Immunoprofiling of human uterine mast cells identifies three phenotypes and expression of ERβ and glucocorticoid receptor

Abstract

Background: Human mast cells (MCs) are long-lived tissue-resident immune cells characterised by granules containing the proteases chymase and/or tryptase. Their phenotype is modulated by their tissue microenvironment. The human uterus has an outer muscular layer (the myometrium) surrounding the endometrium, both of which play an important role in supporting a pregnancy. The endometrium is a sex steroid target tissue consisting of epithelial cells (luminal, glandular) surrounded by a multicellular stroma, with the latter containing an extensive vascular compartment as well as fluctuating populations of immune cells that play an important role in regulating tissue function. The role of MCs in the human uterus is poorly understood with little known about their regulation or the impact of steroids on their differentiation status. The current study had two aims: 1) To investigate the spatial and temporal location of uterine MCs and determine their phenotype; 2) To determine whether MCs express receptors for steroids implicated in uterine function, including oestrogen (ERα, ERβ), progesterone (PR) and glucocorticoids (GR). Methods: Tissue samples from women (n=46) were used for RNA extraction or fixed for immunohistochemistry. Results: Messenger RNAs encoded by TPSAB1 (tryptase) and CMA1 (chymase) were detected in endometrial tissue homogenates. Immunohistochemistry revealed the relative abundance of tryptase MCs was myometrium>basal endometrium>functional endometrium. We show for the first time that uterine MCs are predominantly of the classical MC subtypes: (positive, +; negative, -) tryptase+/chymase- and tryptase+/chymase+, but a third subtype was also identified (tryptase-/chymase+). Tryptase+ MCs were of an ERβ+/ERα-/PR-/GR+ phenotype mirroring other uterine immune cell populations, including natural killer cells. Conclusions: Endometrial tissue resident immune MCs have three protease-specific phenotypes. Expression of both ERβ and GR in MCs mirrors that of other immune cells in the endometrium and suggests that MC function may be altered by the local steroid microenvironment.

Non‐IgE mediated mast cell activation

“…However, additional anti‐inflammatory functions of glucocorticoids can also be observed rapidly within seconds to minutes, which excludes a nuclear effect. MCs were shown recently to express the GR in the RBL‐2H3 cell line, but also in human uterine MC . Numerous functional consequences of glucocorticoid exposure in MCs have been reported.…”

SULFATION PATHWAYS: Contribution of intracrine oestrogens to the aetiology of endometriosis

“…Notably, ERβ but not ERα is present in the vascular endothelium of the human and non-human primate endometrium and appears to regulate the E2 responsiveness of these cells consistent with oestrogen regulation of angiogenesis (Critchley et al 2001, Greaves et al 2013. The impact of E2 on diverse immune cell populations may also be regulated by ERβ as the receptor has been detected in the nuclei of uterine natural killer (uNK) (Henderson et al 2003) and mast cells (De Leo et al 2017). Notably, recent studies have demonstrated that uNK cells treated with E2 release the chemokine CCL2, which promotes endometrial endothelial cells to form angiogenesis networks (Gibson et al 2015).…”

Significance of mast cells in spermatogenesis, implantation, pregnancy, and abortion: Cross talk and molecular mechanisms

“…Moreover, chymase + MCs were distributed in the basal compartment of the endometrium and the myometrium. MC TC subtype was found in all layers . MC accumulation in endometriotic lesions is evident, and MC‐derived proteases play a role in fibrogenesis and accumulation of type I collagen in endometriosis during all stages of cycle .…”