Uterine Transcriptome: Understanding Physiology and Disease Processes

In recent years, transcriptomics has enabled us to gain a deeper understanding of fundamental reproductive physiology, including the menstrual cycle, through a more precise molecular analysis. The endometrial mRNA transcript levels fluctuate during the normal menstrual cycle, indicating changes in the relative recruitment and abundance of inflammatory cells, as well as changes in the receptivity and remodeling of the endometrium. In addition to providing a more comprehensive understanding of the molecular underpinnings of pathological gynecological conditions such as endometriosis, leiomyomas, and adenomyosis through RNA sequencing, this has allowed researchers to create transcriptome profiles during both normal menstrual cycles and pathological gynecological conditions. Such insights could potentially lead to more targeted and personalized therapies for benign gynecological conditions. Here, we provide an overview of recent advances in transcriptome analysis of normal and pathological endometrium.

Expression of the epidermal growth factor system in human endometrium during the menstrual cycle

The epidermal growth factor (EGF) system is ubiquitous in humans and plays fundamental roles in embryogenesis, development, proliferation and differentiation. As the endometrium of fertile women is characterized by proliferation and differentiation, we hypothesize a role for the EGF system. Fourteen premenopausal women had endometrial samples removed on day 6 +/- 1 and day 6 +/- 1 and 12 +/- 1 after ovulation during one menstrual cycle. RNA was extracted and analysed by real-time PCR, and immunohistochemistry was performed to localize the components of the EGF system. Human EGF Receptor 1 (HER1) showed highest expression during the proliferative phase, HER2 and HER4 during the early and HER3 during the late secretory phase. Amphiregulin (AR) and transforming growth factor alpha (TGFalpha) expression is highest in proliferative phase. Heparin binding (HB)-EGF and betacellulin (BCL) show no variation. Epiregulin (EP) is detectable in some samples. EGF is undetectable. HER1, HER2, HER3 and HER4 were localized to the epithelium and glands HER3 and HER4 solely in the secretory phase. Amphiregulin was seen in leucocytes and stromal cells, TGFalpha and betacellulin in the epithelial lining, epiregulin in stromal cells whereas HB-EGF and EGF are undetectable. In conclusions, we observed cyclical expression of the four EGF receptors and two ligands and localized all four receptors and four ligands in endometrial biopsies. This suggests a role for the EGF system in growth of the endometrium.

In vivo assessment of the regulation of transforming growth factor alpha, epidermal growth factor (EGF), and EGF receptor in the human endometrium by medroxyprogesterone acetate

PURPOSE

The present study evaluated the in vivo effect of medroxyprogesterone acetate (MPA) on the localization of immunoreactive transforming growth factor alpha (TGFalpha), epidermal growth factor (EGF), and their common receptor (EGF-R) in the human endometrium.

METHODS

The study design was a randomized clinical trial enrolling 36 healthy women with regular menstrual cycles. The participants were randomly assigned into three groups: groups 1 (n = 11) and 2 (n = 17) received placebo and were submitted to endometrial biopsy during the proliferative and secretory phases of menstrual cycle, respectively; group 3 (n = 8) received MPA (10 mg/day) for 10 days followed by endometrial biopsy, which was performed during the secretory phase. Immunohistochemistry was used to localize TGFalpha, EGF, and EGF-R in the endometrial tissue.

RESULTS

TGFalpha was present markedly in the luminal and glandular epithelia but also in the periglandular stroma, with a distribution pattern similar in the three experimental groups. EGF immunostaing was equally distributed in epithelial and stromal layers of the endometrium and remained unchanged in endometrial samples from women treated with MPA compared to placebo. EGF-R was expressed only in the epithelium. The intensity of EGF-R immunostaining was higher in secretory than in proliferative endometrium and was further increased by administration of MPA (p < 0.05, chi-square test).

CONCLUSION

The present results suggest that the progestogen-induced in vivo differentiation of secretory endometrium does not require dramatic changes in the expression of EGF or TGFalpha, whereas EGF-R may be up regulated.

Specificity of the localization of transforming growth factor-alpha immunoreactivity in colon mucosa

Transforming growth factor-alpha (TGF-alpha) plays an important role in gastrointestinal pathophysiology. However, the exact location of its expression in the intestine is still controversial. This study systematically compared the localization of TGF-alpha immunoreactivity in frozen or fixed human colon using three different antibodies and examined specificity of antibodies by using tissues from TGF-alpha knockout mice and by Western blotting. Consistent with the mRNA distribution revealed by in situ hybridization, a similar staining pattern was obtained in frozen sections by all three antibodies, localizing on the surface and along the crypt epithelium. In paraffin sections, although the polyclonal antibodies (raised against recombinant human or rat TGF-alpha) gave minimal staining, the monoclonal antibody (against C-terminal peptide of human TGF-alpha) still gave intense staining on the surface and upper crypt epithelium. By using specimens from TGF-alpha knockout mice in immunostaining and Western blotting, the polyclonal antibodies were shown to be specific. In contrast, specificity of the monoclonal antibody was in doubt in rodent tissues because it gave similar detection between wild-type and knockout mice in both analyses, indicating its crossreaction to non-TGF-alpha molecules. In conclusion, frozen sections and antibodies raised from recombinant TGF-alpha should be used for TGF-alpha immunohistochemistry in the colon.