X is for Xenotransplantation

Xenotransplantation is the removal of organs or living cells from one species for transplant into another.

Xenotransplantation is considered as an option for transplant of organs into humans due to the shortage of human organ donors, and the incompatibility of many human organs for transplantation. Human organ donations can be consented by the donor in different ways depending on the laws of the country. In Australia, human organ donations are considered using an opt-in process, requiring people to explicitly consent to having their organs removed following their death. This has perpetuated a significant shortage of human organs available for donation as many people do not take the step to registering as an organ donor. Some countries, such as the United Kingdom, operate under a presumed consent system where all persons are considered donors upon death. However, this has its own issues as, for example, relatives can dispute their family member’s donation as they had not explicitly consented to their organs being removed.

There are a number of reasons for the shortage of organs. Family disputes in the presumed consent approach can render the organs available for donation useless given the time taken to resolve the dispute, and people leading longer, healthier lives extends the period of time between possible organ donations.

Adding a contemporary revival of xenotransplantation as a medical intervention has increased the number of experiments attempting to genetically engineer animal organs as a ‘sustainable’ option to fill the gap in patients awaiting organ transplant.

Xenotransplantation has its beginnings in blood transfusions throughout England and France in the seventeenth century, however it wasn’t until the early twentieth century when organ transplant was first attempted. The success of these transplants was relative. Following the procedures and subsequent heavy medication, patients ‘survived’ for up to nine months. In recent years, ‘successes’ have been praised by researchers and the media despite all patients dying in the months following their procedures. Many ‘successful’ procedures last mere hours, which when the planned period of study is mere hours, equals a success to the researchers and a gold star on their paper.

Currently, genetic modification has become the primary goal of researchers and pigs have become the preferred ‘donor’ animal. While the modification of pigs to better suit a human body has brought them slightly genetically closer to a human, there remain a significant number of issues when considering pig organs for transplant.

Humans and pigs last shared a common ancestor over 80 million years ago. Humans are actually more closely related to a laboratory mouse, although we last shared that ancestor about 70 million years ago. While there may be some similarities between humans and pigs, and it is these similarities which researchers and the reporting media will highlight, when considering how alike we are it must the be the entire species’ body which is considered, including the overwhelming number of differences.

As pigs live for a shorter time than humans, their organs grow at a rate faster than that of humans. Organ growth may continue after implantation, potentially causing significant pain to the recipient. It is also unknown the extent of cell and genetic differences between humans and pigs and how these differences impact the body’s acceptance of the transplant. The more we research xenotransplantation, the more issues we come across. In addition to the issues of species difference, even when considering the customisation of genetic modification, there are a significant number of impacts which required drugs, such as immunosuppressants, have on the bodies of transplant recipients.

A common point made by researchers is that pigs are already bred commercially for food. However, the conditions in which these pigs live is far from the bio-secure facilities of research laboratories. For these animals to be bred in facilities which are appropriate for transplant into humans, facilities which ensure the pigs are healthy and free from virus and disease, a significant investment would be required to establish clean facilities for the breeding program.

Modern technologies have already begun to eclipse the decades of research into xenotransplantation. For example, bioprinting can fabricate human-like organs which researchers then use to test medications and which may have unlimited potential to provide organs for human transplant. Current methods of bioprinting often uses some animal material, such as foetal bovine serum, but there are advancements in clean-bioprinting which remove animal components entirely, instead using plant or synthetic materials.

What can be done?

In Australia one must explicitly request to become an organ donor. Previously it was an option when applying for or renewing a driver’s licence, however this is no longer the case. Taking #thenextsixtyseconds to join or check your status on the Australian Organ Donor Register means that you are taking a step towards providing a life for someone, and towards reducing or eliminating the need for unnecessary xenotransplantation experiments on animals.

Sources:

Berg J, Kurreck J. Clean bioprinting - Fabrication of 3D organ models devoid of animal components. ALTEX. 2021;38(2):269-288. doi: 10.14573/altex.2009151. Epub 2020 Dec 2. PMID: 33264417.

Craddock, Paul. Spare Parts, 2022. ISBN 9780241370261.

Dooldeniya MD, Warrens AN. Xenotransplantation: where are we today? J R Soc Med. 2003 Mar;96(3):111-7. doi: 10.1258/jrsm.96.3.111. PMID: 12612110; PMCID: PMC539416.

The similarities between humans and pigs. www.science.org.au/curious/people-medicine/similarities-between-humans-and-pigs