In Vitro Maturation of Oocytes Retrieved from Ovarian Tissue: Outcomes from Current Approaches and Future Perspectives

Abstract

In vitro maturation (IVM) of transvaginally aspirated immature oocytes is an effective and safe assisted reproductive treatment for predicted or high responder patients. Currently, immature oocytes are also being collected from the contralateral ovary during laparoscopy/laparotomy and even ex vivo from the excised ovary or the spent media during ovarian tissue preparation prior to ovarian cortex cryopreservation. The first live births from in vitro-matured ovarian tissue oocytes (OTO-IVM) were reported after monophasic OTO-IVM, showing the ability to achieve mature OTO-IVM oocytes. However, fertilisations rates and further embryological developmental capacity appeared impaired. The introduction of a biphasic IVM, also called capacitation (CAPA)-IVM, has been a significant improvement of the oocytes maturation protocol. However, evidence on OTO-IVM is still scarce and validation of the first results is of utmost importance to confirm reproducibility, including the follow-up of OTO-IVM children. Differences between IVM and OTO-IVM should be well understood to provide realistic expectations to patients.

Keywords: CAPA-IVM; OTO-IVM; in vitro maturation.

Figure 1

Ovarian tissue preparation for cryopreservation: (a) Bisection of the ovary; (b) Bisected ovary with antral follicles displayed in the medulla; (c) Cortical tissue of which the medulla is removed; (d) Cortical tissue pieces ready for cryopreservation; (e) Residual medulla after it has been mechanically scraped from the cortical tissue; (f) Microscopic view of the Petri dish (e) showing cumulus–oocyte complexes.

Figure 2

Overview of success ratios achieved with current IVM methods [11,13,27,28,35,38,42,43,44,58,59].