Synthetic Embryos Have Been Implanted Into Monkey Wombs

An anonymous reader quotes a report from MIT Technology Review: Embryos made from stem cells -- instead of a sperm and egg -- have been created from monkey cells for the first time. When researchers put these 'synthetic embryos' into the uteruses of adult monkeys, some showed the initial signs of pregnancy. It's the furthest scientists have ever been able to take lab-grown embryos in primates -- and the work hints that it may one day be possible to generate fetuses this way. The team behind the research, Zhen Liu at the Chinese Academy of Sciences in Shanghai and his colleagues, started with embryonic stem cells originally taken from macaque monkey embryos. These cells have been grown in labs for multiple generations and, given the right conditions, have the potential to develop into pretty much any type of body cell, including those that make up organs, blood, and nervous system.

The team used a set of lab conditions, which they tweaked and improved, to encourage embryonic stem cells to develop further. Over several days, the cells began developing in a very similar way to embryos. The resulting blobs of cells are called blastoids, because they look like early embryos, which are called blastocysts. After the blastoids had been growing in a dish for seven days, the researchers put them through a series of tests to figure out how similar they were to typical embryos. In one test, the team separated the individual cells in the blastoids and checked to see which genes were expressed in each one. The team analyzed over 6,000 individual cells this way.

These tests revealed close similarities between the stem-cell-derived embryos and conventional monkey embryos. Some of the blastoids were grown for longer -- up to 17 days. These structures looked very much like typical embryos, the researchers say, although other scientists not involved in the study say more evidence is needed to prove just how similar they are. The only way to find out how embryo-like these blastoids really are is to test whether they can develop in a monkey's uterus. So the team put between eight and 10 seven-day-old blastoids into the uteruses of each of eight adult monkeys. The researchers then monitored the transferred blastoids for three weeks. The researchers believe that in three of these monkeys, the blastoids successfully implanted in the uterus and appeared to generate a yolk sac -- one of the very first signs of pregnancy. These monkeys also had elevated levels of pregnancy hormones. In other words, they would have had a positive pregnancy test. But within 20 days of transfer, the monkey blastoids stopped developing and seemed to come apart, say Liu and colleagues, who published their results in the journal Cell Stem Cell. The results suggest that blastoids still aren't perfect replicas of normal embryos. 'That might be because a typical embryo is generated from an egg, which is then fertilized by sperm,' reports MIT Technology Review. 'A blastoid made from stem cells might express genes in the same way as a normal embryo, but it may be missing something crucial that normally comes from an egg.'

'There's also a chance that the team might have seen more progress if the experiment had been done in more monkeys. After all, of the 484 blastoids that were developing at day seven, only five survived to day 17.'

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