Genetics researchers at Salk University in California made strides in organ transplant research by growing an embryo that is part-pig and part-human, as described in Cell, a peer-reviewed scientific journal, on Jan. 26. According to The Washington Post, the researchers created the embryo by injecting human stem cells into a pig embryo and placing it in the uterus of a pig. The researchers hope that one day a similar process can be used to make organ transplants more available, as the U.S. Department of Health and Human Services (HHS) reports that 22 people die each day due to a shortage of organs.
This type of hybrid is called a chimera, named after a creature in Greek mythology that is a combination of a snake, a lion and a goat. Much of past chimera research has involved rats and mice. Last December, scientists published an experiment in the journal Nature in which they grew a mouse pancreas inside a rat embryo and transferred some of the tissue to diabetic mice, alleviating some of the symptoms of diabetes. But this is the first time that researchers have created a human-pig hybrid.
According to Wheaton’s Associate Professor of Genetics Rodney Scott, pig organs are “fairly similar” to human organs in terms of size and basic physiology. In fact, clinicians already use valves from pig hearts in human heart surgery. “Before, they have put human cells into rodent embryos,” Scott said. “If the long term objective is to make replacement human organs, that’s never going to be done in a rodent system.”
Although researchers have made progress growing organs in petri dishes, they are not entirely the same as those grown in an embryo. “There’s a lot of tweaking you have to do along the way to make things come out right,” Scott said. But an embryo growing in a living organism has the benefit of natural signals from the body directing the process of organ growth.
The creation of human-animal hybrids has raised many ethical questions. In 2015, the National Institute of Health put a temporary ban on federal funding for certain human-animal chimera research. Some argue that because stem cells can develop into any type of tissue, researchers risk growing human brain cells in animals, which could lead to sentient organisms, or growing reproductive cells, furthering the possibility of breeding these creatures.
However, Scott argued that, although it’s important to have conversations about experimental ethics, the results of these concerns were not likely. Researchers can genetically modify stem cells not to develop into nervous tissue. Even if they did, it would take a lot of neurons to change the pig’s consciousness. He also said that there should be strict guidelines against breeding the hybrids in the event that they developed sperm or egg cells.
Joy Riley, a physician and executive director of the Tennessee Center for Bioethics and Culture, told the Baptist Press that these issues raise important moral questions that should be answered before scientists move forward with this research. “From more than 1,400 embryos containing pig and human cells, 186 were harvested between day 21 and day 28 of development,” Riley wrote. “What were these embryos? How does one classify these beings? How many cells does it take in order for the being to be human?”
Scott addressed similar arguments that researchers are “playing God,” a claim that comes up frequently in Christian circles. “To me that’s a weak argument because it doesn’t identify what is being done that is illegitimate or inappropriate,” he said. “ has given us minds that are capable of thinking in a way that mirror his thinking in a small way, and he has told us that we’re in charge of creation, that we should care for it. Sometimes that caring for creation requires us to manipulate creation. If that’s playing God, then we’ve been playing God ever since the dawn of human time.”
Scott said it was “hard to say” how long it would be before this experiment could be turned into a clinical procedure but that researchers have “the kind of techniques in hand” to make it “reasonably feasible” to take the next steps.