title: Kinetics of cell death of frozen-thawed human embryonic stem cell colonies is reversibly slowed down by exposure to low temperature.
abstract: A major challenge in the widespread application of hES (human embryonic stem) cells in clinical therapy and basic scientific research is the development of efficient cryopreservation protocols. Conventional slow-cooling protocols utilizing standard cryoprotectant concentrations i.e. 10% (v/v) DMSO, yield extremely low survival rates of less than 5% as reported by previous studies. This study characterized cell death in frozen-thawed hES colonies that were cryopreserved under standard conditions. Surprisingly, our results showed that immediately after post-thaw washing, the overwhelming majority of hES cells were viable (approximately 98%), as assessed by the trypan blue exclusion test. However, when the freshly thawed hES colonies were placed in a 37 degrees C incubator, there was a gradual reduction in cell viability over time. The kinetics of cell death was drastically slowed down by keeping the freshly thawed hES colonies at 4 degrees C, with more than 90% of cells remaining viable after 90 min of incubation at 4 degrees C. This effect was reversible upon re-exposing the cells to physiological temperatures. The vast majority of low temperature-exposed hES colonies gradually underwent cell death upon incubation for a further 90 min at 37 degrees C. Hence, our observations would strongly suggest involvement of a self-induced apoptotic mechanism, as opposed to cellular necrosis arising from cryoinjury.
authors.affiliation: National University of Singapore, Singapore.
authors.forename: B C
authors.initials: BC
authors.lastname: Heng
authors.forename: C P
authors.initials: CP
authors.lastname: Ye
authors.forename: H
authors.initials: H
authors.lastname: Liu
authors.forename: W S
authors.initials: WS
authors.lastname: Toh
authors.forename: A J
authors.initials: AJ
authors.lastname: Rufaihah
authors.forename: T
authors.initials: T
authors.lastname: Cao
mesh_terms: D017209:Apoptosis; D002448:Cell Adhesion; D016923:Cell Death; D002470:Cell Survival; D002478:Cells, Cultured; D003080:Cold Temperature; D015925:Cryopreservation / Q000379:methods*; D053595:Embryonic Stem Cells / Q000166:cytology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics