Finding human organ donors for transplant is a matter of grave concern worldwide. Thousands of patients succumb to death waiting in line for organ donors. For years scientists have struggled to find alternatives and have chiefly resorted to stem-cell research hoping to grow human organs in animals such as sheep and pigs. However, the approach has not reaped any fruitful results so far.

Recently, however, scientists from various international institutes have attempted to create mixed-species embryos by injecting stem cells from humans into macaque (monkey) embryos. Monkey embryos are mainly used for this purpose because monkeys are genetically the closest to the human species.

Scientists injected 25 induced pluripotent stem cells from humans into 132 macaque embryos. The embryos were each 6-days old. All cells survived and grew inside the 132 embryos in the first 24 hours. After a lapse of 10 days, 29 embryos expired leaving only 103 chimeric embryos behind. By the 19th day, all except 3 chimeric embryos died, which too were terminated.

Researchers have marked this a great victory and believe that the rate the human cells grew inside the monkey embryos for the first 24 hours is remarkable and could be a great breakthrough in genetic engineering.

“This knowledge will allow us to go back now and try to re-engineer these pathways that are successful for allowing appropriate development of human cells in these other animals,” Juan Carlos Izpisua Belmonte, a genetics professor at the Salk Institute for Biological Sciences in La Jolla, California, and co-author of the study told NPR.

“We are very, very excited,” he added.

“Our goal is not to generate any new organism, any monster,” Belmonte told the broadcaster. “We are trying to understand how cells from different organisms communicate with one another.

All these experiments have led to promising results, as pointed out by the researchers.

Integration of the cells was not a challenge, but the survival was proving to be difficult so eventually the researchers investigated some new ways to conduct screening for drugs. This assisted in generating transplantable cells, tissues, and even organs.

Even though the idea is serving as a major breakthrough in the world of genetics, the experiment has already been tried before but with little success. In 2017, some scientists designed human-pig chimeras by introducing human cells into pig embryos. The cells were then incubated for a period of four weeks and just when they thought it would work, the number of cells grown proved to be insufficient.

This is why the researchers focused on producing a higher rate of growth.

The experiment does raise questions on ethicacy.  “My first question is: Why?” research fellow at Rice University’s Baker Institute Kirstin Matthews told NPR. “I think the public is going to be concerned, and I am as well, that we’re just kind of pushing forward with science without having a proper conversation about what we should or should not do.”