Flow cytometric measurement of apoptosis and necrosis in cryopreserved PBPC concentrates from patients with malignant diseases

Effects of cell concentration, time of fresh storage, and cryopreservation on peripheral blood stem cells: PBSC fresh storage and cryopreservation

INTRODUCTION

Peripheral blood stem cells are widely used in autologous or allogeneic transplantation. The quality of the product directly impacts clinical outcomes, and the cell quality and/or functionality may be influenced by the storage conditions as time, temperature, total nucleated cells (TNC) concentration and cryopreservation requirement.

OBJECTIVE

To verify the effects of time, cell concentration, and cryopreservation/thawing in the viability and functionality of stem cells for transplantation.

METHODS

We evaluated TNC, CD45⁺ viable cells, CD34⁺ viable cells, and cell viability and functionality of 11 samples. Measurements were performed immediately and 24 h, 48 h, 72 h, and 96 h after sample collection at high and low TNC concentrations. The same parameters were also evaluated after cryopreservation and thawing of the samples.

RESULT

Duration of storage and TNC concentration exhibited a negative effect on cell quality (CD45⁺ viable cells, CD34⁺ viable cells and functionality). Moreover, the association of these parameters increased the negative effect on graft quality. Cryopreservation and thawing also negatively affected the collected sample regarding viable CD34⁺ cells (recovery 66.2 %), viable CD45⁺ cells (recovery 56.8 %), and 7-AAD viability. No significant losses in viable CD45⁺/CD34⁺ cells and functionality were observed in the first 24 h in both TNC conditions.

CONCLUSION

These results emphasize the importance to consider carefully the storage conditions until transplantation, measuring TNC/μL until 24 h after collection (diluting the product when TNC > 300 × 10³/μL) and infusing fresh graft as soon as possible.

A Comparison of p53 Isoform Profiles and Apoptosis Induced by Camptothecin or a Herbal Khat Extract (Catha Edulis (Vahl) Forssk. ex Endl.) in Leukemic Cell Lines: Exploring Cellular Responses in Therapy Development

Simple Summary

This study aimed at exploring the modulations of p53 in cell toxicity induced by an extract of the herb khat, a natural stimulant used by millions of people. We previously reported that khat-extract induced cell death by affecting mitochondrial function and the receptor- and mitochondria-mediated cell death pathways, in leukemic cell lines and cells of the oral cavity, in vitro. We included the cancer therapeutic camptothecin, which induces apoptosis in various cancer cell lines. By studying modulations of p53 full-length protein and p53 β/γ isoforms following exposure to khat-extract and camptothecin, we wished to elucidate differences and similarities resulting from the treatments using MOLM-13 and MV-4-11 leukemic cell lines. Our results demonstrate that molecular effects of the cytotoxic treatments resulted in different p53 isoforms patterns and post-translational modifications. We suggest that analysis of p53 modulations could be useful in the search for new chemical probes and experimental cancer therapeutics.

Abstract

Khat (Catha edulis (Vahl) Forssk. ex Endl.) is habitually used as a natural stimulant by millions of people, but is associated with adverse effects on gastrointestinal, cardiovascular and central neural systems. At the cellular level khat toxicity involves p53 induction and cell cycle arrest, decreased mitochondrial function and activation of receptor- and mitochondria-mediated cell death pathways. In this study we have examined an extract of khat for induction of p53 post-translational modifications (PTMs) and the functional role of p53 in khat-mediated cell death. Khat was shown to induce phosphorylation and acetylation of p53 in both the khat-sensitive MOLM-13 and the khat-resistant MV-4-11 cell line, but accumulation of the full-length p53 isoform was only observed in the khat sensitive cell line. Small molecule inhibitors of p38 MAP kinase sensitized MV-4-11 cells for khat-treatment without concomitant stabilization of p53. Experiments using a p53 knock-down cell line and murine p53 knock-out bone marrow cells indicated that p53 was redundant in khat-mediated cell death in vitro. We suggest that analysis of isoform patterns and p53 PTMs are useful for elucidation of biological effects of complex plant extracts, and that p53 protein analysis is particularly useful in the search for new chemical probes and experimental cancer therapeutics.

Enhancement of Quercetin-Induced Apoptosis by Cotreatment with Autophagy Inhibitor Is Associated with Augmentation of BAK-Dependent Mitochondrial Pathway in Jurkat T Cells

A flavonoid antioxidant quercetin promotes dose-dependent activation of the ATM-CHK-p53 pathway, downregulation of antiapoptotic survivin, and upregulation of proapoptotic NOXA in human T cell acute lymphoblastic leukemia Jurkat clones (J/Neo and J/BCL-XL). However, the downregulation of antiapoptotic BAG3 and MCL-1 occurred in J/Neo cells but not in J/BCL-XL cells overexpressing BCL-XL. Additionally, several BCL-XL-sensitive intrinsic mitochondrial apoptotic events including apoptotic sub-G₁ cell accumulation, TUNEL-positive DNA fragmentation, BAK activation, mitochondrial membrane potential (Δψm) loss, caspase-9/caspase-8/caspase-3 activation, and PARP cleavage were induced only in J/Neo cells. Both cytosolic and mitochondrial ROS levels were elevated in quercetin-treated J/Neo cells; however, the ROS elevations were almost completely abrogated in J/BCL-XL cells, suggesting the ROS elevations were downstream of BCL-XL-sensitive mitochondrial damage and dysfunction. Wild-type A3, FADD-deficient I2.1, and caspase-8-deficient I9.2 Jurkat clones exhibited similar susceptibilities to the cytotoxicity of quercetin, excluding an involvement of extrinsic pathway in triggering the apoptosis. The autophagic events such as attenuation of AKT-mTOR pathway, formation of acridine orange-stainable acidic vesicular organelles, conversion of microtubule-associated protein 1 light chain 3-I (LC3-I) to LC3-II, and downregulation of p62/SQSTM1 level were detected in quercetin-treated J/Neo and J/BCL-XL cells, regardless of BCL-XL overexpression. Cotreatment with the autophagy inhibitor (3-methyladenine, LY294002, or chloroquine) resulted in a significant enhancement of quercetin-induced BAK activation and subsequently the mitochondrial damage-mediated apoptosis pathway by augmenting the downregulation of BAG3 and MCL-1 levels in J/Neo cells. These results demonstrated that quercetin induces intrinsic apoptosis and cytoprotective autophagy, and autophagy inhibition can potentiate BAK-dependent apoptotic activity of quercetin in Jurkat T cells.

Cryopreservation and thawing of hematopoietic stem cell CD34-induced apoptosis through caspase pathway activation: Key role of granulocytes

INTRODUCTION

Cell damage inescapably occurs during both the freezing and the thawing graft processes for autologous hematopoietic stem cell (HSC) transplantation. To estimate HSC injury, a quality control is performed including: (i) CD34⁺ quantification; (ii) percentage of CD34⁺ viability and (iii) evaluation of HSC functional ability to form colony forming unit-granulocyte macrophage (CFU-GM). Apoptosis involves complex pathways such as caspase enzymes. Here, we assess the extent of apoptosis that is caspase-dependent before and after cryoconservation of CD34⁺, using a Fluorescent Labeled Inhibitor of CAspases (FLICA).

METHODS

Caspase pathway activation status was evaluated in 46 patients (multiple myeloma [n = 24], lymphoma [n = 22]), by flow cytometry, using a 7-aminoactinomycin-D (7AAD)/FLICA staining test, in CD34⁺, CD3⁺, CD14⁺ and CD56⁺ cells. Viable 7AAD^-/FLICA⁺ cells were then correlated with various parameters.

RESULTS

We showed a significant caspase pathway activation, with 23% CD34⁺/7AAD^-/FLICA⁺ cells after thawing, compared with the 2% described in fresh CD34⁺ cells (P < 0.0001). Moreover, caspase pathway was significantly activated in thawing CD3⁺, CD56⁺ and CD14⁺ cells. We also report a significant correlation between the rate of CD34⁺/7AAD^-/FLICA⁺ cells and post-thawing granulocytes count (P = 0.042) and their potential to be differentiated into CFU-GM (P = 0.004).

DISCUSSION

Our results show substantial cell death, induced by the increase of caspase pathway activation, secondary to the thawing process, and across all study cell types. This observation may affect the immune response quality during recipient aplasia, without detecting a clinical impact. Moreover, caspase pathway activation through CD3⁺ and CD56⁺ subpopulations could modify the therapeutic result of donor lymphocytes infusion (DLI).

Effect of fraxetin on proliferation and apoptosis in breast cancer cells

The aim of the present study was to examine the effect of fraxetin on proliferation and apoptosis in the MCF-7 breast cancer cell line. Cell proliferation was measused using an MTT assay and 4′,6-diamidino-2-phenylindole (DAPI) staining was used to determine shrinkage and condensation. RT-PCR was used to examine the expression of factor-associated suicide (Fas) and Fas ligand (FasL) mRNA, and western blot analysis was used to examine Bax and Bcl-2 protein. MTT showed that the proliferation of MCF-7 cells was significantly inhibited by fraxetin in a dose-dependent manner. Fraxetin also induced significant morphological changes of MCF-7 cells, suggestive of apoptosis, whereas DAPI staining showed that fraxetin caused cell shrinkage and chromatin condensation. RT-PCR showed that the expression of Fas and FasL mRNA was upregulated by fraxetin and the western blot analysis revealed that Bax was upregulated and Bcl-2 was downregulated. In conclusion, fraxetin can inhibit the proliferation of MCF-7 cells, induce apoptosis, upregulate Fas, FasL and Bax, and downregulate Bcl-2 to induce apoptosis. These results support the potential therapeutic role for fraxetin in breast cancer.

Cryopreservation: Evolution of Molecular Based Strategies

Cryopreservation (CP) is an enabling process providing for on-demand access to biological material (cells and tissues) which serve as a starting, intermediate or even final product. While a critical tool, CP protocols, approaches and technologies have evolved little over the last several decades. A lack of conversion of discoveries from the CP sciences into mainstream utilization has resulted in a bottleneck in technological progression in areas such as stem cell research and cell therapy. While the adoption has been slow, discoveries including molecular control and buffering of cell stress response to CP as well as the development of new devices for improved sample freezing and thawing are providing for improved CP from both the processing and sample quality perspectives. Numerous studies have described the impact, mechanisms and points of control of cryopreservation-induced delayed-onset cell death (CIDOCD). In an effort to limit CIDOCD, efforts have focused on CP agent and freeze media formulation to provide a solution path and have yielded improvements in survival over traditional approaches. Importantly, each of these areas, new technologies and cell stress modulation, both individually and in combination, are now providing a new foundation to accelerate new research, technology and product development for which CP serves as an integral component. This chapter provides an overview of the molecular stress responses of cells to cryopreservation, the impact of the hypothermic and cell death continuums and the targeted modulation of common and/or cell specific responses to CP in providing a path to improving cell quality.

Biobanking: The Future of Cell Preservation Strategies

With established techniques cryopreservation is often viewed as an "old school" discipline yet modern cryopreservation is undergoing another scientific and technology development growth phase. In this regard, today's cryopreservation processes and cryopreserved products are found at the forefront of research in the areas of discovery science, stem cell research, diagnostic development and personalized medicine. As the utilization of cryopreserved cells continues to increase, the demands placed on the biobanking industry are increasing and evolving at an accelerated rate. No longer are samples providing for high immediate post-thaw viability adequate. Researchers are now requiring samples where not only is there high cell recovery but that the product recovered is physiologically and biochemically identical to its pre-freeze state at the genominic, proteomic, structural, functional and reproductive levels. Given this, biobanks are now facing the challenge of adapting strategies and protocols to address these needs moving forward. Recent studies have shown that the control and direction of the molecular response of cells to cryopreservation significantly impacts final outcome. This chapter provides an overview of the molecular stress responses of cells to cryopreservation, the impact of the apoptotic and necrotic cell death continuum and how studies focused on the targeted modulation of common and/or cell specific responses to freezing temperatures provide a path to improving sample quality and utility. This line of investigation has provided a new direction and molecular-based foundation guiding new research, technology development and procedures. As the use of and the knowledge base surrounding cryopreservation continues to expand, this path will continue to provide for improvements in overall efficacy and outcome.

Targeting cryopreservation-induced cell death: a review

Despite marked developments in the field of cryopreservation of cells and tissues for research and therapeutic applications, post-thaw cell death remains a significant drawback faced by cryobiologists. Post cryopreservation apoptosis and necrosis are normally observed within 6 to 24 h after post-thaw culture. As a result, massive loss of cell viability and cellular function occur due to cryopreservation. However, in this new generation of cryopreservation science, scientists in this field are focusing on incorporation of apoptosis and necrosis inhibitors (zVAD-fmk, p38 MAPK inhibitor, ROCK inhibitor, etc.) to cryopreservation and post-thaw culture media. These inhibitors target and inhibit various proteins such as caspases, proteases, and kinases, involved in the cell death cascade, resulting in reduced intensity of apoptosis and necrosis in the cryopreserved cells and tissues, increased cell viability, and maintenance of cellular function; thus improved overall cryopreservation efficiency is achieved. The present article provides an overview of various cell death pathways, molecules mediating cryopreservation-induced apoptosis and the potential of certain molecules in targeting cryopreservation-induced delayed-onset cell death.

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

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

Increased apoptosis in cryopreserved autologous hematopoietic progenitor cells collected by apheresis and delayed neutrophil recovery after transplantation: a nested case-control study

BACKGROUND AIMS

Delayed neutrophil recovery following autologous hematopoietic stem cell transplantation (aHSCT) increases transplant-related morbidity. Apoptosis induced by cryopreservation and thawing of hematopoietic progenitor cells collected by apheresis (HPC-A) was investigated in this nested case-control study as a factor associated with delayed neutrophil recovery following aHSCT.

METHODS

Among patients with lymphoma who underwent aHSCT between 2000 and 2007 (n = 326), 13 cases of primary delayed neutrophil recovery and 22 age- and sex-matched controls were identified. Apoptosis and viability were measured using multiparameter flow cytometry, and colony-forming capacity was determined using semi-solid methylcellulose assays.

RESULTS

HPC-A grafts from cases and controls had similar percentages of viable mononuclear cells (MNC) and CD34+ progenitor cells, as determined by standard 7AAD dye exclusion methods measured before and after cryopreservation. Patients with delayed neutrophil recovery received increased numbers of apoptotic MNC (P = 0.02) but similar numbers of apoptotic CD34+ cells per kilogram measured after thawing. Apoptosis was more pronounced in MNC compared with CD34+ cells after thawing, and apoptosis was negligible in freshly collected HPC-A products. Patients with delayed neutrophil recovery had fewer total colony-forming unites (CFU) and CFU-granulocyte-macrophages (GM) per 10(5) viable post-thaw MNC compared with controls (P < 0.05).

CONCLUSIONS

Increased numbers of apoptotic MNC in thawed HPC-A products are associated with delayed neutrophil recovery after aHSCT. Studies that address factors contributing to increased apoptosis are needed, and measuring apoptosis in thawed HPC-A may have a role in the assessment of graft adequacy.

Specific cellular signal-transduction responses to in vivo combination therapy with ATRA, valproic acid and theophylline in acute myeloid leukemia

Acute myeloid leukemia (AML) frequently comprises mutations in genes that cause perturbation in intracellular signaling pathways, thereby altering normal responses to growth factors and cytokines. Such oncogenic cellular signal transduction may be therapeutic if targeted directly or through epigenetic regulation. We treated 24 selected elderly AML patients with all-trans retinoic acid for 2 days before adding theophylline and the histone deacetylase inhibitor valproic acid (ClinicalTrials.gov NCT00175812; EudraCT no. 2004-001663-22), and sampled 11 patients for peripheral blood at day 0, 2 and 7 for single-cell analysis of basal level and signal-transduction responses to relevant myeloid growth factors (granulocyte-colony-stimulating factor, granulocyte/macrophage-colony-stimulating factor, interleukin-3, Flt3L, stem cell factor, erythropoietin, CXCL-12) on 10 signaling molecules (CREB, STAT1/3/5, p38, Erk1/2, Akt, c-Cbl, ZAP70/Syk and rpS6). Pretreatment analysis by unsupervised clustering and principal component analysis divided the patients into three distinguishable signaling clusters (non-potentiated, potentiated basal and potentiated signaling). Signal-transduction pathways were modulated during therapy and patients moved between the clusters. Patients with multiple leukemic clones demonstrated distinct stimulation responses and therapy-induced modulation. Individual signaling profiles together with clinical and hematological information may be used to early identify AML patients in whom epigenetic and signal-transduction targeted therapy is beneficial.

Genes of cell-cell interactions, chemotherapy detoxification and apoptosis are induced during chemotherapy of acute myeloid leukemia

Background

The molecular changes in vivo in acute myeloid leukemia cells early after start of conventional genotoxic chemotherapy are incompletely understood, and it is not known if early molecular modulations reflect clinical response.

Methods

The gene expression was examined by whole genome 44 k oligo microarrays and 12 k cDNA microarrays in peripheral blood leukocytes collected from seven leukemia patients before treatment, 2–4 h and 18–24 h after start of chemotherapy and validated by real-time quantitative PCR. Statistically significantly upregulated genes were classified using gene ontology (GO) terms. Parallel samples were examined by flow cytometry for apoptosis by annexin V-binding and the expression of selected proteins were confirmed by immunoblotting.

Results

Significant differential modulation of 151 genes were found at 4 h after start of induction therapy with cytarabine and anthracycline, including significant overexpression of 31 genes associated with p53 regulation. Within 4 h of chemotherapy the BCL2/BAX and BCL2/PUMA ratio were attenuated in proapoptotic direction. FLT3 mutations indicated that non-responders (5/7 patients, 8 versus 49 months survival) are characterized by a unique gene response profile before and at 4 h. At 18–24 h after chemotherapy, the gene expression of p53 target genes was attenuated, while genes involved in chemoresistance, cytarabine detoxification, chemokine networks and T cell receptor were prominent. No signs of apoptosis were observed in the collected cells, suggesting the treated patients as a physiological source of pre-apoptotic cells.

Conclusion

Pre-apoptotic gene expression can be monitored within hours after start of chemotherapy in patients with acute myeloid leukemia, and may be useful in future determination of therapy responders. The low number of patients and the heterogeneity of acute myeloid leukemia limited the identification of gene expression predictive of therapy response. Therapy-induced gene expression reflects the complex biological processes involved in clinical cancer cell eradication and should be explored for future enhancement of therapy.

Hematopoietic stem cell transplantation for chronic lymphocytic leukemia: potential cure for an incurable disease

Hematopoietic stem cell transplantation (HSCT) has been used as a treatment modality in patients with chronic lymphocytic leukemia (CLL). Allogeneic HSCT is the only therapy at present that has curative potential in patients with CLL. Allogeneic HSCT using standard myeloablative regimens has been generally associated with high treatment mortality rates and autologous HSCT with high relapse rates. Over the last decade the use of reduced intensity conditioning (non-myeloablative) regimens have reduced the treatment-related mortality after allogeneic-HSCT without affecting the graft-versus-leukemia effectiveness. In addition, the development of molecular and biologic markers has identified high-risk CLL patients that may benefit from earlier treatment with HSCT. This review summarizes the use of existing prognostic markers in CLL and their use in HSCT, and the advances, indications and clinical outcomes of both autologous HSCT and allogeneic HSCT.

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

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

Evaluation of the Reactivity of Apoptosis Markers Before and After Cryopreservation in Cord Blood CD34+Cells

Umbilical cord blood (CB) CD34(+) cells, on the basis of flow cytometry analysis, are comprised of multiple populations. In in vitro assays, only CD34(regular) FSC(high) cells are functional and low percentages of nonfunctional CD34(regular) FSC(low) cells were determined to be present in liquid-stored CB. Liquid-stored CD34(regular) FSC(high) cells prior to cryopreservation were judged to be functional by the formation of erythroid and myeloid colonies and transmigration assays. We have further evaluated the occurrence of apoptosis in CB CD34(+) cells using various apoptotic markers to understand better the influence of storage conditions that could be utilized with transplantation of CB. Of the CD34(regular) FSC(low) cells shown in the present study, 20-45% were labeled with the apoptotic reagents annexin-V, fluorescent caspase peptide substrates, and the anti-mitochondrial antibody APO2.7, but these cells were minimally stained with 7-aminoactinomycin-D (7-AAD). These apoptotic reagents identify different cellular targets, indicating the initiation of the apoptotic cascade prior to cryopreservation/thawing. Following cryopreservation and thawing, the apoptotic markers SYTO-16, tetramethyl rhodamine ethyl ester (TMRE), and 7-AAD showed the presence of apoptotic cells. After cryopreservation/thawing, enumeration of CB CD34(+) cells was reduced 10-65% when excluding cells positive for apoptotic markers. We attempted to limit the progression of apoptosis observed after cryopreservation/thawing by the addition of anti-apoptotic reagents z-VAD-fmk (100 microM) and Q-VD-OPH (100 microM) (peptide inhibitors of caspases) without or with the inclusion of survival reagents for CD34(+) cells-stromal-derived factor-1 (SDF-1), stem cell factor (SCF), thrombopoietin, and diprotin A, an inhibitor of CD26 prior to cryopreservation. The expression of apoptosis markers was minimally affected even when using combinations of caspase inhibitors/ CD34(+) cell survival cytokines in an attempt to block apoptosis caused by cryopreservation/thawing. Decreases in apoptosis marker reactivity following cryopreservation were not observed except for a reduced expression of APO2.7 reactivity with z-VAD-fmk and Q-VD-OPH caspase inhibitors. The ability of the inhibitors of apoptosis of CD34(+) cells to generate CFU-GM, CFU-MK, or BFUE colonies was also unaffected except with z-VAD-fmk (100 microM) and Q-VD-OPH (100 microM). The occurrence of apoptosis, as measured by flow cytometry with selected apoptotic markers, suggests a reduction in the number of viable CD34(+) cells.

Prevention of apoptosis as a possible mechanism behind improved cryoprotection of hematopoietic cells by catalase and trehalose

BACKGROUND

Our previous in vitro work has shown the usefulness of membrane stabilizers and antioxidants as additives in conventional freezing medium to freeze mouse and human hematopoietic cells. The present work was carried out using murine model to test the in vivo engraftment ability of mouse bone marrow frozen with (test cells) or without (control cells) addition of a combination of trehalose and catalase in the medium containing 10% dimethyl sulfoxide (DMSO).

METHODS

Viability, nucleated cell recovery, and progenitor content of revived cells were measured. Freezing efficacy was tested by in vivo assays like colony forming unit-spleen (CFU-S), pre-CFU-S, and short-term engraftment of frozen marrow in irradiated mice. Long-term engraftment ability of frozen marrow was assessed using a Ly5.1-Ly 5.2 chimera model. Levels of apoptosis and reactive oxygen species (ROS) generated in revived cells were estimated. The former by Annnexin V, TUNEL, and DNA laddering and the latter by DCFH-DA probe.

RESULTS

Our results show that the combination of catalase and trehalose with 10% DMSO improves freezing efficacy not only in terms of viability, cell recovery, and progenitor content but also by in vivo assays like CFU-S, pre-CFU-S, and short- and long-term engraftment. Both the level of apoptosis and ROS generation were considerably reduced in test set as compared to control set.

CONCLUSIONS

We conclude that inclusion of a combination of trehalose and catalase in conventional freezing medium leads to enhanced engraftment potential of cryopreserved mouse bone marrow cells probably by preventing apoptotic cell death. Our observation using animal model may have significant clinical implications.

Apoptotic and necrotic cells induced by different agents vary in their expression of MHC and costimulatory genes

We have recently reported, in a murine tumor model, that apoptotic cells induced by different agents may vary in their ability to elicit host immunity. The basis for this observation is unclear but may involve varying efficiencies of cross-presentation and/or direct activation of immunity by different apoptotic preparations. As a first step in addressing this issue, we compared expression patterns of selected immune genes (MHC class I, class II, CD40, B7-1, B7-2) on viable and apoptotic populations induced by four different agents. The histone deacetylase inhibitor trichostatin A (TSA) induced MHC class II expression on viable and apoptotic cell populations, while LPAM, H2O2 and gamma-irradiation did not activate class II. Each agent employed elicited a different expression pattern of costimulatory molecules (CD40, B7-1, B7-2) on both apoptotic and 7-AAD+ 'necrotic' populations. In striking contrast to the TSA induction of MHC class II, class I cell surface protein was diminished on the apoptotic populations. These effects were not a result of changes in the cell cycle produced by the various treatments. The data demonstrate that distinctive gene expression patterns on viable and apoptotic cells are elicited by different apoptosis inducing agents. We discuss how expression patterns on dead or dying tumor cells could potentially affect the tumor's ability to elicit immunity.

Autologous transplantation: the viable transplanted CD34+ cell dose measured post-thaw does not predict engraftment kinetics better than the total CD34+ cell dose measured pre-freeze in patients that receive more than 2×106 CD34+ cells/kg

BACKGROUND

The aim of the study was to investigate whether the number of viable CD34+ cells in cryopreserved PBPC autografts is a better predictor of engraftment than the total CD34+ cell number determined before freezing.

METHODS

A total of 119 patients was treated with autotransplantation for various malignant disorders during the period 1996-2002. All patients were reinfused with at least 2x10(6)/kg total CD34 cells analyzed before programmed freezing in 10% DMSO. The total CD34 cell number determined before freezing was compared with the number of viable cells determined after cryopreservation for 51 of these patients. The number of viable cells was determined by a flow cytometric analysis including triple staining with anti-CD34, anti-CD45 and the viability marker 7-actinomycin D (7-AAD).

RESULTS

Simple linear regression analyses showed that both the total transplanted CD34 cell dose measured before freezing and the viable CD34 cell dose determined after cryopreservation were significantly correlated with neutrophil and platelet engraftment. In a multiple regression model the prediction of engraftment was not improved when the transplanted viable CD34 cell dose was included as a variable in addition to the total CD34 cell dose measured immediately after collection.

DISCUSSION

Routine estimation of viable CD34 cells after cryopreservation of PBPC autografts is not necessary as long as the total CD34 cell dose is determined before freezing and the patients are reinfused with at least 2x10(6) cells/kg body weight.

No differences in colony formation of peripheral blood stem cells frozen with 5% or 10% dimethyl sulfoxide

High-dose chemotherapy with autologous stem cell rescue usually requires cryopreservation of the cells. For several years, 10% dimethyl sulfoxide (DMSO) has been used as the standard cryoprotectant. Because DMSO infusion can lead to toxic clinical complications in a dose-related manner, we wanted to evaluate if reduction to 5% DMSO would be possible. We have compared colony formation in the myeloid, erythropoietic, and megakaryocyte lineages in peripheral blood progenitor cell (PBPC) samples cryopreserved in parallel with 5% and 10% DMSO. Twenty-seven PBPC samples from patients with malignant diseases were investigated after 3 months of cryopreservation in liquid N(2), and samples from 14 of these patients were investigated after 1 year. A significantly higher colony formation was demonstrated for colony-forming units-erythrocyte (CFU-E) and CFU-granulocyte, erythrocyte, macrophage, megakaryocyte (GEMM) both at 3 months and at 1 year in the 5% samples. For CFU-granulocyte-macrophage (GM) and CFU-megakaryocyte (Mk) no significant difference was demonstrated neither at 3 months nor at 1 year in samples frozen with 5% and 10% DMSO. Also, there was a statistically significant correlation between the CFU-total and CFU-Mk-total, indicating that the CFU-total might be used as an evaluation of megakaryocyte progenitors. Viability testing with the Trypan Blue exclusion test showed that cells cryopreserved in 5% DMSO had significantly higher viability than the cells cryopreserved in 10% DMSO. We conclude that 5% DMSO is at least as good for cryopreservation of small-volume PBPC samples as the conventional 10% DMSO, and our results suggest that the possibility of using 5% DMSO for cryopreservation of autologous PBPC grafts should be further investigated in clinical studies.

In vitro culture of human acute lymphoblastic leukemia (ALL) cells in serum-free media; a comparison of native ALL blasts, ALL cell lines and virus-transformed B cell lines

The aim of this study was to standardize in vitro culture conditions for human acute lymphoblastic leukemia (ALL) cells. The cells were cultured in medium containing 10% fetal calf serum (FCS) and in the four serum-free media X-vivo 10, X-vivo 15, X-vivo 20 and Stem Span. Native ALL blasts could proliferate in all four serum-free media, but the strongest responses were usually observed with Stem Span. Native leukemia blasts were also cultured in the presence of various single cytokines or cytokine combinations. The highest proliferation was usually observed in the presence of Flt3-Ligand (Flt3-L) when single cytokines were examined, and these responses could be further increased especially by combining Flt3-L with interleukin 3 (IL3), IL7 or stem cell factor (SCF). Proliferation could also be increased when ALL blasts were cultured in the presence of two commercially available fibroblast cell lines (Hs27 and HFL1). Based on these results we suggest that in vitro culture conditions for native human ALL blasts can be standardized by using serum-free culture media supplemented with exogenous Flt3-L+IL3+SCF, and the use of accessory cells can also be standardized by using well-characterized fibroblast cell lines. Detectable ALL blast proliferation can then be observed for most patients. Our experimental model can thereby be used for in vitro evaluation of possible antileukemic treatment strategies, and it will then allow comparison of experimental results between different studies.

Cryopreserving human peripheral blood progenitor cells with 5-percent rather than 10-percent DMSO results in less apoptosis and necrosis in CD34+ cells

BACKGROUND

The grade of toxicity experienced by patients when cryopreserved peripheral blood progenitor cells (PBPCs) are reinfused is related to the amount of DMSO present in the PBPC concentrate. This study was initiated to investigate whether cell viability, apoptosis, and necrosis would be altered in CD34+ cells if PBPCs were cryopreserved with 5-percent as opposed to the conventional 10-percent DMSO.

STUDY DESIGN AND METHODS

Samples of PBPCs from consecutive patients were mixed in parallel with 5- and 10-percent DMSO, frozen at a controlled rate, and stored in liquid nitrogen for periods of 3 to 22 months. Two different flow cytometric methods were used to measure both the absolute count of total and viable CD34+ cells as well as the fraction of apoptotic and necrotic cells in the post-thaw samples frozen with 5- and 10-percent DMSO.

RESULTS

Both the number of total and viable CD34+ cells were higher (n = 18) or equal (n = 1) in all the samples cryopreserved with 5-percent as opposed to 10-percent DMSO. The percentage of viable CD34+ cells in the PBPC sample was significantly higher, and the fraction of apoptotic and necrotic CD34+ cells was significantly lower in the samples frozen with 5-percent as compared to 10-percent DMSO.

CONCLUSION

Cryopreserving PBPC with 5-percent rather than 10-percent DMSO results in improved CD34+ cell viability and possibly a higher potential for in vivo engraftment and ex vivo manipulations of HPCs.

Early apoptosis largely accounts for functional impairment of CD34+ cells in frozen-thawed stem cell grafts

Quality assessment of stem cell grafts is usually performed by flow cytometric CD34(+) enumeration or assessment of clonogenic output of fresh material. Previously, we identified the occurrence of early apoptosis, not detectable with the permeability marker 7-amino actinomycin D (7-AAD), in purified frozen-thawed CD34(+) cells, using the vital stain Syto16. Syto(high)/7-AAD(-) cells were defined as viable, Syto16(low)/7-AAD(-) cells as early apoptotic and Syto16(low)/7-AAD(+) as dead. This was confirmed in a subsequent study using frozen-thawed transplants of lymphoma patients. In the present study on grafts from multiple myeloma and lymphoma patients, we investigated the functional consequences of the early apoptotic process. The mean Syto16-defined viability was 41 and 42%, respectively, for both graft groups, compared to 78% and 72%, respectively, using 7-AAD only. The established early apoptosis marker annexin V missed roughly 50% of the early apoptosis detected with Syto16. In contrast, viability of CD34(+) cells in nonmanipulated whole blood transplants from a matched group of lymphoma patients, after 72 h of storage at 4 degrees C, was more than 90%, even with the Syto16 assay. CFU recovery (median 26-33%) after cryopreservation matched CD34(+) recovery after Syto16, but not 7-AAD correction. In contrast, colony-forming unit (CFU) recovery in the whole blood transplant was close to 100%. Furthermore, early apoptotic CD34(+) cells had lost migratory ability toward stromal cell derived factor-1alpha (SDF-1alpha). The establishment of a Syto16(high)/7-AAD(-) proportion of CD34(+) cells offers a new approach for a more correct determination of the number of viable nonapoptotic CD34(+) cells in stem cell grafts. Further development of this assay should allow its incorporation into the routine CD34(+) assessment of post-thawed samples in clinical flow cytometry laboratories.