Localization and variable expression of G alpha(i2) in human endometrium and Fallopian tubes

BACKGROUND

Heterotrimeric G proteins take part in membrane-mediated cell signalling and have a role in hormonal regulation. This study clarifies the expression and localization of the G protein subunit G alpha(i2) in the human endometrium and Fallopian tube and changes in G alpha(i2) expression in human endometrium during the menstrual cycle.

METHODS

The expression of G alpha(i2) was identified by Polymerase chain reaction (PCR), and localization confirmed by immunostaining. Cyclic changes in G alpha(i2) expression during the menstrual cycle were evaluated by quantitative real-time PCR.

RESULTS

We found G alpha(i2) to be expressed in human endometrium, Fallopian tube tissue and in primary cultures of Fallopian tube epithelial cells. Our studies revealed enriched localization of G alpha(i2) in Fallopian tube cilia and in endometrial glands. We showed that G alpha(i2) expression in human endometrium changes significantly during the menstrual cycle, with a higher level in the secretory versus proliferative and menstrual phases (P < 0.05).

CONCLUSIONS

G alpha(i2) is specifically localized in human Fallopian tube epithelial cells, particularly in the cilia, and is likely to have a cilia-specific role in reproduction. Significantly variable expression of G alpha(i2) during the menstrual cycle suggests G alpha(i2) might be under hormonal regulation in the female reproductive tract in vivo.

Endometrial, subendometrial, and ovarian stromal blood flow in patients treated with two different doses of recombinant human chorionic gonadotropin

The effects of two different doses of recombinant hCG on blood flow to the uterus and ovary on the day of oocyte retrieval were studied by three-dimensional Doppler ultrasonography in 60 women during IVF treatment. There were no differences in all the indices of endometrial, subendometrial, and ovarian stromal blood flow in women who had received 250 microg or 500 microg of recombinant hCG for final oocyte maturation.

Human chorionic gonadotropin contributes to maternal immunotolerance and endometrial apoptosis by regulating Fas-Fas ligand system

The first known hormonal signal of the conceptus during implantation is human chorionic gonadotropin (hCG). Interestingly, increased apoptosis in human endometrium coincides with the implantation window. Factors from the fetal or placental origin as well as maternal hormonal factors are likely to have a potential role in the regulation of apoptotic signaling molecules. We hypothesized that hCG may be a placental link for the development of local maternal immunotolerance. Fas-Fas ligand (FasL) system is one of the apoptotic signaling pathways, shown to be important in the development of local immune tolerance during and after implantation. We report that hCG treatment decreases cell proliferation and increases apoptosis in endometrial cells. Moreover, hCG stimulates FasL mRNA and protein expression without affecting Fas mRNA in these cells. Interestingly, in coculture experiments, hCG-treated endometrial cells induce an increase in T cell apoptosis. Our in vivo results reveal that cells of early pregnancy decidua express strong FasL immunoreactivity, and decidual areas containing interstitial cytotrophoblasts have numerous TUNEL-positive cells. Compared with decidual areas devoid of interstitial cytotrophoblasts, we observed in decidual areas containing interstitial cytotrophoblasts clearly less amount of TUNEL-positive cells. These results suggest that hCG may be a link in the development of peritrophoblastic immune tolerance and may facilitate the trophoblast invasion by regulating proapoptotic molecules such as FasL in endometrial cells.

Evidence for cycle-dependent expression of full-length human chorionic gonadotropin/luteinizing hormone receptor mRNA in human endometrium and decidua

OBJECTIVE

To investigate the expression of full-length and truncated hCG/LH-receptor mRNA in human endometrium and decidua.

DESIGN

In vitro experiment.

SETTING

Tertiary university center.

PATIENT(S)

Premenopausal women undergoing hysterectomy because of benign diseases or induced abortions.

INTERVENTION(S)

Isolation of RNA from endometrial samples, reverse transcription, selective preamplification of full-length hCG/LH receptor mRNA and several shorter fragments of the receptor gene (exons 1-11, 1-10, and 1-5), nested polymerase chain reaction with internal primers.

MAIN OUTCOME MEASURE(S)

Appropriately sized cDNA product confirmed by sequencing.

RESULT(S)

All samples derived from the proliferative as well as from the early and mid-luteal phases were positive for all four amplification products, suggesting the expression of a full-length hCG/LH receptor mRNA. Only 5 of 8 samples derived from the late secretory phase and 2 of 12 samples derived from early decidua amplified the entire receptor sequence. In contrast, the shortest fragment (exons 1-5), coding for part of the extracellular receptor domain, was amplified in all samples.

CONCLUSION(S)

The data suggest cycle-dependent regulation of hCG/LH-receptor mRNA by changes in the alternative splicing pattern and down-regulation of full-length hCG/LH receptor mRNA in early decidua. The major splicing site appears to be located between introns 5 and 9. Alternative splicing may be a mechanism regulating hCG/LH-receptor down-regulation.

Intrauterine microdialysis reveals cycle-dependent regulation of endometrial insulin-like growth factor binding protein-1 secretion by human chorionic gonadotropin

OBJECTIVE

To investigate whether hCG may directly influence endometrial differentiation and function.

DESIGN

Controlled clinical study.

SETTING

Tertiary university center.

PATIENT(S)

Fifty-six women with infertility.

INTERVENTION(S)

An intrauterine microdialysis device (IUMD) was developed that consisted of two balloon catheters connected by microdialysis tubing (molecular weight cutoff: 2,000 kDa). The IUMD was inserted into the uterine cavity and perfused with saline for 3 hours. In 45 women, urinary hCG was then added for 5 hours. Eleven women underwent an identical procedure but without the application of hCG.

MAIN OUTCOME MEASURE(S)

The response of the endometrium was assessed by measuring IGFBP-1 in the perfusate.

RESULT(S)

Intrauterine secretion of IGFBP-1 was strictly confined to the late secretory phase (>or=10 days after the beginning of the LH peak). This time point marks the closing of the implantation window. The application of hCG did not affect intrauterine IGFBP-1 levels before day 10 but induced a significant decrease of intrauterine IGFBP-1 levels thereafter. There was no significant change of intrauterine IGFBP-1 levels in the controls.

CONCLUSION(S)

Intrauterine microdialysis allows a dynamic assessment of endometrial paracrine function in vivo. Human chorionic gonadotropin may be involved in the mechanisms regulating endometrial receptivity.

Modulation of the baboon (Papio anubis) uterine endometrium by chorionic gonadotrophin during the period of uterine receptivity

This study was undertaken to determine the modulation of uterine function by chorionic gonadotrophin (CG) in a nonhuman primate. Infusion of recombinant human CG (hCG) between days 6 and 10 post ovulation initiated the endoreplication of the uterine surface epithelium to form distinct epithelial plaques. These plaque cells stained intensely for cytokeratin and the proliferating cell nuclear antigen. The stromal fibroblasts below the epithelial plaques stained positively for alpha-smooth muscle actin (alphaSMA). Expression of alphaSMA is associated with the initiation of decidualization in the baboon endometrium. Synthesis of the glandular secretory protein glycodelin, as assessed by Western blot analysis, was markedly up-regulated by hCG, and this increase was confirmed by immunocytochemistry, Northern blot analysis, and reverse transcriptase-PCR. To determine whether hCG directly modulated these uterine responses, we treated ovariectomized baboons sequentially with estradiol and progesterone to mimic the hormonal profile of the normal menstrual cycle. Infusion of hCG into the oviduct of steroid-hormone-treated ovariectomized baboons induced the expression of alphaSMA in the stromal cells and glycodelin in the glandular epithelium. The epithelial plaque reaction, however, was not readily evident. These studies demonstrate a physiological effect of CG on the uterine endometrium in vivo and suggest that the primate blastocyst signal, like the blastocyst signals of other species, modulates the uterine environment prior to implantation.

Messenger ribonucleic acid for the gonadal luteinizing hormone/human chorionic gonadotropin receptor is not present in human endometrium

OBJECTIVE

To determine whether messenger RNA for the gonadal LH/hCG receptor is present in human endometrium with the use of reverse-transcriptase polymerase chain reaction.

DESIGN

In vitro experiment.

SETTING

Academic medical center.

PATIENT(S)

Premenopausal women who were not receiving hormonally active medications and who were undergoing hysterectomy for uterine leiomyomas, menorrhagia, pelvic pain, or uterine prolapse.

INTERVENTION(S)

Tissue from hysterectomy specimens was processed for RNA and treated with deoxyribonuclease where appropriate, and RNA was reverse-transcribed to complementary DNA.

MAIN OUTCOME MEASURE(S)

An appropriately sized band after reverse-transcriptase polymerase chain reaction, followed by sequencing to confirm the results.

RESULT(S)

A primer pair that spanned the extracellular domain was unable to amplify receptor complementary DNA from human endometrial tissue. For a primer pair that spanned transmembrane regions 2-6 of the receptor and was contained wholly in exon 11, a 552-base pair fragment was amplified successfully in 19 of 25 human endometrial samples.

CONCLUSION(S)

The traditional gonadal LH/hCG receptor does not appear to be present in human endometrial tissue. The presence of a portion of the transmembrane part of the molecule suggests that human endometrium may express a truncated or variant form of the receptor.