Pig’s heart transplantation into Humans

Subject – Science and Tech

Context – US surgeons have successfully implanted a heart from a genetically modified pig in a 57-year-old man

Concept –

US surgeons have successfully implanted a heart from a genetically modified pig in a 57-year-old man, a medical first that could one day help solve the chronic shortage of organ donations.
While it’s too soon to know if the operation really will work, it marks a step in the decades-long quest to one day use animal organs for life-saving transplants.
But prior attempts at such transplants — or xenotransplantation — have failed, largely because patients’ bodies rapidly rejected the animal organ. Notably, in 1984, Baby Fae, a dying infant, lived 21 days with a baboon heart.
The difference this time: The Maryland surgeons used a heart from a pig that had undergone gene-editing to remove a sugar in its cells that’s responsible for that hyper-fast organ rejection. Several biotech companies are developing pig organs for human transplant.
The Food and Drug Administration, which oversees such experiments, allowed the surgery under what’s called a “compassionate use” emergency authorization, available when a patient with a life-threatening condition has no other options.
Over the years, scientists have turned from primates to pigs, tinkering with their genes.

Xenotransplantation

Xenotransplantation, or heterologous transplant, is the transplantation of living cells, tissues or organs from one species to another.
Such cells, tissues or organs are called xenografts or xenotransplants.
It is contrasted with allotransplantation (from other individual of same species), syngeneic transplantation or isotransplantation (grafts transplanted between two genetically identical individuals of the same species) and autotransplantation (from one part of the body to another in the same person).
Xenotransplantation of human tumor cells into immunocompromised mice is a research technique frequently used in pre-clinical oncology research.
Human xenotransplantation offers a potential treatment for end-stage organ failure, a significant health problem in parts of the industrialized world.

Animal-to-human transplants history

The first attempts at animal-to-human transplants were made in 1838, when the cornea of a pig was transplanted into a human.
Between 1902 and 1923, organs from pigs, goats, sheep, and monkeys were used in unsuccessful transplantation attempts.
From 1963 onward, researchers attempted organ transplantation from chimpanzees, baboons and pigs.
In 1984, a two-week-old baby in the United States received a baboon’s heart, but died within three weeks.
For fear of transmission of viruses from animals to humans, xenotransplantation has for long been an area that governments and doctors have treated with caution.

Why pigs in particular?

A pig’s genetic make-up and internal organs are similar to a human’s. Its weight, the tendency to become obese, lipids, arterial pressure, heart rate, renal function, electrolyte balance, and digestive system match those in the human body.
The problem is that the rejection rate is higher in a pig-to-human transplant than in a human-to-human transplant. ‘Rejection’ is what happens when the human body’s immune system starts working against any foreign organ.
In a human-to-human transplant, immunosuppressants help trick the body into accepting the foreign organ as its own. But immune suppressants have failed to work in animal-to-human transplants.
There are certain enzymes, proteins and amino acids in pigs that are different from those in humans. These are substances against which the human body will produce antibodies and reject the organ. It is called antigenicity. The lower the antigenicity, the better.