title: Assessing the toxic effects of DMSO on cord blood to determine exposure time limits and the optimum concentration for cryopreservation.
abstract: OBJECTIVE
  Advantages of using cord blood (CB) over other sources of haematopoietic progenitor cells, such as bone marrow, include the ability to cryopreserve and bank the samples until requested for a transplant. Cryopreservation requires the addition of a cryoprotectant to prevent the formation of intracellular ice during freezing. Dimethyl sulphoxide (DMSO) is commonly used at a concentration of 10% (v/v); however, there is evidence to suggest this chemical is toxic to cells as well as to patients after infusion.
  
  
  METHODS
  The toxic effects of DMSO were assessed through cell viability and in vitro functional assays in fresh and post-thaw CB samples before determining the maximum exposure time and optimal concentration for cryopreservation.
  
  
  RESULTS
  A dose-dependent toxicity of DMSO was observed in fresh samples with 40% removing all viable and functional haematopoietic progenitor cells (HPC). In fresh and post-thaw analysis, minimal toxic effect was observed when cryopreservation was delayed for up to 1 h after 10% DMSO addition. After thawing, DMSO washout was superior to dilution or unmanipulated when maintained for long periods (advantage observed 1 h after thawing). Finally, the optimum concentration for cryopreserving CB was found to be 7.5 to 10% with detrimental effects observed outside of this range.
  
  
  CONCLUSIONS
  These results support the use of 7.5-10% as the optimal DMSO concentration and the maximum exposure time should be limited to <1 h prior to freezing and 30 min post-thaw.
authors.affiliation: Anthony Nolan Cell Therapy Centre, Nottingham Trent University, Nottingham, UK.
authors.forename: L J
authors.identifier: http://orcid.org/0000-0002-5553-3707
authors.initials: LJ
authors.lastname: Fry
authors.affiliation: Banc de Sang I Teixits, Barcelona, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Querol
authors.affiliation: Anthony Nolan Cell Therapy Centre, Nottingham Trent University, Nottingham, UK.
authors.forename: S G
authors.initials: SG
authors.lastname: Gomez
authors.affiliation: John van Geest Cancer Research Centre, Nottingham Trent University, Nottingham, UK.
authors.forename: S
authors.initials: S
authors.lastname: McArdle
authors.affiliation: John van Geest Cancer Research Centre, Nottingham Trent University, Nottingham, UK.
authors.forename: R
authors.initials: R
authors.lastname: Rees
authors.affiliation: Anthony Nolan Research Institute, Royal Free Hospital, London, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Madrigal
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000009:adverse effects* / Q000633:toxicity; D004121:Dimethyl Sulfoxide / Q000009:adverse effects* / Q000633:toxicity; D005312:Fetal Blood / Q000187:drug effects*; D006801:Humans
chemical_list: D003451:Cryoprotective Agents; D004121:Dimethyl Sulfoxide
keywords: DMSO; cord blood; cryopreservation; dextran-40