Until now it hasn’t been possible to isolate human naïve stem cells, even though we’ve had the technology to do it in mice for thirty years – leading some people to doubt it would be possible.
- Ge Guo
As well as a potential source of stem cells for use in regenerative medicine, the technique could open up new avenues of research into disorders such as Down’s syndrome.
The ability to derive naïve stem cells has been possible for over thirty years from mouse embryos, using a technique developed by Sir Martin Evans and Professor Matthew Kaufman during their time at Cambridge, but this is the first time this has been possible from human embryos.
Human pluripotent stem cells for use in regenerative medicine or biomedical research come from two sources: embryonic stem cells, derived from fertilised egg cells discarded from IVF procedures; and induced pluripotent stem cells, where skin cells are reprogrammed to a pluripotent form. However, these cells are already “primed” for differentiation into specific cell types. In contrast, all instructions have been erased in naïve cells, which may make it easier to direct them into any cell type of interest.
Recently naïve-like human induced pluripotent stem cells have been created by reprogramming but it has been unknown whether they can also be obtained directly from the human embryo.
When an egg cell is fertilised by a sperm, it begins to divide and replicate before the embryo takes shape. Around day five, the embryonic cells cluster together and form a structure called the ‘blastocyst’. This occurs before implantation into the uterus. The blastocyst comprises three cell types: cells that will develop into the placenta and allow the embryo to attach to the womb; and cells that form the ‘yolk sac’, which provides nutrients to the developing foetus; and the ‘epiblast’ comprising the naïve cells that will develop into the future body.
In research published in the journal Stem Cell Reports, scientists from the Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute managed to remove cells from the blastocyst at around day six and grow them individually in culture. By separating the cells, the researchers in effect stopped them ‘talking’ to each other, preventing them from being steered down a particular path of development.
“Until now it hasn’t been possible to isolate these naïve stem cells, even though we’ve had the technology to do it in mice for thirty years – leading some people to doubt it would be possible,” explains Ge Guo, the study’s first author, “but we’ve managed to extract the cells and grow them individually in culture. Naïve stem cells have many potential applications, from regenerative medicine to modelling human disorders.”
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Image:Colonies of human naïve embryonic stem cells grown on mouse feeder cells
Credit: Ge Guo
Reproduced courtesy of the University of Cambridge
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