First-Ever Growth of Human Kidneys Inside Pigs


Researchers have managed to coax human stem cells into forming early-stage human kidneys within pigs, marking the first time a human organ has been successfully generated inside another animal. This groundbreaking advancement in stem cell research holds the promise of bringing us closer to a future where we can grow human organs in pigs, potentially addressing the critical shortage of organs available for transplantation.

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According to developmental biologist Juan Carlos Izpisúa Belmonte of Altos Labs, who has previously experimented with growing human stem cells in different species, this development signifies a significant leap forward in the field. While the kidneys generated in this study were not intended for immediate transplantation into patients, Izpisúa Belmonte notes that it hints at the potential for achieving the ultimate goal of producing human organs in other mammals.

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In efforts to overcome the shortage of human organs for transplantation, transplant surgeons have previously implanted pig kidneys and hearts into a few individuals in experimental procedures. However, these pig organs were genetically modified to reduce the risk of rejection by human recipients, still necessitating lifelong immune-suppressing drugs. Growing human organs within pigs presents an appealing alternative, as these organs could be derived from a patient’s own stem cells, avoiding immune rejection issues.

                                          -p-Progress has already been made in this direction, with researchers like regenerative cell biologist Mary Garry and her colleagues inserting human stem cells into genetically altered pig embryos. These embryos, when implanted into surrogate mother pigs, used the human cells to develop certain tissues, such as human muscle and blood vessel linings. However, the challenge lies in inducing these embryos to generate complete organs with multiple cell types.

A team led by stem cell biologists Liangxue Lai, Zhen Dai, Miguel Esteban, and Guangjin Pan at the Guangzhou Institute of Biomedicine and Health identified two key obstacles in previous attempts. Firstly, human stem cells were not competitive enough with their pig cell counterparts, which was addressed by genetically enhancing the human cells. Secondly, the human cells were developmentally ahead of the pig cells, and a new culture medium was developed to synchronize their development, allowing better integration with pig cells.

These upgraded human stem cells were then introduced into pig embryos genetically engineered to lack kidney growth ability. After about a month of development within surrogate mother pigs, the researchers discovered primordial human kidneys in some of the embryos, with up to 65% of the cells in these organs being human. This suggests that the human stem cells successfully gave rise to kidney cells within the pig environment.

While this achievement marks a significant milestone, scientists must tackle several challenges before these organs can be considered suitable for transplantation into patients. The kidneys generated in this study were temporary and functional for only a few weeks early in development, whereas transplantable organs must function throughout an individual’s life. Additionally, efforts are required to increase the percentage of human cells in the organs to prevent immune rejection.

                            The ethical implications of growing human organs in pigs also loom large. There is a concern that human cells could migrate to the animals’ brains or reproductive systems, potentially altering their mental capabilities or leading to the development of human genes in their sperm or eggs. Researchers are exploring additional genetic modifications to prevent such infiltration.

While the approach taken in this study to fortify stem cells before insertion into embryos is considered promising, questions remain about the quality of the human kidney cells produced. Researchers are eager to determine whether they can produce adult-stage kidneys, which is a key milestone on the path to successful transplantation.

Mary Garry, who co-founded a company focused on producing human organs in pigs, emphasizes the need for further analysis of the human cells within the kidneys and an evaluation of the organs’ functionality. It is crucial to ensure that the developing kidneys are genuinely human and that the pigs survive through birth and beyond.

Miguel Esteban, one of the researchers involved in the study, anticipates allowing similar embryos with human stem cells to develop for a longer duration to ascertain whether adult-stage kidneys can be achieved. While the timeline for producing transplantation-ready organs remains uncertain, Esteban is cautiously optimistic, believing that within a decade, this groundbreaking research may become a reality.