The Calcium-Sensing Receptor Is Involved in Follicle-Stimulating Hormone-Induced Cumulus Expansion in in vitro Cultured Porcine Cumulus-Oocyte Complexes.

Huage Liu,Xianhong Mo,Dan Zhou,Xiangwei Fu,Yan Luo,Qingrui Zhuan,Cong Liu,Yunpeng Hou

doi:10.3389/fcell.2021.625036

Abstract

The Calcium-Sensing Receptor (CASR) is a G protein-coupled receptor of the C family that reportedly promotes maturation of porcine oocytes. However, its role in cumulus expansion of cumulus-oocyte complexes (COCs) is not well known. This study was conducted to determine the role of CASR and potential mechanisms involved during in vitro maturation (IVM) of porcine COCs. After culture of COCs in follicle-stimulating hormone (FSH)-supplement maturation medium for 24 h, the time of breakdown of the germinal vesicle (GVBD), indicative of initiation of meiotic maturation, resulted in an increased (p < 0.05) CASR mRNA expression level in cumulus cells. Moreover, IVM of COCs in 10 μM of the CASR agonist NPS R-568 promoted (p < 0.05) cumulus expansion but only in FSH-containing medium. Conversely, 20 μM of the CASR inhibitor NPS2390 precluded cumulus expansion. We next tested the effect of the CASR agonist/inhibitor on the expression of cumulus expansion-related genes. The CASR agonist significantly upregulated the expression of hyaluronan acid synthase 2 (HAS2), whereas the CASR inhibitor downregulated the expression of all HAS2, prostaglandin-endoperoxide synthase 2 (PTGS2), and tumor necrosis factor a-induced protein 6 (TNFAIP6). Altogether, these results suggest that CASR activity is involved in FSH-stimulated porcine cumulus expansion.

Highlights

During follicular development, mammalian oocytes undergo a series of important changes induced by the pre-ovulatory surge of gonadotropins (Eppig, 1996)
Culture of cumulus-oocyte complexes (COCs) for 24 h in FSHcontaining medium upregulated the expression of Calcium-Sensing Receptor (CASR) mRNA in cumulus cells (p < 0.05; Figure 2)
To determine whether CASR was involved in cumulus expansion in vitro and, if so, whether the presence of follicle-stimulating hormone (FSH) was critical, either the CASR agonist NPS R-568 or inhibitor NPS2390 were added to the maturation medium in different treatments

Summary

Introduction

Mammalian oocytes undergo a series of important changes induced by the pre-ovulatory surge of gonadotropins (Eppig, 1996). FSH enhances cumulus expansion during in vitro culture of canine (Lee et al, 2007) and mouse (Eppig, 1979a) cumulus-oocyte complexes (COCs). Epidermal growth factor (EGF) can stimulate cumulus expansion in vitro in mouse (Downs, 1989; Boland and Gosden, 1994) and bovine (Lorenzo et al, 1994). FSH (Nagyová et al, 1999) and EGF (Procházka et al, 2000; Jezová et al, 2001)-induced cumulus expansion correlated with the synthesis of hyaluronan by porcine cumulus cells and its accumulation. The expression of genes involved in the production of hyaluronic acid and its organization in the extracellular matrix, such as hyaluronan acid synthase 2 (HAS2), prostaglandin-endoperoxide synthase 2 (PTGS2), and tumor necrosis factor a-induced protein 6 (TNFAIP6), is increased preceding cumulus expansion in mouse COCs (Park et al, 2004)

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