Chimeras and How They Work: What It Meant When Researchers Built the First Human-Pig Hybrid

Scientists, for the first time, have successfully grown human cells inside early-stage pig embryos in laboratories. This means that we have created the first pig-human hybrids or interspecies chimeras.

While the experiment is still in its infant stage, we may one day see lab-grown human organs that can be transplanted to those who need them and save thousands of lives.

According to Science Alert, researchers from the U.S. injected human stem cells into early-stage pig embryos, which were then transferred into surrogate sows, allowing them to develop until the first trimester. More than 150 of these embryos have formed into chimeras; meaning, they developed the precursors of organs such as the heart and the liver. However, they contained very little amount of human cells. Only one in 10,000 of the hybrids' cells is human.

Phys.org notes that this is a proof-of-concept experiment that shows that human-pig hybrids are, in fact, possible. The ultimate goal is to check if these lab-grown human parts can be made into transplanted organs.

Team member Juan Carlos Izpisua Belmonte from the Salk Institute of California said the findings may offer hope for advancing science and medicine by providing an ability to study embryo development, organ formation, and even pave a way to new therapies.

This technology may even be used to allow organisms to produce specific organs of other species. Izpisua Belmonte and his team have performed experiments on these way back in 2015. Their earlier studies said they were successful in integrating human stem cells into mouse embryos, which showed that human cells could develop inside a different species.

The term "chimera" comes from Greek mythology. It is a monster that looks like a lion but with a goat's head sticking from the side of its neck and a snake for a tail. In biology, "chimera" is defined as one individual organism containing cells from another.

According to Nature, the human-pig embryo was the culmination of a number of experiments regarding chimeras. The study involved two important steps: using CRISPR-Cas9, a new tool in gene-editing that turns off genes that produce pancreas on mice, and then inserting rat stem cells into the mouse that contains the genetic information needed to grow rat pancreas.

These embryos, though they have different species' pancreas inside them, developed normally. This allowed for other similar experiments as well.