The ovarian follicle of ruminants: the path from conceptus to adult

Abstract

This review resulted from an international workshop and presents a consensus view of critical advances over the past decade in our understanding of follicle function in ruminants. The major concepts covered include: (1) the value of major genes; (2) the dynamics of fetal ovarian development and its sensitivity to nutritional and environmental influences;(3) the concept of an ovarian follicle reserve, aligned with the rise of anti-Müllerian hormone as a controller of ovarian processes; (4) renewed recognition of the diverse and important roles of theca cells; (5) the importance of follicular fluid as a microenvironment that determines oocyte quality; (6) the 'adipokinome' as a key concept linking metabolic inputs with follicle development; and (7) the contribution of follicle development to the success of conception. These concepts are important because, in sheep and cattle, ovulation rate is tightly regulated and, as the primary determinant of litter size, it is a major component of reproductive efficiency and therefore productivity. Nowadays, reproductive efficiency is also a target for improving the 'methane efficiency' of livestock enterprises, increasing the need to understand the processes of ovarian development and folliculogenesis, while avoiding detrimental trade-offs as greater performance is sought.

Biological Relationship between Insulin-like Growth Factors (igf1 And Igf2) Genes And Steroidogenesis in Ovine Ovarian Antral Follicles

“…The current study sought to characterize the presence of IGF-1 and -2 in ovine ovarian antral follicles and to identify their functional roles using bioinformatic analysis. Previous studies have utilized IGFs to improve the ovulation rates and litter size in different species including sheep (for a review see (Juengel et al, 2021)). Our study reported that IGF-1 and-2 were markedly observed in the ovine small and large antral follicles.…”

Frontiers in sheep reproduction - making use of natural responses to environmental challenges to manage productivity

“…Recently, in a new consensus paper, Juengel et al (2021) summarized subsequent advances including the paracrine and autocrine actions of the adipokines (eg, adiponectin, chemerin). This situation is complex because most adipokines are produced in more than one variant and, to date, many variants have not been measured.…”

Endothelial cell‐derived fibroblast growth factor‐18 regulates ovarian function in sheep

“…The microenvironment within the follicle also affects follicle development, and factors secreted locally by either granulosa or theca cells can have stimulatory or inhibitory effects on granulosa cell proliferation and follicle function (Juengel et al, 2021). Stimulatory factors include bone morphogenetic protein 4 (BMP4) secreted from theca cells and BMP15 from the oocyte that stimulate granulosa cell proliferation and suppress apoptosis in cattle (Glister et al, 2004; Hussein et al, 2005; McNatty et al, 2005; Shimizu et al, 2012).…”