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After slow freezing, the survival rate of human embryonic stem (hES) cells is poor and inconsistent. The aim of this study was to increase the freeze-thaw survival rate of hES cells by utilizing the ROCK inhibitor Y-27632. hES cell colonies were first treated with Y-27632, followed by collagenase IV and TrypLE Select dissociation whereupon small clumps were slow frozen using 90% Knockout serum replacement and 10% dimethyl sulfoxide. After thawing at 37 C, the clumps were cultured in medium supplemented with 10 microM Y-27632 for 1 day. Our results show that the use of Y-27632 significantly increases the survival of hES cells after thawing compared with that of the control group. Y-27632-treated freeze-thawed hES cells retain morphology, stable karyotype, expression of cell surface markers, and the potential to differentiate into derivatives of all three germ layers after long-term culture. We have concluded that conventional slow freezing with Y-27632 treatment is efficient and convenient for the cryopreservation of hES cells.
Li et al. (Wed,) studied this question.