A Belgian scientist reported that he was able to develop human embryonic stem cells (hESCs) from a blastomere of a four-cell stage embryo at the “European Society of Human Reproduction and Embryology” meeting.
Researchers have been unsure as to when in early development blastomeres cease to be totipotent, i.e., able to develop into all cell types of the body. The results from the current study, done by Hilde Van de Velde of the Vrije Universiteit Brussel, confirm his group’s previous report that at the four-cell stage the cells are equal and totipotent.
“Previously, scientists have been able to derive hESC lines at the eight-cell stage,” notes Dr. Van de Velde. “But success rates were variable, and it was necessary to culture them by mixing with established hESC lines. We have been able to derive hESCs at an earlier stage of embryonic development and without the need for co-culture with established hESC lines.”
Dr. Van de Velde used mature eggs donated by couples being treated at the University's IVF center. Embryos were obtained after intracytoplasmic sperm injection using sperm from a consenting donor. Then, three good quality four-cell stage embryos were split into 12 single blastomeres and allowed to grow in vitro to produce 12 morulas; the morula stage occurs 96 hours after fertilization when the egg divides four to five times.
The morulas were cultured in the conventional way for hESC derivation. Dr. Van de Velde reports that one morula resulted in a stable hESC line. His team thus concluded that at least one cell was pluripotent.
"Now we will try to derive four hESC lines from the same embryo in order to compare the potency capacity of all four cells," says Dr. Van de Velde.