Association of post-thaw viable CD34+ cells and CFU-GM with time to hematopoietic engraftment

Long-Term Cryopreservation of Peripheral Blood Stem Cell Harvest Using Low Concentration (4.35%) Dimethyl Sulfoxide with Methyl Cellulose and Uncontrolled Rate Freezing at -80 °C: An Effective Option in Resource-Limited Settings

Long-term cryopreservation of peripheral blood stem cells (PBSCs) is highly useful in the setting of tandem/multiple transplantations or treatment of relapse in the autologous hematopoietic stem cell transplantation (HSCT) setting. Even in allogeneic HSCT, donor lymphocyte infusions may be stored for months to years if excess stem cells are collected from donors. Cryopreservation is a delicate, complex, and costly procedure, and higher concentrations of dimethyl sulfoxide (DMSO), a commonly used cryoprotectant, can be toxic to cells and cause adverse effects in the recipient during infusions. In this study, we examined the effect of long-term cryopreservation using 4.35% DMSO (as final concentration) with methyl cellulose and uncontrolled rate freezing in a mechanical freezer (-80 °C) on the viability and colony-forming ability of CD34+ human PBSCs. For patients undergoing autologous HSCT, PBSCs were cryopreserved using DMSO (final concentration of 4.35%) with methyl cellulose. The post-thaw viability of PBSCs was determined using Trypan blue exclusion and flow cytometry-based 7-amino-actinomycin-D (FC-7AAD) methods. Concentrations of CD34+ stem cells and immune cell subsets in post-thaw PBSC harvest samples were assessed using multicolor flow cytometry, and the clonogenic potential of post-thaw stem cells was studied using a colony-forming unit (CFU) assay. CD34+ stem cell levels were correlated with the prestorage CD34 levels using the Pearson correlation test. The viability results in the Trypan blue dye exclusion method and the flow cytometry-based method were compared using Bland-Altman plots. We studied 26 PBSC harvest samples with a median cryopreservation duration of 6.6 years (range, 3.8 to 11.5 years). The median viability of post-thaw PBSCs was >80% using both methods, with a weak agreement between them (r = .03; P = .5). The median CD34+ stem cell count in the post-thaw samples was 9.13 × 106/kg (range, .44 to 26.27 × 106/kg). The CFU assay yielded a good proliferation and differentiation potential in post-thaw PBSCs, with a weak correlation between granulocyte macrophage CFU and CD34+ stem cell levels (r = .4; P = .05). Two samples that had been cryopreserved for >8 years showed low viability. Cryopreservation of PBSCs using 4.35% DMSO with methyl cellulose and uncontrolled freezing in a mechanical freezer at -80 °C allows the maintenance of long-term viability of PBSC for up to 8 years.

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.

Variable recovery of cryopreserved hematopoietic stem cells and leukocyte subpopulations in leukapheresis products

INTRODUCTION

Due to the expansion of cell therapy using not only haematopoietic stem cells (HSC) but also other leukocyte subpopulations, the loss of these cells in cryopreserved apheresis products needs to be evaluated. Various factors that could negatively affect post-thaw recovery, such as leukapheresis product characteristics, storage time and cryopreservation protocols have been identified.

METHODS

The post-thaw recovery of HSCs, lymphocytes, NK cells and monocytes, as well as the factors that could adversely affect it were analysed in autologous and allogeneic leukapheresis products.

RESULTS

The lowest post-thaw recovery was observed in autologous and allogeneic CD34+ cells, with the median of 73.7% and 68.1%, respectively. In leukocyte subpopulation, the lowest post-thaw recovery was observed for CD14+ cells, both autologous and allogeneic. The highest post-thaw recovery was observed for CD3+/CD8+ cells in autologous, and for CD19+ cells in allogeneic samples. The statistically significant difference was observed between autologous and allogeneic PBSC products for CD3+ cell recovery (P = 0.031) and CD3+/CD8+ cell recovery (P = 0.009). The evaluation of factors that could adversely affect the post-thaw recovery in autologous samples showed weak negative correlations between platelet concentration and CD3+ recovery, as well as between storage time and CD3+CD8+ recovery. In allogeneic samples, a strong negative correlation was observed only between the percentage of granulocytes and CD3+, CD3+/CD8+ and CD3+/CD4+ cell recoveries.

CONCLUSION

Since various post-thaw recoveries of leukocyte subpopulations were observed, the cell therapy manufacturing centers should evaluate how their cryopreservation method and other factors affect the recovery of cell population of interest in their settings.

A critical assessment of dose effects of post-thaw CD34 on autologous stem cell transplantation treatment of haematological malignancies

A consensus threshold of pre-cryopreservation CD34-positive cells (CD34s) has been used as the minimum dose to initiate autologous stem cell transplantation (ASCT). Advances in cryopreservation posed a debate whether post-thaw CD34s might be a superior surrogate instead. We addressed the debate in this retrospective study of 217 adult ASCTs in five different haematological malignancies treated at a single centre. We showed that post-thaw CD34s was highly correlated with pre-cryopreservation CD34s (r = 0.97) and explained ∼2.2% (p = 0.003) of the variation of the post-thaw total nucleated cell viability that however had no power to predict engraftment outcomes. After stratifying the ASCT cases into four dose groups based on post-thaw CD34s reinfused, stepwise multivariate regression analyses detected significant effects in dose group and interactions with diseases for neutrophil and platelet recovery respectively. The significant dose effects and interactions were triggered by two technical outliers in the low dose group, and disappeared in the repeated regressions after exclusion of the outliers where disease and age were the significant predictors remained. Our data clearly support the validity of the consensus threshold in ASCT applications but also highlight neglected conditions where monitoring post-thaw CD34s and clinical attributes are valuable.

Leukocytapheresis variables and transit time for allogeneic cryopreserved hpc: better safe than sorry

Cryopreservation was recommended to ensure continuity in allogeneic hematopoietic progenitor cells (HPC) transplantation during the COVID-19 pandemic. Several groups have shown no impact on clinical outcomes for patients who underwent HPC transplantation with cryopreserved products during the first months of this pandemic. However, concerns about quality control attributes after cryopreservation have been raised. We investigated, in 155 allogeneic peripheral blood cryopreserved HPC, leukocytapheresis characteristics influencing viable CD34⁺ and CD3⁺ cells, and CFU-GM recoveries after thawing. Collection characteristics such as volume, nucleated cells (NC)/mL and hematocrit correlated with viable CD34⁺ and CD3⁺ cells recoveries after thawing in univariate analysis but only CD3⁺ cells remained statistically significant in multivariate analysis (r2 = 0.376; P = < 0.001). Additionally, transit time also showed correlation with viable CD34⁺ (r2 = 0.186), CD3⁺ (r2 = 0.376) and CFU-GM recoveries (r2 = 0.212) in multivariate analysis. Thus, diluting leukocytapheresis below 200 × 10⁶ NC/mL, avoiding red cells contamination above 2%, cryopreserving below 250 × 10⁶ NC/mL and minimizing transit time below 36 h, prevented poor viable CD34⁺ and CD3⁺ cells, and CFU-GM recoveries. In summary, optimizing leukocytapheresis practices and minimizing transportation time may better preserve the quality attributes of HPC when cryopreservation is indicated.

FACTORS INFLUENCING POST- CRYOPRESERVED CD34+ CELLS VIABILITY IN THE HARVESTED PRODUCTS OF AUTOLOGOUS HAEMATOPOIETIC STEM CELLS

The cryopreservation process of stem cells potentially cause the loss of CD34+ cells. The aim of this study is to evaluate association of patient, graft and technical characteristics with post cryopreserved CD34+ cells viability among lymphoproliferative disease namely multiple myeloma (MM) and lymphoma patients at Hospital Universiti Sains Malaysia (USM). This retrospective study was conducted in the Transplant Unit. A search of the hospital data (2008-2018) to identify 132 patients for both MM and lymphoma who underwent autologous peripheral blood haematopoietic stem cells (APBSC) mobilisation, and were successfully harvested and cryopreserved. Selected patients' profile as well as selected parameters of stem cell mobilization and cryopreservation were obtained from laboratory information system (LIS), record unit and the Transplant Unit. Multiple logistic regression (MLR) was used to find significant associated factors and p <0.05 was considered significant. The mean age of the patients was 39 years old with almost equal gender distribution and majority were lymphoma patients, 96 (72.7%) while 36 (27.3%) were multiple myeloma (MM) patients. The significant influencing factors of post-cryopreserved CD34+ cells viability were pre-cryopreserved CD34+ cell viability, total nucleated cells (TNC), and anti-platelet and antibiotics usage. Patients who are not on anti-platelet and have higher pre-cryopreserved CD34+ cells viability have higher chance for good post-cryopreserved CD34+ cells viability. While, those patients with higher TNC and on antibiotics have lower chance for good post cryopreserved CD34+ cells viability. This study showed patients who are not on anti-platelet and antibiotics will have higher probability of achieving good post cryopreserved CD34+ cells viability. The APBSC products with higher pre-cryopreserved CD34+ cells viability and lower TNC will achieve better post-cryopreserved CD34+ cells viability. The addition of extra plasma to the APBSC products is recommended to reduce the TNC.

Assessment of the Impact of Post-Thaw Stress Pathway Modulation on Cell Recovery following Cryopreservation in a Hematopoietic Progenitor Cell Model

The development and use of complex cell-based products in clinical and discovery science continues to grow at an unprecedented pace. To this end, cryopreservation plays a critical role, serving as an enabling process, providing on-demand access to biological material, facilitating large scale production, storage, and distribution of living materials. Despite serving a critical role and substantial improvements over the last several decades, cryopreservation often remains a bottleneck impacting numerous areas including cell therapy, tissue engineering, and tissue banking. Studies have illustrated the impact and benefit of controlling cryopreservation-induced delayed-onset cell death (CIDOCD) through various “front end” strategies, such as specialized media, new cryoprotective agents, and molecular control during cryopreservation. While proving highly successful, a substantial level of cell death and loss of cell function remains associated with cryopreservation. Recently, we focused on developing technologies (RevitalICE™) designed to reduce the impact of CIDOCD through buffering the cell stress response during the post-thaw recovery phase in an effort to improve the recovery of previously cryopreserved samples. In this study, we investigated the impact of modulating apoptotic caspase activation, oxidative stress, unfolded protein response, and free radical damage in the initial 24 h post-thaw on overall cell survival. Human hematopoietic progenitor cells in vitro cryopreserved in both traditional extracellular-type and intracellular-type cryopreservation freeze media were utilized as a model cell system to assess impact on survival. Our findings demonstrated that through the modulation of several of these pathways, improvements in cell recovery were obtained, regardless of the freeze media and dimethyl sulfoxide concentration utilized. Specifically, through the use of oxidative stress inhibitors, an average increase of 20% in overall viability was observed. Furthermore, the results demonstrated that by using the post-thaw recovery reagent on samples cryopreserved in intracellular-type media (Unisol™), improvements in overall cell survival approaching 80% of non-frozen controls were attained. While improvements in overall survival were obtained, an assessment on the impact of specific cell subpopulations and functionality remains to be completed. While work remains, these results represent an important step forward in the development of improved cryopreservation processes for use in discovery science, and commercial and clinical settings.

Effects of storage media, supplements and cryopreservation methods on quality of stem cells

Despite a vast amount of different methods, protocols and cryoprotective agents (CPA), stem cells are often frozen using standard protocols that have been optimized for use with cell lines, rather than with stem cells. Relatively few comparative studies have been performed to assess the effects of cryopreservation methods on these stem cells. Dimethyl sulfoxide (DMSO) has been a key agent for the development of cryobiology and has been used universally for cryopreservation. However, the use of DMSO has been associated with in vitro and in vivo toxicity and has been shown to affect many cellular processes due to changes in DNA methylation and dysregulation of gene expression. Despite studies showing that DMSO may affect cell characteristics, DMSO remains the CPA of choice, both in a research setting and in the clinics. However, numerous alternatives to DMSO have been shown to hold promise for use as a CPA and include albumin, trehalose, sucrose, ethylene glycol, polyethylene glycol and many more. Here, we will discuss the use, advantages and disadvantages of these CPAs for cryopreservation of different types of stem cells, including hematopoietic stem cells, mesenchymal stromal/stem cells and induced pluripotent stem cells.

Allogeneic transplant procurement in the times of COVID-19: Quality report from the central European cryopreservation site

Background

Because of limitations of transportation imposed by the COVID-19 pandemic, current recommendation calls for cryopreservation of allogeneic stem cell transplants before patient conditioning. A single cell therapy laboratory was selected to function as the central cryopreservation hub for all European registry donor transplants intended for the Australian-Pacific region. We examined properties of these transplants to ascertain how quality is maintained.

Methods

We analyzed 100 pandemic-related allogeneic mobilized blood-derived stem cell apheresis products generated at 30 collection sites throughout Europe, shipped to and cryopreserved at our center between April and November of 2020. Products were shipped in the cool, subsequently frozen with DMSO as cryoprotectant. Irrespective of origin, all products were frozen within the prescribed shelf-life of 72 h.

Results

Prior to cryopreservation, viable stem cell and leukocyte count according to the collection site and our reference laboratory were highly concordant (r² = 0.96 and 0.93, respectively) and viability was > 90% in all instances. Median nominal post-thaw recovery of viable CD34+ cells was 42%. Weakly associated with poorer CD34+ cell recovery was higher leukocyte concentration, but not time lag between apheresis or addition of cryopreservant, respectively, and start of freezing. The correlation between pre- and post-thaw CD34+ cell dose was high (r² = 0.85), hence predictable. Neutrophil and platelet engraftment were prompt with no evidence of dose dependency within the range of administered cell doses (1.31–15.56 × 10⁶ CD34+ cells/kg).

Conclusions

General cryopreservation of allogeneic stem cell transplants is feasible. While more than half of the CD34+ cell content is lost, the remaining stem cells ensure timely engraftment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02810-9.

Current and Future Perspectives for the Cryopreservation of Cord Blood Stem Cells

Hematopoietic stem cell (HSC) transplantation is a well-established procedure for the treatment of many blood related malignancies and disorders. Before transplantation, HSC are collected and cryopreserved until use. The method of cryopreservation should preserve both the number and function of HSC and downstream progenitors responsible for long- and short-term engraftment, respectively. This is especially critical for cord blood grafts, since the cell number associated with this stem cell source is often limiting. Loss of function in cryopreserved cells occurs following cryoinjuries due to osmotic shock, dehydration, solution effects and mechanical damage from ice recrystallization during freezing and thawing. However, cryoinjuries can be reduced by 2 mitigation strategies; the use of cryoprotectants (CPAs) and use of control rate cooling. Currently, slow cooling is the most common method used for the cryopreservation of HSC graft. Moreover, dimethyl-sulfoxide (DMSO) and dextran are popular intracellular and extracellular CPAs used for HSC grafts, respectively. Yet, DMSO is toxic to cells and can cause significant side effects in stem cells' recipients. However, new CPAs and strategies are emerging that may soon replace DMSO. The aim of this review is to summarise key concepts in cryobiology and recent advances in the field of HSC cryobiology. Other important issues that need to be considered are also discussed such as transient warming events and thawing of HSC grafts.

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

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

The role of the novel LincRNA uc002jit.1 in NF-kB-mediated DNA damage repair in acute myeloid leukemia cells

The roles and therapeutic potential of long noncoding RNAs (lncRNAs) in acute myeloid leukemia (AML) have attracted increased attention. However, many lncRNAs have not been annotated in AML, and their predictive value for AML therapy remains unclear. In this study, we identified a novel large intergenic noncoding RNA uc002jit.1 (D43770) from a lncRNA microarray. We first proved uc002jit.1 is a target gene of nuclear factor kappa B/RELA, RELA regulated uc002jit.1 transcription by binding to its promoter. Additionally, uc002jit.1 knockdown impaired the stability of poly (ADP-ribose) polymerase 1 (PARP1) mRNA, and then reduced PARP1 protein content and PARylation level upon DNA damage, thus inhibiting DNA damage repair in AML cells. Moreover, uc002jit.1 knockdown significantly inhibited AML cells proliferation and increased the sensitivity to chemotherapeutic drugs in vitro as well as in a mouse model in vivo. Overall, our study indicated that uc002jit.1 may be associated with the occurrence and prognosis of AML and could be a new diagnostic/prognostic biomarker and therapeutic target for AML.

Manipulation, and cryopreservation of autologous peripheral blood stem cell products in Italy: A survey by GITMO, SIDEM and GIIMA societies

There is considerable heterogeneity in manipulation and cryopreservation of hematopoietic stem cells (HSC) for autologous HSC transplantation across Europe and Italy. To better address this point, three Italian Scientific Societies (GITMO- Gruppo Italiano per il Trapianto di Midollo Osseo; SIDEM- Società Italiana Emaferesi e Manipolazione Cellulare; and GIIMA- Gruppo Italiano Interdisciplinare Manipolazione e Aferesi per Terapie Cellulari), in collaboration with the Competent Authority "National Transplant Center" (CNT) sent to 85 Italian transplant centers (TC) a survey, which included 12 questions related to the most critical elements in graft processing. Fifty-nine centers (70 %) responded to the questionnaire. Overall, this survey demonstrates that the majority (>90 %) of responding TC used standardized procedures for HSC processing; however, an intercenter heterogeneity was clearly documented in several standard operating procedures adopted by different TC. These results seem to suggest that further standardization and efforts are needed to provide recommendations and guidelines on HSC manipulation, cryopreservation and functional assessment of cryopreserved material for autologous HSCT.

Sorting by interfacial tension (SIFT): label-free selection of live cells based on single-cell metabolism

Selection of live cells from a population is critical in many biological studies and biotechnologies. We present here a novel droplet microfluidic approach that allows for label-free and passive selection of live cells using the glycolytic activity of individual cells. It was observed that with the use of a specific surfactant utilized to stabilize droplet formation, the interfacial tension of droplets was very sensitive to pH. After incubation, cellular lactate release results in droplets containing a live cell to attain a lower pH than other droplets. This enables the sorting of droplets containing live cells when confined droplets flow over a microfabricated trench oriented diagonally with respect to the direction of flow. The technique is demonstrated with human U87 glioblastoma cells for the selection of only droplets containing a live cell while excluding either empty droplets or droplets containing a dead cell. This label-free sorting method, dubbed sorting by interfacial tension (SIFT) presents a new strategy to sort diverse cell types based on metabolic activity.

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.

Effect of cryopreservation on viability and growth efficiency of stromal-epithelial cells derived from neonatal human thymus

The thymus is the major site of T lymphocyte generation and so is critical for a functional adaptive immune system. Since, thymectomy is a component of neonatal surgery for congenital heart diseases, it provides great potential for collection and storage of thymic tissue for autologous transplantation. However, specific investigation into the optimum parameters for thymic tissue cryopreservation have not been conducted. In this research, we evaluated the effect of different cryoprotective media compositions, which included penetrating (Me₂SO, glycerol) and non-penetrating (dextran-40, sucrose, hydroxyethyl starch) components, on the viability and functionality of frozen-thawed human thymic samples to select an optimal cryoprotective medium suitable for long-term storage of thymic tissue and a stromal-epithelial enriched population. Our primary focus was on receiving, low-temperature storage, culturing and evaluation of thymic tissue samples from newborns and infants with congenital heart diseases, who had undergone thymectomy as a part of standard surgical procedure. Thus, this work builds the platform for autologous clinical intervention into the thymus-deficient patients with congenital heart diseases. From our data, we conclude that although there were no significant differences in efficiency of tested cryoprotective media compositions, the combination of Me₂SO and dextran-40 compounds was the most suitable for long-term storage both thymic cell suspensions and thymic fragments based on the viability of CD326⁺ epithelial cells and stromal-epithelial cell monolayer formation.

Microfluidic Sorting of Cells by Viability Based on Differences in Cell Stiffness

The enrichment of viable cells is an essential step to obtain effective products for cell therapy. While procedures exist to characterize the viability of cells, most methods to exclude nonviable cells require the use of density gradient centrifugation or antibody-based cell sorting with molecular labels of cell viability. We report a label-free microfluidic technique to separate live and dead cells that exploits differences in cellular stiffness. The device uses a channel with repeated ridges that are diagonal with respect to the direction of cell flow. Stiff nonviable cells directed through the channel are compressed and translated orthogonally to the channel length, while soft live cells follow hydrodynamic flow. As a proof of concept, Jurkat cells are enriched to high purity of viable cells by a factor of 185-fold. Cell stiffness was validated as a sorting parameter as nonviable cells were substantially stiffer than live cells. To highlight the utility for hematopoietic stem cell transplantation, frozen samples of cord blood were thawed and the purity of viable nucleated cells was increased from 65% to over 94% with a recovery of 73% of the viable cells. Thus, the microfluidic stiffness sorting can simply and efficiently obtain highly pure populations of viable cells.

Small-Molecule Ice Recrystallization Inhibitors Improve the Post-Thaw Function of Hematopoietic Stem and Progenitor Cells

The success of hematopoietic stem cell transplantation depends in part on the number and the quality of cells transplanted. Cryoinjuries during freezing and thawing reduce the ability of hematopoietic stem and progenitor cells (HSPCs) to proliferate and differentiate after thawing. Up to 20% of the patients undergoing umbilical cord blood (UCB) transplant experience delayed or failed engraftment, likely because of the inadequate hematopoietic potency of the unit. Therefore, the optimization of cryopreservation protocols, with an emphasis on the preservation of HSPCs, is an important issue. Current protocols typically utilize a 10% dimethyl sulfoxide cryoprotectant solution. This solution ensures 70-80% post-thaw cell viability by diluting intracellular solutes and maintaining the cell volume during cryopreservation. However, this solution fails to fully protect HSPCs, resulting in the loss of potency. Therefore, a new class of cryoprotectants (N-aryl-d-aldonamides) was designed and assessed for the ability to inhibit ice recrystallization and to protect HSPCs against cryoinjury. Several highly active ice recrystallization inhibitors were discovered. When used as additives to the conventional cryoprotectant solution, these nontoxic small molecules improved the preservation of functionally divergent hematopoietic progenitors in the colony-forming unit and long-term culture-initiating cell assays. By contrast, structurally similar compounds that did not inhibit ice recrystallization failed to improve the post-thaw recovery of myeloid progenitors. Together, these results demonstrate that the supplementation of cryopreservation solution with compounds capable of controlling ice recrystallization increases the post-thaw function and potency of HSPCs in UCB. This increase may translate into reduced risk of engraftment failure and allow for greater use of cryopreserved cord blood units.

miR-199b, a novel tumor suppressor miRNA in acute myeloid leukemia with prognostic implications

Background

Dysregulation of miRNAs that can act as tumor suppressors or oncogenes can result in tumorigenesis. Previously we demonstrated that miR-199b was significantly downregulated in acute myeloid leukemia (AML) and targets podocalyxin and discoidin domain receptor 1. Herein we investigated the functional role of miR-199b in AML and its prognostic implications.

Methods

Major approaches include transduction of hematopoietic stem cells and bone marrow transplantation, analyses of blood lineages, histone deacetylases (HDAC) inhibitors, and molecular and clinical data analyses of AML patients using The Cancer Genome Atlas (TCGA).

Results

We first examined the relative miR-199b expression in steady state hematopoiesis and showed CD33⁺ myeloid progenitors had the highest miR-199b expression. Further, silencing of miR-199b in CD34⁺ cells resulted in significant increases in CFU-GM colonies. Via TCGA we analyzed the molecular and clinical characteristics of 166 AML cases to investigate a prognostic role for miR-199b. The Kaplan–Meier curves for high and low expression values of miR-199b and the observed distribution of miRNA expression revealed the highly expressed group had significantly better survival outcomes (p < 0.016, log rank test). Additionally, there was significant difference between miR-199b expression across the AML subtypes with particularly low expression found in the FAB-M5 subtype. Furthermore, FAB-M5 subtype showed a poor prognosis with a 1-year survival rate of only 25 %, compared with 51 % survival in the overall sample (p < 0.024). Furthermore, significant inverse correlation of HoxA7 and HoxB6 expression with miR-199b was observed in FAB-M5 AML patients. Molecular mutations were analyzed among miR-199b high and low AML cases. Significant correlations in terms of association and survival outcomes were observed for NPMc and IDH1 mutations. Treatment of THP-1 cells (represents M5-subtype) with HDAC inhibitors AR-42, Panobinostat, or Decitabine showed miR-199b expression was significantly elevated upon AR-42 and Panobinostat treatment. To further understand the hematopathological consequences of decreased miR-199b, we employed a bone-marrow transduce/transplant (BMT) mouse model. Interestingly, in vivo miR-199b silencing per-se in HSCs did not result in profound perturbations.

Conclusions

Loss of miR-199b can lead to myeloproliferation while HDAC inhibitors restore miR-199b expression and promote apoptosis. Low miR-199b in AML patients correlates with worse overall survival and has prognostic significance for FAB-M5 subtype.

Electronic supplementary material

The online version of this article (doi:10.1186/s40164-016-0033-6) contains supplementary material, which is available to authorized users.

Transdifferentiation of Human Hair Follicle Mesenchymal Stem Cells into Red Blood Cells by OCT4

Shortage of red blood cells (RBCs, erythrocytes) can have potentially life-threatening consequences for rare or unusual blood type patients with massive blood loss resulting from various conditions. Erythrocytes have been derived from human pluripotent stem cells (PSCs), but the risk of potential tumorigenicity cannot be ignored, and a majority of these cells produced from PSCs express embryonic ε- and fetal γ-globins with little or no adult β-globin and remain nucleated. Here we report a method to generate erythrocytes from human hair follicle mesenchymal stem cells (hHFMSCs) by enforcing OCT4 gene expression and cytokine stimulation. Cells generated from hHFMSCs expressed mainly the adult β-globin chain with minimum level of the fetal γ-globin chain. Furthermore, these cells also underwent multiple maturation events and formed enucleated erythrocytes with a biconcave disc shape. Gene expression analyses showed that OCT4 regulated the expression of genes associated with both pluripotency and erythroid development during hHFMSC transdifferentiation toward erythroid cells. These findings show that mature erythrocytes can be generated from adult somatic cells, which may serve as an alternative source of RBCs for potential autologous transfusion.

The loss of CD34+ cells in peripheral hematopoietic stem cell products cryopreserved by non-controlled rate freezing and stored at -80 °C after overnight storage

Although peripheral blood stem cell (PBSC) products cryopreserved by non-controlled rate freezing and stored at -80 °C after overnight storage are used frequently, data regarding the rate of loss of CD34+ cells in these products are limited. In this prospective study, CD34+ cells were counted at three (fresh, post-overnight and post-thaw) points in 83 PBSC products from 41 patients by flow cytometry. Compared to fresh products, the mean losses of post-overnight and post-thaw total CD34+ cells are 16.3% and 38.4% (p = 0.02), and the mean losses of post-overnight and post-thaw viable CD34+ cells are 16.5% and 48.5%, respectively (p < 0.001). The numbers of fresh viable, post-thaw total and post-thaw viable CD34+ cells were inversely correlated with the durations of neutrophil and platelet engraftment. Our results indicate that the mean loss of post-thaw total and viable CD34+ cells is approximately 20% higher than that observed in standard cryopreservation methods. In addition, fresh viable, post-thaw total and especially post-thaw viable CD34+ cell levels are valuable predictors of both neutrophil and platelet engraftments.

Cryopreservation of Peripheral Blood Stem Cells Using a Box-in-Box Cooling Device

The cooling process is critical for the cryopreservation of human hematopoietic stem cells (HSCs). Currently, programmed freezing methods and uncontrolled cooling methods are in use, both having obvious disadvantages. In this article, a novel device termed Box-in-Box (BIB) was developed and evaluated by in vitro cryopreservation tests in 2 different operation modes ("against-side" mode for Group I (n = 10), and "in-middle" mode for Group II (n = 10), respectively), and compared with an uncontrolled cooling method (Group III (n = 7), Styrofoam boxes) as well as a conventional programmed freezer method (Group IV (n = 10), CryoMed TM 1010, Cryogenic Tech., FL). Recorded temperature profiles of samples cryopreserved with BIB show that a consistent cooling procedure with a rate around -1°C to -3.5°C/min can be achieved during their transfer from room temperature to an -80°C freezer. Statistical analysis of the stem cell population recovery, survival, and colony generation recovery shows that there is no significant difference (P > 0.26) among the methods using the BIB or programmed freezer (Group I, Group II, and Group IV), and their related deviations are smaller than the uncontrolled cooling rate method (Group III). Methods using the BIB (Group I and Group II) generated significantly better cell survival rate (P < 0.01) than the uncontrolled cooling rate method (Group III). The results indicate that the controlled cooling rate methods (BIB or CryoMed PF) are more consistent and reliable for clinical use. Considering the advantages of low cost, durability, and no liquid nitrogen consumption for the cooling process, the BIB can be a good alternative to the programmed freezers for the cryopreservation of HSCs.

A new system for quality control in hematopoietic progenitor cell units before reinfusion in autologous transplant

BACKGROUND

In our Center, the cell viability, the integrity of the bag, and the clonogenic assay were evaluated before the reinfusion of hematopoietic progenitor cells-apheresis (HPC-A). This quality control (QC) should be made 14 days before the reinfusion to the patient to have the result of the functional test on the proliferative capacity of hematopoietic progenitors.

STUDY DESIGN AND METHODS

This study was designed to assess the potential of an automatic cell counting system (NucleoCounter NC-3000, ChemoMetec) in our clinical routine as a support of the clonogenic assay and the cytofluorimetric analysis for the QC of the cryopreserved HPC-A. The cell viability was evaluated by flow cytometry using the modified International Society of Hematotherapy and Graft Engineering protocol. The proliferative potential was assessed by specific clonogenic tests using a commercial medium. Furthermore, we evaluated the cellular functionality with NucleoCounter NC-3000, by using two protocols: "vitality assay" and "mitochondrial potential assay."

RESULTS

The evaluation of the total nucleated cells in preapoptosis measured by 5,5,6,6-tetrachloro-1,1,3,3-tetraethylbenzimidazol-carbocyanine iodide (JC-1) assay showed a negative correlation (r=-0.43) with the total number of colonies (colony-forming unit [CFU]-granulocyte-macrophage progenitors plus burst-forming unit-erythroid progenitors plus CFU-granulocyte, erythroid, macrophage, megakaryocyte progenitors) obtained after seeding of 50 × 10(6) /L viable total nucleated cells. We observed a significant difference (p<0.0001) comparing the median number of colonies (166.70; SD, ± 136.36) obtained with a value of JC-1 less than 30% to the number of colonies (61.75; SD, ± 59.76) obtained with a value of JC-1 more than 30%.

CONCLUSION

The evaluation of cell functionality by the use of the NucleoCounter NC-3000 is in agreement with results from clonogenic assay and can be considered an effective alternative in the routine laboratory.

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.

Developing assays to address identity, potency, purity and safety: cell characterization in cell therapy process development

A major challenge to commercializing cell-based therapies is developing scalable manufacturing processes while maintaining the critical quality parameters (identity, potency, purity, safety) of the final live cell product. Process development activities such as extended passaging and serum reduction/elimination can facilitate the streamlining of cell manufacturing process as long as the biological functions of the product remain intact. Best practices in process development will be dependent on cell characterization; a thorough understanding of the cell-based product. Unique biological properties associated with different types of cell-based products are discussed. Cell characterization may be used as a tool for successful process development activities, which can promote a candidate cell therapy product through clinical development and ultimately to a commercialized product.

Evaluation of overnight storage conditions for autologous peripheral blood stem cell products: comparison of three different conditions

BACKGROUND

Overnight (ON) storage of peripheral blood stem cell (PBSC) occurs frequently in clinical settings. However, there are no standard guidelines for optimal storage conditions of freshly harvested PBSC. The aim of this study was to investigate the influence of storage temperatures on the quality of autologous PBSC and establish optimal storage conditions before cryopreservation.

METHODS

A retrospective analysis was performed on 260 PBSC harvests according to pre-cryopreservation conditions: immediate processing or ON storage at room temperature (RT). For direct comparison, 30 autologous PBSC products were collected prospectively and prepared under three different pre-cryopreservation conditions: immediate processing, ON storage at 4°C and ON storage at RT. The recovery of CD34(+) cells, post-thaw CFU-GM count and viability were analysed.

RESULTS

Retrospective analysis revealed that post-thaw CFU-GM count was significantly lower when PBSC were stored ON at RT compared to when immediately processed (136·4 vs. 409·6/μl). Prospective analysis showed a mean recovery of CD34(+) cells of 65·5 ± 25·1%, 70·5 ± 27·4% and 35·9 ± 25·1% for immediate processing, ON storage at 4°C and ON storage at RT, respectively. Similarly, mean viability and CFU-GM counts were significantly reduced when stored ON at RT compared to when immediately processed or stored ON at 4°C (60·4 ± 25·6 vs. 84·1 ± 12·9 vs. 82·7 ± 12·6%, 15·7 ± 25·7 vs. 398·5 ± 906·2 vs. 350·0 ± 847·9/μl, respectively).

CONCLUSIONS

ON storage of autologous PBSC at RT significantly decreased the quality of HPCs. These data indicate that ON storage of autologous PBSC at 4°C would be the most reasonable approach for maintaining the quality of HPCs when immediate processing is not possible.

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.

A Bayesian adjustment for multiplicative measurement errors for a calibration problem with application to a stem cell study

We develop a Bayesian approach to a calibration problem with one interested covariate subject to multiplicative measurement errors. Our work is motivated by a stem cell study with the objective of establishing the recommended minimum doses for stem cell engraftment after a blood transplant. When determining a safe stem cell dose based on the prefreeze samples, the postcryopreservation recovery rate enters in the model as a multiplicative measurement error term, as shown in the model. We examine the impact of ignoring measurement errors in terms of asymptotic bias in the regression coefficient. According to the general structure of data available in practice, we propose a two-stage Bayesian method to perform model estimation via R2WinBUGS (Sturtz, Ligges, and Gelman, 2005, Journal of Statistical Software 12, 1-16). We illustrate this method by the aforementioned motivating example. The results of this study allow routine peripheral blood stem cell processing laboratories to establish recommended minimum stem cell doses for transplant and develop a systematic approach for further deciding whether the postthaw analysis is warranted.

Carbohydrate-mediated inhibition of ice recrystallization in cryopreserved human umbilical cord blood

Cryopreservation of human umbilical cord blood (UCB) typically involves the cryoprotectant dimethylsulfoxide (DMSO), however, infusional toxicity and reductions in cell viability remain a concern. Ice recrystallization (IR) is an important source of cryopreservation-induced cellular injury and limits the stem cell dose in UCB units. Carbohydrates have wide-ranging intrinsic IR inhibition (IRI) activity related to structural properties. We investigated the impact of carbohydrate IRI on cell viability, induction of apoptosis and hematopoietic progenitor function in cryopreserved UCB. Mononuclear cells (MNCs) from UCB were cryopreserved in storage media containing specific carbohydrates (200mM) and compared to 5% DMSO. Samples were analyzed under conditions of high IR ('slow' thaw) and low IR ('fast' thaw). Thawed samples were analyzed for viability and apoptosis by flow cytometry and hematopoietic function using colony-forming unit (CFU) assays. IRI of carbohydrate solutions was determined using the 'splat cooling' assay. Greater IRI capacity of carbohydrates correlated with increased yield of viable MNCs (r(2)=0.92, p=0.004) and CD34(+) cells (r(2)=0.96, p=0.019) after thawing under conditions of high IR. The correlations were less apparent under conditions of low IR. Carbohydrates with greater IRI modulate the induction of early apoptosis during thawing, especially in CD34+ cells (r(2)=0.96, p=0.0001) as compared to total mononuclear cells (p=0.006), and preserve CFU capacity in vitro (r(2)=0.92, p=<0.0001). Our results suggest that carbohydrates with potent IRI increase the yield of non-apoptotic and functional hematopoietic progenitors and provide a foundation for the development of novel synthetic carbohydrates with enhanced IRI properties to improve cryopreservation of UCB.

The effect of CD34 count and clonogenic potential of hematopoietic stem cells on engraftment

In this study we have determined that the number of the CD34 (+) cells in the grafts that were infused to 48 patients who underwent autologous and allogeneic hematopoietic cell transplantation and evaluated the number of colony forming units in vitro. Our aim was to determine whether there is a relation between these cell counts and post transplantation engraftment kinetics. A negative correlation was detected (p<0.05) between the CD34 (+) cell count and all colony forming units. A correlation between the CD34 (+) cell count and the kinetics of engraftment could not be demonstrated. In the autologous group, only a weak negative correlation between the CFU-GEMM and neutrophil engraftment was detected. In the allogeneic group, colony forming units did not determine the engraftment.

CXCR4 expression on transplanted peripheral blood CD34+ cells: relationship to engraftment after autologous transplantation in a cohort of multiple myeloma patients

Expression of the chemokine receptor CXCR4 by haematopoietic stem cells (HSCs) is believed to influence the process of these cells 'homing' back to the bone marrow post-transplantation, in response to the stromal cell-derived factor-1 gradient, followed by engraftment. The primary aim of this retrospective study was to compare reinfused CD34(+) cell dose, assessed from the fresh collection, with the post-thaw viable (v) CD34(+) and vCD34/CXCR4(+) dual positive cell dose as predictors of haematopoietic recovery in multiple myeloma patients undergoing autologous stem cell transplantation. Cryopreserved samples from stem cell collections of 27 myeloma patients were analysed for CD34 and CXCR4 expression and times to haematological engraftment measured. Dosage of transplanted vCD34(+) cells was on average 79% of the original calculation from the fresh collection bag (range 29-98%). The median percentage of vCD34+ cells co-expressing CXCR4 was 37% (3.7-97%). Surface expression of CXCR4 by thawed vCD34(+) cells was closely correlated to complementary DNA levels. The median dose of CD34/CXCR4(+) cells in the autografts was 1.2 × 10(6)/kg (0.2-3.0 × 10(6)/kg) compared with 3.3 × 10(6)/kg for transplanted vCD34(+) cells (1.2-5.5 × 10(6)/kg). Both CD34 and vCD34 doses correlated with neutrophil engraftment (p < 0.005) although vCD34/CXCR4(+) dose did not. However, patients given a higher dose of CD34/CXCR4(+) cells (≥1.75 × 10(6)/kg) showed a faster time to platelet recovery (p < 0.05) than those given a lower dose (≤0.42 × 10(6)/kg). These results warrant further study of CD34/CXCR4 expression by mobilised HSCs and the relationship to platelet recovery post-transplantation on a larger cohort of patients.

[Quality control of defrosted cord blood units: results from an inter-laboratory study]

PURPOSE

Today, haematopoietic stem cell graft from placental blood concerns more than 15 % of allogeneic grafts. An inter-laboratory study of the quality control of defrosted cord blood units has been coordinated by the French society for cell and tissue bioengineering (SFBCT), with the cord blood bank of Bourgogne Franche-Comté and controlled by the French health products safety agency (Afssaps). The aim of this study is to ensure the inter-laboratory reproducibility of the quality controls practised by the banks during defrosting. The cellular outputs were analyzed according to the defrosting techniques, according to the method used in flow cytometry: single-platform (SP) versus double-platform (DP), or the product nature, i.e. in total blood or miniaturized.

METHODS

Forty-two units of placental blood (USP), which were out of range were provided for defrosting to 14 participating sites. USP were defrosted and controlled according to the procedures of each bank. Once the USP is defrosted, a part of the product was controlled by the site and the other part by Afssaps. Following controls were carried out: numeration of the total nucleated cells (TNC) and of CD34+ cells (made by a SP method in Afssaps) and functional assay.

RESULTS

Concerning TNC, the defrosting sites obtained a cellular output of 94 %+/-28 in day 0 compared with an output of 72 %+/-24 in Afssaps showing a rather good stability of the USP transmitted with an average deviation of 23 %+/-22. The freezing process with or without reduction of volume does not affect this variation. Concerning the numeration of CD34+ cells, the average deviation between the participating sites and Afssaps was 29 %+/-23 compared with 21 %+/-16 for the sites using a SP method against 47 %+/-25 for those using a DP method. The CD34+ outputs are equal to 82 % +/- 60 in day 0 for the participating sites against 52 %+/-20 for Afssaps. For the sites using a DP method, it is stressed that this output is particularly high with a rate of 126 %+/-90 (n=15) whereas it is 62 %+/-20 (n=32) for the sites using a SP method.

CONCLUSION

These results underline a good stability of viable CD34+ cells and a greater reliability of the SP methods for the CD34+ cell numeration for these defrosted USP. Lastly, the results of the functional assay regarding the average clonogenicities (equal to 15 %) reinforce the conclusions on the quality of the defrosted products.

Intracellular ice formation in confluent monolayers of human dental stem cells and membrane damage

Dental pulp stem cells (DPSCs) are of interest to researchers and clinicians due to their ability to differentiate into various tissue types and potential uses in cell-mediated therapies and tissue engineering. Currently DPSCs are cryopreserved in suspension using Me(2)SO. However, preservation as two and three dimensional constructs, along with the elimination of toxic Me(2)SO, may be required. It was shown that intracellular ice formation (IIF), lethal to cells in suspensions, may be innocuous in cell monolayers due to ice propagation between cells through gap junctions that results in improved post-thaw recovery. We hypothesized that innocuous IIF protects confluent DPSC monolayers against injury during cryopreservation. The objective was to examine the effects of IIF on post-thaw viability of both confluent monolayers and suspensions of DPSCs. Confluent DPSC monolayers were assessed for the expression of gap junction protein Connexin-43. IIF was induced on the cryostage and in the methanol bath at different subzero temperatures. Membrane integrity and colony-forming ability were assessed post-thaw. Confluent DPSC monolayers expressed Connexin-43. In cell suspensions, 85.9+/-1.7% of cells were damaged after 100% IIF. In cell monolayers, after 100% IIF, only 25.5+/-5.5% and 14.8+/-3.3% of cells were damaged on the cryostage and in the methanol bath respectively. However, DPSC monolayers exposed to 100% IIF showed no colony-forming ability. We conclude that confluent monolayers of DPSCs express the gap junction-forming protein Connexin-43 and upon IIF retain membrane integrity, however lose the ability to proliferate.

Improved post-thaw recovery of peripheral blood stem/progenitor cells using a novel intracellular-like cryopreservation solution

BACKGROUND AIMS

Peripheral blood stem cells (PBSC) have become the preferred stem cell source for autologous hematopoietic transplantation. A critical aspect of this treatment modality is cryopreservation of the stem cell products, which permits temporal separation of the PBSC mobilization/collection phase from the subsequent high-dose therapy. While controlled rate-freezing and liquid nitrogen storage have become 'routine' practice in many cell-processing facilities, there is clearly room for improvement as current cryopreservation media formulations still result in significant loss and damage to the stem/progenitor cell populations essential for engraftment, and can also expose the patients to relatively undefined serum components and larger volumes of dimethylsulfoxide (DMSO) that can contribute to the morbidity and mortality of the transplant therapy.

METHODS

This study compared cryopreservation of PBSC in a novel intracellular-like, fully defined, serum- and protein-free preservation solution, CryoStor (BioLife Solutions Inc.), with a standard formulation used by the Fred Hutchinson Cancer Research Center (FHCRC). Briefly, human PBSC apheresis specimens were collected and 5 x 10(7) cells/1 mL sample vial were prepared for cryopreservation in the following solutions: (a) FHCRC standard, Normosol-R, 5% human serum albumin (HAS) and 10% DMSO; and (b) CryoStor CS10 (final diluted concentration of 5% DMSO). A standard controlled-rate freezing program was employed, and frozen vials were stored in the vapor phase of a liquid nitrogen freezer for a minimum of 1 week. Vials were then thawed and evaluated for total nucleated cell count (TNC), viability, CD34 and granulocytes by flow cytometry, along with colony-forming activity in methylcellulose.

RESULTS

The PBSC samples frozen in CryoStor CS10 yielded significantly improved post-thaw recoveries for total viable CD34(+), colony-forming units (CFU) and granulocytes. Specifically, relative to the FHCRC standard formulation, cryopreservation with CS10 resulted in an average 1.8-fold increased recovery of viable CD34(+) cells (P=0.005), a 1.5-fold increase in CFU-granulocyte-macrophage (GM) numbers (P=0.030) and a 2.3-fold increase in granulocyte recovery (P=0.045).

CONCLUSIONS

This study indicates that use of CryoStor for cryopreservation can yield significantly improved recovery and in vitro functionality of stem/progenitor cells in PBSC products. In addition, it is important to note that these improved recoveries were obtained while not introducing any extra serum or serum-derived proteins, and reducing the final concentration/volume of DMSO by half. Further in vitro and in vivo studies are clearly necessary; however, these findings imply use of CryoStor for cryopreservation could result in improved engraftment for those patients with a lower content of CD34(+) cells in their PBSC collections, along with reducing the requirement for additional apheresis collections and decreasing the risk of adverse infusion reactions associated with higher exposure to DMSO.

Cryopreservation of hematopoietic stem/progenitor cells for therapeutic use

To date, more than 25,000 hematopoietic transplants have been carried out across Europe for hematological disorders, the majority being for hematological malignancies. At least 70% of these are autologous transplants, the remaining 30% being allogeneic, which are sourced from related (70% of the allogeneic) or unrelated donors. Peripheral blood mobilized with granulocyte colony stimulating factor is the major source of stem cells for transplantation, being used in approx 95% of autologous transplants and in approx 65% of allogeneic transplants. Other cell sources used for transplantation are bone marrow and umbilical cord blood. One crucial advance in the treatment of these disorders has been the development of the ability to cryopreserve hematopoietic stem cells for future transplantation. For bone marrow and mobilized peripheral blood, the majority of cryopreserved harvests come from autologous collections that are stored prior to a planned infusion following further treatment of the patient or at the time of a subsequent relapse. Other autologous harvests are stored as backup or "rainy day" harvests, the former specifically being intended to rescue patients who develop graft failure following an allogeneic transplant or who may require this transplant at a later date. Allogeneic bone marrow and mobilized peripheral blood are less often cryopreserved than autologous harvests. This is in contrast to umbilical cord blood that may be banked for directed or sibling (related) hematopoietic stem cell transplants, for allogeneic unrelated donations, and for autologous donations. Allogeneic unrelated donations are of particular use for providing a source of hematopoietic stem cells for ethnic minorities, patients with rare human leukocyte antigen types, or where the patient urgently requires a transplant and cannot wait for the weeks to months required to prepare a bone marrow donor. There are currently more than 200,000 banked umbilical cord blood units registered with the Bone Marrow Donors Worldwide registry. In this chapter, we describe several protocols that we have used to cryopreserve these different sources of hematopoietic stem/progenitor cells, keeping in mind that the protocols may vary among transplant processing centers.

Post-thaw viable CD34(+) cell count is a valuable predictor of haematopoietic stem cell engraftment in autologous peripheral blood stem cell transplantation

BACKGROUND AND OBJECTIVES

In peripheral blood stem cell transplantation, the number of CD34(+) cells infused is considered a predictor of haematopoietic engraftment. However, the currently accepted minimal threshold of CD34(+) cells/kg was determined by counting CD34(+) cells before freezing, and the loss of viable CD34(+) cells during freezing, cryopreservation or thawing prior to reinfusion has not been assessed.

MATERIALS AND METHODS

Total and viable CD34(+) cells were quantified using single platform flow cytometry and viability dye, 7-amino actinomycin D (7-ADD), at the time of collection and prior to reinfusion in 46 peripheral haematopoietic stem cell grafts from 36 patients. The time to engraftment of neutrophil and platelet was assessed by routine peripheral blood cell counts performed daily.

RESULTS

The median number of viable CD34(+) cells harvested was 3.6 x 10(6)/kg (range 0.05-21.2), and the median viability was 98% (range 70-100%) before freezing. After thawing, the median number of viable CD34(+) cells was reduced to 2.2 x 10(6)/kg (range 0.04-14.8) and the median viability was reduced to 71% (range 31-89%). The number of viable CD34(+) cells/kg before freezing and after thawing significantly correlated with engraftment of neutrophils (P < 0.0001 both) and platelets (P = 0.007 and 0.006, respectively). Although the minimum dose for engraftment (2.0 x 10(6) CD34(+) cells/kg) was harvested in 37 of 46 cases (85%), only 25 cases (54%) met this threshold at the time of reinfusion. For platelet engraftment, determination of viable CD34(+) cells prior to reinfusion was more important than enumeration at the time of collection.

CONCLUSION

Quantification of post-thaw viable CD34(+) cells better represents the actual composition of the graft and may be a more accurate predictor of haematopoietic engraftment than post-thaw total CD34(+) cell counts, or prefreeze determinations, especially for platelet engraftment. It is necessary to develop good quality controls for freezing and thawing procedures to minimize variance in cell viability.

Cryopreservation of hematopoietic stem cells

Stem cell transplantation represents a critical approach for the treatment of many malignant and non-malignant diseases. The foundation for these approaches is the ability to cryopreserve marrow cells for future use. This technique is routinely employed in all autologous settings and is critical for cord blood transplantation. A variety of cryopreservatives have been used with multiple freezing and thawing techniques as outlined in the later chapters. Freezing efficiency has been proven repeatedly and the ability of long-term stored marrow to repopulate has been established. Standard approaches outlined here are used in many labs as the field continues to evolve.

Viable CD34+/CD133+ blood progenitor cell dose as a predictor of haematopoietic engraftment in multiple myeloma patients undergoing autologous peripheral blood stem cell transplantation

Both CD34 (cluster of differentiation 34) and the more recently described CD133 are markers of primitive stem cells with haematopoietic repopulating ability. Most transplanting centres use a minimum number of CD34+ cells as the requirement for a transplant and consider this a predictor of haematopoietic engraftment. However, transplanted CD34+ cell dose does not always give a close correlation with time to engraftment nor explain delayed engraftment in some patients. We have retrospectively evaluated the potential of measuring viable CD133+ cell numbers in the autograft as an alternative predictor of haematological engraftment after autologous stem-cell transplantation in a cohort of patients with multiple myeloma (MM). We found an average 32% loss of viability of CD34+ cells in the post-thaw sample compared with the fresh sample. Of the original estimated CD34+ cell numbers transplanted per kg, 43% of the thawed samples were double positive for CD34+/CD133+. In this patient group, the CD34+/CD133+ subset gave the closest statistical correlation with time to neutrophil engraftment (p < 0.05), particularly for patients given above median (1.8 x 10(6)/kg) dose of the double-positive cells. The CD34+/CD133+ population was the only parameter to give a significant correlation with white cell engraftment in this patient cohort (p < 0.05). There was no significant correlation between CD34+, viable CD34+ or viable CD34+/CD133+ cells/kilogram with platelet engraftment. Determination of viable CD34+/CD133+ progenitor cell dose in the autograft may be a useful tool to predict neutrophil recovery after autologous transplantation than conventional assessment of CD34+ numbers. These results warrant further investigation of the role of CD133 in haematopoietic engraftment.