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In a first, scientists have taken human eggs from their earliest stages in the ovaries all the way to the most mature stage, all in a laboratory setting.

The breakthrough could lead to new fertility treatments for some women – especially females who develop cancer at a young age, but eventually want to have children themselves, report the scientists in the journal Molecular Human Reproduction.

“The ability to develop human oocytes from the earliest follicular states in vitro through to maturation and fertilization would benefit fertility preservation practice,” tha authors conclude.

The scientists from the University of Edinburgh and the Center for Human Reproduction in Manhattan found 10 volunteers. The women were undergoing elective caesarian section, and ranged from 25 to 39 years old.

The cortical biopsies of the ovaries were tiny – approximately 5 mm by 4 mm with variable thicknesses – and then dissected into thin strips. Then began a process of multi-step process of segregation and observation.

Growing follicles were removed, and then cultured in a medium for eight days. Then the tissue was further dissected to be cultured another eight days. At that point, a majority of the follicles had reached a crucial stage of development.

The most promising cumulus oocyte complexes were “retrieved by gentle pressure” from the follicles – and those were cultured for another four days.

A total of nine of the complexes were oocytes that had emitted a polar body, matured and resumed meiosis in the medium, the scientists report.

“This is a small number of samples but provides proof of concept that complete development of human oocytes can occur in vitro,” they write. “Further optimization with morphological evaluation and fertilization potential of (in vitro grown) oocytes is required to determine whether they are normal.”

"We also hope to find out, subject to regulatory approval, whether they can be fertilized,” said Evelyn Telfer, one of the Edinburgh authors, in a school statement.

The breakthrough follows similar advances in mice and in non-human primates. But the new breakthrough in human cells means not only fertility treatments – but also more research opportunities, the scientists add.

“Apart from the clinical implications of this work, the system described here provides direct access to the process of human oogenesis in an experimentally tractable paradigm for future research,” they write.

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