In a world-first, a newly unveiled machine repairs injured human livers and keeps the organ alive outside of the human body for up to a week, showing promise in the treatment of those awaiting life-saving liver transplants around the world.
In the US alone, Columbia Surgery reports that there are nearly 17,000 people awaiting a transplant for a variety of reasons, including when a person’s liver fails due to injury or illness or to treat rare disorders. The procedure removes a diseased or injured liver and replaces it with a healthy liver from a donor, but until now a liver could only survive just a matter of hours outside of the human body. (However, a device unveiled in 2013 showed promise for keeping human livers alive and in perfect condition for at least 24 hours, reported New Scientist at the time.)
Researchers from the University Hospital Zurich, ETH Zurich, Wyss Zurich and the University of Zurich describe their long-term project in Nature Biotechnology, calling the machine a major breakthrough for transplantation medicine.
"The success of this unique perfusion system – developed over a four-year period by a group of surgeons, biologists, and engineers – paves the way for many new applications in transplantation and cancer medicine helping patients with no liver grafts available" explains Professor Pierre-Alain Clavien, Chairman of the Department of Surgery and Transplantation at the University Hospital Zurich (USZ), in a statement.
Currently, donor livers are preserved by first flushing the organ with a cold solution before storing it on ice, which reduced metabolic activity, allowing safe storage for up to 18 hours. Alternatively, human livers may also be kept metabolically active for up to 24 hours by supplying oxygenated fluids and normothermic blood via a machine. Researchers up that limit by sevenfold by mimicking the real-life conditions and environment of a liver inside the human body.
The complex perfusion system connects the liver to a machine that mimics core body functions to repair and successfully store livers. When the project began five years ago, a liver could only be kept on the machine for 12 hours. Now, the machine can repair a preexisting injury, clean fat deposits, and even regenerate partial livers. Injured livers from cadavers that were previously not suitable for transplantation were shown to regain full function when perfused in the new machine for just a few days. Six of the 10 perfused human lives, which were deemed of poor quality and declined for transplantation by all centers in Europe, recovered to full function in just one week.
The machine uses pancreatic hormones, including insulin and glucagon, to control metabolic conditions and works through a "unique dual vascular supply with high-pressure, oxygen-rich arterial blood entering through the hepatic artery and low-pressure, oxygen-reduced portal vein blood draining the abdominal viscera," write the researchers. Additionally, a majority of the livers presented bile production, which is one of the "most convincing indicators of liver viability after transplantation."
The authors are quick to note that several parameters of viability remain difficult to assess and monitor, such as coagulation and the efficiency of intrahepatic bile ducts.
None of the livers have been successfully transplanted into a living human. The researchers say this area is the next target for their study.