Stem Cell

Stem cells mimic sphere where embryos grow

Researchers report that they have coaxed pluripotent human stem cells to grow on a specially engineered surface into structures that resemble the amniotic sac.

Gumucio likens a PASE to a mismatched plastic Easter egg or a blue-and-red Pokémon ball—with two clearly divided halves of two kinds of cells…

The first few weeks after sperm meets egg still hold many mysteries. Among them: what causes the process to fail, leading to many cases of infertility. Despite the importance of this critical stage, scientists haven’t had a good way to explore what can go wrong, or even what must go right, after the newly formed ball of cells implants in the wall of the human uterus.

But the new achievement with human stem cells may help change that. The tiny lab-grown structures could give researchers a chance to see what they couldn’t before, while avoiding ethical issues associated with studying actual embryos.

The stem cells researchers used spontaneously developed some of the same structural and molecular features seen in a natural amniotic sac, which is an asymmetric, hollow ball-like structure containing cells that will give rise to a part of the placenta as well as the embryo itself.

But the structures lack other key components of the early embryo, so they can’t develop into a fetus.

It’s the first time a team has grown such a structure starting with stem cells, rather than coaxing a donated embryo to grow, as a few other teams have done.

“As many as half of all pregnancies end in the first two weeks after fertilization, often before the woman is even aware she is pregnant. For some couples, there is a chronic inability to get past these critical early developmental steps, but we have not previously had a model that would allow us to explore the reasons why,” says co-senior author Deborah Gumucio, professor of cell and developmental biology and professor of internal medicine at the University of Michigan.

“We hope this work will make it possible for many scientists to dig deeper into the pathways…