Medical breakthrough: Researchers grow human kidney cells in pigs

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Scientists have grown kidney tissue containing mainly human cells in pig embryos. Organs grown in this way can later become donor organs.

To do this, the researchers switched off two genes in the pig embryos that are important for kidney development. Kidney tissue from human stem cells could then grow into this organ opening. The group led by Liangxue Lai of the Institutes of Biomedicine and Health in Guangzhou (China) presented their approach Thursday in the journal Cell Stem Cell.

“Rat organs have been produced in mice and mouse organs in rats, but previous attempts to grow human organs in pigs have been unsuccessful,” Lai explains. The problem is the same as with organ donation, where donor and recipient are not a good match: the recipient’s body then rejects the organ because the immune system recognizes it as foreign tissue and initiates defensive measures. In addition, the pig cells in the embryo can assert themselves better than the human cells. Both cell types also have different needs in order to thrive.

Kidney tissue grows from human stem cells

Using gene scissors, the researchers removed the genes SIX1 and SALL1, which are necessary for the development of the kidneys, from a single-cell pig embryo. As a result, the embryo did not develop pig kidneys, a vacancy or niche was created. Human stem cells from umbilical cord blood were injected into the embryo, from which all kinds of human cells can arise. In the created niche, they could develop into kidney tissue largely without competition.

The human stem cells were specially prepared beforehand. On the one hand, genetic manipulation caused the MYCN and BCL2 genes to become increasingly activated. They ensure better cell survival. On the other hand, the researchers placed the stem cells in a recently developed nutrient medium, transferring the stem cells to earlier stages of development. In this way, they resemble early human embryonic cells.

Mixture of human and pig cells

The scientists planted the pig embryos in sows, where they were allowed to develop until day 25 or 28. There were some embryos in which a kidney composed mainly of human cells had developed normally compared to untreated pig embryos. However, the procedure still needs improvement: “The overall proportion of degenerating pig embryos is high and it needs to be assessed what this is related to,” the study authors write.

Even the well-developed kidneys still contain over a third of the cells of pigs, which can lead to immune reactions in the human organism during organ transplantation. “Since organs are not just made up of a single cell line, we would probably have to manipulate the pigs in a much more complex way to get an organ in which everything is human,” says study co-author Miguel Esteban of the Guangzhou Institutes of Science. Biomedicine and health.

“It is not objectionable to breed animals to save human lives”

Medical ethicist Wolfram Henn of the German Ethics Council positively emphasizes in his assessment of the study that umbilical cord blood was used as the basis for human stem cells. This avoids the use of human embryos. The procedure also offers the prospect of using the blood stem cells of a patient who is dependent on a donor organ as the basis for culturing the organ. Because the cells used then come from the patient himself, rejection reactions should not usually occur. Overall, he considers the approach of the researchers reasonable and responsible.

Henn also considers the process ethical in terms of animal welfare: “We breed animals to eat them, so it is not objectionable to breed animals to save human lives.” Henn believes it is particularly important to modernize German legislation, as the Embryo Protection Act is now over thirty years old. Many of the procedures used today did not exist back then, so the legal basis for research as described in the study had to be revised, the medical ethicist demanded. (SDA)

Source: Blick