Scientists in China have achieved a breakthrough in organ bioengineering by successfully growing kidneys with human cells in pig embryos. This is the first time that a solid humanized organ has been grown in another species, and it could pave the way for future solutions to organ donation shortages.
How the human-pig hybrids were created
The researchers from the Guangzhou Institutes of Biomedicine and Health used CRISPR gene editing to delete two genes essential for kidney formation in pig embryos, creating a niche that could be filled by human cells. They then added specially prepared human pluripotent stem cells, which have the potential to develop into any cell type, to the pig embryos. The embryos were then cultured in test tubes containing substances that nourished both the human and pig cells, before being implanted into surrogate sows.
What the results showed
The pregnancies were terminated after 25 and 28 days to assess how the experiment had worked. Five embryos selected for analysis were found to have functionally normal kidneys for their stage of development, with between 50 and 60 percent human cells. The human cells were mostly localized to the kidneys, while the rest of the embryo was comprised of pig cells. The researchers also found only very few human neural cells in the brain and spinal cord, which is an ethical concern for creating hybrid animals.
Why this is a significant achievement
Previous attempts to grow human organs in pigs have not succeeded, because pig cells tend to outcompete human cells during development. The new approach improves the integration of human cells into recipient tissues and allows the growth of human organs in pigs. This could have implications for understanding organ development, modeling kidney diseases, screening drugs, and potentially generating transplantable organs.
What are the challenges and limitations
The kidneys grown in this study were not entirely human, as they included vasculature and nerves made mostly from pig cells. This means they could not be used for transplantation in their current form. It is also not clear whether the challenge of making a wholly human organ would be achievable with current genetic engineering techniques. Moreover, there are ethical issues involved in creating animal-human hybrids, such as the potential impact on animal welfare, the risk of cross-species infections, and the moral status of the chimeric animals.
How this relates to other organoid research
Organoids are miniature organ-like structures that can be grown from stem cells in a dish. They have been used to model various kidney diseases, such as polycystic kidney disease, congenital nephrotic syndrome, renal cell carcinoma, and viral infections. They can also be used to test drugs and study kidney development. However, organoids are not fully functional or anatomically correct, and they have limitations in size, vascularization, and maturation. Therefore, growing humanized organs in animals could offer a complementary approach to organoid research.