Technologies for the Production of Fertilizable Mammalian Oocytes

Gianna Rossi,Stefania Annarita Nottola,Iman Halvaei,Guido Macchiarelli,Valentina Di Nisio,Lucia De Santis,Sandra Cecconi

doi:10.3390/app9081536

Abstract

Women affected by ovarian pathologies or with cancer can usually preserve fertility by egg/embryo freezing. When oocyte retrieval is not feasible, the only option available is ovarian tissue cryopreservation and transplantation. The culture of follicles isolated from fresh or cryopreserved ovaries is considered still experimental, although this procedure is considered safer, because the risk of unintentional spreading of cancer cells eventually present in cryopreserved tissue is avoided. Animal and human small follicles can be cultured in vitro, but standardized protocols able to produce in vitro grown oocytes with the same developmental capacity of in vivo grown oocytes are not available yet. In fact, the different sizes of follicles and oocytes, the hormonal differences existing between mono- (e.g., human, goat, cow, and sheep) and poly-ovulatory (rodents and pig) species, and the incomplete identification of the mechanisms regulating the oocyte–follicle and follicle–ovary interrelationships affect the outcome of in vitro culture. From all these attempts, however, new ideas arise, and the goal of assuring the preservation of female reproductive potential appears a more realistic possibility. This review surveys and discusses advances and challenges of these technologies that, starting from a simple attempt, are now approaching the biosynthesis of a functional engineered ovary.

Highlights

What is the meaning of the term “infertility”? According to the most recent literature, infertility corresponds to the failure to achieve a clinical pregnancy after 12 months or after 6 months of regular unprotected sexual intercourse
Starting from consideration that an in vitro culture system has to assure the production of competent oocytes the by considerationthe that an infeatures vitro culture to assure theseveral production of competent by reproducing unique of the system in vivo has grown follicles, protocols have been oocytes developed reproducing the unique features ofresults the in vivo grownon follicles, several protocols developed during these years, with discrepant depending the species studied
Technical modifications need to be confirmed at morphological and molecular levels, because it is mandatory to determine whether In Vitro Grown (IVG) oocytes are “normal”

Summary

Introduction

According to the most recent literature, infertility corresponds to the failure to achieve a clinical pregnancy after 12 months (women < 35 years) or after 6 months (women > 35 years) of regular unprotected sexual intercourse. It affects 8–12% of reproductive-aged couples worldwide, a percentage that may even increase up to 25% for couples living in Western Countries [1,2,3]. The terms infertility and subfertility can be used interchangeably, subfertility more generally addresses any form or grade of reduced fertility. Infertility should be differentiated from impairment of

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