Hybrid is the combination of two offspring with difference and varieties. The project proves that human cells can be introduced into a non-human organism, survive, and even grow inside a host animal, in this case, pigs.
This biomedical advance has long been a dream and a quandary for scientists hoping to address a critical shortage of donor organs.
Every ten minutes, a person is added to the national waiting list for organ transplants. And every day, 22 people on that list die without the organ they need. What if, rather than relying on a generous donor, you could grow a custom organ inside an animal instead?
Building a Chimera
There are two ways to make a chimera. The first is to introduce the organs of one animal into another—a risky proposition, because the host’s immune system may cause the organ to be rejected.
The other method is to begin at the embryonic level, introducing one animal’s cells into the embryo of another and letting them grow together into a hybrid.
At first, Juan Carlos Izpisua Belmonte, a professor in the Salk Institute’s Gene Expression Laboratory, thought the concept of using a host embryo to grow organs seemed straightforward enough. However, it took Belmonte and more than 40 collaborators four years to figure out how to make a human-animal chimera.
To do so, the team piggybacked off prior chimera research conducted on mice and rats.
Other scientists had already figured out how to grow the pancreatic tissue of a rat inside a mouse. On Wednesday, that team announced that mouse pancreases grown inside rats successfully treated diabetes when parts of the healthy organs were transplanted into diseased mice.
The Salk-led group took the concept one step further, using the genome editing tool called CRISPR to hack into mouse blastocysts—the precursors of embryos. There, they deleted genes that mice need to grow certain organs. When they introduced rat stem cells capable of producing those organs, those cells flourished.