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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 × 107 ( 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. [ABSTRACT FROM AUTHOR]

Lysis of erythrocytes using hypotonic solutions is one approach to remove red blood cells (RBCs) from umbilical cord blood (UCB), bone marrow (BM), and peripheral blood (PB) before flow cytometric analysis or sorting of nucleated cells (NCs). Our team employed this separation step to prepare UCB-, BM-, or PB-derived cells to sort very small embryonic-like stem cells (VSELs). We noticed that depletion of RBCs from UCB by hypotonic lysis resulted in a significant increase in the number of NCs including VSELs that bind Annexin-V (Ann-V). Surprisingly, these cells were not apoptotic and displayed normal proliferative potential. To explain this discrepancy, we show that RBC-derived microvesicles (RMV) released during erythrocyte lysis may transfer phosphatidylserine (PS) to the surface of NCs and ‘mark’ them falsely positive as apoptotic cells. This observation should be considered whenever Ann-V binding viability assays are employed to evaluate the quality of NCs depleted from erythrocytes via hypotonic lysis. [ABSTRACT FROM AUTHOR]