Oocyte quality following in vitro follicle development†

Abstract

In vitro follicle development (IVFD) is an adequate model to obtain basic knowledge of folliculogenesis and provides a tool for ovarian toxicity screening. IVFD yielding competent oocytes may also offer an option for fertility and species preservation. To promote follicle growth and oocyte maturation in vitro, various culture systems are utilized for IVFD in rodents, domestic animals, wild animals, nonhuman primates, and humans. Follicle culture conditions have been improved by optimizing gonadotropin levels, regulatory factors, nutrient supplements, oxygen concentration, and culture matrices. This review summarizes quality assessment of oocytes generated from in vitro-developed antral follicles from the preantral stage, including oocyte epigenetic and genetic profile, cytoplasmic and nuclear maturation, preimplantation embryonic development following in vitro fertilization, as well as pregnancy and live offspring after embryo transfer. The limitations of oocyte quality evaluation following IVFD and the gaps in our knowledge of IVFD to support proper oocyte development are also discussed. The information may advance our understanding of the requirements for IVFD, with a goal of producing competent oocytes with genetic integrity to sustain embryonic development resulting in healthy offspring.

Keywords: follicle culture; in vitro follicle development; oocyte competence; oocyte maturation; oocyte quality.

Figure 1

Bridging the gap to improving oocyte competence in IVFD. Follicles from early developmental stages can develop to the antral stage in vitro in the optimized culture systems. Comparing follicles developed in vitro and in vivo will identify critical factors that can improve IVFD to produce mature oocytes competent for embryonic development resulting in live offspring in various species. 2D, two-dimensional; 3D, three-dimensional; IVM, in vitro maturation.