Equine Chorionic Gonadotropin as an Effective FSH Replacement for In Vitro Ovine Follicle and Oocyte Development.

Chiara Di Berardino,Valentina Russo,Annunziata Mauro,Umberto Tosi,Martina Crociati,Nicola Bernabò,Giulia Capacchietti,Barbara Barboni,Maurizio Monaci,Alessia Peserico

doi:10.3390/ijms222212422

Abstract

The use of assisted reproductive technologies (ART) still requires strategies through which to maximize individual fertility chances. In vitro folliculogenesis (ivF) may represent a valid option to convey the large source of immature oocytes in ART. Several efforts have been made to set up ivF cultural protocols in medium-sized mammals, starting with the identification of the most suitable gonadotropic stimulus. In this study, Equine Chorionic Gonadotropin (eCG) is proposed as an alternative to Follicle Stimulating Hormone (FSH) based on its long superovulation use, trans-species validation, long half-life, and low costs. The use of 3D ivF on single-ovine preantral (PA) follicles allowed us to compare the hormonal effects and to validate their influence under two different cultural conditions. The use of eCG helped to stimulate the in vitro growth of ovine PA follicles by maximizing its influence under FBS-free medium. Higher performance of follicular growth, antrum formation, steroidogenic activity and gap junction marker expression were recorded. In addition, eCG, promoted a positive effect on the germinal compartment, leading to a higher incidence of meiotic competent oocytes. These findings should help to widen the use of eCG to ivF as a valid and largely available hormonal support enabling a synchronized in vitro follicle and oocyte development.

Highlights

Assisted reproductive technologies (ART) aim to overcome human infertility and to optimize reproductive exploitation in domestic animals and the preservation in endangered species.In a female context, most of ART’s success has been through the optimization of the use of fully-grown competent oocytes to generate high quality embryos to be transferred
One challenging biotechnological perspective is to mimic the process of follicle growth in vitro to support the acquisition of gamete meiotic and developmental competences, enlarging the availability on an individual basis of oocytes that can be enrolled with success in in vitro Maturation (IVM)/in vitro Fertilization (IVF) and embryo cultures
The research reported in this paper aimed to study the influence of two different gonadotropins (FSH vs. Equine Chorionic Gonadotropin (eCG)) on in vitro follicle cultures of a single ovine PA follicle, collected at the large secondary stage

Summary

Introduction

Most of ART’s success has been through the optimization of the use of fully-grown competent oocytes to generate high quality embryos to be transferred. This is contrasted by the fact that most individual reproductive resources are enclosed into primordial and growing oocytes. The ivF system has been developed successfully in mice [6,7] but it remains to be translated with efficiency to medium/large mammals This limit is due to the longer period required for follicle/oocyte growth, the greater dimension of antral follicles enclosing competent oocytes and the difficulty in mimicking the environmentally favorable conditions that guarantee a synergic oocyte and somatic compartment development by preserving the tissue architecture [8–17]. To translate the in vitro culture systems to non-rodent models, a better comprehension of the physiology mechanisms triggering follicle growth initiation, sustaining the interplay between germinal and somatic compartment, and supporting the basic metabolic needs of early growing follicles, are required

Objectives

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Conclusion