Science reveals human-pig embryos

WHY SWINES? — Pigs are ideal for chimera research because their organs are relatively similar sizes as humans, despite the distant genetic similarities and that their organs grow at quicker rates. This image shows human stem cells injected into a pig embryo. (BBC)

For decades, scientists have implemented controversial medical research, raising questions on whether they stretch their limits too far.

Researchers argue whether they lean toward innovative medical progress or ethical laws. With a high demand for organs, the United Network for Organ Sharing revealed that 118,744 people are on the waiting list for an organ transplant. The issue continues to rise as the law claims unethical treatment for putting a price tag on organs in the market. In addition, because only a limited number of candidates are registered organ donors, presumed consent raises ethical concerns as it allows individuals to lose ownership of their bodies.

However, the “chimera,” which is commonly known as a mythical creature of a hybrid lion, snake and goat, was a procedure that scientists discovered. This experiment revealed that scientists could combine tissue from humans and animals, resulting in a human-pig embryo to grow. This experiment involved human stem cells, that are indeterminate, being injected into a pig embryo. This embryo of human and pig cells was then implanted into the uterus of a sow, where it grew up to four weeks.
After a month, the stem cells in the embryo had developed into precursors of vital organs such as the heart, liver, kidneys and neurons.

The researchers cautioned that this experiment was not efficient and could not develop into a live piglet that may be useful for immediate care. However, it was a stepping stone toward organ developmental research that could grow functioning human organs. “We were just trying to answer the yes or no question of, can human cells contribute at all,” said Juan Carlos Izpisua Belmonte, a developmental biologist at Salk Institute who was the senior author of the human-pig chimera study. “And the answer to that question is yes.”

Previous experiments were conducted in the past, involving a similar approach of chimera where researchers created embryos that were part-rat, part-mouse by growing a mouse pancreas inside a rat. The insulin-secreting tissue from the mouse pancreas was injected into diabetic mice to test if its’ function was successful without a rejection of the immune response. This experiment revealed that interspecies organ transplant is possible. If functional organs of one species can be grown into another, then would this supply a successful resource to the demand of organ transplants?

The National Institutes of Health had a suspension on funding for research on human-animal chimera, which was the reason why the researchers were only able to grow the embryo for up to one month. Several can argue that chimera crosses the ethical line of taking advantage of human and animal DNA, modifying them to the point of no distinction or animals reproducing human DNA to their offspring. Others claim that stem cells raise uncertainty to an organism’s identity by humanizing animals, especially with the threats that an animal may contain a human brain. Would this approach allow animals to human rights?

However, by avoiding certain paths with this research, chimera may allow for further research on human disease, drug testing and embryo development research. Organ development for transplants still raises the questions of uncertainty. Producing organs in a body is more beneficial than growing in a petri dish since it replicates as naturally as possible. “What if we let nature do the work for us? What if we just put human cells inside the embryo and the embryo knows what to do?” said Izpisua Belmonte. But will this allow for a future market of organs to be fought over, or can this save the lives of thousands?