P-795 Robust and simple in vitro maturation of ovarian tissue oocytes
Authors: Goldsmith S , Silber S 
Published: July 2024

Abstract

Study question
Using in-vitro gametogenesis results in mice, can we perform simple, robust in-vitro maturation (IVM) of oocytes from human ovarian tissue?

Summary answer
In vitro oogenesis in mice reveals 3 phases of oocyte maturation, IVD, IVG, and IVM. In vivo IVD and IVG simplifes a more robust IVM.

What is known already
For fertility preservation in cancer patients, IVM of GV’s obtained from ovary tissue with live birth has been achieved, but the results are variable, and great effort has gone into trying to make the “right” culture media, and most are given booster shots of gonadotropin with questionable results. It is easy to obtain many GV oocytes from tiny follicles using open cortical dissection. But it still has remained a puzzle how to do robust IVM in the best way.

Study design, size, duration
A total of 146 females underwent ovary tissue cryopreservation since 1977. The most recent 38 consecutive such patients between 2 and 38 years of age underwent in-vitro maturation of oocytes (IVM) derived from their ovarian tissue. This is a prospective non-randomized pilot study based upon our results with in vitro oogenesis.

Participants/materials, setting, methods
After ovarian cortex dissection, the spent media is examined for cumulous complexes (CC’s), which were placed in culture with widely varying concentrations of FSH and HCG, and in a variety of different media. Based on now established mechanisms of in vitro oogenesis, we postulated that the specific media for IVM and the concentrations of HCG would not impact results. There was no prior hormone administration.

Main results and the role of chance
The harvested germinal vesicle oocyte developed into mature metaphase II oocytes with simple culture media just as well as with “IVM media”, and with HCG concentration from 10 mIU/l to 1000 mIU/l. Of the 38 cases, 18 had had previous chemotherapy or were pre-pubertal. None of these had CC’s. Of the 20 who were post-pubertal and had not yet undergone chemotherapy, the number of CC’s averaged 20 per patient. Of a total of 402 GV oocytes, 137 became mature MII’s (34.1%), varying between 20% and 56%. The only case with low maturation rate (9%) occurred when the cumulus was stripped immediately instead of at 24 hours. Thus mature oocytes can robustly and easily be obtained from ovary tissue with simple media and no need for ovarian stimulation. Furthermore, ovarian stimulation and ovulation are not necessary for oocyte maturation. Oocytes that have just exited IVD that have been exposed to less than 7 days of gonadotropin (IVG) will not mature. Those oocytes exposed to more than 11 days of IVG will degenerate. Thus about 35% of oocytes at any given time will have already been properly prepared in vivo for IVM.

Limitations, reasons for caution
This is an early proof of concept study in humans with only 30 participants. However, it is completely consistent with what we have predicted from in vitro oogenesis in the mouse.

Wider implications of the findings
Ovary tissue freezing along with robust IVM will at once provide cancer patients with two possibilities for fertility preservation, without having to delay cancer treatment. Four months of in vivo IVD (non-hormonal) followed by 11 days of IVG (FSH) have already prepared oocytes for IVM.

Trial registration number
not applicable