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Stem cells
Stem cells have the
ability to develop into other cell types, and existing stem cell lines are
already extremely useful for research into development, disease and treatments.
However, the two currently available types of stem cell lines -- Embryonic Stem
cells (ES) and induced Pluripotent Stem cells (iPS) -- have certain
limitations. It is not currently possible for them to form every type of cell
since they are already excluded from developing certain cell lineages.
To discover new stem
cells for use in research and regenerative medicine, the researchers created a
way of culturing cells from the earliest stage of development, when the
fertilised egg has only divided into 4 or 8 cells that are still considered to
retain some totipotency -- the ability to produce all cell types. Their
hypothesis was that these cells should be less programmed than ES cells, which
are taken from the around-100-cell stage of development -- called a blastocyst.
They grew these early cells in a special growth condition that inhibited key
development signals and pathways.
The scientists
discovered that their new cultured cells kept the desired development
characteristics of the earliest cells and named them Expanded Potential Stem
Cells (EPSCs). Importantly, they were also able to reprogramme mouse ES cells
and iPS cells in the new condition and create EPSCs from these cells, turning
back the development clock to the very earliest cell type.
Key words: stem cells, egg, fertilization
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