Organ donation and new alternatives
June 4, 2021
Researchers are developing ways to fix a shortfall in organ donations. Artificial organs or those taken from nonhuman animals, such as pigs and cows, could be part of the solution.
Which organs are we talking about?
Taking Germany as an example, doctors performed 142,584 organ transplants from 1963 through 2020. Those have included:
- 90,642 kidney transplants
- 27,095 liver transplants
- 13,773 heart transplants
- 6,960 lung transplants
- 4,114 pancreas transplants
Worldwide estimates suggest that more than 153,000 transplants are performed every year — 17.5 transplants per hour.
Surgeons in the United States became the first in the world to conduct a fully successful organ transplantation in 1954. It was a kidney transplant.
Today, kidneys are among the most "in demand" organs.
The artificial heart
In 1969, Domingo Liotta, a heart surgeon practicing at the Texas Heart Institute in the United States developed the first artificial heart.
It was given to a 47-year-old patient and replaced with a healthy human heart after 65 hours. But the patient died shortly thereafter.
More than 50 years later, surgeons still don't use artificial hearts as permanent replacements for human hearts. But artificial hearts can be used temporarily until they find a donated, natural heart.
People can wait up to two years for a donated heart. An artificial heart can support their natural heart while they wait. But there are risks, too.
An artificial heart uses a pump system that is connected to the patient's body with a cable. If germs get into the system, they can cause serious infections. During the transplant surgery itself, internal bleeding can occur, and that can lead to a risk of stroke.
Researchers have yet to develop an artificial heart that works as well as a natural human heart. But they are optimistic that artificial hearts will one day provide a permanent solution for many people with heart conditions.
One of the most recent developments has been the "Carmat," a high-tech pump that operates with a membrane. An electric motor pumps the membrane back and forth, and that moves blood around the body.
Tissue engineering
Other researchers are looking into developing organs in the laboratory, or tissue engineering.
The idea is to cultivate entire organs from stem cells taken from the human body. It is a time-consuming and complicated process. The patient's stem cells, or tissue, are reproduced in a lab and turned into a new organ that can then be implanted.
That's the theory, anyway. Experts say it will be some time before any such artificial organs can be produced in a petri dish in a way that lets them assume the role of an original, human organ.
One problem is the artificial organ's size. Researchers have developed kidneys and livers in the lab, but compared to human organs, the artificial ones are just not big enough.
Organs made with a 3D printer
Three-dimensional printers have been used to make all kinds of things and in a range of materials.
As with paper printers, 3D printers are computer-controlled devices that reproduce an image or design.
The difference is that, instead of printing just one layer of ink, 3D printers build objects with multiple layers — layer by layer — often with liquid plastics, resin or ceramics. Some metals can also be used.
Now, researchers are looking into using 3D printers to produce artificial organs.
In fact, they have produced some already, including artificial ovaries, bones, cartilage and muscle tissue.
In 2019, Israeli researchers even managed to print a heart using human tissue.
But many researchers say the technology and methods are far from ready.
Researchers use a so-called bio ink to 3D print organs. It's another complicated process that involves converting human tissue into a gel, which becomes that bio ink.
The bio ink consists of tissue taken from the patient. In theory, the body considers the bio ink its own, and that reduces the risk of its rejecting the organ. But, again, that is just the theory. It is an important factor, though, because there is always a chance that a patient's body will reject even a donated human organ, let alone an artificial one.
Xenotransplantation: Animals for parts
When it comes to using animal organs for transplants, researchers tend to focus on pigs.
Pig organs are considered physiologically similar to our own. And in some respects, animals have become a kind of organ factory. Researchers have conducted first experiments with pig organs on monkeys. But the results have been less than successful — the organs are often very quickly rejected by the recipient body.
Successful xenotransplants include heart valves from pigs.
The French surgeon Alain Carpentier first developed "biological heart valves" in the 1970s. They consist of animal tissue. The risk of the body rejecting the transplanted organ is low, and compared to artificial heart valves, patients are not required to use a blood thinner or anticoagulant for the rest of their lives.
Heart valves are a vital organ, so this has been a major step. They make sure that your blood gets sent in the right direction around your body, with every heartbeat, which means about 100,000 times per day — an incredible thing.
Heart valves from pigs have been implanted in humans successfully for decades. But they don't last forever, either. They are susceptible to wear-and-tear like anything else.
Doctors tend to use animal heart valves, including those from cows, in older patients. And the operation is considered quite routine these days.
But, even here, problems can arise. For instance, viruses can enter the body during the operation — every operation carries a certain level of risk. To fully prevent this, scientists would have to keep their donor pigs in a sterile, isolated environment. But usually, the animals come straight from the slaughterhouse.