Subsets of CD34+ cells and rapid hematopoietic recovery after peripheral-blood stem-cell transplantation

Evaluation of AQUIOS STEM, a novel method for automated CD34+ stem cell enumeration using flow cytometry

OBJECTIVES

Hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for various diseases. The measurement of CD34+ cells is crucial to schedule the peripheral blood stem cell collection and assess the engraftment potential of the apheresis product. The AQUIOS STEM system has been introduced as a novel application on the AQUIOS CL, a fully automated flow cytometer, for the enumeration of CD34+ hematopoietic progenitor cells (HPCs) in accordance with the The International Society for Hematotherapy and Graft Engineering guidelines. This study aimed to assess the potential of the novel AQUIOS STEM system versus currently used systems including the FACSCanto-II and the FACS Lyric flow cytometer in a multicenter study.

METHODS

A total of 91 samples were used for the validation of the AQUOIS STEM system, including an analytical performance evaluation by means of assessing precision, sample stability, intersample carryover, and linearity and a method comparison with the present FACS systems in use to assess analytical and clinical decision agreement.

RESULTS

Results showed excellent precision, with coefficient of variations <15% for dedicated quality control material and patient samples. There was no significant carry over. The fresh apheresis samples were stable when stored overnight at room temperature and at 4°C. Analytical comparison with the current systems demonstrated good correlation in peripheral blood, and minimal, clinically neglectable systematic and proportional bias in fresh apheresis products but a low correlation coefficient in cryopreserved products.

CONCLUSIONS

The STEM system on AQUIOS CL allows automated enumeration of CD34+ stem cells, demonstrating good analytical performance and promising overall outcomes in peripheral blood and fresh apheresis products.

Can GCSF-stimulated donor lymphocyte infusions improve outcomes for relapsed disease following allogeneic hematopoietic cell transplantation? A systematic review and meta-analysis

Donor lymphocyte infusions (DLI) can produce graft-versus tumor effects to treat relapse after allogeneic hematopoietic cell transplantation, however, durable responses remain uncommon. A systematic review and meta-analysis are needed to clarify whether DLI collected after stimulation with granulocyte colony-stimulating factor (GCSF; G-DLI) can improve clinical outcomes. Sixteen studies (4 controlled) involving 585 patients were identified in a systematic search up to 17 September 2020. A meta-analysis demonstrated no significant difference in the risk of all-cause mortality (RR: 0.94, 95% CI 0.52-1.68, p = 0.82; n = 3 studies) or relapse-related mortality (RR: 0.72, 0.44-1.18, p = 0.19; n = 3 studies) between G-DLI and conventional DLI (C-DLI) groups. G-DLI products had similar mean CD3+ cells compared to C-DLI products, but median CD34+ cells/kg were increased. No improvement in disease progression, complete response rates, or risk of developing GVHD was observed with G-DLI, however, greater non-relapse mortality was observed compared to C-DLI. Alternative approaches to enhancing graft-versus-tumor effects are needed.

Short treatment of peripheral blood cells product with Fas ligand using closed automated cell processing system significantly reduces immune cell reactivity of the graft in vitro and in vivo

Mobilized peripheral blood cells (MPBCs) graft and peripheral blood cells apheresis are used for bone marrow transplantation and for treatment of graft versus host disease (GvHD). We demonstrate that a short treatment of MPBCs with Fas ligand (FasL, CD95L) for 2 h using a closed automated cell processing system selectively induces apoptosis of specific donor T cells, B cells and antigen presenting cells, but, critically, not CD34⁺ hematopoietic stem cells and progenitors, all of which may contribute to an increased likelihood of graft survival and functionality and reduced GvHD. Treated cells secreted lower levels of interferon-gamma as compared with control, untreated, cells. Moreover, FasL treatment of immune cells increased signals, which led to their phagocytosis by activated macrophages. FasL treated immune cells also reduced the ability of activated macrophages to secrete pro-inflammatory cytokines. Most importantly, FasL ex vivo treated MPBCs prior to transplantation in NOD-SCID NSG mice prevented GvHD and improved stem cell transplantation in vivo. In conclusion, MPBCs, as well as other blood cell products, treated with FasL by automated manufacturing (AM), may be used as potential treatments for conditions where the immune system is over-responding to both self and non-self-antigens.

Enumeration of viable CD34+ cells in cord blood using a novel stem cell enumeration kit

OBJECTIVE

To assess the detection performance of the hematopoietic stem cell enumeration kit developed by BD Biosciences.

METHODS

Cord blood samples were prepared using a hematopoietic stem cell enumeration kit developed by BD Biosciences and Stem-Kit reagents from Beckman Coulter. CD34+ cells were enumerated using a BD FACSCanto instrument and FACSDiva software.

RESULTS

A total of 519 samples were analyzed in this study. The hematopoietic stem cell enumeration kit developed by BD Biosciences yielded absolute counts of CD34-positive cells that were on average 8.7% lower than Beckman Coulter Stem-Kit reagents (range: -5.7% to-14.7%). The BD Biosciences kit yielded relative counts that were on average 9.9% higher compared with Beckman Coulter Stem-Kit reagents (range: -2.1% to +13.8%). The intraclass correlation coefficients for absolute and relative counts of CD34-positive cells were 0.9967 (95% confidence interval [CI]: 0.9961-0.9972) and 0.9512 (95% CI: 0.9423-0.9587) for the BD Biosciences and Beckman Coulter kits, respectively.

CONCLUSIONS

The hematopoietic stem cell enumeration kit developed by BD Biosciences can be used to enumerate CD34-positive stem cells from cord blood samples.

Hematopoietic stem and progenitor cells use podosomes to transcellularly cross the bone marrow endothelium

Bone marrow endothelium plays an important role in the homing of hematopoietic stem and progenitor cells upon transplantation, but surprisingly little is known on how the bone marrow endothelial cells regulate local permeability and hematopoietic stem and progenitor cells transmigration. We show that temporal loss of vascular endothelial-cadherin function promotes vascular permeability in BM, even upon low-dose irradiation. Loss of vascular endothelial-cadherin function also enhances homing of transplanted hematopoietic stem and progenitor cells to the bone marrow of irradiated mice although engraftment is not increased. Intriguingly, stabilizing junctional vascular endothelial-cadherin in vivo reduced bone marrow permeability, but did not prevent hematopoietic stem and progenitor cells migration into the bone marrow, suggesting that hematopoietic stem and progenitor cells use the transcellular migration route to enter the bone marrow. Indeed, using an in vitro migration assay, we show that human hematopoietic stem and progenitor cells predominantly cross bone marrow endothelium in a transcellular manner in homeostasis by inducing podosome-like structures. Taken together, vascular endothelial-cadherin is crucial for BM vascular homeostasis but dispensable for the homing of hematopoietic stem and progenitor cells. These findings are important in the development of potential therapeutic targets to improve hematopoietic stem and progenitor cell homing strategies.

CD34+ cell dose effects on clinical outcomes after T-cell replete haploidentical allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia using peripheral blood stem cells. A study from the acute leukemia working Party of the European Society for blood and marrow transplantation (EBMT)

Previous observations have reported controversial conclusions regarding cell dose and survival endpoints after allogeneic hematopoietic stem cell transplantation (HSCT). We conducted a retrospective analysis on 414 adult patients (median age 54 years, range, 18-74 years) with acute myeloid leukemia (AML) in first and second complete remission. They received a T-cell replete allogeneic HSCT from haploidentical donors, using peripheral blood stem cells, between 2006-2018. Median number of infused CD34+ was 6.58 × 10⁶ /kg (range, 2.2-31.2 × 10⁶ /kg). Graft-vs-host disease (GVHD) prophylaxis was post-transplant cyclophosphamide in 293 patients and anti-lymphocyte serum in 121 patients. Conditioning was myeloablative in 179 patients and reduced-intensity in 235 patients. After a median follow-up of 23.3 months (range, 12.1-41.8 months), 2-year overall survival (OS) was 64.5% (95% CI 59.3%-69.7%) with leukemia-free survival (LFS) of 57.3% (95% CI 51.8%-62.7%) and non-relapse mortality (NRM) of 23.3% (95% CI 19%-27.7%). Grades III-IV acute GVHD day+100 incidence was 14.6% while extensive chronic GVHD was 14.4% at 2-years. Thirteen (3.2%) patients experienced graft failure. We found the optimal CD34+/kg threshold defining high (n = 334) vs low cell dose (n = 80) at 4.96 × 10⁶ . Recipients of >4.96 × 10⁶ /kg CD34+ cells experienced less NRM (Hazard ratio [HR] 0.48; 95% CI 0.30-0.76) and prolonged LFS (HR 0.63; 95% CI 0.43-0.91) and OS (HR 0.60; 95% CI 0.40-0.88) compared to those in the lower cell dose cohort. Larger cohort studies are needed to confirm these findings.

Allogeneic hematopoietic cell transplantation; the current renaissance

Allogeneic hematopoietic cell transplantation (HCT) provides the best chance for cure for many patients with malignant and nonmalignant hematologic disorders. Recent advances in selecting candidates and determining risk, procedure safety, utilization in older patients, use of alternative donors, and new or novel application of anti-cancer, immunosuppressive and antimicrobial agents have improved outcomes and expanded the role of HCT in hematologic disorders. Relapse remains the predominant cause of failure but enlightened use of new targeted and immunotherapeutic agents in combination with HCT promises to reduce relapse and further improve HCT outcomes.

Peripheral Stem Cell Apheresis is Feasible Post 131Iodine-Metaiodobenzylguanidine-Therapy in High-Risk Neuroblastoma, but Results in Delayed Platelet Reconstitution

PURPOSE

Targeted radiotherapy with ¹³¹iodine-meta-iodobenzylguanidine (¹³¹I-MIBG) is effective for neuroblastoma (NBL), although optimal scheduling during high-risk (HR) treatment is being investigated. We aimed to evaluate the feasibility of stem cell apheresis and study hematologic reconstitution after autologous stem cell transplantation (ASCT) in patients with HR-NBL treated with upfront ¹³¹I-MIBG-therapy.

EXPERIMENTAL DESIGN

In two prospective multicenter cohort studies, newly diagnosed patients with HR-NBL were treated with two courses of ¹³¹I-MIBG-therapy, followed by an HR-induction protocol. Hematopoietic stem and progenitor cell (e.g., CD34⁺ cell) harvest yield, required number of apheresis sessions, and time to neutrophil (>0.5 × 10⁹/L) and platelet (>20 × 10⁹/L) reconstitution after ASCT were analyzed and compared with "chemotherapy-only"-treated patients. Moreover, harvested CD34⁺ cells were functionally (viability and clonogenic capacity) and phenotypically (CD33, CD41, and CD62L) tested before cryopreservation (n = 44) and/or after thawing (n = 19).

RESULTS

Thirty-eight patients (47%) were treated with ¹³¹I-MIBG-therapy, 43 (53%) only with chemotherapy. Median cumulative ¹³¹I-MIBG dose/kg was 0.81 GBq (22.1 mCi). Median CD34⁺ cell harvest yield and apheresis days were comparable in both groups. Post ASCT, neutrophil recovery was similar (11 days vs. 10 days), whereas platelet recovery was delayed in ¹³¹I-MIBG- compared with chemotherapy-only-treated patients (29 days vs. 15 days, P = 0.037). Testing of harvested CD34⁺ cells revealed a reduced post-thaw viability in the ¹³¹I-MIBG-group. Moreover, the viable CD34⁺ population contained fewer cells expressing CD62L (L-selectin), a marker associated with rapid platelet recovery.

CONCLUSIONS

Harvesting of CD34⁺ cells is feasible after ¹³¹I-MIBG. Platelet recovery after ASCT was delayed in ¹³¹I-MIBG-treated patients, possibly due to reinfusion of less viable and CD62L-expressing CD34⁺ cells, but without clinical complications. We provide evidence that peripheral stem cell apheresis is feasible after upfront ¹³¹I-MIBG-therapy in newly diagnosed patients with NBL. However, as the harvest of ¹³¹I-MIBG-treated patients contained lower viable CD34⁺ cell counts after thawing and platelet recovery after reinfusion was delayed, administration of ¹³¹I-MIBG after apheresis is preferred.

Aerobic exercise in humans mobilizes HSCs in an intensity-dependent manner

Hematopoietic stem and progenitor cells are necessary to maintain, repair, and reconstitute the hematopoietic blood cell system. Mobilization of these cells from bone marrow to blood can be greatly increased under certain conditions, one such being exercise. The purpose of this study was to identify the importance of exercise intensity in hematopoietic mobilization, to better understand the mobilization kinetics postexercise, and to determine if exercise is capable of mobilizing several specific populations of hematopoietic cells that have clinical relevance in a transplant setting. Healthy individuals were exercised on a cycle ergometer at 70% of their peak work rate (WRpeak) until volitional fatigue and at 30% of their WRpeak work matched to the 70% WRpeak bout. Blood was collected before, immediately post, and 10, 30, and 60 min postexercise. Total blood cells, hematocrit, and mononuclear cells isolated by density gradient centrifugation were counted. Specific populations of hematopoietic stem cells were analyzed by flow cytometry. Mononuclear cells, CD34+, CD34+/CD38-, CD34+/CD110+, CD3-/CD16+/CD56+, CD11c+/CD123-, and CD11c-/CD123+ cells per millilter of blood increased postexercise. Overall, the 70% WRpeak exercise group showed greater mobilization immediately postexercise, while there was no observable increase in mobilization in the work matched 30% WRpeak exercise group. Mobilization of specific populations of hematopoietic cells mirrored changes in the general mobilization of mononuclear cells, suggesting that exercise serves as a nonspecific mobilization stimulus. Evidently, higher intensity exercise is capable of mobilizing hematopoietic cells to a large extent and immediately postexercise is an ideal time point for their collection.

NEW & NOTEWORTHY

Here we demonstrate for the first time that mobilization of hematopoietic stem cells (HSCs) through exercise is intensity dependent, with the greatest mobilization occurring immediately after high-intensity exercise. As well, we show that exercise is a general stimulus for mobilization: increases in specific HSC populations are reliant on general mononuclear cell mobilization. Finally, we demonstrate no differences in mobilization between groups with different aerobic fitness.

Safety and Efficacy of Megakaryocytes Induced from Hematopoietic Stem Cells in Murine and Nonhuman Primate Models

Because of a lack of platelet supply and a U.S. Food and Drug Administration‐approved platelet growth factor, megakaryocytes have emerged as an effective substitute for alleviating thrombocytopenia. Here, we report the development of an efficient two‐stage culture system that is free of stroma, animal components, and genetic manipulations for the production of functional megakaryocytes from hematopoietic stem cells. Safety and functional studies were performed in murine and nonhuman primate models. One human cryopreserved cord blood CD34⁺ cell could be induced ex vivo to produce up to 1.0 × 10⁴ megakaryocytes that included CD41a⁺ and CD42b⁺ cells at 82.4% ± 6.1% and 73.3% ± 8.5% (mean ± SD), respectively, yielding approximately 650‐fold higher cell numbers than reported previously. Induced human megakaryocytic cells were capable of engrafting and producing functional platelets in the murine xenotransplantation model. In the nonhuman primate model, transplantation of primate megakaryocytic progenitors increased platelet count nadir and enhanced hemostatic function with no adverse effects. In addition, primate platelets were released in vivo as early as 3 hours after transplantation with autologous or allogeneic mature megakaryocytes and lasted for more than 48 hours. These results strongly suggest that large‐scale induction of functional megakaryocytic cells is applicable for treating thrombocytopenic blood diseases in the clinic. Stem Cells Translational Medicine2017;6:897–909

The prognostic impact of peripheral blood progenitor cell dose following high-dose therapy and autologous stem cell transplant for hematologic malignancies

High-dose chemotherapy (HDT) followed by autologous peripheral blood progenitor cell transplant (PBPCT) has become a standard intervention in certain clinical settings of hematologic malignancies, particularly multiple myeloma and relapsed/refractory lymphoma. While the minimal required PBPCs infused, as defined by number of CD34 + cells, has been relatively well delineated for adequate hematopoietic recovery post-HDT, optimal PBPC dose has not been clearly defined. This is particularly relevant in the context of retrospective data suggesting improved survival outcomes with increased PBPC doses. The potential confounding of these data as they relate to disease risk is discussed within this review. Additionally, other retrospective data have suggested that enhanced quantitative lymphocyte subset reconstitution post-HDT-PBPCT may confer progression-free and overall survival advantage. These reported series herein reviewed may inform discussion of future, prospective clinical trials with the intent of defining optimal autologous PBPC dose following HDT, especially as it may relate to metrics beyond hematopoietic recovery.

Characterization of Clonogenic Progenitors in Autologous Peripheral Blood Stem Cell Grafts: Evaluation of a Simple In Vitro Assay Suitable for Routine Clinical Use

Autologous peripheral blood stem cell (PBSC) transplantation has a low treatment-related morbidity and mortality when using appropriate criteria for patient selection and graft quality evaluation. It will be important to use simple and standardised procedures for evaluation of progenitor cell numbers when considering autografting in patients with malignant or non-malignant disorders and increased risk of prolonged posttransplant cytopenia. We determined the number of clonogenic cells in PBSC autografts after 7 days of in vitro culture, and these results were compared with both the total number of colonies and the numbers of colony subsets in conventional 14 days colony assays (colony-forming unit granulocyte-erythrocyte-macrophage-megakaryocyte, CFU-GEMM; CFU-E, CFU-GM; CFU-megakaryocyte). The total colony number after 7 days of culture correlated significantly with (i) the CD34+ cell number; (ii) the total colony number as well as the numbers of erythroid, nonerythroid and mixed colonies in a conventional assay using 14 days of culture; (iii) the number of megakaryocyte colonies. The total colony number after 7 days of in vitro culture is a simple in vitro parameter that seems to reflect the proliferative capacity of various progenitor subsets in PBSC autografts. This simple analysis may be used in combination with other in vitro techniques (e.g. estimation of stem cell viability and CD34+ cell subset analysis) for pretransplant evaluation of autografts. However, the possible clinical use of this parameter has to be examined in prospective clinical studies.

Predictive factors for rapid neutrophil and platelet engraftment after allogenic peripheral blood stem cell transplantation in patients with acute leukemia

The aim of this study was to investigate predictive factors for rapid engraftment after allogeneic peripheral blood stem cell transplantation (alloPBSCT) in patients with acute leukemia. Two hundred sixty-two patients receiving alloPBSCT were analyzed. Subset analyses of donor stem cells were conducted using a flow cytometric method. The correlation between rapid engraftment of neutrophils, platelets, and donor stem cells doses, as well as other recipient and donor clinical factors, was analyzed. In univariate analysis, factors correlated with neutrophil engraftment (≥0.5 × 10(9)/L) by day 12 were achievement of complete remission (CR) after induction chemotherapy (CR1) before hematopoietic cell transplantation (HCT) and high numbers of CD34+ cells, CD3+ T cells, and CD3+/CD4+ T cells. Factors correlated with platelet engraftment (≥20 × 10(9)/L) by day 12 were achievement of CR1 before HCT, donor and recipient sex mismatch, and high numbers of mononuclear cells, CD34+ cells, CD3+ T cells, CD3+/CD4+ T cells, CD3+/CD8+ T cells, and CD56+ NK cells. In multivariate analysis, independent predictive factors for rapid neutrophil and platelet engraftment were CR1 before HCT (p < 0.001 and p = 0.002, respectively), high number of donor CD34+ cells (p = 0.005 and p < 0.001, respectively), and high number of CD3+ T cells (p = 0.005 and p = 0.001, respectively). In conclusion, achieving CR1 before HCT, as well as larger quantities of donor CD34+ and CD3+ T cells, may predict rapid neutrophil and platelet engraftment after PBSCT.

High-dose therapy and autologous peripheral blood stem cell transplantation in patients with multiple myeloma

Since its introduction in 1983, high-dose therapy followed by autologous peripheral blood stem cell transplantation is a pillar of the treatment of patients with multiple myeloma. In the last decades, a multitude of clinical trials helped to improve strategies based on high-dose therapy and autologous stem cell transplantation resulting in a continuously prolongation of overall survival of patients. In this chapter we will review the progress, which has been made in order to enhance the mobilisation of autologous stem cells and increase the effectiveness of this treatment.

Platelet-rich plasma diminishes calvarial bone repair associated with alterations in collagen matrix composition and elevated CD34+ cell prevalence

The interaction between platelets and both type I and III collagens plays an important role in modulating platelet adhesion and aggregation, also contributing to the chemotaxis of CD34+ cells. The interaction with type III collagen can maintain high levels of collagen and alter the biology of bone repair when the PRP is used. The aim of this study was to evaluate the effect of platelet-rich plasma (PRP) and autograft on the presence of type III and type I collagens, the ratio between them, as well as the presence of CD34+ progenitor cells, while comparing these results by means of a histomorphometric analysis of the bone tissue. Four bone defects (8.0mm in diameter and 2.0mm in depth) were produced on the calvarium of 23 rabbits. The surgical defects were treated with either autogenous bone grafts, autogenous bone grafts with PRP and PRP alone. Animals were euthanized at 2, 4 or 6 weeks post-surgery. Histological, histomorphometric and immunohistochemical analyses were performed to assess repair time, as well as the expression of type I and III collagens, and number of progenitor CD34+ cells. Data were analyzed using the ANOVA and Student-Newman-Keuls test (alpha=5%). An enlarged granulation and medullary tissue areas in the PRP groups were observed. The use of PRP in this study hindered bone deposition, also enhanced type III to type I collagen ratio and the chemotaxis of CD34+ progenitor cells, similarly to a thrombogenic effect.

Plerixafor inhibits chemotaxis toward SDF-1 and CXCR4-mediated stroma contact in a dose-dependent manner resulting in increased susceptibility of BCR-ABL+ cell to Imatinib and Nilotinib

Despite Imatinib's remarkable success in chronic myelogenous leukemia treatment, monotherapy frequently causes resistance, underlining the rationale for combination chemotherapy. A potential approach would be interrupting the SDF-1/CXCR4 axis using the selective CXCR4 antagonist Plerixafor (previously AMD3100), as this axis has been reported to provide survival-enhancing effects to myeloid progenitor cells. By efficient CXCR4 blocking in the CXCR4(+)/BCR-ABL(+) cell line BV-173, plerixafor (1-100 muM) significantly inhibits SDF-1alpha-mediated chemotaxis and cell migration toward the murine stroma cell line FBMD-1. Furthermore, plerixafor also significantly (10-100 muM) increased the detachment rate of SDF-1-mediated/VCAM-1-associated cell adherence under shear stress. Using a stroma-dependent coculture assay, plerixafor sensitized BCR-ABL(+) cells toward tyrosine kinase inhibitor therapy. Because the level of cell killing nearly reached that of samples cultured without stroma, a cell-cell interaction disruption seems to improve the efficacy of BCR-ABL-targeting drugs. In addition, we could show that exposure of BCR-ABL(+) cells to Imatinib or Nilotinib induced an increase in surface CXCR4 expression. Our data suggest that for BCR-ABL(+) leukemia, the selective blocking of the SDF-1/CXCR4 axis by plerixafor is a potential mechanism to overcome the protective effect of the bone marrow environment, thereby increasing the therapeutic potency of anti-BCR-ABL drugs and the therapeutic window.

Comparison of unmobilized and mobilized graft characteristics and the implications of cell subsets on autologous and allogeneic transplantation outcomes

Autologous and allogeneic hematopoietic stem cell transplantation (HSCT) are considered the standard of care for many malignancies, including lymphoma, myeloma, and some leukemias. In many cases, mobilized peripheral blood has become the preferred source of hematopoietic stem cells. The efficacy of different mobilization regimens and transplantation outcomes based on cell doses has been well studied; however, the characteristics of the stem cell graft may be of equal importance with respect to patient outcomes following autologous or allogeneic HSCT. This review summarizes available preclinical and clinical data for bone marrow and mobilized peripheral blood HSCT characteristics, defined as the cell types found in the graft as well as their gene expression profiles. It also explores how graft characteristics can affect bone marrow homing, engraftment, immune reconstitution, and other posttransplantation outcomes in both the allogeneic and autologous HSCT settings.

Improved postthaw viability and in vitro functionality of peripheral blood hematopoietic progenitor cells after cryopreservation with a theoretically optimized freezing curve

BACKGROUND

The freezing curve currently used for the cryopreservation of peripheral blood stem cell transplants (PBSCTs) has been determined empirically. Although the use of cryopreserved PBSCTs is successful and usually leads to rapid hematopoietic recovery, the freeze-thawing process is known to induce a significant degree of cell death. Furthermore, the infusion of dimethyl sulfoxide (DMSO), used to protect the cells against damage induced by freezing, can cause morbidity. Therefore, optimizing the current cryopreservation protocol (with 10% DMSO and a slow linear cooling curve) with theoretically optimized freezing curves and a lower DMSO concentration might improve the recovery after transplantation.

STUDY DESIGN AND METHODS

A theoretical model was used to predict optimal freezing curves for 5 and 10 percent DMSO. CD34+-selected and -unselected PBSCs were cryopreserved with the current or the new freezing curves. Postthaw quality was evaluated by cell viability, colony formation, and megakaryocyte outgrowth.

RESULTS

With 10 percent DMSO, the use of the predicted optimal freezing curve resulted in increased postthaw viability of CD34+ cells, colony formation, and megakaryocyte outgrowth. Lowering the DMSO concentration to 5 percent resulted in improved postthaw viability and functionality, which was not further improved by use of the theoretically optimized freezing curve.

CONCLUSIONS

Our results indicate that the current cryopreservation method for PBSCTs can be improved by either lowering the DMSO concentration to 5 percent or by using the theoretically optimized freezing curve. Infusion of less DMSO and more viable cells might improve the outcome of PBSCT.

Histopathology of bone marrow reconstitution after umbilical cord blood transplantation for hematological diseases

To study hematopoietic reconstitution in umbilical cord blood transplantation (CBT), bone marrow (BM) histology was investigated in 35 biopsies after bone marrow transplantation (BMT) and in 40 biopsies after CBT. BM biopsies were obtained at different times after transplantation and were evaluated for cellularity, number of megakaryocytes and CD34-positive cells, and fibrosis. In biopsies up to 29 days after BMT, cellularity was increased and megakaryocytes were observed, but at 29 days after CBT, biopsies showed severe cellular depletion and almost no megakaryocytes. In addition, fewer CD34-positive cells were observed after CBT compared to after BMT. After day 30 after CBT, hematopoietic recovery of the BM was gradually observed and after day 100 after transplantation, no essential differences were observed between BMT and CBT. Hematopoietic recovery of the BM after CBT was delayed compared to that after BMT, but engraftment of donor cells after CBT was also observed in histopathologically. To the best of the authors' knowledge this is the first histopathological description of BM reconstitution after CBT.

Inverse Tendency between Ex Vivo Expansion Potential of Hematopoietic Progenitors and Time to Engraftment after Hematopoietic Stem Cell Transplantation

BACKGROUND

The CD34(+) cell dose and infused number of committed progenitor cells in transplantation are important factors in hematologic engraftment. However, the relationship between expansion potential of progenitor cells and hematologic engraftment remains controversial. We evaluated whether expansion potential of progenitor cells is a predictive factor of post-transplantation hematologic engraftment.

METHODS

Mononuclear cells isolated from mobilized peripheral blood and bone marrow were cultured with cytokine cocktail for 7 days. Progenitor cells and committed progenitors were analyzed using stem cell markers (CD34 and CD133) and lineage specific markers. Hematologic engraftment was defined as neutrophil counts over 500/microL and platelet counts over 20,000/microL without transfusion. Acute and chronic graft-versus-host disease (GVHD) were investigated.

RESULTS

There was inverse tendency between the number and fold expansion of progenitor cells or committed (granulocytic or megakaryocytic) progenitors and time to engraftment. Especially, fold expansion of CD34(+)/CD33(+) cells was significantly correlated with time to neutrophil engraftment in bone marrow transplantation (r=-0.56, P=0.04). The infused number and fold expansion of lymphoid progenitors were not related to the occurrence of acute or chronic GVHD.

CONCLUSIONS

We could not prove that expansion potential of progenitor cells and committed progenitor cells is correlated to hematologic engraftment although there is a correlation between CD34(+)/ CD33(+) cells and time to neutrophil engraftment. But, a further study on the value of expansion potential is required because there is an inverse tendency.

In leukapheresis products from non-Hodgkin's lymphoma patients, the immature hematopoietic progenitors show higher CD90 and CD34 antigenic expression

Damage to the stem cell progenitors caused by the chemotherapy received in patients diagnosed with non-Hodgkin's lymphoma (NHL) may be an important factor limiting progenitor cell mobilization. The aim of the present analysis was to evaluate the effect of the chemotherapy on the different progenitor cell subpopulations obtained in the leukapheresis. For this purpose, a combination of immunophenotype and functional assays has been performed in 26 mobilized peripheral blood (PB) samples from NHL patients and 36 healthy donors. The different progenitor subpopulations analyzed by flow cytometry significantly correlated with the corresponding populations assessed by functional assays in both healthy donors and NHL patients (p<0.05, r>0.5). The number of committed CFU-GM was similar in both groups (p=0.246), but we found significant decrease in the number of BFU-E and more immature progenitors in PB from NHL patients as compared to donors (p<0.05). Moreover, the number of total CFU was significantly lower in NHL patients (p=0.007). Accordingly, CD34+ cells (p=0.018) and CD34+ subpopulations was decreased in NHL patients. Nevertheless, CD90 and CD34 intensity was significantly higher within CD34+ cells from NHL patients as compared to donors. However, although numerically reduced non-committed CD34+ cells are more immature in chemotherapy mobilized NHL patients. In summary, our results show that all NHL hematopoietic progenitors, analyzed by both immunophenotypical and functional approaches, are impaired in leukapheresis products.

A randomized comparison of peripheral blood hematopoietic progenitor cell level of 5/mm3 versus 50/mm3 as a surrogate marker to initiate efficient autologous blood stem cell collection

We previously showed that at least 5/mm(3) hematopoietic progenitor cells (HPCs) could be used as a marker for initiating autologous blood stem cell collection (ABSCC). However, the timing of efficient ABSCC following mobilization is still to be determined. We conducted a prospective, randomized comparison of 5/mm(3) versus 50/mm(3) peripheral blood (PB) HPCs as a surrogate marker to initiate efficient ABSCC. Forty-five consecutive patients, 26 with multiple myeloma (MM) and 19 with non-Hodgkin's lymphoma (NHL), were enrolled between October 2004 and October 2006. Chemotherapy was cyclophosphamide 4 g/m(2) for MM and ESHAP (etoposide, methylprednisolone, high-dose cytarabine, and cisplatin), with or without Rituximab, for NHL. Circulating HPCs were monitored daily with the Sysmex SE9000 automated hematology analyzer, and harvested CD34+ cells were counted by flow cytometry. ABSCC was initiated when HPC levels reached at least 5/mm(3) (HPC5 group) or 50/mm(3) (HPC50 group). The median number of harvested CD34+ cells was 15.0 x 10(6)/kg and 21.0 x 10(6)/kg in the HPC5 and HPC50 groups, respectively (P = 0.23). Optimal collection (>5 x 10(6) CD34+ cells/kg) in a single session (day 1) was attained in 15 HPC5 patients (63%) and in 14 HPC50 patients (67%), and targeted collection of 5 x 10(6) CD34+ cells/kg was achieved in 100 and 95% of HPC5 and HPC50 patients, respectively (P = 0.47), with a median number of 1 apheresis in both groups (P = 0.58). There were no between group differences in optimal collection rate on day 1, median number of aphereses to achieve optimal collection, and overall optimal collection rate. HPC > or = 5/mm(3) and > or =50/mm(3) are both reliable indices for the timing of ABSCC.

Failure to achieve a threshold dose of CD34+CD110+ progenitor cells in the graft predicts delayed platelet engraftment after autologous stem cell transplantation

In this study, we retrospectively analysed the utility of CD110 expression on CD34(+) cells as a predictor of delayed platelet transfusion independence in 39 patients who underwent autologous peripheral blood stem cell transplantation. Absolute CD34(+) cells and CD34(+) subsets expressing CD110 were enumerated using flow cytometry. Of the 39 patients, 7 required 21 days or more to achieve platelet transfusion independence. Six of the seven patients received a dose of CD34(+)CD110(+) cells below 6.0 x 10(4)/kg while 30 of 32 patients who achieved platelet transfusion independence in <21 days received a dose of CD34(+)CD110(+) cells >6.0 x 10(4)/kg (P<0.001). Patients with delayed platelet engraftment received a median dose of 5.2 x 10(4) CD34(+)CD110(+) cells/kg compared with a median dose of 16.4 x 10(4) cells/kg for those engrafting within 21 days (P=0.003). Further analysis showed that >6.0 x 10(4) CD34(+)CD110(+) cells/kg was highly sensitive (93.8%) and highly specific (85.7%) for achieving platelet transfusion independence within 21 days. Delay in platelet transfusion independence translated into an increased requirement for platelet transfusion (median 6 vs 2 transfusions, P<0.0001). The dose of CD34(+)/CD110(+) cells/kg infused at time of transplantation appears to be an important factor identifying patients at risk of delayed platelet engraftment.

Risk assessment in haematopoietic stem cell transplantation: Stem cell source

Bone marrow (BM) has been used for many years as the unique source of progenitor cells for allogeneic transplantation. However, two other sources of progenitor cells, peripheral blood (PB) and umbilical cord (UC), are being increasingly used. The type of graft is one of the most important factors in determining the speed and robustness of the reconstitution after the transplant of monocytes, T lymphocytes, B lymphocytes, NK cells, and dendritic cells. This fact is of especial relevance since the most important reactions after allogeneic transplants - e.g. graft-versus-host disease (GVHD), graft-versus-leukaemia effect (GvL), achievement of full donor chimerism, and fight against infections - are strongly influenced by a rapid and robust reconstitution of these cells. For this reason, the choice of the type of graft for allogeneic transplantation will influence the clinical outcome.

Clinical approaches involving thrombopoietin to shorten the period of thrombocytopenia after high-dose chemotherapy

High-dose chemotherapy followed by a peripheral blood stem cell transplant is successfully used for a wide variety of malignancies. A major drawback, however, is the delay in platelet recovery. Several clinical strategies using thrombopoietin (Tpo) have been developed in an attempt to speed up platelet repopulation. In contrast to its success in immune thrombocytopenia and in low-dose toxic chemotherapeutic regimens, Tpo appears less effective in the case of high-dose chemotherapy and peripheral blood stem cell transplant. To develop a successful therapeutic approach, more knowledge is needed on several aspects of megakaryocyte (progenitor) biology, such as homing to the bone marrow, endomitosis, and platelet formation. Interactions of the megakaryocytes with the marrow vasculature and the microvascular microenvironment are other key factors for optimal thrombocytopoiesis. The present report reviews the background of the inefficiency of Tpo after intensive chemotherapy and describes possible strategies that might lead to successful therapies to treat chemotherapy-induced thrombocytopenia.

Low doses of GM-CSF (molgramostim) and G-CSF (filgrastim) after cyclophosphamide (4 g/m2) enhance the peripheral blood progenitor cell harvest: results of two randomized studies including 120 patients

The use of a combination of G-CSF and GM-CSF versus G-CSF alone, after cyclophosphamide (4 g/m2) was compared in two randomized phase III studies, including 120 patients. In study A, 60 patients received 5 x 2 microg/kg/day of G-CSF and GM-CSF compared to 5 mug/kg/day of G-CSF. In study B, 60 patients received 2.5 x 2 microg/kg/day G-CSF and GM-CSF compared to G-CSF alone (5 microg/kg/day). With the aim to collect at least 5 x 10(6)/kg CD34 cells in a maximum of three large volume leukapherises (LK), 123 LK were performed in study A, showing a significantly higher number of patients reaching 10 x 10(6)/kg CD34 cells (21/29 in G+GM-CSF arm vs 11/27 in G-CSF arm, P=0.00006). In study B, 109 LK were performed, with similar results (10/27 vs 15/26, P=0.003). In both the study, the total harvest of CD34 cells/kg was twofold higher in G-CSF plus GM-CSF group (18.3 x 10(6) in study A and 15.85 x 10(6) in study B) than in G-CSF group (9 x 10(6) in study A and 8.1 x 10(6) in study B), a significant difference only seen in multiple myeloma, with no significant difference in terms of mobilized myeloma cells between G-CSF and GM-CSF groups.

Expression of MAC-1 (CD11b) in acute myeloid leukemia (AML) is associated with an unfavorable prognosis

There is evidence to suggest, that cellular adhesion molecules and receptors could play a role in leukemia, e.g., through altered adhesive qualities of leukemic blasts. We have studied the expression of the beta2-integrin Mac-1 (CD11b) on mononuclear cells in 48 patients with AML at first diagnosis by flow cytometry using a direct fluorescein-conjugated antibody. A case was defined as positive if more than 20% of the cells expressed Mac-1. Within the FAB types, we observed a high expression rate in cases with M5 (100% MAC-1+ cases, 73% MAC-1+ cells), M4 (75% MAC-1+ cases, 48% MAC-1+ cells) and in cases with FAB-M1 with 71% MAC-1+ cases and 29% MAC-1+ cells. Separating our patients' cohort in cytogenetic risk groups, we could detect significant higher proportions of MAC-1+, cases (88% vs. 27%, P = 0.005) and cells (51% vs. 16%, P = 0.015) with poor cytogenetic risk compared to the favorable risk group. For clinical evaluations only patients treated according to the protocols of the German AML Cooperative Group (AML-CG) were included (n = 29, cases with AML-M3 were excluded). More MAC-1+ cases and cells were found in the "non-responders" group (n = 8) compared to the "responders" group (n = 24). We can conclude that AML cases with high MAC-1 expression are characterized by a worse prognosis. Evaluation of MAC-1 expression in AML might therefore contribute clinically important data with respect to develop new therapies that influence the interactions between integrins like MAC-1 on leukemic cells and endothelial or immunoreactive cells.

Implementation of peripheral blood CD34 analyses to initiate leukapheresis: marked reduction in resource utilization

BACKGROUND

Analysis of the peripheral blood (PB) C34 value may determine the optimal time to initiate leukapheresis.

STUDY DESIGN AND METHODS

After selecting a threshold PB CD34 value of five CD34 + cells per microL to initiate leukapheresis procedure, a prospective analysis of 50 consecutive patients was initiated to identify the optimal time to initiate leukapheresis and its impact on costs and resource utilization. Clinical decisions were made to commence or to postpone leukapheresis with this PB CD34 threshold number. Based on PB CD34 values for each patient, the number of leukapheresis procedures, postponed or canceled, the number of CD34+ cells per kg, and the total number of cells collected were identified. Costs of mobilization were obtained from the hospital cost accounting system.

RESULTS

In 13 months, 50 patients with a hematologic disorder underwent mobilization. There were 34 cancellations or postponements of collections due to a low PB CD34 value in 13 patients. By use of our identified costs per initial collection, this resulted in a savings of 67,660 US dollars.

CONCLUSIONS

This prospective study defines how the implementation of the PB CD34 value results in costs savings. A low PB CD34 value canceled or postponed a significant number of leukapheresis procedures, resulting in a substantial cost savings. Use of the PB CD34 value should be the standard of care during mobilization and peripheral blood progenitor cell collection.

The Expansion of Megakaryocyte Progenitors from CD34+-Enriched Mobilized Peripheral Blood Stem Cells Is Inhibited by Flt3-L

This study aimed to determine the optimal growth factor combination for expansion of megakaryocyte (Mk) progenitors with clonogenic potential from CD34+-enriched mobilized peripheral blood stem cells (PBSC). Mobilized PBSC were monocyte depleted and CD34+ enriched, then cultured with various combinations of interleukin-3 (IL-3), IL-6, IL-11, Flt3 ligand (Flt3-L), stem cell factor (SCF), granulocyte-macrophage colonystimulating factor (GM-CSF), and erythropoietin (EPO), using a 2(7-3) IV fractional factorial design. Expansion of Mk committed progenitors (CD41+) and primitive precursors (CD61+ CD34+) was determined using FACS and colony-forming assays. Amplification of Mk progenitor production was attributed to IL-3 (p < 0.002), SCF (p < 0.001), and GM-CSF (p < 0.05). Flt3-L inhibited the production of total CD61+ cells (p < 0.05), CD61+CD34+ cells (p < 0.03), and total CD41a+ cells (p < 0.01). Addition of Flt3-L to the optimum growth factor combination of megakaryocyte growth and development factor (MGDF), SCF, IL-3, and GM-CSF caused the greatest increase in total nucleated cells but reduced Mk progenitor expansion. There was also a 20% reduction in Mk+ colonies from cells expanded in the presence of Flt3-L. Factorial analysis identified the optimal combination of growth factors required to expand Mk precursors with clonogenic potential. The addition of Flt3-L to the optimal combination of MGDF, SCF, IL-3, and GM-CSF reduced both the fold expansion of Mk progenitors and Mk colony numbers.

High-dose versus low-dose cyclophosphamide in combination with G-CSF for peripheral blood progenitor cell mobilization

BACKGROUND

To compare the mobilizing effects and toxicities of two different doses of cyclophosphamide (CY) plus lenograstim (glycosylated G-CSF), we performed a prospective randomized study by enrolling patients suffering with either high-risk Non-Hodgkin's lymphoma (NHL) or breast cancer undergoing ablative chemotherapy.

METHODS

The NHL patients received 4 cycles of CHOP and the breast cancer patients received 2-3 cycles of FAC (FEC) adjuvant chemotherapy. Then, the patients were randomly allocated to receive CY 4 g/m2 (arm A) or 1.5 g/m2 (arm B) in combination with lenograstim. Large volume leukapheresis was carried out and it was continued daily until the target cell dose of 2 x 10(6) CD34+ cell/kg was reached.

RESULTS

Twenty-seven patients were enrolled in the study. The median number of leukaphereis sessions actually performed was 2.5 sessions in arm A and 3 sessions in arm B. The target cell dose was obtained with the median number of one leukapheresis session in both arms of the study (p=0.09). The collected number of CD34+ cells in the leukapheresis products was higher in arm A than arm B (22.4 vs. 9.9 x 10(6)/kg, respectively, p=0.05). Grade III or IV leukopenia was present in 14/15 patients (94%) in arm A and in 1/12 patients (8%) in arm B (p<0.0001). Grade Ill or IV thrombocytopenia was present in 8/15 patients (54%) in arm A, but this was not present in any patients of arm B (p=0.0004). Neutropenic fever occurred in 6/15 patients (40%) in arm A, and in 1/12 patients (8%) in arm B (p=0.09). The hematological recovery of the leukocytes and platelets after transplantation was not statistically different between the two doses.

CONCLUSION

Low-dose CY plus lenograstim is a safe and effective mobilizing regimen.

Ex Vivo Expansion of Megakaryocyte Progenitor Cells: Cord Blood Versus Mobilized Peripheral Blood

Thrombocytopenia is a problematic and potentially fatal occurrence after transplantation of cord blood stem cells. This problem may be alleviated by infusion of megakaryocyte progenitor cells. Here, we compared the ability of hematopoietic progenitor cells obtained from cord blood and expanded in culture to that of mobilized peripheral blood cells. The CD34(+) cells were plated for 10 days in presence of thrombopoietin (TPO) alone and combined with stem cell factor (SCF), Flt3-ligand (FL), interleukin-3 (IL-3), IL-6, and IL-11. Cells were analyzed for the CD41 and CD42b expression and for their ploidy status. Ex vivo produced platelets were enumerated. We show that (1) TPO alone was able to induce differentiation of CD34(+) cells into CD41(+) cells, with limited total leucocyte expansion; (2) the addition of SCF to TPO decreased significantly CD41(+) cell percentage in CB, but not in MPB; and (3) in CB, the addition of FL, IL-6, and IL-11 to TPO increased the leukocyte expansion with differentiation and terminal maturation into MK lineage. In these conditions, high numbers of immature CD34(+)CD41(+) MK progenitor cells were produced. Our results thereby demonstrate a different sensitivity of CB and MPB cells to SCF, with limited CB MK differentiation. This different sensitivity to SCF (produced constitutively by BM stromal cells) could explain the longer delay of platelet recovery after CB transplant. Nevertheless, in CB, the combination of TPO with FL, IL-6, and IL-11 allows generation of a suitable number of immature MK progenitor cells expressing both CD34 and CD41 antigens, which are supposed to be responsible for the platelet recovery after transplantation.

Characterization of banked umbilical cord blood hematopoietic progenitor cells and lymphocyte subsets and correlation with ethnicity, birth weight, sex, and type of delivery: a Cord Blood Transplantation (COBLT) Study report

BACKGROUND

The Cord Blood Transplantation (COBLT) Study banking program was initiated in 1996. The study goals were to develop standard operating procedures for cord blood (CB) donor recruitment and banking and to build an ethnically diverse unrelated CB bank to support a transplantation protocol.

STUDY DESIGN AND METHODS

The hematopoietic progenitor cell (HPC) and lymphocyte subset (LS) content of approximately 8000 CB units were characterized, and these results were correlated with donor ethnicity, birth weight, gestational age, sex, and type of delivery.

RESULTS

There was a significant correlation of CD34+ cell count with colony-forming unit (CFU)-granulocyte-macrophage (r=0.68, p<0.001), CFU-granulocyte-erythroid-macrophage-megakaryocyte (r=0.52, p<0.001), burst-forming unit-erythroid (BFU-E; r=0.61, p<0.001), and total CFUs (r=0.67, p<0.001). Nucleated red blood cell count was significantly correlated with total CD34+ (r=0.56, p<0.001), total CFU (r=0.50, p<0.001), BFU-E (r=0.48, p<0.001), and counts of CD34+ subsets (p<0.001). Caucasian ethnicity was significantly correlated with higher CD3+/CD4+, CD19+, and CD16+/CD56+ LSs. Furthermore, CD34+/CD38- and CD34+/CD61+ CB units (HPC-C) were significantly lower in African American and Asian persons compared to Caucasian and Hispanic persons. Male sex was associated with significantly fewer CD3+/CD4+, CD19+, and CD16+/CD56+ but increased CD3+/CD8+ LSs (p<0.001). Finally, cesarean section was associated with significantly higher total CFU and CD16+/CD56+ but lower CD3+/CD4+, CD3+/CD8+, and CD19+ LSs.

CONCLUSION

These results provide a standard and range for uniformly processed HPC-C progenitor cells and LSs. CB progenitor cells and/or LSs may in the future predict for rapidity of engraftment, incidence of graft-versus-host disease, speed and quality of immunore- constitution, graft-versus-tumor effects, and/or success of gene transfection after CB transplantation.

Delayed platelet engraftment in group O patients after autologous progenitor cell transplantation

BACKGROUND

Fucosylated glycans, including H-antigen, play critical roles in hematopoietic progenitor cell homing, adhesion, growth, and differentiation. H-active antigens are strongly expressed on CD34+ progenitor cells and committed megakaryocytic progenitors and may mediate adhesion to marrow stromal fibroblasts. We examined the possible influence of donor ABO type on platelet (PLT) engraftment after autologous peripheral blood progenitor cell transplant (PBPCT).

STUDY DESIGN AND METHODS

A retrospective analysis of all patients who underwent a single autologous PBPCT between 1996 and 2000 were reviewed. Neutrophil and PLT engraftment were compared by patient ABO type and CD34+ cell dose by t test, chi-square test, analysis of variance, Kaplan-Meier probability, and log-rank test.

RESULTS

Engraftment data was available in 195 patients. PLT engraftment was delayed in all patients, regardless of ABO type, at CD34+ PBPC doses of 2x10(6) to 3x10(6) per kg (p<0.001). When examined by ABO type, late PLT engraftment (PLT count>50x10(9)/L) was significantly delayed in group O patients relative to all non-group O patients (32.4 days vs. 19.6 days, p<0.001). Approximately 50 percent of group O patients required more than 40 days to achieve late PLT recovery (p<0.005).

CONCLUSIONS

A group O phenotype may be associated with delayed PLT engraftment at lower CD34 doses.

Impact of CD34 subsets on engraftment kinetics in allogeneic peripheral blood stem cell transplantation

Our objective was to evaluate, probably for the first time, the impact of CD34 subsets on engraftment kinetics in allogeneic PBSC transplantation (PBSCT). PBSC graft components were analyzed in 62 cases for the absolute count/kg of total CD34+ and the following subsets: DR- and +, CD71+/-, CD38+/-, CD33+/- and CD61+/-. Time to ANC >0.5 and >1 x 10(9)/l and platelets >20 and >50 x 10(9)/l was reported. The median value for each parameter was used to discriminate rapid from slow engraftment. Four parameters showed significant predictive power of early neutrophil engraftment, namely CD34+ /DR- (P = 0.002), CD34+/38- (P = 0.02), CD34+/CD61- (P = 0.04) and total CD34+ cell dose (P = 0.04). Four parameters showed significant predictive power of early platelet engraftment, namely CD34+/CD61+ (P = 0.02), CD34+ /CD38- and total CD34+ cell dose (P = 0.04) and CD34+ /CD71- (P = 0.05). Comparing patients who received > to those who received < the threshold dose(s), only CD34+ /CD38- lost its significance for neutrophil engraftment; and only CD34+ /CD61+ retained its significance for platelet engraftment (P = 0.03); furthermore, the former group required significantly fewer platelet transfusions (P = 0.018). We concluded that in allogeneic PBSCT, the best predictor of early neutrophil engraftment is the absolute CD34+ /DR- and for early platelet engraftment is the absolute CD34+ /CD61+ cell dose.

Mathematical modeling of granulocyte reconstitution after high-dose chemotherapy with stem cell support: effect of post-transplant G-CSF treatment

Cancer patients treated with high-dose chemotherapy and autotransplanted with peripheral blood progenitor cells most often reconstitute neutrophils (> 0.5 x 10(9)c/l) 8-16 days after the initiation of treatment. By means of a mathematical model of human granulopoiesis, the present work assesses the effect of administering granulocyte colony stimulating factor (G-CSF) post-transplant to reduce engraftment time, and also assesses the effect of delaying initiation of G-CSF treatment relative to a general schedule. Hematopoietic progenitor cells from 21 breast cancer patients were mobilized by chemotherapy followed by G-CSF injections. Purified CD34+ cells taken from the mobilized blood were infused 3 days after termination of chemotherapy. Patients were given subcutaneous injections of G-CSF post-transplant (5 microg/kg every 12 h). Neutrophil counts calculated from a mathematical model were compared with data from individual patients. These results were also compared with data and modeling results from a group of 19 lymphoma patients given no post-transplant G-CSF therapy. The observed engraftment times were associated with the number of CFU-GM cells in the reinfused blood graft and the administration of post-transplant G-CSF. The latter finding was most predominant in patients given < 5.0 x 10(5) CFU-GM/kg bw. These tendencies were well captured by the model. Interestingly, the model showed no major differences in time to engraft neutrophils if the initiation of G-CSF was postponed for up to 5 days after transplantation. Our findings indicate that the present mathematical model of neutrophil recovery following high-dose therapy correlates with clinical observations and can potentially be used to predict time to neutrophil recovery.

CD34+ CD90+ cells and late hematopoietic reconstitution after autologous peripheral blood stem cell transplantation

Autologous peripheral blood stem cell transplantation (PBSCT) has been demonstrated to result in rapid. stable long-term engraftment. However, there has been considerable debate concerning the cells responsible for early and late hematopoietic reconstitution after PBSCT. Recently, CD34+ hematopoietic stem and progenitor cells have been clearly divided into two subpopulations by flow cytometry; namely undifferentiated pluripotent stem cells and differentiated committed progenitor cells. However, only a few studies have defined which subset contained in graft products might be the most predictive for late hematopoietic reconstitution after PBSCT. In this review, we present updated information regarding the relationships between the number of infused CD34+ cells or their immature subsets such as CD34+ CD90+ cells and the late hematopoietic reconstitution after PBSCT, and discuss the threshold dose of CD34 + CD90+ cells required for sustained long-term engraftment.

High CD34+ cell dose promotes faster platelet recovery after autologous stem cell transplantation for acute myeloid leukemia

We studied platelet engraftment in 58 patients with acute myeloid leukemia in first remission treated with autologous stem cell transplantation (ASCT) to determine whether CD34+ cell doses >10 x 10(6)/kg were associated with faster platelet engraftment. We compared engraftment rates in patients receiving CD34+ doses between 5 and 10 x 10(6)/kg (standard-dose ASCT) with those receiving doses > or =10 x 10(6)/kg (high-dose [HD] ASCT). We also studied neutrophil engraftment rates and platelet and red blood cell transfusion requirements. In multivariate adjusted models, the rate of platelet recovery to > or =20,000/microL was 4-fold greater among subjects who received HD-ASCT (hazard ratio [HR], 4.1; confidence interval [CI], 1.8-9.2; P =.001), with median recovery times of 14 versus 28 days. The rate of platelet recovery to > or =50,000/microL was 2-fold greater (HR, 2.1; CI, 1.3-5.9; P =.01), with median recovery times of 19 versus 46 days. Faster platelet recovery resulted in the need for fewer platelet transfusions among the subjects who received HD-ASCT (mean transfusions, 3.7 versus 9.8; P =.005). Although not statistically significant, neutrophil recovery data in the adjusted model suggested a similar effect in the HD-ASCT group, with faster engraftment times at absolute neutrophil counts >500/microL (median, 9.2 versus 12 days; HR, 1.6; CI, 0.69-3.5; P =.29) and absolute neutrophil counts >1000/microL (median, 9.5 versus 12 days; HR, 1.3; CI, 0.56-2.8; P =.58). Subjects who received HD-ASCT required fewer red blood cell transfusions (4.0 versus 9.8 units; P =.01). Our findings suggest that CD34+ cell doses >10 x 10(6)/kg CD34+ result in faster engraftment and fewer red blood cell and platelet transfusions.

Cotransplantation of human mesenchymal stem cells enhances human myelopoiesis and megakaryocytopoiesis in NOD/SCID mice

OBJECTIVE

For approximately 5% of autologous transplant recipients and a higher proportion of allogeneic transplant recipients, low level and delayed platelet engraftment is an ongoing problem. Mesenchymal stem cells (MSC), which can be derived from bone marrow as well as other organs, are capable of differentiation into multiple cell types and also support hematopoiesis in vitro. Because cotransplantation of marrow-derived stromal cells has been shown to enhance engraftment of human hematopoietic stem cells, we hypothesized that cotransplantation of MSC could enhance platelet and myeloid cell development.

MATERIALS AND METHODS

We tested this hypothesis by transplantation of CD34-selected mobilized human peripheral blood stem cells (PBSC) into sublethally irradiated NOD/SCID mice with or without culture-expanded human MSC and evaluated human myeloid, lymphoid, and megakaryocytic engraftment with flow cytometry and in vitro cultures.

RESULTS

We find that MSC cotransplantation enhances human cell engraftment when a limiting dose (<1 x 10(6)) of CD34 cells is administered. This enhancement is characterized by a shift in the differentiation of human cells from predominantly B lymphocytes to predominantly CD13(+), CD14(+), and CD33(+) myeloid cells with a corresponding increase in myeloid CFU in the marrow. Megakaryocytopoiesis is enhanced by MSC cotransplantation as assessed by an increase in both marrow CFU-MK and circulating human platelets. In contrast, MSC do not affect the percentage of human bone marrow cells that expresses CD34(+).

CONCLUSIONS

Cotransplantation of human mesenchymal stem cells with CD34(+)-selected hematopoietic stem cells enhances myelopoiesis and megakaryocytopoiesis.

Optimising parameters for peripheral blood leukapheresis after r-metHuG-CSF (filgrastim) and r-metHuSCF (ancestim) in patients with multiple myeloma: a temporal analysis of CD34(+) absolute counts and subsets

Patients (n = 69) with multiple myeloma undergoing peripheral blood stem cell collection (PBSC) were treated with cyclophosphamide and a combination of recombinant methionyl human granulocyte colony-stimulating factor (r-metHuG-CSF, filgrastim) and recombinant methionyl human stem cell factor (r-metHuSCF, ancestim). The objectives of this study were to determine: (1) The proportion of patients reaching a target yield of >or=5 x 10(6) CD34(+) cells/kg in one or two successive large-volume (20 liter) leukapheresis procedures; (2) the optimal collection time for leukapheresis; (3) mobilization kinetics of CD34(+) subsets in response to G-CSF/SCF. All patients were mobilized with cyclophosphamide (2.5 g/m(2)) on day 0 followed by filgrastim (10 microg/kg ) plus ancestim (20 microg/kg) commencing day 1 and continuing to day 11 or 12. Of the 65 evaluable patients, 57 were considered not heavily pretreated and 96.5% obtained a target of >or=5 x 10(6)/kg in one collection. The median CD34(+) cells/kg was 39.5 x 10(6) (range: 5.2-221.2 x 10(6)). Subset analysis demonstrated the number of CD38(-), CD33(-), and CD133(+) peaked at day 11; and CD34(+), CD90(+) cells peaked at day 10. The optimum day for leukapheresis was determined to be day 11. The median absolute peripheral blood CD34(+) cell numbers on day 11 was 665 x 10(6)/l (range: 76-1481 x 10(6)/l). Eight of the 10 heavily pretreated patients were evaluable: three achieved the target dose in one leukapheresis (37.5%) and three (37.5%) achieved the target dose with two leukaphereses. Use of this mobilization strategy allowed the collection of high numbers of CD34(+) cells and early progenitors and the ability to predictably schedule leukapheresis.

Reassessing the definition of myeloid engraftment after autotransplantation: it is not necessary to see 0.5 x 10(9)/l neutrophils on 3 consecutive days to define myeloid recovery

The time to myeloid recovery after autologous hematopoietic stem cell transplantation (HSCT) is usually defined as the first of 3 consecutive days with an absolute neutrophil count (ANC) of >or=0.5 x 10(9)/l (ANC500). Universal documentation of ANC500 for 3 consecutive days, historically required to ensure robust myeloid recovery, has become difficult with a trend towards early discharge and outpatient HSCT. We studied 90 autografted patients to see how frequently ANC declined after having reached >or=0.5 x 10(9)/l. ANC500 was documented on 2 and 3 consecutive days in 14 and 63 patients, respectively. ANC increased by a median of 213% from the 1st to the 2nd day (rise in 75 and unchanged in two), and by a median of 142% from the 2nd day to the 3rd (rise in 60, unchanged in one, and decline in two; higher than the 1st day in the latter three). The increase from the 1st to the 3rd day was 13-3433% (median, 557%). Thus, in all 63 patients, no decline below ANC500 was seen, and the first day with ANC500 was also the first of 3 consecutive days with ANC500. The remaining 13 patients had repeat counts 2-7 days after the 1st day with ANC500 documenting further increase in ANC with no evidence of failed engraftment. These data show that the first day with ANC500 is also consistently the first of 3 consecutive days with ANC500 in autografted patients. Therefore, the traditional definition of myeloid engraftment should be changed to consider the first day with ANC500 as the day of engraftment without necessarily documenting ANC500 on the subsequent 1-2 days. This simple change in definition has significant implications for how data are reported to transplant registries and how peer-review organizations such as the Foundation for the Accreditation of Hematopoietic Cell Therapy (FAHCT) define completeness of data.

Influence of the different CD34+ and CD34- cell subsets infused on clinical outcome after non-myeloablative allogeneic peripheral blood transplantation from human leucocyte antigen-identical sibling donors

Currently, no information is available regarding the influence of the different CD34+ cell subsets infused on the haematopoietic recovery, following non-myeloablative allogeneic peripheral blood stem cell transplantation (allo-PBSCT). We have explored, in a group of 13 patients receiving non-myeloablative allo-PBSCT from human leucocyte antigen-identical sibling donors, the influence of the total dose of CD34+ haematopoietic progenitor cells (HPC) infused, compared with that of the different CD34+ HPC and CD34- leucocyte subsets in the leukapheresis samples, on both engraftment and clinical outcome. The overall numbers of total CD34+ HPC (P = 0.002) and myelomonocytic-committed CD34+ HPC infused (P = 0.0002) were strongly associated with neutrophil recovery (> 1 x 109 neutrophils/l), the latter being the only independent parameter influencing neutrophil recovery. Regarding long-term engraftment, only the number of immature CD34+ HPC infused/kg correlated with the duration of hospitalization in the first 2 years after discharge (r = -0.75, P = 0.005). Both the overall amount of CD34+ HPC and the number of myelomonocytic CD34+ HPC infused showed a significant influence on the risk of graft-versus-host disease (GVHD). Thus, the overall probability of GVHD was 100%vs 25% for patients receiving >/= 5 x 106 CD34+ HPC or >/= 3.5 x 106 of myelomonocytic-committed CD34+ HPC vs lower doses (P = 0.013). None of the other CD34+ and CD34- cell subsets analysed correlated with development of GVHD. In summary, our results suggest that in non-myeloablative allo-PBSCT, high numbers of CD34+ HPC, especially the myelomonocytic-committed CD34+ progenitors, lead to rapid neutrophil engraftment. However, they also strongly impair clinical outcome by increasing the incidence of GVHD.