[Effective cryopreservation of human embryonic stem cells by programmed freezing].

Cryopreservation of human embryonic stem cells is an important and unsolved problem. A computer-controlled programmable cooler was used in the preservation of ES cells. Several effects have been experimentally studied, which include the cooling rates, the temperature of seeding, the temperatures before the samples being plunged into liquid nitrogen, and the cryoprotective agents. It was found that the favorable constitution of cryoprotective agents was Me2SO+ FBS+DMEM(1:3:6, v/v/v) with cooling protocol of -0.5 degrees C/min from 0 degrees C to -35 degrees C (seeding at -10 degrees C), and being plunged into the liquid nitrogen immediately. The high survival rate (81.8%) was obtained.