Chinese team grows humanised kidneys in pigs for first time, raising transplant hopes – and ethical concerns

Scientists in China grow organs inside pig embryos, offering potentially ‘groundbreaking solution’ as patients face donor shortage
Researchers use gene-editing tool CRISPR to allow human cells to grow, but results raise questions about ethics

Science

Victoria Bela

Published: 8:31pm, 8 Sep 2023

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In a world first, a team of scientists in China has grown kidneys that are mostly human inside pig embryos – presenting an “attractive alternative” to transplant organs that are in short supply, but raising ethical concerns about potential risks.

Researchers at the Chinese Academy of Sciences Guangzhou Institutes of Biomedicine and Health published their findings in the journal Cell Stem Cell on Thursday, showing the potential to grow organs for transplant and research in pigs.

According to China Science Net, it is the first time a solid human organ has been grown inside another species.

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Kidneys are one of the most commonly transplanted organs. However, donor kidney shortages make it difficult to provide healthy organs to recipients who need them.

Growing human organs in large mammal embryos “would be a groundbreaking solution” to this problem, according to the paper.

Lai Liangxue, the study’s corresponding author, told Science Net his team’s method of inserting human stem cells into recipient tissue helped improve the cultivation of human stem cells within the embryos.

Out of more than 1,800 embryos involved in the study, five embryos succeeded in growing without degenerating, and these embryos grew kidneys containing 50 to 60 per cent human cells. Due to ethical considerations and the risk of embryonic degradation, gestation was stopped at 28 days, according to the paper.

They used the gene-editing tool CRISPR to target two genes that are part of kidney development to limit pig cell growth. Dai Zhen, one of the study authors, said doing this created a “vacancy in the pig embryo” that allowed human cells to grow in its place, according to Science Net.

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A major concern in the creation of these interspecies chimeric embryos – embryos that contain cells of both human and pig origin – is the possibility of human cells contributing to the pig cell lineage, according to the paper.

Human cells were found in the brain and spinal cord of the embryos, but none were found around the genital ridge, suggesting the human cells did not differentiate into reproductive cells, Dai said.

Darius Widera, a professor of stem cell biology at the University of Reading in Britain, said in a Science Media Centre briefing on Thursday that the paper was a “clear milestone”, but the discovery of human cells in the embryos’ brains raised “important ethical questions”.

According to the study, this could be overcome by eliminating genes responsible for the development of certain cell lineages, but this could also affect the growth of the kidneys.

The paper identified other challenges, such as the large number of embryos that degenerated during the experiments, the potential for organ rejection because of differing cell types and possible issues that could arise if the embryos had a longer gestation time.

Pig kidney works in brain-dead man’s body for over a month

There have been other attempts to fix the organ shortage problem, such as xenotransplantation, or transplanting an organ from one species to another. Genetic modification can be done to stop the expression of genes that cause rejection in xenotransplantation, according to New York University Langone Health.

Last month, surgeons at NYU Langone successfully transplanted a pig kidney with only one genetic modification into a brain-dead patient, and the organ continued to function 32 days after the procedure.

The Chinese team’s study said xenotransplantation had “remarkable short-term success”, but genetic modifications had still not removed the potential for immune rejection.