An alternative to dextran for the thawing of cord blood units.

BACKGROUND: Preparation of umbilical cord blood units (CBUs) for infusion requires a step of dilution or washing to reduce the toxicity of the dimethyl sulfoxide present in the freezing solution. However, the worldwide shortage of clinical-grade dextran 40, the most widely used cord blood dilution or washing solution, prompted us to search for an alternative solution. We elected to evaluate the performance of alternative solutions that could be used as potential replacements for the dextran 40-based solution. STUDY DESIGN AND METHODS: Frozen CBUs were rapidly thawed and immediately diluted 1:4 in each of 10 dilution solution variants of dextran 40, Plasma-lyte, or Hespan. We compared these alternatives by assessing viability, CD34, CD45, and colony-forming units recovery postthaw. RESULTS: A significantly lower CD34 and CD45 recovery was observed in all solutions without human serum albumin (HSA). All solutions with 5% HSA gave recovery, viability, and potency figures similar to the dextran 40/HSA solution. CONCLUSION: Based on our results and considering that Plasma-lyte A (PA)/HSA is already used for the thawing of CD34 from mobilized blood, we conclude that PA/HSA could be a safe and efficient solution for the replacement of dextran 40-based dilution solutions.

A global look into human T cell subsets before and after cryopreservation using multiparametric flow cytometry and two-dimensional visualization analysis.

The cryopreservation of human lymphocytes is an essential step for the achievement of several cellular therapies. Besides, T cells are considered as promising actors in cancer therapy for their cytotoxic and regulatory properties. Consequently, the development of tools to monitor the impact of freezing and thawing processes on their fine distribution may be an asset to achieve quality control in cellular therapy. In this study, the phenotypes of freshly isolated human mononuclear cells were compared to those observed following one cycle of cryopreservation and rest periods 0h, 1h and 24h after thawing but before staining. T cells were scrutinized for their distribution according to naive, memory effector, regulatory and helper subsets. Flow cytometry analyses were done using eight-color antibody panels as proposed by the Human Immunophenotyping Consortium. Data were further analyzed by using conventional directed gating and clustering software, namely SPADE and viSNE. Overall, SPADE and viSNE tools were very efficient to monitor the outcome of PBMC populations and T cell subsets. T cells were more sensitive to cryopreservation than other cells. Our results indicated that submitting the thawed cells to a 1h rest period improved the detection of some cell markers when compared to fresh samples. In contrast, cells submitted to a 24h rest period, or to none, were less representative of fresh sample distribution. The heterogeneity of PBMC, as well as the effects of freeze-thaw cycle on their distribution, can be easily monitored by using SPADE and viSNE.

In Vitro Culture of Human Hematopoietic Stem Cells in Serum Free Medium and Their Monitoring by Flow Cytometry.

Hematopoietic stem cells can be isolated from human blood cells trapped in leukoreduction systems. The leukoreduction systems filters or chambers are usually discarded from routine blood or platelet donations in blood banks around the world. These CD34+ cells are a good source of normal stem cells and can be used as models to characterize the blood stem cells before and after culture in vitro. This chapter contains detailed methodologies for the isolation of stem cells from peripheral blood, the culture of these cells in a medium exempt of animal proteins and for the flow cytometry analysis of the resulting cell population for the characterization of their differentiation.

Heterogeneity of in vitro-cultured CD34+ cells isolated from peripheral blood.

BACKGROUND AIMS: For transplantation, hematopoietic stem cells (HSC) are obtained from bone marrow, cord blood and mobilized adult peripheral blood. HSCs are present in the blood of healthy adults and can be recovered in leuko-reduction system chambers, with a potential yield of 1 to 4 × 10(6) CD34+ cells per unit. Some groups have investigated this valuable source of stem cells; however, investigations are still needed to support their use. METHODS: CD34+ cells were purified from leuko-reduction system chambers and cultured with a defined custom medium without animal protein and supplemented with interleukin-3, interleukin-6, Fms-like tyrosine kinase 3, stem cell factor and thrombopoietin. Cells were cultured under 8% and 21% oxygen levels. With the use of multiparametric flow cytometry analysis, the phenotypes of emerging populations were compared between oxygen levels and resting CD34+ cells. Both conventional gating and clustering analysis were used to visualize the cellular outcome. RESULTS: A maximum expansion of 20-fold was obtained without major differences in viability, number of cells or cellular heterogeneity between atmospheric and physiologic oxygen conditions. Worthy of note, phenotype analysis revealed that megakaryocyte and erythrocyte progenitors were favored, albeit more moderately when submitted to 8% O2. CONCLUSIONS: This study suggests that the bias of cultured blood CD34+ cells toward megakaryocyte and erythrocyte progenitor cells can be reduced by use of 8% pO2. It also shows how clustering software, such as SPADE, can help visualize the complexity of stem cell differentiation.