Keeping hearts alive outside the body
Can we keep a donated heart alive for longer? And if we can, could we treat it outside the body? These are the questions Mats Vervoorn looked into during his PhD. Donor hearts are rare. If we can keep them working longer outside the body with a machine, more people could get the help they need. Mats found ways to improve how we preserve hearts using machine perfusion and even started exploring if we can treat hearts while they're outside the body. He successfully defended his thesis on July 15, 2025.
Every year, thousands of people with severe heart failure need a heart transplant, but only a few patients receive one. One reason is that donor hearts don’t last long using traditional storage methods after they’re taken out. During his PhD, Mats Vervoorn worked on improving a perfusion machine, also called ‘heart-in-a-box’. This machine gives the heart oxygen and nutrients so it keeps beating. At UMC Utrecht, this method is already used for hearts from donors whose hearts have stopped (DCD donors). Although this saves many hearts, there’s still more time to gain.
More time, more hearts
“Perfusion is already happening in the clinic”, Mats says. “But we’re still limited in how long the heart can stay outside the body. If we can stretch that time, we can improve matching between donor and recipient, even from donors further away. And we might be able to use donor hearts that are now being rejected.”
Mats developed a new protocol to protect the heart during perfusion at body temperature and keep the heart alive for a longer time. To test this, Mats used hearts from pigs that were slaughtered for human consumption. These hearts had already been without blood and oxygen in both warm and cold conditions due to the slaughtering process and transportation to the lab, making them especially challenging keep alive.
The hearts kept working well throughout the entire perfusion time
Keeping a donor heart alive
To develop the protocol, Mats and his colleagues had to make small but important changes to a conventional perfusion setup. “We experimented with a lot of variables”, Mats says. “We lowered the temperature during reperfusion slightly, added substances to reduce inflammation and oxidative stress, and adjusted the mix of nutrients to better support the heart’s metabolism”, Mats explains. “We even added a filter to eliminate harmful substances like the kidneys normally would do.” These changes helped protect the hearts from damage when the blood flow started again and during the time the hearts were connected to the machine. “In the end, the hearts looked better and kept working well throughout the entire perfusion time”, he says.
As a result, the hearts could be kept alive and beating for up to nine hours, without getting worse in quality and function. “That’s a big step”, Mats says. “It shows that extended preservation is possible, even with lower-quality hearts, such as hearts harvested in the slaughterhouse.”
Treating hearts outside of the body
“If we can keep the heart alive outside the body, we could also start treating it”, Mats says. His PhD was part of the cardiovascular moonshot consortium of RegMedXB, which aims to develop regenerative treatments for the heart. “The idea is that gene therapy, stem cells, or other targeted treatments could be delivered directly to the beating heart during isolated organ perfusion without affecting other organs in the body”, Mats explains. “Machine perfusion makes that possible. That opens up a whole new world of therapeutic options.”
Valves that grow
After his PhD, Mats is staying in the field. As a postdoc, he will be working on homografts: donor heart valves used in children. “Donor valves need to be frozen before surgery”, he explains. “But the current preservation process kills the cells, so the valve can’t grow anymore once implanted.” Because the valve doesn’t grow with the child, multiple surgeries are often needed.
Together with Marijn Peters and Bram van Wijk, Mats will work on better ways to preserve the tissue and keep it alive. “We also want to treat the valves with gene therapy to help the body accept them. That way, the immune system won’t see them as foreign”, Mats explains. “The dream is for the valves to grow with the child and be seen as part of the body.”
They said this might be the beginning of organ banking
Piece of a puzzle
Looking back, Mats is proud of what his project accomplished. “In our field, it was really seen as a step forward”, he says. The research was published in top journals, and even received its own editorial. “They said this might be the beginning of organ banking. That was really special to see.” Still, Mats is realistic. “We didn’t change transplantation overnight. But we found a piece of a puzzle. And that’s what science is about.”