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