Infusion of unwashed umbilical cord blood stem cells after thawing for allogeneic transplantation

Trehalose in Biomedical Cryopreservation-Properties, Mechanisms, Delivery Methods, Applications, Benefits, and Problems

Cells and tissues are the foundation of translational medicine. At present, one of the main technological obstacles is their preservation for long-term usage while maintaining adequate viability and function. Optimized storage techniques must be developed to make them safer to use in the clinic. Cryopreservation is the most common long-term preservation method to maintain the vitality and function of cells and tissues. But, the formation of ice crystals in cells and tissues is considered to be the main mechanism that could harm cells and tissues during freezing and thawing. To reduce the formation of ice crystals, cryoprotective agents (CPAs) must be added to the cells and tissues to achieve the cryoprotective effect. However, conventional cryopreservation of cells and tissues often needs to use toxic organic solvents as CPAs. As a result, cryopreserved cells and tissues may need to go through a time-consuming washing process to remove CPAs for further applications in translational medicine, and multiple valuable cells are potentially lost or killed. Currently, trehalose has been researched as a nontoxic CPA due to its cryoprotective ability and stability during cryopreservation. Nevertheless, trehalose is a nonpermeable CPA, and the lack of an effective intracellular trehalose delivery method has become the main obstacle to its use in cryopreservation. This article illustrated the properties, mechanisms, delivery methods, and applications of trehalose, summarized the benefits and limits of trehalose, and summed up the findings and research direction of trehalose in biomedical cryopreservation.

Evaluation of DMSO dextrose as a suitable alternative for DMSO dextran in cord blood cryopreservation

BACKGROUND AND OBJECTIVES

Umbilical cord blood is considered an alternative source of hematopoietic stem cells. Standard banking procedures use 50/55% DMSO in dextran 40 for cryopreservation and dextran-based solutions for thawing, however, due to the potential risk of crystallization of dextran, dextran 40 approved for clinical use has become limited or unavailable. This affects cryopreservation and thawing procedures. Carbohydrates, in particular sucrose, trehalose and glucose, have been shown to be effective in reducing cell damage during dehydration and have cryoprotective potential. We aim to study a 50/55% DMSO in 5% dextrose cryopreservation solution as an alternative to DMSO dextran.

MATERIALS AND METHODS

Eighteen samples were divided into two aliquots and cryopreserved, one using standard solution and the other with DMSO dextrose experimental solution. Both aliquots were thawed and diluted with PBS or saline. Total nucleated cells counts, 7-AAD viability of CD45⁺ cells and recovery of CD34⁺ viable cells were assessed on thawed samples and compared between pair of aliquots.

RESULTS

No differences were observed in the total nucleated cells recovery between cryopreservation solutions, however, higher viability and CD34⁺ viable cells recoveries were observed using the experimental solution.

CONCLUSION

Results showed that DMSO dextrose cryopreservation solution had better results than the standard solution when thawed in an isotonic solution. This indicates that DMSO dextrose is probably a better alternative for direct infusion or when dextran thawing solutions are unavailable. Viability of CD45⁺ cells and recovery of CD34⁺ viable cells have positive correlation with engraftment, highlighting the relevance of the optimization of the cryopreservation and thawing process.

Hydroxyethylstarch in cryopreservation - mechanisms, benefits and problems

As the progress of regenerative medicine places ever greater attention on cryopreservation of (stem) cells, tried and tested cryopreservation solutions deserve a second look. This article discusses the use of hydroxyethyl starch (HES) as a cryoprotectant. Charting carefully the recorded uses of HES as a cryoprotectant, in parallel to its further clinical use, indicates that some HES subtypes are a useful supplement to dimethysulfoxide (DMSO) in cryopreservation. However, we suggest that the most common admixture ratio of HES and DMSO in cryoprotectant solutions has been established by historical happenstance and requires further investigation and optimization.

Cell recovery comparison between plasma depletion/reduction- and red cell reduction-processing of umbilical cord blood

BACKGROUND AIMS

Limited cell dose has hampered the use of cord blood transplantation (CBT) in adults. One method of minimizing nucleated cell loss in cord blood (CB) processing is to deplete or reduce plasma but not red blood cells - plasma depletion/reduction (PDR).

METHODS

The nucleated cell loss of PDR was studied, and determined to be less than 0.1% in the discarded supernatant plasma fraction in validation experiments. After testing and archival sampling, the median nucleated cell recovery for PDR processing was 90%, and median CD34(+) cell recovery 88%. In a CB bank inventory of 12 339 products with both pre- and post-processing total nucleated cells (TNC), PDR processing resulted in median post-processing TNC recoveries of 90.0% after testing and archival samples removal. Using the same 10 CB units divided into two halves, we compared directly the recovery of PDR against hydroxyethyl starch red cell reduction (RCR) for TNC, CD34(+) cells and colony-forming units (CFU-GM, CFU-E, CFU-GEMM and total CFU) after parallel processing. We also compared the loss of very small embryonic-like stem cells (VSEL).

RESULTS

We demonstrated significantly higher recoveries using PDR for TNC (124%), CD34(+) cells (121%), CFU-GM (225%), CFU-GEMM (201%), total CFU (186%) and VSEL (187%). The proportion of high TNC products was compared between 10 912 PDR and 38 819 RCR CB products and found to be 200% higher for products that had TNC ≥150 × 10(7) (P = 0.0001) for the PDR inventory.

CONCLUSIONS

Our data indicate that PDR processing of CB provides a significantly more efficient usage of this valuable and scarce resource.

Unrelated umbilical cord blood transplantation for adults with haematological malignancies: results from a single Australian centre

BACKGROUND

A number of haematological malignancies can be cured by allogeneic stem cell transplantation but only approximately 30% of Australians have a suitable histocompatible related donor. Matched donors can be found on international registries of unrelated volunteers for a proportion of the remaining patients. For those patients in need of an allogeneic transplant, but for whom a suitable matched related or unrelated adult donor cannot be found, the use of banked unrelated umbilical cord blood has emerged as a potential option. However, there is uncertainty about the applicability of this technique for the majority of adult patients as a result of limitations in the number of cells in banked cord blood units and the degree of mismatching for histocompatibility antigens.

AIMS

The aim of this study was to define the feasibility of allogeneic stem cell transplantation using single unrelated cord blood units in a cohort of adults with poor prognosis leukaemia or lymphoma.

METHODS

Nine patients with haematological malignancies (five with acute myeloid leukaemia, one with acute lymphoblastic leukaemia, one with Hodgkin lymphoma and two with non-Hodgkin lymphomas) received transplants of cryopreserved cord blood after conditioning therapy with high-dose cyclophosphamide, total body irradiation and antithymocyte globulin. Cord units contained a median 2.6 x 10(7) nucleated cells/kg recipient bodyweight and were matched for four (seven cases) or five (two cases) major histocompatibility complex class 1 and 2 antigens. Patients were given post-transplant immunosuppression with cycosporin and methylprednisolone.

RESULTS

Neutrophil recovery to 0.5 x 10(9)/L was seen by median day 30 after transplant in all seven patients who survived more than 1 month post-transplant. Platelet recovery to 50 x 10(9)/L occurred by median day 81 in five evaluable patients. Acute graft versus host disease (GVHD) grades II-IV was seen in four of seven evaluable patients and limited chronic GVHD was seen in four of five. Infection was the most common complication. Four patients died before day 100 of infection (methicillin-resistant Staphylococcus aureus septicaemia, respiratory syncitial virus pneumonia), GVHD and multi-organ failure, and intracranial bleeding. Five patients survived 7-69 months post-transplant, without evidence of relapse of the underlying malignancy.

CONCLUSION

Unrelated cord blood transplantation is feasible in adults with high-risk malignancy, with infection relating to immunocompromise being the major limitation.