Chimeras―Are They An Ethically Justified Answer to Organ Transplants?
A chimera is, essentially, the term given to an organism with cells belonging to two more individuals. The word chimera is popular in the Greek mythology as a fire-breathing creature with the forepart of a lion, the mid of a goat (usually envisioned with an added head of a goat emerging from its back) and the hind part (or tail) of a serpent. Therefore, the term is fitting when referring to similar hybrids, more specifically human-animal hybrids, which are made of an animal cell that has been injected with human stem cells. That is, there are two different sets of DNA present, leading to the growth into separate organisms.
As of now, no such human-animal embryos have been brought to reach gestational period. But recently, biologist Dr. Hiromitsu Nakauchi, at the University of Tokyo, is planning on bringing mouse-human and rat-human hybrids to term at the approval of the Japanese Government. This means the hybrid embryos will not need to be destroyed on the 14th day. Dr. Nakauchi will use surrogate animals to bring the embryos to full term; 19 to 21 days for mice and 21 to 26 days for rats.
In a similar experiment, Prof. Juan Carlos Izpisúa Belmonte from the Salk Institute in California successfully created human-monkey embryos in China, as was reported by the Spanish newspaper El País, but there is no official publication of the research yet, so no details of the procedure are available and the embryos were most probably terminated after 14 days.
Why Create The Chimera?
Studies have shown that over 400 patients in the UK died waiting for organ transplants and 6000 are still waiting. Many alternate methods of obtaining organs for transplantation are being applied, such as 3-D printed hearts, made of collagen, to the bionic pancreas. Chimeras would work in pretty much the same way. Instead of relying on donors for an organ transplant, the organ can be grown in an animal body using human cells. Dr. Nakauchi and his team have already, successfully, created a rat with a pancreas made of mouse cells and he plans on creating human pancreas in much the same way. Furthermore, in his experiments, Dr. Nakauchi implanted a mouse, engineered with diabetes, with the chimera’s pancreas, effectively curing it.
Speaking so, to grow an organ for humans, a much larger animal would need to be used. Additionally, creating chimeras of animals that are closely related would yield many promising results.
How To Make the Transplanted Organ:
First, the DNA of an animal embryo is edited, removing the gene that codes for an organ of interest. Then, Human induced pluripotent stem (iPS) cells (which can develop into any cell) are taken from the recipient and injected into the animal embryo. The gap in the genes of the embryo is filled by the iPS, which will now provide the code for the organ of interest that the embryo lacked.
The embryo is then placed in a surrogate animal and allowed to be brought to term, creating an animal with one human organ.
The creation of human-animal hybrids was attempted before, once in 2017, when Izpisúa Belmonte’s team claimed to have created a successful, pig-human hybrid. But, after being developed for 3 to 4 weeks, the only 1/100,000th of the cells identified to be human (using fluorescence) and were not localized in any particular organ.
When Ethics is Involved:
Dr. Mackenzie Graham, a research fellow in neuroethics at the Oxford Uehiro Centre for Practical Ethics, explains how the concept of chimeras is met with much criticism, despite being used for humanitarian aid. People consider them unnatural and think that the alteration of species in such ways is better left to the hands of God. Dr. Mackenzie thinks this criticism needs to be directed towards a much bigger concern.
“If we are creating creatures that have a higher moral status because of, say, higher cognitive capacity, they might be entitled to treatment that we’re not giving them in a research context,” he says. Moral status defines how a creature should be treated by considering its interests. Graham explains that humans have a moral status, which protects them from being harmed or killed by taking their interests in the account. But, a tree does not have any moral status, as it cannot defend itself against being cut down or burned.
What’s important to know is what gives something higher moral status. Some philosophers believe moral status comes with higher cognitive capacity; therefore, all humans have high moral status and free will while all other creatures remain inferior. On the other hand, some relate moral status with the capacity to feel any emotion; mainly suffering. All in all, that moral status is high for creatures that have a high capacity to feel pain and suffering. This includes any living thing that feels pain and can be harmed.
So, when a human-animal hybrid is created, it is important to know if its capacity to suffer has changed. “What if we inject these chimeras with stem cells and because these stem cells can turn into any other type of cell, what if they make their way up into the brain and make changes to the brain which could result in cognitive improvements to the animal?” Graham suggests. This could lead to a hybrid that is more intelligent than a normal animal of the same species, and it feels self-conscious in the same way that a human does. Would that mean they cannot be made use of in the way originally thought? That they have a higher moral status now, and therefore, their interests need to be acknowledged?
Izpisúa Belmonte’s team have reassured that they have safeguarded the human stem cells in a way that if they were to travel to the brain, they will self-destruct. The scientist also said that if the animal’s moral status is increased, it is important to know by how much. It is highly unlikely that a pig would have increased moral status by possessing human cells and that it is justified to use their organs for transplants since humans have a much higher moral status. “If human lives are at stake, hybrids would need to have the same moral status as us for it to be unethical to use them for organs, and this seems highly unlikely.”
What is the Success Rate?
As mentioned previously, a chimera is most likely to survive if the two species used are closely related. Dr. Nakauchi’s mouse-rat hybrid survived well into adulthood given the close relations between the two animals. But, Alejandro De Los Angeles, who is working on similar research at Yale University, says that humans and monkeys have an evolutionary gap of 30–40 million years, not at all a close enough species to make hybrids out of, since they are not closely related. “So, it is unclear if it is possible,” he told The Guardian.
