One of the greatest challenges in medical history was to find a cure for patients who
suffered from organ failure because of damage to the organ cannot be reversed or
repaired. This is why organ transplantation is one of the greatest medical breakthroughs
of all time. Transplantation is a surgical procedure in which tissue or an organ is
transferred from one area of a person's body to another area, or from one person called
the donor to another person called the recipient.
There are two types of organ transplantations, including transplantation
and xenotransplantation.
While all transplantation involves a transplantation of an organ or tissue between
two similar species, such as human to human xenotransplantation involves a
transplantation from one species to a different species, such as a pig to a human.
And we'll discuss xenotransplantation specifically.
The applicability of xenotransplantation is of particular importance because there's a
huge lack of human donors.
So other animals serve as a great substitute to save the lives of patients with organ
failure. The concept of xenotransplantation goes back all the way to the 17th century in
France, where Dr.
Jean-Baptiste Denys attempted the first sheep to human blood transfusion.
Pigs, however, are great candidates for xenotransplantation nowadays due to the fast
maturation of organs and similar physiology to the human anatomy.
In choosing the best candidate animal for xenotransplantation, researchers often narrow
it down to pigs and primates.
Some reasons that pigs are preferred over primates include the fact that pigs can be
bred intensively with large litters, meaning the number of available organs could be
increased rapidly.
Keeping pigs in sterile conditions is relatively easy.
Pigs do not resemble humans the same way primates do.
Making people feel less guilt when raising pigs for transplantation and the use of pigs
is considered by some as acceptable because of their production for food.
While it does seem strange that the organs of a different animal could function properly
in a new host, a 98% DNA match between humans and pigs leads to pig hearts having a
very similar size anatomy and function to human hearts.
And they are quite compatible.
Both hearts contain four chambers consisting of two ventricles and two atria.
There are also four valves that are consistent with the valves in the human
heart, and the aorta is in a similar position.
These similarities allow for blood to flow through a pig heart, the same way it flows
through a human heart. In fact, prior to the first pig to human heart transplant, pig
heart valves have been commonly used as replacements for human heart valves in past
years. Despite the many similarities, there are also some key differences.
For one, the shape of the pig heart is a typical Valentine heart shape, while the
human heart is more of a trapezoidal sheep.
Pig hearts also tend to be larger than human hearts.
Pigs are four legged animals and the heart is used to pumping horizontally.
Whereas in humans who stand upright, the heart pumps in vertically.
Additionally, in humans, the left atrium receives four pulmonary veins, whereas in
pigs it receives only two pulmonary veins.
There are also some occasions where the physiology and beat rate of a pig heart
differs from that of a human heart and must be corrected.
Although most of the differences seen are minimal and can be fixed with some
traditional plumbing, they are still very important to consider during
xenotransplantation.
After going through the taxing process of xenotransplantation, the journey does not end
there as there can be various post transplant difficulties that a patient needs
to deal with. The biggest concern post surgery is rejection of the transplanted
organ and increased susceptibility to secondary infections.
Rejection is usually the primary concern following transplantation.
The fear of rejection is even more amplified if the transplanted organ is from a non-human
donor. Our body has curated mechanisms to prevent our immune system from attacking our
own organs, tissues and cells.
However, any foreign material that enters our body is instantly eliminated by our
immune system.
Due to this process, an organ that comes from a different species is usually rejected
within a few minutes in a process called hyper acute rejection.
This is a process in which immune cells in the recipient's bloodstream attack the
transplanted organ and eliminate it.
The transplanted organ usually has antigens on its surface, which are like flags stating,
Hey, I am a pig heart, not a human heart that signals the immune cells to trigger a
defensive immune response, causing the organ to stop working.
To bypass this mechanism of rejection.
Anti-rejection drugs, also known as immunosuppressive drugs, are administered to
the patient. These drugs suppress the recipient's immune system, preventing it from
being able to mount a strong response against the transplanted organ.
Scientists have also been devising a mechanism to genetically modified the donor's
genome to prevent rejection.
However, despite these anti-rejection drugs and genetic modification, transplantation
still poses a serious risk.
One of these risks is the risk of infections.
Because patients take immunosuppressive drugs, their immune system is weakened,
making it unable to protect the body against foreign pathogens.
These immunosuppressants can lead to a significant decrease in white blood cells in.
Rethink susceptibility to many bacterial infections, making them more serious than
they otherwise would be.
Evidently, the new xenotransplantation of the Pig Heart is an amazing breakthrough in
the medical field. However, it does not come without negatives.
Patients will have to adhere to strict medical regimens, like taking multiple
immunosuppressive drugs and having regular doctor visits, which include sampling or
biopsies of the transplanted heart tissue to check for rejection, which can be an anxiety
inducing process.
The transplantation process is very energy taxing, and it can take several months for a
person to gain their energy back.
If such an intense surgical procedure crossing the barriers of animals and humans,
you can imagine that there are quite a few ethical concerns regarding
xenotransplantation. Let's delve into some of them.
Firstly, many argue if it is right to harvest animals for their organs to save
human lives, we do not have consent from these animals to do such a thing and the
unnatural living conditions which they are raised in is questionable.
Animal rights movements also argue that raising pigs just to put their organs into
humans is horrifying and inhumane.
Another point is that how would you go about deciding who deserves the organ first?
For example, a child who desperately needs an organ as soon as possible, versus a mother
of five who has been on the waiting list for a regular organ for a long time.
In this case, how do we allocate the pig organs accordingly, since the process is so
new? Would we create a waiting list or start giving them to those who need it most?
What is fair and what is not?
Certain religions and cultures also prevent pork consumption.
In this case, xenotransplantation may not be suitable for them, as they may not want a pig
heart inside of them.
So how would we go about accommodating for this?
There is also the claim that xenotransplantation violates God's will.
God preserves humans, so humans should preserve animals.
Is it right to play God by crossing the barrier of species?
Throughout this video, we have discussed xenotransplantation, looking at the
compatibility between human and pig heart's post-transplant risk factors and ethical
concerns surrounding xenotransplantation.
With many cardiovascular, kidney, liver and lung diseases on the rise, coupled with the
lack of people signing up as organ donors, there's a global organ shortage crisis, a
potential solution that can improve and save lives is xenotransplantation.
There's still a lot more research to be done, but with the first pig to human heart
transplant completed, we're on our way there.
For more information on this specific case, see part two of the series link below.
Thanks for watching.