[Retric]

It’s a model because it’s not completely equivalent. Medicine has learned a great deal from studying rodents, but humans are quite different.

For one thing human embryos would have already been implanted in a womb for a week at that point and a great deal of signaling occurs between embryo and the uterus.

[jtbayly]

>"For one thing human embryos would have already been implanted in a womb for a week at that point"

At what point? Implantation typically occurs 6-12 days after fertilization. This experiment starts at the equivalent of day 7. IVF is a thing.

It sounds like you're just guessing.

Edited to add, this article says "It would be illegal to implant them into a patient’s womb" which is a far cry from what you are implying, that it would be impossible.

https://www.theguardian.com/science/2023/jun/14/synthetic-hu...

[Retric]

I thought I was repeating what the article said:

“This stage corresponds to day 7 of the natural human embryo, around the time it implants itself in the womb.”

“The researchers discovered that if the embryo is not enveloped by placenta-forming cells in the right manner at day 3 of the protocol (corresponding to day 10 in natural embryonic development), its internal structures, such as the yolk sac, fail to properly develop.”

“The stem cell–based embryo-like structures (termed SEMs) developed normally outside the womb for 8 days, reaching a developmental stage equivalent to day 14 in human embryonic development.” (So ~1 week post implantation for a human embryo.)

[jtbayly]

None of your quotes indicate that it would be impossible to implant these. The article is beating around the bush, but essentially it is saying "These could potentially be implanted." That's why people are somewhat up in arms about this. Read the other article I linked.

This research in animals has led to successful implantation, but not live births. Nobody knows why yet.

[Retric]

Nothing I said had anything to do with if these were viable or could be made viable, just that they aren’t direct equivalents.

People could be up in arms if hypothetically 50% of these where viable, but the nonviable 50% would still cause errors when compared to human embryos. Alternatively, 100% could be viable and they could still be different in critical ways from natural human embryos resulting in universally late or premature births etc. Or perhaps 0% are viable and people just don’t understand the nuances.

It’s therefore an orthogonal question.

[jtbayly]

You don’t appear to be able to say anything helpful about what “model” means in this discussion. The only explicit claim you made (that they were different because they would have been implanted in a womb for a week already) was incorrect. Some would likely have been implanted for a day.

[Retric]

Your timeline is off, the egg can take nearly 2 weeks to implant but that requires a delay in fertilization. This 14 day timeline is specifically in reference to fertilization not the release of the egg.

The discrepancy exists because people can track the day of ovulation and hormonal changes from implantation but actual fertilization has no obvious signs, unless your doing IVF or something and looking at the actual egg.

That said, extreme outliers may exist but that’s not what we’re talking about.

[beebeepka]

Signalling? Thank you for expanding my horizons. Could you please share some more? Even a link or two would suffice.

[danielschonfeld]

I am not expert but I think OP means different hormones would start to get produced and others would become suppressed to support the creation of a placenta, to support the the lining of the uterus and to cease ovulation and menstrual cycle as well as to start supporting the growing embryo in terms of nutrients by means of generating and connecting blood vessels.

I read somewhere that pregnancy (unlike what is normally described) is a tug of war between the embryo which is the leach if you will on the mother which is the host. The embryo basically try consumes the host and so long as everybody is doing what they're supposed to, all the mechanisms end up keeping that war at bay with both participants making it alive at the end. If some mechanisms (and signals) were to misbehave one of the two would cease to exist.

[I_Am_Nous]

Preeclampsia is a condition where the fetus "requests" that the mother's body increase blood pressure to dangerous levels. It's definitely a case where one misbehaving could kill both the mother and the fetus.