of diagnosis. These cells can subsequently be used for autologous transplantation, however, the impact on long-term survival requires longer follow-up, and potential benefits may be compromised by the high mortality.     

Sustained proliferation, multi-lineage differentiation and maintenance of primitive human haemopoietic cells in NOD/SCID mice transplanted with human cord blood

Time course studies of sublethally irradiated non-obese mice with severe combined immunodeficiency (NOD/SCID mice) transplanted intravenously with 10⁷ human cord blood cells showed a rapid and parallel regeneration of human erythroid, granulopoietic, megakaryopoietic and B-lymphoid progenitors, as well as more primitive subpopulations of CD34⁺ cells (defined by their multi-lineage in vitro colony-forming ability, coexpression of Thy-1, or functional activity in long-term culture-initiating cell [LTC-IC] assays), in the marrow, spleen and blood. Maximum numbers of human cells were reached within 6 weeks and were then sustained for another 18–20 weeks. ³H-thymidine suicide studies showed all types of in vitro clonogenic human progenitors tested and the human LTC-IC to be proliferating in vitro throughout this period. A 2-week course of injections of human Steel factor, interleukin-3, granulocyte-macrophage colony-stimulating factor and erythropoietin given just prior to assessment of the mice had no effect on any of these human engraftment parameters. 4–6 weeks post-transplant, the marrow of primary NOD/SCID recipients contained human cells that were able to regenerate lymphopoiesis and/or myelopoiesis in secondary irradiated NOD/SCID mice. These findings establish a baseline for the kinetics of engraftment, multi-lineage differentiation and self-renewal of human cord blood stem cells in this xenogeneic transplant model and thus set the stage for future studies of their regulation in vivo .     

CD34+/CD90+ cells infused best predict late haematopoietic reconstitution following autologous peripheral blood stem cell transplantation

This study aimed to identify which graft product subset of cells might be the most predictive of late haematopoietic recovery (three to 12 months) following autologous peripheral blood stem cell transplantation (PBSCT). The relationships between the numbers of reinfused CD34+ cells and their immature subsets such as CD34+/CD90+, CD34+/AC133+, CD34+/CD38- and CD34+/HLA-DR- cells, and haemoglobin, white blood cell (WBC) and platelet counts at 3, 6, 9 and 12 months after PBSCT, were studied in 25 patients with haematological and solid malignancies. The total CD34+ cell number, as well as CD34+/CD90+ and CD34+/AC133+ cell numbers, correlated with platelet counts at 3, 6, 9 and 12 months after PBSCT, but the CD34+/CD90+ cells infused best predicted platelet recovery during the first 12 months after PBSCT (P < 0.0238 at any time-point). The CD34+/AC133+ cell dose also correlated with WBC counts at 3 months post PBSCT. In addition, all patients receiving more than 80 x 10(4) CD34+/CD90+ cells/kg showed platelet counts greater than 100 x 10(9)/l at all points after PBSCT, suggesting that this value of the CD34+/CD90+ cells infused was a threshold dose for durable haematopoietic engraftment after PBSCT.     

Growth factor receptor profile of CD34 cells in normal bone marrow, cord blood and mobilized peripheral blood

Growth factors regulate the proliferation and differentiation of hemopoietic cells. Their effect on hemopoietic precursors differs according to the ontogenic source of the cells. Cord blood and mobilized blood CD34(+) cells have a higher sensitivity for growth factors than bone marrow CD34(+) cells. This could be due to a higher expression of growth factor receptors. Therefore, we examined the expression of receptors for stem cell factor (SCF), interleukin-6 (IL-6), IL-3, granulocyte colony-stimulating factor (G-CSF) and IL-7 on the CD34(+) cells of cord blood, mobilized peripheral blood and bone marrow. The receptors were detected with monoclonal antibodies and flow cytometry. The majority of the CD34(+) cells in bone marrow clearly expressed SCFR; they showed a moderate positivity for IL-3Ralpha and a weak staining for G-CSFR and IL-6 Ralpha. Less than 10% of the cells were IL-7R positive. Cord blood CD34(+) cells showed a higher expression of SCFR and a lower positivity for G-CSFR and IL-6Ralpha. Mobilized blood CD34(+) cells showed a lower expression of SCFR and G-CSFR, and a higher positivity for IL-3Ralpha. This was not solely due to the presence of more myeloid precursors in mobilized blood, as the growth factor receptor profile did not correspond to that of early or late myeloid CD34(+) precursors in normal bone marrow. Changes induced by the mobilization procedure occurred as well. In conclusion, the higher sensitivity for growth factors of hemopoietic precursors in cord blood and mobilized blood cannot be explained by a general increase of the growth factor receptor expression on the CD34(+) cells.     

Primordial role of CD34+38− cells in early and late trilineage haemopoietic engraftment after autologous blood cell transplantation

In order to better define which cell subset contained in graft products might be the most predictive of haemopoietic recovery following autologous blood cell transplantation (ABCT), the relationships between the amounts of reinfused mononuclear cells (MNC), CFU-GM, total CD34⁺ cells and their CD33 and CD38 subsets, and the successive stages of trilineage engraftment kinetics, were studied in 45 cancer patients, using the Spearman correlation test, a linear regression model and a log-inverse model. No relationship was found between the infused numbers of MNC, CD33⁺ and CD33^? subsets observed and the numbers of days to reach predetermined absolute neutrophil (ANC), platelet and reticulocyte counts. The infused numbers of CFU-GM, CD34⁺ and CD34⁺38⁺ cells correlated inconstantly with haemopoietic recovery parameters. The strongest and the most constant correlations were significantly observed between the infused numbers of CD34⁺38^? cells and each trilineage engraftment parameter. The log-inverse model determined a threshold dose of 0.05 × 10⁶ (= 5 × 10⁴) CD34⁺38^? cells/kg, below which the trilineage engraftment kinetics were significantly slower and unpredictable. Post-transplant TBI-conditioning regimens increased the low cell dose-related delay of engraftment kinetics whereas post-transplant administration of haemopoietic growth factors (HGF) seemed to abrogate this delay. This would justify clinical use of HGF only in patients transplanted with CD34⁺38^? cell amounts lower than the proposed threshold value. This study suggests that the CD34⁺38^? subpopulation, although essentially participating in late complete haemopoietic recovery, is also composed of committed progenitor cells involved in early trilineage engraftment.     

Preclinical ex vivo expansion of peripheral blood CD34+ selected cells from cancer patients mobilized with combination chemotherapy and granulocyte colony-stimulating factor

Background and Objectives  Ex vivo peripheral blood progenitor cell (PBPC) expansion has been proposed as a strategy to increase the number of haematopoietic progenitors available for cell transplantation. We have expanded CD34+ cells from PBPCs obtained from four patients with haematological malignancies and one patient with an Ewing's sarcoma.
Materials and Methods  Cells were expanded in the Dideco 'Pluricell system'. After 12 days in culture, we evaluated cell phenotype, total nucleated cells, CD34+ fold increase, cell apoptosis and colony assay of expanded cells. Cell engraftment has been evaluated by transplanting two groups of irradiated non-obese diabetic/severe combined immunodeficient (NOD-SCID) mice with expanded and non-expanded cell populations.
Results  Total nucleated cells and CD34+ cells increased 59·5 and 4·0 times, respectively. The expanded cells were mainly constituted of myeloid and megakaryocytic cells. A significant increase in the number of colony-forming unit–granulocyte macrophage (CFU-GM) was observed in the CFU assay. Ten mice transplanted with expanded cells showed a best overall survival (80%) compared to 10 mice transplanted with non-expanded cells (20%). Human CD45+ cells were detected by flow cytometry and polymerase chain reaction in bone marrow and spleen of transplanted animals. The relative low engraftment level obtained with the expanded cells suggests a loss of SCID repopulating cells maybe due to cell differentiation during expansion.
Conclusions  We have demonstrated the feasibility of the ex vivo expansion of mobilized PBPCs from cancer patients, evidencing a clonal expansion of CFUs and the ability of the expanded cells to engraft the bone marrow and spleen of immunosuppressed mice. The differentiation of the CD34+ stem cell compartment could be further minimized by ameliorating the expansion conditions.     

Early apoptosis in CD34+ cells as a potential heterogeneity in quality of cryopreserved umbilical cord blood

The increased use of umbilical cord blood (UCB) raises issues regarding the quality of cryopreserved UCB. This study investigated whether early apoptosis of CD34+ cells is part of the functional heterogeneity of cryopreserved UCB. Annexin V binding of CD34+ PI(-) cells showed wide variations in both fresh and cryopreserved UCBs, with greater variation among units frozen for > 5 years. Xenotransplantation of sorted cells into non-obese diabetic severe combined immunodeficient mice demonstrated that the Annexin V assay identified most repopulating activities in UCB units. Thus, early apoptosis of CD34+ cells could influence the outcome of transplantation using cryopreserved UCB.     

Generation and functional characterization of human dendritic cells derived from CD34+ cells mobilized into peripheral blood: comparison with bone marrow CD34+ cells

Dendritic cells (DCs) are the most powerful professional antigen-presenting cells (APC), specializing in capturing antigens and stimulating T-cell-dependent immunity. In this study we report the generation and characterization of functional DCs derived from both steady-state bone marrow (BM) and circulating haemopoietic CD34⁺ cells from 14 individuals undergoing granulocyte colony-stimulating factor (G-CSF) treatment for peripheral blood stem cells (PBSC) mobilization and transplantation. Clonogenic assays in methylcellulose showed an increased frequency and proliferation of colony-forming unit-dendritic cells (CFU-DC) in circulating CD34⁺ cells, compared to that of BM CD34⁺ precursors in response to GM-CSF and TNF-α with or without SCF and FLT-3L. Moreover, peripheral blood (PB) CD34⁺ cells generated a significantly higher number of fully functional DCs, as determined by conventional mixed lymphocyte reactions (MLR), than their BM counterparts upon different culture conditions. DCs derived from mobilized stem cells were also capable of processing and presenting soluble antigens to autologous T cells for both primary and secondary immune response. Replacement of the early-acting growth factors SCF and FLT-3L with IL-4 at day 7 of culture of PB CD34⁺ cells enhanced both the percentage of total CD1a⁺ cells and CD1a⁺CD14^? cells and the yield of DCs after 14 d of incubation. In addition, the alloreactivity of IL-4-stimulated DCs was significantly higher than those generated in the absence of IL-4. Furthermore, autologous serum collected during G-CSF treatment was more efficient than fetal calf serum (FCS) or two different serum-free media for large-scale production of DCs. Thus, our comparative studies indicate that G-CSF mobilizes CD34⁺ DC precursors into PB and circulating CD34⁺ cells represent the optimal source for the massive generation of DCs. The sequential use of early-acting and intermediate-late-acting colony-stimulating factors (CSFs) as well as the use of autologous serum greatly enhanced the growth of DCs. These data may provide new insights for manipulating immunocompetent cells for cancer therapy.     

Immunomagnetic selection of CD34+peripheral blood stem cells for autografting in patients with breast cancer

Contamination of transplants with tumour cells may contribute to relapse after peripheral blood stem cell transplantation (PBSCT). We studied the feasibility of CD34⁺ cell selection from blood-derived autografts obtained following G-CSF-supported cytotoxic chemotherapy in a group of 25 patients with breast cancer (10 with high-risk stage II/III and 15 with stage IV without bone or bone marrow involvement).
Using immunomagnetic beads (Isolex 300 SA, Baxter) CD34⁺ cells were enriched and released by chymopapain resulting in a median purity of 95% (range 82–99%) and a median recovery of 80% (range 27–132%). The enrichment procedure did not change the proportion of CD34⁺ subsets coexpressing HLA-DR, CD38 and Thy-1, while L-selectin was removed from the cell surface following selection. Using a sensitive immunocytological technique with a cocktail of epithelial-specific antibodies (anti-cytokeratin 8, 18 and 19; HEA125; BM7 and BM8), five leukaphereses products contained epithelial cells, whereas the selected CD34⁺ cell fraction was free of tumour cells. A neutrophil count of 0.5×10⁹/l and a platelet count of 20×10⁹/l was reached after a median time of 14 and 10 d following 40 high-dose chemotherapy (HDC) cycles. Our results indicate that immunomagnetic selection of CD34⁺ cells yields highly purified autografts devoid of tumour cells whereas the engraftment ability of the progenitor and stem cells is fully retained.     

Impact of different dimethyl sulphoxide concentrations on cell recovery,viability and clonogenic potential of cryopreserved peripheral blood hematopoietic stem and progenitor cells

Background and Objectives The procedure of autologous hematopoietic stem/progenitor cell transplantation requires cryopreservation. Addition of DMSO is necessary to secure the viability of such cells, but this solvent is potentially toxic to stem cells’ recipient. 10% DMSO solution is used by the majority of transplant centres. The aim of our study was to test if DMSO concentration might be reduced without negative impact on cell recovery and clonogenicity. Materials and Methods Samples were prospectively collected from 20 patients. Small volumes of leukapheresis products were frozen with different cryoprotective mixtures, containing 10%, 7·5%, 5% and 2·5% DMSO, respectively. The quality of cryoprotective mixtures was evaluated based on recovery, viability and clonogenic potential of hematopoietic stem cells after defreezing. Results Reduction in DMSO concentration to 7·5% or lower was associated with decreased recovery of nucleated cells. In contrast, the number of colonies was highest for 7·5% DMSO with significant differences when compared to 10% DMSO solution. Conclusion Reduction in DMSO concentration from 10% to 7·5% may have favourable impact on hematopoietic recovery after autologous transplantation. The findings require confirmation in a clinical setting.     

Variables affecting the presence of mesenchymal stromal cells in peripheral blood and their relationship with apheresis products

Mesenchymal stromal cells (MSCs) demonstrate the properties of self-renewal, multipotentiality, and immunosuppression, which are responsible for their widespread clinical applications in tissue repair and regeneration. MSCs have been isolated from bone marrow, adipose tissue, and cord blood using culture in specialised media. Their presence in peripheral blood (PB) is debatable. We studied the presence of MSCs at baseline (PB) and following mobilisation with growth factors [PB and apheresis product (AP)] in patients undergoing autologous stem cell transplantation and healthy donors using flow cytometry. We conclude that both mobilised PB and AP are potential sources of MSCs. Given their small numbers in PB/AP, clinical use is feasible following ex-vivo expansion. Variables affecting the presence of MSCs in PB and AP are also discussed.     

Identification of human T-lymphoid progenitor cells in CD34+ CD38low and CD34+ CD38+ subsets of human cord blood and bone marrow cells using NOD-SCID fetal thymus organ cultures

In contrast to myeloid and B-lymphoid differentiation, which take place in the marrow environment, development of T cells requires the presence of thymic stromal cells. We demonstrate in this study that human CD34+, CD34+ CD38+ and CD34+ CD38(low) cells from both cord blood and adult bone marrow reproducibly develop into CD4+ CD8+ T cells when introduced into NOD-SCID embryonic thymuses and further cultured in organotypic cultures. Such human/mouse FTOC fetal thymic organ culture) thus represents a reproducible and sensitive system to assess the T-cell potential of human primitive progenitor cells. The frequency of T-cell progenitors among cord-blood-derived CD34+ cells was estimated to be 1/500. Furthermore, the differentiation steps classically observed in human thymus were reproduced in NOD-SCID FTOC initiated with cord blood and human marrow CD34+ cells: immature human CD41(low) CD8- sCD3- TCR alphabeta- CD5+ CD1a+ T cells were mixed with CD4+ CD8+ cells and more mature CD4+ CD8- TCR alphabeta+ cells. However, in FTOC initiated with bone marrow T progenitors, <10% double-positive cells were observed, whereas this proportion increased to 50% when cord blood CD34+ cells were used, and most CD4+ cells were immature T cells. These differences may be explained by a lower frequency of T-cell progenitors in adult samples, but may also suggest differences in the thymic signals required by bone marrow versus cord blood T progenitors. Finally, since cytokine-stimulated CD34+ CD38(low) cells retained their ability to generate T cells, these FTOC assays will be of value to monitor, when combined with other biological assays, the influence of different expansion protocols on the potential of human stem cells.