Stem cells isolated from the skin of pig fetuses are capable of giving rise to egg-like cells, according to a paper published in the April issue of Nature Cell Biology.
Embryologists have long sought to understand when and where germ cells - which give rise to sperm and eggs - are formed. The stem cells in the early embryo give rise to all the different lineages of the fetus, including the germ-cell lineage. In mammals, germ cells become segregated from non-germ cells (called somatic cells) during embryonic development and migrate into the gonads, where they form sperm or eggs. Now, Julang Li and colleagues show that even post-embryonic somatic stem cells (derived from later stages of foetal development) can also give rise to egg-like cells in vitro.
They found that when skin-derived stem cells from pig fetuses were grown in vitro for 30-40 days under specific conditions known to be important for egg formation, they expressed markers normally found in germ cells and produced egg-forming cell aggregates. After a further 10-15 days, these cell aggregates extruded large egg-like cells that expressed markers specific for meiosis - the specialized cell division programme that gives rise to sperm and eggs. Li and colleagues also showed that a subset of these egg-like cells spontaneously underwent parthenogenesis - producing embryo-like structures without fertilisation.
Although it remains unclear whether these eggs can be fertilized to form viable embryos, the ability to generate egg-like cells from cells derived from the skin provides new possibilities for tissue therapy and reproductive engineering and offers a powerful in vitro model for the study of egg development
Julang Li (University of Guelph, Guelph, Canada)
Abstract available online.
(C) Nature Cell Biology press release.
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