In-vitro gametogenesis (IVG) is the creation of eggs or sperm from other cell types, such as skin cells. Two competing methods are being pursued: IVG proper, which transforms skin cells into stem cells that are then coaxed into becoming egg cells; and somatic-cell nuclear transfer (SCNT), the technique used to clone Dolly the sheep, adapted for reproductive purposes.
Shoukhrat Mitalipov of Oregon Health & Science University published results in Nature Communications (2025) showing that his team had created fertilisable human eggs from skin cells using a modified SCNT method. They removed the nuclei from donated egg cells, fused them with skin cells from other volunteers, and then used a novel form of cell division they call "mitomeiosis" to shed half the chromosomes—reducing the count from the 46 found in normal cells to the 23 required for a fertilisable egg.
The team created 82 SCNT eggs this way and fertilised them with sperm. Five developed to the blastocyst stage before the experiment was terminated. A significant limitation remains: the process has no control over which chromosomes are shed, so on average only about half the chromosome pairs match up correctly.
Hayashi Katsuhiko, a geneticist at the University of Osaka, is a pioneer of the stem-cell route to IVG. This approach has so far succeeded only in mice. At least one startup, Conception Bio, is also pursuing IVG through the stem-cell method.
Both approaches remain far from clinical use. Egg donation for the SCNT method requires a complex and invasive procedure, and any reproductive application would face years of ethical and regulatory scrutiny.
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