Follicle development and selection: past, present and future

Abstract

This paper reviews progress that has been made over the last 50 years and discusses how the development and application of new technologies have been utilized to increase our understanding of the development and selection of the dominant follicle. Our increased knowledge from research carried out worldwide, has demonstrated that the development of the dominant follicle, and importantly the production of a good quality oocyte, are controlled by a set of complex and interactive extra-and intra-ovarian control systems, impacted by underlying genetic and external environmental factors, such as nutrition. In totality this has resulted in improvements in fertility, as demonstrated by the impact of diet on oocyte quality and increased pregnancy rates. However, given the increasing global challenges of food security, coupled with climate change, more in-depth understanding of these complex multifactorial control systems will have even greater significance in overcoming today's livestock production challenges, including some that were present over 50 years ago. In conclusion, the continuing development of new technologies, coupled with new knowledge and understanding of these complex control systems, should ensure that ruminant fertility is maximized, while ensuring good animal welfare within sustainable production systems.

Membrane Estrogen Receptor (GPER) and Follicle-Stimulating Hormone Receptor (FSHR) Heteromeric Complexes Promote Human Ovarian Follicle Survival

“…Conversely, GPER KO mice feature pathological conditions such as altered glucose and lipid metabolism ( Sharma and Prossnitz, 2016 ) and tumorigenesis ( Marjon et al., 2014 ), without any specific reproductive phenotype ( Prossnitz and Hathaway, 2015 ). However, the mouse is a multiovulatory species, and species-specific mechanisms underlying the endocrine regulation of multi- versus mono-ovulation are different ( Driancourt et al., 1991 ; Webb et al., 2016 ). Whether FSHR-GPER heteromerization results from the evolution in mono-ovulatory mammals is a topic of future studies.…”

Membrane estrogen receptor (GPER) and follicle-stimulating hormone receptor heteromeric complexes promote human ovarian follicle survival

“…Conversely, GPER KO mice feature pathological conditions such as altered glucose and lipid metabolism 64 and tumorigenesis 65 , without any specific reproductive phenotype 66 . However, the mouse is a multiovulatory species and species-specific mechanisms underlying the endocrine regulation of multi-vs. mono-ovulation are different 67,68 . Whether FSHR-GPER heterodimerization results from the evolution in mono-ovulatory mammals is a topic of future studies.…”

Necessity for LH in selection and continued growth of the bovine dominant follicle

“…Numerous studies have attempted to understand the molecular, cellular, paracrine, hormonal, and follicular dynamics that produce selection of a single dominant follicle from the cohort of follicles that are growing during a follicular wave (Fortune et al 1991, Ginther et al 1996, Crowe 1999, Ireland et al 2000, Mihm et al 2002, Webb et al 20022016, Scaramuzzi et al 2011, Ginther 2016, Garcia-Guerra et al 2018) and yet all the mechanisms involved in this process have not been defined. This study focused on the role of circulating LH during the follicle selection mechanism.…”

“…The use of precise characterization of follicular wave dynamics during ablation of LH pulses using acute treatment with a potent GnRH antagonist, Acyline, and subsequent replacement of LH action using a specific LHr agonist, hCG, allowed substantial insight into the hormonal control of follicle selection. The bovine model is particularly informative because of the extensive previous characterization of follicle dynamics and the complexities during follicle selection under different physiological conditions (Adams & Pierson 1995, Ginther et al 1996, 2016, Garcia-Guerra et al 2018, Gomez-Leon et al 2019.…”

“…Previous research in our laboratory (Haughian et al 2013) found that short-term treatment with a GnRH antagonist, Acyline, during the first follicular wave suppressed GnRH-stimulated LH secretion but not circulating FSH and led to cessation of growth of the largest follicle at about 8 mm with inhibition of follicle diameter deviation and a subsequent increase in circulating FSH concentration . Other more chronic models, such as hypophysectomy (Mcnatty et al 1990), hypothalamo-pituitary disconnection (Clarke et al 1983), immunization against GnRH (Crowe et al 2001a,b), or chronic treatment with GnRH receptor antagonist (Taylor et al 2004, Webb et al 2016 or potent GnRH agonist (Gong et al 1996) indicated a role for LH but also a need for FSH in order to complete follicle development. However, acute experimental depression of LH by an acute GnRH antagonist treatment, leaving circulating FSH at normal concentrations, combined with the replacement of only LH action has not been used to determine the temporal relationship between the reduction in F1 growth and the transitional period and whether deficient LH accounted for the lack of the development of follicle dominance.…”