Researchers have successfully grown humanized kidneys inside pigs, raising hopes for a future where human organs can be cultivated within animals.
This breakthrough can potentially transform the field of organ transplantation, addressing the chronic shortage of available organs for those in need.
Humanized Kidneys Grown from Pigs
The Guardian reports that scientists did this by creating human-pig chimeric embryos-tiny biological hybrids containing a mix of human and pig cells. This novel approach resulted in the development of kidneys predominantly composed of human cells.
However, these humanized kidneys were not entirely human, as they retained some pig vasculature and nerves. This crucial distinction means that, in their current state, these kidneys cannot be transplanted into humans.
The challenge is transforming them into fully functional human organs, which might take many more years of research and genetic engineering.
Genetic Engineering
Previous attempts to create human-pig hybrids had faltered because pig cells tended to dominate the development process, leaving the resulting chimera almost entirely pig.
This time, researchers took a different approach. They genetically engineered a single-cell pig embryo by deactivating two genes crucial for kidney development. This created a niche within the embryo where human embryonic stem cells could integrate, resulting in humanized kidneys.
These chimeric embryos were transferred into 13 surrogate pig mothers during the study. The embryos were extracted and examined after a gestation period of either 25 or 28 days. The findings were promising.
The developing kidneys displayed structural normality for their stage and consisted of 50-60% human cells. In addition, some human neural cells were identified in the brain and spinal cord.
Ethical and Legal Hurdles
While this research opens exciting possibilities, it also raises serious ethical questions.
The Guardian notes that human cells in these hybrid embryos' brain and central nervous system are a significant concern. This issue is one of the reasons for strict legal restrictions on such research in many countries.
In the UK, human embryonic cells can be introduced into animal embryos, but these embryos cannot be implanted into animal mothers for further development.
The Future of Xenotransplantation
One of the critical challenges in xenotransplantation has been the human immune system's rejection of pig organs.
Scientists have genetically modified pig genes to address this, turning off some that trigger rejection and adding others that protect the organs from immune attacks.
These modifications have significantly improved organ survival rates in animal experiments, even leading to the first trial of a pig heart transplant into a human.
David Bennett, a 57-year-old man suffering from terminal heart failure, became the first human to get a genetically modified pig heart. Bennett survived for two months following the surgery in the US.
What's Next?
It is important to note that the road to fully functional human organs grown in pigs is long and challenging. Integrating human nerves and vasculature into these organs without developing a humanized brain remains a complex puzzle.
Prof. Dusko Ilic, a stem cell scientist at King's College London, aptly captures the sentiment: "As the authors admitted, there are plenty of challenges. Will this approach prove to be the ultimate solution? Only time holds the answer."
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