Enumeration of CD34+ cells in cord blood: a variation on a single-platform flow cytometric method based on the ISHAGE gating strategy

Sepax-2 cell processing device: a study assessing reproducibility of concentrating thawed hematopoietic progenitor cells

Background

Autologous hematopoietic progenitor cell (HPC) transplantation is currently the standard of care for a fraction of patients with newly diagnosed myelomas and relapsed or refractory lymphomas. After high-dose chemotherapy, cryopreserved HPC are either infused directly after bedside thawing or washed and concentrated before infusion. We previously reported on the comparability of washing/concentrating HPC post-thaw vs. infusion without manipulation in terms of hematopoietic engraftment, yet settled for the prior favoring cell debris and DMSO removal. For almost two decades, automation of this critical step of washing/concentrating cells has been feasible. As part of continuous process verification, we aim to evaluate reproducibility of this procedure by assessing intra-batch and inter-batch variability upon concentration of thawed HPC products using the Sepax 2 S-100 cell separation system.

Methods

Autologous HPC collected from the same patient were thawed and washed either in two batches processed within a 3-4 h interval and immediately infused on the same day (intra-batch, n = 45), or in two batches on different days (inter-batch, n = 49) for those patients requiring 2 or more high-dose chemotherapy cycles. Quality attributes assessed were CD34+ cell recovery, viability and CD45+ viability; CFU assay was only performed for allogeneic grafts.

Results

Intra-batch and inter-batch median CD34+ cell recovery was comparable (75% vs. 73% and 77% vs. 77%, respectively). Similarly, intra-batch and inter-batch median CD45+ cell viability was comparable (79% vs. 80% and 79% vs. 78%, respectively). Bland-Altman analysis describing agreement between batches per patient revealed a bias close to 0%. Additionally, lower HPC recoveries noted in batch 1 were noted as well in batch 2, regardless of the CD34+ cell dose before cryopreservation, both intra- and inter-batch, suggesting that the quality of the collected product plays an important role in downstream recovery. Intrinsic (high mature and immature granulocyte content) and extrinsic (delay between apheresis and cryopreservation) variables of the collected product resulted in a significantly lower CD45+ viability and CD34+ cell recovery upon thawing/washing.

Conclusions

Automated post-thaw HPC concentration provides reproducible cell recoveries and viabilities between different batches. Implications of this work go beyond HPC to concentrate cell suspension/products during manufacturing of cell and gene therapy products.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03703-1.

In silico-labeled ghost cytometry

Characterization and isolation of a large population of cells are indispensable procedures in biological sciences. Flow cytometry is one of the standards that offers a method to characterize and isolate cells at high throughput. When performing flow cytometry, cells are molecularly stained with fluorescent labels to adopt biomolecular specificity which is essential for characterizing cells. However, molecular staining is costly and its chemical toxicity can cause side effects to the cells which becomes a critical issue when the cells are used downstream as medical products or for further analysis. Here, we introduce a high-throughput stain-free flow cytometry called in silico-labeled ghost cytometry which characterizes and sorts cells using machine-predicted labels. Instead of detecting molecular stains, we use machine learning to derive the molecular labels from compressive data obtained with diffractive and scattering imaging methods. By directly using the compressive 'imaging' data, our system can accurately assign the designated label to each cell in real time and perform sorting based on this judgment. With this method, we were able to distinguish different cell states, cell types derived from human induced pluripotent stem (iPS) cells, and subtypes of peripheral white blood cells using only stain-free modalities. Our method will find applications in cell manufacturing for regenerative medicine as well as in cell-based medical diagnostic assays in which fluorescence labeling of the cells is undesirable.

High-volume endurance exercise training stimulates hematopoiesis by increasing ACE NH2-terminal activity

One of the health benefits of endurance exercise training (ET) is the stimulation of hematopoiesis. However, the mechanisms underlying ET-induced hematopoietic adaptations are understudied. N-Acetyl-Seryl-Aspartyl-Lysyl-Proline (Ac-SDKP) inhibits proliferation of early hematopoietic progenitor cells. The angiotensin I-converting enzyme (ACE) NH2-terminal promotes hematopoiesis by inhibiting the anti-hematopoietic effect of Ac-SDKP. Here we demonstrate for the first time the role of ACE NH2-terminal in ET-induced hematopoietic adaptations. Wistar rats were subjected to 10 weeks of moderate-(T1) and high-(T2) volume swimming-training. Although both protocols induced classical ET-associated adaptations, only T2 increased plasma ACE NH2-domain activity (by 40%, P=0.0003) and reduced Ac-SDKP levels (by 50%, P<0.0001). T2 increased the number of hematopoietic stem cells (HSCs; ∼200%, P=0.0008), early erythroid progenitor colonies (∼300%, P<0.0001) and reticulocytes (∼500%, P=0.0007), and reduced erythrocyte lifespan (∼50%, P=0.022). Following, Wistar rats were subjected to T2 or T2 combined with ACE NH2-terminal inhibition (captopril (Cap) treatment: 10 mg.kg-1.day-1). T2 combined with ACE NH2-terminal inhibition prevented Ac-SDKP decrease and attenuated ET-induced hematopoietic adaptations. Altogether, our findings show that ET-induced hematopoiesis was at least partially associated with increased ACE NH2-terminal activity and reduction in the hematopoietic inhibitor Ac-SDKP.

Combined impact of HLA-allele matching and the CD34-positive cell dose on optimal unit selection for single-unit cord blood transplantation in adults

The combined effects of HLA-allele matching at six-loci (HLA-A, -B, -C, -DRB1, -DQB1, and -DPB1) and CD34⁺ cell dose on clinical outcomes were analyzed in 1,226 adult cases with single-unit unrelated cord blood transplantation. In the six-loci analysis, low HLA-allele matches did not significantly increase the overall mortality compared to higher matches, whereas in the five-loci analysis excluding HLA-DPB1, they caused a higher overall mortality (HR 1.42, p = .002), possibly due to the graft-versus-leukemia effect of HLA-DPB1 mismatches. A lower CD34⁺ cell dose (<.50 × 10⁵/kg) resulted in higher mortality and lower engraftment; these inferior outcomes were offset by high HLA-allele matches (7-10/10 match), while the inferior outcomes of low HLA-allele matches were improved by increasing the CD34⁺ cell dose. Consideration of the combined effects of the CD34⁺ cell dose and HLA matching may expand the options for transplantable units when HLA matching or the CD34⁺ cell dose is inadequate.

Validation of the single-platform ISHAGE protocol for enumeration of CD34+ hematopoietic stem cells in umbilical cord blood in a Brazilian center

Background

This study aims to validate the single-platform method for enumeration of CD34+ cells, by comparing the performance of two different commercial kits, as well as to evaluate the efficiency of the Accuri^TM C6 cytometer in providing direct counts of absolute cell numbers.

Method

We evaluated 20 samples from umbilical cord blood (UCB), comparing the two different methodologies for enumeration of CD34+ cells: single and dual-platform. For the assessment of the single-platform, Procount and SCE kits were used, both of which use fluorescent beads as a counting reference to obtain absolute CD34+ cells numbers. Moreover, after the acquisition of samples in flow cytometer Accuri^TM C6, following the protocol established for each kit, the number of CD34+ cells was recalculated, considering the cell count provided by the Accuri^TM C6.

Main Results

In our analysis, the results showed a strong correlation between the number of CD34+ cells/μL (r² = 0.77) when comparing the SCE kit and the current dual-platform method. On the other hand, the comparison between Procount kit and dual-platform results showed a moderate correlation for the number of CD34+/μL cells (r² = 0.64).

Conclusion

Our results showed that the Accuri^TM C6 flow cytometer can be used safely, applying both the dual and single platform analysis strategy. Considering the ISHAGE protocol-based single-platform approach, as the most appropriate methodology for CD34+ cells enumeration, our results demonstrated that the SCE kit has great potential for national standardization of UCB samples analysis methodology.

NEW HORIZONS ON STEM CELL CRYOPRESERVATION THROUGH THE ARTIFICIAL EYES OF CD 34+, USING MODERN FLOW CYTOMETRY TOOLS

Hematopoietic stem cell (HSC) cryopreservation is a critical step in autologous and cord blood transplantation (CBT). In most circumstances, cryopreservation is performed in a mixture containing dimethyl sulfoxide (DMSO), since DMSO is necessary to secure cell viability. Most centers use a controlled rate (slow) freezing before the long-term storage at vapor phase liquid nitrogen (LN₂) temperatures (≤ -160 °C). The primary objectives for laboratories supporting HSCT programs are to provide secure storage for leukapheresis and cord blood products, and to adequately characterize the functional properties of the grafts before their infusion. In the autologous setting, the large majority of the published results dealt with the assessment of the graft before cryopreservation. On the contrary, in CBT, before a CB unit is released, a sample obtained from a contiguous segment of that CB unit needs to be tested to verify HLA type and cell viability. The effects of graft handling, cryopreservation, storage and thawing on the recovery of CD34+ cells needs to be carefully analyzed and standardized on a global level. Some technical unresolved issues still limit the application of the ISHAGE derived single platform flow cytometry protocol for the assessment of the thawed material; based on these considerations, an adaptation of both the acquisition setting and the gating strategyis necessary for reliable measurement of CD34-expressing HSC in cryopreserved grafts. Artificial intelligence applied to "big data" may provide a new tool for improving advanced processing procedures and quality management guidelines in this area of investigation.

Standardization of a compensation matrix for the use in an ISHAGE-based single-platform for CD34+ stem cell quantitation on the FACSVia™ flow cytometer

INTRODUCTION

Becton Dickinson (BD) FACSVia™ is a recently developed flow cytometer with which worldwide clinical experience is limited. Recently, our center started using the single-platform BD Stem Cell Kit (BD SCE) for the quantitation of viable CD34+ (7-aminoactinomycin D-7-AAD-negative cells) on a BD FACSVia™. Currently, there are no formal recommendations for the fluorescence compensation of 7-AAD in this scenario.

METHODS

A 3-color fluorescence compensation matrix ("Optimized BD CS&T") was standardized based on the fluorescence of 7-AAD in samples of 27 individuals. The "Optimized BD CS&T" was compared with manual compensation (predicated method) and BD CS&T beads.

RESULTS

The analysis of the viable CD34+ cells/mm³ showed a very strong correlation between the manual compensation versus "Optimized BD CS&T" (r = 1.00) and manual versus BD CS&T (r = .99). The analysis of CD34+ viability (%) showed a very strong correlation for manual versus "Optimized BD CS&T" (r = .99). However, for manual versus BD CS&T, the correlation was inferior (r = .86). For viable CD34+ cells/mm³ , Bland-Altman plots showed a better concordance between manual and "Optimized BD CS&T" than between manual and BD CS&T. For CD34+ viability (%), the concordance was very good between manual and "Optimized BD CS&T", while there was a poor concordance between manual and BD CS&T.

CONCLUSION

"Optimized BD CS&T" matrix proved to be more precise than the conventional BD CS&T beads. The "Optimized BD CS&T" matrix can be used along with BD SCE kit on BD FACSVia™ flow cytometers.

Human Leukocyte Antigen and Red Blood Cells Impact Umbilical Cord Blood CD34+ Cell Viability after Thawing

Hematopoietic progenitor cell (HPC) transplantation is a treatment option for malignant and nonmalignant diseases. Umbilical cord blood (UCB) is an important HPC source, mainly for pediatric patients. It has been demonstrated that human leukocyte antigen (HLA) matching and cell dose are the most important features impacting clinical outcomes. However, UCB matching is performed using low resolution HLA typing and it has been demonstrated that the unnoticed mismatches negatively impact the transplant. Since we found differences in CD34+ viability after thawing of UCB units matched for two different patients (p = 0.05), we presumed a possible association between CD34+ cell viability and HLA. We performed a multivariate linear model (n = 67), comprising pre-cryopreservation variables and high resolution HLA genotypes separately. We found that pre-cryopreservation red blood cells (RBC), granulocytes, and viable CD34+ cell count significantly impacted CD34+ viability after thawing, along with HLA-B or -C (R2 = 0.95, p = 0.01; R2 = 0.56, p = 0.007, respectively). Although HLA-B*40:02 may have a negative impact on CD34+ cell viability, RBC depletion significantly improves it.

Fully automated, clinical-grade bone marrow processing: a single-centre experience

BACKGROUND

Clinical grade processing of harvested bone marrow is required in various clinical situations, particularly in the management of ABO mismatching in allogeneic haematopoietic stem cell transplantation (HSCT) and in regenerative medicine.

MATERIAL AND METHODS

We report a single-centre experience using a fully automated, clinical grade, closed system (Sepax, Biosafe, Switzerland). From 2003 to 2015, 125 procedures were performed in our laboratory, including buffy-coat production for HSCT (n=58), regenerative medicine in an orthopaedic setting (n=54) and density-gradient separation in a trial for treatment of critical limb ischaemia (n=13).

RESULTS

Buffy coat separation resulted in a median volume reduction of 85% (range, 75-87%), providing satisfactory red blood cell depletion (69%, range 30-88%) and a median recovery of CD34 cells of 96% (range, 81-134%) in the setting of allogeneic HSCT. Significantly greater volume reduction (90%; range, 90-92%) and red blood cell depletion (88%; range, 80-93%) were achieved by the new SmartRedux software released for Sepax2, validated in the last eight allogeneic HSCT. The density gradient separation programme resulted in complete red blood cell depletion associated with high CD34 recovery (69%; range, 36-124%). No reactions related to the quality of the product were reported. Time to engraftment following allogeneic HSCT was in the normal range. No cases of microbiological contamination related to the manipulation were reported.

DISCUSSION

Clinical grade, automated bone marrow manipulation with Sepax was shown to be effective, giving operator-independent results and could be used for a broad range of clinical applications.

Enhancing endogenous stem cells in the newborn via delayed umbilical cord clamping

There is currently no consensus among clinicians and scientists over the appropriate or optimal timing for umbilical cord clamping. However, many clinical studies have suggested that delayed cord clamping is associated with various neonatal benefits including increased blood volume, reduced need for blood transfusion, increased cerebral oxygenation in pre-term infants, and decreased frequency of iron deficiency anemia in term infants. Human umbilical cord blood contains significant amounts of stem and progenitor cells and is currently used in the treatment of several life-threatening diseases. We propose that delayed cord clamping be encouraged as it enhances blood flow from the placenta to the neonate, which is accompanied by an increase supply of valuable stem and progenitor cells, as well as may improve blood oxygenation and increase blood volume, altogether reducing the infant's susceptibility to both neonatal and age-related diseases.

GATA2 regulates differentiation of bone marrow-derived mesenchymal stem cells

The bone marrow microenvironment comprises multiple cell niches derived from bone marrow mesenchymal stem cells. However, the molecular mechanism of bone marrow mesenchymal stem cell differentiation is poorly understood. The transcription factor GATA2 is indispensable for hematopoietic stem cell function as well as other hematopoietic lineages, suggesting that it may maintain bone marrow mesenchymal stem cells in an immature state and also contribute to their differentiation. To explore this possibility, we established bone marrow mesenchymal stem cells from GATA2 conditional knockout mice. Differentiation of GATA2-deficient bone marrow mesenchymal stem cells into adipocytes induced accelerated oil-drop formation. Further, GATA2 loss- and gain-of-function analyses based on human bone marrow mesenchymal stem cells confirmed that decreased and increased GATA2 expression accelerated and suppressed bone marrow mesenchymal stem cell differentiation to adipocytes, respectively. Microarray analysis of GATA2 knockdowned human bone marrow mesenchymal stem cells revealed that 90 and 189 genes were upregulated or downregulated by a factor of 2, respectively. Moreover, gene ontology analysis revealed significant enrichment of genes involved in cell cycle regulation, and the number of G1/G0 cells increased after GATA2 knockdown. Concomitantly, cell proliferation was decreased by GATA2 knockdown. When GATA2 knockdowned bone marrow mesenchymal stem cells as well as adipocytes were cocultured with CD34-positive cells, hematopoietic stem cell frequency and colony formation decreased. We confirmed the existence of pathological signals that decrease and increase hematopoietic cell and adipocyte numbers, respectively, characteristic of aplastic anemia, and that suppress GATA2 expression in hematopoietic stem cells and bone marrow mesenchymal stem cells.

The Royan Public Umbilical Cord Blood Bank: Does It Cover All Ethnic Groups in Iran Based on HLA Diversity?

BACKGROUND

Umbilical cord blood (UCB) stem cells allow the transplantation of partially human leukocyte antigen (HLA)-matched grafts and are a valuable resource for the treatment of hematologic malignancies and heritable hematologic, immunologic and metabolic diseases, especially when a compatible bone marrow donor is unavailable. The aim of this study was to determine how many ethnic groups in Iran are covered by the available UCB units based on HLA diversity.

METHODS

From 2009 until mid-2013, 4,981 (30.3%) of the 16,437 UCB samples collected met the storage criteria and were cryopreserved at a public cord blood bank (CBB) in Tehran, Iran. HLA-A, -B and -DRB1 were typed in 1,793 samples.

RESULTS

The mean volume of the cryopreserved samples was 81.25 ± 20.3 ml. The range of total nucleated cells per unit was 51 × 10(7)-107 × 10(7). The most common HLA alleles were HLA-A*2 (17%) and HLA-A*24 (15.6%), HLA-B*35 (16.8%) and HLA-B*51 (13.9%), and HLA-DRB1*11 (20%) and HLA-DRB1*15 (14%). The predominant haplotypes were HLA-A*24-B*35-DRB1*11 (2%), HLA-A*02-B*50-DR*07 (1.8%), and HLA-A*02-B*51-DRB1*11 (1.5%).

CONCLUSIONS

Based on the HLA-DRB1 profiles, the UCB units available at the Royan public UCB bank are a potentially adequate resource for hematopoietic stem cell transplantation for Iranian recipients belonging to particular ethnic groups. Regular educational programs to improve the public knowledge of UCB for transplantation can enhance the public CBB stocks for all Iranian ethnic groups in the future.

Peripheral blood CD34+ cell monitoring after cyclophosphamide and granulocyte-colony-stimulating factor: an algorithm for the pre-emptive use of plerixafor

Plerixafor "on demand" after chemotherapy plus granulocyte-colony-stimulating factor (G-CSF) is efficient in peripheral stem cell mobilization, but the timing of administration and criteria for patient selection are under investigation. To devise an algorithm for the "on demand" use of plerixafor at the first mobilization attempt, we analyzed the kinetics of hematopoietic recovery and peripheral blood CD34+ cells in 107 patients treated with high-dose cyclophosphamide plus G-CSF. Fifty-one patients with myeloma were treated with cyclophosphamide 3-4 g/m(2) on day 0 followed by G-CSF 10 μg/kg from day + 6, and 56 patients with lymphoma received cyclophosphamide 6-7 g/m(2) followed by G-CSF 5 μg/kg from day + 1. Peripheral blood CD34+ cell monitoring was started on day + 8 in patients with myeloma and day + 10 in patients with lymphoma. The outcome of interest was a collection of ≤ 2 × 10(6) CD34+/kg. By a multivariate logistic regression model, CD34+ cell count < 10/μL at leukocyte recovery (> 1000/μL) or leukocyte count < 1000/μL after day + 12 in myeloma and day + 14 in lymphoma predicted the failure of mobilization by 2.7 and 2.8 times (p = 0.001 and p = 0.02) with a sensitivity of 89% and specificity of 88%, respectively. Plerixafor "on demand" may be considered in patients with myeloma and lymphoma with delayed hematopoietic recovery and < 10/μL CD34+ cells, as a first-line mobilization strategy.

Toward personalized cell therapies by using stem cells: seven relevant topics for safety and success in stem cell therapy

Stem cells, both embryonic and adult, due to the potential for application in tissue regeneration have been the target of interest to the world scientific community. In fact, stem cells can be considered revolutionary in the field of medicine, especially in the treatment of a wide range of human diseases. However, caution is needed in the clinical application of such cells and this is an issue that demands more studies. This paper will discuss some controversial issues of importance for achieving cell therapy safety and success. Particularly, the following aspects of stem cell biology will be presented: methods for stem cells culture, teratogenic or tumorigenic potential, cellular dose, proliferation, senescence, karyotyping, and immunosuppressive activity.

Evaluation of a xeno-free protocol for long-term cryopreservation of cord blood cells

Cord blood is regarded as a powerful source for adult stem cells. Cord blood transplants have been used successfully to treat children and adults in autologous and allogeneic settings. Nevertheless, in many cases, the clinically relevant cell number (CD34+ cells and total leukocytes) is a limiting factor. To enable standardized cell banking and future in vitro expansion of adult stem/progenitor cells, elimination of serum, which inevitably differs from lot to lot and donor to donor, is highly desirable. Here, we demonstrate the feasibility of a xeno-free, chemically defined cryopreservation procedure for cord blood-derived cells over a period of 1 year. Cell recoveries with respect to retrieval of clinically relevant CD34+ cells, colony-forming units, and in vitro cultures of erythroid progenitor cells under standardized conditions were analyzed after 1 week or 1 year of cryopreservation and found to be very high and similar to the samples before freezing. The established xeno-free procedure is an important step toward using the full potential of adult stem cells from cord blood, enabling the elimination of serum-derived factors negatively influencing proliferation, differentiation, and survival of hematopoietic stem cells.

A multiple regression analysis on factors influencing haematopoietic progenitor cell collection for autologous transplantation

Autologous hematopoietic stem cell (HSC) transplantation today is the standard treatment for a wide variety of haematological and oncological diseases. HSC are collected from peripheral blood by leukapheresis (HPC-A) following chemotherapy and/or growth factor-mediated mobilization. The ideal HPC-A collection allows to reach the CD34(+) target dose through a single, tailored leukapheresis. The aim of this paper was to find out which collection parameter might play a key role in obtaining a CD34 dose >4×10(6)/kg with a reduced number of leukapheresis. To address this issue, a multivariate logistic regression was carried out on several operational and laboratory parameters from 943 HPC-A collections performed in 600 hematological and oncological patients. We observed a CD34(+) cells collection efficiency (CE) >50% when patient's pre-apheresis total WBC count was lower than 12.5×10(6)/mL. At the same time, the likelihood of reaching the CD34(+) cells target dose/kg increased from 6 to 3 times when the pre-apheresis WBC count ×10(6)/mL t was below 4.3 (OR=6.1; 2.6-14.1) and between 4.3 and 7 (OR=2.8; 1.4-5.7) respectively when compared to a pre-apheresis WBC count >36×10(6)/mL.

True volumetric method for flow cytometric enumeration of CD34 + stem cells and its agreement with a standard bead-based single-platform protocol

BACKGROUND AIMS

Stem cells are commonly enumerated with bead-based methods in blood and marrow progenitor cell transplantation centers. We compared the International Society of Hematotherapy and Graft Engineering (ISHAGE) bead-based method with a true volumetric one that obviates the use of fluorescent beads for enumeration.

METHODS

From 31 samples, including 15 peripheral blood samples and 16 leukapheresis products, CD34 (+) cells were enumerated with the single-platform bead-based ISHAGE method and a true volumetric method. After exclusion of two outliers, one from the peripheral blood group and the other from the leukapheresis group, the results were compared.

RESULTS

In the peripheral blood category, no significant difference was observed. However, a proportional systematic error was seen in the leukapheresis group. The systematic error was corrected in the leukapheresis group using a regression line equation. The 95% confidence interval of differences was [-5.83, 2.18] for the peripheral blood and [-38.40, 38.77] for the leukapheresis group after correction of the systematic error.

CONCLUSIONS

The true volumetric method is a simple and reliable approach that can be used instead of the more popular bead-based procedures.

Predictive factors for inadequate stem cell mobilization in Chinese patients with NHL and HL: 14-year experience of a single-center study

BACKGROUND

Factors affecting progenitor cell mobilization in patients with non-Hodgkin's lymphoma (NHL) and Hodgkin's lymphoma (HL) are incompletely understood. The aim of this retrospective study was to determine which factors are crucial for effective mobilization and collection of autologous peripheral blood stem cells (PBSC) prior to transplantation in Chinese patients.

PATIENTS AND METHODS

A total of 239 patients with lymphoma (198 NHL and 41 HL patients) underwent PBSC collection after mobilization with granulocyte-colony-stimulating factor (G-CSF) or G-CSF plus chemotherapy priming.

RESULTS

Patient characteristics at diagnosis and transplant, including low Eastern Cooperative Oncology Group score (P = 0.013), lack of extranodal invasion (P = 0.034), previously administered radiotherapy regimens (P = 0.040), treatment with platinum prior to mobilization (P = 0.042), previous chemotherapy regimens (P = 0.001) and cycles (P < 0.001), and chemotherapy regimens (P < 0.001) were statistically significant for successful mobilization in multivariate analysis. Premobilization factors, including previous radiotherapy (P = 0.009), previous chemotherapy regimens (P = 0.043) and cycles (P = 0.039), low platelet count prior to mobilization (P = 0.042), and lower CD34+ cells in peripheral blood (PB) (P = 0.050) or bone marrow (BM) (P = 0.007) were considered possibly predictive of poor mobilization. We found the patients who had chemosensitive lymphoma had worse progress-free survival (PFS) than the patients with initial treatment and high risks (P = 0.017).

CONCLUSION

Our analysis showed that high amounts of chemotherapy, radiotherapy, low platelet count, chemosensitive recurrent patients, combination chemotherapy plus G-CSF and low CD34+ cells in BM prior to mobilization could emerged as important predictive factors for mobilization failure in Chinese patients with NHL and HL.

Immunophenotyping of hematopoietic progenitor cells: Comparison between cord blood and adult mobilized blood grafts

AIM

To study the immunophenotype of hematopoietic progenitor cells from cord blood (CB) grafts (n = 39) in comparison with adult apheresis grafts (AG, n = 229) and pre-apheresis peripheral blood (PAPB) samples (n = 908) using flow cytometry analysis.

METHODS

First, we performed a qualitative analysis of CD34+ cell sub-populations in both CB and PAPB grafts using the standardized ISHAGE protocol and a wide panel of 20 monoclonal antibodies. Next, we studied some parameters, such as the age of mothers and the weight of newborns, which can influence the quality and the quantity of CD34+ cells from CB.

RESULTS

We found that the percentage of apoptotic cells was high in CB in comparison to PAPB (PAPB: 4.6% ± 2.6% vs CB: 53.4% ± 5.2%, P < 0.001). In CB, the weight of newborn and the age of the mother have the influence on CD34+ cells. The follow-up of Ag CD133 in the ISHAGE double platform protocol in association with CD45, CD34 and the 7'AAD shows an equal rate between the two cell populations CD133+CD45+CD34+ high and CD34+CD45+ high with a higher percentage. So, is the inclusion of Ac CD133 necessary in the present panel included in the ISHAGE method? Last part, we showed a significant presence of interferon γ in CB in comparison to PAPB, the annexin showing the high number of apoptotic cells in CB.

CONCLUSION

This study demonstrates that many different obstetric factors must be taken into account when processing and cryo-banking umbilical CB units for transplantation.

Evaluation of volume and total nucleated cell count as cord blood selection parameters: a receiver operating characteristic curve modeling approach

The objective of the study was to evaluate the current standard practice of using volume and total nucleated cell (TNC) count for the selection of cord blood (CB) units for cryopreservation and further transplantation. Data on 794 CB units whose CD34+ cell content was determined by flow cytometry were analyzed by using a receiver operating characteristic (ROC) curve model to validate the performance of volume and TNC count for the selection of CB units with grafting purposes. The TNC count was the best parameter to identify CB units having 2 × 10(6) or more CD34+ cells, with an area under the ROC curve of 0.828 (95% confidence interval, 0.800-0.856; P < .01) and an efficiency of 75.4%. Combination of parameters (TNC/mononuclear cells [MNCs], efficiency 74.7%; TNC/volume, efficiency 68.9%; and volume/MNCs, efficiency 68.3%) did not lead to improvement in CB selection. All CB units having a TNC count of 8 × 10(8) or more had the required CD34+ cell dose for patients weighing 10 kg or less.

Enumeration of viable CD34(+) cells by flow cytometry in blood, bone marrow and cord blood: results of a study of the novel BD™ stem cell enumeration kit

BACKGROUND AIMS

Enumeration of CD34(+) cells in leukocyte-rich cell suspensions is important for clinical decision-making in stem cell transplantation. Single-platform flow cytometry assays offer the significant advantages of speed and reproducibility, and have therefore become the gold standard in stem cell enumeration. The clinical community has recently defined the need for stem cell enumeration kits that incorporate viability dyes. The purpose of this study was to evaluate a novel assay, BD Biosciences' (BD) stem cell enumeration kit (SCE kit(‡)), in relation to Beckman Coulter's (BC) commercially available BC Stem-Kit™.

METHODS

Fresh/freeze-thawed samples from leukapheresis, bone marrow and cord blood, and fresh normal/mobilized blood, were analyzed with both assays (simultaneous detection of side/forward scatter and three fluorescence signals) on two flow cytometry platforms, BD FACSCanto II and BD FACSCalibur. Results. Results from both assays were highly congruent, with an overall r(2) ≥ 0.99 (all specimen types included), a linear correlation across all CD34(+) cell frequencies and concentrations, and an almost ideal steepness of the trend line.

CONCLUSIONS

Both assays functioned reliably. Being based on single-platform International Society of Hematotherapy and Graft Engineering (ISHAGE) guidelines and similar staining methods, both assays essentially come to identical results. For most specimen types, the viability of CD34(+) cells was equal to overall leukocyte viability. In summary, in the hands of an experienced technician, the BD™ SCE kit and the BC Stem-Kit are equivalent. The infrequent user might derive benefit from the fact that counting spheres are pre-pipetted into the Trucount tube for the SCE kit, making this assay less susceptible to pipetting inaccuracy.

Impact of viable CD45 cells infused on lymphocyte subset recovery after unrelated cord blood transplantation in children

We studied lymphocyte recovery in 88 children who consecutively underwent unrelated cord blood transplantation for malignant (n = 64) or nonmalignant (n = 24) diseases. All children but 3 received myeloablative conditioning regimens with pretransplant antithymocyte globulin. Median age was 5.6 years (0.1-18 years) and median follow-up was 40 months (10-136 months). The median dose of infused viable CD45(+) cells (vCD45) was 3.35 × 10(7)/kg with a ratio infused vCD45/collected total nucleated cell at 0.46. Immunologic endpoints were: time to achieve CD3(+) >500 and 1500/mm(3), CD4(+) >500/mm(3), CD8(+) >250/mm(3), CD19(+) >200/mm(3), natural killer >100/mm(3). These endpoints were analyzed through the use of cumulative curves for estimating incidence over time in the context of competing risks, and through Fine and Gray models to assess prognostic factors. The median time to reach these endpoints was 33, 97, 214, and 340 days for natural killer, B, CD8, and CD4 cells, respectively. In multivariate analysis, a high infused vCD45 cell dose improved CD3 (P = .014) and CD4 (P = .032) reconstitutions. A young recipient age also favored CD3 recovery (P = .013). With patients grouped according to vCD45 cell dose quartiles, the threshold for a better recovery was 3.35 × 10(7)/kg. Considering the ratio vCD45/TNC, this "immune recovery based" threshold corresponds to a higher cell dose than the minimum usually recommended dose for myelogenous engraftment. This may have important implication for UCB selection.

Endothelial progenitor cells in mixed cryoglobulinemia

OBJECTIVE

Endothelial progenitor cells (EPC) are a rare population of circulating cells involved in vascular homeostasis. Our aim was to analyze EPC in patients with mixed cryoglobulinemia (MC).

METHODS

EPC were evaluated by cytometry according to guidelines of the International Society for Hematotherapy and Graft Engineering in 17 patients with MC and 36 controls.

RESULTS

Numbers of EPC were significantly increased in MC compared to controls and correlated with cryocrit, but not with clinical manifestations of the disease.

CONCLUSION

The high number of EPC might indicate an intact vascular repair ability. Alternatively, EPC might be defective in homing ability and their increase may represent the attempt to restore vascular integrity.

Consistency of the initial cell acquisition procedure is critical to the standardization of CD34+ cell enumeration by flow cytometry: results of a pairwise analysis of umbilical cord blood units and cryopreserved aliquots

BACKGROUND

The CD34+ cell content is a predictive factor for engraftment and survival after umbilical cord blood (UCB) transplantation. The high variability in the CD34 assay results in different recommended cell doses for infusion across transplant centers and also limits the clinical utility of the CD34+ cell counts provided by cord blood banks (CBBs). This bi-institutional study was intended to understand the sources of this variability.

STUDY DESIGN AND METHODS

The level of CD34 agreement between the University of Minnesota (UM) and the Madrid CBB (MCBB) was evaluated on 50 UCB units before and after cryopreservation. Two cryopreserved vials per unit were thawed and processed at both laboratories. Dual-platform ISHAGE-based flow cytometry was used for CD34 enumeration.

RESULTS

Postthaw nucleated cell recoveries were similar. However, whereas CD34+ cell enumeration before freezing was 0.35 +/- 0.22 percent, the results after thawing were 0.98 +/- 0.65 and 0.57 +/- 0.39 percent at UM and MCBB, respectively. Bland-Altman plots analysis ruled out the interchangeability of MCBB and UM CD34 values. Differences in the initial cell acquisition settings accounted for most of the CD34 discrepancy, which was no longer present after normalization of the forward scatter threshold for cell acquisition.

CONCLUSIONS

The standardization of CD34+ cell enumeration by flow cytometry is strongly reliant on a consistent initial cell acquisition procedure. The interlaboratory variation can be minimized by using frozen cell aliquots as reference samples. Both requisites should be considered for CD34 testing and UCB unit selection by regulatory institutions involved with cord blood banking and transplantation.

Assessment of cord blood hematopoietic cell parameters before and after cryopreservation

BACKGROUND

The testing of cord blood (CB) progenitor and stem cell units for transplantation suitability involves enumeration of total nucleated cells before freezing. CD34+ cell counts may also be a means of determining suitability. Studies have been conducted to evaluate how specific storage conditions influence cell counts.

STUDY DESIGN AND METHODS

CB units were processed by hydroxyethyl starch volume reduction. Cryopreserved-thawed samples were diluted 1:3 without washing. CD34+ cells were measured with three commercially available assay methods. In specific studies, apoptosis-indicating reagents were included. CB units were analyzed for nucleated cells, aldehyde dehydrogenase-containing cells, and progenitor colonies.

RESULTS

CD34+ cell levels and nucleated cells were retained during storage in test tubes at 1 to 6 degrees C for 3 days. Cryopreserved-thawed samples showed a reduction in CD34+ cells relative to prefreeze levels with the largest decrease with the Stem-Kit (Beckman Coulter) restricted gating procedure. Prefreeze samples contained minimal numbers of presumed apoptotic cells detected with 7-aminoactinomycin D or SYTO16, but after cryopreservation-thawing there was an increase. Nucleated cell levels determined with a hematology analyzer or flow cytometry were reduced after thawing. Cryopreservation-thawing reduced the percentage of CD34+ cells positive for the presence of aldehyde dehydrogenase and the number of progenitor colonies. These differences were significant.

CONCLUSION

These studies indicate that CD34+ cell counts were maintained when CB samples were stored at 1 to 6 degrees C in test tubes for 3 days. Cryopreservation-thawing resulted in changes in a number of parameters including the percentage of CD34+ cells that were aldehyde dehydrogenase(+) and the number of 7-aminoactinomycin D(+) cells and SYTO16(low) cells.

Comparative quantification of umbilical cord blood CD34+ and CD34+ bright cells using the ProCount™-BD and ISHAGE protocols

The total number of CD34+ cells is the most relevant clinical parameter when selecting human umbilical cord blood (HUCB) for transplantation. The objective of the present study was to compare the two most commonly used CD34+ cell quantification methods (ISHAGE protocol and ProCount - BD) and analyze the CD34+ bright cells whose 7-amino actinomycin D (7AAD) analysis suggests are apoptotic or dead cells. Twenty-six HUCB samples obtained at the Placental Blood Program of New York Blood Center were evaluated. The absolute numbers of CD34+ cells evaluated by the ISHAGE (with exclusion of 7AAD+ cells) and ProCount (with exclusion of CD34+ bright cells) were determined. Using the ISHAGE protocol we found 35.6 +/- 19.4 CD34+ cells/microL and with the ProCount method we found 36.6 +/- 23.2 CD34+ cells/microL. With the ProCount method, CD34+ bright cell counts were 9.3 +/- 8.2 cells/microL. CD34+ bright and regular cells were individually analyzed by the ISHAGE protocol. Only about 1.8% of the bright CD34+ cells are alive, whereas a small part (19.0%) is undergoing apoptosis and most of them (79.2%) are dead cells. Our study showed that the two methods produced similar results and that 7AAD is important to exclude CD34 bright cells. These results will be of value to assist in the correct counting of CD34+ cells and to choose the best HUCB unit for transplantation, i.e., the unit with the greatest number of potentially viable stem cells for the reconstitution of bone marrow. This increases the likelihood of success of the transplant and, therefore, the survival of the patient.

Multiple-laboratory comparison of in vitro assays utilized to characterize hematopoietic cells in cord blood

BACKGROUND

Understanding the variability in results obtained by multiple laboratories is important because cord blood units are distributed worldwide for transplantation.

STUDY DESIGN AND METHODS

Four exercises were conducted by multiple laboratories to assess assay variability on nucleated cell (NC), mononuclear cell (MNC) by hematology analyzers [HAs], and CD34+ cell (flow cytometry) measurements. Exercise 1 was an intralaboratory exercise in which the reproducibility of cell measurements was determined. Exercises 2 and 3 involved the shipment of identical processed cord blood samples. In Exercise 2, laboratory-specific methods were utilized. In Exercise 3, two commercial CD34+ cell methods (Stem-Kit and TruCOUNT) were used. In Exercise 4, CD34+ cell levels were determined on repetitive regating of identical list-mode files.

RESULTS

Intralaboratory reproducibility was highest for NC measurements and lowest for CD34+ cell measurements. In Exercise 2, all laboratories except one utilized HA with an impedance technology and determined comparable results for NC and MNC levels, whereas the other laboratory utilized a HA with an optical counting method. Substantial variation was observed on measuring CD34+ cells with ranges of 32 to 141, 32 to 66, and 25 to 116 CD34+ cells per microL for the three identical samples. In Exercise 3, on the use of one specific commercial assay, the ranges of CD34+ levels were 214 to 411 and 62 to 178 cells per microL for the two identical samples. Nearly all participating laboratories determined comparable CD34+ levels on the use of identical list-mode files.

CONCLUSION

These studies indicate that substantial variability in CD34+ cell levels were determined with flow cytometry. The variability in NC and MNC levels was minimal with HA methodology.

SCID-repopulating activity of human umbilical cord blood-derived hematopoietic stem and/or progenitor cells in a nonobese diabetic/Shi-SCID mice serial xenotransplantation model and immune cell activities in vitro: a comparative study of the filter method and the hydroxyethyl starch method

BACKGROUND

A novel filter system was developed for umbilical cord blood (UCB) volume reduction. The aim of this study was to compare the functions of cryopreserved UCB cells processed by the filter and by the hydroxyethyl starch (HES) sedimentation method from the aspect of the graft quality.

STUDY DESIGN AND METHODS

UCB specimens were divided into two portions, processed in parallel by the filter or HES, and then cryopreserved in the clinical setting. The thawed UCB specimens containing 1 x 10(5) CD34+ cells were injected into nonobese diabetic/Shi-SCID mice, and the engraftment capacity in primary and secondary transplants was assessed. The functions of natural killer (NK) cells and monocyte-derived dendritic cells (DCs) were also assayed in vitro.

RESULTS

The percentage of recovery of CD34+ cells by both methods was equivalent. In the marrow of the primary transplant recipients, the percentage of hCD45+ cells in the filter group and HES group was 58.2 +/- 31.6 and 46.5 +/- 28.4 percent, respectively (p = 0.016). The engraftment capacity and multilineage differentiation in the secondary transplantations were equal in both groups. The cytotoxic activity of the NK cells and phagocytosis activity of the DCs from both the groups were similar.

CONCLUSION

The filter yielded a desirable percentage of recovery of hematopoietic cells with engraftment ability in the clinical setting. Thus, it is considered that the filter system may be useful for UCB banking for cord blood transplantation.

ESHAP+fixed dose G-CSF as autologous peripheral blood stem cell mobilization regimen in patients with relapsed or refractory diffuse large cell and Hodgkin's lymphoma: a single institution result of 127 patients

From 1996 to November 2004, 131 consecutive patients with relapsed or refractory diffuse large cell lymphoma (DLCL) and Hodgkin's lymphoma (HD) received ESHAP as mobilization chemotherapy before autologous peripheral blood stem cell transplant (ASCT). Patients received fixed dose G-CSF 300 microg SC bid starting 24-36 h after finishing mobilizing ESHAP. In all, four patients failed mobilization and are excluded. Characteristics of 127 patients: 68 males: 59 females. DLCL 49: HD 78. Initial stage I:II:III:IV:unknown was 15:34:33:42:3. Median age at ASCT 26 years. Median prior chemotherapy cycles were six [<6 (17 patients), 6-8 (90 patients), >8 (20 patients)]. Median ESHAP cycle used as mobilizer was third. Patients required 1, 2, 3, 4 apheresis were 93:25:8:1. Median total CD34+ cells/kg collected were 6.9 x 10(6) (DLCL 5.17 x 10(6) and HD 7.6 x 10(6)), patients weighing < or = 70 kg (93 patients) 6.54 x 10(6) and >70 kg (34 patients) 7.44 x 10(6) (P = 0.59), one apheresis (93 patients) 8.6 x 10(6)/kg and >1 apheresis (34 patients) 4.5 x 10(6) (P = 0.001). We conclude that ESHAP and G-CSF 300 microg SC bid is an effective mobilizing regimen even in patients >70 kg and most patients require only 1-2 apheresis.

Flow cytometry for natural killer T cells: multi-parameter methods for multifunctional cells

Valpha24-Jalpha18 invariant natural killer T cells (iNKT) are an evolutionary conserved sub-lineage of T cells with effector-memory phenotype that often express an NK cell surface antigen CD161 and is characterized by reactivity to self-glycolipids and alpha-galactosylceramide (alphaGalCer) that are presented by monomorphic HLA class-I-like molecule CD1d. Upon antigen recognition, iNKT cells can rapidly produce multiple cytokines and chemokines and regulate development of Th-2 and Th-1 immune responses. Potential importance of iNKT cells has been demonstrated in several animal models of infection diseases, autoimmunity, and cancer. Multi-parameter flow cytometry has been the main tool to study human and murine iNKT cells. Analysis of human iNKT cells is particularly demanding since their frequency among peripheral blood T cells is relatively low ranging from less than 0.01% to 1%, with a mean of about 0.1%. Herein, we discuss flow cytometry applications that are utilized for iNKT cell identification and enumeration, subset characterization, detection of intracellular cytokines, quantitative analysis of multiple secreted molecules, cell-mediated cytotoxicity, and migration.

Monitoring dendritic cells in clinical practice using a new whole blood single-platform TruCOUNT assay

Dendritic cells (DC) from distinct DC subsets are essential contributors to normal human immune responses. Despite this, reliable assays that enable DC to be counted precisely have been slow to evolve. We have now developed a new single-platform flow cytometric assay based on TruCOUNT beads and the whole blood "Lyse/No-Wash" protocol that allows precise counting of the CD14(-) blood DC subsets: CD11c(+)CD16(-) DC, CD11c(+)CD16(+) DC, CD123(hi) DC, CD1c(+) DC and BDCA-3(+) DC. This assay requires 50 microl of whole blood; does not rely on a hematology blood analyser for the absolute DC counts; allows DC counting in EDTA samples 24 h after collection; and is suitable for cord blood and peripheral blood. The data is highly reproducible with intra-assay and inter-assay coefficients of variation less than 3% and 11%, respectively. This assay does not produce the DC-T lymphocyte conjugates that result in DC counting abnormalities in conventional gradient-density separation procedures. Using the TruCOUNT assay, we established that absolute blood DC counts reduce with age in healthy individuals. In preliminary studies, we found a significantly lower absolute blood CD11c(+)CD16(+) DC count in stage III/IV versus stage I/II breast carcinoma patients and a lower absolute blood CD123(hi) DC count in multiple myeloma patients, compared to age-matched controls. These data indicate that scientific progress in DC counting technology will lead to the global standardization of DC counting and allow clinically meaningful data to be obtained.

Quantitation of MHC tetramer-positive cells from whole blood: Evaluation of a single-platform, six-parameter flow cytometric method

BACKGROUND

Quantitation of antigen-specific T cells provides an insight into the development and dynamics of T-cell responses in tumor immunology and infectious diseases. Soluble major histocompatibility class I tetramers are widely used to monitor immune responses; however, variations due to handling and analysis are likely to confound comparisons between different experiments and laboratories.

METHODS

Whole blood from healthy donors was stained with HLA-A*0201/tetramers specific for an epitope of phosphoprotein 65, the immunodominant antigen in cytomegalovirus infection. With the help of Trucount tubes, a single-platform, four-color flow cytometric assay was established to obtain absolute counts of tetramer-positive cells. Various staining and gating strategies were evaluated.

RESULTS

The no-wash method was a quick and straightforward procedure for the quantitation of tetramer-positive events from whole blood. The level for background staining was low. This information about the intra-assay-related variation and the physiologic variation will allow validation and interpretation of data in future studies.

CONCLUSIONS

The method is highly reliable and can be standardized for multiple experiments. It is therefore suitable for the direct ex vivo analysis of antigen-specific T cells in a variety of clinical settings such as infectious, autoimmune, or neoplastic diseases and can be implemented as a tool for multicenter studies.