Every ten minutes, another name is added to the growing list of disgruntled patients waiting desperately for an organ transplant. The increase in organ failure over the past decades, and the subsequent success of many transplantation procedures has resulted in organ transplants being one of the most effective treatments for vital organ failure. As a consequence, the recent rising demand for organs has led to a severe shortage of organ donors worldwide. In the United States alone, over 120,000 patients are currently waiting for potentially lifesaving organ transplants, and this number is projected to only keep rising. Patients suffering from terminal illnesses may have to wait years before receiving an organ transplant, and many die while still on the waiting list.1 Certainly, creating better technologies to fix the organ shortage crisis is a top priority of many physicians, policy makers, and biomedical researchers alike.
Some scientists in the U.S. are thinking of a radical, yet promising idea – growing human organs inside pigs. By injecting human stem cells into a pig embryo, scientists can create a human-pig hybrid embryo, called a “chimeric” embryo. Hypothetically, this embryo can develop into a pig with an entirely functional human organ that should avoid immuno-rejection complications within the patient whose stem cells were used.
To create this chimera, scientists at UC Davis use a powerful gene editing tool called CRISPR/Cas9, which allows for precise editing of DNA. First, the section of the pig embryo’s DNA sequence used to create a certain organ, a pancreas for example, is deleted. Then, the patient’s stem cells are injected into the embryo, creating the chimera, which allows for a human pancreas to grow in order to fill the void. This chimeric embryo is then implanted back into the sow to further grow.2
Surely, any research breakthrough that can potentially generate human organs without rejection in the body is exciting to scientists; however, this particular research is fraught with ethical concerns. For instance, there is a miniscule, but real, possibility that the human stem cells inside the embryo could affect other organs, such as the brain or the heart, giving the pig more human-like characteristics.3 More pressing, however, is that the idea of creating “organ farms” for human benefit could lead to inhumane animal breeding and exploitation, further diminishing the quality of lives for many animals living in large farms. Because of such possibilities, the National Institutes of Health has indefinitely suspended chimera research until more information is brought to light about its implications.
To avoid some of the aforementioned concerns, the UC Davis study limits the gestation period for the embryo to only 28 days, before it is extracted and analyzed. This 28 day limit prevents the embryo from properly developing into anything more than just a half-inch long fetus, as a pig takes 114 days to fully develop. However, this gestation period is enough time to see whether the embryo has human pancreatic cells that are contributing to human pancreas growth.
This research is undeniably promising and exciting, as it represents an alternative strategy to generate organs. Despite this, it should not be considered as the first means to aid the organ shortage crisis, because so little is known about the full implications of creating chimeric embryos. It is much more necessary right now to take a policy stance and focus on raising the number of voluntary organ donors in an ethical manner; in addition, we must aim to better understand the molecular principles behind immuno-rejection to increase the efficacy of organ transplants and improve post-transplant outcomes.