Decreased Progesterone Receptor B/A Ratio in Endometrial Cells by Tumor Necrosis Factor-Alpha and Peritoneal Fluid from Patients with Endometriosis

Aberrant epigenetic regulation of estrogen and progesterone signaling at the level of endometrial/endometriotic tissue in the pathomechanism of endometriosis

Endometriosis is a term referring to a condition whereby the endometrial tissue is found outside the uterine cavity. This progressive and debilitating condition affects up to 15% of women of reproductive age. Due to the fact that endometriosis cells may express estrogen receptors (ERα, Erβ, GPER) and progesterone (P4) receptors (PR-A, PR-B), their growth, cyclic proliferation, and breakdown are similar to the processes occurring in the endometrium. The underlying etiology and pathogenesis of endometriosis are still not fully explained. The retrograde transport of viable menstrual endometrial cells with the retained ability to attach within the pelvic cavity, proliferate, differentiate and invade into the surrounding tissue explains the most widely accepted implantation theory. Endometrial stromal cells (EnSCs) with clonogenic potential constitute the most abundant population of cells within endometrium that resemble the properties of mesenchymal stem cells (MSCs). Accordingly, formation of the endometriotic foci in endometriosis may be due to a kind of EnSCs dysfunction. Increasing evidence indicates the underestimated role of epigenetic mechanisms in the pathogenesis of endometriosis. Hormone-mediated epigenetic modifications of the genome in EnSCs or even MSCs were attributed an important role in the etiopathogenesis of endometriosis. The roles of excess estrogen exposure and P4 resistance were also found to be crucial in the development of epigenetic homeostasis failure. Therefore, the aim of this review was to consolidate the current knowledge regarding the epigenetic background of EnSCs and MSCs and the changed properties due to estrogen/P4 imbalances in the context of the etiopathogenesis of endometriosis.

Human V α 7.2-J α 33 mucosal-associated invariant T cells in endometrial ectopic tissues tend to produce interferon-gamma: A new player in endometriosis etiology: A case-control study

Background

Endometriosis is a chronic estrogen-related inflammatory disorder that is known by proliferating endometrial cells in a place outside the uterus. The high presence of immune cells in the peritoneal fluid of women with endometriosis confirms the involvement of the immune system in the pathogenesis of the disease. Mucosal-associated invariant T (MAIT) cells play an undeniable impact on mucosal immunity by the production of interleukin-17, interferon-gamma (IFN-γ), and tumor necrosis factor-alpha. The function of the cells in the pathogenesis of endometriosis is less investigated.

Objective

This study aims to investigate the infiltration of MAIT cells by using the determination levels of V α 7.2-J α 33 gene expression in eutopic and ectopic tissue of endometriosis lesions.

Materials and Methods

In this case-control study, the tested samples include 20 eutopic and 20 ectopic tissues of women with endometriosis and 20 uterine endometrial tissues of women in the control group. Expressions of the V α 7.2-J α 33 tumor necrosis factor-alpha, interleukin-17A, and IFN-γ genes were analyzed by quantitative reverse transcriptase-polymerase chain reaction.

Results

According to the results, V α 7.2-J α 33 gene expression did not show substantial elevation in the uterine and eutopic endometrial tissues compared to internal gene control as well as in ectopic tissues. Correlation analysis approved a positive relationship between V α 7.2-J α 33 expression genes and IFN-γ levels in ectopic tissues.

Conclusion

Considering the low-expression specific gene of MAIT cells in ectopic tissue, it can be concluded that these cells are present in the endometriotic environment to a certain extent, and there is a possibility of their role in the progression of endometriosis by secreting IFN- γ .

Regulation of progesterone receptor expression in endometriosis, endometrial cancer, and breast cancer by estrogen, polymorphisms, transcription factors, epigenetic alterations, and ubiquitin-proteasome system

The uterus and breasts are hormone-responsive tissues. Progesterone and estradiol regulate gonadotropin secretion, prepare the endometrium for implantation, maintain pregnancy, and regulate the differentiation of breast tissue. Dysregulation of these hormones causes endometriosis, endometrial cancer, and breast cancer, damaging the physical and mental health of women. Emerging evidence has shown that progesterone resistance or elevated progesterone activity is the primary hormonal substrate of these diseases. Since progesterone acts through its specific nuclear receptor, the abnormal expression of the progesterone receptor (PR) dysregulates progesterone function. This review discusses the regulatory mechanisms of PR expression in patients with endometriosis, and endometrial or breast cancer, including estrogen, polymorphisms, transcription factors, epigenetics, and the ubiquitin-proteasome system. (1) Estrogen promotes the expression of PRA (a PR isoform) mRNA and protein through the interaction of estrogen receptors (ERs) and Sp1 with half-ERE/Sp1 binding sites. ERs also affect the binding of Sp1 and Sp1 sites to promote the expression of PRB (another PR isoform)(2) PR polymorphisms, mainly PROGINS and + 331 G/A polymorphism, regulate PR expression by affecting DNA methylation and transcription factor binding. (3) The influence of epigenetic alterations on PR expression occurs through DNA methylation, histone modification, and microRNA. (4) As one of the main protein degradation pathways in vivo, the ubiquitin-proteasome system (UPS) regulates PR expression by participating in protein degradation. These mechanisms may provide new molecular targets for diagnosing and treating endometriosis, endometrial, and breast cancer.

MicroRNAs and Progesterone Receptor Signaling in Endometriosis Pathophysiology

Endometriosis is a significant disease characterized by infertility and pelvic pain in which endometrial stromal and glandular tissue grow in ectopic locations. Altered responsiveness to progesterone is a contributing factor to endometriosis pathophysiology, but the precise mechanisms are poorly understood. Progesterone resistance influences both the eutopic and ectopic (endometriotic lesion) endometrium. An inability of the eutopic endometrium to properly respond to progesterone is believed to contribute to the infertility associated with the disease, while an altered responsiveness of endometriotic lesion tissue may contribute to the survival of the ectopic tissue and associated symptoms. Women with endometriosis express altered levels of several endometrial progesterone target genes which may be due to the abnormal expression and/or function of progesterone receptors and/or chaperone proteins, as well as inflammation, genetics, and epigenetics. MiRNAs are a class of epigenetic modulators proposed to play a role in endometriosis pathophysiology, including the modulation of progesterone signaling. In this paper, we summarize the role of progesterone receptors and progesterone signaling in endometriosis pathophysiology, review miRNAs, which are over-expressed in endometriosis tissues and fluids, and follow this with a discussion on the potential regulation of key progesterone signaling components by these miRNAs, concluding with suggestions for future research endeavors in this area.

Peritoneal fluid progesterone and progesterone resistance in superficial endometriosis lesions

Peritoneal fluid in ovulatory women is an ovarian exudate with higher estrogen and progesterone concentrations than in plasma. In the follicular phase, progesterone concentrations are as high as plasma concentrations in the luteal phase. After ovulation, estrogen and progesterone concentrations in the peritoneal fluid are 5-10 times higher than in plasma, both in women with and without endometriosis. The histologically proliferative aspect without secretory changes of most superficial subtle lesions is not compatible with the progesterone concentrations in the peritoneal fluid. Therefore, we have to postulate a strong progesterone resistance in these lesions. The mechanism is unclear and might be a peritoneal fluid effect in women with predisposing defects in the endometrium, or isolated endometrial glands with progesterone resistance, or subtle lesions originating from the basal endometrium: the latter hypothesis is attractive since in basal endometrium progesterone does not induce secretory changes while progesterone withdrawal, not occurring in peritoneal fluid, is required to resume mitotic activity and proliferation. Hormone concentrations in the peritoneal fluid are an important factor in understanding the medical therapy of endometriosis. The effect of oestro-progestin therapy on superficial endometriosis lesions seems to be a consequence of the decreased estrogen concentrations rather than a direct progestin effect. In conclusion, the peritoneal fluid, being a secretion product of the ovarian follicule, deserves more attention in the pathophysiology and treatment of endometriosis.

Estrogen- and Progesterone (P4)-Mediated Epigenetic Modifications of Endometrial Stromal Cells (EnSCs) and/or Mesenchymal Stem/Stromal Cells (MSCs) in the Etiopathogenesis of Endometriosis

Endometriosis is a common chronic inflammatory condition in which endometrial tissue appears outside the uterine cavity. Because ectopic endometriosis cells express both estrogen and progesterone (P4) receptors, they grow and undergo cyclic proliferation and breakdown similar to the endometrium. This debilitating gynecological disease affects up to 15% of reproductive aged women. Despite many years of research, the etiopathogenesis of endometrial lesions remains unclear. Retrograde transport of the viable menstrual endometrial cells with retained ability for attachment within the pelvic cavity, proliferation, differentiation and subsequent invasion into the surrounding tissue constitutes the rationale for widely accepted implantation theory. Accordingly, the most abundant cells in the endometrium are endometrial stromal cells (EnSCs). These cells constitute a particular population with clonogenic activity that resembles properties of mesenchymal stem/stromal cells (MSCs). Thus, a significant role of stem cell-based dysfunction in formation of the initial endometrial lesions is suspected. There is increasing evidence that the role of epigenetic mechanisms and processes in endometriosis have been underestimated. The importance of excess estrogen exposure and P4 resistance in epigenetic homeostasis failure in the endometrial/endometriotic tissue are crucial. Epigenetic alterations regarding transcription factors of estrogen and P4 signaling pathways in MSCs are robust in endometriotic tissue. Thus, perspectives for the future may include MSCs and EnSCs as the targets of epigenetic therapies in the prevention and treatment of endometriosis. Here, we reviewed the current known changes in the epigenetic background of EnSCs and MSCs due to estrogen/P4 imbalances in the context of etiopathogenesis of endometriosis. Graphical Abstract.

THE EFFECTS OF ETANERCEPT AND CABERGOLINE ON ENDOMETRIOTIC IMPLANTS, UTERUS AND OVARIES IN RAT ENDOMETRIOSIS MODEL

The pathophysiology of endometriosis is still unknown and treatment options remain controversial. Searches focus on angiogenesis, stem cells, immunologic and inflammatory factors. This study investigated the effects of etanercept and cabergoline on ovaries, ectopic, and eutopic endometrium in an endometriosis rat model. This randomized, placebo-controlled, blinded study included 50 rats, Co(control), Sh(Sham), Cb(cabergoline), E(etanercept), and E + Cb(etanercept + cabergoline) groups. After surgical induction of endometriosis, 2^nd operation was performed for endometriotic volume and AMH level. After 15 days of treatment: AMH level, flow cytometry, implant volume, histologic scores, immunohistochemical staining of ectopic, eutopic endometrium, and ovary were evaluated at 3^rd operation. All groups had significantly reduced volume, TNF-α, VEGF, and CD 146/PDGF-Rβ staining of endometriotic implants comparing to the Sh group (p < 0.05).TNF-α staining of eutopic endometrium in all treatment groups was similar to Sh and Co groups (p > 0.05). E and E + Cb groups significantly decreased TNF-α staining in the ovary comparing to Sh, Co, and Cb groups (p < 0.05). All treatment groups had significantly higher AFC compared to the Sh group. CD25⁺ Cells' median percentage was significantly increased in the E + Cb group compared to Co, Sh, Cb, and E group. E + Cb group had a significantly higher CD5⁺ Cells' level than the Co group (p = 0.035). In conclusion; Etanercept and/or Cabergoline decreased volume, TNF-α, VEGF, and CD 146/PDGF-Rβ staining of the ectopic endometrial implant. E and E + Cb treatment decreased TNF-α levels in the ovary. E + Cb also increased peripheral blood CD25⁺ & CD5⁺ Cell's.

Insights into molecular pathways of endometriosis and endometriosis-related ovarian carcinoma

Background: Endometriosis is a benign estrogen-dependent gynecological disease involving components of the female genital tract (uterus, Fallopian tubes, ovaries, large, round, and utero-sacral ligaments) and intra- and extraperitoneal regions. Since the moment of its etiopathogeny has been identified, the intrinsic capacity of endometriosis malignant transformation has been hypothesized. Patients,Materials and Methods: Our study included a total number of 50 patients diagnosed with endometriosis (31 cases) and endometriosis-related ovarian carcinoma (EOC) (19 cases). A clinicopathological and immunohistochemical study directed towards the detection of atypical transition lesions and the similitudes in epithelial–mesenchymal transition (EMT) phenomenon [E-cadherin/β-catenin/cytokeratin 18 (CK18)], apoptosis [B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X (Bax)], and hormonal dynamics mirrored by the immunoexpression of estrogen receptor (ER) and progesterone receptor (PR) in endometriosis and EOC glands and stroma has been performed. Results: Our study showed a higher immunoexpression of CK18 and E-cadherin in endometriosis than in neoplastic counterparts, while β-catenin had a stronger immunoexpression in tumors compared with endometriotic areas, with statistically significant differences between the studied groups. Bcl-2/Bax higher rate in endometriosis had a statistically significant association to a more aggressive tumor behavior (p=0.020). ER immunoexpression was stronger in endometriosis, with less negative scores compared to EOC, while PR immunoexpression was stronger in endometriosis, with a lower percent of negative scores compared to EOC. PR immunostaining was correlated to ovarian location of endometriosis (p=0.004) and tumor grade of EOC (p=0.027). Stromal ER and PR immunoexpression has been significantly lower in endometriosis in comparison to tumor stroma (p=0.001) and PR stromal immunoexpression had been higher in more differentiated tumors compared to less differentiated types (p=0.005). Conclusions: Our study supports that endometriosis is a precursor of EOC by the identification and the coexistence of both lesions in the investigated cases, the identification of intermediate lesions, as well as the expression of EMT immunomarkers, along with apoptosis and steroid receptors immunoexpression.

Peritoneal lavage cytology in the diagnosis of pelvic endometriosis

BACKGROUND

We aimed to assess the sensibility, specificity, and predictive values of cytology of the fluid sediment in patients with pelvic endometriosis diagnosed based on laparoscopic-guided biopsy.

METHODS

Between January 2017 and September 2018, 71 specimens of peritoneal fluid collected by laparoscopy were evaluated. Fifty-three patients were diagnosed laparoscopically and histologically with endometriosis, and 18 were considered controls (without suspicious endometriosis lesions). We calculated the sensitivity, specificity, the positive and negative predictive value, and the accuracy of endometrial-like cells (ELC) and hemosiderin-laden macrophages (HLM) in the fluid sediment.

RESULTS

Of the 50 patients with endometriosis, 32 (64%) had HLM, 9 (18%) had ELC, and 7 (14%) had both elements. Of the 18 patients without endometriosis, 3 (16%) had HLM, 2 (11%) had ELC, and 1 (5%) had both ELC and HLM. The sensitivity of the cytology of peritoneal fluid sediment for the diagnosis of endometriosis, based on the presence of ELC, was 18%, the specificity was 83%, the positive predictive value was 82%, the negative predictive value was 28.7%, and the accuracy was 36.8%. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy based on the presence of HLM were 64%, 83%, 91%, 45.5%, and 69.1%, respectively.

CONCLUSION

The study of peritoneal fluids obtained laparoscopically from women undergoing evaluation for endometriosis may identify patients with the disease.

Differential regulation of osteopontin and CD44 correlates with infertility status in PCOS patients

Endometrial receptivity is mediated by adhesion molecules at the endometrium-trophoblast interface where osteopontin (OPN) and CD44 form a protein complex that plays an important role in embryo recognition. Here, we undertook a prospective study investigating the expression and regulation of OPN and CD44 in 50 fertile and 31 infertile ovulatory polycystic ovarian syndrome (PCOS) patients in the proliferative and secretory phases of the natural menstrual cycle and in 12 infertile anovulatory PCOS patients. Endometrial biopsies and blood samples were evaluated for expression of OPN and CD44 using RT-PCR, immunohistochemistry and ELISA analysis to determine circulating levels of OPN, CD44, TNF-α, IFN-γ and OPN and CD44 levels in biopsy media. Our findings highlighted an increased level of circulating OPN and CD44 in serum from infertile patients that inversely correlated with expression levels in endometrial tissue and positively correlated with levels secreted into biopsy media. OPN and CD44 levels positively correlated to each other in serum and media from fertile and PCOS patients, as well as to circulating TNF-α and IFN-γ. In vitro analysis revealed that hormone treatment induced recruitment of ERα to the OPN and CD44 promoters with a concomitant increase in the expression of these genes. In infertile patients, inflammatory cytokines led to recruitment of NF-κB and STAT1 proteins to the OPN and CD44 promoters, resulting in their overexpression. These observations suggest that the endometrial epithelial OPN-CD44 adhesion complex is deficient in ovulatory PCOS patients and displays an altered stoichiometry in anovulatory patients, which in both cases may perturb apposition. This, together with elevated circulating and local secreted levels of these proteins, may hinder endometrium-trophoblast interactions by saturating OPN and CD44 receptors on the surface of the blastocyst, thereby contributing to the infertility associated with ovulating PCOS patients. KEY MESSAGES: • Endometrial epithelial OPN-CD44 adhesion complex levels are deficient in ovulatory PCOS patients contributing to the endometrial infertility associated with ovulating PCOS patients. • Circulating levels of OPN, CD44 and inflammatory cytokines TNF-α and IFN-γ are altered in infertile PCOS patients. • Increased levels of both OPN and CD44 in biopsy media and serum inversely correlate with endometrial expression of these markers in endometrial tissue. • In infertile PCOS patients, high levels of oestrogens and inflammatory cytokines stimulate the recruitment of transcription factors to the OPN and CD44 promoters to enhance gene transcription. • Our study identifies a novel crosstalk between the CD44-OPN adhesion complex, ERα, STAT1 and NF-κB pathways modulating endometrial receptivity.

Relaxin-2 May Suppress Endometriosis by Reducing Fibrosis, Scar Formation, and Inflammation

Background: Relaxin (RLX)-2, produced by the corpus luteum and placenta, is known to be potentially effective in fibrotic diseases of the heart, lungs, kidneys, and bladder; however, its effectiveness in endometriosis has not yet been investigated. In the present study, we conducted a comprehensive study on the effect of RLX-2 on endometriosis. We checked the expressions of LGR-7, a primary receptor of RLX-2, in endometriomas using immunohistochemistry. Endometriotic stromal cells (ESCs) purified from surgical specimens were used in in vitro experiments. The effects of RLX-2 on ESCs were evaluated by quantitative-PCR, ELISA, and Western blotting. Gel contraction assay was used to assess the contraction suppressive effect of RLX-2. The effect of RLX-2 was also examined in the endometriosis mouse model. LGR-7 was expressed in endometriotic lesions. In ESCs, RLX-2 increased the production of cAMP and suppressed the secretion of interleukin-8, an inflammatory cytokine, by 15% and mRNA expression of fibrosis-related molecules, plasminogen activator inhibitor-1 (PAI-1), and collagen-I by approximately 50% (p < 0.05). In the gel contraction assay, RLX-2 significantly suppressed the contraction of ESCs, which was cancelled by removing RLX-2 from the medium or by adding H89, a Protein Kinase A (PKA) inhibitor. In ESCs stimulated with RLX-2, p38 MAPK phosphorylation was significantly suppressed. In the endometriosis mouse model, administration of RLX-2 significantly decreased the area of the endometriotic-like lesion with decreasing fibrotic component compared to non-treated control (p = 0.01). RLX-2 may contribute to the control of endometriotic lesion by suppressing fibrosis, scar formation, and inflammation.

Obstetrical complications and outcome in patients with endometriosis

Endometriosis is a disease that has a profound impact on the quality of life of women, due to the associated chronic pelvic pain, dysmenorrhea, dyspareunia and infertility. However, even getting long-awaited pregnancy (often after assisted reproductive technologies), patients with endometriosis have a high risk of obstetric complications, such as miscarriage, preterm birth, preeclampsia, placental abnormalities, hemorrhage in labor, birth of small for gestational age infants, stillbirth and higher cesarean section rate. In addition, during pregnancy acute complications of endometriosis may occur, such as spontaneous hemoperitoneum, which is rare but life-threatening conditions that in most cases require surgical intervention. The mechanisms of the observed complications in pregnant women with endometriosis are not fully understood. This review presents literature data and personal considerations on the effect of endometriosis on pregnancy outcome and the occurrence of complications, as well as their possible underlined mechanisms. Based on this, we proposed ways to reduce the risk of obstetric complications in pregnant women with a history of endometriosis.

New therapeutic approaches for endometriosis besides hormonal therapy

Supplemental Digital Content is available in the text

Objective:

Endometriosis is a common gynecologic disease that frequently leading to chronic pelvic pain, severe dysmenorrhea, and subfertility. As first-line hormonal treatment can interfere with ovulation and may cause recurrent pelvic pain, exploration of new non-hormonal therapeutic approaches becomes increasingly necessary. This review aimed to evaluate the pre-clinical and clinical efficacy and safety of non-hormonal treatment for endometriosis

Data sources:

Databases including PubMed, Embase, Cochrane Library, SINOMED, ClinicalTrials.gov, and Google Scholar were searched up to October 2019, using search terms “endometriosis” and “non-hormonal therapy.”

Study selection:

Twenty-four articles were reviewed for analysis, including nine animal studies and 15 human trials; all were published in English.

Results:

Twenty-four articles were identified, including 15 human trials with 861 patients and nine animal studies. Some agents have been evaluated clinically with significant efficacy in endometriosis-related pelvic pain and subfertility, such as rofecoxib, etanercept, pentoxifylline, N-palmitoylethanolamine, resveratrol, everolimus, cabergoline (Cb2), and simvastatin. Other drugs with similar pharmacological properties, like parecoxib, celecoxib, endostatin, rapamycin, quinagolide, and atorvastatin, have only been tested in animal studies.

Conclusions:

Clinical data about most of the non-hormonal agents are not sufficient to support them as options for replacement therapy for endometriosis. In spite of this, a few drugs like pentoxifylline showed strong potential for real clinical application.

Women with Endometriosis, Especially Those Who Conceived with Assisted Reproductive Technology, Have Increased Risk of Placenta Previa: Meta-analyses

BACKGROUND

Many women with endometriosis have become pregnant through assisted reproductive technology (ART), and have often experienced placenta previa (PP) during pregnancy. The objective of this study was to assess the association between women with endometriosis, especially those who conceived with ART, and the risk of PP.

METHODS

Two reviewers independently determined studies that were considered suitable for meta-analyses published in various medicine-related databases from March 1, 2004 through July 31, 2017 without language restrictions. Eight studies met the inclusion criteria, with a combined sample size of 21,930 women. Of these 21,930 pregnancies, 6,256 had endometriosis (endometriosis) and 15,674 had no endometriosis. Four of these studies included 8,161 women who conceived with ART, 1,640 of whom had endometriosis (endometriosis + ART), and 6,521 of whom did not have endometriosis. Meta-analyses were estimated with odds ratios (ORs) and 95% confidence intervals (CIs) using random effect analysis according to heterogeneity of studies.

RESULTS

These meta-analyses showed women with endometriosis (endometriosis) have an increased risk of PP (OR, 4.038; 95% CI, 2.291-7.116; P = 0.000). These results showed women who conceived with ART (endometriosis + ART), have a substantially increased risk of PP (OR, 5.543; 95% CI, 1.659-18.523; P = 0.005).

CONCLUSION

These meta-analyses demonstrate women with endometriosis have an increased risk of PP.

Effect of Etanercept on the Success of Assisted Reproductive Technology in Patients with Endometrioma

AIMS

To determine the effects of a tumor necrosis factor inhibitor (etanercept) on pregnancy outcomes in patients with endometrioma who were treated with assisted reproductive technology.

METHODS

Sixty-eight infertile patients who had endometrioma were included in our retrospective case-control study. We administered etanercept (Enbrel, 50 mg in 1 mL intramuscularly) to 19 patients on the second day of their previous menstrual cycle. All patients were treated with assisted reproductive technology. Pregnancy and live birth rates (LBR) were documented.

RESULTS

When all other parameters (age, body mass index, infertility) are supposed to be constant, the clinical pregnancy rate was significantly higher in patients who used etanercept in an antagonist protocol than in patients who did not use etanercept (χ2 = 5.547; p = 0.019) but LBR did not reach a statistical significance (χ2 = 3.179; p = 0.075). The use of etanercept had an OR of 4.17 (95% CI 1.23-14.14) compared with not using etanercept for clinical pregnancy rate. The use of etanercept increased the rate of pregnancy (χ2 = 6.55; p = 0.01). The pregnancy rate with the use of etanercept had an OR of 4.23 (95% CI 1.35-13.25) compared with patients who did not use etanercept. In the same way, the use of etanercept increased LBR twofold, but it is not significant in the border line (χ2 = 3.771; p = 0.052).

CONCLUSIONS

Etanercept may be a new non-hormonal therapy that may be an adjunct to treatment of infertile women with endometrioma. However, the safety of etanercept on embryos and fetuses has not been fully clarified.