Leptin Stimulates Endometriosis Development in Mouse Models

Endometriosis is a chronic inflammatory condition in women, and obesity leads to an inflammatory condition that is directly involved in the etiology of endometriosis. However, observational studies have shown an inverse correlation between endometriosis and a low body mass index (BMI). Obesity does not protect against endometriosis, and on the contrary, an increased BMI may lead to more severe forms of the disease. To determine the effect of obesity on endometriosis, diet-induced and genetically engineered obese mouse models were integrated with endometriosis mouse models with fluorescence-tagged ectopic lesions. High-fat diet-induced obese mice revealed a significant increase in endometriosis development compared with regular-diet control mice. However, obese recipient mice with leptin deficiency and leptin receptor deficiency showed suppressed endometriosis development compared with control mice. Furthermore, donor uterine tissues with leptin deficiency and leptin receptor deficiency suppressed endometriosis development compared with control donor in control recipient mice. Importantly, we revealed that aberrant high levels of leptin concentration significantly increased endometriosis development compared with vehicle treatment group in control mice with normal body weight. Our results suggest that leptin and its receptor are critical for endometriosis development.

Loss of MIG-6 results in endometrial progesterone resistance via ERBB2

Female subfertility is highly associated with endometriosis. Endometrial progesterone resistance is suggested as a crucial element in the development of endometrial diseases. We report that MIG-6 is downregulated in the endometrium of infertile women with endometriosis and in a non-human primate model of endometriosis. We find ERBB2 overexpression in the endometrium of uterine-specific Mig-6 knockout mice (Pgr^cre/+Mig-6^f/f; Mig-6^d/d). To investigate the effect of ERBB2 targeting on endometrial progesterone resistance, fertility, and endometriosis, we introduce Erbb2 ablation in Mig-6^d/d mice (Mig-6^d/dErbb2^d/d mice). The additional knockout of Erbb2 rescues all phenotypes seen in Mig-6^d/d mice. Transcriptomic analysis shows that genes differentially expressed in Mig-6^d/d mice revert to their normal expression in Mig-6^d/dErbb2^d/d mice. Together, our results demonstrate that ERBB2 overexpression in endometrium with MIG-6 deficiency causes endometrial progesterone resistance and a nonreceptive endometrium in endometriosis-related infertility, and ERBB2 targeting reverses these effects.

Female subfertility is highly associated with endometriosis. Here the authors show that progesterone-induced MIG-6 is reduced in endometrium of infertile women and non-human primates with endometriosis, and in a mouse model find that Erbb2 is the key mediator of Mig-6 loss induced endometriosis-related infertility.

Associations between Exposure to Organochlorine Chemicals and Endometriosis: A Systematic Review of Experimental Studies and Integration of Epidemiological Evidence

BACKGROUND

Growing epidemiological evidence suggests that organochlorine chemicals (OCCs), including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), may play a role in the pathogenesis of endometriosis.

OBJECTIVES

We aimed to systematically review the experimental evidence (in vivo and in vitro) on the associations between exposure to OCCs and endometriosis-related end points.

METHODS

A systematic review protocol was developed following the National Toxicology Program /Office of Health Assessment and Translation (NTP/OHAT) framework and managed within a web-based interface. In vivo studies designed to evaluate the impact of OCCs on the onset or progression of endometriosis and proliferation of induced endometriotic lesions were eligible. Eligible in vitro studies included single-cell and co-culture models to evaluate the proliferation, migration, and/or invasion of endometrial cells. We applied the search strings to PubMed, Web of Science, and Scopus®. A final search was performed on 24 June 2020. Assessment of risk of bias and the level of evidence and integration of preevaluated epidemiological evidence was conducted using NTP/OHAT framework Results: Out of 812 total studies, 39 met the predetermined eligibility criteria (15 in vivo, 23 in vitro, and 1 both). Most studies (n=27) tested TCDD and other dioxin-like chemicals. In vivo evidence supported TCDD's promotion of endometriosis onset and lesion growth. In vitro evidence supported TCDD's promotion of cell migration and invasion, but there was insufficient evidence for cell proliferation. In vitro evidence further supported the roles of the aryl hydrocarbon receptor and matrix metalloproteinases in mediating steroidogenic disruption and inflammatory responses. Estrogen interactions were found across studies and end points.

CONCLUSION

Based on the integration of a high level of animal evidence with a moderate level of epidemiological evidence, we concluded that TCDD was a known hazard for endometriosis in humans and the conclusion is supported by mechanistic in vitro evidence. Nonetheless, there is need for further research to fill in our gaps in understanding of the relationship between OCCs and their mixtures and endometriosis, beyond the prototypical TCDD. https://doi.org/10.1289/EHP8421.

Liver uptake of gold nanoparticles after intraperitoneal administration in vivo: a fluorescence study

Background

One particularly exciting field of research involves the use of gold nanoparticles (GNPs) in the detection and treatment of cancer cells in the liver. The detection and treatment of cancer is an area in which the light absorption and emission characteristics of GNPs have become useful. Currently, there are no data available regarding the fluorescence spectra or in vivo accumulation of nanoparticles (NPs) in rat liver after repeated administration. In an attempt to characterise the potential toxicity or hazards of GNPs in therapeutic or diagnostic use, the present study measured fluorescence spectra, bioaccumulation and toxic effects of GNPs at 3 and 7 days following intraperitoneal administration of a 50 μl/day dose of 10, 20 or 50 nm GNPs in rats.

Methods

The experimental rats were divided into one normal group (Ng) and six experimental groups (G1A, G1B, G2A, G2B, G3A and G3B; G1: 20 nm; G2: 10 nm; G3: 50 nm; A: infusion of GNPs for 3 days; B: infusion of GNPs for 7 days). A 50 μl dose of GNPs (0.1% Au by volume) was administered to the animals via intraperitoneal injection, and fluorescence measurements were used to identify the toxicity and tissue distribution of GNPs in vivo. Seventy healthy male Wistar-Kyoto rats were exposed to GNPs, and tissue distribution and toxicity were evaluated after 3 or 7 days of repeated exposure.

Results

After administration of 10 and 20 nm GNPs into the experimental rats, two fluorescence peaks were observed at 438 nm and 487 nm in the digested liver tissue. The fluorescence intensity for 10 and 20 nm GNPs (both first and second peaks) increased with the infusion time of GNPs in test rats compared to normal rats. The position of the first peak was similar for G1A, G2A, G1B, G2B, G3B and the normal (438 nm); that for G3A was shifted to a longer wavelength (444 nm) compared to the normal. The position of the second peak was similar for G1A, G1B, G2A, G2B and the control (487 nm), while it was shifted to a shorter wavelength for G3A (483 nm) and G3B (483 nm). The fluorescence intensity of the first and second peaks increased for G1A, G2A, G1B and G2B, while it decreased for G3A and G3B compared to the control.

Conclusions

The fluorescence intensity of GNPs varied with the number, size and shape of particles and with the ratio of surface area to volume in a given sample. Fluorescence intensity changes during infusion depended on the size and shape of GNPs, with smaller particles experiencing larger changes during the infusion time in addition to the quenching produced by the larger GNPs. It is likely that smaller particles, which have a much higher ratio of surface area to volume compared to larger particles, are more prone to aggregation and surface interaction with biological components. This study suggests that fluorescence intensity can be used to evaluate bioaccumulation and the toxicity of gold nanoparticles in rats.

Quantification of endometriotic lesions in a murine model by fluorimetric and morphometric analyses

BACKGROUND

In animal models of endometriosis, the identification and quantification of lesions originating from human endometrium is often hampered by the small size of the implants and their embedding in murine tissue. The purpose of the present study was to develop two new methods of quantifying endometriosis-like lesions in a nude mouse model: fluorimetry and morphometry.

METHODS

Human menstrual endometrium was labelled using a fluorescent tracker, carboxyfluorescein diacetate, succinimidyl ester (CFDA-SE), and transplanted into the pelvic cavity of mice by injection through the peritoneum after performing a cutaneous incision. After 5 days, lesions were recovered by laparotomy. The fluorescence of the recovered endometriotic lesions was measured. Endometrial stroma and glands were immunostained in lesion sections with anti-CD10 and anti-CK22 antibodies, and their surface area was evaluated by morphometric analysis.

RESULTS

Fluorescent labelling allows identification of lesions not visible macroscopically. A good correlation was observed between fluorimetry and morphometry (r=0.88) applied for lesion quantification.

CONCLUSIONS

Fluorimetric evaluation combined with morphometric analysis of endometriosis-like lesions allows objective and reliable recording of endometriosis development in a nude mouse model. This quantification method could therefore be useful for future pharmacological and toxicological studies.

Associations between serum levels of selected organochlorine compounds and endometriosis in infertile Japanese women

Endocrine-disrupting chemicals (EDCs) have been proposed as risk factors for endometriosis. Persistent organochlorine compounds, a group of suspected EDCs, are present to some extent in almost all human adipose tissue and blood via the food chain. A few animal studies have confirmed that exposure to these compounds can increase the incidence of endometriosis. In this study, we examined the associations between endometriosis and exposure to selected organochlorine compounds, including 8 polychlorinated dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs), 4 coplanar polychlorinated biphenyls (cPCBs), 36 ortho-substituted polychlorinated biphenyls (PCBs), and 13 chlorinated pesticides or their metabolites. The participants were 139 infertile Japanese women who were examined by laparoscopy and diagnosed as either endometriosis cases (Stages II-IV) or controls (Stages 0-I). The serum levels (lipid adjusted) of the targeted organochlorine compounds were in both 58 cases and 81 controls. There were very few differences in the various levels between endometriosis cases and controls. The total serum toxic equivalency (TEQ) value of PCDDs was significantly higher in the controls than in the cases (P=0.02). No other total TEQ values differed between cases and controls. For PCDDs, PCDFs, cPCBs, and PCBs, the multivariate odds ratio was 0.38 [95% confidence interval (CI), 0.12-1.17] and 0.41 (95% CI, 0.14-1.27) for the third and highest quartiles, respectively, compared to the lowest quartile of total TEQ values. A weak, negative dose-response relationship was evident for total TEQs (P for trend of 0.06). The results of this study provide some evidence that serum levels of these organochlorine compounds are not associated with an increased risk of endometriosis in infertile Japanese women.

Health effects classification and its role in the derivation of minimal risk levels: Reproductive and endocrine effects

The Agency for Toxic Substances and Disease Registry (ATSDR) derives health-based guidance values called minimal risk levels (MRLs) to assist with assessment of risks posed by exposures to hazardous chemicals. From the total of 326 MRLs currently posted on ATSDR's web site (www.atsdr.cdc.gov), 14 and 5 MRLs are based on reproductive and endocrine endpoints, respectively. The paper also describes the ranking of effects into less serious and serious categories according to ATSDR's Guidance for Developing Toxicological Profiles, endpoints used for the MRLs derivation, and the use of uncertainty factors.

Nonsteroidal antiinflammatory drugs differentially suppress endometriosis in a murine model

OBJECTIVE

To determine whether nonsteroidal antiinflammatory drugs (NSAIDs) affect the establishment and progression of endometriotic lesions in a murine model.

DESIGN

Pharmacologic intervention in a surgically induced murine model of abdominal/peritoneal endometriosis.

SETTING

Animal research facility.

PATIENT(S)

Eight-week-old, female C57BL/6 mice.

INTERVENTION(S)

After implantation of autologous endometrium, mice were randomized into groups and treated with one of several NSAIDs or the vehicle-matched control for 4 weeks.

MAIN OUTCOME MEASURE(S)

Establishment, growth, and total burden of endometriotic lesions.

RESULT(S)

The NSAIDs differentially inhibited lesion establishment and growth, resulting in significantly reduced disease burden. Compared with controls (5.7 +/- 2.3 mm(2)), lesion burden was reduced by celecoxib (1.3 +/- 1.2 mm(2)), indomethacin (1.4 +/- 1.4 mm(2)), naproxen (2.7 +/- 1.2 mm(2)), sulindac (3.1 +/- 1.5 mm(2)), rofecoxib (3.4 +/- 3.0 mm(2)), and ibuprofen (4.1 +/- 1.4 mm(2)). In contrast, aspirin (5.9 +/- 1.2 mm(2)) had no statistically significant effect. Uninterrupted estrus cycling was confirmed by vaginal exams and smears in celecoxib-treated mice.

CONCLUSION(S)

Chronic administration of certain NSAIDs limits the progression of endometriosis in this murine model. The data suggest that NSAID selection in the treatment of endometriosis should be extended beyond pain management to maximize the inhibitory effect on disease burden.

Histomorphometric alteration and cell-type specific modulation of arylhydrocarbon receptor and estrogen receptor expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin and 17β-estradiol in mouse experimental model of endometriosis

Our purpose was to examine the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), either singly (10 microg/kg) or with 17beta-estradiol (E2, 100 microg/kg), on the growth of endometriosis in a mouse endometriosis model by employing histo-morphometrical analysis as well as expression of arylhydrocarbon receptor (AhR) and estrogen receptor (ER). Epithelial height, stromal thickness, and proliferative activity of the endometriotic lesions were significantly increased by E2 in ovariectomized mice, whereas co-administered TCDD significantly reduced these effects. TCDD alone did not affect the proliferative activity but rather reduced the epithelial height and stromal thickness. ER expression in the luminal epithelium was decreased by E2 compared with ovariectomy alone, while TCDD significantly increased it. On the other hand, stromal ER expression was significantly increased by ovariectomy and decreased by E2, though TCDD did not further enhance this expression. These results indicate that a short-term exposure to TCDD failed to increase the growth of endometriotic lesion and the direct effect of TCDD probably depends on a cell-specific interaction with ovarian steroids mediated by their own receptors. These initial findings in intact tissue of mouse endometriosis may suggest critical roles of steroid hormones in the pathogenesis of endometriosis in relation to endocrine disruptors.

Tampons, dioxins, and endometriosis

Concern has been expressed that rayon tampons contain dioxins as a result of chlorine bleaching and, further, that the dioxins in tampons may increase the risk of endometriosis. Rayon tampons do not contain 2,3,7,8-tetrachlorodibenzo-p-dioxin, the chemical commonly meant when the generic term "dioxin" is used. In addition, rayon tampons contain only trivial amounts of dioxin-like environmental contaminants, similar to the amounts contained in unbleached cotton tampons. The amount of dioxin-like material that is theoretically available from tampons is at least six orders of magnitude lower than estimated daily food exposure levels to these contaminants. The evidence for a causal relationship between environmental exposure to dioxins and endometriosis is inconsistent. Prediction of the effective dioxin dose based on the most suggestive of the primate studies on endometriosis does not raise concerns about typical human food exposures to these compounds, let alone the considerably lower levels that could be present in tampons.

Children's environmental health risks: a state-of-the-art conference

More than 100 academic and private-sector researchers, government officials, politicians, and public health practitioners met to discuss issues regarding children's environmental health. Of special concern were the lack of toxicological data on many chemicals, the paucity of studies of children's exposure to these chemicals, and our limited understanding of pediatric toxicology. The increased incidence of childhood cancers and asthma were also of concern, as was our lack of understanding of how exposures to multiple environmental chemicals in low doses may influence child growth and development, disrupt endocrine function, and stimulate development of chronic diseases. An agenda for basic research, education and outreach, and policy and program development was created, with a goal of moving children's environmental health issues forward in a logical and thoughtful manner.