New Technique Harvests Stem Cells at Earlier Stage

Thursday, July 10, 2008; 3:00 AM

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WEDNESDAY, July 9 (HealthDay News) -- Scientists say they have finally succeeded in developing human embryonic stem cells earlier in the development stage of a blastomere, or a 4-cell stage embryo, so the whole embryo is not destroyed.

The development, expected to be presented Wednesday at the European Society of Human Reproduction & Embryology annual conference in Barcelona, may make stem cell research easier to conduct by not raising as many ethical concerns, the researchers added.

"Previously, scientists have been able to derive hESC [human embryonic stem cell] lines at the 8-cell stage," Hilde Van de Velde of the Vrije Universiteit Brussel, Brussels, Belgium, said in a news release issued by the society, "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. Now we have derived a second hESC from one cell of a 4-cell stage embryo. Given the complex nature of earlier attempts, we were pleased that we could develop a technique that seemed simple and was also reproducible."

Blastomeres form in the early stages of embryonic development when important changes occur: inner cells become the fetus, and outer cells change into trophoblast, the outermost layer of the embryo that hooks into the uterus and becomes a feeding tube for the developing egg.

Working with mature eggs donated by couples undergoing in vitro fertilization, researchers split three 4-cell stage embryos into a dozen single blastomeres. They then allowed them to grow in vitro and cultured them using conventional methods for hESC derivation. From these 12, one resulted in a stable hESC line, including one that scientists determined was pluripotent, or derived from the inner cells at the blastocyst stage, just as most other established hESC lines are.

"Now we will try to derive four hESC lines from the same embryo in order to compare the potency capacity of all four cells," Van de Velde said.