O-294 In-vitro maturation of oocytes from ovary tissue and ovarian longevity
Authors: Silber S.J , Goldsmith S , Castleman L , Hayashi K 
Published: June 2022

Abstract

Study question
Is it possible to accomplish simple and robust in-vitro maturation (IVM) of oocytes from human ovarian tissue using principles of in vitro gametogenesis?

Summary answer
Many mature oocytes can be obtained from ovary tissue with simple media and no need for ovarian stimulation.

What is known already
IVM from ovarian tissue has been difficult in the past. To mature primordial follicles in vitro has become possible in mice utilizing eight ‘core genes’. It has not yet been performed in humans, and will be complicated. However, culturing germinal vesicle oocytes that have already become meiotically competent by in-vivo IVD and IVG would not be expected to be difficult. In addition, it is far easier to obtain many germinal vesicle oocytes with cortical dissection rather than with a needle.

Study design, size, duration
After the ovarian cortex has been dissected from the medulla and divided into slices for cryopreservation, the ‘spent’ medium in which the dissection took place was examined for free, loose cumulus complexes, and cultured for 24 to 48 hours. A variety of different culture media and gonadotrophin concentrations were employed, based on previously published data from in vitro gametogenesis in mice.

Participants/materials, setting, methods
A total of 119 female patients between age 2 and 35 years old underwent ovary cryopreservation (as well as in-vitro maturation of oocytes and IVM in the last 13 individuals) over a 24 year period. Up to 22 years later, 17 returned to have their ovary tissue thawed and transplanted back.

Main results and the role of chance
Every woman had return of ovarian function 5 months after transplant, similar to previous observations. As observed before, AMH concentration rose as FSH fell 4 months later. The grafts continued to work up to 8 years. Of the 17, 13 (76%) became pregnant with intercourse at least once, resulting in 19 healthy live births, including six live births from three women who had leukemia. Of the harvested germinal vesicle oocytes, 35% developed with simple culture media into mature metaphase II oocytes. Maturation of germinal vesicle to MII oocytes was detected between 24 and 48 h of exposure to the HCG-containing media. For most participants, the number of mature oocytes was what would be obtained from ovarian stimulation. Surprisingly, the success of IVM was not related to the specific media or to the concentration of gonadotrophin in the media. A variety of media and concentrations were intentionally used in light of now-established mechanisms of in-vitro oogenesis, to see if this understanding could be used for a simplification of IVM.

Limitations, reasons for caution
This is an early pilot study only, but the results are strikingly consistent with our extensive work with IVG in mice.

Wider implications of the findings
This study and the results of in-vitro gametogenesis reveal the limited role of the ovulatory cycle and ovarian stimulation in oocyte development other than for the oocyte to exit the ovary. The normal ovulation cycle is not needed for meiotic competence. Ovarian stimulation is only required for easy oocyte retrieval.

Trial registration number
Not applicable