Organ transplantation – doctors transplant pig heart for the first time

In Baltimore, Maryland, USA, patient Dave Bennett received a pig heart for the first time. (imago / ZUMA Wire / University Of Maryland School)

The transplanted heart has started work, the patient is fine, said the US university clinic in a press release. But he’s still a long way from over the mountain. The outcome of the clinical experiment should determine how quickly further xenotransplantation attempts are made.

How is the patient with the new pig heart?

The 57-year-old craftsman David Bennet survived the risky operation three days ago. He was in a life-threatening situation, end-stage heart failure. According to the clinic, the transplantation of a human donor heart was out of the question. Three days after the procedure, he is still connected to a heart-lung machine and ventilated.

How risky was this transplant?

The operation represents an enormous risk for the patient. Whether he will survive it will be seen when the heart-lung machine is switched off shortly. Then the connected pig heart must take over the pumping function. The surgeon in charge had previously tried the technique about 50 times on non-human primates. He said cautiously: “We are thrilled. But we don’t know what will happen tomorrow. ”

Why was a pig’s heart used?

The pig heart is about the same size as a human heart and does exactly the same job. It pumps blood all over the body. In contrast to the kidney or liver, biochemical differences do not play a role in the heart. Other enzymes are often produced in other organs. Different substances are broken down or released.

Why did the pig heart have to be genetically modified?

Without genetic manipulation, the pig heart would have been rejected by the recipient’s immune system. In total, genetic engineers from Revivicor have changed the pig genome in ten places. Four genes have been shut down or inactivated, and six human genes have been incorporated into the pig genome. The change in certain sugars on the cell surface of pig cells is particularly important. The immune system uses this to differentiate its own cells from foreign cells. The pig cells have been disguised, so to speak, so that the human immune system does not recognize the pig cells as foreign and rejects them.

Will more animal organs be transplanted from animals to humans in the future?

Teams from Munich and New York have also developed methods for transplanting pig organs. Pig hearts have already been transplanted into baboons in Munich several times. Bruno Reichart and his team achieved survival times of more than half a year. Other groups were able to change dozens of genes in parallel in laboratory experiments with pig cells. This was achieved through so-called genome editing with the CRISPR / Cas gene scissors. These procedures should also come into medical practice in the next few years.

What are the long-term chances for the first patient?

It is not yet clear whether the patient will survive. The experts will only be able to answer two important questions in a few weeks’ time: Does the pig heart take over the full pumping function when the heart-lung machine is switched off? And can medium and long-term rejection reactions be controlled? If all goes well, the patient needs strong medication for life to slow down his immune system. It is an open question to what extent the patient can lead a normal life outside of the hospital.

Could animal organs alleviate the existing donor organ shortage in the future?

Doctors in the US are very optimistic. The chief medical officer Muhammad Mohiuddin stated: “If that works, there will be an endless supply of these organs for humans.” However, it is not yet possible to say whether this hope is justified. If the first patient feels better in a few weeks, further animal organ transplants will certainly follow.

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