Cord blood HPC collections maintained at 4 °C retained higher TNC counts, MNC counts, and CD45+ cell viability over a 72- to 96-hour storage period.

Total CFUs obtained in 7- and 14-day CFU assays are comparable and show similar levels of interlaboratory variability. The major source of this variability is due to differences in how CFU plates are scored by individuals at different sites. UCB progenitor cells can be maintained in methylcellulose-based media at room temperature for up to 48 hours prior to transport without a significant loss in CFUs.

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Tourcoing, France) collection bags and stored for 72 hours at 4°C using a commercial methylcellulose-based CFC assay kit (Stem Alpha ID, Stem Alpha, St Clement les Places, France). The decrease in CFC recovery was also accompanied by a significant decrease in total nucleated cell (TNC) and CD34+ cell recovery of comparable magnitude (14%-18%). These results contrast with those previously published by our group 1 utilizing different collection systems, TNC and CD34+ cell counting methods, and commercial CFC assay kits (methylcellulose-based medium supplemented with erythropoietin, Methocult GF H4434, Stem-Cell Technologies, Vancouver, BC, Canada).In our article, the primary focus was to evaluate the differential susceptibility of polymorphonuclear leukocyte, lymphocyte, monocyte, and CD34+ cell populations to in vitro loss of cell viability utilizing alternative methods for measuring total cell viability (TB and AO/PI) and viability of individual cell populations based on flow cytometric measurements with 7-aminoactinomycin staining combined with functional viability assessment based on CFC assay. We were specifically interested in the correlation between CFC recovery and CD34+ cell viability, which we were able to confirm. In our study, after 72-hour storage at 4°C (84-88 hr postcollection), we found a small decrease in TNC recovery (4%), viable CD34+ cell recovery (9%), and CFC recovery (16%) that did not reach significance and proposed that based on these results, it might be possible to delay processing of UCB products by storing products at 4°C. Our results clearly showed that recovery of viable CD34+ cells and CFC content was significantly better at 4°C than at 24°C (room temperature) or elevated temperatures (37°C).Although Ivanovic and colleagues did not report results for measurements of cell viability or for storage of UCB products at temperatures other than 4°C, the decreases in TNC, CD34+, and CFC recovery they observed (14%-22%) are not markedly different from the 4% to 16% decreases we observed in the same variables, respectively. These differences could easily be accounted for simply on the basis of the different methods used for cell counting and CFC assay. In our studies, we did not observe a significant loss of TNC recovery until there were marked decreases in total cell viability, CD34+ cell viability, and CFC recovery. This is expected since although the automated hematology analyzers used to determine TNC measure viable and nonviable cells, it is only after the cells have undergone marked loss in viability and cellular fragmentation that we expect to see a decrease in TNCs. The approximately 15% decrease in TNC recovery and comparable loss of TNCs, viable CD34+ cells, and CFCs observed by Ivanovic and coworkers is concerning and suggests a systematic failure to recover cells after 72 hours of storage at 4°C. In any case, we agree with the conclusion of the authors that larger trials from different centers are necessary before we should provide widespread endorsement of the practice of permitti...