Establishment and optimization of a flow cytometric method for evaluation of viability of CD34+ cells after cryopreservation and comparison with trypan blue exclusion staining

Pros and Cons of Cryopreserving Allogeneic Stem Cell Products

The COVID-19 pandemic has precipitously changed the practice of transplanting fresh allografts. The safety measures adopted during the pandemic prompted the near-universal graft cryopreservation. However, the influence of cryopreserving allogeneic grafts on long-term transplant outcomes has emerged only in the most recent literature. In this review, the basic principles of cell cryopreservation are revised and the effects of cryopreservation on the different graft components are carefully reexamined. Finally, a literature revision on studies comparing transplant outcomes in patients receiving cryopreserved and fresh grafts is illustrated.

Flow Cytometric Characterization of Hematopoietic Stem and Progenitor Cell Subpopulations in Autologous Peripheral Blood Stem Cell Preparations after Cryopreservation

Introduction

Autologous stem cell transplantation is a successful routine procedure with only a small number of non-engraftment cases, although the time to hematopoietic recovery may vary considerably across patients. While CD34 has been the decisive marker for enumerating hematopoietic stem and progenitor cells (HSPCs) for more than 30 years, the impact of CD34-positive cellular subpopulations in autologous HSPC grafts on hematopoietic reconstitution remains unclear.

Methods

The two-color ISHAGE protocol represents the current gold standard for CD34+ cell enumeration but includes only the number of viable CD45+/CD34+ cells relative to the body weight of the recipient. We adapted a multicolor flow cytometry marker panel for advanced characterization of CD34 subpopulations in retained samples of autologous peripheral blood stem cell products (n = 49), which had been cryostored for a wide range from 4 to 15 years. The flow cytometric analysis included CD10, CD34, CD38, CD45, CD45RA, CD133, and viability staining with 7AAD. The findings were correlated with clinical engraftment data, including reconstitution of leukocytes, neutrophils, and platelets after transplantation (TPL).

Results

We demonstrated that the identification of autologous HSPC subpopulations by flow cytometry after cryopreservation is feasible. Regarding the distribution of HSPC subpopulations, a markedly different pattern was observed in comparison to previously published data obtained using fresh autologous material. Our data revealed the largest ratio of lympho-myeloid progenitors (LMPPs) after freezing and thawing, followed by multipotent progenitors and erythroid-myeloid progenitors. A high ratio of LMPPs, representing an immature stage of differentiation, correlated significantly with early neutrophilic granulocyte and leukocyte engraftment (p = 0.025 and p = 0.003). Conversely, a large ratio of differentiated cells correlated with late engraftment of neutrophilic granulocytes (p = 0.024). Overall, successful engraftment was documented for all patients.

Conclusion

We established an advanced flow cytometry panel to assess the differentiation ability of cryostored autologous peripheral blood stem cell grafts and correlated it with timely hematopoietic reconstitution. This approach represents a novel and comprehensive way to identify hematopoietic stem and progenitor subpopulations. It is a feasible way to indicate the engraftment capacity of stem cell products.

Processing Adipose Tissue Samples in a GMP Environment Standardizes the Use of SVF in Cell Therapy Treatments: Data on 302 Patients

Stromal vascular fraction (SVF) cells, together with adipose-derived mesenchymal stem cells, are becoming the tool of choice for many clinical applications. Currently, nearly 200 clinical trials are running worldwide to prove the efficacy of this cell type in treating many diseases and pathological conditions. To reach the goals of cell therapies and produce ATMPs as drugs for regenerative medicine, it is necessary to properly standardize GMP processes and, thus, collection methods, transportation strategies, extraction protocols, and characterization procedures, without forgetting that all the tissues of the human body are characterized by a wide inter-individual variability which is genetically determined and acquired during life. Here, we compare 302 samples processed under GMP rules to exclude the influence of the operator and of the anatomical site of collection. The influence of variability in the ages and genders of patients, along with laboratory parameters such as total cell number, cell viability, stem cell number, and other stromal vascular fraction cell subpopulations, has been compared. The results show that when the laboratory protocol is standardized, the variability of quantifiable cell parameters is widely statistically non-significant, meaning that we can take a further step toward standardized advanced cell therapy products.

Overview of current adipose-derived stem cell (ADSCs) processing involved in therapeutic advancements: flow chart and regulation updates before and after COVID-19

Adipose-derived stem cells (ADSCs) have raised big interest in therapeutic applications in regenerative medicine and appear to fulfill the criteria for a successful cell therapy. Their low immunogenicity and their ability to self-renew, to differentiate into different tissue-specific progenitors, to migrate into damaged sites, and to act through autocrine and paracrine pathways have been altogether testified as the main mechanisms whereby cell repair and regeneration occur. The absence of standardization protocols in cell management within laboratories or facilities added to the new technologies improved at patient's bedside and the discrepancies in cell outcomes and engraftment increase the limitations on their widespread use by balancing their real benefit versus the patient safety and security. Also, comparisons across pooled patients are particularly difficult in the fact that multiple medical devices are used and there is absence of harmonized assessment assays despite meeting regulations agencies and efficient GMP protocols. Moreover, the emergence of the COVID-19 breakdown added to the complexity of implementing standardization. Cell- and tissue-based therapies are completely dependent on the biological manifestations and parameters associated to and induced by this virus where the scope is still unknown. The initial flow chart identified for stem cell therapies should be reformulated and updated to overcome patient infection and avoid significant variability, thus enabling more patient safety and therapeutic efficiency. The aim of this work is to highlight the major guidelines and differences in ADSC processing meeting the current good manufacturing practices (cGMP) and the cellular therapy-related policies. Specific insights on standardization of ADSCs proceeding at different check points are also presented as a setup for the cord blood and bone marrow.

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.

Evaluation of the BD Stem Cell Enumeration Kit on the BD FACSCanto II flow cytometer using bd facscanto clinical and bd facsdiva software

INTRODUCTION

CD34+ hematopoietic stem cell (HSC) enumeration by cell flow cytometry is routinely used in clinical laboratories for monitoring of HSC mobilization into peripheral blood and assessment of the quality of HSC products. The modified ISHAGE protocol is the most often used procedure for determination of CD34+ cells using flow cytometry. The aim of this study was to evaluate BD Enumeration stem cell kit on flow cytometer BD facscanto II, using facscanto clinical and facsdiva softwares.

METHODS

Validation study included determination of within-run and between-run precision, trueness (bias), comparison of the test results analyzed on facscanto clinical and facsdiva softwares, assessment of linearity, specimen stability, and carryover.

RESULTS

For between-run precision, coefficients of variation (CVs) were all <10%, except for low control level on facsdiva software. CVs for within-run precision were <10%, except for high absolute count of CD34+ cells on facsdiva software. Comparison of data showed no statistically significant differences between facscanto clinical and facsdiva software (Spearman's rank correlation coefficients were .993 for % of CD34+ cells and 0.983 for absolute count of CD34+ cells). In linearity study, bias for all dilutions was < 20%, and carryover assessment cannot be considered significant on both softwares. There was a statistically significant difference (P = .044) in absolute count of CD34+ cells after 24 hours of storage, when using facscanto clinical software.

CONCLUSION

BD Stem Cell Enumeration Kit can be used in routine laboratory work on BD FACSCanto II instrument, whereas facscanto clinical and facsdiva software were used for acquisition and data analysis.

Overcoming the deceptively low viability of CD45+ cells in thawed cord blood unit segments

BACKGROUND AND OBJECTIVES

There is no standard methodology for post-thaw sample preparation for viability analysis of umbilical cord blood units (CBU). A common challenge faced by CB bank is for their product to meet the post-thaw cell viability threshold for CD45⁺ cells set at 40% by NetCord-FACT. The objective of this work was to improve the post-thaw staining method to maximize CD45⁺ cell viability so that clinically valuable samples meet the NetCord-FACT threshold criteria for CD45⁺ and CD34⁺ cell viabilities.

MATERIALS AND METHODS

Samples of CBU buffy coats and CBU segments were thawed and taken for staining. Various parameters were evaluated on CD45⁺ and CD34⁺ cell viability as measured by 7-actinomycin D (7-AAD) staining.

RESULTS

The results revealed that initiating the staining at 20 min post-thaw instead of 30, shortening the red cell lysis treatment, or performing lysis on ice and removing this step all together, all improved the viability of CD45⁺ cells. Using CBU segments, it was shown that the most effective approach in increasing the viability of CD45⁺ cells was the complete omission of red cell lysis step. However, removal of the lysis step can create technical artefacts during flow cytometry acquisition that results in an underestimation of the viability of CD34⁺ cells. This can be avoided and CD34⁺ cell viability restored with additional thresholding on CD45 signal.

CONCLUSION

CB CD45⁺ cells are sensitive to red cell lysis treatment post-thaw; omission of this step provides the best viability and ultimately better reflects the quality of cells used for transplantation.

Role of TGF-β1/miR-382-5p/SOD2 axis in the induction of oxidative stress in CD34+ cells from primary myelofibrosis

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by an excessive production of pro-inflammatory cytokines resulting in chronic inflammation and genomic instability. Besides the driver mutations in JAK2, MPL, and CALR genes, the deregulation of miRNA expression may also contribute to the pathogenesis of PMF. To this end, we recently reported the upregulation of miR-382-5p in PMF CD34+ cells. In order to unveil the mechanistic details of the role of miR-382-5p in pathogenesis of PMF, we performed gene expression profiling of CD34+ cells overexpressing miR-382-5p. Among the downregulated genes, we identified superoxide dismutase 2 (SOD2), which is a predicted target of miR-382-5p. Subsequently, we confirmed miR-382-5p/SOD2 interaction by luciferase assay and we showed that miR-382-5p overexpression in CD34+ cells causes the decrease in SOD2 activity leading to reactive oxygen species (ROS) accumulation and oxidative DNA damage. In addition, our data indicate that inhibition of miR-382-5p in PMF CD34+ cells restores SOD2 function, induces ROS disposal, and reduces DNA oxidation. Since the pro-inflammatory cytokine transforming growth factor-β1 (TGF-β1) is a key player in PMF pathogenesis, we further investigated the effect of TGF-β1 on ROS and miR-382-5p levels. Our data showed that TGF-β1 treatment enhances miR-382-5p expression and reduces SOD2 activity leading to ROS accumulation. Finally, inhibition of TGF-β1 signaling in PMF CD34+ cells by galunisertib significantly reduced miR-382-5p expression and ROS accumulation and restored SOD2 activity. As a whole, this study reports that TGF-β1/miR-382-5p/SOD2 axis deregulation in PMF cells is linked to ROS overproduction that may contribute to enhanced oxidative stress and inflammation. Our results suggest that galunisertib may represent an effective drug reducing abnormal oxidative stress induced by TGF-β1 in PMF patients. DATABASE LINKING: GEO: https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE103464.

A non-aggressive, highly efficient, enzymatic method for dissociation of human brain-tumors and brain-tissues to viable single-cells

Background

Conducting research on the molecular biology, immunology, and physiology of brain tumors (BTs) and primary brain tissues requires the use of viably dissociated single cells. Inadequate methods for tissue dissociation generate considerable loss in the quantity of single cells produced and in the produced cells’ viability. Improper dissociation may also demote the quality of data attained in functional and molecular assays due to the presence of large quantities cellular debris containing immune-activatory danger associated molecular patterns, and due to the increased quantities of degraded proteins and RNA.

Results

Over 40 resected BTs and non-tumorous brain tissue samples were dissociated into single cells by mechanical dissociation or by mechanical and enzymatic dissociation. The quality of dissociation was compared for all frequently used dissociation enzymes (collagenase, DNase, hyaluronidase, papain, dispase) and for neutral protease (NP) from Clostridium histolyticum. Single-cell-dissociated cell mixtures were evaluated for cellular viability and for the cell-mixture dissociation quality. Dissociation quality was graded by the quantity of subcellular debris, non-dissociated cell clumps, and DNA released from dead cells. Of all enzymes or enzyme combinations examined, NP (an enzyme previously not evaluated on brain tissues) produced dissociated cell mixtures with the highest mean cellular viability: 93 % in gliomas, 85 % in brain metastases, and 89 % in non-tumorous brain tissue. NP also produced cell mixtures with significantly less cellular debris than other enzymes tested. Dissociation using NP was non-aggressive over time—no changes in cell viability or dissociation quality were found when comparing 2-h dissociation at 37 °C to overnight dissociation at ambient temperature.

Conclusions

The use of NP allows for the most effective dissociation of viable single cells from human BTs or brain tissue. Its non-aggressive dissociative capacity may enable ambient-temperature shipping of tumor pieces in multi-center clinical trials, meanwhile being dissociated. As clinical grade NP is commercially available it can be easily integrated into cell-therapy clinical trials in neuro-oncology. The high quality viable cells produced may enable investigators to conduct more consistent research by avoiding the experimental artifacts associated with the presence dead cells or cellular debris.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-016-0262-y) contains supplementary material, which is available to authorized users.

Successful mobilization, intra-apheresis recruitment, and harvest of hematopoietic progenitor cells by addition of plerixafor and subsequent large-volume leukapheresis

BACKGROUND

In patients failing successful conventional mobilization of hematopoietic progenitor cells (HPC) plerixafor (Mozobil(®)) seems to be an alternative. We report a series of 14 patients with multiple myeloma or NHL successfully mobilized and harvested by plerixafor together with large-volume leukaphereses (LVL).

METHODS

In a first series (GI), 5 patients were mobilized with G-CSF and plerixafor. In the second series (GII), 9 patients were mobilized by chemotherapy, G-CSF, and plerixafor.

RESULTS

In GI and GII, addition of plerixafor led to a significant (p < 0.01) increase of leukocytes and CD34+ cells in peripheral blood (PB). In GII, the median number of CD34+ cells in PB before and after addition of plerixafor was significantly (p = 0.019) higher compared to GI (9 vs. 5 and 50 vs. 24 cells/μl, respectively). In GI and GII, a median number of three or one aphereses was performed. In GII, the median yield (6.7 × 10(6) CD34+ cells/kg) of the first apheresis and the median intra-apheresis recruitment of CD34+ cells were significantly (p < 0.05) higher compared to GI (2.94 × 10(6) CD34+ cells/kg). All patients transplanted, 5 in GI and 8 in GII, exhibited successful engraftment.

CONCLUSIONS

Plerixafor and G-CSF mobilization or the addition of plerixafor during non-optimal chemotherapy and G-CSF mobilization together with LVL enabled, independent of leukocyte count and even without detectable CD34+ cells before addition of plerixafor, sufficient harvest of HPC numbers for transplantation. Addition of plerixafor during chemotherapy and G-CSF mobilization led to an increased intra-apheresis recruitment and a significantly higher yield of CD34+ cells compared to plerixafor and G-CSF steady-state mobilized patients.

Apparent mtDNA sequence heterogeneity in single human blood CD34+ cells is markedly affected by storage and transport

Single CD34(+) cells from adult human peripheral blood show mtDNA sequence heterogeneity. In this study, we compared mtDNA sequence variation in single CD34(+) cells from peripheral blood (PB) mononuclear cells (MNCs) from the same donors but under different conditions of storage and transport: group I, MNCs from heparinized PB that inadvertently required six days to be transported to the testing laboratory; group II, MNCs which were isolated from PB within a day of phlebotomy and frozen prior to transportation and storage. We observed more cell death for MNCs of group I than group II. Concordantly, group I CD34(+) cells had a very low potential for hematopoietic colony formation in vitro compared with group II cells. CD34(+) cells of group II showed an unexpectedly higher level of mtDNA sequence heterogeneity than was present in group I cells. These observations suggest that reduced mtDNA sequence heterogeneity in single CD34(+) cells of group I was likely due to elimination of cells harboring mutations. CD34(+) cells that survive stress ex vivo may be more enriched in quiescent primitive hematopoietic stem cells, with fewer mtDNA mutations than are present in committed progenitors. Technically, attention is required to conditions of preparation of human blood samples for single cell mtDNA analysis.

Clinical grade adult stem cell banking

There has been a great deal of scientific interest recently generated by the potential therapeutic applications of adult stem cells in human care but there are several challenges regarding quality and safety in clinical applications and a number of these challenges relate to the processing and banking of these cells ex-vivo. As the number of clinical trials and the variety of adult cells used in regenerative therapy increases, safety remains a primary concern. This has inspired many nations to formulate guidelines and standards for the quality of stem cell collection, processing, testing, banking, packaging and distribution. Clinically applicable cryopreservation and banking of adult stem cells offers unique opportunities to advance the potential uses and widespread implementation of these cells in clinical applications. Most current cryopreservation protocols include animal serum proteins and potentially toxic cryoprotectant additives (CPAs) that prevent direct use of these cells in human therapeutic applications. Long term cryopreservation of adult stem cells under good manufacturing conditions using animal product free solutions is critical to the widespread clinical implementation of ex-vivo adult stem cell therapies. Furthermore, to avoid any potential cryoprotectant related complications, reduced CPA concentrations and efficient post-thaw washing to remove CPA are also desirable. The present review focuses on the current strategies and important aspects of adult stem cell banking for clinical applications. These include current good manufacturing practices (cGMPs), animal protein free freezing solutions, cryoprotectants, freezing & thawing protocols, viability assays, packaging and distribution. The importance and benefits of banking clinical grade adult stem cells are also discussed.

Valproic acid triggers erythro/megakaryocyte lineage decision through induction of GFI1B and MLLT3 expression

Histone deacetylase inhibitors represent a family of targeted anticancer compounds that are widely used against hematological malignancies. So far little is known about their effects on normal myelopoiesis. Therefore, in order to investigate the effect of histone deacetylase inhibitors on the myeloid commitment of hematopoietic stem/progenitor cells, we treated CD34(+) cells with valproic acid (VPA). Our results demonstrate that VPA treatment induces H4 histone acetylation and hampers cell cycle progression in CD34(+) cells sustaining high levels of CD34 protein expression. In addition, our data show that VPA treatment promotes erythrocyte and megakaryocyte differentiation. In fact, we demonstrate that VPA treatment is able to induce the expression of growth factor-independent protein 1B (GFI1B) and of mixed-lineage leukemia translocated to chromosome 3 protein (MLLT3), which are crucial regulators of erythrocyte and megakaryocyte differentiation, and that the up-regulation of these genes is mediated by the histone hyperacetylation at their promoter sites. Finally, we show that GFI1B inhibition impairs erythroid and megakaryocyte differentiation induced by VPA, while MLLT3 silencing inhibits megakaryocyte commitment only. As a whole, our data suggest that VPA sustains the expression of stemness-related markers in hematopoietic stem/progenitor cells and is able to interfere with hematopoietic lineage commitment by enhancing erythrocyte and megakaryocyte differentiation and by inhibiting the granulocyte and mono-macrophage maturation.

Direct volumetric flow cytometric quantitation of CD34+ stem and progenitor cells

OBJECTIVES

In this study, we compared a classic single-platform (SP) method applying beads for enumeration of CD45+ or CD34+ cells with a new device allowing direct volumetric measurements of stem and progenitor cells.

BACKGROUND

Following apheresis and cyropreservation, the precise enumeration of CD34+ cells as key parameter of graft quality is mandatory for the clinical course after transplantation. Currently, flow cytometry with SP technique represents the 'gold standard' for such determinations.

METHODS/MATERIALS

Fresh samples, 14 from mobilised peripheral blood (PB), 9 from apheresis products (AP) and 13 samples from frozen-thawed (FT) haematopoietic progenitor cell grafts, were analysed for CD34+ cells, CD45+ cells, and in frozen-thawed samples for viability by a bead-based flow cytometric method and in parallel by a direct, volumetric flow cytometric method.

RESULTS

Comparison of CD34+ analyses revealed a significant correlation (P < 0·01) for each material between both techniques with r = 0·95 (PB), r = 0·933 (AP) and r = 0·929 (FT). Also, for analysis of CD45+ cells µL(-1) , the measured numbers evaluated with the different techniques did not significantly differ for all three materials analysed. In frozen-thawed samples, the analysis of viability was comparable for both techniques.

CONCLUSIONS

The results of this study demonstrate that a direct volumetric analysis of CD34+ cells µL(-1) or CD45+ cells µL(-1) is feasible. This technique represents a simple and economical approach for standardisation of progenitor and stem cell analyses.

Biomimetic postcapillary expansions for enhancing rare blood cell separation on a microfluidic chip

Blood cells naturally auto-segregate in postcapillary venules, with the erythrocytes (red blood cells, RBCs) aggregating near the axis of flow and the nucleated cells (NCs)--which include leukocytes, progenitor cells and, in cancer patients, circulating tumor cells--marginating toward the vessel wall. We have used this principle to design a microfluidic device that extracts nucleated cells (NCs) from whole blood. Fabricated using polydimethylsiloxane (PDMS) soft lithography, the biomimetic cell extraction device consists of rectangular microchannels that are 20-400 μm wide, 11 μm deep and up to 2 cm long. The key design feature is the use of repeated expansions/contractions of triangular geometry mimicking postcapillary venules, which enhance margination and optimize the extraction. The device operates on unprocessed whole blood and is able to extract 94 ± 4.5% of NCs with 45.75 ± 2.5-fold enrichment in concentration at a rate of 5 nl s(-1). The device eliminates the need to preprocess blood via centrifugation or RBC lysis, and is ready to be implemented as the initial stage of lab-on-a-chip devices that require enriched nucleated cells. The potential downstream applications are numerous, encompassing all preclinical and clinical assays that operate on enriched NC populations and include on-chip flow cytometry (A. Y. Fu et al., Anal. Chem., 2002, 74, 2451-2457; A. Y. Fu et al., Nat. Biotechnol., 1999, 17, 1109-1111), genetic analyses (M. M. Wang et al., Nat. Biotechnol., 2005, 23, 83-87; L. C. Waters et al., Anal. Chem., 1998, 70, 5172-5176) and circulating tumor cell extraction (S. Nagrath et al., Nature, 2007, 450, 1235-1241; S. L. Stott et al., Proc. Natl. Acad. Sci. U. S. A., 2010, 18392-18397; H. K. Lin et al., Clin. Cancer Res., 2010, 16, 5011-5018).

Quality of long-term cryopreserved umbilical cord blood units for hematopoietic cell transplantation

The aim of this study was to evaluate the quality of long-term cryopreserved umbilical cord blood (CB) units for hematopoietic cell transplantation (HCT). The recovery of the number of total nucleated cell (TNC), hematopoietic progenitor cells (HPCs; CD34+ cells, colony-forming units-granulocyte/macrophages [CFU-GMs]), and the percentage of viable cells, CD34+ CD38- cells, and CD34+ CXCR4+ cells of CB units cryopreserved for 10 years for HCT were examined. Eighteen CB units cryopreserved for 10 years (as the study group) and for 1 month (as the control group), respectively, were analyzed. The recovery rate of TNC, CD34+ cells and CFU-GMs were 88.72 ± 16.40, 68.39 ± 18.37 and 42.28 ± 38.16% for the study group and 80.17 ± 14.46, 72.67 ± 20.38 and 49.61 ± 36.39% for the control group (p = 0.106, p = 0.513 and p = 0.559, respectively). There were no significant differences in the recovery rate of TNC, CD34+ cells and CFU-GMs between the study group and the control group. The mean basal percentage of viable cells, CD34+ CD38- cells, and CD34+ CXCR4+ cells after thawing were 83.69 ± 9.45, 9.11 ± 4.13 and 81.65 ± 10.82% for the study group. These results indicate that long-term cryopreservation does not negatively affect the quality of CB units for HCT.

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.

P-selectin-coated microtube for the purification of CD45+ hematopoietic cells directly from human peripheral blood

Purified samples of CD45+ hematopoietic cells are a prerequisite for chimerism analysis in transplantation therapies, and are useful in various research and clinical settings such as functional and molecular analysis or disease diagnosis. Recently, we have established a flow-based adhesion molecule-dependent process for the purification of these cells from human bone marrow. However, for practical purposes, it is desirable to apply this approach to process small volumes of human blood. CD45+ cell purities were >94% when PBMNCs and plasma depleted blood were perfused through P-selectin coated microtubes. However, P-selectin surface failed to capture CD45+ cells when fresh blood prior to washing was perfused. The process requires a pre-step of plasma removal which otherwise inhibits interactions of cell surface PSGL-1 with immobilized P-selectin due to the presence of soluble PSGL-1 in plasma. We conclude that P-selectin can be used in a compact flow device to isolate and purify CD45+ cells directly from human peripheral blood. The process is simple, rapid, cost effective and represents a physiologic approach to the capture and purification of CD45+ MNCs from peripheral blood.

Role of CD34 antigen in myeloid differentiation of human hematopoietic progenitor cells

CD34 is a transmembrane protein that is strongly expressed on hematopoietic stem/progenitor cells (HSCs); despite its importance as a marker of HSCs, its function is still poorly understood, although a role in cell adhesion has been demonstrated. To characterize the function of CD34 antigen on human HSCs, we examined, by both inhibition and overexpression, the role of CD34 in the regulation of HSC lineage differentiation. Our results demonstrate that CD34 silencing enhances HSC granulocyte and megakaryocyte differentiation and reduces erythroid maturation. In agreement with these results, the gene expression profile of these cells reveals the upregulation of genes involved in granulocyte and megakaryocyte differentiation and the downregulation of erythroid genes. Consistently, retroviral-mediated CD34 overexpression leads to a remarkable increase in erythroid progenitors and a dramatic decrease in granulocyte progenitors, as evaluated by clonogenic assay. Together, these data indicate that the CD34 molecule promotes the differentiation of CD34+ hematopoietic progenitors toward the erythroid lineage, which is achieved, at least in part, at the expense of granulocyte and megakaryocyte lineages.

Cryopreservation of cellular products in a closed-bag system with an incorporated dimethyl sulfoxide-resistant sterile filter outside of cleanroom facilities

BACKGROUND

Manipulations, for example, cryopreservation, of cellular therapeutics carried out in an open system must be performed in a class A environment with surrounding class B environment. To avoid cleanroom facilities, a new closed-bag system with an incorporated dimethyl sulfoxide-resistant sterile filter for cryopreservation of cellular products was evaluated at two different centers.

STUDY DESIGN AND METHODS

A total of 44 different products (22 buffy coats [BCs] and 22 leukapheresis [LK] products) were split and cryopreserved in parallel in cleanroom facilities (Method I) and with the closed system on the bench of a "normal" laboratory (Method II). Viability analyzed by 7-aminoactinomycin D staining and flow cytometric analysis and sterility of the products were analyzed.

RESULTS

Independent of the cellular source (BC or LK), the median viability of CD45+ cells decreased significantly (p < 0.01) during cryopreservation: namely, in BCs, -15.8 percent with both methods, and in LK products, -5.4 percent with Method I and -4.8 percent with Method II, respectively. CD3+ as well as CD14+ cells exhibited a similar pattern and were also found significantly (p < 0.01) diminished after thawing independent of the handling system. For CD19+ cells, the small decrease of viability was only for the BC group significant (p = 0.027) when the cells had been processed with Method I. No bacterial contamination was detected neither in fresh products nor in products after cryopreservation.

CONCLUSION

The closed system for cryopreservation of cellular products appears to be equivalent to cleanroom-based methods regarding cellular integrity and sterility when appropriate quality of sterile filters is assured.

Quality of umbilical cord blood CD34+ cells in a double-compartment freezing bag cryopreserved without a rate-controlled programmed freezer

The aim of this study was to evaluate how a simple method of cryopreservation influences the quality of CD34+ cells in umbilical cord blood (UCB). The cells were dispensed into a double-compartment freezing bag, cryopreserved at -85 degrees C without a rate-controlled programmed freezer, and stored in the liquid phase of nitrogen. The viability of the CD34+ cells before freezing and after thawing was assessed by flow cytometry with 7-aminoactinomycin D and by colony-forming assays. Twenty UCB units cryopreserved for a median of 92 days were analyzed. Mean CD34+ cell viabilities before freezing were 99.8% +/- 0.4% and after thawing were 99.5% +/- 0.8% in large chambers, 99.6% +/- 0.5% in small chambers, and 99.4% +/- 0.6% in sample tubes. The mean values from colony-forming assays of the viable CD34+ cells before freezing were 30.7 +/- 6.8 (colony-forming units-granulocyte-macrophage [CFU-GM] per 100 viable CD34+ cells) and 68.5 +/- 14.8 (total CFUs per 100 viable CD34+ cells). The CFU-GM and total CFU values after thawing were, respectively, 32.7 +/- 9.0 and 66.0 +/- 13.4 in large chambers, 32.4 +/- 8.1 and 64.5 +/- 16.1 in small chambers, and 30.9 +/- 5.4 and 64.7 +/- 12.4 in sample tubes. The results of the colony-forming assays before freezing and after thawing were not significantly different. Our findings overall indicated that our simple method for the cryopreservation of UCB cells without a rate-controlled programmed freezer does not impair the clonogenic capacity of UCB progenitor cells. This cryopreservation method could provide cellular products adequate for hematopoietic stem cell transplantation.