title: Long-term storage of peripheral blood stem cells frozen and stored with a conventional liquid nitrogen technique compared with cells frozen and stored in a mechanical freezer.
abstract: BACKGROUND
  Cryopreservation of hematopoietic progenitor cells using liquid nitrogen and controlled-rate freezing requires complex equipment and highly trained staff and is expensive. We compared the liquid nitrogen method with methods using a combination of dimethyl sulfoxide (DMSO) and hydroxyethyl starch (HES) for cryopreservation followed by storage in mechanical freezers.
  
  
  METHODS
  Peripheral blood stem cells (PBSCs) were collected from normal donors by apheresis and allocated to one of four preservation and storage conditions: 1) 10% DMSO with freezing in liquid nitrogen and storage in liquid nitrogen, 2) 5% DMSO and 6% HES with freezing and storage in a -80 degrees C mechanical freezer, 3) 5% DMSO and 6% HES with freezing in a -80 degrees C mechanical freezer and storage in a -135 degrees C mechanical freezer, or 4) 5% DMSO and 6% HES with freezing and storage both in a 135 degrees C mechanical freezer. Cells were stored for 5 years during which total nucleated cells (TNCs), cell viability, CD34+ cell content, and colony-forming unit-granulocyte-macrophage content were determined.
  
  
  RESULTS
  There were some significant differences in the variables measured during freezing and the 5 years of storage compared to the values before freezing and storage; however, these differences were not consistent and do not favor one protocol over the others. Samples stored for 24 hours before cryopreservation showed a significant decrease in TNCs, but no other significant changes during the 5 years.
  
  
  CONCLUSIONS
  In vitro measurements indicate that PBSCs can be successfully frozen and stored using a combination of DMSO and HES providing smaller amounts of DMSO and allowing simplified freezing and storage conditions.
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA. mccul001@umn.edu
authors.forename: Jeffrey
authors.initials: J
authors.lastname: McCullough
authors.forename: Rebecca
authors.initials: R
authors.lastname: Haley
authors.forename: Mary
authors.initials: M
authors.lastname: Clay
authors.forename: Allison
authors.initials: A
authors.lastname: Hubel
authors.forename: Bruce
authors.initials: B
authors.lastname: Lindgren
authors.forename: Gary
authors.initials: G
authors.lastname: Moroff
mesh_terms: D001793:Blood Preservation / Q000379:methods; D002470:Cell Survival / Q000187:drug effects; D003114:Colony-Forming Units Assay; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005615:Freezing; D018380:Hematopoietic Stem Cell Transplantation / Q000379:methods / Q000592:standards; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D009584:Nitrogen
chemical_list: D003451:Cryoprotective Agents; D009584:Nitrogen; D004121:Dimethyl Sulfoxide