P-173 Neuregulin 1 supplementation and sequential stimulation improve post-IVM embryo production
Authors: Buratini J , Dellaqua T , Degli Esposti M , Dos Santos Carneiro D , Romeiro Silva N , Gabrielli de Souza C , Mignini Renzini M , Dal Canto M 
Published: June 2023

Abstract

Study question
Can supplementation with neuregulin 1 during a pre-IVM culture step followed by sequential stimulation with FSH and amphiregulin improve IVM outcomes?

Summary answer
Supplementation with neuregulin 1 during a pre-IVM culture step followed by sequential stimulation with FSH and amphiregulin improves post-IVM bovine embryo production

What is known already
Evidence that gradual activation of the maturation cascade favours nuclear-cytoplasmic synchrony and cumulus-oocyte communication has motivated the investigation of pre-IVM culture steps. In vivo, the cumulus-oocyte complex (COC) is first exposed to increased FSH levels, after which final maturation is triggered by EGF-like factors secreted by granulosa cells. We have demonstrated that supplementation of the IVM medium with neuregulin 1 (NRG1), a modulatory EGF-like factor, improves oocyte developmental competence. Herein, we utilized the bovine model to assess the impacts of NRG1 supplementation during pre-IVM and sequential exposure to FSH and amphiregulin (AREG) during IVM on post-IVF embryo development

Study design, size, duration
Bovine COCs were subjected to a pre-IVM culture with (group NS) or without NRG1 (groups D and S). Subsequently, COCs were subjected to direct (group D) or sequential IVM with FSH followed by AREG stimulation (groups S and NS). Post-IVF production of total and high quality (expanded and hatched) blastocysts was compared between groups by ANOVA followed by the Fisher Protected test (n = 3 replicates, each with 20-25 oocytes per treatment-group)

Participants/materials, setting, methods
Germinal stage vesicle COCs were aspirated from 2-8mm follicles of abattoir bovine ovaries, pooled in groups of 20-25 and subjected to pre-IVM for 9h in the “Follicular System” (FS)-preIVM medium, with or without 1ng/mL NRG1, followed by IVM in the FS-IVM medium for 24h. In sequential IVM, COCs were first subjected to a 6h culture in the FS-IVM medium without AREG and, subsequently, to a 18h culture in the complete FS-IVM medium (AREG 100ng/mL)

Main results and the role of chance
Supplementation of NRG1 during pre-IVM combined with sequential IVM with FSH followed by AREG stimulation increased post-IVF embryo development as assessed by the percentage of the total oocytes subjected to pre-IVM/IVM generating total and high quality (expanded and hatched) blastocysts. Total blastocyst rates were 34.34 ± 1.66%, 40.26 ± 1.94% and 45.94 ± 3.04% for groups D, S and NS, respectively (P = 0.032). Rates of high quality blastocysts were 30.53 ± 1.47%, 29.71 ± 2.36% and 38.56 ± 1.91%, for groups D, S and NS, respectively (P = 0.036)

Limitations, reasons for caution
Our study is subjected to the intrinsic limitations of the use of an animal model. Treatment effects may vary with different biological activities associated with different batches and suppliers of EGF-like factors

Wider implications of the findings
Our findings contribute for a better understanding of the mechanisms regulating oocyte developmental competence and constitute novel parameters for the improvement of IVM efficacy. Therefore, our data may contribute for the development of infertility treatment strategies with reduced hormonal cost and patient discomfort

Trial registration number
Not applicable