The scientists, from Kyoto University, first produced healthy mouse pups in 2011 using stem cell-derived sperm. They have now achieved the same by using eggs which were created in the same way.
Scientists are describing the Kyoto team's feat as a "significant achievement" which will have a profound impact on reproductive cell biology and genetics research.
In both cases, the scientists used ES (embryonic stem) cells and iPS (induced pluripotent stem) cells. ES are taken from embryos while iPS come from reprogrammed adult tissue cells that mimic stem cell behavior.
Theory suggests that both ES and iPS cells can produce all the cell types in the body. However, the majority of scientists have not been able to make them turn into germ cells, which eventually become eggs or sperm.
Mitinori Saitou and team hit upon a process that managed to turn stem cells into germ cells. They started off with ES and iPS cells and cultured them into a mix of proteins to produce primordial germ cell-like cells.
Their aim was to get precursor egg cells, known as oocytes. They mixed the primordial cells with fetal ovarian cells, and formed reconstituted ovaries which were grafted onto natural ovaries within live mice. Exactly four weeks and four days later, the primordial germ cell-like cells had turned into oocytes. The ovaries were removed from the mice and the oocytes harvested, fertilized in petri dishes, and the resulting embryos were implanted into surrogate mothers.
Within around three weeks, the surrogate mothers gave birth to healthy mouse pups.
The journal Science quoted Davor Solter, from Singapore's Institute of Medical Biology, as saying:
The team now plan to get a better understanding of the molecular mechanisms that were at work when the germ cells were being formed.
They believe that they may eventually be able to coax the cells through the entire oocyte development process in a lab dish, effectively bypassing the grafting.
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From Stem Cells To Mouse Eggs To Baby Mice - No Father Involved