The presence of chorionic gonadotrophin beta subunit in normal cyclic human endometrium

Expression and production of human chorionic gonadotropin (hCG) in the normal secretory endometrium: evidence of CGB7 and/or CGB6 beta hCG subunit gene expression

We have previously confirmed glandular cell CGB and CGA subunit mRNA gene expression as well as the expression of their dimeric and single-subunit human chorionic gonadotropin (hCG) proteins in normal secretory transformed endometrium. The objective of this study was to investigate the endometrial epithelial gene locus of the human hCG/LH gene cluster from CGB genes responsible for gene expression. For this study, endometrial specimens were selected from women characterized using our endometrium score and hCG staining index that had normal secretory transformed endometrium and optimal hCG staining. Using full-length CGB mRNA sequence analysis, we found that epithelial CGB is (co)expressed as the product of gene locus CGB7 and CGB6 (48%), as single CGB7 (42%), or to a lower percentage as single CGB6 (10%). In addition to known differences between these genes and CGB5, the nucleotide sequence of the mRNA differs between CGB7 and CGB6 in the untranslated promoter region and in translated exon 2. Immunohistochemical results show that endometrial joint CGB7 and CGB6, single CGB7, and single CGB6 mRNA expression lead to the release of endometrial hCG. Gene-specific antibodies for CGB7 reveal secretory endometrial hCG production, which is not observed for gene-specific CGB5 antibodies, whereas the placenta is positive for CGB5 and negative for CGB7 antibody as revealed by immunohistochemistry and Western blot hCG isoform analysis. Only endometrial CGB7 expression seems to be supported specifically by secretory endometrial transcription factors. In conclusion, epithelial hCG is expressed and produced as CGB7 and/or CGB6 but not CGB5, and it is produced together with CGA as a secretory transformation marker in the normal secretory phase endometrium.

Recurrent pre-clinical pregnancy loss is unlikely to be a 'cause' of unexplained infertility

BACKGROUND

A proportion of women with 'unexplained' infertility may present with subfertility because their pregnancies fail before they are clinically recognized. In order to test whether pre-clinical early pregnancy losses (EPL) occur more frequently in women with unexplained infertility, serial urinary hCG concentrations were measured to compare EPL per cycle rates following spontaneous conception in patients with unexplained infertility versus healthy volunteers.

METHODS

Sixty patients under 39 years of age with unexplained infertility and 60 healthy controls, who were trying to conceive spontaneously, participated in this study. All participants were asked to collect daily urine samples from cycle day 14 until menstruation for three consecutive cycles or until a positive pregnancy test was obtained. Urinary hCG and creatinine levels were measured by immunoassay. Implantation was detected when urinary hCG levels rose above reference levels constructed from samples obtained from 12 women not attempting to conceive. EPL rates were determined by a linear mixed model using logarithmically transformed hCG/creatinine data.

RESULTS

In the 133 cycles of 60 women with unexplained infertility, just one implantation was detected, which became an ongoing pregnancy. In contrast, in 103 such cycles in 46 control patients, 30 implantations were detected (24 clinical pregnancies, 6 cases of EPL). The odds ratio for EPL/cycle in the unexplained versus control group was 0 (95% confidence interval: 0-0.795, P = 0.026).

CONCLUSIONS

Our data do not support the hypothesis that recurrent EPL may present as unexplained infertility. Post-implantation failure is therefore unlikely to contribute significantly to the presentation of subfertility.

Epithelial human chorionic gonadotropin is expressed and produced in human secretory endometrium during the normal menstrual cycle

The objective of this study was to determine whether beta human chorionic gonadotropin (hCG) (CGB) subunits and alpha hCG (CGA) subunits are expressed and the hCG dimer is produced in normal human cyclic endometrium. Endometrial specimens were collected for histological dating from women undergoing treatment in our division of human reproduction. RNA from normal secretory endometrium was extracted, and CGB and CGA gene expression was assessed by semiquantitative PCR. Adequate secretory endometrial specimens were homogenized using protease inhibitors. Proteins present in the supernatant were separated electrophoretically, and molecular hCG isoforms were detected by Western blot. The supernatant hCG concentrations were measured by ELISA. We characterized hCG and leukocytes in endometrial specimens by immunohistochemistry. Uterine flushing was performed to confirm endometrial hCG secretion into the uterine fluid. A full-length CGB mRNA encompassing the exon 1 promoter region and the structure exons 2 and 3 (including the C-terminal peptide) was expressed in normal secretory endometrial specimens (similar to CGA) during the early secretory phase of the menstrual cycle, up to an optimum at the midsecretory to late secretory phases. In homogenate supernatants obtained from normal secretory endometrium, hormone concentrations of dimeric hCG were approximately 5 mU per 10 mg of tissue, compared with considerably smaller concentrations of corresponding single free CGB subunit. Single chains of CGB, CGA, and dimeric molecular hCG isoforms were found in endometrial specimens by Western blot. Glandular endometrial hCG production is demonstrated immunohistochemically, with an increase toward the late secretory phase vs. the early secretory phase of the normal secretory menstrual cycle. However, glandular hCG release is diminished or absent in the dyssynchronous or missing endometrial secretory transformation. Endogenous endometrial hCG may be important for implantation and maintenance of pregnancy.

Identification of differences in gene expression in primary cell cultures of human endometrial epithelial cells and trophoblast cells following their interaction

BACKGROUND

The interaction between epithelial cells of endometrium and trophoblast cells during implantation is presumed to be accompanied by a change in gene expression in the cell types involved. The objective of this study was to identify such differentially expressed genes.

METHODS

The interaction between the cell types was simulated in vitro by growing primary cell cultures of human endometrial epithelial cells and trophoblast cells together (co-culture) and separately (control cultures). Gene expression in the cell cultures was compared using the Differential Display method and confirmed using a modified Northern Blot method.

RESULTS

Twelve transcripts were identified as being differentially expressed following the interaction between trophoblast and endometrial cells. Some of these sequences show homology to known human genes while other sequences are coding for potential novel genes: (1) one sequence was homologous to the to Homer 1 gene, (2) one identical to the mRNA for XP-G factor, (3) one similar to a hypothetical protein, (4) transcripts showing homologies to a mRNA coding for a cellular proapoptotic protein, and (5) sequences homologous to regions on human chromosomes 5 and 16. Besides, some differentially expressed transcripts have sequences, which could be translated into ribosomal proteins or possibly code for novel proteins.

CONCLUSION

These sequences may be important to the course of events following the interaction between endometrial epithelial and trophoblast cells and responsible for implantation.

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.

Is there any evidence for immunologically mediated or immunologically modifiable early pregnancy failure?

PURPOSE

Human reproduction is an inefficient process. There is a high rate of loss of early pregnancies, often before the mother (or physician) knows she is pregnant. Genetic abnormalities can explain much of the wastage, but can it explain all of the failures? As embryos bear paternal and embryonic antigens foreign to the maternal immune system, could some otherwise normal embryos be "rejected"?

METHODS

Critical review of existing data.

RESULTS AND CONCLUSIONS

Otherwise normal embryos can fail prior to implantation, at implantation, in the periimplantation period as occult/chemical pregnancies, and as clinically evident miscarriages. The maternal immune system and its products (e.g., cytokines) can have innocent bystander effects, and a good case for direct recognition and "rejection" can also be made. The tools needed for accurate clinical diagnosis of such situations require further development and validation. Deliberate modification of the maternal host defence system can improve the chance of success, but the best evidence for efficacy of immunotherapeutic interventions is the situation of recurrent spontaneous abortions, which constitutes only a small percentage of losses. There is also evidence of clinical efficacy for several types of treatment to improve implantation and early pregnancy success.

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.

Early pregnancy losses in in vitro fertilization and oocyte donation

OBJECTIVE

To evaluate prospectively the incidence of early pregnancy losses (before menstruation occurs) in IVF and ovum donation cycles.

DESIGN

Prospective case-control study.

SETTING

Tertiary care, university-associated center.

PATIENT(S)

One hundred forty-five patients undergoing IVF and 92 undergoing oocyte donation were recruited. The control group for IVF consisted of 15 ovum donors who had no ET and were instructed to avoid intercourse. The control group for oocyte donation included 10 women undergoing a mock cycle of steroid replacement.

INTERVENTION(S)

Starting on day 6 after ET, the women were instructed to collect the first urine sample of the day every 2 days. Each patient collected six different specimens of urine (days 6, 8, 10, 12, 14, and 16 after ET for cases or the same days without ET for controls.

MAIN OUTCOME MEASURE(S)

beta-HCG was measured with a standardized microparticle enzyme immunoassay, and IVF reproductive outcome was assessed.

RESULT(S)

For IVF, positive implantation was registered in 88 of 145 cycles of embryo replacement (60.7%). Only 30 (20.7%) resulted in viable pregnancies, whereas the remaining 58 miscarried. Forty-two of these miscarriages (72.4%) were early pregnancy losses and 13 (22.4%) were classified as clinical abortions. In ovum donation, positive implantation was recorded in 64 of 92 cycles of ET (69.6%). A total of 30 (32.6%) ended in viable pregnancies, whereas the remaining 34 (37.0%) were miscarriages. Early pregnancy loss accounted for 70.6% of pregnancy losses, whereas biochemical pregnancies and clinical abortions accounted for 11.8% and 17.6%, respectively.

CONCLUSION(S)

Our results demonstrate that patients undergoing assisted reproductive technology have an increased rate of early pregnancy loss compared with fertile patients. In addition, these data indicate that implantation is more frequently impaired in IVF than in oocyte donation cycles, resulting in a high incidence of early pregnancy loss. This suggests that implantation may be subjected to abnormal conditions in assisted reproduction.

HCG secretion by peripheral mononuclear cells during pregnancy

Peripheral mononuclear cells (MNC) in culture release a biologically active hCG. This effect is detectable during pregnancy with a maximum between the 9th and 16th wk. Peripheral MNC already secrete hCG between the 7th and 11th d after embryo transfer. The secretion of hCG is activated by the PKC-activator TPA. TPA induces hCG release into the medium, thus causing a decrease in intracellular hCG content. In contrast, db-cAMP inhibites hCG secretion into the medium. Protein synthesis inhibitors of transcription and translation suppress the production and secretion of hCG. Peripheral natural killer (NK) cells (CD56+/CD16+) and monocytes (CD14+) show the highest secretion rates. IL-1 beta, IL-4, IL-6, IL-10, TNF alpha, and GM-CSF stimulate, whereas IL-2 and INF gamma inhibit, the hCG secretion of mononuclear cells. Flow cytometric experiments with hCG antibody demonstrate a binding of hCG on the surface of monocytes more than lymphocytes. The binding capacity is improved during pregnancy. Different hCG bands are shown in the Western blot analysis. We could confirm the mRNA of beta hCG and alpha CG are in MNC as well in the placental control. Peripheral MNC, first and foremost NK cells and monocytes, produce and secrete hCG during pregnancy, which play an important role for the corpus luteum rescue during the early gestational age and possibly for the immunotolerance.