Pre infusion, post thaw CD34+ peripheral blood stem cell enumeration as a predictor of haematopoietic engraftment in autologous haematopoietic cell transplantation

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.

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.

Determination of the relationship between CD34+ stem cell amount and DMSO in hematopoetic stem cell transplantation

It is important to calculate the CD34+ stem cell (SC) count at the right time in patients with hematological malignancies who will undergo Hematopoietic Stem Cell Transplantation (HSCT). The amount of SC infused into the patient affects the engraftment time and healing process of the patient. In this study, we aimed to compare which of the DMSO-not removed and DMSO-removed samples showed the CD34 + SC amount more accurately as the SC amount determination method after the SC was dissolved after cryopreservation in patients who will undergo HSCT. A total of 22 patients were included in the study. All 22 patients were transplanted from frozen samples using DMSO. After the SC products were dissolved in a 37 °C water bath, they were washed 2 times and the amount of CD34+ SC was studied from the samples taken by removing DMSO and without removing DMSO. In the findings, the amounts of CD34+ SC studied with both methods were compared. The increase in the number and percentage of CD34+ SC after DMSO-removed was found to be statistically significant both in terms of difference and proportionally, and the calculated effect sizes also showed that the increase was clinically significant (Cohen's d is between 0.43 and 0.677). After thawing the frozen SCs of the patients who will undergo HSCT, the analysis of CD34+ SCs from which DMSO is removed provides a more accurate calculation of the CD34+ SC amount in the AP.

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 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.

Long-Term Cryopreservation Does Not Affect Quality of Peripheral Blood Stem Cell Grafts: A Comparative Study of Native, Short-Term and Long-Term Cryopreserved Haematopoietic Stem Cells

Cryopreserved haematopoietic progenitor cells are used to restore autologous haematopoiesis after high dose chemotherapy. Although the cells are routinely stored for a long period, concerns remain about the maximum storage time and the possible negative effect of storage on their potency. We evaluated the effect of cryopreservation on the quality of peripheral stem cell grafts stored for a short (3 months) and a long (10 years) period and we compared it to native products.The viability of CD34+ cells remained unaffected during storage, the apoptotic cells were represented up to 10% and did not differ between groups. The clonogenic activity measured by ATP production has decreased with the length of storage (ATP/cell 1.28 nM in native vs. 0.63 in long term stored products, P < 0.05). Only borderline changes without statistical significance were detected when examining mitochondrial and aldehyde dehydrogenase metabolic activity and intracellular pH, showing their good preservation during cell storage. Our experience demonstrates that cryostorage has no major negative effect on stem cell quality and potency, and therefore autologous stem cells can be stored safely for an extended period of at least 10 years. On the other hand, long term storage for 10 years and longer may lead to mild reduction of clonogenic capacity. When a sufficient dose of stem cells is infused, these changes will not have a clinical impact. However, in products stored beyond 10 years, especially when a low number of CD34+ cells is available, the quality of stem cell graft should be verified before infusion using the appropriate potency assays.

Evaluation of a clinical-grade, cryopreserved, ex vivo-expanded stem cell product from cryopreserved primary umbilical cord blood demonstrates multilineage hematopoietic engraftment in mouse xenografts

BACKGROUND AIMS

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative therapy for a wide range of malignant and genetic disorders of the hematopoietic and immune systems. Umbilical cord blood (UCB) is a readily available source of stem cells for allo-HSCT, but the small fixed number of hematopoietic stem and progenitor cells (HSPCs) found in a single unit limits its widespread use in adult recipients. The authors have previously reported that culturing UCB-CD34⁺ cells in serum-free media supplemented with a combination of cytokines and the histone deacetylase inhibitor valproic acid (VPA) led to expansion of the numbers of functional HSPCs. Such fresh expanded product has been advanced to the clinic and is currently evaluated in an ongoing clinical trial in patients with hematological malignancies undergoing allo-HSCT. Here the authors report on the cryopreservation of this cellular product under current Good Manufacturing Practice (cGMP).

METHODS

cGMP VPA-mediated expansion was initiated with CD34⁺ cells isolated from cryopreserved primary UCB collections, and the functionality after a second cryopreservation step of the expanded product evaluted in vitro and in mouse xenografts.

RESULTS

The authors found that the cryopreserved VPA-expanded grafts were characterized by a high degree of viability, retention of HSPC phenotypic subtypes and maintenance of long-term multilineage repopulation capacity in immunocompromised mice. All cellular and functional parameters tested were comparable between the fresh and cryopreserved VPA-expanded cellular products.

CONCLUSIONS

The authors' results demonstrate and support the practicality of cryopreservation of VPA-expanded stem cell grafts derived from UCB-CD34⁺ cells for clinical utilization.

A novel method to evaluate prethawing viability of cryopreserved CD34+ hematopoietic stem cells for autologous transplantation

BACKGROUND

Cryopreservation of CD34+ hematopoietic stem cells (HSCs) is associated with variable loss of viability. Although postfreezing CD34+ cell viability can be assessed on the sampling tube (bag tail) directly connected to the main bag (mother bag), results often underestimate the actual viability observed when the mother bag is thawed and reinfused. We assessed a novel method to measure postfreezing CD34+ cell viability, based on small bag (minibag) samples; results were compared with those obtained on the corresponding mother bags and bag tails.

STUDY DESIGN AND METHODS

Sixty-one apheresis procedures of 42 patients undergoing autologous HSC transplant were analyzed. Viable CD34+ cells were quantified with flow cytometry before controlled rate freezing (ICE-CUBE14M system, SY-LAB- IceCube, SIAD), after 10 days of storage (mini-bag and bag tail), and before reinfusion (aliquot from a thawed mother bag). Results were compared using Student's t test and Spearman's rho correlation test.

RESULTS

The mean CD34+ cell viability before cryopreservation was 99.3% (confidence interval [CI], 98.94-99.65%); the mean amount of CD34+ cells, white blood cells and neutrophils in the mother bag was 0.8 ± 1.1 × 10⁹ /L, 63.4 ± 23.5 × 10⁹ /L, and 25.7 ± 15.5 × 10⁹ /L, respectively. Mother bags postthawing CD34+ cell viability was 72.3% (CI, 67.74-76.85%; p < 0.01 compared to prefreezing); no difference was observed with respect to minibags (73.7%; CI, 69.80-77.59%; p = NS), whereas significantly lower values were found for bag tails (58.6%; CI, 54.19-63.00%; p < 0.01 vs. both mini- and mother bags).

CONCLUSION

Compared to bag tails, minibags represent a more accurate tool to measure the CD34+ cell viability of the apheresis mother bag prior to reinfusion; in addition, minibags may could be of help for case-by-case calculation of the amount of apheresis to be infused to patients undergoing autologous HSC transplant.

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

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

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.

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.

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.

The Functional Effect of Repeated Cryopreservation on Transduced CD34+ Cells from Patients with Thalassemia

Stable gene marking and effective engraftment of gene-modified CD34⁺ hematopoietic stem cells is a prerequisite for gene therapy success but may be challenged by the inevitable cryopreservation of the final product prior to extensive quality assurance testing. We investigated the β-globin gene transfer potency in fresh and cryopreserved CD34⁺ cells from mobilized patients with β-thalassemia, as well as the qualitative impact of repeated freeze/thaw cycles on the functionality of cultured and unmanipulated CD34⁺ cells in terms of engrafting capacity in a xenotransplantation model, under partial myeloablation. Cells transduced fresh or after one freeze-thaw cycle yielded similar clonogenic and gene transfer frequencies. Repeated cryopreservation cycles did not affect the transduction rates whereas either one or two freeze-thaw cycles of cultured-but not of unmanipulated-cells significantly reduced their clonogenicity. No differences in the engrafting potential of gene-corrected cells subjected to either none or up to two cryopreservation cycles, were encountered post xenotransplantation. Overall, we assessed the gene transfer efficiency, clonogenicity and engrafting capacity of cryopreserved CD34⁺ cells and the impact of repeated freeze/thaw cycles in their performance. These observations may prove essential in the design of gene therapy trials, considerably facilitating their logistics.

The relationship between CD34+ stem cell dose and time to neutrophil recovery in autologous haematopoietic stem cell recipients-A single centre experience

A retrospective, observational study was performed of 112 patients who underwent autologous haematopoietic stem cell transplantation (ASCT) to determine the relationship between CD34+ stem cell dose and neutrophil engraftment. Importantly, a novel approach to more accurately calculate time to neutrophil engraftment was employed. The results demonstrated that a higher CD34+ stem cell dose was associated with faster neutrophil recovery (P < 0.05). CD34+ stem cell dose using actual and ideal patient body weight were both equally predictive of neutrophil engraftment as were absolute and viable CD34+ measurements. The clinical implications for this relationship are limited with an increase in CD34+ stem cell dose by 1 × 10⁶/kg reducing the neutrophil engraftment time by only 3 h and 50 min. The median time to neutrophil recovery was 217 h (9 days and 1 h) and this relatively early engraftment time may be related to an early initiation of granulocyte colony-stimulating factor (G-CSF) on day +1 post-transplant. Female patients engrafted 17 h faster than their male counterparts on multi-variate analysis (P < 0.05). Conditioning chemotherapy, bacteraemia, G-CSF dose/kg body weight and increasing age had no impact on time to neutrophil recovery.

Relevance of flow cytometric enumeration of post-thaw leucocytes: influence of temperature during cell staining on viable cell recovery

BACKGROUND AND OBJECTIVES

Our post-thaw cell recovery rates differed substantially in interlaboratory comparisons of identical samples, potentially due to different temperatures during cell staining.

MATERIALS AND METHODS

Viable CD34(+) cells and leucocyte (WBC) subtypes were quantified by multiparameter single-platform flow cytometry in leucapheresis products collected from 30 adult lymphoma and myeloma patients, and from 10 paediatric patients. After thawing, cells were prepared for analysis within 30 min between thawing and acquisition, at either 4°C or at room temperature.

RESULTS

For cell products cryopreserved in conventional freezing medium (10% final DMSO), viable cell recovery was clearly lower after staining at 4°C than at RT. Of all WBC subtypes analysed, CD4(+) T cells showed the lowest median recovery of 4% (4°C) vs. 25% (RT), followed by CD3, CD34 and CD8 cells. The recovery was highest for CD3γδ cells with 44% (4°C) vs. 71% (RT). In the 10 samples cryopreserved in synthetic freezing medium (5% final DMSO), median recovery rates were 89% for viable CD34 (both at 4°C and RT) and 79% (4°C) vs 68% (RT) for WBC.

CONCLUSIONS

The post-thaw environment and, potentially, the cryoprotectant impact the outcome of cell enumeration, and results from the analysis tube may not be representative of the cells infused into a patient.