A Chinese team has grown, for the first time in the world, early kidneys from human stem cells inside pig embryos. The advance that brings pig-grown human organs closer to reality will open an exciting avenue for kidney transplants and a new window for studying human kidney development, according to a study published on Thursday in the journal Cell Stem Cell. Scientists from Guangzhou Institutes of Biomedicine and Health under the Chinese Academy of Sciences used a gene-editing tool to engineer certain genes in human induced pluripotent stem cells (IPSCs) to strengthen their capability to gain a foothold and form kidneys in pig embryos that are genetically modified to lack the ability to grow a kidney. IPSCs are a type of stem cells derived from adult skin or blood cells and reprogrammed back into an embryonic-like state that enables the development of any type of human cell needed for therapeutic purposes. The study revealed that the researchers finally harvested five embryos with organized human-pig chimeric middle-stage kidney structures within 28 days and those human donor cells could differentiate into functional cells. The proportion of human cells in the chimeric kidneys reached up to 70 percent, and the proportion of human cell contribution in the formation of mesonephric tubules reached a maximum of 58 percent, according to the paper. The gestation was terminated within 3 to 4 weeks in accordance with current ethical rules. This study demonstrates proof-of-principle of the possibility of generating a humanized primordial organ in pigs, offering an attractive potential alternative to help overcome the shortage of human organs for transplantation. The results describe “pioneering steps in a new approach to organ bioengineering using pigs as incubators for growing and cultivating human organs,” said Dusko Ilic, a peer-reviewer from King’s College London. “In the future, an optimised version of this technology could address the current shortage of compatible donors for kidney transplantation,” said Darius Widera, a professor with University of Reading.