Week-long storage boosts time organs are usable and distances over which they can be moved

Human livers from organ donors can now be preserved for a week, researchers have revealed, a dramatic improvement on previous techniques, which could only keep the organs usable for a matter of hours.

The technology could boost the number of livers available for transplantation and offer new approaches to treating diseases such as liver cancer.

In 2018-19 1,010 liver transplants were carried out. At the end of March 2019 there were 432 people waiting for the procedure. While about 60% of those in need receive a liver within six months, others face waits of two or more years. Some die before a liver can be transplanted.

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Livers are typically only stored for about nine to 12 hours on ice before transplant.

In 2018 researchers in the UK published a report on system that allows livers to be kept at body temperature for 24 hours, a move that the lead author said at the time “improved both the transplant success rate as well as the number of livers available for transplant”.

Now experts have pushed such an approach even further, revealing a system that allows human livers to be stored for a week just below body temperature. “This is a different type of machine that we [had] to develop to reach seven days,” said Prof Pierre-Alain Clavien, co-author of the research from University Hospital Zurich.

The week-long storage, the researchers say, would not only increase the distance over which organs can be transported, but offers another crucial advantage: it gives damaged livers more time to repair themselves, boosting the number of livers that could be used for transplant, while allowing doctors to reject those that are unsuitable.

“We know from operations on patients and others that the liver needs a week to fully regenerate,” said Clavien.

Writing in the journal Nature Biotechnology, Clavien and colleagues report how they engineered a machine that keeps the liver alive and well by performing similar roles as the human body, including pumping blood through the organ and introducing nutrients and hormones such as insulin.

Clavien said the system also removed waste products from the blood, allowing it to be cycled through the organ, and regulated levels of oxygen and blood pressure while the organ itself was moved rhythmically to mimic breathing.

The team initially developed the system using pig livers and carried out three liver transplants on the animals using livers that had been stored for a week. A few hours after transplantation, the team found no difference in the function or tissues of the livers compared with livers stored for just a few hours.

The approach was then tweaked and tested on 10 human livers that had been stored traditionally but turned down for transplantation due to their poor quality.

The team found that all 10 livers lost weight during the course of the week and four deteriorated. However, six livers showed improvements and at the end of seven days were deemed suitable for transplantation.

The study has limitations, including that some aspects of liver function can only be assessed many months after transplantation.

However, Clavien said the system would be used for livers initially stored on ice but deemed too poor quality for immediate transplantation, and that in future it may also be used to boost the quality of marginal livers. Transplants in humans using the approach were in the offing, he said.

The system could also offer new approaches to tackling a range of diseases, the researchers say. For example, a patient with liver cancer could have a healthy section of their liver removed, have it grown using the machine, and then reimplanted with the remaining cancerous liver removed.