[Un article de The Conversation écrit par
Coralie Thieulin – Enseignant chercheur en physique à l”ECE,
docteure en biophysique, ECE Paris]
The term xenograft refers to the transplantation of a tissue or organ from a different species than the recipient, for example, from a pig to a human. It is distinguished from allograft, between two humans, and autograft, using the patient's own tissues. The goal is to address the chronic shortage of human organs available for transplantation, while ensuring graft compatibility and safety.
In France, at 1er January 2025, 22,585 patients were registered on the national transplant waiting list, including 11,666 on the active list. In 2024, 852 patients died while waiting for a transplant.
Pig skin, a pioneer of xenografts
It was the skin that first led the way. Since the 1960s, pigskin has been used as a temporary biological dressing for severe burn victims. Its structure and thickness are surprisingly close to those of human skin, providing good adhesion and effective protection against infections and dehydration.
Unlike other animals (cow, sheep, rabbit), pig skin has a collagen network (structural protein present in connective tissue and responsible for the resistance and elasticity of tissues) and a cell density similar to those of humans, limiting immediate rejection reactions. However, these transplants are only temporary: the immune system ends up destroying them. However, they offer temporary protection before an autograft or a human transplant.
A striking biological proximity
Beyond the skin, the pig shares many physiological points with humans: size of organs, heart rate, blood pressure, plasma composition, even metabolism. The heart of an adult pig, for example, has dimensions close to that of a human, making it a natural candidate for transplants.
Other species, such as non-human primates, have even greater genetic proximity, but their use raises much heavier ethical and health questions, not to mention their slow reproduction and protected status.
An animal compatible with modern medicine
On the contrary, pigs are easy to raise, reach adult size quickly, and their organs can be obtained under controlled sanitary conditions. Genetically modified lines, such as those developed by the American company Revivicor, are now devoid of certain genes responsible for hyperacute rejection, which makes their organs more “compatible” with the human immune system.
The researchers also removed “dormant” viruses (which do not activate) present in the pig genome, reducing the risk of transmission of infectious agents to humans.
From biological dressing to organ transplant
After the skin, researchers are turning to the kidneys, the heart, the liver and even the pancreas. In 2024, patients have survived several weeks with a genetically modified pig heart, a feat long considered impossible. Trials have also been carried out with pig kidneys, notably in brain dead patients or, more recently, in a living patient. On the other hand, research on the liver and pancreas is still at the preclinical stage, carried out only in animals. These advances are not only symbolic: the global shortage of human donors is pushing medicine to explore realistic alternatives.
However, the immunological challenge remains immense – even genetically modified, porcine organs can be rejected by the human immune system – as do the ethical issues linked in particular to animal welfare.
The pig emerged not by chance, but because it represents a compromise between biological proximity, feasibility and social acceptability. If trials confirm the safety and durability of grafts, pigs could soon become an unexpected but essential ally in human medicine.
With an unwavering passion for local news, Christopher leads our editorial team with integrity and dedication. With over 20 years’ experience, he is the backbone of Wouldsayso, ensuring that we stay true to our mission to inform.
