Researchers create human eggs from skin cells and reach blastocysts

Researchers at Oregon Health & Science University reported Tuesday that they have for the first time created human egg cells from a person’s skin cells, fertilized those eggs with sperm in the laboratory, and grown the resulting embryos to the blastocyst stage. The study, published in Nature Communications, describes a combination of cloning and chromosome-reduction techniques that produced 82 egglike cells, nine of which developed into blastocysts after fertilization and several days of laboratory culture.

The team used somatic cell nuclear transfer, a method that replaces the nucleus of a donor egg with the nucleus from a somatic cell, in this case skin. Because somatic nuclei contain two sets of chromosomes rather than the single set found in eggs, the researchers then induced a process they call mitomeiosis to mimic the natural halving of chromosome number that occurs during meiosis. That step removed one set of chromosomes from the reprogrammed cells, producing oocytes with a single set of 23 chromosomes and enabling fertilization with sperm.

Although the experiment produced fertilized embryos that reached the typical five to six day blastocyst stage used in in vitro...