Four days later, embryos in diapause were flushed out of the uterus and cultured on STO feeder cells in four-well plates in Dulbecco's Modified Eagle Medium (DMEM) supplemented with 20% Fetal Bovine Serum (Hyclone), 0.1 mM Non-Essential Amino Acids (Invitrogen), 2 mM L-glutamine (Invitrogen), 50 U/ml Penicillin-Streptomysin (Invitrogen), and 0.11 mM 2-mercaptoethanol (Invitrogen).