New Study Shows Much Longer Survival for Heart Transplants Across Species

Discovery Could Eventually Lead To Increased Use of Xenotransplantation

A new immune-suppressing therapy has led to the longest survival yet for a cross-species heart transplant, according to new research conducted in part by researchers at the University of Maryland School of Medicine (UM SOM).

Richard N. Pierson, MD, Professor of Surgery at UM SOM, is a co-author of the study, which involved transplanting pig hearts into baboons. The results could lead to increased use of xenotransplantation, the transplantation of organs from one species to another. Researchers hope this approach could eventually be used in humans, helping the severe organ shortage among patients awaiting transplantation.

The study, which was conducted at the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health, was published yesterday in Nature Communications.

A key problem with using xenotransplantion in humans is that the immune system reacts very strongly, which can cause organ rejection. Scientists have tried modifying the organ donor’s genes and developing novel immune-suppressing drugs for the organ recipients. 

In the current study, scientists developed a novel immune-suppressing drug regimen that includes a key antibody, called anti-CD40 antibody, which may help the organ resist the immune system response. The researchers used pigs that had been genetically modified to have high immune system tolerance and then transplanted hearts from these animals into a group of five baboons. The pig heart did not replace the baboon heart, but was an additional organ. Both the new and original hearts continued to pump blood.

With the new immune-suppressing drugs, the pig hearts survived for up to 945 days in the baboons – much longer than previous pig-to-primate heart transplants. The immune-suppressing drugs played a key role in this.

“This has the potential to really move the field forward,” said Dr. Pierson, who has studied xenotransplantation for three decades. “This new approach clearly made a difference. We obviously have a lot more work to do, but I’m confident that eventually this will be useful to human patients.”

The study’s lead author was Muhammad Mohiuddin, MD, chief of the transplantation section in the Cardiothoracic Surgery Research Program at the NHLBI.

About the University of Maryland School of Medicine

The University of Maryland School of Medicine, chartered in 1807 and as the first public medical school in the United States, continues today as an innovative leader in accelerating innovation and discovery in medicine. The School of Medicine is the founding school of the University of Maryland and is an integral part of the 12-campus University System of Maryland. Located on the University of Maryland’s Baltimore campus, the School of Medicine works closely with the University of Maryland Medical Center and Medical System to provide a research-intensive, academic and clinically based education. With 45 academic departments, centers, programs and institutes and a faculty of more than 3,000 physicians and research scientists, along with more than $400 million in extramural funding, the School is regarded as one of the leading biomedical research institutions in the U.S. with top-tier faculty and programs in cancer, brain science, surgery and transplantation, trauma and emergency medicine, vaccine development and human genomics, among other centers of excellence. The School is not only concerned with the health of the citizens of Maryland and the nation, but also has a global presence, with research and treatment facilities in more than 35 countries around the world.
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