Cryopreservation of adherent human embryonic stem cells

Modulating Membrane Properties: The Effect of Trehalose and Cholesterol on a Phospholipid Bilayer

The protective properties of trehalose on cholesterol-containing lipid dipalmitoylphosphatidylcholine (DPPC) bilayers are studied through molecular simulations. The ability of the disaccharide to interact with the phospholipid headgroups and stabilize the membrane persists even at high cholesterol concentrations and restricts some of the changes to the structure that would otherwise be imposed by cholesterol molecules. Predictions of bilayer properties such as area per lipid, tail ordering, and chain conformation support the notion that the disaccharide decreases the main melting transition in these multicomponent model membranes, which correspond more closely to common biological systems than pure bilayers. Molecular simulations indicate that the membrane dynamics are slowed considerably by the presence of trehalose, indicating that high sugar concentrations would serve to avert possible phase separations that could arise in mixed phospholipid systems. Various time correlation functions suggest that the character of the modifications in lipid dynamics induced by trehalose and cholesterol is different in the hydrophilic and hydrophobic regions of the membrane.

Cryopreservation of human embryonic stem cells without the use of a programmable freezer

BACKGROUND

An effective freezing-thawing technique is crucial for the clinical application of human embryonic stem (ES) cells. The aim of this study was to find an optimal cryopreservation protocol for human ES cells using slow freezing-rapid thawing without a programmable freezer.

METHODS

The human ES cell line, SNUhES-3, was cultured on an STO feeder layer in gelatin-coated tissue culture dishes. All cryopreservation steps were performed using a simple commercial freezing container. The survival rate of cryopreserved-thawed human ES cells was estimated by counting colony numbers under a stereomicroscope. Initially, we compared the survival rates of cryopreserved human ES cells using three cryoprotectants: dimethylsulphoxide (DMSO), ethylene glycol (EG) and glycerol. In this experiment, 5% DMSO/95% fetal bovine serum (FBS) (vol/vol) showed the highest survival rate. We next tested the impact of various concentrations of FBS (95, 50 and 5%) with 5% DMSO, and then examined the effects of adding EG or glycerol to 5% DMSO + optimal FBS.

RESULTS

No significant difference in survival rate was observed between 95 and 50% FBS in the presence of 5% DMSO. A significant improvement in survival rate was obtained by adding 10% EG to 5% DMSO+50% FBS. After thawing, surviving cells were found to maintain the inherent characteristics of human ES cells.

CONCLUSION

5% DMSO+50% FBS+10% EG may be an optimal cryoprotectant for the slow freezing-rapid thawing of human ES cells.

Improved cryopreservation of human embryonic stem cells with trehalose

Human embryonic stem (ES) cells have been established either from fresh or frozen embryos. The recovery rates of undifferentiated human ES cells after cryopreservation with conventional slow-rate freezing and rapid-thawing methods are relatively low. The purpose of this study was to improve cryopreservation efficiency by modifying conventional methods with addition of trehalose. Immature oocytes donated from patients undergoing IVF treatment were utilized to generate blastocysts. One human ES cell line (named hES1) was established and characterized in detail. The hES1 cells expressed regular human ES cell markers, including stage-specific embryonic antigens SSEA-3, SSEA-4, tumour rejection antigens TRA-1-60, TRA-1-81 and octamer-binding transcription factor Oct-4 with high levels of alkaline phosphatase and telomerase activities. Cells could be differentiated to form teratomas in vivo. With slow-rate freezing and rapid-thawing methods modified by adding trehalose, the recovery rate of undifferentiated hES1 cells has been greatly improved from 15 to 48%. Cells retained pluripotency with normal karyotype after thawing. The results indicated that the use of trehalose is efficient and convenient for cryopreservation of human ES cells.