Experimental endometriosis in the rat is correlated with colonic motor function alterations but not with bacterial load

Voluntary Wheel Running Reduces Vesicle Development in an Endometriosis Animal Model Through Modulation of Immune Parameters

Introduction

Endometriosis is a chronic gynecological disorder characterized by the growth of endometrial glands and stroma outside the endometrial cavity producing inflammation and pain. Previously we demonstrated that modulation of the hypothalamic pituitary adrenal (HPA) axis exacerbates the development and severity of this condition. A physically active lifestyle has been shown to confer health benefits in many chronic conditions by potentially acting as a stress buffer, thus we hypothesized that voluntary physical exercise can “realign/reset” the HPA axis resulting in reduced endometriosis symptoms in an animal model.

Methods

Endometriosis was induced in female Sprague Dawley rats by implanting uterine tissue next to the intestinal mesentery on day 0. Sham controls received sutures only. One group of endometriosis animals had access to a running wheel for 2 weeks prior to endometriosis induction until time of sacrifice at day 60. Sham and endometriosis controls received no exercise. All animals were examined for developed vesicles which were collected and measured. Uterine tissue was analyzed for cellular infiltration. Brain, liver, spleen, adrenal glands, leg muscles, and fat were collected, along with peritoneal fluid and blood.

Results

Endometriosis animals developed vesicles in 86.96% of the implants with significantly increased mesenteric fat compared to sham (p < 0.05). Exposure to exercise significantly decreased the size (p < 0.01) and number (p < 0.05) of vesicles that developed, as well as the mesenteric fat (p < 0.01). Exercised animals had higher levels of lactoferrin in peritoneal fluid, and decreased serum fractalkine and leptin. Exercise significantly increased estrogen alpha receptor expression levels (p < 0.01), while significantly decreasing estrogen receptor beta expression (p < 0.01) and macrophage infiltration (p < 0.05) in vesicles compared to non- exercised animals.

Conclusions

Our results suggest that voluntary physical activity might protect against endometriosis and alleviate the associated inflammation via immune modulation of the HPA axis. This offers the potential for further exploration of exercise as a complementary therapy in endometriosis patients.

Inhibition of Histone Methyltransferase EZH2 Suppresses Endometriotic Vesicle Development in a Rat Model of Endometriosis

Endometriosis is a painful gynecological disease with no cure and limited therapeutic options. It has been hypothesized that epigenetic drugs can be used as a nonhormonal treatment for endometriosis. This study was conducted to study the efficacy of an inhibitor of the histone methyltransferase EZH2 using an established rat model of endometriosis. We hypothesized that treatment will block or reduce the number of endometriotic vesicles in this model. We conducted a preclinical drug study in female rats with experimental endometriosis (uterine tissue transplanted next to the intestinal mesentery) or control sham (sutures only). Rats with endometriosis or sham surgery received either treatment with EZH2 inhibitor (5 mg/kg or 10 mg/kg) or vehicle (0.1%, 67% DMSO) every other day during 4 weeks. After treatment completion, the number, area, volume, and weight of vesicles were evaluated. RT [2] Profiler Arrays for neuropathic and inflammation, epithelial to mesenchymal transition, inflammatory response, and autoimmunity pathways were used to examine gene expression changes in the vesicles that developed. Treatment with EZH2 inhibitor (10 mg/kg) suppressed the development of vesicles, by significantly decreasing the total vesicle number, area, volume, and weight. In addition, EZH2 inhibition significantly increased the expression of CACNA1B and FKBP1A genes, involved in pain and proliferation, respectively. EZH2 inhibition suppresses the growth of vesicles without apparent detrimental effects to other organs. Treatment with this epigenetic inhibitor leads to upregulation of a limited number of genes related to endometriosis-relevant pathways. In conclusion, these data support follow-up studies to evaluate its potential as a therapeutic approach for endometriosis.

Stress During Development of Experimental Endometriosis Influences Nerve Growth and Disease Progression

PURPOSE

We have previously shown that stress prior to induction worsens clinical presentation and inflammatory parameters in a rat model of endometriosis. This study was designed to examine whether stress during the development of endometriosis can affect the growth of endometriotic implants through nerve growth and immune alterations.

METHODS

Endometriosis was surgically induced in female Sprague-Dawley rats by suturing uterine horn implants onto the small intestine mesentery. Two weeks later, one group of rats (endo-stress) was subjected to a 10-day swim stress protocol. Controls had no stress (endo-no stress) or sutures only and stress (sham-stress). On day 60, all rats were killed and examined for the presence of endometriotic vesicles. The size of each vesicle was measured. The uterus and colon were removed and assessed for damage, cell infiltration, and expression of nerve growth factor (NGF), its receptors (p75 and Tropomyosin receptor kinase A (Trk-A)/pTrk-A), and calcitonin gene-related peptide, a sensory fiber marker. A differential analysis of peritoneal fluid white blood cell count was performed.

RESULTS

Stress significantly increased endometriotic vesicle size but not colonic damage and increased infiltration of mast cells. Significantly increased expression of NGF and its receptors was found in the uterus of animals with endometriosis receiving stress.

CONCLUSIONS

Stress stimulates the development of ectopic endometrial vesicles in an animal model of endometriosis and increases inflammatory cell recruitment to the peritoneum. In addition, stress promotes nerve fiber growth in the uterus.

Impact of Psychological Stress on Pain Perception in an Animal Model of Endometriosis

PURPOSE

Pain in patients with endometriosis is considered a significant source of stress but does not always correlate with severity of the condition. We have demonstrated that stress can worsen endometriosis in an animal model. Here, we tested the impact of a psychological stress protocol on pain thresholds and pain receptors.

METHODS

Endometriosis was induced in female rats by suturing uterine horn tissue next to the intestinal mesentery. Sham rats had sutures only. Rats were exposed to water avoidance stress for 7 consecutive days or handled for 5 minutes (no stress). Fecal pellets and serum corticosterone (CORT) levels were measured as an index of anxiety. Pain perception was assessed using hot plate and Von Frey tests. Substance P, enkephalin, endomorphin-2, Mu opioid receptor (MOR), and neurokinin-1 receptor expression in the spinal cord were measured by immunohistochemistry.

RESULTS

Fecal pellets and CORT were significantly higher in the endo-stress (ES) group than endo-no stress (ENS; P < .01) and sham-no stress groups (SNS; P < .01). The ES rats had more colonic damage ( P < .001 vs SNS; P < .05 vs ENS), vesicle mast cell infiltration ( P < .01 vs ENS), and more severe vesicles than ENS. The ES developed significant hyperalgesia ( P < .05) but stress reversed the allodynic effect caused by endo ( P < .001). The MOR expression was significantly reduced in ENS versus SNS ( P < .05) and more enkephalin expression was found in endo groups.

CONCLUSION

Animals subjected to stress develop more severe symptoms but interestingly stress seems to have beneficial effects on abdominal allodynia, which could be a consequence of the stress-induced analgesia phenomenon.

Endometriosis Is Associated With a Shift in MU Opioid and NMDA Receptor Expression in the Brain Periaqueductal Gray

Studies have examined how endometriosis interacts with the nervous system, but little attention has been paid to opioidergic systems, which are relevant to pain signaling. We used the autotransplantation rat model of endometriosis and allowed to progress for 60 days. The brain was collected and examined for changes in endogenous opioid peptides, mu opioid receptors (MORs), and the N-methyl-d-aspartate subunit receptor (NR1) in the periaqueductal gray (PAG), since both of these receptors can regulate PAG activity. No changes in endogenous opioid peptides in met- and leu-enkephalin or β-endorphin levels were observed within the PAG. However, MOR immunoreactivity was significantly decreased in the ventral PAG in the endometriosis group. Endometriosis reduced by 20% the number of neuronal profiles expressing MOR and reduced by 40% the NR1 profiles. Our results suggest that endometriosis is associated with subtle variations in opioidergic and glutamatergic activity within the PAG, which may have implications for pain processing.

Telocytes in Inflammatory Gynaecologic Diseases and Infertility

Women suffered with inflammatory gynecologic diseases, such as endometriosis (EMs) and acute salpingitis (AS) often complained of sub- or infertility, even in those women without obvious macroscopic anatomical pelvic abnormalities also have unexplained infertility. Generally, besides the well-known impairment of classically described oviduct cells caused by inflammatory diseases, such as the ciliated cells, fibroblasts and myofibroblasts, the involvement of the newly identified telocytes (TCs) in disease-affected oviduct tissues and potential pathophysiological roles in fertility problems remain unknown. In this chapter, TCs was investigated in rat model of EMs- and AS-affected oviduct tissues. Results showed inflammation and ischaemia-induced extensive ultrastructural damages of TCs both in cellular body and prolongations, with obvious TCs loss and interstitial fibrotic remodelling. Such in vivo pathological alterations might contribute to structural and functional abnormalities of oviduct tissue and potentially engaged in sub- or infertility. And especially, TCs connected to various activated immunocytes in both normal and diseased tissues, thus might participate in local immunoregulation (either repression or activation) and serve a possible explanation for immune-mediated pregnancy failure. Then, in vitro cell co-culture study showed that uterine TC conditioned media (TCM) can activate mouse peritoneal macrophages and subsequently trigger its cytokine secretion, thus providepreliminary evidence that, TCs are not simply innocent bystanders, but are instead potential functional players in local immunoregulatory and immunosurveillance.

Impact of physical activity on pain perception in an animal model of endometriosis

BACKGROUND

Symptoms of endometriosis, such as pain and infertility, are considered significant sources of stress. In many chronic conditions, exercise can act as a stress buffer and influence pain perception. We tested the impact of swimming exercise on pain perception and pain receptors in an animal model of endometriosis.

METHODS

Endometriosis (Endo) was induced in female rats by suturing uterine horn tissue next to the intestinal mesentery. Sham rats received sutures only. Rats were exposed to swimming exercise for 7 consecutive days, while no-exercise rats were left in the home cage. Fecal pellets were counted after swimming as an index of anxiety, and serum corticosterone levels measured. Pain perception was assessed using the hot plate test for hyperalgesia and Von Frey test for allodynia. Mu-opioid receptor (MOR) and neurokinin-1 receptor expression in the spinal cord was measured by immunofluorescence.

RESULTS

Fecal pellet counts were higher in those animals that swam (p<0.05), but no significant difference in corticosterone was found. Although Endo-exercise rats had higher colonic damage (p<0.05) with more cellular infiltration, the lesions were smaller than in Endo-no exercise rats (p<0.05). Exercise did not ameliorate the hyperalgesia, whereas it improved allodynia in both groups. MOR expression was significantly higher in Endo-exercise vs. Endo-no exercise rats (p<0.01), similar to Sham-no exercise levels.

CONCLUSIONS

Our results point toward beneficial effects of swimming exercise during endometriosis progression. Physical interventions might be investigated further for their ability to reduce perceived stress and improve outcomes in endometriosis.

Stress management affects outcomes in the pathophysiology of an endometriosis model

We have previously shown detrimental effects of stress in an animal model of endometriosis. We now investigated whether the ability to control stress can affect disease parameters. Endometriosis was surgically induced in female Sprague-Dawley rats before exposing animals to a controllable (submerged platform) or uncontrollable (no platform) swim stress protocol. Corticosterone levels and fecal pellet numbers were measured as an indicator of stress. Uncontrollable stress increased the number and size of the endometriotic cysts. Rats receiving uncontrollable stress had higher anxiety than those exposed to controllable stress or no stress and higher corticosterone levels. Uncontrollable stressed rats had more colonic damage and uterine cell infiltration compared to no stress, while controllable stress rats showed less of an effect. Uncontrollable stress also increased both colonic and uterine motility. In summary, the level of stress controllability appears to modulate the behavior and pathophysiology of endometriosis and offers evidence for evaluating therapeutic interventions.

Telocytes damage in endometriosis-affected rat oviduct and potential impact on fertility

Women with endometriosis (EMs) have unexplained infertility. The recently identified telocytes (TCs) might participate in the maintenance of structural and functional integrity of oviduct tissue, but so far the involvement of TCs in EMs-affected oviduct tissue and potential impact on fertility capacity remain unknown. By an integrated technique of haematoxylin and eosin staining, in situ immunohistochemistry and double-labelled immunofluorescence staining and electron microscopy approach, TCs were studied in the autotransplantation Sprague-Dawley rat model of EMs-affected oviduct tissue and in sham control, respectively, together with determination of iNOS, COX-2, LPO and estradiol. TCs were found in perivascular connective tissue and smooth muscle bundles in sham oviduct, with typical ultrastructural features (a slender piriform/spindle/triangular cell body, and one or more extremely long prolongations, emerged from cell bodies and extend to various directions), and specific immunophenotype of CD34-positive/vimentin-positive/c-kit-negative. However, in EMs-affected oviduct tissue (grade III), extensive ultrastructural damage (degeneration, discontinue, dissolution and destruction), significant decrease or loss of TCs and interstitial fibrosis were observed, together with elevated level of iNOS, COX-2, LPO and estradiol, thus suggestive of inflammation and ischaemia-induced TCs damage. Based on TCs distribution and intercellular connections, we proposed that such damage might be involved in structural and functional abnormalities of oviduct, such as attenuated intercellular signalling and oviduct contractility, impaired immunoregulation and stem cell-mediated tissue repair, 3-D interstitial architectural derangement and tissue fibrosis. Therefore, TCs damage might provide a new explanation and potential target for EMs-induced tubal damage and fertility disorders.

Stress exacerbates endometriosis manifestations and inflammatory parameters in an animal model

Women with endometriosis have significant emotional distress; however, the contribution of stress to the pathophysiology of this disease is unclear. We used a rat model of endometriosis to examine the effects of stress on the development of this condition and its influence on inflammatory parameters. Female Sprague-Dawley rats were subjected to swim stress for 10 consecutive days prior to the surgical induction of endometriosis by suturing uterine horn implants next to the intestinal mesentery (endo-stress). Sham-stress animals had sutures only, and an endo-no stress group was not subjected to the stress protocol. At the time of sacrifice on day 60, endometriotic vesicles were measured and colons assessed for macroscopic and microscopic damage. Colonic tissue and peritoneal fluid were collected for inflammatory cell analysis. Endometriosis, regardless of stress, produced a decrease in central corticotropin-releasing factor immunoreactivity, specifically in the CA3 subregion of the hippocampus. Prior exposure to stress increased both the number and severity of vesicles found in animals with endometriosis. Stress also increased colonic inflammation, motility, myeloperoxidase levels, and numbers of mast cells. In summary, prior stress may contribute to the development and severity of endometriosis in this animal model through mechanisms involving cell recruitment (eg, mast cells), release of inflammatory mediators, and deregulation of hypothalamic-pituitary axis responses in the hippocampus.