A physician wonders if any colleagues are familiar with published data or have first hand experience with long-term storage of stem cells in the vapor phase of liquid nitrogen vs. minus 80°C in a mechanical freezer? She has found many studies that compare minus 80°C and vapor phase of liquid nitrogen for short-term storage, but could only find one well controlled study that compared minus 80°C and vapor phase of liquid nitrogen for long-term storage (Valeri and Pivacek in Transfusion, 1996). Unfortunately, the Valeri and Pivacek study only compared storage times up to 2.4 years. Specifically, how long do stem cells survive after controlled rate freezing and storage in minus 80°C vs. storage in liquid nitrogen? She is interested to know: (1) how well the stored products engraft, (2) perform in methylcellulose CFU assays, or (3) perform in viability and CD34 flow cytometry analysis. In addition, if cells are transferred from liquid nitrogen to minus 80°C, how long do stem cells survive in the minus 80°C freezer?
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