Every twelve minutes another name is added to the American national transplant waiting list. One organ donor can save up to eight lives; however with so many hundreds of thousands of patients waiting for this surgery, it is not surprising that approximately 18 people die every day due to the lack of available organs for transplant.
Furthermore, in researching statistics for transplant surgery I have discovered that some transplants do not last. For example, a kidney transplant only lasts around 10-12 years before another kidney must be transplanted into the body. I found this fact shocking. Kidneys play such a vital role in the body: filtering the blood and reabsorbing important molecules such as water and glucose from the nephrons. Living without two functioning kidneys is exceedingly difficult, as one must always be in reach of a hospital in case a dialysis machine is needed.
However, one solution to this problem has caused controversy as its ethics are discussed.
This solution is xenotransplantation, or in other words, transplanting organs between species. Unfortunately, that doesn’t mean that in the foreseeable future I’ll have the giraffe neck I’ve always wanted, but it means that organs for transplants can come from animals rather than human donors. The animal used for this type of transplant is the pig, as pigs are reasonably similar to humans. Unarguably, apes are more similar to humans. However for the purpose of xenotransplantation, the close similarity between apes and humans is dangerous; like humans, primates carry disease easily, and these diseases could easily infect humans. The pigs’ organs are genetically modified by inserting strands of human DNA, so that the organs are more willingly accepted by patients’ immune systems.
To date, no transplant of this fashion has been entirely successful; the last attempt was on a hepatitis B patient in 1993. Often the patient’s body will quickly destroy the foreign organ (this is called hyperacute rejection). Conversely, rejection of the organ could be over weeks, months or years, because of causes not yet fully understood by medics; for example, chronic rejection. However, hyperacute and chronic rejection- as well as other types of transplant rejection- can occur in all transplants, not just xenotransplants.
In addition, I have learnt that the xenograph (the tissue transplanted from one specie to a recipient of another specie) also brings the possibility of ‘xenozoonosis’, meaning the transmission of pathogens between species. The chance of disease transmission is increased by the operation as the physical barriers that help prevent disease- such as the skin- are opened, and the patient would be extremely ‘immunosuppressed’ in order to allow the organ to not be attacked by the lymphocytes and phagocytes of the bloodstream.
…Just as an aside, I feel sympathy for lymphocytes. Phagocytes are so much cooler. If I were a blood cell, I would want to have the power to extend my cytoplasm (pseudopodia) and engulf pathogens…
There are benefits of xenotransplantation, such as:
- We are in desperate need of organs for transplants and xenotransplantation can allow us to help more people
- Xenotransplantation could eliminate the need for living donors, which is positive as donating organs whilst still living can be dangerous for the donor
- Could also eliminate the need for deceased donors
- Using organs from pigs means that transplants can be easily prescheduled
- Easier to obtain organs for second transplants
- Decreases waiting times for patients which also improves qualities of lives and could prevent fatalities
- Decreases chances of using damaged organs for transplants
- Could eliminate illegally obtained human organs
- As far as prefixes go, ‘xeno’ (meaning foreign or other) is a pretty good one
I have also read on the website of the National Centre for Biotechnology Information (NCBI) that another advantage of xenotransplantation is that ischemia times can be minimised. Not knowing what an ischemia time was, I researched it and found out that it is the time in which the organs for transplantation are kept outside the body and do not receive any blood (or oxygen), until reperfusion (when they once again receive blood flow). Not only does the term ‘ischemia time’ apply when the organs are outside of the body, but also when cross clamping occurs. ‘Cross clamping’ is the procedure of clamping the aorta- the longest artery in the body- to restrict blood flow in surgical operations.
“It is infinitely better to transplant a heart than to bury it to be devoured by worms.”
-Christiaan Barnard (1922-2001), cardiac surgeon who performed the first successful human-to-human heart transplant
However, xenotransplantation has many disadvantages and ethical concerns, including ones previously discussed.
- Xenotransplantation could lead to disease epidemics
- Many patients could die from xenotransplantation as organs are rejected, and those who survive the initial operation could face longer term problems
- Successful xenotransplants may need constant monitoring throughout the life of the patient
- Against animal rights
- Pigs are already slaughtered every day for the benefit of humans
- Encourages cloning of animals, which again breeches animal rights and also is considered as an act against nature
- Encourages xenotourism (people leaving the country to have operations not legalised in their home country)
In the mean time, governments have a sceptical attitude towards xenotransplantation, and alternatives- such as stem cell research and creating artificial organs- are being explored.
isntsciencewonderful 