Determination of Follicular Localization in Human Ovarian Cortex for Vitrification

To determine the optimal follicle localization for ovarian vitrification in adolescent and young adult (AYA)-aged (between 15 and 39 years of age) patients with cancer or primary ovarian insufficiency (POI).

In total, ovaries from 24 women were included in our study. These include women who received ovariectomy for fertility preservation before gonadotoxic treatments for cancer (n = 4), or for the treatment of POI by the in vitro activation method (n = 8), and other women and infants (0-3 years of age) whose ovaries were autopsied (n = 12). Before cryopreservation, a portion of the ovary sampled from cancer and POI patients was used for histological analysis. Depths of follicles from the surface of ovarian cortices were then measured by using digital imaging software. The locations of the follicles at different developmental stages in the ovarian cortex were noted.

The mean depth at which the primordial and primary follicles were located was 271 μm in infants. This was deeper in women in their twenties, thirties, and forties (501, 462, and 493 μm, respectively). The majority of secondary follicles were located <1000 μm from the ovarian surface (mean depth, 639 μm). In regard to patients with POI, the mean depth of primordial and primary follicles was 566 μm, whereas 70% of secondary follicles were located >1000 μm deep.

These findings suggest that <1 mm is a potential optimum thickness of normal ovarian tissue for vitrification and a requirement that thicker ovarian cortices include secondary follicles in POI patients.