Determining post-thaw CD34+ cell dose of cryopreserved haematopoietic progenitor cells demonstrates high recovery and confirms their integrity

Pros and Cons of Cryopreserving Allogeneic Stem Cell Products

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

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.

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.

Rebound and overshoot of donor-specific antibodies to human leukocyte antigens (HLA) during desensitization with plasma exchanges in hematopoietic progenitor cell transplantation: A case report

BACKGROUND

Donor-specific antibodies (DSA) to HLA have been associated with graft loss in hematopoietic progenitor cell (HPC) transplantation. Limited data associate therapeutic plasma exchange (TPE) with desensitization and successful engraftment. We report an attempt of desensitization and observed overshooting of DSA during transplantation.

CASE REPORT AND RESULTS

A 27-year-old female with cutaneous T cell lymphoma was scheduled for HPC transplantation from her HLA-haploidentical half-sister, who carried the HLA-DRB1*13:03:01 allele. The patient had the corresponding DSA. Lacking an alternative donor option at the time, we attempted a desensitization approach by immunosuppression with tacrolimus and mycophenolate mofetil (MMF). Unexpectedly, DSA increased from a mean fluorescence intensity (MFI) of 1835 on day -63 to 9008 on day -7. The MFI increased further during 3 TPE procedures and intravenous immunoglobulin (IVIG) until day -1. After transplantation, the DSA remained elevated despite 2 more TPE/IVIG procedures and graft-versus-host disease prophylaxis with high-dose cyclophosphamide, sirolimus, and MMF. Flow cytometric crossmatch, initially negative, turned positive after transplantation. Primary graft failure occurred and was attributed to antibody-mediated rejection. A second transplantation from a 7/8 HLA-matched unrelated donor, not carrying DRB1*13:03 allele, resulted in successful engraftment.

CONCLUSION

Unexpected and rapid increases of a DSA can occur despite the use of current desensitization approaches. This is problematic when conditioning has already started, as such increases are unlikely to be overcome by TPE or other interventions for desensitization. Overshoot of DSA in HPC transplantation has rarely been reported. Its cause remains unclear and can include underlying disease, immunotherapy, chemotherapy, or TPE.

Labeling mesenchymal cells with DMSA-coated gold and iron oxide nanoparticles: assessment of biocompatibility and potential applications

BACKGROUND

Nanoparticles' unique features have been highly explored in cellular therapies. However, nanoparticles can be cytotoxic. The cytotoxicity can be overcome by coating the nanoparticles with an appropriated surface modification. Nanoparticle coating influences biocompatibility between nanoparticles and cells and may affect some cell properties. Here, we evaluated the biocompatibility of gold and maghemite nanoparticles functionalized with 2,3-dimercaptosuccinic acid (DMSA), Au-DMSA and γ-Fe2O3-DMSA respectively, with human mesenchymal stem cells. Also, we tested these nanoparticles as tracers for mesenchymal stem cells in vivo tracking by computed tomography and as agents for mesenchymal stem cells magnetic targeting.

RESULTS

Significant cell death was not observed in MTT, Trypan Blue and light microscopy analyses. However, ultra-structural alterations as swollen and degenerated mitochondria, high amounts of myelin figures and structures similar to apoptotic bodies were detected in some mesenchymal stem cells. Au-DMSA and γ-Fe2O3-DMSA labeling did not affect mesenchymal stem cells adipogenesis and osteogenesis differentiation, proliferation rates or lymphocyte suppression capability. The uptake measurements indicated that both inorganic nanoparticles were well uptaken by mesenchymal stem cells. However, Au-DMSA could not be detected in microtomograph after being incorporated by mesenchymal stem cells. γ-Fe2O3-DMSA labeled cells were magnetically responsive in vitro and after infused in vivo in an experimental model of lung silicosis.

CONCLUSION

In terms of biocompatibility, the use of γ-Fe2O3-DMSA and Au-DMSA as tracers for mesenchymal stem cells was assured. However, Au-DMSA shown to be not suitable for visualization and tracking of these cells in vivo by standard computed microtomography. Otherwise, γ-Fe2O3-DMSA shows to be a promising agent for mesenchymal stem cells magnetic targeting.

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.

Kinetics of human myeloid-derived suppressor cells after blood draw

Background

Human myeloid-derived suppressor cells (MDSC) have been described as a group of immature myeloid cells which exert immunosuppressive action by inhibiting function of T lymphocytes. While there is a huge scientific interest to study these cells in multiple human diseases, the methodological approach varies substantially between published studies. This is problematic as human MDSC seem to be a sensible cell type concerning not only cryopreservation but also time point after blood draw. To date data on delayed blood processing influencing cell numbers and phenotype is missing. We therefore evaluated the kinetics of granulocytic MDSC (gMDSC) and monocytic MDSC (mMDSC) frequencies after blood draw in order to determine the best time point for analysis of this recently defined cell type.

Methods

In this study, we isolated peripheral blood mononuclear cells (PBMC) of patients with HIV infection or solid tumors directly after blood draw. We then analyzed the frequencies of gMDSC and mMDSC 2, 4 and 6 h after blood draw and after an overnight rest by FACS analysis using the standard phenotypic markers. In addition, part of the cells was frozen directly after PBMC preparation and was measured after thawing.

Results

gMDSC levels showed no significant difference using fresh PBMC over time with a limitation for the overnight sample. However they were massively diminished after freezing (p = 0.0001 for all subjects). In contrast, frequencies of fresh mMDSC varied over time with no difference between time point 2 and 4 h but a significantly reduction after 6 h and overnight rest (p = 0.0005 and p = 0.005 respectively). Freezing of PBMC decreased the yield of mMDSC reaching statistical significance (p = 0.04). For both MDSC subgroups, FACS analysis became more difficult over time due to less sharp divisions between populations.

Conclusions

According to our data human MDSC need to be studied on fresh PBMC. gMDSC can be studied with delay, mMDSC however should be studied no later than 4 h after blood draw. These results are crucial as an increasing number of clinical trials aim at analyzing MDSC nowadays and the logistics of blood processing implies delayed sample processing in some cases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0755-y) contains supplementary material, which is available to authorized users.

Cryopreservation in Closed Bag Systems as an Alternative to Clean Rooms for Preparations of Peripheral Blood Stem Cells

Autologous and allogeneic stem cell transplantation (SCT) represents a therapeutic option widely used for hematopoietic malignancies. One important milestone in the development of this treatment strategy was the development of effective cryopreservation technologies resulting in a high quality with respect to cell viability as well as lack of contamination of the graft.Stem cell preparations have been initially performed within standard laboratories as it is routinely still the case in many countries. With the emergence of cleanrooms, manufacturing of stem cell preparations within these facilities has become a new standard mandatory in Europe. However, due to high costs and laborious procedures, novel developments recently emerged using closed bag systems as reliable alternatives to conventional cleanrooms. Several hurdles needed to be overcome including the addition of the cryoprotectant dimethylsulfoxide (DMSO) as a relevant manipulation. As a result of the development, closed bag systems proved to be comparable in terms of product quality and patient outcome to cleanroom products. They also comply with the strict regulations of good manufacturing practice.With closed systems being available, costs and efforts of a cleanroom facility may be substantially reduced in the future. The process can be easily extended for other cell preparations requiring minor modifications as donor lymphocyte preparations. Moreover, novel developments may provide solutions for the production of advanced-therapy medicinal products in closed systems.

Long-term effects of cryopreservation on clinically prepared hematopoietic progenitor cell products

BACKGROUND AIMS

The question of how long hematopoietic progenitor cells (HPCs) destined for clinical applications withstand long-term cryopreservation remains unanswered. To increase our basic understanding about the stability of HPC products over time, this study focused on characterizing long-term effects of cryopreservation on clinically prepared HPC products.

METHODS

Cryovials (n = 233) frozen for an average of 6.3 ± 14.2 years (range, 0.003-14.6 years) from HPC products (n = 170) representing 75 individual patients were thawed and evaluated for total nucleated cells (TNCs), cell viability, viable CD34+ (vCD34+) cells and colony-forming cells (CFCs). TNCs were determined by use of an automated cell counter, and cell viability was measured with the use of trypan blue exclusion. Viable CD34 analysis was performed by means of flow cytometry and function by a CFC assay.

RESULTS

Significant losses in TNCs, cell viability, vCD34+ cells and CFC occurred on cryopreservation. However, once frozen, viable TNCs, vCD34+ cells and CFC recoveries did not significantly change over time. The only parameter demonstrating a change over time was cell viability, which decreased as the length of time that an HPC product was stored frozen increased. A significant negative correlation (correlation coefficient = -0.165) was determined between pre-freeze percent granulocyte content and post-thaw percent viability (n = 170; P = 0.032). However, a significant positive correlation was observed between percent viability at thaw and pre-freeze lymphocyte concentration.

CONCLUSIONS

Once frozen, HPC products were stable for up to 14.6 years at <-150°C. Post-thaw viability was found to correlate negatively with pre-freeze granulocyte content and positively with pre-freeze lymphocyte content.

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.

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

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

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.

Quantifying loss of CD34+ cells collected by apheresis after processing for freezing and post-thaw

INTRODUCTION

CD34(+) cells collected for autologous bone marrow transplantation (BMT) are usually quantified in the apheresis product after collection, but the necessity to repeat these measures post-thaw is controversial.

METHODS

We examined the loss of CD34(+) cells after collection, preparation for freezing and post-thaw in apheresis products collected for BMT.

RESULTS

Median number of CD34(+) cells collected per unit was 1.61×10(6)/kg, viability: 97-100%. This number decreased to 1.38×10(6)/kg, viability: 96-100% before freezing and was 1.17×10(6)/kg post-thaw. Viability decreased to 86-98%. The relative loss of viable PBHPC showed an inverse correlation with the ratio "CD34(+) cells/total nucleated cells" (r=-0.45; p=<0.0005). This relative loss was largest in patients with Hodgkin's lymphoma.

CONCLUSION

Cryopreservation and thawing of PBHPCs in leukapheresis products provokes a small but significant stem cell loss. So, quantification of viable CD34(+) cells post-thaw is important, especially in poorly mobilizing patients. Besides, the ratio "CD34(+) cells/total nucleated cells" after leukapheresis is an important parameter for prediction of neutrophil recovery after BMT.

Leukapheresis in non-cytokine-stimulated donors with a new apheresis system: first-time collection results and evaluation of subsequent cryopreservation

BACKGROUND

Adoptive cell therapy based on mononuclear cells (MNCs) became an important modality of cancer immunotherapy. Data about collection results and donor response of leukapheresis with the Spectra Optia v.5.0 (Terumo BCT) in nonmobilized donors are required.

STUDY DESIGN AND METHODS

Twelve MNC collections were performed using the Spectra Optia v.5.0 in non-cytokine-stimulated donors. Leukapheresis products and peripheral blood samples from donors were assayed for CD45+, CD34+, CD3+, and CD14+ cells by flow cytometry. Prefreeze and postthaw cell counts, cell viability, and numbers of colony-forming units were assessed in cryobags and compared to data from cryovials.

RESULTS

Leukapheresis yielded a mean of 5.26×10(9) ±2.2×10(9) CD45+ cells, 1.5×10(9) ±0.77×10(9) CD14+ monocytes, and 2.28×10(9) ±1.2×10(9) CD3+ Tcells by processing 6690±930mL of whole blood. A significant positive correlation between yield of CD3+ Tcells and residual platelets (PLTs) and red blood cells (RBCs) was observed. This did not apply for CD34+ and CD14+ white blood cell subsets. Mean collection efficiencies for CD14+ monocytes and CD3+ Tcells were 61.8±17 and 37.2±18%, respectively. Recovery of CD14+ cells after cryopreservation was 75.2±8.2%, which was significantly lower than recovery of CD45+ cells (81.4±5.5%; p=0.01).

CONCLUSION

This study of a small cohort demonstrates that the Spectra Optia v.5.0 is capable of collecting low product volumes with satisfactory MNC yields and low residual RBCs and PLTs in non-cytokine-mobilized apheresis. Our data suggest that cryovials can serve as a representative surrogate for the primary product cryobag.

Relative recovery of haematopoietic stem cell products after cryogenic storage of up to 19 years

There is an increasing trend towards long-term frozen storage of haematopoietic stem cells. For such stem cells, harvested from peripheral blood (PB) or BM, it is not known if stem cell viability decreases with time. In this study, 31 separate bags of stem cell product (SCP) stored for 11-19 years (median 15 years) were assessed for total nucleated cell (TNC) count, colony forming unit-granulocyte/macrophage (CFU-GM), CD34⁺ cell count and cell viability. The results were compared with the initial results obtained for the products at the time of stem cell harvest, and the percentage recovery of each parameter was plotted against time. Recovery of TNC, CD34⁺ cell count and cell viability decreased with time (P=<0.01) but CFU-GM did not. This study shows that SCPs harvested from PB and BM do deteriorate with long-term storage. This could have an impact on rates of engraftment.

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.

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.

Postthaw clotting of peripheral blood stem cell products due to insufficient anticoagulant

The amount of acid citrate dextrose formula A (ACD-A), which is a commonly used anticoagulant in leukopheresis, has to ensure both the safety of the donor and guarantee the integrity of the peripheral blood stem cell (PBSC) product until its transplant. Two recent consecutive cases of postthaw PBSC product clotting initiated a look-back investigation of the ACD-A percentage in leukopheresis products collected in our facility. The data indicated a significant difference between the average amount of ACD-A in prefreezing products collected during 2006 (11.4%) and in products collected during 2007 and 2008 (8.8% and 8.7%, respectively). These findings and the fact that the two clotted products had less than 7% ACD-A indicated that insufficient amount of anticoagulant might contribute to their clotting. This investigation prompted us to modify our collection and thawing procedures to prevent similar events in the future.