Science just made a huge breakthrough. A team of researchers at the Salk Institute for Biological Studies (SALK) has succeeded in growing human stem cells in pig embryos. According to experts, this is the first step in the direction of potentially developing human organs in animals that can later be used for transplants.

The organ shortage predicament

Organ shortage is a real crisis. The demand for transplants has rapidly increased in recent years, mainly due to the increased incidence of vital organ failure, as well as advancements in medical procedures. Over 650,000 transplants have occurred in the United States since 1998 — 30,970 alone in 2015. But many people whose lives could be saved by means of a transplant surgery expire before they are able to be paired up with a viable organ. There are currently over 119,000 men, women, and children on the national transplant waiting list. And an estimated 22 people die each day waiting for a transplant. There are simply not enough organs to meet the needs of patients that need them. That’s why scientists are looking to new methods, such as growing human replacement organs in animals, to fill the void.

The future of organ transplants

The idea behind the new approach is that scientists would collect stem cells from a patient’s skin and grow a human replacement organ in a large animal, like a pig. The pigs that grow the human organs would be considered “chimeras,” animals composed of cells that originate from two (or more) different species. Once the organ had matured, it would be harvested and transplanted into a patient’s body. And since the organ would be created via a patient’s own cells, researchers are hypothesizing that there would be minimal risk of immune rejection.

The science behind it

SALK’s Juan Carlos Izpisua Belmonte, and his team recently celebrated the fact that they were able to demonstrate that human stem cells can in fact contribute to forming the tissues of a pig. To achieve this, they injected stem cells into 1,500 pig embryos. After waiting to see which ones survived the first few weeks of life, the researchers determined that the intermediate pluripotent stem cells, “somewhere between a blank slate and a stem cell primed to start developing into different tissues,” were the cells that worked best. Around 20 days in, they used fluorescent tagging to reveal one living human cell within every 100,000 pig cells.

Another group, headed by scientists at the University of Tokyo and Hiromitsu Hiromitsu Nakauchi of Stanford, is working to find ways to treat diabetes by means of animal assistance. The team was able to reverse diabetes in mice by inserting pancreas glands made of mouse cells that were grown in a rat. Tomoyuki Yamaguchi and his colleagues implanted mouse pluripotent stem cells into rat embryos that were genetically engineered to be unable to develop their own pancreas. These rats were therefore forced to rely on the injected mouse cells for the development of the organ. When the rats were grown, the researchers transplanted insulin-producing cells clusters (islets) into mice that were given a drug to develop diabetes. The team found that the mice with diabetes were able to normalize their blood glucose levels for more than a year after the transplantation.

Looking ahead

The studies above are promising discoveries that could potentially help to save lives by means of artificially growing human replacement hormones. While it’s opened the doors to new and future research, these recent experiments have also raised questions of whether or not using animals to manufacture human organs is ethical. One such concern from naysayers is the possibility of pig fetuses developing human-like brains due to the stem cells inserted into the fetuses. And animal rights activists are angered over the idea of pigs being bred for the sole purpose of growing human organs and later killed during the harvesting process. Scientists, however, are rallying behind the idea that if the technology develops further, it could potentially save thousands of lives on an annual basis.