Attempts for Generation of Embryonic Stem Cells from Human Embryos Following In Vitro Embryo Twinning.

In vitro embryo twinning can be used to increase the number of the human embryos available for production of human embryonic stem cell (hESC) lines. The aim of this study was to generate hESCs following the production of the twin embryos by in vitro embryo splitting procedures. In total 21 chromosomally abnormal (three pronuclei) embryos underwent in vitro embryo twinning and were allowed to develop to the blastocyst stage. As a result, 42 twin embryos were obtained, of which 24 developed to blastocyst stage. Using micromanipulation technique, the zona-free blastocysts were recovered and plated onto mitotically inactivated Yazd human foreskin fibroblast (Batch18; YhFF#18) feeder layers in microdrops. After 3 to 5 days of blastocyst culture onto human foreskin fibroblast feeder layers, the hESC-like outgrowths were passaged onto new feeders in microdrops. The initial outgrowths of hESC-like cells were generated, and cells were proliferated, passaged, and some of them expressed hESC and trophoblastic markers; however, no cell lines were established. This might be due to the low cell number and poor quality of inner cell mass within these twin blastocysts. In vitro embryo twinning by increasing the number of the human embryos could be useful in the future for the generation of new pluripotent stem cell lines. However, the challenge remains to optimize the methods.