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

Frozen-thawed embryo transfer: does the addition of low-dose choriogonadotropin alfa to progesterone in the luteal phase of artificial cycles improve the endometrium and increase the chances of pregnancy?

OBJECTIVE

Primary: To evaluate the effect of low doses of recombinant hCG (choriogonadotropin alfa) in the luteal phase of frozen-thawed embryo transfers (FET) of artificial cycles on the chances of pregnancy in patients aged ≤38years. Secondary: To assess the chances of pregnancy in the FET groups of artificial cycles using micronized vaginal progesterone (VP) versus injectable intramuscular progesterone (IMP) and the chances of pregnancy in type-1 embryo transfers (two top embryos).

METHODS

This retrospective cohort study included 122 cycles of FET and compared two groups of patients aged 38 years or younger, one given hCG in the luteal phase and one not administered hCG.

RESULTS

The clinical pregnancy rates (CPR) in the control and hCG groups were 45% and 45.16%, respectively (p=0.9999). The live birth rates (LBR) were 33.33% and 32.25%, respectively, (p=0.99909). The CPR in the VP group (83 patients) was 46.89% versus 41.02% in the IMP group, (p=0.5459). The LBR was 33.73% in the VP group and 30.76% in the IMP group (39 patients), (p=0.7559).

CONCLUSIONS

The CPR and LBR of patients undergoing FET in groups prescribed and not prescribed low doses of recombinant hCG were similar. No significant difference was found between patients given VP or IMP.

Expression and function of the luteinizing hormone choriogonadotropin receptor in human endometrial stromal cells

The human luteinising hormone choriogonadotropin receptor (LHCGR) is a G-protein coupled receptor activated by both human chorionic gonadotropin (hCG) and luteinizing hormone (LH), two structurally related gonadotropins with essential roles in ovulation and maintenance of the corpus luteum. LHCGR expression predominates in ovarian tissues where it elicits functional responses through cyclic adenosine mononucleotide (cAMP), Ca²⁺ and extracellular signal-regulated kinase (ERK) signalling. LHCGR expression has also been localized to the human endometrium, with purported roles in decidualization and implantation. However, these observations are contentious. In this investigation, transcripts encoding LHCGR were undetectable in bulk RNA sequencing datasets from whole cycling endometrial tissue and cultured human endometrial stromal cells (EnSC). However, analysis of single-cell RNA sequencing data revealed cell-to-cell transcriptional heterogeneity, and we identified a small subpopulation of stromal cells with detectable LHCGR transcripts. In HEK-293 cells expressing recombinant LHCGR, both hCG and LH elicited robust cAMP, Ca²⁺ and ERK signals that were absent in wild-type HEK-293 cells. However, none of these responses were recapitulated in primary EnSC cultures. In addition, proliferation, viability and decidual transformation of EnSC were refractory to both hCG and LH, irrespective of treatment to induce differentiation. Although we challenge the assertion that LHCGR is expressed at a functionally active level in the human endometrium, the discovery of a discrete subpopulation of EnSC that express LHCGR transcripts may plausibly account for the conflicting evidence in the literature.

Is human chorionic gonadotropin supplementation beneficial for frozen and thawed embryo transfer in estrogen/progesterone replacement cycles?: A randomized clinical trial

Aim

Human chorionic gonadotropin (hCG) is used frequently for luteal support in fresh in vitro fertilization cycles as it induces progesterone secretion from the ovaries after oocyte retrieval and modulates the endometrium for implantation in fresh cycles. In contrast, hCG is not usually used for the transfer of cryopreserved-thawed embryos in estrogen/progesterone replacement cycles because ovulation is suppressed. However, several studies have shown that luteinizing hormone and hCG receptors are present in the human endometrium and that hCG can directly induce the decidualization of endometrial stromal cells in vitro. Thus, this study evaluated whether hCG supplementation can be beneficial for cryopreserved-thawed embryo transfer in estrogen/progesterone replacement cycles.

Methods

One-hundred-and seventy-three cryopreserved-thawed embryo transfer cycles with estrogen/progesterone replacement were divided randomly into two groups. Transdermal oestradiol was used in combination with vaginal progesterone suppositories for HR. The embryo transfer was performed on day 17 and/or day 20 of the HR therapy cycle in both groups. In Group A, 3000 IU of hCG was administered on days 17, 20, and 23. In Group B, hCG was not used.

Results

There was no significant difference in the average age of the patients, the average number of previous assisted reproductive technology cycles, or the average number of embryo transfers between the two groups. The rates of pregnancy and implantation per embryo were 37.2% and 25.3%, respectively, in Group A and 35.6% and 21.7%, respectively, in Group B. The pregnancy and implantation rates were similar in both groups.

Conclusion

Supplementation with hCG is not beneficial for cryopreserved-thawed embryo transfer in estrogen/progesterone replacement cycles.

Expression of LH receptor in nonpregnant mouse endometrium: LH induction of 3β-HSD and de novo synthesis of progesterone

In mouse uterus, at the late diestrus stage LH binding sites have previously been described. The aim of our study was to confirm the existence of LH receptor (Lhr (Lhcgr)) mRNA and its protein in mouse endometrium. Endometrium at all stages of the estrous cycle contained Lhr mRNA, essentially identical to that found in mouse ovary. Endometrium also contained a 72  kDa immunoreactive receptor protein that bound to mouse anti-LHR antibody in western blot. Both receptor mRNA and protein were maximally expressed in the endometrium at metestrus and LH caused a significant increase in their expression levels. Endometrium also contained 3β-hydroxy steroid dehydrogenase (3β-hsd) mRNA and 3β-HSD protein. LH addition elevated their expression and activity as evident from increased conversion of labeled pregnenolone to progesterone (P(4)) and de novo P(4) synthesis. LH-induced endometrial P(4) synthesis is mediated through expression of steroidogenic acute regulatory (Star) gene. Results demonstrated that LH-induced P(4) synthesis in endometrium is possibly mediated through the cAMP pathway. Involvement of a MAPK pathway was also evident. Gonadotropin-stimulated endometrial P(4) synthesis was markedly attenuated by an antagonist of MEK1/2, PD98059. LH-stimulated MEK1/2-dependent phosphorylation of ERK1/2 in a concentration- and time-dependant manner in cultured endometrial tissues. Moreover, involvement of cAMP in LH-stimulated activation of ERK1/2 was also evident. It is therefore possible that the major signaling pathways regulating endometrial steroidogenesis in mouse, including the adenylate cyclase and MAP kinase pathways, converge at a point distal to activation of protein kinase A and ERK1/2.

Human chorionic gonadotropin produced by the invasive trophoblast but not the villous trophoblast promotes cell invasion and is down-regulated by peroxisome proliferator-activated receptor-gamma

A critical step in the establishment of human pregnancy is the invasion of the uterus wall by extravillous cytotrophoblasts (EVCTs) during the first trimester. It is well established that human chorionic gonadotropin hormone (hCG) is secreted by the endocrine syncytiotrophoblast (ST) into the maternal compartment. We recently reported that invasive EVCTs also produce hCG, suggesting an autocrine role in the modulation of trophoblast invasion. Here we analyzed the role of hCG secreted in vitro by primary cultures of invasive EVCT and noninvasive ST. We first demonstrated that LH/CG receptor was present in EVCTs in situ and in vitro as well as in an EVCT cell line (HIPEC65). We next showed that hCG secreted by EVCTs stimulated progesterone secretion by MA10 cells in a concentration-dependent manner. Incubation of HIPEC65 with EVCT supernatants induced a 10-fold increase in cell invasion, whereas ST supernatants had no effect. This stimulating effect was strongly decreased when hCG was depleted from EVCT supernatants containing a large amount of the hyperglycosylated form of hCG, which is almost undetectable in ST supernatants. Finally, we investigated the regulation of hCG expression by peroxisome proliferator-activated receptor (PPAR)-gamma, a nuclear receptor shown to inhibit trophoblast invasion. Activation of PPARgamma decreased alpha- and beta-subunit transcript levels and total hCG secretion in primary EVCTs. Our results offer the first evidence that hCG secreted by the invasive trophoblast, likely the hyperglycosylated form of hCG, but not by the syncytiotrophoblast, promotes trophoblast invasion and may be a PPARgamma target gene in trophoblast invasion process.

Assessment of luteinizing hormone receptor function in an endometrial cancer cell line, Ishikawa cells in response to human chorionic gonadotrophin (hCG)

Luteinizing hormone (LH) and human chorionic gonadotropin (hCG) play an important role in the development and maintenance of male and female gonads. Both these hormones act through the same specific receptor LH/hCG receptor (LHR). Recent studies have shown the existence of functional LHR in several non-gonadal tissues. The aim of this study was to confirm the functional existence of LHR in an endometrial adenocarcinoma cell line, Ishikawa cells, which has been used since long as an in vitro uterine endometrium model. Reverse transcriptase-polymerase chain reaction (RT-PCR) data showed the stable expression of LHR in this cell line. However, the receptor failed to activate the PKA pathway in response to hCG, which is the most conventional mode of LH/hCG action in target tissues. When tested for other pathways, hCG failed to activate them either. Nested RT-PCR confirmed the existence of full-length LHR and this was further supported by Western blot. This study demonstrated that although Ishikawa cells do possess a full-length LHR, which was confirmed by RT-PCR, nested RT-PCR, Western blot and DNA sequencing, it failed to activate the conventional LH-mediated downstream signaling. Based on these data we hypothesize that in Ishikawa cells LH/hCG does not utilize its conventional receptor. Whether it acts through some other receptor is a question, which can be answered through future research.

Is human chorionic gonadotropin directly involved in the regulation of human implantation?

The regulation of human implantation is not fully understood. hCG as one of the earliest embryonal signals may be a major regulator in the parakrine embryo-endometrial communication. The expression of full-length hCG/LH-receptor mRNA could be demonstrated in human endometrium throughout the follicular and secretory phase of the menstrual cycle. In contrast, in early pregnancy decidua only truncated variants could be detected. To investigate direct effects of hCG on the human endometrium, an intrauterine microdialysis device was developed to measure parakrine mediators within the uterine cavity in vivo. Using this system, hCG was applied in the secretory phase and the endometrial response was evaluated. The administration of hCG (500 IU/ml) provoked a significant inhibition of intrauterine IGFBP-1 and M-CSF, while LIF, VEGF and MMP-9 were significantly stimulated. Taken together there appear to be multiple direct effects of hCG on the endometrium that precede the classical endocrine role of the hormone.

Embryo-maternal interactive factors regulating the implantation process: implications in assisted reproductive

The embryo-maternal dialogue that starts very early in the life of the embryo is crucial for its own implantation. A disturbance in this dialogue is the major reason for which 60% of all pregnancies are terminated at the end of the periimplantation period. Many studies have been performed to improve the understanding of the molecular mechanisms involved in this dialogue. Both partners, the mother and the embryo, are equally involved in this exchange of signals. Much progress has been done in understanding the role of (i) chorionic gonadotrophin, (ii) growth factors and cytokines, and (iii) steroid hormones and other mediators, produced either by the embryo, by the mother, or by both, during the peri-implantation period. Today it is clear that their production dictates changes in the endometrium, in the immunological system of the mother and in embryo metabolism, that enable the embryo to implant. Knowledge of the molecular mechanisms involved in the embryo-maternal interaction are reviewed in this article.

Human chorionic gonadotropin and growth factors at the embryonic-endometrial interface control leukemia inhibitory factor (LIF) and interleukin 6 (IL-6) secretion by human endometrial epithelium

BACKGROUND

The elucidation of the molecular mechanisms by which the embryo contributes to its implantation is an area of extensive research. The main objective of this study was to investigate the pattern of leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) secretion by human endometrial epithelium, and their regulation by human chorionic gonadotropin (hCG) and other growth factors present at the embryonic-endometrial interface.

METHODS

Endometrial epithelial cells (EEC) were isolated from biopsies collected at both proliferative and secretory phases of fertile women.

RESULTS

HCG (1-50 IU/ml) increased LIF secretion by EEC cultures derived from follicular phase (up to 285+/-75%) or from secretory phase (up to 212+/-16%). In contrast, hCG reduced IL-6 secretion by EEC in both phases. The hCG/LH receptor gene was transcribed by EEC as evidenced by RT-PCR. Insulin-like growth factors 1 and 2 increased LIF secretion by EEC. Transforming growth factor beta1 stimulated LIF and reduced IL-6 secretion.

CONCLUSIONS

Through hCG, the blastocyst may be involved in the control of its implantation (via an increase of proimplantatory LIF) and tolerance (via an inhibition of proinflammatory IL-6). Other growth factors present at the embryonic-endometrial interface are also involved in the control of LIF and IL-6 endometrial secretion.

Increased expression of human luteinizing hormone/human chorionic gonadotropin receptor mRNA in human endometrial cancer

Fifty randomly selected endometrial tissue samples were used in this study to determine the existence of LH/hCG receptor. Of these, 6 were matched samples of cancerous and surrounding morphologically normal tissues from the same individuals. Conventional RT-PCR, nested RT-PCR, and relative real-time PCR (TaqMan) methods were used to measure the gene expression on the RNA levels. The results show, (1) Real-time PCR can detect LH/hCG receptor expression in all the RNA samples analyzed when conventional RT-PCR only demonstrates the expression of LH/hCG receptor in 17% of the tested samples. (2) Absolute quantitation of LH/hCG receptor by real-time PCR shows higher expression in cancer tissue. This finding was confirmed by the six matched samples. It suggests that LH/hCG receptor gene expresses in endometrium at very low levels and real-time PCR is the best method to detect the expression. Quantitative real-time PCR also reveals increased expressions of LH/hCG receptor in endometrial cancerous tissues compared with surrounding microscopically normal tissues.

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.

Embryo-maternal signalling: how the embryo starts talking to its mother to accomplish implantation

The process of implantation and trophoblast invasion is currently considered as the most limiting factor for the establishment of pregnancy. Molecular interactions at the embryo-maternal interface during the time of adhesion and subsequent invasion are crucial to the process of embryonic implantation. Both partners, the mother as well as the embryo, play equal roles in the embryo-maternal dialogue, the embryonic part being the main topic in this study. Investigations of the proteins in the extra-embryonic matrices (i.e. zona pellucida) indicate that the embryo participates intensively in this early embryo-maternal signalling. One unique feature during implantation process of primate embryos is the release of chorionic gonadotrophin, which seems to influence endometrial activity by two different mechanisms: (i) luteotrophic activity with increasing progesterone release and (ii) a direct action on the endometrium. Furthermore, embryonic interleukin-1beta may be involved in embryo-maternal signalling. Other significant signals in this interaction are most likely leukaemia inhibitory factor (LIF) and colony-stimulating factor (CSF), which stimulate matrix metalloproteinase (MMP)/insulin-like growth factor binding protein-1 (IGFBP-1) activity and the insulin-like growth factor (IGF) system, which is modulated by embryonic IGFBP-3. Similar significances are discussed for uteroglobin and haptoglobin. Finally, the phenomenon of maternal immunological tolerance, triggered by the presence of the early embryo, is fundamental to the understanding of implantation and trophoblast invasion. A tightly regulated balance between activated and inactivated T cells at the implantation site may control the beginning of adequate trophoblast invasion and also limit this invasion to a tolerable extent for the maternal system, consequently ensuring a biologically healthy haemo-chorial placenta.

Signal transduction pathways activated by chorionic gonadotropin in the primate endometrial epithelial cells

Successful implantation requires synergism between the developing embryo and the receptive endometrium. In the baboon, infusion of chorionic gonadotropin (CG) modulates both morphology and physiology of the epithelial and stromal cells of the receptive endometrium. This study explored the signal transduction pathways activated by CG in endometrial epithelial cells from baboon (BE) and human (HES). Incubations of BE and HES cells with CG did not significantly alter adenylyl cyclase activity or increase intracellular cAMP when compared with Chinese hamster ovarian cells stably transfected with the full-length human CG/luteinizing hormone (LH) receptor (CHO-LH cells). However, in BE and HES cells, CG induced the phosphorylation of several proteins, among them, extracellular signal-regulated protein kinases 1 and 2 (ERK 1/2). Phosphorylation of ERK 1/2 in uterine epithelial cells was protein kinase A (PKA) independent. This novel signaling pathway is functional because, in response to CG stimulation, prostaglandin E(2) (PGE(2)) was released into the media and increased significantly 2 h following CG stimulation. CG-stimulated PGE(2) synthesis in epithelial cells was inhibited by a specific mitogen-activated protein kinase (MEK 1/2) inhibitor, PD 98059. In conclusion, immediate signal transduction pathways induced by CG in endometrial epithelial cells are cAMP independent and stimulate phosphorylation of ERK 1/2 via a MEK 1/2 pathway, leading to an increase in PGE(2) release as the possible result of cyclooxygenase-2 activation.

The lutropin/choriogonadotropin receptor, a 2002 perspective

Reproduction cannot take place without the proper functioning of the lutropin/choriogonadotropin receptor (LHR). When the LHR does not work properly, ovulation does not occur in females and Leydig cells do not develop normally in the male. Also, because the LHR is essential for sustaining the elevated levels of progesterone needed to maintain pregnancy during the first trimester, disruptions in the functions of the LHR during pregnancy have catastrophic consequences. As such, a full understanding of the biology of the LHR is essential to the survival of our species. In this review we summarize our current knowledge of the structure, functions, and regulation of this important receptor.

The role of human chorionic gonadotropin on decidualization of endometrial stromal cells in vitro

Although decidualization of endometrial stromal cells (ESC) is crucial for blastocyst implantation and maintenance of pregnancy, its complex mechanism still remains largely unknown. It has long been believed that hCG can directly induce in vitro decidualization of ESC via cAMP signaling. Recently, however, it has been reported that the LH/CG receptor is not present in human endometrium, and the direct effect of hCG on decidualization has become controversial. To reevaluate the exact effect of hCG on decidualization, human ESC were isolated and cultured with hCG and/or ovarian steroids. ESC treated with 17beta-estradiol plus progesterone (E(2)/P) transformed morphologically and produced significant PRL, whereas ESC treated with hCG alone showed no significant increase in PRL in culture medium and exhibited no morphological changes. Moreover, hCG did not promote E(2)/P-induced PRL production or intracellular cAMP accumulation, and protein kinase A inhibitor failed to block E(2)/P-induced PRL production. These results suggest that hCG does not directly affect in vitro decidualization of human ESC and that the process of E(2)/P-induced in vitro decidualization might consist of several pathways, including the intracellular cAMP signaling cascade.

Expression and localization of luteinizing hormone receptor in the female mouse reproductive tract

The presence of the LH receptor (LHR) in nongonadal tissues of the reproductive tract has been reported, but localization studies have not been performed. Our objectives were to demonstrate the presence of LHR in the reproductive tract and to localize receptor expression. Reproductive age rats and mice were obtained and (125)I-hCG binding assays were performed on membrane preparations from the uterus, ovary, liver, and testis. In situ hybridizations were performed using (35)S-labeled antisense and sense RNA probes prepared from nucleotides 1-591 of the mouse LHR cDNA. Specific hCG binding was detected in membrane preparations from the ovary, uterus, and testis but not in the liver in both the rat and mouse. In the ovary, LHR mRNA was localized in theca cells, large follicles, and corpora lutea as expected. In the uterus, LHR mRNA was expressed in stromal cells of the endometrium and in the uterine serosa. Uterine smooth muscle cells had low levels of expression, and the endometrial epithelium was negative. In the oviduct, high levels of LHR expression were noted on the serosa and in subepithelial cells. Oviductal smooth muscle had low expression, and the epithelium was negative. We conclude that functional, nongonadal LHR are expressed in the mouse reproductive tract. The presence and localization of LHR expression in the mouse reproductive tract lay the foundation for transgenic models to address the physiologic role of these receptors.