Development of a microfluidic device for determination of cell osmotic behavior and membrane transport properties

An understanding of cell osmotic behavior and membrane transport properties is indispensable for cryobiology research and development of cell-type-specific, optimal cryopreservation conditions. A microfluidic perfusion system is developed here to measure the kinetic changes of cell volume under various extracellular conditions, in order to determine cell osmotic behavior and membrane transport properties. The system is fabricated using soft lithography and is comprised of microfluidic channels and a perfusion chamber for trapping cells. During experiments, rat basophilic leukemia (RBL-1 line) cells were injected into the inlet of the device, allowed to flow downstream, and were trapped within a perfusion chamber. The fluid continues to flow to the outlet due to suction produced by a Hamilton Syringe. Two sets of experiments have been performed: the cells were perfused by (1) hypertonic solutions with different concentrations of non-permeating solutes and (2) solutions containing a permeating cryoprotective agent (CPA), dimethylsulfoxide (Me(2)SO), plus non-permeating solute (sodium chloride (NaCl)), respectively. From experiment (1), cell osmotically inactive volume (V(b)) and the permeability coefficient of water (L(p)) for RBL cells are determined to be 41% [n=18, correlation coefficient (r(2)) of 0.903] of original/isotonic volume, and 0.32+/-0.05 microm/min/atm (n=8, r(2)>0.963), respectively, for room temperature (22 degrees C). From experiment (2), the permeability coefficient of water (L(p)) and of Me(2)SO (P(s)) for RBL cells are 0.38+/-0.09 microm/min/atm and (0.49+/-0.13) x 10(-3)cm/min (n=5, r(2)>0.86), respectively. We conclude that this device enables us to: (1) readily monitor the changes of extracellular conditions by perfusing single or a group of cells with prepared media; (2) confine cells (or a cell) within a monolayer chamber, which prevents imaging ambiguity, such as cells overlapping or moving out of the focus plane; (3) study individual cell osmotic response and determine cell membrane transport properties; and (4) reduce labor requirements for its disposability and ensure low manufacturing costs.

Connective tissue growth factor (CTGF) expression and outcome in adult patients with acute lymphoblastic leukemia

We compared the gene expression profile of adult acute lymphoblastic leukemia (ALL) to normal hematopoietic and non-ALL samples using oligonucleotide arrays. Connective tissue growth factor (CTGF) was the highest overexpressed gene in B-cell ALL compared with the other groups, and displayed heterogeneous expression, suggesting it might have prognostic relevance. CTGF expression was examined by quantitative reverse transcriptase-polymerase chain reaction (ORT-PCR) on 79 adult ALL specimens. CTGF expression levels were significantly increased in ALL cases with B-lineage (P < .001), unfavorable cytogenetics (P < .001), and blasts expressing CD34 (P < .001). In a multivariate proportional hazards model, higher CTGF expression levels corresponded to worsening of overall survival (OS; hazard ratio 1.36, for each 10-fold increase in expression; P = .019). Further studies are ongoing to confirm the prognostic value of CTGF expression in ALL and to investigate its role in normal and abnormal lymphocyte biology.

CD34+ hematopoietic stem-progenitor cell microRNA expression and function: a circuit diagram of differentiation control

MicroRNAs (miRNAs) are a recently identified class of epigenetic elements consisting of small noncoding RNAs that bind to the 3' untranslated region of mRNAs and down-regulate their translation to protein. miRNAs play critical roles in many different cellular processes including metabolism, apoptosis, differentiation, and development. We found 33 miRNAs expressed in CD34+ hematopoietic stem-progenitor cells (HSPCs) from normal human bone marrow and mobilized human peripheral blood stem cell harvests. We then combined these data with human HSPC mRNA expression data and with miRNA-mRNA target predictions, into a previously undescribed miRNA:mRNA interaction database called the Transcriptome Interaction Database. The in silico predictions from the Transcriptome Interaction Database pointed to miRNA control of hematopoietic differentiation through translational control of mRNAs critical to hematopoiesis. From these predictions, we formulated a model for miRNA control of stages of hematopoiesis in which many of the genes specifying hematopoietic differentiation are expressed by HSPCs, but are held in check by miRNAs until differentiation occurs. We validated miRNA control of several of these target mRNAs by demonstrating that their translation in fact is decreased by miRNAs. Finally, we chose miRNA-155 for functional characterization in hematopoiesis, because we predicted that it would control both myelopoiesis and erythropoiesis. As predicted, miRNA-155 transduction greatly reduced both myeloid and erythroid colony formation of normal human HSPCs.

Reduced incidence of acute and chronic graft-versus-host disease with the addition of thymoglobulin to a targeted busulfan/cyclophosphamide regimen

To reduce the incidence of graft-versus-host disease (GVHD), we added Thymoglobulin (THY) to dose-adjusted oral busulfan plus cyclophosphamide (targeted BUCY). The starting dose of THY was 4.5 mg/kg given over days -3, -2, and -1, escalated in steps of 1.5 mg/kg in cohorts of 15 evaluable patients. Escalation was dependent on acute GVHD incidence and Epstein-Barr virus reactivation. Fifty-six patients with myelodysplastic syndrome and other myeloid disorders underwent transplantation with peripheral blood progenitor cells from related (n=30) or unrelated (n=26) donors. All but 2 patients achieved engraftment, and 56% survived in remission beyond 1 year. The incidence of acute GVHD was 50%, and that of chronic GVHD was 34%. The highest THY dose was 6.0 mg/kg, a dose at which 1 patient experienced Epstein-Barr virus reactivation. Nine patients did not receive the prescribed THY dose. Results were comparable for related and unrelated transplants and for patients given 4.5 or 6.0 mg/kg THY. Among 27 myelodysplastic syndrome patients (14 with related and 13 with unrelated donors) who underwent transplantation concurrently with targeted BUCY without THY, the incidence of acute and chronic GVHD was 82%. Thus, THY 4.5 to 6.0 mg/kg seemed beneficial for GVHD prevention in BUCY-conditioned patients who underwent transplantation with peripheral blood progenitor cells, although relapse-free survival did not differ significantly from that in comparable historical controls not given THY.

HES1 inhibits cycling of hematopoietic progenitor cells via DNA binding

Notch signaling is implicated in stem cell self-renewal, differentiation, and other developmental processes, and the Drosophila hairy and enhancer of split (HES) 1 basic helix-loop-helix protein is a major downstream effector in the Notch pathway. We found that HES1 was expressed at high levels in the hematopoietic stem cell (HSC)-enriched CD34+/[CD38/Lin](- /low) subpopulation but at low levels in more mature progenitor cell populations. When CD34+ cells were cultured for 1 week, the level of HES1 remained high in the CD34+ subset that had remained quiescent during ex vivo culture but was reduced in CD34+ cells that had divided. To investigate the effects of HES1 in human and mouse hematopoietic stem-progenitor cells (HSPCs), we constructed conditional lentiviral vectors (lentivectors) to introduce transgenes encoding either wild-type HES1 or a mutant lacking the DNA-binding domain (BHES1). We found that lentivector-mediated HES1 expression in CD34+ cells inhibited cell cycling in vitro and cell expansion in vivo, associated with upregulation of the cell cycle inhibitor p21(cip1/Waf1) (p21). The HES1 DNA-binding domain was required for these actions. HES1 did not induce programmed cell death or alter differentiation in HSPCs, and while short-term repopulating activity was reduced in HES1-transduced mouse and human cells, long-term reconstituting HSC function was preserved. Our data characterize the complex, cell context-dependent actions of HES1 as a major downstream Notch signaling regulator of HSPC function.

Collection of blood stem cells from patients with sickle cell anemia

Prior to initiating gene therapy trials for sickle cell disease (SCD), methods to collect sufficient numbers of hematopoietic stem and progenitor cells will need to be developed. Bone marrow harvest entails significant morbidity that could be severe in patients with SCD. In addition, an ability to perform repeated stem cell collections so that several transfers of genetically modified cells could be attempted would be advantageous. In other settings, apheresis collection of mobilized blood stem cells has become the preferred source of stem cells for transplantation. Unfortunately, patients with SCD do not tolerate granulocyte-colony stimulating factor and therefore cannot be mobilized using these conventional methods. In this pilot study, we investigated whether withdrawal of hydroxyurea therapy results in an increase in circulating numbers of CD34+ cells and hematopoietic progenitors. In addition, we performed leukapheresis in one patient with severe SCD in an attempt to determine whether blood stem cell collection can be performed safely in patients who would be candidates for SC gene therapy trials. Our results highlight some of the potential difficulties in initiating gene therapy clinical trials for sickle cell disease.

High doses of transplanted CD34+ cells are associated with rapid T-cell engraftment and lessened risk of graft rejection, but not more graft-versus-host disease after nonmyeloablative conditioning and unrelated hematopoietic cell transplantation

This report examines the impact of graft composition on outcomes in 130 patients with hematological malignancies given unrelated donor granulocyte-colony-stimulating-factor-mobilized peripheral blood mononuclear cells (G-PBMC) (n = 116) or marrow (n = 14) transplantation after nonmyeloablative conditioning with 90 mg/m(2) fludarabine and 2 Gy TBI. The median number of CD34(+) cells transplanted was 6.5 x 10(6)/kg. Higher numbers of grafted CD14(+) (P = 0.0008), CD3(+) (P = 0.0007), CD4(+) (P = 0.001), CD8(+) (P = 0.004), CD3(-)CD56(+) (P = 0.003), and CD34(+) (P = 0.0001) cells were associated with higher levels of day 28 donor T-cell chimerism. Higher numbers of CD14(+) (P = 0.01) and CD34(+) (P = 0.0003) cells were associated with rapid achievement of complete donor T-cell chimerism, while high numbers of CD8(+) (P = 0.005) and CD34(+) (P = 0.01) cells were associated with low probabilities of graft rejection. When analyses were restricted to G-PBMC recipients, higher numbers of grafted CD34(+) cells were associated with higher levels of day 28 donor T-cell chimerism (P = 0.01), rapid achievement of complete donor T-cell chimerism (P = 0.02), and a trend for lower risk for graft rejection (P = 0.14). There were no associations between any cell subsets and acute or chronic GVHD nor relapse/progression. These data suggest more rapid engraftment of donor T cells and reduced rejection rates could be achieved by increasing the doses of CD34(+) cells in unrelated grafts administered after nonmyeloablative conditioning.

Differences in F36VMpl-based in vivo selection among large animal models

Animal models are indispensable tools for understanding physiological and pathological processes, as well as for developing new therapies. Ultimately, the results of animal experimentation must provide information that can guide the development of therapeutic approaches in humans. Significant differences have been reported comparing a gene therapy approach between different animal models. However, little information exists describing differences among the available large animal models. Here we evaluated, in the hemopoietic cells of baboons, a system of selection that has previously demonstrated activity in mice, in dogs, and in human cells ex vivo. This system employs a derivative of the murine thrombopoietin receptor (F36Vmpl), which is conditionally activated in the presence of a small-molecule drug called a chemical inducer of dimerization (CID). Whereas cultured mouse, human, and, to a lesser extent, dog hemopoietic cells all proliferate in response to the F36Vmpl signal, we observed only a minor and variable response to the F36Vmpl signal in the cultured cells of baboons. Similarly, we have noted significant rises in the frequency of transduced hemopoietic cells in mice and in dogs upon CID administration in vivo; however, here we show that responses to CID administration in three baboons were modest and variable. These findings have general implications for the evaluation and development of new strategies for gene therapy.

Allogeneic peripheral blood stem cell graft composition affects early T-cell chimaerism and later clinical outcomes after non-myeloablative conditioning

We have studied the influence of cell subsets [CD34, CD3, CD4, CD8, CD14, CD20, natural killer (NK; CD3(-)/CD56(+)), NKT (CD3(+)/CD56(+)), DC1, and DC2 cells] of granulocyte colony-stimulating factor mobilized peripheral blood stem cells (PBSC) on early T-cell chimaerism and later clinical outcomes in 125 patients with haematological malignancies who received human leucocyte antigen (HLA)-matched related grafts after non-myeloablative conditioning. Conditioning consisted of 2 Gy total body irradiation (TBI) alone (n = 28), or 2 Gy TBI preceded by either 90 mg/m(2) fludarabine (n = 62) or planned autologous haematopoietic cell transplantation (HCT) (n = 35). Post-transplant immunosuppression included mycophenolate mofetil and ciclosporin. Multivariate analysis showed that higher numbers of grafted NK cells predicted higher early T-cell chimaerism (P = 0.03), while higher numbers of B cells were associated with better clinical outcomes and a higher risk for chronic graft-versus-host disease (P = 0.05). Higher numbers of CD14(+) cells were associated with worse overall survival (P = 0.03), while higher numbers of CD34(+) cells showed better survival (P = 0.03). The addition of fludarabine or autologous HCT predicted higher early T-cell chimaerism (P = 0.001), while advanced donor age predicted lower chimaerism (P < or = 0.02). Patients with aggressive diseases were at higher risk for relapse/disease progression, and shorter progression-free and overall survival (P < 0.01). These results suggest that the dosing of certain cellular subsets of PBSC products can influence important outcomes post-HCT after non-myeloablative conditioning.

Microarray and serial analysis of gene expression analyses identify known and novel transcripts overexpressed in hematopoietic stem cells

The human CD34(+)/CD38(-)/Lin(-) cell subset, comprising approximately 1-10% of the CD34(+) cell population, contains few of the less primitive hematopoietic (lineage-committed) progenitor cells (HPCs) but most of the primitive in vivo engrafting (lympho-)hematopoietic stem cells (HSCs). We analyzed gene expression in CD34(+)/CD38(-)/Lin(-) cell populations isolated from normal human adult donor bone marrow, neonatal placental/umbilical cord blood, and mobilized adult donor peripheral blood stem-progenitor cells. As measured by Affymetrix microarrays, 4746 genes were expressed in CD34(+)/CD38(-)/Lin(-) cells from all three tissues. We also determined the transcriptomes of the stem cell-depleted, HPC-enriched CD34(+)/[CD38/Lin](++) cell population from each tissue. Comparison of CD34(+)/CD38(-)/Lin(-) (HSC-enriched) versus CD34(+)/[CD38/Lin](++) (HPC-enriched, HSC-depleted) cells from each tissue yielded 81 genes overrepresented and 90 genes underrepresented, common to all three of the CD34(+)/CD38(-)/Lin(-) cell populations. These transcripts, which are selectively expressed in HSCs from all three tissues, include a number of known genes (e.g., transcription factors, receptors, and signaling molecules) that might play roles in key functions (e.g., survival, self-renewal, differentiation, and/or migration/adhesion) of human HSCs. Many genes/transcripts of unknown function were also detected by microarray analysis. Serial analysis of gene expression of the bone marrow HSC and HPC populations confirmed expression of most of the overrepresented transcripts for which reliable serial analysis of gene expression tags were detected and additionally suggested that current microarrays do not detect as many as 30% of the transcripts expressed in HSCs, including a number of previously unknown transcripts. This work is a step toward full definition of the transcriptome of normal human HSCs and may identify new genes involved in leukemogenesis and cancer stem cells.

Kinetics of engraftment in patients with hematologic malignancies given allogeneic hematopoietic cell transplantation after nonmyeloablative conditioning

We analyzed the kinetics of donor engraftment among various peripheral blood cell subpopulations and their relationship to outcomes among 120 patients with hematologic malignancies given hematopoietic cell transplantation (HCT) after nonmyeloablative conditioning consisting of 2 Gy total body irradiation (TBI) with or without added fludarabine. While patients rapidly developed high degrees of donor engraftment, most remained mixed donor/host chimeras for up to 180 days after HCT. Patients given preceding chemotherapies and those given granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cell (G-PBMC) grafts had the highest degrees of donor chimerism. Low donor T-cell (P = .003) and natural killer (NK) cell (P = .004) chimerism levels on day 14 were associated with increased probabilities of graft rejection. High T-cell chimerism on day 28 was associated with an increased probability of acute graft-versus-host disease (GVHD) (P = .02). Of 93 patients with measurable malignant disease at transplantation, 41 achieved complete remissions a median of 199 days after HCT; 19 of the 41 were mixed T-cell chimeras when complete remissions were achieved. Earlier establishment of donor NK-cell chimerism was associated with improved progression-free survival (P = .02). Measuring the levels of peripheral blood cell subset donor chimerisms provided useful information on HCT outcomes and might allow early therapeutic interventions to prevent graft rejection or disease progression.

Male DNA in female donor apheresis and CD34-enriched products

Increased risk of graft-versus-host disease (GVHD) has been described in recipients of hematopoietic stem cell transplantations when the donor is a parous woman. Cells from prior pregnancies are now known to persist in women and could contribute to GVHD. We asked whether male DNA (presumed fetal microchimerism) is present in apheresis products of female donors. A total of 50 samples were studied by using real-time quantitative polymerase chain reaction (PCR) for the Y chromosome-specific sequence DYS14. Among 29 growth factor-mobilized peripheral blood mononuclear cell (G-PBMC) products, 34% were positive for male DNA. Quantitative results, expressed as DNA genome equivalent of male cells per million host cells (gEq/mil), ranged from 0 to 35 gEq/mil. Among 21 CD34-enriched cell fractions, 48% were positive with a range of 0 to 357 gEq/mil. In summary, male DNA was frequently detected in G-PBMC and CD34-enriched products from female donors. Whether fetal microchimerism contributes to GVHD merits further investigation.

Pharmacologically regulated Fas-mediated death of adoptively transferred T cells in a nonhuman primate model

Conditional suicide genes derived from pathogens have been developed to confer drug sensitivity and enhance safety of cell therapy, but this approach is limited by immune responses to the transgene product. We examined a strategy to regulate survival of transferred cells based on induction of apoptosis through oligomerization of a modified human Fas receptor by a bivalent drug (AP1903). Three macaques (Macaca nemestrina) received autologous T cells retrovirally engineered to express a Fas suicide-construct (LV'VFas). High levels of transduced cells were present in blood following cell transfer, but LV'VFas(+) cells declined rapidly after AP1903 administration. A small fraction of LV'VFas(+) cells resisted elimination by AP1903, in part due to insufficient levels of transgene expression in resting T cells, because reactivation of these cells in vitro enhanced sensitivity to AP1903. An immune response to the transgene product was observed, but epitope mapping indicated the response was directed to discrete components of human LV'VFas that were variant with the corresponding macaque sequences. These data demonstrate that chemically induced dimerization can be used to regulate survival of adoptively transferred T cells in vivo.

HLA-matched unrelated donor hematopoietic cell transplantation after nonmyeloablative conditioning for patients with hematologic malignancies

A hematopoietic cell transplantation (HCT) approach was developed for elderly or ill patients with hematologic malignancies that employed nonmyeloablative conditioning to avoid common regimen-related toxicities and relied on graft-versus-tumor effects for control of malignancy. Eighty-nine patients, median age 53 years, were given fludarabine (90 mg/m2) and 2 Gy total body irradiation. Marrow (n = 18) or granulocyte colony-stimulating factor (G-CSF)-stimulated peripheral blood mononuclear cells (G-PBMCs; n = 71) were transplanted from unrelated donors matched for human leukocyte antigen A (HLA-A), -B, -C antigens and -DRB1 and -DQB1 alleles. Postgrafting immunosuppression included mycophenolate mofetil and cyclosporine. Donor T-cell chimerism was higher for G-PBMCs compared with marrow recipients. Durable engraftment was observed in 85% of G-PBMCs and 56% of marrow recipients. Cumulative probabilities of grade II, III, and IV acute graft-versus-host disease (GVHD) were 42%, 8%, and 2%, respectively. Nonrelapse mortality at day 100 and at 1 year was 11% and 16%, respectively. One-year overall survivals and progression-free survivals were 52% and 38%, respectively. G-PBMC recipients had improved survival (57% vs 33%) and progression-free survival (44% vs 17%) compared with marrow recipients. HLA-matched unrelated donor HCT after nonmyeloablative conditioning is feasible in patients ineligible for conventional HCT. G-PBMCs conferred higher donor T-cell chimerism, greater durable engraftment, and better progression-free and overall survivals compared with marrow.

A randomized phase III clinical trial of autologous blood stem cell transplantation comparing cryopreservation using dimethylsulfoxide vs dimethylsulfoxide with hydroxyethylstarch

Hematopoietic stem cells intended for autologous transplantation are usually cryopreserved in solutions containing 10% dimethylsulfoxide (DMSO, v/v) or 5% DMSO in combination with 6% hydroxyethylstarch (HES, w/v). We performed a single-blinded, randomized study comparing these cryoprotectant solutions for patients undergoing autologous peripheral blood stem cell (PBSC) transplantation. A total of 294 patients were evaluable; 148 received cells frozen with 10% DMSO and 146 received cells frozen in 5% DMSO/6% HES. Patients who received cells frozen with the combination cryoprotectant recovered their white blood cell count >or=1.0 x 10(9)/l at a median of 10 days, one day faster than those who received PBSC frozen with DMSO alone (P=0.04). Time to achieve neutrophil counts of >or=0.5 x 10(9) and >or=1.0 x 10(9)/l were similarly faster for the recipients of the cells frozen in the combination solution. This effect was more pronounced for patients who received quantities of CD34+ cells higher than the median for the population. Median time to discontinuation of antibiotic use was also one day faster for the recipients of cells cryopreserved with DMSO/HES (P=0.04). In contrast, median times to recovery of platelet count >or=20 x 10(9)/l were equivalent for each group (10 days; P=0.99) and the median numbers of red cell and platelet transfusions did not differ.

Bone marrow transplantation: how important is CD34 cell dose in HLA-identical stem cell transplantation?

A recent analysis of Fred Hutchinson Cancer Research Center data has been undertaken to investigate the association of infused CD34 cell dose with various clinical outcomes after HLA-identical transplantation. Separate assessments for unrelated vs related donors and the use of bone marrow or mobilized G-CSF stimulated peripheral blood mononuclear cells (G-PBMC) have been incorporated. The three primary findings are: (1) Higher CD34 dose results in better neutrophil and platelet recovery in all settings. (2) Higher CD34 doses (8 x 10(6)/kg) are associated with the development of more chronic graft-versus-host disease when using related G-PBMC. (3) Higher CD34 dose is correlated with improved survival after unrelated donor bone marrow transplantation. These data suggest that the CD34 content of a graft can have a significant impact on clinical outcome after allogeneic transplantation, but defining an optimal dose is dependent on both the type of donor and the stem cell source.

HLA-identical stem cell transplantation: is there an optimal CD34 cell dose?

A review of the published literature, supplemented with a recent analysis of Fred Hutchinson data, has been undertaken to investigate the association of infused CD34 cell dose with various clinical outcomes after HLA-identical transplantation. Separate assessments for unrelated vs related donors and the use of bone marrow or mobilized G-PBMC have been incorporated. The three primary findings are: (1) higher CD34 dose results in better neutrophil and platelet recovery in all settings; (2) high CD34 doses (>8 x 10(6)/kg) are associated with the development of more chronic GVHD when using related G-PBMC; (3) higher CD34 dose is correlated with improved survival after bone marrow transplantation, especially with unrelated donors. This is not seen when using G-PBMC. The data suggest that the CD34 content of the graft can have a significant impact on clinical outcome after allogeneic transplantation, but optimal dose is dependent on both donor type and stem cell source.

CD28 costimulation and immunoaffinity-based selection efficiently generate primary gene-modified T cells for adoptive immunotherapy

The introduction of an inducible suicide gene has been proposed as a strategy to exploit the antitumor reactivity of donor T cells after allogeneic hematopoietic stem cell transplantation but permit control of graft-versus-host disease. However, there are several obstacles to this approach that may impair the ability of T cells to function and survive in vivo. These include the requirement for in vitro activation or long-term culture to introduce the transgene and obtain therapeutic cell numbers, the toxicity of drug selection to enrich transduced cells, and the immunogenicity of the transgene-encoded products. Here we have developed a transduction and selection strategy for generating large numbers of polyclonal T cells transduced with a retroviral vector encoding the human low-affinity nerve growth factor receptor (LNGFR) for selection and a Fas-based suicide construct (LV'VFas). Ligation of CD28 in conjunction with a T-cell receptor signal permitted efficient transduction, substantially promoted T-cell growth, and contributed to the generation of gene-modified T cells that retained clonal diversity, functional properties, and a homing receptor profile similar to untransduced peripheral blood lymphocytes. Microbeads conjugated directly to antibody specific to LNGFR significantly improved the immunomagnetic selection of LV'VFas-modified T cells and assisted in scaling of the selection procedure to therapeutic cell numbers. Thus, these studies identified a strategy that requires only a brief ex vivo culture and does not use drug selection to obtain large numbers of functional gene-modified polyclonal T cells that can be used for adoptive immunotherapy.

Comparison of gene expression in CD34+ cells from bone marrow and G-CSF-mobilized peripheral blood by high-density oligonucleotide array analysis

A prospective randomized trial has shown that there is a survival advantage for allogeneic transplant recipients who received granulocyte colony-stimulating factor (G-CSF)-stimulated peripheral blood mononuclear cells (GPBMC) versus those who received bone marrow (BM) as a source of stem cells. The biological basis for this advantage is not clear and may be attributable to qualitative as well as quantitative differences in the CD34 cells, T cells, and/or the monocytes transplanted. To begin to address this issue, gene expression patterns in CD34 cells isolated from these 2 stem cell sources were compared to identify functional pathways that may distinguish these 2 populations. CD34 cells were isolated to purity from the BM and peripheral blood stem cells of multiple healthy donors. (The complete data set will be available at http://parma.fhcrc.org/lgraf upon publication.) Two separate RNA preparations from pooled samples from both sources were analyzed by Affymetrix Oligonucleotide Array chips for expression of over 6400 human genes. Comparative analyses among the samples showed that a small set of 28 sequences increased and 38 sequences decreased in expression more than 3-fold in both of the GPBMC samples compared to those in BM samples. More highly expressed genes include several for nuclear proteins and transcriptional factors. Functional categorization of the genes decreased in expression indicated sequences influential in cell cycle progression, in agreement with the recognized quiescence of circulating CD34 cells. Multiple transcriptional regulators and chemokines were also found to be decreased. These data emphasize that in addition to increased numbers of CD34 cells, G-CSF mobilization also results in significant qualitative changes. Whether they impact engraftment remains to be determined.

CD34 cell dose in granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cell grafts affects engraftment kinetics and development of extensive chronic graft-versus-host disease after human leukocyte antigen-identical sibling transplantation

A retrospective analysis of granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cell (G-PBMC) products harvested from healthy donors indicates significant variability in both the absolute number and relative proportion of CD34, CD3, and CD14 cells obtained. This report examined whether variations in the cellular composition of G-PBMC products correlated with clinical outcomes after myeloablative allogeneic transplantation. The numbers of CD34, CD3, and CD14 cells infused into 181 human leukocyte antigen (HLA)-identical sibling recipients were analyzed with respect to tempo of engraftment, acute graft-versus-host-disease (GVHD), clinical extensive chronic GVHD, overall survival, and disease relapse. Neither acute GVHD, overall survival, nor disease relapse was statistically significantly associated with CD34, CD3, or CD14 cell doses or the CD14 to CD3 ratio. CD3 and CD14 cell doses and CD14 to CD3 ratios did not correlate with the tempo of neutrophil and platelet engraftment. However, increasing CD34 cell numbers were significantly associated with accelerated neutrophil (P =.03) and platelet (P =.01) engraftment. Higher doses of CD34 cells (> 8.0 x 10(6)/kg) were also associated with a significantly increased hazard of clinical extensive chronic GVHD (HR = 2.3, 95% confidence interval [CI] 1.4-3.7, P =.001), but neither CD3 nor CD14 doses were statistically significantly associated with chronic GVHD. It was concluded that CD34 cell dose in G-PBMC grafts appears to affect both the engraftment kinetics and the development of clinical extensive chronic GVHD in HLA-identical sibling recipients but without a demonstrable impact on survival, relapse, and acute GVHD. Given the morbidity associated with extensive chronic GVHD, efforts to further accelerate engraftment in HLA-matched sibling transplants by increasing CD34 cell number in G-PBMC products may be counterproductive.

Trafficking of CD34+ cells into the peripheral circulation during collection of peripheral blood stem cells by apheresis

The number of CD34+ cells collected during apheresis is related to the volume of blood processed. In large-volume apheresis (LVL) procedure, more cells can be collected than were originally present in the peripheral blood at the start of the collection procedure. We prospectively studied the levels of CD34+ cells in the blood and apheresis product during LVL procedures for 21 patients with acute myelogenous leukemia or multiple myeloma. These patients experienced a slow decline in blood CD34+ cell concentrations during the apheresis procedure. No patient demonstrated a sustained rise in CD34+ cell counts as a result of the procedure. The number of CD34+ cells collected exceeded the number calculated to be in the peripheral blood at the start of the procedure by an average of 3.0-fold. The efficiency of collection for CD34+ cells averaged 92.6% and did not vary with speed of blood processing, diagnosis, or mobilization regimen. The calculated release of CD34+ cells from other reservoirs into the peripheral blood averaged 3.71 x 10(6)/min (range, 0.36-13.7 x 10(6)/min), and correlated (r = 0.82) with the concentration of these cells in the peripheral blood at the start of the procedure. These data show that the apheresis procedure used in this study does not affect the release of CD34+ cells in a cytokine-treated patient. LVL will result in collection of larger quantities of CD34+ cells than procedures involving processing of smaller volumes of blood, but the number of cells collected is limited by the rate of release of these cells into the peripheral circulation where they are accessible for collection.