Anterior Gradient Protein 3 and S100 Calcium-Binding Protein P Levels in Different Endometrial Epithelial Compartments May Play an Important Role in Recurrent Pregnancy Failure.

Nicola Tempest,Josephine Drury,Christopher J Hill,Dharani K Hapangama,Hannan Al-Lamee,Elizabeth Batchelor,Andrew J Drakeley

doi:10.3390/ijms22083835

Abstract

Recurrent implantation failure (RIF) and recurrent pregnancy loss (RPL) are distressing conditions without effective treatments. The luminal epithelium (LE) is integral in determining receptivity of the endometrium, whereas functionalis glands and stroma aid in nurturing early embryo development. Calcium signalling pathways are known to be of vital importance to embryo implantation and pregnancy establishment, and anterior gradient protein 3 (AGR3) and S100 calcium-binding protein P (S100P) are involved with these pathways. We initially examined 20 full-thickness endometrial biopsies from premenopausal women across the menstrual cycle to characterize levels of AGR3 protein in each endometrial sub-region at the cellular level. A further 53 endometrial pipelle biopsies collected in the window of implantation were subsequently assessed to determine differential endometrial AGR3 and S100P levels relevant to RIF (n = 13) and RPL (n = 10) in comparison with parous women (n = 30) using immunohistochemistry. Significantly higher AGR3 and S100P immunostaining was observed in ciliated cells of the LE of women with recurrent reproductive failure compared with parous women, suggesting aberrant subcellular location-associated pathophysiology for these conditions. The nuclear localisation of S100P may allow transcriptional regulatory function, which is necessary for implantation of a viable pregnancy. Further work is thus warranted to assess their utility as diagnostic/therapeutic targets.

Highlights

Recurrent reproductive failure is a devastating reproductive health issue that may manifest in two ways: (i) recurrent implantation failure (RIF) during in vitro fertilization (IVF) treatment cycles or (ii) recurrent pregnancy loss (RPL)
Sci. 2021, 22, 3835 levels to be consistently high in the luminal epithelium (LE) throughout the proliferative and secretory phases of the menstrual cycle compared with the functionalis and basalis epithelium, which demonstrated much lower levels of anterior gradient protein 3 (AGR3) (Figure 1A,B)
Using immunofluorescence and the ciliated cell marker acetylated-α tubulin co-localisation with AGR3, we demonstrated similar endometrial AGR3 immunostaining in ciliated epithelial cells as previously observed in the lung (Figure 1C)

Summary

Introduction

Recurrent reproductive failure is a devastating reproductive health issue that may manifest in two ways: (i) recurrent implantation failure (RIF) during in vitro fertilization (IVF) treatment cycles or (ii) recurrent pregnancy loss (RPL). There are no universally accepted definitions of RPL, and the loss of two [5,6] or three [7] consecutive pregnancies [6,7] have been proposed, with most studies reporting the prevalence to be 1–2% of women [5,7]. Unexplained RPL and RIF have no effective treatments, and presumably the causes are multifactorial, a hostile endometrial environment is likely implicated. Both conditions are highly distressing for patients and treatment constitutes one of the most difficult challenges for clinicians in the field [3,8,9]. The luminal epithelium (LE) (the uppermost layer of the endometrium) is the first maternal layer of cells that an embryo communicates with during the window of implantation (WOI) [10]; it is central to determining the receptivity of the endometrium [11]

Methods

Results

Conclusion