Flow cytometric enumeration of CD34+ hematopoietic stem and progenitor cells. European Working Group on Clinical Cell Analysis

Flow Cytometric Enumeration of Peripheral Blood CD34+ Cells Predicts Bone Marrow Pathology in Patients with Less Than 1% Blasts by Manual Count

Background and Aims

Significance of absolute number of CD34+ cells in the peripheral blood of patients with less than 1% myeloblasts by manual differential count is unknown and our aim is to study its relevance in clinical practice.

Methods

We studied 138 peripheral bloods flow cytometric analyses in patients with less than 1% myeloblasts by manual differential, when CD34+ events were present in the gate that encompassed lymphocytes, monocytes, stem cells, and blasts.

Results

The average absolute number of CD34+cells in the peripheral blood was 11 CD34+cells/µL ranging from less than 1 cell/µL to 147 cells/µL. The average absolute number of CD34+ cells in patients with an abnormal expansive process involving bone marrow (metastases, myelodysplasia, granulomas, marrow infections) or if bone marrow biopsy not performed, presumed expansive marrow process was 25 cells/µL, and in patients without an expansive marrow process (or presumed negative) was 4 cells/µL (P<0.00007). Cutoff 12 CD34+ cells/μL had 93% positive predictive value for bone marrow involvement by an expansive process and 78% negative predictive value.

Conclusion

Flow cytometric testing of the peripheral blood is extremely sensitive method for enumerating CD34+ cells and can detect fewer than one CD34+ cell/µL. The absolute number of CD34+ cells in the peripheral blood is a useful parameter in determining marrow involvement by an expansive process and may provide guidance with respect to the necessity for bone marrow biopsy.

Single-cell RNA sequencing of human non-hematopoietic bone marrow cells reveals a unique set of inter-species conserved biomarkers for native mesenchymal stromal cells

BACKGROUND

Native bone marrow (BM) mesenchymal stem/stromal cells (BM-MSCs) participate in generating and shaping the skeleton and BM throughout the lifespan. Moreover, BM-MSCs regulate hematopoiesis by contributing to the hematopoietic stem cell niche in providing critical cytokines, chemokines and extracellular matrix components. However, BM-MSCs contain a heterogeneous cell population that remains ill-defined. Although studies on the taxonomy of native BM-MSCs in mice have just started to emerge, the taxonomy of native human BM-MSCs remains unelucidated.

METHODS

By using single-cell RNA sequencing (scRNA-seq), we aimed to define a proper taxonomy for native human BM non-hematopoietic subsets including endothelial cells (ECs) and mural cells (MCs) but with a focal point on MSCs. To this end, transcriptomic scRNA-seq data were generated from 5 distinct BM donors and were analyzed together with other transcriptomic data and with computational biology analyses at different levels to identify, characterize and classify distinct native cell subsets with relevant biomarkers.

RESULTS

We could ascribe novel specific biomarkers to ECs, MCs and MSCs. Unlike ECs and MCs, MSCs exhibited an adipogenic transcriptomic pattern while co-expressing genes related to hematopoiesis support and multilineage commitment potential. Furthermore, by a comparative analysis of scRNA-seq of BM cells from humans and mice, we identified core genes conserved in both species. Notably, we identified MARCKS, CXCL12, PDGFRA, and LEPR together with adipogenic factors as archetypal biomarkers of native MSCs within BM. In addition, our data suggest some complex gene nodes regulating critical biological functions of native BM-MSCs together with a preferential commitment toward an adipocyte lineage.

CONCLUSIONS

Overall, our taxonomy for native BM non-hematopoietic compartment provides an explicit depiction of gene expression in human ECs, MCs and MSCs at single-cell resolution. This analysis helps enhance our understanding of the phenotype and the complexity of biological functions of native human BM-MSCs.

The flow cytometry myeloid progenitor count: A reproducible parameter for diagnosis and prognosis of myelodysplastic syndromes

BACKGROUND

The bone marrow blast count is central to the diagnosis and monitoring of myelodysplastic syndromes (MDS). It is an independent risk factor for worse prognosis whether based on the morphology blast count or the flow cytometry (FC) myeloid progenitor (MyP) count. It is a principal population in FC MDS analysis also because once defined; it provides significant contributions to the overall FC MDS score.

METHODS

We elected to investigate inter-analyst agreement for the most fundamental parameter of the FC MDS diagnostic score: the MyP count. A common gating strategy was agreed and used by seven cytometrists for blind analysis of 34 routine bone marrows sent for MDS work-up. Additionally, we compared the results with a computational approach.

RESULTS

Concordance was excellent: Intraclass correlation was 0.993 whether measuring %MyP of total cells or CD45+ cells, and no significant difference was observed between files from different centers or for samples with abnormal MyP phenotypes. Computational and manual results were similar. Applying the common strategy to individual laboratories' control cohorts produced similar MyP reference ranges across centers.

CONCLUSION

The FC MyP count offers a reliable diagnostic and prognostic measurement in MDS. The use of manual and computational approaches side by side may allow for optimizing both strategies. Considering its known prognostic power, the MyP count could be considered a useful and reliable addition to existing prognostic scoring systems.

Widely applicable, extended flow cytometric stem cell enumeration panel for quality control of advanced cellular products

The most widely used quality control assay for CD34 + hematopoietic stem cell product characterization is the protocol established by the International Society of Hematotherapy and Graft Engineering (ISHAGE). While this protocol is still the gold standard for stem cell enumeration and viability assessment, it does not include T cell enumeration, which is nowadays mandatory for assaying standard allogeneic grafts and various advanced therapy medicinal products (ATMPs). In accordance, we have developed and extensively validated a new approach for a more comprehensive characterization of hematopoietic cellular products using a pre-formulated dried antibody format panel. In addition to the counting beads, the typical markers CD45 fluorescein isothiocyanate (FITC) and CD34 phycoerythrin (PE), as well as the viability dye 7-amino actinomycin D (7-AAD), our novel pre-formulated panel also contains CD3 Pacific Blue (PB) and CD19 allophycocyanin (APC) in the same tube, thereby allowing a combined calculation of leucocytes, stem cells, T and B cells. Showing high linearity, sensitivity and accuracy, our approach is easy to implement and enables a more in-depth characterization of the cellular product under release testing conditions. In addition, the dried pre-formulated antibody approach increases assay reliability compared to the standard antibody panel.

Mild or Moderate COVID-19 during Pregnancy Does Not Affect the Content of CD34+ Hematopoietic Stem Cells in Umbilical Cord Blood of Newborns

The study included umbilical cord blood samples (n=64) intended for cryogenic storage of hematopoietic stem cells and obtained from patients with a history of mild and moderate forms of COVID-19 during pregnancy. The control group was composed of samples (n=746) obtained from healthy women in labor. A comparative analysis of the volume of cord blood collected, the total leukocyte count, the relative and absolute content of cells with the CD34⁺/CD45⁺ phenotype revealed no significant differences between the groups.

Determination of mononuclear cell count using peripheral smear and flow cytometry in peripheral blood stem cell products: A retrospective study from an Indian cancer center

BACKGROUND:

Mononuclear cells (MNCs) are considered equivalent to hematopoietic stem cells, and differential count using peripheral smear was routinely practiced to enumerate MNC. Flow cytometry plots used for CD34 enumeration assay can also be used in MNC enumeration as it counts more WBC events than manual methods. The aim was to determine the relationship and degree of agreement between peripheral smear and flow cytometry in MNC enumeration of peripheral blood stem cell (PBSC) products.

METHODS:

In 63 patients, 73 PBSC products were collected between January 2017 and September 2019. The differences in MNC count estimated by peripheral smear method and from flow cytometry plots used for CD34 enumeration were analyzed using Mann–Whitney test. Agreement between the two methods for MNC enumeration was determined by regression analysis. Receiver operating characteristic curve was performed to determine MNC threshold in peripheral blood and PBSC product for adequate mobilization and harvest.

RESULTS:

There was no difference in enumeration of median MNC count between peripheral smear and flow cytometry (52% vs. 59%, P = 0.185) in PBSC product. However, regression analysis indicated a constant and proportional difference between the methods with r = 0.52. Cumulative sum test for linearity showed deviation from linearity (P = 0.04). MNC counts in peripheral blood failed to achieve discrimination capacity in predicting adequate CD34+ yield/kg body weight in product.

CONCLUSION:

Peripheral smear estimated lower MNC counts than flow cytometry with weaker agreements between the two methods. Hence, MNC count derived from flow cytometry plot can substitute peripheral smear method for MNC dose calculations. MNC dose at 3.4 × 10⁸/kg consistently predicted >2 × 10⁶/kg CD34+ cells collected.

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.

Correlation between peripheral blood automated hematopoietic progenitor cell counts and flow cytometric CD34+ cell counts differs according to diagnosis in patients undergoing autologous peripheral blood stem cell transplantation

BACKGROUND

An automated hematopoietic progenitor cell count measurement in Sysmex XN analyzer (XN-HPC) has been developed to assist flow cytometry CD34⁺ cell count measurement, which requires technical expertise and a long turnaround time. Here, we evaluated the correlation between XN-HPC count and flow cytometric CD34⁺ cell count in pre-harvest peripheral blood (PB) samples from patients undergoing autologous peripheral blood stem cell (PBSC) transplantation according to diagnosis and investigated the possible cause of the decreased correlation in plasma cell neoplasm patients.

MATERIALS AND METHODS

We retrospectively included 399 patient data that had matched PB XN-HPC count and CD34⁺ cell count of PB and apheresis product from Samsung Medical Center (SMC) and the Hematopoietic Stem Cell (HSC) registry. We assessed the diagnostic accuracy and the potential cutoff values of XN-HPC count for predicting adequate PBSC collection.

RESULTS

The PB XN-HPC count was 1.6 and 1.3-fold higher than the CD34⁺ cell count in SMC (25.0 vs 15.9/μl) and the HSC registry (20.0 vs 15.2/μl), respectively. Overall the correlation between the PB XN-HPC and CD34⁺ cell count was moderate (SMC, r = 0.71; HSC registry, r = 0.66). A significant proportional and systemic bias with overestimation of XN-HPC count were noted in the plasma cell neoplasm patients in both SMC and the HSC registry. However, no significant difference in correlation was observed according to myeloma-related laboratory parameters in plasma cell neoplasm patients.

CONCLUSION

Our results suggest that XN-HPC count should be interpreted cautiously in cancer patients undergoing autologous PBSC transplantation, especially in those with plasma cell neoplasm.

Usefulness of hematopoietic progenitor cell monitoring to predict autologous peripheral blood stem cell harvest timing: A single-center retrospective study

INTRODUCTION

In autologous peripheral blood stem cell harvest (APBSCH), CD34-positive cells have been measured to assess the numbers of hematopoietic stem cells, but measurement requires specialized equipment. Recently, there was a report that peripheral blood hematopoietic progenitor cells (HPCs) are useful indicators of the presence of hematopoietic stem cells. We examined the usefulness of HPC monitoring to predict APBSCH timing.

METHODS

We retrospectively analyzed the relationship between HPC and collected CD34-positive cells in 84 consecutive patients who underwent APBSCH.

RESULTS

According to the receiver operating characteristics curve for the collection of ≥2 × 106 CD34-positive cells/kg, the HPC cut-off value on the day before collection was 21/μL, while that on the day of collection was 41/μL. No significant factors were found in the univariate analysis except for the HPC count on the day before collection (p < 0.001) and the day of collection (p < 0.001). According to the multivariate analysis, the HPC count on the day before collection (p < 0.001) and the day of collection (p < 0.001) were also factors that strongly influenced the quantity of CD34-positive cells collected.

CONCLUSION

Our results suggest that the HPC count on not only the day of collection but also the day before collection is a good indicator for appropriate APBSCH timing.

Network mapping of primary CD34+ cells by Ampliseq based whole transcriptome targeted resequencing identifies unexplored differentiation regulatory relationships

With the exception of a few master transcription factors, regulators of neutrophil maturation are poorly annotated in the intermediate phenotypes between the granulocyte-macrophage progenitor (GMP) and the mature neutrophil phenotype. Additional challenges in identifying gene expression regulators in differentiation pathways relate to challenges wherein starting cell populations are heterogeneous in lineage potential and development, are spread across various states of quiescence, as well as sample quality and input limitations. These factors contribute to data variability make it difficult to draw simple regulatory inferences. In response we have applied a multi-omics approach using primary blood progenitor cells primed for homogeneous proliferation and granulocyte differentiation states which combines whole transcriptome resequencing (Ampliseq RNA) supported by droplet digital PCR (ddPCR) validation and mass spectrometry-based proteomics in a hypothesis-generation study of neutrophil differentiation pathways. Primary CD34+ cells isolated from human cord blood were first precultured in non-lineage driving medium to achieve an active, proliferating phenotype from which a neutrophil primed progenitor was isolated and cultured in neutrophil lineage supportive medium. Samples were then taken at 24-hour intervals over 9 days and analysed by Ampliseq RNA and mass spectrometry. The Ampliseq dataset depth, breadth and quality allowed for several unexplored transcriptional regulators and ncRNAs to be identified using a combinatorial approach of hierarchical clustering, enriched transcription factor binding motifs, and network mapping. Network mapping in particular increased comprehension of neutrophil differentiation regulatory relationships by implicating ARNT, NHLH1, PLAG1, and 6 non-coding RNAs associated with PU.1 regulation as cell-engineering targets with the potential to increase total neutrophil culture output. Overall, this study develops and demonstrates an effective new hypothesis generation methodology for transcriptome profiling during differentiation, thereby enabling identification of novel gene targets for editing interventions.

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.

Peripheral Blood Stem Cell Harvest HPC Count Is an Effective Surrogate Marker for CD34+ Cell Count in Allogeneic Stem Cell Transplant Setting

OBJECTIVE: We assessed the predictive potential of XN-HPC for CD34+ cell count as obtained through Sysmex automated hematology analyzers (XN-1000). METHODS: This study was conducted at the National Institute of Blood Diseases and Bone Marrow Transplantation in 84 donors between December 2012 and December 2017 in the first phase and later validated in 112 donors between December 2017 and December 2018. Sysmex XN-1000 and BD FACS Calibur estimated XN-HPC and CD34+ cells of peripheral blood apheresis product, respectively. Spearman's correlation was assessed between XN-HPC and CD34+ cell count followed by receiver operating characteristic curve calculation to determine the XN-HPC cutoff for a CD34+ count of ≥2 million cells/kg of recipient's body weight RESULTS: There is a moderately positive correlation (P value = .003) between XN-HPC and CD34+ count. Receiver operating characteristic curve analyses demonstrated that a cutoff value for XN-HPC of ≥1·845×10⁶cells/kg of recipient's body weight has a specificity and sensitivity of 100% and 78·2%, respectively, for predicting the CD34+ count of ≥2 million cells/kg of recipient's body weight. This cutoff value of XN-HPC was prospectively validated in 112 donors. The positive predictive value was found to be 100%, while negative predictive value was 17%. CONCLUSION: XN-HPC has a highly promising potential to serve as a cost-effective and time-saving surrogate for CD34+ cell count.

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.

Allogeneic transplantation of peripheral blood stem cell grafts results in a massive decrease of primitive hematopoietic progenitor frequencies in reconstituted bone marrows

The success of allogeneic hematopoietic stem cell transplantation (alloSCT) is indicated by the reconstitution of the peripheral blood system of patients after alloSCT and the engraftment of hematopoietic stem and progenitor cells (HSPCs) into their bone marrow (BM). The number of CD34⁺ cells is commonly used as surrogate for the content of hematopoietic stem cells in the grafts. During the last decade, several antigens (including CD133, CD45RA, CD38, and CD10) were identified allowing discrimination of different HSPC subpopulations within the human CD34⁺ cell compartment. Although such studies increased our understanding of early human hematopoiesis tremendously, hardly any study dissected the CD34⁺ compartment in the alloSCT setting. Consequently, we comprehensively analyzed the CD34⁺ compartment in G-CSF-stimulated peripheral blood stem cell grafts of allogeneic donors, in BM samples of the respective recipients 4 weeks after alloSCT, and in BM samples of healthy donors. We demonstrate that alloSCT is associated with a dramatic shift from primitive to more mature HSPC types. Upon investigating whether the composition of engrafted CD34⁺ cells has any impact on the incidence and severity of graft-versus-host disease, we did not find any correlation. However, more detailed analyses of the CD34⁺ compartment may elucidate associations with other transplantation-related complications.

Assessment of haematopoietic progenitor cell counting with the Sysmex® XN-1000 to guide timing of apheresis of peripheral blood stem cells

BACKGROUND

Successful peripheral blood stem cell (PBSC) collection depends on optimal timing of apheresis, as usually determined by flow cytometry CD34-positive (⁺) cell count in peripheral blood (PB). Since this method is costly and labour-intensive, we evaluated the use of the Hematopoietic Progenitor Cell count programme on a Sysmex^® XN haematologic analyser (XN-HPC) as a rapid and inexpensive alternative for predicting CD34⁺ cell count in PB samples.

MATERIALS AND METHODS

Haematopoietic progenitor cell and CD34⁺ cell counts were compared using 273 PB samples collected from 78 healthy donors and 72 patients who underwent PBSC transplantation. We assessed the effectiveness of the XN-HPC in safely predicting pre-harvest CD34⁺ counts. The most efficient cut-off values of XNHPC were identified. We also evaluated the imprecision (coefficient of variation, CV) and functional sensitivity.

RESULTS

Imprecision of the XN-HPC count was <6.3% on daily measurement of three levels of quality control material. Functional sensitivity was 8.9×10⁶/L. A cut-off value of ≥62×10⁶/L XN-HPC for multiple myeloma (MM) patients and ≥30×10⁶/L for all other subjects had both 100% specificity and 100% positive predictive value for identifying samples with CD34⁺ cells ≥20×10⁶/L. An XN-HPC threshold of <13×10⁶/L identified preharvest CD34⁺ cell count <10×10⁶/L with 100% sensitivity and 100% negative predictive value.

DISCUSSION

The XN-HPC is a fast, easy and inexpensive test that can safely improve apheresis workflow thus possibly replacing other more expensive CD34 counts currently performed and promoting optimal timing of PBSC collection.

Flow cytometric enumeration of CD34+ hematopoietic stem cells: A comparison between single- versus dual-platform methodology using the International Society of Hematotherapy and Graft Engineering protocol

BACKGROUND

Flow cytometric enumeration of CD34+ hematopoietic stem cells (HSC) is the reference point for undertaking apheresis and evaluation of adequacy for peripheral blood stem cell (PBSC) engraftment.

AIMS

To determine whether single platform correlates with dual platform methods in CD34+ enumeration using ISHAGE protocol.

METHODS

Retrospective analysis of CD34 Enumeration assays on both peripheral blood and PBSC product samples using Beckman Coulter FC500 Flow Cytometer. The t test and correlation study was used to study the difference between single and dual platform methods in CD34+ enumeration.

RESULTS

We present our data on 152 samples comprising 41 peripheral blood samples collected before apheresis procedure and 111 samples collected from PBSC product. We observed strong positive correlation between single and dual platform methods for CD34+ counts in peripheral blood sample (r = 0.92; P < 0.001) and PBSC product sample (r = 0.85; P < 0.001).

CONCLUSION

In our study, both single versus dual platform had similar results in CD34+ cell counts. The single platform provides rapid results with ease of procedure. Errors with dual platforms are relatively common with respect to denominator. We recommend to use mean of total leukocyte count from two different hematology analyzer to minimize variation in dual platform.

Comparison of Volumetric and Bead-Based Counting of CD34 Cells by Single-Platform Flow Cytometry

Background

Over 2,000 people a year in the United Kingdom need a bone marrow or blood stem cell transplant. It is important to accurately quantify the hematopoietic stem cells to predict whether the transplant will be successful in replenishing the immune system. However, they are present at low frequency, which complicates accurate quantification. The current gold standard method is single‐platform flow cytometry using internal reference counting beads to determine the concentration of CD34 cells. However, volumetric flow cytometers have the ability to measure the acquisition volume, which removes the need for reference beads for calculation of cell concentrations.

Method

In this study, we compared both methods for calculating CD34 cell concentrations in volumetric cytometers, using either the volume reading or the number of reference beads for calculation. In addition, the uncertainty of measurement for each method was estimated.

Results

The results show that both methods have similar uncertainties of measurement. Regression analysis showed low to no statistical difference in CD34 cell concentrations obtained with each method.

Conclusions

Overall, this study suggests that the volumetric method is a valid approach but that the adoption of this technology may be hindered without some form of external calibration of volume readings to increase confidence in the measurement. © 2019 The Authors. Cytometry Part B: Clinical Cytometry published by Wiley Periodicals, Inc. on behalf of International Clinical Cytometry Society.

The value of the post-thaw CD34+ count with and without DMSO removal in the setting of autologous stem cell transplantation

BACKGROUND

CD34+ cell count correlates with engraftment potency after autologous stem cell transplantation. Assessment of CD34+ mainly occurs after apheresis and before cryopreservation with dimethyl sulfoxide (DMSO). The influence of postthaw CD34+ cell numbers over time to engraftment is not well studied, and determination of postthaw CD34+ cell counts is challenging for a variety of reasons. The aim of this retrospective study was to systematically assess the value of postthaw CD34+ cell counts in autologous grafts with and without DMSO removal.

STUDY DESIGN AND METHODS

Between January 2008 and December 2015, 236 adult patients underwent a total of 292 autologous stem cell transplantations. Median age at transplantation was 56 years, and the main indication was multiple myeloma (60%). DMSO removal was done in 96 grafts (33%), either by centrifugation or by Sepax method.

RESULTS

Patients receiving grafts containing DMSO showed a significantly faster platelet (p = 0.02) and RBC (p = 0.001) engraftment. DMSO removal was not associated with fewer infusion-related adverse events. We observed a good correlation between CD34+ cell count after apheresis and CD34+ cell count after thawing/washing (r = 0.931). Ninety grafts (31%) showed a significant loss of viable CD34+ cells, which translated into a delayed engraftment.

CONCLUSION

DMSO removal was associated with delayed platelet and RBC engraftment without preventing adverse events. CD34+ cell enumeration after thawing remains difficult to perform, but grafts showing higher cell loss during cryopreservation and thawing are associated with slower engraftment. Prospective studies on the role of DMSO removal and postthaw CD34+ enumeration using defined protocols are needed.

Mobilization of hematopoietic progenitor cells for autologous transportation: consensus recommendations

Selected patients with certain hematological malignancies and solid tumors have the potential to achieve long-term survival with autologous hematopoietic progenitor cell transplant. The collection of these cells in peripheral blood avoids multiple bone marrow aspirations, results in faster engraftment and allows treatment of patients with infection, fibrosis, or bone marrow hypocellularity. However, for the procedure to be successful, it is essential to mobilize a sufficient number of progenitor cells from the bone marrow into the blood circulation. Therefore, a group of Brazilian experts met in order to develop recommendations for mobilization strategies adapted to the reality of the Brazilian national health system, which could help minimize the risk of failure, reduce toxicity and improve the allocation of financial resources.

Single Versus Dual Platform Analysis for Hematopoietic Stem Cell Enumeration Using ISHAGE Protocol

Hematopoietic stem cell transplantation is curative therapy in benign and malignant diseases. Adequate stem cell dose is one of the most important marker of engraftment. Several methods have been developed to enumerate CD34+ cells. We present our data on 147 samples analysis. There was a clear linear correlation between two methods. Both methods were effective. Both single vs dual platform analysis yield similar results. Single platform analysis is easier to perform. In terms of cost reduction dual platform analysis is better.

Multi-color immune-phenotyping of CD34 subsets reveals unexpected differences between various stem cell sources

Flow cytometric routine CD34 analysis enumerates hematopoietic stem and progenitor cells irrespective of their subpopulations although this might predict engraftment dynamics and immune reconstitution. We established a multi-color CD34 assay containing CD133, CD45RA, CD10, CD38 and CD33. We examined PBSC, donor bone marrow (BMd) and BM of patients 1 year after allografting (BM1y) regarding their CD34 subset composition, which differed significantly amongst those materials: the early CD45RA(-)CD133(+)CD38(low) subpopulations were significantly more frequent in PBSC than in BMd, and very low in BM1y. Vice versa, clearly more committed CD34 stages prevailed in BM, particularly in BM1y where the proportion of multi-lymphoid and CD38(++) B-lymphoid precursors was highest (mean 59%). CD33 was expressed at different intensity on CD45RA(±)CD133(±) subsets allowing discrimination of earlier from more committed myeloid precursors. Compared with conventional CD34(+) cell enumeration, the presented multi-color phenotyping is a qualitative approach defining different CD34 subtypes in any CD34 source. Its potential impact to predict engraftment kinetics and immune reconstitution has to be evaluated in future studies.

Fifteen years of external quality assessment in leukemia/lymphoma immunophenotyping in The Netherlands and Belgium: A way forward

In 1985, external quality assurance was initiated in the Netherlands to reduce the between-laboratory variability of leukemia/lymphoma immunophenotyping and to improve diagnostic conclusions. This program consisted of regular distributions of test samples followed by biannual plenary participant meetings in which results were presented and discussed. A scoring system was developed in which the quality of results was rated by systematically reviewing the pre-analytical, analytical, and post-analytical assay stages using three scores, i.e., correct (A), minor fault (B), and major fault (C). Here, we report on 90 consecutive samples distributed to 40-61 participating laboratories between 1998 and 2012. Most samples contained >20% aberrant cells, mainly selected from mature lymphoid malignancies (B or T cell) and acute leukemias (myeloid or lymphoblastic). In 2002, minimally required monoclonal antibody (mAb) panels were introduced, whilst methodological guidelines for all three assay stages were implemented. Retrospectively, we divided the study into subsequent periods of 4 ("initial"), 4 ("learning"), and 7 years ("consolidation") to detect "learning effects." Uni- and multivariate models showed that analytical performance declined since 2002, but that post-analytical performance improved during the entire period. These results emphasized the need to improve technical aspects of the assay, and reflected improved interpretational skills of the participants. A strong effect of participant affiliation in all three assay stages was observed: laboratories in academic and large peripheral hospitals performed significantly better than those in small hospitals. © 2015 International Clinical Cytometry Society.

Improvement of plateletpheresis via technical modification on the MCS+

BACKGROUND

With the advantage of easy operation and high reliability, Haemonetics multicomponent collection system (MCS+) is widely used as a blood cell separator in clinical application.

OBJECTIVES

The aim of this study was to evaluate the effect of technical parameter modification as utilised on the MCS+ to improve the quality of platelet yielded as well as donor comfort.

METHODS

After informed consent, a total of 118 donors, well matched for baseline parameters, were included in the study from December 2012 to April 2013. Sixty-one donors underwent single-dose plateletpheresis (SDP), and the other 57 donors underwent double-dose plateletpheresis (DDP) before and after technical modification on the MCS+, respectively, according to the manufacturer's instructions. The procedures were evaluated, focusing on whole blood processed (WBP), processing time (PT) and number of cycles were measured, as well as the quality of products.

RESULTS

No severe adverse reaction was found during donation. WBP, PT and number of cycles after modification were all reduced significantly in both SDP and DDP groups (P < 0·01). In addition, 80·51 % (95 in 118) of the total post-modification products were qualified, presenting with high quality. Besides, the comfort of donors was also improved probably because of the reduced PT.

CONCLUSION

Adjustment of the relevant technical parameters on MCS+ could produce a beneficial effect on the procedure measures and ensure a high-quality platelet production.

The plasma levels of soluble HLA-G molecules correlate directly with CD34+ cell concentration and HLA-G 14bp insertion/insertion polymorphism in cord blood donors

BACKGROUND

Cord blood provides haematopoietic stem cells for allogeneic transplantation and, thanks to the naivety of its immune system, has several advantages over other sources of stem cells. In the transplantation setting, the presence of immunosuppressive human leucocyte antigen (HLA)-G molecules has been advocated to prevent both rejection and Graft-versus-Host disease. HLA-G is physiologically expressed throughout pregnancy and is contained in cord blood at birth. Moreover, it has recently been reported that not only cord blood mesenchymal cells, but also CD34+ cell progenies produce soluble HLA-G (sHLA-G). We tried to identify the largest producer of sHLA-G among 85 healthy cord blood donors at Pavia Cord Blood Bank, correlating the sHLA-G concentration with the HLA-G 14bp insertion/deletion (INS/DEL) genotype and CD34+ cell concentration.

MATERIALS AND METHODS

We measured sHLA-G levels in 36 cord blood plasma stored at -20 °C for 2 months and 49 cord blood plasma stored at -196 °C for 4-6 years, by enzyme-linked immunosorbent assay. All cord blood donors were genotyped for the HLA-G 14bp INS/DEL polymorphism by polymerase chain reaction. For each cord blood unit, we measured the cell concentration by flow cytometry.

RESULTS

We did not find differences in sHLA-G levels between cord blood plasma aliquots stored for 4-6 years at -196 °C and cord blood plasma aliquots stored for 2 months at -20 °C. We observed a higher sHLA-G concentration in cord blood plasma donors who carried the HLA-G 14bp INS/INS genotype and had higher CD34+ cell concentrations (P=0.006).

DISCUSSION

This is the first report showing that the best cord blood stem cell donor is also the best sHLA-G producer, particularly if genetically characterized by the HLA-G 14bp INS/INS genotype. If the therapeutic role of sHLA-G molecules were to be finally established in the transplantation setting, our data suggest that cord blood plasma donors can provide a safe source of allogeneic sHLA-G immunosuppressive molecules ready for transfusion.

Risk factors for unsuccessful peripheral blood stem cell harvesting using granulocyte-colony stimulating factor mobilization in patients with multiple myeloma

The aim of this study was to determine factors that influence unsuccessful peripheral blood stem cell (PBSC) harvesting in patients with multiple myeloma (MM). Retrospective data of 186 MM patients who received G-CSF as mobilization were analyzed. Patients with successful harvest were compared with those who failed (using 2 definitions of failure <2 and <4 CD34 cells×10(6)/mm(3)). The groups were compared regarding age, gender, body weight, baseline platelet count, receipt of radiotherapy, number of prior chemotherapy regimens, PBSC count before collection, processed and collected volume, collect replace, number of sessions and final number of PBSC collected. By multivariate analysis, a baseline platelet count <161,000 cells/mm(3) was associated with PBSC harvest lower than 2×10(6)/kg, and age >58 years was related to PBSC harvest lower than 4×10(6)/kg CD34 cells/kg. Patients with these parameters should not receive mobilization protocols with G-CSF alone. Alternative protocols should be tested in this high risk harvest failure population.

CD34⁺ cell content in unrelated allogeneic peripheral blood stem cell grafts transported internationally. Does the inter-laboratory variability affect comparability of graft quality data?

BACKGROUND

Increasing numbers of unrelated hematopoietic stem cell grafts are transported internationally and evaluated concurrently in different laboratories. The graft quality assessment using the CD34(+) enumeration could be influenced by inter-laboratory variability.

METHODS

We retrospectively analyzed the content of CD34(+) cells in 154 consecutive collections being performed in different transplant centers during two periods (2003-2004, 2007-2010). All samples were tested twice in our own and partner laboratories. CD34(+) percentage and absolute number were compared.

RESULTS

The percentage and the total CD34(+) content correlated well in both observed periods (CD34(+)%: r=0.899 and r=0.922; CD34(+)×10(8)/kg: r=0.966 and r=0.880; p<0.0001). Median CD34(+) percentages obtained in our centre in comparison with other laboratories were 0.54% vs. 0.46% in 2003-2004 and 0.69% vs. 0.70% in 2007-2010 period. The degree of laboratory compliance was affected by the laboratory identity. CD34(+) percentage reported by one laboratory and CD34(+)×10(8)/kg reported by three from twelve laboratories lacked statistically significant correlation with our own data.

CONCLUSIONS

The study documented that results of CD34(+) cell dose assessment of the same grafts reported by different transplant centers are comparable. The graft quality data and the CD34(+) enumeration possess a limited level of inter-laboratory variability.

Shared resource laboratories: impact of new design criteria to consolidate flow cytometry diagnostic service

INTRODUCTION

The Shared Resource Laboratory (SRL) model recently described for research activities would also appear to be highly suitable for diagnostic services. Using modern SRL design criteria and benchmarks, the aim of our study was to verify whether the consolidation of a diagnostic cytofluorimetric activity could improve the overall service.

METHODS

Outcome indicators such as impact on analytical quality, clinical satisfaction, team work involvement, and economic performance were evaluated in the planning and setting up of a new central laboratory. Comparison with preconsolidation status allowed us to investigate possible indicators of improvement.

RESULTS

A total of 30 140 cytofluorimetric analyses performed before and after consolidation at the Central Laboratory in Pievesestina in north-central Italy were evaluated. The overall score of the clinical satisfaction questionnaire (range, between 1 and 5) increased from 4.3 to 4.9. Full-time equivalent (FTE) operators were reduced from 9 to 4.5 and cytofluorimeters from 6 to 2; economic indicator analyses showed a 17.75% reduction in unitary test costs.

CONCLUSIONS

The adoption of new benchmarks and design criteria increased the quality of cytofluorimetric analysis, thus improving specialized diagnostic services and promoting the shared resource clinical laboratory.

Food supplement 20070721-GX may increase CD34+ stem cells and telomerase activity

Few rejuvenation and antiaging markers are used to evaluate food supplements. We measured three markers in peripheral blood to evaluate the antiaging effects of a food supplement containing placental extract. Samples were evaluated for CD34⁺ cells, insulin-like growth factor 1 (IGF1), and telomerase activity, which are all markers related to aging. To control the quality of this food supplement, five active components were monitored. In total, we examined 44 individuals who took the food supplement from 1.2 months to 23 months; the average number of CD34⁺ cells was almost 6-fold higher in the experimental group compared with the control group. Food supplement intake did not change serum IGF1 levels significantly. Finally, the average telomerase activity was 30% higher in the subjects taking this food supplement. In summary, our results suggest that the placental extract in the food supplement might contribute to rejuvenation and antiaging.

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.

ISHAGE protocol: are we doing it correctly?

BACKGROUND

Flow cytometric CD34(+) stem cell enumeration is routinely performed to optimize timing of peripheral blood stem cell collections and assess engraftment capability of the apheresis product. While a number of different flow methodologies have been described, the highly standardized ISHAGE protocol is currently the most widely employed, with 204/255 (81%) international participants in the UK NEQAS CD34(+) stem cell enumeration program indicating their use of this method. Recently, two laboratories were identified as persistent poor performers, a fact attributed to incorrect ISHAGE protocol usage/setup. This prompted UK NEQAS to question whether other laboratories were making similar errors and, if so, how this might affect individual EQA performance.

METHODS AND RESULTS

In send out 0801, where two stabilized samples were issued, the EQA center surveyed 255 participants with flow analysis data and subsequent results collected. One hundred and ninety-six laboratories returned results with 103 returning dot plots. Eighty-three out of one hundred and three stated that they used the ISHAGE protocol gating strategy but 43% (36/83) were incorrectly set-up. Analysis of the data showed those incorrectly using single platform ISHAGE gating strategy were twice as likely to fail an EQA exercise compared to those using the protocol correctly. This failure rate increased two fold when incorrect ISHAGE protocol was used in a dual platform setting.

CONCLUSION

This study suggests a widespread fundamental lack of understanding of the ISHAGE protocol and the need to deploy it correctly, potentially having significant clinical implications and highlights the need to monitor participants rigorously in their deployment of the ISHAGE protocol. It is hoped that once these findings have been disseminated, performance can be improved.

Application of flow cytometry in pediatric hematology-oncology

Applications of flow cytometry in pediatric cancers have expanded substantially in recent years. In acute leukemias, the commonest childhood cancer, flow cytometry can now define complex antigenic profiles that are associated with specific cytogenetic/molecular defects and can also directly identify BCR-ABL fusion protein. Flow cytometry based scoring system has been described for diagnosis of myelodysplastic syndromes. In solid tumors, flow cytometry was previously used mainly to determine DNA content for prognosis; however, recent studies in children with neuroblastoma and Ewing sarcoma have identified its diagnostic utility. In this review, we will discuss the current and future applications of flow cytometry in pediatric hematology-oncology.

CD34+ Cell Enumeration by Flow Cytometry: A Comparison of Systems and Methodologies

Context.—An increasing number of medical centers can collect bone marrow, peripheral blood, or umbilical cord stem cells. Pathology laboratories should accommodate this trend, but investment in additional equipment may be impractical.

Objectives.—To compare CD34+ cell counting results by using 2 widely available flow cytometry systems, with and without the use of a separate hematology analyzer (ie, single-platform versus dual-platform methodologies).

Design.—Whole blood and peripheral blood stem cell (PBSC) samples were analyzed from 13 healthy allogeneic PBSC donors and 46 autologous PBSC donors with various malignancies. The Cytomics FC500 (Beckman Coulter, Fullerton, California) was compared with the FACSCalibur (BD Biosciences, San Jose, California). Dual-platform CD34+ cell counting incorporated data from a KX-21 hematology analyzer (Sysmex, Kobe, Japan).

Results.—Subtle differences in CD34+ cell counting between 2 systems and 2 methods did not achieve statistical significance.

Conclusion.—Different systems and methods for CD34+ cell enumeration, properly validated, can support care for patients undergoing transplants and provide meaningful data for multicenter studies or meta-analyses.

A randomized study of transendocardial injection of autologous bone marrow mononuclear cells and cell function analysis in ischemic heart failure (FOCUS-HF)

BACKGROUND

Autologous bone marrow mononuclear cell (ABMMNC) therapy has shown promise in patients with heart failure (HF). Cell function analysis may be important in interpreting trial results.

METHODS

In this prospective study, we evaluated the safety and efficacy of the transendocardial delivery of ABMMNCs in no-option patients with chronic HF. Efficacy was assessed by maximal myocardial oxygen consumption, single photon emission computed tomography, 2-dimensional echocardiography, and quality-of-life assessment (Minnesota Living with Heart Failure and Short Form 36). We also characterized patients' bone marrow cells by flow cytometry, colony-forming unit, and proliferative assays.

RESULTS

Cell-treated (n = 20) and control patients (n = 10) were similar at baseline. The procedure was safe; adverse events were similar in both groups. Canadian Cardiovascular Society angina score improved significantly (P = .001) in cell-treated patients, but function was not affected. Quality-of-life scores improved significantly at 6 months (P = .009 Minnesota Living with Heart Failure and P = .002 physical component of Short Form 36) over baseline in cell-treated but not control patients. Single photon emission computed tomography data suggested a trend toward improved perfusion in cell-treated patients. The proportion of fixed defects significantly increased in control (P = .02) but not in treated patients (P = .16). Function of patients' bone marrow mononuclear cells was severely impaired. Stratifying cell results by age showed that younger patients (≤60 years) had significantly more mesenchymal progenitor cells (colony-forming unit fibroblasts) than patients >60 years (20.16 ± 14.6 vs 10.92 ± 7.8, P = .04). Furthermore, cell-treated younger patients had significantly improved maximal myocardial oxygen consumption (15 ± 5.8, 18.6 ± 2.7, and 17 ± 3.7 mL/kg per minute at baseline, 3 months, and 6 months, respectively) compared with similarly aged control patients (14.3 ± 2.5, 13.7 ± 3.7, and 14.6 ± 4.7 mL/kg per minute, P = .04).

CONCLUSIONS

ABMMNC therapy is safe and improves symptoms, quality of life, and possibly perfusion in patients with chronic HF.