Like all mammals, girls’ ovaries contain all the eggs (oocytes) that
individual will ever produce before she is even born. Once she reaches sexual
maturity, the eggs begin to ripen on a regular schedule. If the ovaries were
irreversibly damaged before that time, that woman will never produce fertile
eggs. Therefore, when young girls must undergo cancer treatments, doctors make every effort to safeguard their future fertility.
Digital camera shot though a microscope; human primary
follicle.
By
Jpogi, 3/3/2007
It is now possible to cryo-preserve
ovarian tissue without damaging the follicles that will eventually give rise to
the oocytes. Unfortunately, it has been nearly impossible to activate these
immature follicles so that they produce fertilizable oocytes. University
of Gothenburg scientists may now be able to change that paradigm.
The researchers found that a protein with the rather
improbable name of ‘phosphatase and tensin homolog deleted on chromosome ten’
(PTEN) is responsible for inhibiting follicle activation. By in turn inhibiting
PTEN, they were able to get neonatal mouse ovarian tissue to mature properly.
When transplanted into donor mice, the ovarian tissue produced mature oocytes
that could be harvested and fertilized. The resultant offspring were themselves
fertile and healthy. If this works as well in humans, ovarian tissue could be
removed from young girls undergoing toxic therapies and frozen until the child
was grown and ready to become a mother. At that time, the ovarian tissue could
be treated with the PTEN inhibitor [bpV(HOpic), in case you were wondering], and
re-implanted.
PTEN actually has a number of functions, not least of which
is as a tumor suppressor. Therefore, the scientists gave mice high dosages of
the PTEN inhibitor to test for increased rates of cancer. No such increase was
detected. Obviously, many more safety tests will have to be conducted before
this treatment is approved for humans.
Adhikari D, Gorre N, Risal S, Zhao Z, Zhang H, Shen Y, & Liu K (2012). The safe use of a PTEN inhibitor for the activation of dormant mouse primordial follicles and generation of fertilizable eggs. PloS one, 7 (6) PMID: 22761722
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