Understanding main pregnancy complications through animal models

Since human pregnancy is an inefficient process, achieving desired and pleasant outcome of pregnancy - the birth of a healthy and fit baby - is the main goal in any pregnancy. Spontaneous pregnancy failure is actually the most common complication of pregnancy and Most of these pregnancy losses are not known. Animal models have been utilized widely to investigate the system of natural biological adaptation to pregnancy along with increasing our comprehension of the most important hereditary and non-hereditary factors that contribute to pregnancy disorders. We use model organisms because their complexity better reproduces the human condition. A useful animal model for the disease should be pathologically similar to the disease conditions in humans. Animal models deserve a place in research because of the ethical limitations that apply to pregnant women's experiments. The present review provides insights into the overall risk factors involved in recurrent miscarriage, recurrent implant failure and preeclampsia and animal models developed to help researchers identify the source of miscarriage and the best research and treatment strategy for women with Repeated miscarriage and implant failure.

Developmental Exposure to Endocrine Disruptors Expands Murine Myometrial Stem Cell Compartment as a Prerequisite to Leiomyoma Tumorigenesis

Despite the high prevalence and major negative impact of uterine fibroids (UFs) on women's health, their pathogenesis remains largely unknown. While tumor-initiating cells have been previously isolated from UFs, the cell of origin for these tumors in normal myometrium has not been identified. We isolated cells with Stro1/CD44 surface markers from normal myometrium expressing stem cell markers Oct-4/c-kit/nanog that exhibited the properties of myometrial stem/progenitor-like cells (MSCs). Using a murine model for UFs, we showed that the cervix was a hypoxic "niche" and primary site (96%) for fibroid development in these animals. The pool size of these MSCs also responded to environmental cues, contracting with age and expanding in response to developmental environmental exposures that promote fibroid development. Translating these findings to women, the number of MSCs in unaffected human myometrium correlated with risk for developing UFs. Caucasian (CC) women with fibroids had increased numbers of MSCs relative to CC women without fibroids, and African-American (AA) women at highest risk for these tumors had the highest number of MSCs: AA-with fibroids > CC-with fibroids > AA-without fibroids > CC-without fibroids. These data identify Stro1⁺ /CD44⁺ MSCs as MSC/progenitor cell for UFs, and a target for ethnic and environmental factors that increase UF risk. Stem Cells 2017;35:666-678.

Endocrine-disrupting chemicals and uterine fibroids

Uterine fibroids are the most frequent gynecologic tumor, affecting 70% to 80% of women over their lifetime. Although these tumors are benign, they can cause significant morbidity and may require invasive treatments such as myomectomy and hysterectomy. Many risk factors for these tumors have been identified, including environmental exposures to endocrine-disrupting chemicals (EDCs) such as genistein and diethylstilbestrol. Uterine development may be a particularly sensitive window to environmental exposures, as some perinatal EDC exposures have been shown to increase tumorigenesis in both rodent models and human epidemiologic studies. The mechanisms by which EDC exposures may increase tumorigenesis are still being elucidated, but epigenetic reprogramming of the developing uterus is an emerging hypothesis. Given the remarkably high incidence of uterine fibroids and their significant impact on women's health, understanding more about how prenatal exposures to EDCs (and other environmental agents) may increase fibroid risk could be key to developing prevention and treatment strategies in the future.

Magnetic nanoparticles as a new approach to improve the efficacy of gene therapy against differentiated human uterine fibroid cells and tumor-initiating stem cells

OBJECTIVE

To study whether efficient transduction and subsequent elimination of fibroid tumor-initiating stem cells during debulking of tumor cells will aid in completely eradicating the tumor as well as decreasing the likelihood of recurrence.

DESIGN

Case control study.

SETTING

Research laboratory.

PATIENT(S)

None.

INTERVENTION(S)

Magnetic nanoparticles (MNPs) complexed to adenovirus (Ad-GFP) or (Ad-LacZ) used to transfect differentiated human fibroid cells in vitro.

MAIN OUTCOME MEASURE(S)

Rate of transduction and tumor growth inhibition.

RESULT(S)

We have developed a localized nonsurgical adenovirus-based alternative for the treatment of uterine fibroids that combines viral-based gene delivery with nanotechnology for more efficient targeting. Magnetic nanoparticles complexed to adenovirus, in the presence of an external magnetic field, accelerate adenovirus transduction. We observed a statistically significant increase in transduction efficiency among differentiated human fibroid cells at two different multiplicities of infection (MOI), 1 and 10, respectively, with MNPs as compared with adenovirus alone. Human fibroid stem cells transfected with Ad-LacZ expressed β-galactosidaze at a MOI of 1, 10, and 50 at 19%, 62%, and 90%, respectively, which were statistically significantly enhanced with MNPs.

CONCLUSION(S)

When applied with adenovirus herpes simplex thymidine kinase, magnetofection statistically significantly suppressed proliferation and induced apoptosis in both cell types. Through the use of magnetofection, we will prove that a lower viral dose will effectively increase the overall safety profile of suicide gene therapy against fibroid tumors.

Paricalcitol, a vitamin d receptor activator, inhibits tumor formation in a murine model of uterine fibroids

We examined the antitumor and therapeutic potentials of paricalcitol, an analog of 1,25-dihydroxyvitamin D3 with lower calcemic activity, against uterine fibroids using in vitro and in vivo evaluations in appropriate uterine fibroid cells and animal models. We found that paricalcitol has potential to reduce the proliferation of the immortalized human uterine fibroid cells. For the in vivo study, we generated subcutaneous tumors by injecting the Eker rat-derived uterine leiomyoma cell line (ELT-3) rat uterine fibroid-derived cell line in athymic nude mice supplemented with estrogen pellets. These mice were administered with vehicle versus paricalcitol (300 ng/kg/d) or 1,25-dihydroxyvitamin D3 (500 ng/kg/d) for 4 consecutive weeks, and the data were analyzed. We found that while both paricalcitol and 1,25-dihydroxyvitamin D3 significantly reduced fibroid tumor size, the shrinkage was slightly higher in the paricalcitol-treated group. Together, our results suggest that paricalcitol may be a potential candidate for effective, safe, and noninvasive medical treatment option for uterine fibroids.

Proceedings from the Third National Institutes of Health International Congress on Advances in Uterine Leiomyoma Research: comprehensive review, conference summary and future recommendations

BACKGROUND Uterine fibroids are the most common gynecologic tumors in women of reproductive age yet the etiology and pathogenesis of these lesions remain poorly understood. Age, African ancestry, nulliparity and obesity have been identified as predisposing factors for uterine fibroids. Symptomatic tumors can cause excessive uterine bleeding, bladder dysfunction and pelvic pain, as well as associated reproductive disorders such as infertility, miscarriage and other adverse pregnancy outcomes. Currently, there are limited noninvasive therapies for fibroids and no early intervention or prevention strategies are readily available. This review summarizes the advances in basic, applied and translational uterine fibroid research, in addition to current and proposed approaches to clinical management as presented at the 'Advances in Uterine Leiomyoma Research: 3rd NIH International Congress'. Congress recommendations and a review of the fibroid literature are also reported. METHODS This review is a report of meeting proceedings, the resulting recommendations and a literature review of the subject. RESULTS The research data presented highlights the complexity of uterine fibroids and the convergence of ethnicity, race, genetics, epigenetics and environmental factors, including lifestyle and possible socioeconomic parameters on disease manifestation. The data presented suggest it is likely that the majority of women with uterine fibroids will have normal pregnancy outcomes; however, additional research is warranted. As an alternative to surgery, an effective long-term medical treatment for uterine fibroids should reduce heavy uterine bleeding and fibroid/uterine volume without excessive side effects. This goal has not been achieved and current treatments reduce symptoms only temporarily; however, a multi-disciplined approach to understanding the molecular origins and pathogenesis of uterine fibroids, as presented in this report, makes our quest for identifying novel targets for noninvasive, possibly nonsystemic and effective long-term treatment very promising. CONCLUSIONS The Congress facilitated the exchange of scientific information among members of the uterine leiomyoma research and health-care communities. While advances in research have deepened our knowledge of the pathobiology of fibroids, their etiology still remains incompletely understood. Further needs exist for determination of risk factors and initiation of preventive measures for fibroids, in addition to continued development of new medical and minimally invasive options for treatment.

Human uterine smooth muscle and leiomyoma cells differ in their rapid 17beta-estradiol signaling: implications for proliferation

Uterine leiomyomas, benign uterine smooth muscle tumors that affect 30% of reproductive-aged women, are a significant health concern. The initiation event for these tumors is unclear, but 17beta-estradiol (E2) is an established promoter of leiomyoma growth. E2 not only alters transcription of E2-regulated genes but also can rapidly activate signaling pathways. The aim of our study is to investigate the role of rapid E2-activated cytoplasmic signaling events in the promotion of leiomyomas. Western blot analysis revealed that E2 rapidly increases levels of phosphorylated protein kinase C alpha (PKC alpha) in both immortalized uterine smooth muscle (UtSM) and leiomyoma (UtLM) cell lines, but increases levels of phosphorylated ERK1/2 only in UtLM cells. Our studies demonstrate a paradoxical effect of molecular and pharmacological inhibition of PKC alpha on ERK1/2 activation and cellular proliferation in UtLM and UtSM cells. PKC alpha inhibition decreases levels of phosphorylated ERK1/2 and proliferation in UtLM cells but raises these levels in UtSM cells. cAMP-PKA signaling is rapidly activated only in UtSM cells with E2 and inhibits ERK1/2 activation and proliferation. We therefore propose a model whereby E2's rapid activation of PKC alpha and cAMP-PKA signaling plays a central role in the maintenance of a low proliferative index in normal uterine smooth muscle via its inhibition of the MAPK cascade and these pathways are altered in leiomyomas to promote MAPK activation and proliferation. These studies demonstrate that rapid E2-signaling pathways contribute to the promotion of leiomyomas.

Gene therapy targeting leiomyoma: adenovirus-mediated delivery of dominant-negative estrogen receptor gene shrinks uterine tumors in Eker rat model

OBJECTIVE

To evaluate the utility of gene therapy for uterine fibroids in the Eker rat model using an adenovirus-mediated delivery of a dominant-negative estrogen receptor gene (Ad-DNER).

DESIGN

Animal study.

SETTING

University animal laboratory.

ANIMAL(S)

Twenty-seven female Eker rats.

INTERVENTION(S)

We randomized Eker rats with magnetic resonance imaging (MRI)-confirmed uterine leiomyomas to a single treatment of direct intrafibroid injection with Ad-DNER, Ad-bacterial ss-galactosidase, or vehicle.

MAIN OUTCOME MEASURE(S)

Tumor volumes were determined by MRI scanning and caliper measurement. Samples of serum, fibroid tumors, and various organs were collected at 8, 15, and 30 days after treatment to assess treatment safety and efficacy.

RESULT(S)

The Ad-DNER treatment significantly decreased uterine fibroid volume by 45%, 80%, and 77.4% of pretreatment volume at days 8, 15, and 30, respectively, and modulated the expression of apoptosis-, proliferation-, and extracellular matrix-related genes' compared with control animals. The Ad-DNER did not produce any toxic effects in nontarget tissues.

CONCLUSION(S)

The Ad-DNER treatment shrinks Eker rats' fibroids, in part, via modulation of several estrogen-regulated genes. This safe gene therapy approach presents a promising conservative treatment option for women with symptomatic uterine fibroids.

Concentration-dependent effects of a selective estrogen receptor modulator raloxifene on proliferation and apoptosis in human uterine leiomyoma cells cultured in vitro

BACKGROUND

This study was conducted to elucidate the effects of raloxifene on proliferation and apoptosis in cultured human uterine leiomyoma cells.

METHODS

The monolayer cultures were treated with graded concentrations (10(-9), 10(-8) and 10(-7) M) of raloxifene and 10(-7) M 17beta-estradiol (E(2)). Cell viability, percentage of proliferating cell nuclear antigen (PCNA)-positive cells, percentage of terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick-end labelling (TUNEL)-positive cells and the expression of PCNA and Bcl-2 proteins were assessed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxylphenyl)-2-(4-sulphophenyl)-2H-tetraz olium assay, immunocytochemistry, TUNEL assay and western blot analysis, respectively.

RESULTS

Compared with untreated cultures, the number of viable cultured cells, percentage of PCNA-positive cells and PCNA protein expression were significantly decreased by treatment with 10(-9) M raloxifene, but increased by treatment with either 10(-8) M or 10(-7) M raloxifene. In contrast, the percentage of TUNEL-positive cells was significantly increased and Bcl-2 protein expression was significantly decreased by treatment with 10(-9) M raloxifene, whereas they were not affected by treatment with either 10(-8) or 10(-7) M raloxifene.

CONCLUSIONS

In cultured leiomyoma cells, low concentration (10(-9) M) of raloxifene may inhibit the growth of leiomyoma cells, whereas high concentrations (10(-8) M, 10(-7) M) of raloxifene may promote their growth.

Gene therapy and uterine leiomyoma: a review

Leiomyomas (fibroids) are common estrogen-dependent uterine tumours that cause significant morbidity for women and a substantial economic impact on health delivery systems. Currently, there is no effective medical treatment option for this condition-hysterectomy is the mainstay of management. This is not an attractive choice for many women, especially patients desiring to preserve their fertility potential. Gene therapy is becoming a clinical reality, with more than 600 clinical trials worldwide. Researchers have recently attempted to develop a gene-therapy-based approach for the ablation of uterine fibroids. The localized nature of this condition and its accessibility using different imaging or endoscopic techniques make it an attractive target for direct delivery of gene-based vectors. Recent work from our laboratory suggests the potential use of a dominant-negative form of estrogen receptor (ER) to inactivate estrogen signalling in leiomyoma cells and induce apoptosis. Our in vivo data in a mouse model demonstrate the ability of an adenovirus-expressing dominant-negative ER to arrest leiomyoma growth. We and others also have described the utility of the herpes simplex virus-thymidine kinase (HSV-TK) plus ganciclovir (GCV) suicide gene-therapy system to effectively eradicate leiomyoma cells by utilizing the bystandard effect phenomena and the high expression of gap-junction protein in these tumours. Further work on rat models will pave the way for future leiomyoma gene-therapy clinical trials and allow the realization of gene therapy as a viable non-surgical option for this common problem in women's health.

A selective estrogen receptor modulator designed for the treatment of uterine leiomyoma with unique tissue specificity for uterus and ovaries in rats

The design of a novel selective estrogen receptor modulator (SERM) for the potential treatment of uterine leiomyoma is described. 16 (LY2066948-HCl) binds with high affinity to estrogen receptors alpha and beta (ERalpha and ERbeta, respectively) and is a potent uterine antagonist with minimal effects on the ovaries as determined by serum biomarkers and histologic evaluation.

A new selective estrogen receptor modulator with potent uterine antagonist activity, agonist activity in bone, and minimal ovarian stimulation

The use of selective estrogen receptor modulators for the treatment of estrogen-dependent diseases in premenopausal women has been hindered by undesirable ovarian stimulation and associated risks of ovarian cysts. We have identified a selective estrogen receptor modulator compound (LY2066948) that is a strong estrogen antagonist in the uterus yet has minimal effects on the ovaries of rats. LY2066948 binds with high affinity to both estrogen receptors and has potent estrogen antagonist activity in human uterine and breast cancer cells. Oral administration of LY2066948 to immature rats blocked uterine weight gain induced by ethynyl estradiol with an ED50 of 0.07 mg/kg. Studies in mature rats demonstrated that LY2066948 decreases uterine weight by 51% after 35 d treatment, confirming potent uterine antagonist activity over several estrous cycles. This strong uterine response contrasted with the minimal effects on the ovaries: serum estradiol levels remained within the normal range, whereas histologic evaluation showed granulosa cell hyperplasia in few of the rats. Bone studies demonstrated that LY2066948 prevented ovariectomy-induced bone loss and treatment of ovary-intact rats caused no bone loss, confirming estrogen receptor agonist skeletal effects. Collectively, these data show that LY2066948 exhibits a tissue-specific profile consistent with strong antagonist activity in the uterus, agonist activity in bone, and minimal effects in the ovaries.

Antiproliferative and proapoptotic effects of raloxifene on uterine leiomyomas in postmenopausal women

OBJECTIVE

To study the cell effects of raloxifene on uterine and leiomyoma tissue in postmenopausal women.

DESIGN

Prospective, randomized, double-blind, placebo-controlled study.

SETTING

Department of Obstetrics and Gynecology, University "Magna Graecia" of Catanzaro, Italy.

PATIENT(S)

Forty postmenopausal women affected by uterine leiomyomas and selected for hysterectomy.

INTERVENTION(S)

Treatment for three cycles of 28 days with raloxifene at a dose of 180 mg/day orally (raloxifene group) or placebo tablets (3 tablets/day orally) (placebo group).

MAIN OUTCOME MEASURE(S)

Uterine and leiomyoma dimensions were measured in each subject at entry and before surgery. On leiomyomas and homologous myometrium the proliferating cell nuclear antigen (PCNA)-positive cells/total cells (PCNA/TC) and the Bcl-2-positive cells/Bax-positive cells (Bcl-2/Bax) ratios (%), as proliferation and apoptotic indexes, respectively, were measured.

RESULT(S)

After treatment, uterine and leiomyoma sizes were significantly changed in comparison with baseline and the placebo group. PCNA/TC and Bcl-2/Bax ratios were significantly higher in leiomyomas than in homologous myometrium. A significant difference was detected in PCNA/TC between the myometrium of the raloxifene and control groups, whereas no difference was observed in the Bcl-2/Bax ratio. A significant difference in PCNA/TC and Bcl-2/Bax ratios was detected in leiomyoma tissue between the raloxifene group and controls.

CONCLUSION(S)

In postmenopausal women, raloxifene administration reduces uterine leiomyomas by exerting a cell antiproliferative and proapoptotic action.

Raloxifene prevents the growth of uterine leiomyomas in premenopausal women

OBJECTIVE

To evaluate the effects of raloxifene administration on uterine leiomyoma size in premenopausal women.

DESIGN

Prospective, randomized, open-label, controlled clinical trial.

SETTING

Tertiary care unit, University of Vienna, Austria.

PATIENT(S)

Twenty-five premenopausal women with uterine leiomyomas.

INTERVENTION(S)

Three months of treatment with raloxifene (180 mg/d) or no treatment.

MAIN OUTCOME MEASURE(S)

Baseline to end point percent change difference in leiomyoma volume between the therapy and control groups.

RESULT(S)

Raloxifene treatment prevented the progression of uterine leiomyomas. Compared with no medical intervention, raloxifene resulted in a decrease of myoma volume. Raloxifene was clinically well tolerated. No significant differences were detected in symptoms related to leiomyomas and hormonal status.

CONCLUSION(S)

In premenopausal women, high-dose raloxifene is well tolerated and inhibits the growth of leiomyomas.

Uterine leiomyoma in the Eker rat: A unique model for important diseases of women

Eker rats carry a defect in the Tsc-2 tumor suppressor gene and female Eker rats develop uterine leiomyoma with a high frequency. The presentation, response to hormones and molecular alterations in these mesenchymal smooth muscle tumors, closely resembles their cognate human disease. Female rats and tumor-derived cell lines from Eker rat leiomyomas (ELT lines) have been developed as an in vivo/in vitro model system for preclinical studies to identify novel therapeutic agents for this disease and for studying disease pathogenesis. In addition to serving as a model for uterine leiomyoma, Eker rats have proven valuable for studying lymphangioleiomyomatosis, a related proliferative smooth muscle disease of women.

Successful treatment of a symptomatic uterine leiomyoma in a perimenopausal woman with a nonsteroidal aromatase inhibitor

OBJECTIVE

To assess the management of symptomatic leiomyomas using a nonsteroidal aromatase inhibitor in perimenopausal women.

DESIGN

Case report.

SETTING

Academic clinical practice.

PATIENT(S)

A 53-year-old woman suffering from recurrent urinary retention secondary to a uterine leiomyoma.

INTERVENTION(S)

Fadrozole, orally, 2 mg daily for 8 weeks and then 1 mg daily for 4 weeks.

MAIN OUTCOME MEASURE(S)

Measurements of leiomyoma volume, and levels of serum E(2), LH, and FSH.

RESULT(S)

Urinary retention resolved after 2 weeks of treatment and did not recur. Leiomyoma volume estimated by ultrasonography revealed a 71% reduction after 8 weeks of treatment.

CONCLUSION(S)

Fadrozole was useful for the management of a symptomatic leiomyoma without transient deterioration of symptoms. Clinical trials are warranted.

A benefit-risk assessment of medical treatment for uterine leiomyomas

The growth of a uterine leiomyoma growth stops and regresses after the menopause suggesting that leiomyoma growth is dependent on ovarian steroids. Therefore, estrogen has received much attention as the major factor responsible for the development of uterine leiomyomas, but progesterone also plays an important role in development of this disease. Cytogenetic analyses of resected samples has revealed that about 40 to 50% of leiomyomas show karyotypically detectable chromosomal abnormalities. Gonadotrophin releasing hormone (GnRH) agonists exert their action through the suppression of endogenous gonadotrophins and gonadal steroid secretion. Significant reductions of uterine/leiomyoma volume under GnRH agonist therapy has been reported in several studies. However, the leiomyoma generally returns to its pretreatment volume within a few months after discontinuation of the GnRH agonist. To minimise the adverse effects of hypoestrogenism during GnRH agonist treatment, add back therapy can be used (estrogen-progestin, progestin alone and recently tibolone). Antiprogestins have a potential clinical utility in uterine leiomyomas. Mifepristone is a synthetic steroid with both antiprogesterone and antiglucocorticoid activities, that may have an inhibitory effect on growth of leiomyoma. Danazol is an isoxazole of 17beta-ethinyl testosterone, a synthetic steroid, which has a suppressive effect on sex hormone binding globulin concentrations, resulting in efficacy in the short-term treatment of uterine leiomyomas. Gestrinone is a tri-enic steroid with antiestrogen and antiprogesterone properties and has been shown to reduce uterine volume and stop bleeding. Growth factors play a relevant role on the pathophysiology of uterine leiomyoma and probably the inhibition of the action of growth factors on the myometrium will be the basis for future therapy. A number of agents are under investigation for treating uterine leiomyoma. Agents developed from increasing genetic knowledge of this condition could represent, in the next few years, new trends in the medical treatment of uterine leiomyomas.

Protective effect of pregnancy for development of uterine leiomyoma

Many factors that can modulate the risk of developing uterine leiomyoma have been identified, including parity. Epidemiological data on decreased risk of developing this disease has been subject to different interpretations regarding whether pregnancy per se is protective or, as leiomyomas are a major cause of infertility, women that develop these tumors are less fertile and thus have lower pregnancy rates. We have utilized an animal model genetically predisposed to uterine leiomyoma to investigate the potential protective effect of pregnancy on the risk of developing this disease. Female Eker rats that carry a mutation in the tuberous sclerosis 2 (Tsc-2) tumor suppressor gene develop uterine leiomyoma with a frequency of 65% when nulliparous. These animals were bred with intact or vasectomized males and tumor incidence determined after a single pregnancy (to confirm fertility) or multiple pregnancies over the lifetime of the animals. Females with multiple litters displayed a dramatic shift in tumor incidence and presentation. Tumor incidence decreased from 71% in single litter females to 10% in females that had multiple litters (average: five litters/animal). Interestingly, females bred with vasectomized males also exhibited a reduced tumor incidence of 41%, suggesting that the hormonal changes associated with early stages of pregnancy that occur in pseudopregnant females may have contributed to the protective effect of pregnancy.

An in vivo/in vitro model to assess endocrine disrupting activity of xenoestrogens in uterine leiomyoma

Xenoestrogens with endocrine disrupting activity have been associated with the dysregulation of reproductive function and promotion of malignancies in experimental animals and human populations. The high incidence of uterine leiomyomas, a benign estrogen-responsive neoplasm of the uterine myometrium, calls into question the potential influence of xenoestrogens in the pathogenesis of these tumors. An in vivo/in vitro animal model, the Eker rat, that can be used to assess the estrogen-like agonist activity of potential endocrine disruptors in the uterine myometrium is discussed. Using this model, several in vitro assays are developed that demonstrate that compounds from three major classes of xenoestrogens can mimic the effect of estrogen on leiomyoma cells and act as estrogen receptor (ER) agonists: phytoestrogens, organochlorine pesticides and pharmacologic agents. These compounds can stimulate transcription via the ER and upregulate the expression of an estrogen-responsive gene in uterine leiomyoma cells. The use of these in vitro assays has also advanced our ability to predict the agonist activity of potential therapeutic agents in the uterine myometrium. Selective estrogen receptor modulators (SERMs), while able to act as agonists in some tissues such as the bone and uterine endometrium, act as antagonists in vivo in the uterine myometrium and in our in vitro assays. This antagonist activity in the uterine myometrium suggests that SERMs may be useful in the treatment of uterine leiomyoma.

Estrogen-associated genes in uterine leiomyoma

Uterine leiomyomas or fibroids are classified as a benign uterine disease in that the polyps display no malignant growth. However, uterine leiomyomas are a leading cause of morbidity, infertility, and hysterectomy in women. Since leiomyomas are known to be sensitive to estrogen for their growth, we have examined uterine genes known to be estrogen responsive in affected and unaffected uterine tissue. This information will be useful in determining the contribution, if any, of hormonally active environmental chemicals to this highly prevalent reproductive disorder.

Uterine fibroids

Uterine leiomyomas (fibroids or myomas), benign tumours of the human uterus, are the single most common indication for hysterectomy. They are clinically apparent in up to 25% of women and cause significant morbidity, including prolonged or heavy menstrual bleeding, pelvic pressure or pain, and, in rare cases, reproductive dysfunction. Thus, both the economic cost and the effect on quality of life are substantial. Surgery has been the mainstay of fibroid treatment, and various minimally invasive procedures have been developed in addition to hysterectomy and abdominal myomectomy. Formation of new leiomyomas after these conservative therapies remains a substantial problem. Although medications that manipulate concentrations of steroid hormones are effective, side-effects limit long-term use. A better approach may be manipulation of the steroid-hormone environment with specific hormone antagonists. There has been little evidence-based evaluation of therapy. New research into the basic biology of these neoplasms may add new treatment options for the future as the role of growth factors and genetic mutations in these tumours are better understood.

Uterine leiomyomas: mechanisms of tumorigenesis

Uterine leiomyomas, also called fibroids, are the most common reproductive tract neoplasm and the leading indication for hysterectomy in premenopausal women. The discovery and development of medicinal therapies for uterine leiomyoma have been hampered by a lack of understanding regarding the etiology and molecular mechanisms underlying the development of these lesions. Although the estrogen responsiveness of uterine leiomyoma is well established, the impact of environmental estrogens and their contribution to the development of these tumors is currently unknown. The Eker rat model of uterine leiomyoma has proven useful for addressing these issues and understanding the pathophysiology of this disease. The Eker rat is the only animal model that develops spontaneous uterine leiomyomas, and these tumors share many characteristics with those found in humans. The availability of tumor-derived cell lines from these rats has made this a valuable in vitro/in vivo model system for experimental studies to investigate molecular mechanisms of disease and to design interventional and preventative strategies for this clinically relevant tumor.