title: Caspase inhibitor Z-VAD-FMK enhances the freeze-thaw survival rate of human embryonic stem cells.
abstract: Previous study demonstrated that the low survival of human embryonic stem cells (hESC) under conventional slow-cooling cryopreservation protocols is predominantly due to apoptosis rather than cellular necrosis. Hence, this study investigated whether a synthetic broad-spectrum irreversible inhibitor of caspase enzymes, Z-VAD-FMK can be used to enhance the post-thaw survival rate of hESC. About 100 mM Z-VAD-FMK was supplemented into either the freezing solution, the post-thaw culture media or both. Intact and adherent hESC colonies were cryopreserved so as to enable subsequent quantitation of the post-thaw cell survival rate through the MTT assay, which can only be performed with adherent cells. Exposure to 100 mM Z-VAD-FMK in the freezing solution alone did not significantly enhance the post-thaw survival rate (10.2% vs. 9.9%, p > 0.05). However, when 100 mM Z-VAD-FMK was added to the post-thaw culture media, there was a significant enhancement in the survival rate from 9.9% to 14.4% (p < 0.05), which was further increased to 18.7% when Z-VAD-FMK was also added to the freezing solution as well (p < 0.01). Spontaneous differentiation of hESC after cryopreservation was assessed by morphological observations under bright-field microscopy, and by immunocytochemical staining for the pluripotency markers SSEA-3 and TRA-1-81. The results demonstrated that exposure to Z-VAD-FMK did not significantly enhance the spontaneous differentiation of hESC within post-thaw culture.
authors.affiliation: Stem Cell Laboratory, Faculty of Dentistry, National University of Singapore, Singapore, Singapore.
authors.forename: Boon Chin
authors.initials: BC
authors.lastname: Heng
authors.forename: Marie Veronique
authors.initials: MV
authors.lastname: Clement
authors.forename: Tong
authors.initials: T
authors.lastname: Cao
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology*; D002454:Cell Differentiation; D002470:Cell Survival / Q000187:drug effects*; D015925:Cryopreservation; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D053595:Embryonic Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D006801:Humans
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone