Molecular analysis of human endometrium: short-term tibolone signaling differs significantly from estrogen and estrogen + progestagen signaling

Abstract

Tibolone, a tissue-selective compound with a combination of estrogenic, progestagenic, and androgenic properties, is used as an alternative for estrogen or estrogen plus progesterone hormone therapy for the treatment of symptoms associated with menopause and osteoporosis. The current study compares the endometrial gene expression profiles after short-term (21 days) treatment with tibolone to the profiles after treatment with estradiol-only (E(2)) and E(2) + medroxyprogesterone acetate (E(2) + MPA) in healthy postmenopausal women undergoing hysterectomy for endometrial prolapse. The impact of E(2) treatment on endometrial gene expression (799 genes) was much higher than the effect of tibolone (173 genes) or E(2) + MPA treatment (174 genes). Furthermore, endometrial gene expression profiles after tibolone treatment show a weak similarity to the profiles after E(2) treatment (overlap 72 genes) and even less profile similarity to E(2) + MPA treatment (overlap 17 genes). Interestingly, 95 tibolone-specific genes were identified. Translation of profile similarity into biological processes and pathways showed that ER-mediated downstream processes, such as cell cycle and cell proliferation, are not affected by E2 + MPA, slightly by tibolone, but are significantly affected by E(2). In conclusion, tibolone treatment results in a tibolone-specific gene expression profile in the human endometrium, which shares only limited resemblance to E(2) and even less resemblance to E2 + MPA induced profiles.

Fig. 1

SHBG measurements before and after treatment. Sera were collected for each patient just before the start of treatment (pre) and 21 days later just before hysterectomy (post). The bold lines represent the averages of the measured values

Fig. 2

Cluster and correlation analyses of endometrial gene expression profiles obtained after short-term (21 days) treatment with E₂, E₂ + MPA, or tibolone. Using statistical analysis, it was established that 3,293 probe sets (representing 2,312 known and 466 unknown genes) deviated at least threefold, in at least one patient sample, from the geometrical means of all treated samples. These genes were used for the cluster and correlation analyses. a At the bottom of the figure, relatedness is indicated. Red indicates genes with a higher expression relative to the geometrical means, while blue indicates genes with a lower expression relative to the geometrical means. The numbers (#) behind the treatments indicate the patient numbers. b The correlation values are between 1 (dark red, diagonal line) and −1 (dark blue, not represented here). The white boxes represent no correlation between profiles

Fig. 3

A gene expression network of E₂- and tibolone-regulated genes involved in the regulation of the cell cycle. From top to bottom, genes are acting in extracellular space, plasma membrane, cytoplasm, or nucleus. The colors indicate upregulation (red), downregulation (green) or no regulation (not colored). The intensity of colors indicates the magnitude of regulation (darker means more pronounced). Relations between genes are indicated with gray lines and functions of genes by the shape of the gene name boxes. Rectangle Nuclear receptor, square cytokine, vertical diamond enzyme, horizontal diamond peptidase, triangle kinase, quadrangle transporter, ellipse transcription factor, circle other function

Fig. 4

Array data compared to RT-PCR results. The array signal intensities (top) of tested genes were normalized relative to GAPDH. The RT-PCR signals (bottom) were normalized relative to 18sRNA signals. Solid black bars represent data from control patients, solid white bars represent data from tibolone-treated patients, dashed gray bars represent data from E₂ + MPA treated patients, and the solid gray bars represent data from E₂-treated patients