#Brain stem diagram skin#

This stage corresponds to day 7 of the natural human embryo, around the time it implants itself in the womb. The researchers then used Hanna's recently developed method to reprogram pluripotent stem cells so as to turn the clock further back: to revert these cells to an even earlier state-known as the naïve state-in which they are capable of becoming anything, that is, specializing into any type of cell.

#Brain stem diagram skin#

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.

Rather, they started out with human cells known as pluripotent stem cells, which have the potential to differentiate into many, though not all, cell types. As in that research, the scientists made no use of fertilized eggs or a womb. Hanna's team built on their previous experience in creating synthetic stem cell–based models of mouse embryos. It closely mimics the development of a real human embryo, particularly the emergence of its exquisitely fine architecture.' Our stem cell–derived human embryo model offers an ethical and accessible way of peering into this box. 'But that first month is still largely a black box. 'The drama is in the first month, the remaining eight months of pregnancy are mainly lots of growth,' Hanna says. Little is known about the early embryo because it is so difficult to study, for both ethical and technical reasons, yet its initial stages are crucial to its future development.ĭuring these stages, the clump of cells that implants itself in the womb on the seventh day of its existence becomes, within three to four weeks, a well-structured embryo that already contains all the body organs. Given their authentic complexity, the human embryo models obtained by Hanna's group may provide an unprecedented opportunity to shed new light on the embryo's mysterious beginnings.

In addition, they did not have the structural organization characteristic of the embryo and revealed no dynamic ability to progress to the next developmental stage. In particular, they failed to contain several cell types that are essential to the embryo's development, such as those that form the placenta and the chorionic sac. Cellular aggregates derived from human stem cells in previous studies could not be considered genuinely accurate human embryo models, because they lacked nearly all the defining hallmarks of a post-implantation embryo.