Stanniocalcin-1 expression in normal human endometrium and dysregulation in endometriosis

Abstract

Objective: To determine expression of stanniocalcin-1 (STC1) in human endometrium with and without endometriosis and its regulation by steroid hormones.

Design: Laboratory study.

Setting: University.

Patient(s): Nineteen women with endometriosis and 33 control women.

Intervention(s): Endometrial biopsy and fluid sampling.

Main outcome measure(s): Analysis of early secretory (ESE) and midsecretory (MSE) endometrial secretomes from fertile women with the use of nano-liquid chromatography-dual mass spectrometry; real-time quantitative polymerase chain reaction, and immunohistochemistry for STC1 and its receptor calcium-sensing receptor (CASR) mRNA and proteins in endometrium with and without endometriosis; evaluation of STC1 and CASR mRNA expression in endometrial stromal fibroblasts (eSF) from women with and without endometriosis decidualized with the use of E2P or 8-bromo-cyclic adenosine monophosphate (cAMP).

Result(s): STC1 protein was strongly up-regulated in MSE versus ESE in endometrial fluid of fertile women. STC1 mRNA significantly increased in MSE from women with, but not from those without, endometriosis, compared with proliferative endometrium or ESE, with no significant difference throughout the menstrual cycle between groups. STC1 mRNA in eSF from control women increased >230-fold on decidualization with the use of cAMP versus 45-fold from women with endometriosis, which was not seen on decidualization with E2/P. CASR mRNA did not exhibit significant differences in any condition and was not expressed in isolated eSF. STC1 protein immunoexpression in eSF was significantly lower in women with endometriosis compared with control women.

Conclusion(s): STC1 protein is significantly up-regulated in MSE endometrial fluid and is dysregulated in eutopic endometrial tissue from women with endometriosis. It is likely regulated by cAMP and may be involved in the pathogenesis of decidualization defects.

Keywords: Stanniocalcin-1; decidualization; endometriosis; human endometrium; proteomics; stromal fibroblasts.

Figure 1

A. Stanniocalcin-1 (STC1) protein level is increased in receptive (LH+8) phase endometrial secretome. Paired data from six (n=6) fertile women are presented. X-axis values have been obtained by taking log2 from summed peptide peak areas of STC1 protein in different samples. Paired t-test p-value indicated with significance accepted at p≤0.05. B. Relative expression of STC1 and CASR mRNA in human endometrial tissue throughout the menstrual cycle in women with and without endometriosis. C. Expression of STC1 and CASR mRNA in human endometrial tissue throughout the menstrual cycle in women with endometriosis normalized to samples from women without endometriosis and expressed as fold change. Significance accepted at p≤0.05. PE: proliferative phase endometrium, ESE: early secretory phase endometrium, and MSE: mid-secretory phase endometrium. Non-parametric one-way ANOVA Kruskal-Wallis test was used for statistical analysis, and significance was accepted at p≤0.05.

Figure 2

A. Immunochemical evaluation of STC1 protein expression in mid-secretory human endometrium from women without and with endometriosis. LE=luminal epithelium and GE=glandular epithelium. * - statistically significant difference between LE and GE, and between GE and stroma, p<0.02; # - statistically significant difference in stromal staining between no endometriosis and endometriosis samples, p=0.04. Magnification ×200. One-way Kruskal-Wallis test was used for statistical analysis, with significance accepted at p≤0.05. B. Immunochemical evaluation of CASR protein expression in mid-secretory human endometrium from women without and with endometriosis. No stromal expression of CASR was observed, and no difference in epithelial (luminal and glandular) staining was noted between specimens from women with versus without endometriosis. Magnification ×200.

Figure 3

Expression of STC1 mRNA in decidualized human endometrial stromal fibroblasts A. with 0.5 mM cAMP for 96 hours, normalized to 96 hour control, or B. with 10 nM E₂ / 1 μM P₄ for 14 days, normalized to 14 day control. One-way Kruskal-Wallis test was used for statistical analysis, with significance accepted at p≤0.05.