[News Terms] Human Kidney Grown Inside Pig Body: 'Chimera Organ'

Interest in 'chimera' organs has been sparked following the announcement by a Chinese research team that they successfully grew human kidneys inside a pig's body.

Creating Human-Pig Chimera Embryos, Surrogate Mother Transplantation, and Growth Process
[Provided by Wang, Xie, Li, Li, and Zhang et al./Cell Stem Cell]

The term chimera originates from the Greek word Khimaira, meaning a goat, and is the English pronunciation of the Greek word. It is derived from the chimera monster in Greek and Roman mythology. The chimera described in mythology is a three-headed monster composed of a lion at the front, a goat's body, and a snake at the rear. Similarly, chimera technology involves combining genes from different species. A representative chimera plant is the pomato, created by grafting potatoes and tomatoes using cell fusion technology.

In genetics, chimera research is also applied by injecting human stem cells (cells capable of developing into any organ) into animal embryos. If successful in developing chimera organs through such experiments, it could resolve the global shortage of transplant organs. However, the challenge lies in how to avoid the ethical controversies that inevitably accompany this type of research.

For example, in 2021, a joint research team led by Professor Juan Belmonte of the Salk Institute in the United States and Professor Ji Weizhi of Kunming University of Science and Technology in China created a chimera by injecting human stem cells into monkey embryos and observed their growth process. Their results were published in the international journal Cell. At that time, they faced criticism that "there is doubt about whether the embryo is human or not, which could lead to ethical and legal issues." In 2002, South Korea also intensified bioethical debates by creating a 'chimera mouse' through transplanting human embryonic stem cells into mice.

Meanwhile, Dr. Liang Xue's team at the Guangzhou Institute of Biomedicine and Health (GIBH), Chinese Academy of Sciences (CAS), announced on the 7th in the scientific journal Cell Stem Cell that they created human-pig chimera embryos, implanted them into surrogate pigs, and after 28 days, confirmed that the humanized kidneys formed normal structures and nephrons. While human tissues such as blood or skeletal muscle have previously been grown inside pigs, this is the first time that a humanized solid organ has been grown inside another species' body.