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A New Chapter for Heart Transplantation

The phenomenon of replacing organs began from understanding that blood can be exchanged. The first blood transfusion occurred in the early 1800’s and ever since, science and medicine has evolved to the transplantation of organs . The first kidney transplant took place in 1954 and first heart transplant in 1963.

The idea of replacing a human organ with another human organ is easier to wrap your head around than replacing human organs with animals. Oftentimes the use of animals in research is considered a necessary step in understanding mechanisms of disease but with that comes limitations. Animals in science are also linked to the spread of disease and the closer we get in similarity to the animal used e.g chimpanzees it is inhumane to even begin thinking about it.

So why are scientists and doctors so keen on getting pig hearts working for humans?

Human organ donation is still in a heavy deficit, therefore the possibilities of having other sources is truly life changing. This month many news outlets covered the death of the first man to receive a heart transplant from a pig. - Guardian, BBC news, Sky News.

The articles summarise what is considered a breakthrough in science and medicine. The first ever pig to human heart transplant patient died after surviving a precious two months. In that time he was given an extended life. In opting for the treatment he gave scientists and future patients an immense amount of hope. Revolutionary science comes at a time where there are limited options for the patient that chose something of such high risk. In the guardian article his son makes a statement

“We hope this story can be the beginning of hope and not the end.” - David Bennet Jr

A New chapter in the story of Xenotransplantation.

The transplantation of the pig heart into the first human is the beginning of a new chapter in the story of Xenotransplantation.

Xenotransplantation is the transplantation of living cells, tissues or organs from one species to another.

Focusing on pigs and the heart as an organ. There is a story of many decades to tell. In a 1968 article, researchers mapped out the similarities and differences between human and pig hearts by looking at the gross structure. The heart is a simple and essential organ. Its singular role is to pump blood through it to provide oxygen to our cells that keep us functioning. A main difference between a pig and human heart in the papers published were how their anatomy differed due to the stance positions of the pig vs human and hence placement in the body. A fun fact for the non anatomy enthusiast is that the pig heart most resembles the “valentine” heart we all know and use.A 2014 article further highlights the similarities and differences with the pig going into further detail on circulation and ethical issues around its use. It is evident the pig has been a key focus for cardiovascular researchers for many years and that will continue on.

Image of the blood vessels ( vasculature) of a human heart
Image of the blood vessels ( vasculature) of a human heart

Pig Xenografts : The past, present and future

The main challenges for replacement organs are rejections. The Pig-human heart transplant

accounted for this as the heart used was genetically engineered to replace some pig genes with human genes in order to account for a more suitable match.

Pigs are a cornerstone to cardiovascular research development.Their hearts have been integrated into modern medicine and proven to be successful. Heart disease can present in many forms and not only through the commonly known heart attack. The heart is an organ that allows blood to actively and passively flow through. There are valves in the heart that prevent the backflow of blood to different regions of the heart. A faulty valve is a common phenomenon and while some patients can have them repaired, valve replacement surgeries are another alternative. The replacement material can either be mechanical or biological.

Pig valves are one of the biological materials used and once implanted can last from 10-17 years.Science isn’t a one size fits all and treatment is always based on the clinical picture of the patient. Whole pig hearts as a replacement is going to continue to be a focus for future research, other avenues such as regenerative medicine are also making strides in filling the organ donation gap.

The main scientific goal is solving the growing need for donor organs in a world that lacks donors. The more treatment options out there whether human, pig or organs grown in the lab will only lead to better patient outcomes in the future. The ethical considerations and general acceptance is one scientist will have to work hard on explaining.

Acceptance of new therapies!

Heart disease is the number one killer in the western world and with that the discussions around heart health, donations and acceptance of this new therapy will need to be had more often.

When is a good time to start discussing public acceptance? The future of pig hearts as a possibility for regular donor transplantation is one of the future. However, the discussion needs to happen now. The pandemic has shown science on speed mode. We potentially get to watch this new chapter evolve at a much slower pace which is very exciting.

My personal opinion as a scientist is excitement and hope, as someone that communicates science is putting across this isn't a simple task and will most likely only be available to the minority and as a very complex topic, I hope people will seek out the answers and the science community will be readily available to fill in the gaps they know.

If you have pressing questions such as

  1. How did they do it?

  2. Why did they do it?

  3. Will there be clinical trials?

  4. What are the potential disease implications? and more read this: Animal-Human Organ transplants Pig-kidney-heart history.

Every science article is written to fit a narrative. Create your own story and learn more by clicking on some of the articles below :)

References / Extra Reading

  1. Science News: Animal - human organ transplants

  2. Anatomy of the pig heart: comparisons with normal cardiac structure

  3. A comparative Anatomic Physiologic Overview of the Porcine Heart

  4. Nature: First pig-to-human heart transplant : what can scientist learn?

  5. NHS: History of donation, transfusion and transplantation

  6. Ethical issues in xenotransplantation: The first Pig to Human Heart Transplant

  7. The potential of genetically engineered pig heart transplantation in infants with complex congenital heart disease.