A paracrine interaction between granulosa cells and leukocytes in the preovulatory follicle causes the increase in follicular G-CSF levels

Laure Noël,Michelle Nisolle,Nathalie Jacobs,Maïté Fransolet,Carine Munaut,Jean-Michel Foidart

doi:10.1007/s10815-020-01692-y

Laure Noël, Michelle Nisolle + Show 4 more

Open Access

https://doi.org/10.1007/s10815-020-01692-y

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Abstract

ObjectiveFollicular granulocyte colony-stimulating factor (G-CSF) is a new biomarker of oocyte quality and embryo implantation in in vitro fertilization (IVF) cycles. Its role in reproduction is poorly understood. Our study aimed to investigate the mechanisms and cells responsible for G-CSF production in the preovulatory follicle.DesignLaboratory research study.SettingSingle-center study.InterventionsGranulosa cells and leukocytes were isolated from the follicular fluids (FF) or the blood of women undergoing IVF and from the blood of a control group of women with spontaneous ovulatory cycles to perform cocultures.Main outcome measureG-CSF-secreted protein was quantified in the conditioned media of cocultures.ResultsG-CSF secretion was considerably increased in cocultures of granulosa cells and leukocytes. This effect was maximal when leukocytes were isolated from the blood of women in the late follicular phase of the menstrual cycle or from the FF of women undergoing IVF. The leukocyte population isolated from the FF samples of women undergoing IVF had a higher proportion of granulocytes than that isolated from the corresponding blood samples. Leukocytes induced the synthesis and secretion of G-CSF by granulosa cells. Among a range of other FF cytokines/chemokines, only growth-regulated oncogene alpha (GROα) was also increased.ConclusionThe notable rise in G-CSF at the time of ovulation coincides with the accumulation of follicular granulocytes, which stimulate G-CSF production by granulosa cells via paracrine interactions. High follicular G-CSF concentrations may occur in follicles with optimal granulosa–leukocyte interactions, which could explain the increased implantation rate of embryos arising from these follicles.

Highlights

Follicular fluid (FF) surrounds the oocyte and constitutes the milieu in which signaling molecules circulate between granulosa cells and the oocyte during folliculogenesis and oocyte maturation [1]
CD45negative human granulosa cells and CD45-positive follicular leukocytes were isolated from the FF of women undergoing in vitro fertilization (IVF), and CD45-positive blood leukocytes were isolated from their peripheral blood (Fig. 1a and b)
granulocyte colony-stimulating factor (G-CSF) protein, as detected by ELISA assay, was secreted by CD45-negative human granulosa cells (hGC) and fCD45 leukocytes isolated from the FF of women undergoing IVF and by the human granulosaderived cell line HGL5 after 48 h of culture (Fig. 2a–d)

Summary

Introduction

Follicular fluid (FF) surrounds the oocyte and constitutes the milieu in which signaling molecules circulate between granulosa cells and the oocyte during folliculogenesis and oocyte maturation [1]. FFs are collected with the oocytes during in vitro fertilization (IVF) procedures and are discarded after oocyte retrieval. FF represents a source of non-invasive biomarkers of oocyte quality. A competent oocyte is able to be fertilized and to support the first steps of embryo development [2]; only 30% of retrieved oocytes will develop into a good quality embryo and 5% will result in a live birth [3, 4]. Oocyte quality assessment remains a challenge in IVF, since morphology is poorly predictive of oocyte competence [5].

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