• Frida Holm, Susanne Ström, José Inzunza, Duncan Baker, Anne-Marie Strömberg, Björn Rozell, Anis Feki, Rosita Bergström, and Outi Hovatta.
• Division of Obstetrics and Gynecology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, K57, Karolinska University Hospital, Huddinge, Stockholm 141 86, Sweden.
• Hum. Reprod. 2010 May 1; 25 (5): 1271-9.

BackgroundBoth human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) bear a great potential in regenerative medicine. In addition to optimized clinical grade culture conditions, efficient clinical grade cryopreservation methods for these cells are needed. Obtaining good survival after thawing has been problematic.MethodsWe used a novel, chemically defined effective xeno-free cryopreservation system for cryostorage and banking of hESCs and iPSCs. The earlier established slow freezing protocols have, even after recent improvements, resulted in low viability and thawed cells had a high tendency to differentiate. The medium is a completely serum and animal substance free product containing dimethylsulfoxide, anhydrous dextrose and a polymer as cryoprotectants. The cells were directly frozen at -70 degrees C, without a programmed freezer.ResultsThe number of frozen colonies versus the number of surviving colonies differed significantly for both HS293 (chi(2) = 9.616 with one degree of freedom and two-tailed P = 0.0019) and HS306 (chi(2) = 8.801 with one degree of freedom and two-tailed P = 0.0030). After thawing, the cells had a high viability (90-96%) without any impact on proliferation and differentiation, compared with the standard freezing procedure where viability was much lower (49%). The frozen-thawed hESCs and iPSCs had normal karyotype and maintained properties of pluripotent cells with corresponding morphological characteristics, and expressed pluripotency markers after 10 passages in culture. They formed teratomas containing tissue components of the three germ layers.ConclusionThe defined freezing-thawing system described here offers an excellent simple option for banking of hESCs and iPSCs.

40 keywords...

hide…