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Explained: From pig to human, the heart transplant in US man offers hope amid organ shortage

Explained: From pig to human, the heart transplant in US man offers hope amid organ shortage

Explained: From pig to human, the heart transplant in US man offers hope amid organ shortage
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By CNBCTV18.com Jan 11, 2022 1:52 PM IST (Published)

A pig's heart has been successfully transplanted into a patient by surgeons at the University of Maryland Medical Center. This brings the world a step closer to solving the organ shortage crisis. While the transplant of organs from other species into humans – xenotransplantation – has a long history, most of the research had been focused on primates before. 

Surgeons in the US have successfully transplanted a pig’s heart into a patient at the University of Maryland Medical Center. The patient was ineligible for heart transplants and had no other alternatives. The highly experimental procedure appears successful for now.

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"This was a breakthrough surgery and brings us one step closer to solving the organ shortage crisis," said Dr Bartley Griffith, who surgically transplanted the pig heart, to AFP.

“It was either die or do this transplant. I want to live. I know it's a shot in the dark, but it's my last choice,” 57-year-old David Bennett told AP a day before his surgery.

What is special about this surgery?

The surgery is a watershed moment in the field of organ transplantation. It is the first successful heart transplant of a pig heart into a human. While the transplant of organs from other species into humans – xenotransplantation – has a long history, most of the research had been focused on primates before.

Attempts were rarely successful either. Baby Fae, a dying infant, had received a baboon heart but the new organ could only support her for 21 days.

But the Bennett surgery adds one more technological marvel to the mix – gene editing. The pig whose heart Bennett now sports was specifically gene-edited to be more compatible with the human body. A total of 10 genes were edited by the Virginia-based biotech firm Revivicor. One gene responsible for excessive growth of pig heart tissue was removed as well as three other genes that would lead to rejection of the organ were also removed. Six genes that govern organ acceptance in the human body were added.

Bennett was put on standard immuno-suppressants to ensure that his immune system did not attack the new organ as well as a new experimental drug developed by Kiniksa Pharmaceuticals. The company also developed a new perfusion device that preserved the pig’s heart until the day of surgery.

"The successful procedure provided valuable information to help the medical community improve this potentially life-saving method in future patients," said Dr Muhammad Mohiuddin, co-founder of the University of Maryland’s xenotransplantation program, who also developed the experimental drug produced by Kiniksa.

"We are proceeding cautiously, but we are also optimistic that this first-in-the-world surgery will provide an important new option for patients in the future,” Dr Griffith added.

What is a heart transplant?

A heart transplant is a surgical procedure where diseased and failing hearts are replaced with healthier hearts from donors. The surgery is only restricted to those whose conditions do not improve with any other treatment and usually as a last resort.

A heart can become diseased or start to fail due to various medical conditions including congenital defects. In order to become eligible for a heart transplant, patients must meet a strict set of criteria including being healthy enough to undergo surgery and post-transplant treatments, being under 69 years of age, having expected mortality within the next year, do not have any serious ailments or infections including kidney and liver diseases.

The major risk associated with heart transplants is the fact that the newly transplanted heart is rejected by the body. Since the donor heart is a ‘foreign body’, the transplantee’s immune system may attack the heart and lead to the body ‘rejecting’ the organ. The issue is common with almost all major organ donations.

“Your immune system may see your donor heart as a foreign object and try to reject it, which can damage the heart. Every heart transplant recipient receives medication to prevent rejection (immunosuppressants), and as a result, the rate of rejection continues to decrease. Sometimes, a change in medication will halt rejection if it occurs,” explains Mayo Clinic.

Rejection is the main cause of a shortened life span even after a successful heart transplant. While globally, the survival rate of patients after one year of surgery is between 85-90 percent, the survival rate drops considerably as time passes by. One 2004 study estimated that the survival rate after 10 years was only 57 percent. While the lower-end of those figures have climbed significantly in the nearly two decades that have passed since the study was published, organ rejection still remains one of the key concerns with heart transplants.

The world is suffering from a chronic shortage of donor organs. Around 107,000 individuals are currently on a waiting list for a life-saving organ in the US, and it is estimated by experts that lakhs of people die in India while waiting for organ donation.

While almost anyone can donate their organs, organ donation in India is particularly low standing at only 0.01 percent, according to a WHO report. The low rate of organ donation is due to a mix of religious beliefs and a lack of awareness. But even with a much higher rate of organ donation, the need for organs from patients of all kinds may not necessarily be met successfully.

It is for that reason that newer technologies like xenotransplantation and the development of artificial organs can stem the gap between today and the next breakthrough developments as scientists attempt to grow organs through stem cells in labs, tailor-made for each patient. But while it is unknown when such lab-grown organs will be actually feasible for real organ transplantation, thousands of individuals continue to die each year waiting to move up on a list to receive organs.

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