Bitter Taste Receptors Expression in Human Granulosa and Cumulus Cells: New Perspectives in Female Fertility.

Bianca Semplici,Sofia Passaponti,Claudia Landi,Alice Luddi,Laura Governini,Paola Piomboni,Francesca Paola Luongo,Vincenzo De Leo,Giuseppe Morgante

doi:10.3390/cells10113127

Abstract

Bitter taste receptors (TAS2RS) expression is not restricted to the oral cavity and the presence of these receptors in the male reproductive system and sperm provides insights into their possible role in human reproduction. To elucidate the potential role of TAS2Rs in the female reproductive system, we investigated the expression and localization of bitter taste receptors and the components of signal transduction cascade involved in the pathway of taste receptors in somatic follicular cells obtained from women undergoing assisted reproductive techniques. We found that TAS2R genes are expressed in both cumulus (CCs) and granulosa (GCs) cells, with TAS2R14 being the most highly expressed bitter receptor subtype. Interestingly, a slight increase in the expression of TAS2R14 and TAS2R43 was shown in both GCs and CCs in young women (p < 0.05), while a negative correlation may be established between the number of oocytes collected at the pickup and the expression of TAS2R43. Regarding α-gustducin and α-transducin, two Gα subunits expressed in the taste buds on the tongue, we provide evidence for their expression in CCs and GCs, with α-gustducin showing two additional isoforms in GCs. Finally, we shed light on the possible downstream transduction pathway initiated by taste receptor activation in the female reproductive system. Our study, showing for the first time the expression of taste receptors in the somatic ovarian follicle cells, significantly extends the current knowledge of the biological role of TAS2Rs for human female fertility.

Highlights

Cumulus and granulosa cells were isolated from the cumulus–oocyte complex and follicular fluid of patients undergoing assisted reproduction, in whom the recovered oocyte pool included only mature metaphase II stage
B) that appears to be significantly modulated, with TAS2R14 being the most expressed in both granulosa cells (GCs) and in CCs (p < 0.001)
We provide for the first time evidence on the expression of TAS2Rs in GCs and CCs, the somatic cells surrounding the oocyte, which are considered critical for oocyte development and the fertilization process

Summary

Introduction

Female fertility is the result of a finely controlled and specialized process during which the oocyte grows within the ovarian follicle, the functional unit that provides and influences the maturation and quality of the oocyte within it [1]. The preovulatory ovarian follicle is a follicular niche composed of highly differentiated cells (granulosa and cumulus cells) lining the antrum filled with follicular fluid. This complex biological fluid is derived from the ultrafiltration of serum and secretion of the cells lining the follicle itself (both granulosa and cumulus cells); the follicular fluid provides a very important microenvironment and contains regulatory molecules, such as protein hormones, steroids, and electrolytes, which are important for oocyte maturation and quality [2,3,4]. The close connection between the somatic cells and the oocyte itself, which are structurally and metabolically dependent on each other, suggests that the health status of these cells is closely related to the quality of the oocyte [6,7,8]

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