Effects of an antiprogestin onapristone on the endometrium of bonnet monkeys: morphometric and ultrastructural studies

Progesterone receptor blockers: historical perspective, mode of function and insights into clinical and scientific applications

Antigestagens (antiprogestins) are functional competitors of progesterone (P4) that prevent P4 from mediating its biological functions either by suppressing its production or blocking its function. Among the latter are progesterone antagonists, competitors of P4 binding to its nuclear receptor PGR, which have found application in both human and veterinary medicine, in particular in small animal practice for the prevention of nidation and the interruption of pregnancy. Depending on their mode of action, progesterone receptor antagonists can be divided into 2 classes. Class I antagonists bind to the PGR but fail to induce its binding to promoters of target genes (competitive inhibitors). Class II antigestagens, including aglepristone used in veterinary medicine, bind to the PGR, activate its association with a promoter, but interfere with the downstream signalling cascades, e. g., by recruiting transcriptional repressors. They act thereby as transdominant repressors exerting negative effects on target gene expression. Importantly for experimental sciences, as active antagonists, class II antagonists do not require the presence of the natural ligand for their action. Besides their clinical application, antigestagens are used in research for investigating P4-dependent physiological and pathological processes. Here an overview of the history and the current usage of progesterone receptor antagonists in veterinary medicine and research is presented.

Medical Management of Endometriosis

Endometriosis is a chronic medical condition that affects around 6% to 10% of reproductive age women. Pelvic pain, dysmenorrhea, and infertility are the most common presenting symptoms. The disease is characterized by estrogen-dependent growth of the endometrial glands and stroma outside the endometrial cavity. The diagnosis requires a high degree of suspicion and can be only confirmed on histopathology. Treatment includes medical and surgical options. Both hormonal and nonhormonal medical options are available and are tried at first with a goal to control pain and stop the growth of the endometriotic lesions. Nonsteroidal anti-inflammatory drugs, oral contraceptive pills, gonadotropin-releasing hormone (GnRH) agonists, aromatase inhibitors are some of the commonly used medications. With more research on the molecular and biochemical aspects of endometriosis, newer targets of therapy are being developed like selective progesterone receptor modulators, antiangiogenic factors and immunomodulators. In women who do not respond to medical therapy or have severe symptoms, surgical excision of the endometrial lesions and adhesions is often helpful and offers confirmatory diagnosis by histopathology.

Echography of the cervix and uterus during the proliferative and secretory phases of the menstrual cycle in bonnet monkeys (Macaca radiata)

We undertook the present study to investigate the echographic characteristics of the uterus and cervix of female bonnet monkeys ( Macaca radiata ) during the proliferative and secretory phases of the menstrual cycle. The cervix was tortuous in shape and measured 2.74 ± 0.30 cm (mean ± SD) in width by 3.10 ± 0.32 cm in length. The cervical lumen contained 2 or 3 colliculi, which projected from the cervical canal. The echogenicity of cervix varied during proliferative and secretory phases. The uterus was pyriform in shape (2.46 ± 0.28 cm × 1.45 ± 0.19 cm) and consisted of serosa, myometrium, and endometrium. The endometrium generated a triple-line pattern; the outer and central lines were hyperechogenic, whereas the inner line was hypoechogenic. The endometrium was significantly thicker during the secretory phase (0.69 ± 0.12 cm) than during the proliferative phase (0.43 ± 0.15 cm). Knowledge of the echogenic changes in the female reproductive organs of bonnet monkeys during a regular menstrual cycle may facilitate understanding of other physiologic and pathophysiologic changes.

An update on the pharmacological management of endometriosis

INTRODUCTION

Endometriosis is a common disease that causes pain symptoms and/or infertility in women in their reproductive years. The disease is characterised by the presence of endometrium-like tissue - glands and stroma - outside the uterine cavity. Different treatment options exist for endometriosis including medical and surgical treatments or a combination of the two approaches. The most commonly used medications are non-steroidal anti-inflammatory drugs, GnRH agonists, androgen derivatives such as danazol, combined oral contraceptive pills, progestogens and more recently the levonorgestrel intrauterine system.

AREAS COVERED

The authors review current medical treatments used for symptomatic endometriosis and also discuss new treatment approaches. The authors conducted a literature search for randomised controlled trials related to medical treatments of endometriosis in humans, searched the Cochrane library for reviews and also searched for registered trials that have not yet been published on ClinicalTrials.gov.

EXPERT OPINION

The medical treatment of endometriosis is effective at treating pain and preventing recurrence of disease after surgery. Remarkably, the oral contraceptive pill taken continuously is as effective as GnRH-a, while causing far less side-effects. Conversely, no treatment currently exists for enhancing fecundity in women whose infertility is associated with endometriosis. As all existing therapies of endometriosis are contraceptive, great efforts should be targeted at researching novel products that reduce the disease expression without shuttering ovulation.

New treatment strategies and emerging drugs in endometriosis

Introduction: Endometriosis, histologically defined as the presence of endometrium-like tissue - glands and stroma - that develops outside of the uterine cavity, is still an enigmatic disease responsible for pelvic pain and infertility. The current treatments of endometriosis are surgery and hormonal therapies that act by suppressing ovulation and/or directly on steroid receptors located in endometriotic lesions. Areas covered: New hormonal and non-hormonal therapies are being developed for the treatment of endometriosis-related pain. The authors review the state of advancement and the results of novel treatments studied in registered trials ( www.ClinicalTrials.gov ). Cellular signaling pathways activated in endometriotic cells, which constitute potential targets for future treatments, are also described. Expert opinion: Therapeutic research efforts should focus on identifying and testing substances capable of acting locally on the lesions themselves, without interfering with ovulation, in order to be efficacious on both pain symptoms and infertility.

Endometrial modifications during early pregnancy in bonnet monkeys (Macaca radiata)

The present study was undertaken to investigate endometrial modifications that occur before embryo invasion in bonnet monkeys (Macaca radiata). These changes were analysed in luminal epithelium, glandular epithelium and stroma of endometrial functionalis on Day 6 post ovulation from pregnant and non-pregnant animals (n = 4 each) by transmission electron microscopy. Distinct features (i.e. loss of columnar shape by epithelial cells, changes in mitochondrial size and diffused apicolateral gap junctions) were observed in the luminal and glandular epithelium in pregnant animals. Stromal compaction was also observed in pregnant animals. Further, immunogold localisation studies demonstrated significantly higher expression (P < 0.05) of oestrogen receptor alpha, an oestrogen-regulated gene, in the glandular epithelium and stroma of the endometrium in pregnant animals compared with non-pregnant animals. Expression of two other genes known to be regulated by oestradiol, namely beta-actin and cyclo-oxygenase-1, were also significantly higher (P < 0.05) in the endometria of pregnant animals. These studies demonstrate marked changes in the endometrium before embryo invasion in bonnet monkeys. These studies also indicate altered oestrogenic activity in the uterine milieu before embryo invasion.

Mifepristone alters expression of endometrial steroid receptors and their cofactors in new users of medroxyprogesterone acetate

OBJECTIVE

To evaluate the effect of mifepristone on the expression of endometrial steroid receptors and their co-factors in depot medroxyprogesterone acetate (DMPA) users.

DESIGN

A prospective, randomized, placebo-controlled trial.

SETTING

Reproductive research center.

PATIENT(S)

Fifty healthy women with regular menstrual cycle.

INTERVENTION(S)

One hundred fifty milligrams of DMPA were given every 3 months. Two pills (25 mg each) of placebo or mifepristone were administered every 14 days during the DMPA therapy. Four endometrial biopsy specimens were obtained from each patient.

MAIN OUTCOME MEASURE(S)

The expression of estrogen receptor subtypes alpha and beta (ERalpha and ERbeta), progesterone receptors A and B (PRAB and PRB), and androgen receptor messenger RNA and protein was detected by real-time polymerase chain reaction and immunohistochemistry, respectively. Steroid receptor coactivator 1 (SRC-1), silencing mediator for retinoid and thyroid-hormone receptors, and cell proliferation were evaluated by immunohistochemistry.

RESULT(S)

The expression of endometrial ERalpha, PRAB, PRB, and SRC-1 was increased significantly after 1 week of mifepristone, but the increase was no longer seen after 10 weeks. A positive correlation between endometrial ERalpha, PRAB, PRB, and SRC-1 production and proliferation was demonstrated.

CONCLUSION(S)

Short-term exposure of mifepristone in new starters of DMPA increases the expression of endometrial ERalpha, PRAB, PRB, and SRC-1 and promotes cell proliferation. Prolonged exposure to mifepristone does not alter the suppression of these receptors that are caused by DMPA and continues to result in endometrial atrophy.

Therapeutic administration of progesterone antagonist in a model of Charcot-Marie-Tooth disease (CMT-1A)

Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy. The predominant subtype, CMT-1A, accounts for more than 50% of all cases and is associated with an interstitial chromosomal duplication of 17p12 (refs. 2,3). We have generated a model of CMT-1A by introducing extra copies of the responsible disease gene, Pmp22 (encoding the peripheral myelin protein of 22 kDa), into transgenic rats. Here, we used this model to test whether progesterone, a regulator of the myelin genes Pmp22 and myelin protein zero (Mpz) in cultured Schwann cells, can modulate the progressive neuropathy caused by moderate overexpression of Pmp22. Male transgenic rats (n = 84) were randomly assigned into three treatment groups: progesterone, progesterone antagonist (onapristone) and placebo control. Daily administration of progesterone elevated the steady-state levels of Pmp22 and Mpz mRNA in the sciatic nerve, resulting in enhanced Schwann cell pathology and a more progressive clinical neuropathy. In contrast, administration of the selective progesterone receptor antagonist reduced overexpression of Pmp22 and improved the CMT phenotype, without obvious side effects, in wild-type or transgenic rats. Taken together, these data provide proof of principle that the progesterone receptor of myelin-forming Schwann cells is a promising pharmacological target for therapy of CMT-1A.