This novel stem cell line, created from the addition of a factor known as bone morphogenetic protein (BMP)4 to human pluripotent stem cells (PSCs), is totipotent, meaning the stem cells can not only make all the cells of the embryo but also other cells, including those of the placenta, which are needed to support a developing embryo.
Michael Roberts, professor of animal science at the University of Missouri, USA, and lead author of the study, said: 'BMP-primed cells represent a transitional stage of development between embryonic stem cells and their ultimate developmental fate, whether that is placenta cells, or skin cells or brain cells.
'We can use these new stem cells for future research to better understand how embryos are organized and what causes diseases like pre-eclampsia and other prenatal problems.'
The finding, reported in PNAS, was stumbled upon by chance as Professor Roberts and his team attempted to transform hESCs to placental cells by the addition of BMP4.
The scientists found that addition of BMP4 for a shorter time period than had previously been done, as well as the addition of inhibitors of stem cell pluripotency, left hESCs in a half-way house or 'transitional' stem cell state, rather than turning them into placental cells as expected.
'Previously, the common thought was that embryonic stem cells transitioned straight from stem cells to their end products,' explained Professor Roberts. 'These new stem cells made us realise that embryonic stem cells exist in a number of different transitional states, which likely resemble those encountered in the early stages of embryos.'
He concludes that this novel stem cell line should not only herald advances in placental-related health conditions but to more efficient stem cell research in general.
'We now have new stem cells that are easier to manipulate since they are already at the key transitional precipice before changing into placenta cells, skin cells or any other kind of cell that makes up the human body,' he said.