Scientists grow whole model of human embryo without sperm or egg
Weizmann Institute of Science in Israel created the complete models of human embryos from stem cells cultured in the lab — and managed to grow them outside the womb up to day 14.
The research, published in the journal Nature, shows that these synthetic embryo models had all the structures and compartments characteristic of this stage, including the placenta, yolk sac, chorionic sac and other external tissues that ensure the models' dynamic and adequate growth.
The stem cell-derived human embryo model «closely mimics the development of a real human embryo, particularly the emergence of its exquisitely fine architecture,» said Jacob Hanna, a professor at the Weizmann Institute of Science.
The scientists did not use fertilised eggs or a womb. Rather, they started out with human cells known as pluripotent stem cells, which have the potential to differentiate into many cell types.
Some were derived from adult skin cells that had been reverted to «stemness.» Others were the progeny of human stem cell lines that had been cultured for years in the lab, they said.
The researchers then reprogrammed pluripotent stem cells to revert these cells to an even earlier state — known as the naive state — in which they are capable of specialising into any type of cell.
This stage corresponds to day 7 of the natural human embryo, around the time it implants itself in the womb.
The scientists divided the cells into three groups.
The cells intended to develop into the embryo were left as is. The cells in each of the other groups were treated only with chemicals, without any need for genetic modification, so as to turn on certain genes.
These genes cause these cells to differentiate towards one of three tissue types needed to sustain the
