A joint team from Korea, the United States, and China has succeeded in creating eggs capable of actual fertilization from human skin cells. It is expected to offer a new alternative for infertile patients for whom in vitro fertilization (IVF) was impossible due to a lack of egg production.
A team led by Shoukhrat Mitalipov, a professor at Oregon Health & Science University in the United States, said it succeeded in fusing the nucleus of a skin cell with an egg whose nucleus had been removed in advance and then fertilizing it with sperm, according to a paper published on the 30th (local time) in the international journal Nature Communications. CHA University and the First Affiliated Hospital of Anhui Medical University in China also took part in the study.
Infertility occurs when eggs or sperm are not properly produced or have functional abnormalities. Hundreds of millions worldwide are known to face infertility issues. According to the Health Insurance Review & Assessment Service (HIRA), the number of infertility patients in Korea reached 240,000 as of 2022.
Infertile couples try in vitro fertilization. Because fertilization occurs in a laboratory dish, it is called the test-tube baby procedure. It induces superovulation in the woman to secure many eggs in advance and selects healthy sperm for fertilization. However, the success rate is only about 32%. Most couples must undergo multiple procedures before achieving pregnancy.
The joint team proposed somatic cell nuclear transfer (SCNT) as an alternative to in vitro fertilization. The method removes the nucleus containing genetic material from a donated egg and inserts the nucleus of an infertile woman's skin cell. This yields an egg that carries the infertile woman's genes.
Somatic cell nuclear transfer faced a challenge. In normal fertilization, the egg and sperm each have 23 chromosomes and together form a zygote with 46 chromosomes. But somatic cells such as skin cells already have 46 chromosomes. If an egg with a skin cell nucleus is fertilized with sperm, it becomes an abnormal zygote with 69 or more chromosomes. While a solution to this was developed in mouse studies, it had not been applied to human cells.
To solve this problem, the researchers reduced the number of chromosomes in the skin cell nucleus by half, to 23, and then transplanted it into a donated egg whose nucleus had been removed. Using this approach, they created a total of 82 somatic cell nuclear transfer eggs and fertilized each with sperm. As a result, about 9% of the zygotes grew to the blastocyst stage on the sixth day after fertilization. The blastocyst stage is a critical point when the embryo completes early development and prepares for implantation. At this stage, embryonic stem cells are produced that grow into all cells and tissues of the human body.
However, most of the zygotes did not develop normally. Even when embryos did develop, chromosomal abnormalities were often found. The research team then halted further culture.
Mitalipov said, "Most of the zygotes did not grow normally after fertilization, and chromosomal abnormalities were found even at the blastocyst stage," and noted, "This study shows the possibility of creating cells close to normal eggs from somatic cells, but we confirmed that many challenges remain in terms of success rate and stability."
The scientific community sees this study as the first to demonstrate the possibility of creating eggs from human cells, potentially serving as an important foundation for future infertility treatment research. However, legal and ethical barriers remain before such possibilities can be applied in clinical practice.
In particular, it is realistically difficult to apply this technology in Korea. Under the Bioethics and Safety Act, it is permitted to create embryos via somatic cell nuclear transfer to obtain stem cells, but implanting them in the uterus to produce a baby is prohibited. Kang Eun-joo, a professor at CHA University and a co-author of the paper, carried out the research in the United States and achieved results, but said the study was not possible in Korea.
Earlier, in 2016, Professor Mitalipov and Professor Kang addressed mutations in mitochondria, the energy-producing organelles in eggs, through somatic cell nuclear transfer. If mitochondria mutate, a baby born later can develop a fatal disease. The team removed the nucleus from a donated egg and inserted the patient's egg nucleus to create an egg with normal mitochondria.
Kang said, "Even though we developed the original technology, while the United States proceeded using our technology, Korea's Bioethics and Safety Act made the research itself impossible," and added, "This study applied a method similar to the original technology in the United States, but the results were technically unstable, so we must begin the research ourselves as soon as possible."
References
Nature Communications (2025), DOI: https://doi.org/10.1038/s41467-025-63454-7
Nature (2016), DOI: https://doi.org/10.1038/nature20592