Cyclic activity of signal transduction pathways in fimbrial epithelium of the human fallopian tube

Abstract

Introduction: The local environment of the fallopian tube represents the optimal conditions for reproductive processes. To maintain tissue homeostasis, signal transduction pathways are thought to play a pivotal role. Enhancing our understanding of functional signal transduction pathway activity is important to be able to clarify the role of aberrant signal transduction pathway activity leading to female subfertility and other tubal diseases. Therefore, in this study we investigate the influence of the hormonal cycle on the activity of key signal transduction pathways in the fimbrial epithelium of morphologically normal fallopian tubes.

Material and methods: We included healthy pre- (n = 17) and postmenopausal (n = 8) patients who had surgical interventions for benign gynecologic conditions. Histologic sections of the fallopian tubes were reviewed by two pathologists and, for the premenopausal patients, hormone serum levels and sections of the endometrium were examined to determine the hormonal phase (early follicular [n = 4], late follicular [n = 3], early luteal [n = 5], late luteal [n = 5]). After laser capture microdissection, total mRNA was extracted from the fimbrial epithelium and real-time quantitative reverse transcription-PCR was performed to determine functional signal transduction pathway activity of the androgen receptor (AR), estrogen receptor (ER), phosphoinositide-3-kinase (PI3K), Hedgehog (HH), transforming growth factor-beta (TGF-β) and canonical wingless-type MMTV integration site (Wnt) pathways.

Results: The early luteal phase demonstrated high AR and ER pathway activity in comparison with the late luteal phase (p = 0.016 and p = 0.032, respectively) and low PI3K activity compared with the late follicular phase (p = 0.036), whereas the late luteal phase showed low activity of HH and Wnt compared with the early follicular phase (both p = 0.016). Signal transduction pathway activity in fimbrial epithelium from postmenopausal patients was most similar to the early follicular and/or late luteal phase with regard to the AR, ER and PI3K pathways. Wnt pathway activity in postmenopausal patients was comparable to the late follicular and early luteal phase. We observed no differences in HH and TGF-β pathway activity between pre- and postmenopausal samples. The cyclic changes in signal transduction pathway activity suggest a stage-specific function which may affect the morphology and physiology of the human fallopian tube.

Conclusions: We demonstrated cyclic changes in activity of the AR, ER, PI3K, HH and Wnt pathways throughout the hormonal cycle.

Keywords: computational models; fimbriae; hormonal cycle; human fallopian tube; signal transduction pathways.

FIGURE 1

Line graphs displaying hormone serum concentrations in premenopausal patients during the menstrual cycle. (A) Follicle‐stimulating hormone (FSH) serum concentrations (U/L). (B) Luteinizing hormone (LH) serum concentrations (U/L). (C) Estradiol serum concentrations (nmol/L). Black dots with error bars represent mean concentrations with standard deviations. Gray dots indicate individual patients. Note that in the early follicular phase there is one patient with markedly higher estradiol concentrations, which strongly influenced the mean concentration during this phase. Repeated analysis after exclusion of this patient demonstrated higher estradiol concentrations during the late follicular and late luteal phase when compared with the early follicular and early luteal phase

FIGURE 2

Signal transduction pathway (STP) activity in fimbrial epithelium of fallopian tubes from pre‐ and postmenopausal patients. (A) Androgen receptor (AR). (B) Estrogen receptor (ER). (C) Phosphoinositide‐3‐kinase (PI3K). (D) Hedgehog (HH). (E) Transforming growth factor beta (TGFb). (F) Canonical wingless‐type MMTV integration site (Wnt). (G) Simplified overview of median STP activity scores measured during the menstrual cycle. Direct comparison of the activity scores of the different STPs was not possible, as every STP has his own cell type‐specific range of STP activity. *p < 0.050; **p < 0.010; ¹Patient with a relatively high estradiol serum concentration. Repeated analysis after exclusion of this patient demonstrated minimal changes in significance levels without influencing our conclusions. ²Sample with evidence for oxidative stress