Avoiding room temperature storage and delayed cryopreservation provide better postthaw potency in hematopoietic progenitor cell grafts

A machine-learning model that incorporates CD45 surface expression predicts hematopoietic progenitor cell recovery after freeze-thaw

BACKGROUND AIMS

Sufficient doses of viable CD34+ (vCD34) hematopoietic progenitor cells (HPCs) are crucial for engraftment. Additional-day apheresis collections can compensate for potential loss during cryopreservation but incur high cost and additional risk. To aid predicting such losses for clinical decision support, we developed a machine-learning model using variables obtainable on the day of collection.

METHODS

In total, 370 consecutive autologous HPCs, apheresis-collected since 2014 at the Children's Hospital of Philadelphia, were retrospectively reviewed. Flow cytometry was used to assess vCD34% on fresh products and thawed quality control vials. The ratio of vCD34% thawed to fresh, which we call "post-thaw index," was used as an outcome measure, with a "poor" post-thaw index defined as <70%. HPC CD45 normalized mean fluorescence intensity (MFI) was calculated by dividing CD45 MFI of HPCs to the CD45 MFI of lymphocytes in the same sample. We trained XGBoost, k-nearest neighbor and random forest models for the prediction and calibrated the best model to minimize falsely-reassuring predictions.

RESULTS

In total, 63 of 370 (17%) products had a poor post-thaw index. The best model was XGBoost, with an area under the receiver operator curve of 0.83 evaluated on an independent test data set. The most important predictor for a poor post-thaw index was the HPC CD45 normalized MFI. Transplants after 2015, based on the lower of the two vCD34% values, showed faster engraftment than older transplants, which were based on fresh vCD34% only (average 10.6 vs 11.7 days, P = 0.0006).

CONCLUSIONS

Transplants taking into account post-thaw vCD34% improved engraftment time in our patients; however, it came at the cost of unnecessary multi-day collections. The results from applying our predictive algorithm retrospectively to our data suggest that more than one-third of additional-day collections could have been avoided. Our investigation also identified CD45 nMFI as a novel marker for assessing HPC health post-thaw.

Cryopreservation: A Comprehensive Overview, Challenges, and Future Perspectives

Cryopreservation is the most prevalent method of long-term cell preservation. Effective cell cryopreservation depends on freezing, adequate storage, and correct thawing techniques. Recent advances in cryopreservation techniques minimize the cellular damage which occurs while processing samples. This article focuses on the fundamentals of cryopreservation techniques and how they can be implemented in a variety of clinical settings. The article presents a brief description of each of the standard cryopreservation procedures, such as slow freezing and vitrification. Alongside that, the membrane permeating and nonpermeating cryoprotectants are briefly discussed, along with current advancements in the field of cryopreservation and variables influencing the cryopreservation process. The diminution of cryoinjury incurred by the cell via the resuscitation process will also be highlighted. In the end application of cryopreservation techniques in many fields, with a special emphasis on stem cell preservation techniques and current advancements presented. Furthermore, the challenges while implementing cryopreservation and the futuristic scope of the fields are illustrated herein. The content of this review sheds light on various ways to enhance the output of the cell preservation process and minimize cryoinjury while improving cell revival.

Extracellular Matrix-Mimetic Peptide Scaffolds Prolonged the Hypothermic Preservation of Stem Cells for Storage and Transportation

Encouraging advances in both regenerative medicine and tissue engineering with stem cells require a short-term preservation protocol to provide enough time for quality control or the transportation of cell products from manufacturing facilities to clinical destinations. The hypothermic preservation of stem cells under refrigerated conditions (2-8 °C) in their specific culture medium provides an alternative and low-cost method for cryopreservation or commercial preservation fluid for short-term storage. However, most stem cells are vulnerable to hypothermia, which might result in cell damage from the cooling process and the lack of extracellular matrix (ECM). Herein, we report a peptide scaffold cell-culture-medium additive for mimicking in vivo ECM to enhance the storage efficiency of mesenchymal stem cells (MSCs) under hypothermic preservation. Peptide scaffolds exhibit protective effects against hypothermic injury by maintaining the viability, proliferation, migration, and differentiation capabilities of cells. The mechanistic study showed that the peptide scaffold was conducive to maintain mitochondrial function by retaining mitochondrial respiration, mitochondrial membrane potential (ΔΨm), and mass to alleviate intracellular and mitochondrial reactive oxygen species (ROS) production. Moreover, the peptide scaffold also prolonged the survival and retained the multipotency of hematopoietic stem and progenitor cells (HSPCs) under hypothermic conditions. In conclusion, these results demonstrate a feasible and convenient preservation system for stem cells that has the potential to promote the clinical application of hematopoietic stem cell therapy.

Long-term and short-term preservation strategies for tissue engineering and regenerative medicine products: state of the art and emerging trends

There is an ever-growing need of human tissues and organs for transplantation. However, the availability of such tissues and organs is insufficient by a large margin, which is a huge medical and societal problem. Tissue engineering and regenerative medicine (TERM) represent potential solutions to this issue and have therefore been attracting increased interest from researchers and clinicians alike. But the successful large-scale clinical deployment of TERM products critically depends on the development of efficient preservation methodologies. The existing preservation approaches such as slow freezing, vitrification, dry state preservation, and hypothermic and normothermic storage all have issues that somehow limit the biomedical applications of TERM products. In this review, the principles and application of these approaches will be summarized, highlighting their advantages and limitations in the context of TERM products preservation.

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.

The wider perspective: cord blood banks and their future prospects

Over the past three decades, cord blood transplantation (CBT) has established its role as an alternative allograft stem cell source. But the future of stored CB units should be to extend their use in updated transplant approaches and develop new CB applications. Thus, CBT will require a coordinated, multicentric, review of transplantation methods and an upgrade and realignment of banking resources and operations. Significant improvements have already been proposed to support the clinical perspective including definition of the cellular threshold for engraftment, development of transplantation methods for adult patients, engraftment acceleration with single cell expansion and homing technologies, personalised protocols to improve efficacy, use of adoptive cell therapy to mitigate delayed immune reconstitution, and further enhancement of the graft-versus-leukaemia effect using advanced therapies. The role of CB banks in improving transplantation results are also critical by optimizing the collection, processing, storage and characterization of CB units, and improving reproducibility, efficiency and cost of banking. But future developments beyond transplantation are needed. This implies the extension from transplantation banks to banks that support cell therapy, regenerative medicine and specialized transfusion medicine. This new "CB banking 2.0" concept will require promotion of international scientific and technical collaborations between bank specialists, clinical investigators and transplant physicians.

Influence of laboratory procedures on postthawing cell viability and hematopoietic engraftment after autologous peripheral blood stem cell transplantation

BACKGROUND

The kinetics of hematopoietic recovery after autologous stem cell transplantation (ASCT) may be affected by laboratory procedures. The aim of this study was to evaluate the influence of characteristics of the cryopreserved units of peripheral blood stem cells (PBSC) on postthawing cell viability and engraftment outcomes after ASCT.

STUDY DESIGN AND METHODS

This was a retrospective cohort study including individuals referred for ASCT. Cryopreservation was conducted at a single processing facility between 2014 and 2019, and patients received clinical care at six transplant centers. Covariates and outcome data were retrieved from participants' records.

RESULTS

The study population comprised 619 patients (345 [55.7%] male). Median age was 53 years. Multiple myeloma was the most common diagnosis (62.7%). Higher preapheresis CD34+ cell count, lower nucleated cell (NC) concentration per cryobag, and composition of the cryoprotectant solution (5% dimethyl sulfoxide [DMSO] and 6% hydroxyethyl starch) were statistically significantly associated with higher postthawing cell viability. The linear regression model for time to neutrophil and platelet engraftment included the infused CD34+ cell dose and the composition of the cryoprotectant solution. Patients who had PBSC cryopreserved using 10% DMSO solution presented six times higher odds (odds ratio [OR] = 6.9; 95% confidence interval [CI]: 2.2-21.1; p = .001) of delayed neutrophil engraftment (>14 days) and two times higher odds (OR = 2.3, 95%CI: 1.4-3.7; p = .001) of prolonged hospitalization (>18 days).

DISCUSSION

The study showed that mobilization efficacy, NC concentration, and the composition of the cryoprotectant solution significantly affected postthawing cell viability. In addition, the composition of the cryoprotectant solution significantly impacted engraftment outcomes and time of hospitalization after ASCT.

Multi-laboratory assay for harmonization of enumeration of viable CD34+ and CD45+ cells in frozen cord blood units

BACKGROUND AIMS

In 2016, specifications for both pre-cryopreserved and post-thawed cord blood were defined in the sixth edition of NetCord Foundation for the Accreditation of Cellular Therapy (FACT) Standards for Cord Blood Banks. However, for several experts, harmonization regarding flow cytometry analysis performed on post-thawed samples is still a concern. A multicenter study led by Héma-Québec aimed to provide scientific data to support the cord blood accreditation bodies such as NetCord FACT in the revision of standards.

METHODS

Twelve cord blood units were processed for plasma and red cell reduction following standard operating procedures. Cord blood unit aliquots were shipped to eight participating centers under cryogenic conditions for analysis before and after standardization of protocol. Repeatability of stem cell count, measured pre- and post-intervention with the centers, was estimated using multilevel linear regression models with a heterogeneous compound symmetry correlation structure among repeated measures.

RESULTS

Excellent inter-center repeatability was reported by each participant regarding the viable CD34+ cells concentration, and a successful improvement effect of protocol standardization was also observed. However, we observed that better control over the critical parameters of the protocol did not have a significant effect on improving homogeneity in the enumeration of CD45+ cells.

CONCLUSIONS

The current practice in cord blood selection should now also consider relying on post-thaw CD34+ concentration, providing that all cord blood banks or outsourcing laboratories in charge of the analysis of post-thaw CB samples take into account the consensual recommendations provided in this work and adhere to a good-quality management system.

Umbilical cord blood quality and quantity: Collection up to transplantation

Umbilical cord blood (UCB) is an attractive source of hematopoietic stem cells for transplantation in some blood disorders. One of the major factors that influence on transplantation fate is cord blood (CB) cell count, in addition to human leukocyte antigen similarity and CD34+ cell number. Here, we review the factors that could effect on quality and quantity of CBUs. Relevant English-language literatures were searched and retrieved from PubMed using the terms: CB, quality, collection, and transplantation. The numbers of total nucleated cells (TNCs) and CD34+ cells are good indicators of CB quality because they have been associated with engraftment; thereby, whatever the TNCs in a CB unit (CBU) are higher, more likely they led to successful engraftment. Many factors influence the quantity and quality of UCB units that collect after delivery. Some parameters are not in our hands, such as maternal and infant factors, and hence, we cannot change these. However, some other factors are in our authority, such as mode of collection, type and amount of anticoagulant, and time and temperature during collection to postthaw CBUs and freeze-and-thaw procedures. By optimizing the CB collection, we can improve the quantity and quality of UCB for storage and increase the likelihood of its use for transplantation.

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

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

Leukapheresis cell concentration adjustment required for a successful recovery of HSC after cryopreservation

The recovering of an adequate number of hematopoietic stem cells after cryopreservation is considered pivotal for successful transplantation. Various factors could influence the recovery of HSC following processing and cryopreservation. Therefore, leukapheresis product from thirty patients was cryopreserved in 10% DMSO in cryopreservation bags for their autologous bone marrow transplantation, and 2 ml were cryopreserved in cryovials for post-thaw viability assessment by flow cytometry. The percentage of viable HSCs recovered post-cryopreservation in leukapheresis product was significantly influenced by the concentration of the total nucleated cells cryopreserved per volume. Patients receiving a higher rate of viable HSCs resulted in earlier engraftment of both neutrophils and platelets, so they have been discharged earlier from the hospital. Furthermore, Storage temperature and duration played a role in the recovery of these cells and for the support of the findings, age of the patient at the time of collection did not show any impact on the recovery of this HSC post-cryopreservation. In conclusion, various influencing factors must be taken into consideration during the cryopreservation of HSCs, especially for poor mobilizing patients with a low number of collected hematopoietic stem cells.

Measurable residual disease in acute myeloid leukemia using flow cytometry: approaches for harmonization/standardization

Introduction: Measurable residual disease (MRD) in acute myeloid leukemia (AML) is a rapidly evolving area with many institutes embarking on it, both in academic and pharmaceutical settings. However, there is a multitude of approaches to design, perform, and report flow cytometric MRD. Together with the long-term experience needed, this makes flow cytometric MRD in AML nonstandardized and time-consuming. Areas covered: This paper briefly summarizes critical issues, like sample preparation and transport, markers and fluorochromes of choice, but in particular focuses on the main issues, which includes specificity and sensitivity, hereby providing a new model that may circumvent the main disadvantages of the present approaches. New approaches that may add to the value of flow cytometric MRD includes assessment of leukemia stem cells, MRD in peripheral blood, and approaches to use multidimensional image analysis. Expert commentary: MRD in AML requires standardization/harmonization on many aspects, for which the present paper offers possible guidelines.

Cryopreservation of Hematopoietic Stem Cells: Emerging Assays, Cryoprotectant Agents, and Technology to Improve Outcomes

Hematopoietic stem cell (HSC) therapy is widely used to treat a growing number of hematological and non-hematological diseases. Cryopreservation of HSCs allows for cells to be transported from the site of processing to the site of clinical use, creates a larger window of time in which cells can be administered to patients, and allows sufficient time for quality control and regulatory testing. Currently, HSCs and other cell therapies conform to the same cryopreservation techniques as cells used for research purposes: cells are cryopreserved in dimethyl sulfoxide (DMSO) at a slow cooling rate. As a result, HSC therapy can result in numerous adverse symptoms in patients due to the infusion of DMSO. Efforts are being made to improve the cryopreservation of HSCs for clinical use. This review discusses advances in the cryopreservation of HSCs from 2007 to the present. The preclinical development of new cryoprotectants and new technology to eliminate cryoprotectants after thawing are discussed in detail. Additional cryopreservation considerations are included, such as cooling rate, storage temperature, and cell concentration. Preclinical cell assessment and quality control are discussed, as well as clinical studies from the past decade that focus on new cryopreservation protocols to improve patient outcomes.

Assessment of stability of CD34+ cell products enriched by immunoselection from peripheral blood mononuclear cells during refrigerated storage

Durable engraftment of transplanted CD34+ cells largely depends on the quality of the cell product. Limited data are currently available about extended storage of immunoselected CD34+ cells. The aim of our study was to assess the stability of CD34+ cell product with the cells stored in high concentration (80×10⁶ in 6mL) in small bags intended for cell implantation. Cell products were prepared by leukapheresis and immunoselection (Clinimacs^plus procedure) from 13 patients with chronic dilated cardiomyopathy. CD34+ cell products were stored at 2-8°C and analyzed at time 0 (fresh products), 24, 48h, 4 and 6 days. Product viability, absolute number of viable CD34+ cells and apoptosis were determined by flow cytometry. Microbiological contamination of the cell products was tested by BACTEC system. The mean viability of CD34+ cells decreased by 2.7% within 24h, by 13.4% within 48h and by 37.5% within 6 days. The mean recovery of viable CD34+ cells was 91.1%, 74.8%, 66.3% and 56.2% at 24, 48h, 4 and 6 days, respectively. The mean fraction of early apoptotic cells in fresh and stored products was 4.9±3.5% at 0h, 5.9±3.8% at 24h, 4.2±3.1% at 48h, 6.3±2.6% at 4 days and 9.3±4.6% at 6 days. All products were negative for microbial contamination.

The influence of temperature treatment before cryopreservation on the viability and potency of cryopreserved and thawed CD34+ and CD45+ cord blood cells

BACKGROUND

Hematopoietic stem cell (HSC) viability and potency is crucial for qualified cord blood (CB) transplants. This study analyzes time and temperature condition before cryopreservation for the viability of CD34⁺/CD45⁺ cells after cryopreservation.

METHODS

Cell viabilities were determined by antibody co-staining with 7-aminoactinomycin D detecting necrotic cells, and subsequent flow cytometric analysis. Additionally, Annexin V staining for determination of apoptotic cells and colony-forming unit (CFU) assays for testing functional potency of HSCs were performed.

RESULTS

For all cell types assessed (CD45⁺/CD34⁺ cells, lymphocytes and granulocytes), the highest viabilities were obtained for CB maintained at 4°C or room temperature (RT; 22 ± 4°C) and cryopreserved directly after collection. Starting material were CB units with an age of 24.7 ± 3.5 h after birth. Post-thaw CD34⁺ cell results were > 90% after temperature treatment of t = 24 h (48 h total age) and > 70% after t = 48 h (72 h total age) at 4°C (48 h, 91.4 ± 5.5%; 72 h, 75.0 ± 12.0%) and RT (48 h, 84.2 ± 9.7%; 72 h, 72.6 ± 0.6%). Viabilities for 30°C samples were < 80% after t = 24 h (48 h total age, 79.8 ± 3.1%) and < 50% after t = 48 h of treatment (72 h total age, 46.8 ± 14.3%). Regarding CFU recovery of pre-freeze (without volume reduction) and thawed CB, a trend toward the highest recoveries was observed at 4°C/RT. The difference between 4°C (77.5 ± 12.0%) and 30°C samples (53.9 ± 4.8%) was shown to be significant in post-thaw samples after t = 24 h treatment (48 h total age; P = 0.0341).

DISCUSSION

Delays between collection and cryopreservation should be minimized because increasing time reduces numbers of viable cells and CFUs before/after cryopreservation. CB units should be maintained at 4°C/RT to retain the highest possible potency of the cells after thawing.

Spheroidal formation preserves human stem cells for prolonged time under ambient conditions for facile storage and transportation

Human stem cells are vulnerable to unfavorable conditions, and their transportation relies on costly and inconvenient cryopreservation. We report here that human mesenchymal stem cells (MSC) in spheroids survived ambient conditions (AC) many days longer than in monolayer. Under AC, the viability of MSC in spheroids remained >90% even after seven days, whereas MSC in monolayer mostly died fast. AC-exposed MSC spheroids, after recovery under normal monolayer culture conditions with controlled carbon dioxide and humidity contents, resumed typical morphology and proliferation, and retained differentiating and immunosuppressive capabilities. RNA-sequencing and other assays demonstrate that reduced cell metabolism and proliferation correlates to the enhanced survival of AC-exposed MSC in spheroids versus monolayer. Moreover, AC-exposed MSC, when injected as either single cells or spheroids, retained therapeutic effects in vivo in mouse colitis models. Spheroidal formation also prolonged survival and sustained pluripotency of human embryonic stem cells kept under AC. Therefore, this work offers an alternative and relatively simple method termed spheropreservation versus the conventional method cryopreservation. It shall remarkably simplify long-distance transportation of stem cells of these and probably also other types within temperature-mild areas, and facilitate therapeutic application of MSC as spheroids without further processing.

Ex vivo virotherapy with myxoma virus does not impair hematopoietic stem and progenitor cells

BACKGROUND

Relapsing disease is a major challenge after hematopoietic cell transplantation for hematological malignancies. Myxoma virus (MYXV) is an oncolytic virus that can target and eliminate contaminating cancer cells from auto-transplant grafts. The aims of this study were to examine the impact of MYXV on normal hematopoietic stem and progenitor cells and define the optimal treatment conditions for ex vivo virotherapy.

METHODS

Bone marrow (BM) and mobilized peripheral blood stem cells (mPBSCs) from patients with hematologic malignancies were treated with MYXV at various time, temperature and incubation media conditions. Treated BM cells from healthy normal donors were evaluated using flow cytometry for MYXV infection, long-term culture-initiating cell (LTC-IC) assay and colony-forming cell (CFC) assay.

RESULTS

MYXV initiated infection in up to 45% of antigen-presenting monocytes, B cells and natural killer cells; however, these infections were uniformly aborted in >95% of all cells. Fresh graft sources showed higher levels of MYXV infection initiation than cryopreserved specimens, but in all cases less than 10% of CD34(+) cells could be infected after ex vivo MYXV treatment. MYXV did not impair LTC-IC colony numbers compared with mock treatment. CFC colony types and numbers were also not impaired by MYXV treatment. MYXV incubation time, temperature or culture media did not significantly change the percentage of infected cells, LTC-IC colony formation or CFC colony formation.

CONCLUSIONS

Human hematopoietic cells are non-permissive for MYXV. Human hematopoietic stem and progenitor cells were not infected and thus unaffected by MYXV ex vivo treatment.

Variable resistance to freezing and thawing of CD34-positive stem cells and lymphocyte subpopulations in leukapheresis products

BACKGROUND AIMS

Leukapheresis products for hematopoietic stem cell transplantation can be cryopreserved for various indications. Although it is known that CD34(+) cells tolerate cryopreservation well, a significant loss of CD3(+) cells has been observed, which has been ascribed to several factors, including transport, storage conditions and granulocyte-colony stimulating factor (G-CSF) administration.

METHODS

To assess the tolerance of CD34(+) cells and lymphocyte subpopulations for cryopreservation and thawing, the post-thaw recoveries of CD34(+) cells, CD3(+)CD4(+) cells, CD3(+)CD8(+) cells, CD19(+) cells and CD16(+)CD56(+) cells were determined in 90 cryopreserved apheresis products, among which 65 were from G-CSF-mobilized donors, and 34 from unrelated donors that underwent transport before cryopreservation at our center. A controlled rate freezer and 5% dimethyl sulfoxide were used for cryopreservation.

RESULTS

We could detect statistically significant differences for CD34(+) cell recovery (93.0 ± 20.7%) when compared to CD3(+)CD4(+) cell (83.1 ± 15.4%, P = 0.014), and CD3(+)CD8(+) cell recovery (83.3 ± 13.9%, P = 0.001). Similarly, CD19(+) cell recovery (98.6 ± 15.1%) was higher than CD3(+)CD4(+) cell (P = 2.5 × 10(-7)) and CD3(+)CD8(+) cell recovery (P = 1.2 × 10(-8)). Post-thaw recovery rates of all cell populations were not impaired in G-CSF-mobilized products compared with non-mobilized products nor in unrelated compared with related donor products.

DISCUSSION

Our data suggest a lower tolerance of CD3(+) cells for cryopreservation and demonstrate that freezing-thawing resistance thawing is cell-specific and independent from other factors that affect post-thaw recovery of cryopreserved cells. Thus, a clinical consequence may be the monitoring of post-thaw CD3(+) cell doses of cryopreserved products, such as donor lymphocyte infusions.

Liquid Storage of Hematopoietic Stem Cells Versus Proliferative Potential Colony-Forming Unit Granulocyte-Monocytes: Validation of Cell Processing

BACKGROUND

The material for transplantation must be of the highest quality. As far as we know, short-term storage is one of the crucial points of stem cell banking. According to the quality assurance system in a stem cell bank, each step of cell processing must be validated. The aim of this study was to assess the influence of short-term storage conditions into a clonogenic assay.

METHODS

Material was collected from mobilized peripheral blood by means of leukapheresis from 15 patients. Samples were stored at 4°C and 20°C; samples were evaluated on the day of leukapheresis and after 24 hours and after 48 hours of storage. The number of colony-forming unit granulocyte-monocyte (CFU-GM) precursors was analyzed with the use of in vitro culture. The material was evaluated before freezing and after thawing.

RESULTS

The average number of CFU-GM precursors in the material stored at 4°C before freezing on the day of collection was 84/10(5) nuclear cells (nc) and after 24 hours and 48 hours of storage was, respectively, 62/10(5) nc (P = .011719) and 36/10(5) nc (P = .02088). The average of the CFU-GM precursors in material stored at 20°C after 24 hours and 48 hours of storage amounted to 33/10(5) nc (P = .004439) and 2/10(5) nc (P = .00346), respectively.

CONCLUSIONS

In our study, the number of colonies of CFU-GM after 24 hours and 48 hours of storage, both at 4°C and 20°C, was significantly reduced compared with the number of colonies on the day of collection. Significantly greater numbers of CFU-GM precursors were observed in the material stored before freezing at 4°C in comparison with the material stored at 20°C.

Global Cell Proteome Profiling, Phospho-signaling and Quantitative Proteomics for Identification of New Biomarkers in Acute Myeloid Leukemia Patients

The identification of protein biomarkers for acute myeloid leukemia (AML) that could find applications in AML diagnosis and prognosis, treatment and the selection for bone marrow transplant requires substantial comparative analyses of the proteomes from AML patients. In the past years, several studies have suggested some biomarkers for AML diagnosis or AML classification using methods for sample preparation with low proteome coverage and low resolution mass spectrometers. However, most of the studies did not follow up, confirm or validate their candidates with more patient samples. Current proteomics methods, new high resolution and fast mass spectrometers allow the identification and quantification of several thousands of proteins obtained from few tens of μg of AML cell lysate. Enrichment methods for posttranslational modifications (PTM), such as phosphorylation, can isolate several thousands of site-specific phosphorylated peptides from AML patient samples, which subsequently can be quantified with high confidence in new mass spectrometers. While recent reports aiming to propose proteomic or phosphoproteomic biomarkers on the studied AML patient samples have taken advantage of the technological progress, the access to large cohorts of AML patients to sample from and the availability of appropriate control samples still remain challenging.

Quality of the hematopoietic stem cell graft affects the clinical outcome of allogeneic stem cell transplantation

BACKGROUND

In approximately two-thirds of patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) no suitable related donor can be identified but an unrelated HLA-matched donor can be found through international donor registries. HSCT grafts from unrelated donors are commonly collected at distant sites. Therefore, graft storage and transportation becomes crucial in the HSCT process. We aimed to study the impact of graft quality on clinical outcome and identify factors affecting graft quality.

STUDY DESIGN AND METHODS

We investigated the influence of graft quality on the clinical outcome in 144 HSCT patients. Graft quality was assessed by determining the viability (7-aminoactinomycin D [7AAD]) on a frozen-thawed sample from the peripheral blood stem cell (PBSC) graft.

RESULTS

Patients receiving PBSCs with inferior quality (i.e., viability < 64% in the frozen-thawed sample) more frequently developed acute graft-versus-host disease (aGVHD) Grades I to IV than patients receiving grafts with better quality (p = 0.025). The transplant-related mortality (TRM) was higher in the group receiving grafts with lower viability (p = 0.03). The viability of the frozen-thawed samples was highly variable (median, 64%; range, 24%-96%). No correlation could be observed when comparing the viability in newly arrived PBSC grafts to frozen-thawed vials. Grafts with white blood cell (WBC) count of more than 300 × 10(9) /L had lower viability than those with lower WBC counts (p < 0.001).

CONCLUSION

Graft quality affects clinical outcome. Patients receiving grafts with inferior quality had more aGVHD and higher TRM. There is a need for better analyses for assessing graft quality in routine HSCT care; analysis using 7AAD on fresh PBSC grafts is not sufficient.

Effects of tobacco smoking during pregnancy on oxidative stress in the umbilical cord and mononuclear blood cells of neonates

Background

Although cigarette smoke is known to be a complex mixture of over 4000 substances that can lead to damage through active or passive smoking, its mechanisms and biochemical consequences in pregnancy and neonates are not yet fully understood. Therefore, in the present study, we propose to study the impact of smoking during gestation on the viability of blood mononuclear cells (MNC) from umbilical cords of newborns to assess the degree of oxidative stress and cell viability. After childbirth, the cord blood and the umbilical cord were immediately collected in public hospitals in Greater Vitoria, ES, Brazil. Flow cytometry was used to analyze the cord blood followed by biochemical and histological tests to analyze possible changes in the umbilical cord.

Results

Pregnant smokers had a reduction of MNC viability from the umbilical cord (10%), an increase in the production of reactive oxygen species (ROS) and an increase in cell apoptosis (~2-fold) compared to pregnant non-smokers. In the umbilical cord, it was observed an increase of advanced oxidation protein products - AOPP (~2.5-fold) and a loss of the typical architecture and disposition of endothelial cells from the umbilical artery.

Conclusions

These data suggest that maternal cigarette smoking during pregnancy (even in small amounts) may compromise the viability of MNC cells and damage the umbilical cord structure, possibly by excessive ROS bioavailability.

Factors which can influence the quality related to cell viability of the umbilical cord blood units

Cell viability is an important indicator for the quality of umbilical cord blood (UCB) units that can influence the transplant final outcome. Thus, it is particularly important to identify the factors that may affect the cell quality during the banking process. The present study is a first attempt to correlate the impact of exogenous factors (time from collection to processing, collected UCB volume) and endogenous factors (TNCC--total nucleated cell count, CD34(+)cell count) on cell viability assessed before UCB units cryopreservation within a banking standardized process. Three thousand UCB units collected in 35 ml CPDA containing bags were processed by HES sedimentation within 48 h. TNCC, CD34(+) cell counts and total cell viability were determined after processing. Cell viability of 94.37 ± 4.67%, TNCC of 73.17 ± 36.73 × 10(7) and CD34(+)cell count of 2.61 ± 2.29 × 10(6) was obtained after processing of units with UCB collected volume of 80.23 ± 28.52 ml. A significant negative correlation was found between cell viability and the time from collection to processing (r = -0.7228; P < 0.0001). The cell viability decreasing rate of 20.54%, 15.18% and 3-10% were achieved for units with collected UCB volume <40 ml, (40-80 ml) and >80 ml, to 48 h versus 12 h. There were no differences considering cell viability for the UCB units with similar collected UCB volume that had various CD34(+)cell count or TNCC (P > 0.05). The extension of the time from collection to processing of UCB units can reduce the quality by decreasing cell viability. The cell viability decreasing rate owing to the time influence is determined by the collected UCB volume being inversely proportional to it. Endogenous factors do not affect the cell viability.

Umbilical cord blood CD34(+) stem cells and other mononuclear cell subtypes processed up to 96 h from collection and stored at room temperature maintain a satisfactory functionality for cell therapy

BACKGROUND AND OBJECTIVES

Umbilical cord blood (UCB) is a good stem cell source for cell therapy. We recently demonstrated that cord blood mononuclear cell (MNCs) subtypes were viable and functional until 96 h after collection, even stored at room temperature. Now, we analyzed the viability and functionality of the cells before and after cryopreservation.

MATERIALS AND METHODS

Twenty UCB units were analyzed at 24 and 96 h after collection, frozen for 6 months, thawed and re-evaluated. MNCs were analyzed by flow cytometry, viability by 7-AAD and clonogenic assays (CFU) were performed.

RESULTS

After 96 h of storage, no substantial loss of MNC was found (median 7.320 × 10(6 ) × 6.05 × 10(6) ). Percentage and viability CD34(+) cells, B-cell precursors and mesenchymal stem cells were not affected. However, mature B and T lymphocytes as well as granulocytes had a substantial loss. CFU growth was observed in all samples. Prefreezing storage of 96 h was associated with a relative loss of colony formation (median 12%). Postthaw, this loss had a median of 49% (24 h samples) to 56% (96 h samples).

CONCLUSION

The delay of 96 h before UCB processing is possible, without a prohibitive impairment of CD34(+) loss in number and functionality.

A novel procedure to improve functional preservation of hematopoietic stem and progenitor cells in cord blood stored at +4°c before cryopreservation

During storage and transportation of collected cord blood units (CBUs) to the bank prior to their processing and cryopreservation, it is imperative to preserve the functional capacities of a relatively small amount of cells of interest (stem and progenitor cells) which are critical for graft potency. To improve CBU storage efficiency, we conceived an approach based on the following two principles: (1) to provide a better nutritive and biochemical environment to stem and progenitor cells in CB and (2) to prevent the hyperoxygenation of these cells transferred from a low- (1.1%-4% O2 in the CB) to a high-oxygen (20%-21% O2 in atmosphere) concentration. Our hypothesis is confirmed by the functional assessment of stem cell (hematopoietic reconstitution capacity in immunodeficient mice-scid repopulating cell assay) and committed progenitor activities (capacity of in vitro colony formation and of ex vivo expansion) after the storage period with our medium (HP02) in gas-impermeable bags. This storage procedure maintains the full functional capacity of a CBU graft for 3 days with respect to day 0. Further, using this procedure, a graft stored 3 days at +4°C exhibits better functional capacities than one currently used in routine storage (CBUs stored at +4°C for 1 day in gas-permeable bags and without medium). We provided the proof of principle of our approach, developed a clinical-scale kit and performed a preclinical assay demonstrating the feasibility and efficiency of our CBU preservation protocol through all steps of preparation (volume reduction, freezing, and thawing).

Storage time affects umbilical cord blood viability

BACKGROUND

Cryopreserved umbilical cord blood (CB) is increasingly used as a cell source to reconstitute marrow in hematopoietic stem cell transplant patients. Delays in cryopreservation may adversely affect cell viability, thereby reducing their potential for engraftment after transplantation.

STUDY DESIGN AND METHODS

The impact of delayed cryopreservation for up to 3 days on the viability of both CD45+ and CD34+ cell populations in 28 CB donations with volumes of 58.40 ± 15.4 mL (range, 39.4-107.4 mL) was investigated to establish whether precryopreservation storage time could be extended from our current time of 24 to 48 hours in line with other CB banks. Viability was assessed on 3 consecutive days, both before and after cryopreservation, by flow cytometry using 7-aminoactinomycin D (7-AAD) and annexin V methods.

RESULTS

The results using 7-AAD and annexin V indicated the viability of CD34+ cells before cryopreservation remained high (>92.33 ± 4.11%) over 3 days, whereas the viability of CD45+ cells decreased from 86.36 ± 4.97% to 66.24 ± 7.78% (p < 0.0001) by Day 3. Storage time significantly affected the viability of CD34+ cells after cryopreservation. Using 7-AAD, the mean CD34+ cell viability decreased by approximately 5% per extra day in storage from 84.30 ± 6.27% on Day 1 to 79.01 ± 7.44% (p < 0.0057) on Day 2 and to 73.95 ± 7.54% (p < 0.0001) on Day 3. With annexin V staining CD34+ cell viability fell by approximately 7% per extra day in storage from 77.17 ± 8.47% on Day 1 to 69.56 ± 13.30% (p < 0.0194) on Day 2 and to 62.89 ± 15.22% (p < 0.0002) on Day 3.

CONCLUSION

This study demonstrates that extended precryopreservation storage adversely affects viability and should be avoided.

Effects of storage temperature on hematopoietic stability and microbial safety of BM aspirates

Bone marrow (BM) remains a common source for hematopoietic SCT. Due to the transcutaneous approach, contamination with skin bacteria is common. The delay between harvest and transfusion can be considerable, potentially allowing for bacterial proliferation. The optimal transportation temperature, specifically with respect to bacterial growth and consequences thereof for hematopoietic quality, remain undefined. For 72 h, 66 individual BM samples, non-spiked/spiked with different bacteria, stored at 20-24 °C room temperature (RT) or 3-5 °C (cold), were serially analyzed for hematopoietic quality and microbial burden. Under most conditions, hematopoietic quality of BM was equal or better at RT: Typical BM contaminants (P. acnes and S. epidermidis) and E. coli were killed or bacterial proliferation was arrested at RT; hematopoietic quality was not impacted by the contamination. However, several pathogenic bacteria not typically found in BM (S. aureus and K. pneumoniae) proliferated dramatically at RT and impaired hematopoietic quality. Bacterial proliferation was arrested in the cold. The overwhelming majority of BM samples, that is, those that are sterile or contaminated only with skin commensals, will benefit from transportation at RT. Those bacteria that proliferate and perturb hematopoietic quality are not typically found in BM. Our data support recommendations for RT transportation and storage of BM.