Pathobiology of myomatosis uteri: the underlying knowledge to support our clinical practice

INTRODUCTION

Uterine myomatosis, a benign condition, is the most common indication for hysterectomies worldwide, affecting the reproductive goals and quality of health of women. However, gynecologists have been provided with interesting insights on its pathobiology, which are the basis for uterine-preserving therapies. The aim of this paper is to discuss the latest evidence on these mechanisms and its importance in the clinical practice.

METHOD

A comprehensive literature search was made in Pubmed, Medline, the Cochrane Library, Orbis plus and Google Scholar for articles related to the epidemiological, biological, and genetic bases.

RESULTS

There is extensive evidence that genetic, epigenetic, hormonal, environmental, proinflamatory, angiogenetic, and growing factors are involved in the biology of myomatosis. Such factors are capable of activating and promoting inhibitory signaling pathways leading to initiation, development, and regression of myomata through changes in myometrial cells and myomata fibers, such as cellular proliferation, differentiation, apoptosis, angiogenesis, and changes in the surrounding environment.

CONCLUSION

A good understanding of the pathobiologic mechanisms of myomatosis gives reasons to physicians to elect conservative or combined therapies, and allow affected women to receive an individualized management, according to age, reproduction desire, and clinical condition.

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.

Gene expression in uterine leiomyoma from tumors likely to be growing (from black women over 35) and tumors likely to be non-growing (from white women over 35)

The study of uterine leiomyomata (fibroids) provides a unique opportunity to investigate the physiological and molecular determinants of hormone dependent tumor growth and spontaneous tumor regression. We conducted a longitudinal clinical study of premenopausal women with leiomyoma that showed significantly different growth rates between white and black women depending on their age. Growth rates for leiomyoma were on average much higher from older black women than for older white women, and we now report gene expression pattern differences in tumors from these two groups of study participants. Total RNA from 52 leiomyoma and 8 myometrial samples were analyzed using Affymetrix Gene Chip expression arrays. Gene expression data was first compared between all leiomyoma and normal myometrium and then between leiomyoma from older black women (age 35 or older) and from older white women. Genes that were found significant in pairwise comparisons were further analyzed for canonical pathways, networks and biological functions using the Ingenuity Pathway Analysis (IPA) software. Whereas our comparison of leiomyoma to myometrium produced a very large list of genes highly similar to numerous previous studies, distinct sets of genes and signaling pathways were identified in comparisons of older black and white women whose tumors were likely to be growing and non-growing, respectively. Key among these were genes associated with regulation of apoptosis. To our knowledge, this is the first study to compare two groups of tumors that are likely to have different growth rates in order to reveal molecular signals likely to be influential in tumor growth.

A novel mouse model that closely mimics human uterine leiomyomas

OBJECTIVE

To develop a predictive mouse model for uterine fibroids.

DESIGN

Human fibroid cells xenografted to immunodeficient mice.

SETTING

University and industrial research center.

ANIMAL(S)

Immunodeficient scid/beige mice.

INTERVENTION(S)

Subcutaneous and intrauterine injection of fibroid-derived cells, SV40 transformation of primary cells by lentiviral transduction, proliferation determined by immunohistochemistry, FISH.

MAIN OUTCOME MEASURE(S)

Characterization of primary and immortalized cells by Western blot and soft agar assay, determination of in vivo tumorigenicity, comparative histology and immunohistochemistry, fluorescence in situ hybridization.

RESULT(S)

Tumorigenicity of primary myoma cells disappears upon in vitro culture. Transformation and immortalization does not restore or conserve the in vivo growth potential of cultured cells. Injection of primary cells into myometrium of mice leads to xenografts with a leiomyoma-like histology.

CONCLUSION(S)

Primary myoma cells are suited to generate fibroid-like xenografts for studying pathogenesis without genetic modifications. In contrast, in vitro culture abolishes transplantability, and neither transformation nor immortalization is sufficient to restore tumorigenic capacity.

Growth factors and myometrium: biological effects in uterine fibroid and possible clinical implications

BACKGROUND

Growth factors are proteins secreted by a number of cell types that are capable of modulating cellular growth, proliferation and cellular differentiation. It is well accepted that uterine cellular events such as proliferation and differentiation are regulated by sex steroids and their actions in target tissues are mediated by local production of growth factors acting through paracrine and/or autocrine mechanisms. Myometrial mass is ultimately modified in pregnancy as well as in tumour conditions such as leiomyoma and leiomyosarcoma. Leiomyomas, also known as fibroids, are benign tumours of the uterus, considered to be one of the most frequent causes of infertility in reproductive years in women.

METHODS

For this review, we searched the database MEDLINE and Google Scholar for articles with content related to growth factors acting on myometrium; the findings are hereby reviewed and discussed.

RESULTS

Different growth factors such as epidermal growth factor (EGF), transforming growth factor-α (TGF-α), heparin-binding EGF (HB-EGF), acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF), platelet-derived growth factor (PDGF) and TGF-β perform actions in myometrium and in leiomyomas. In addition to these growth factors, activin and myostatin have been recently identified in myometrium and leiomyoma.

CONCLUSIONS

Growth factors play an important role in the mechanisms involved in myometrial patho-physiology.

Uterine myomas during pregnancy: a longitudinal sonographic study

OBJECTIVE

To evaluate volumetric changes of uterine myomas (fibroids) during pregnancy.

METHODS

This was an observational, longitudinal and prospective study of 38 consecutive Caucasian women with singleton pregnancies and a total of 42 uterine myomas, enrolled from a cohort of 1492 women who took part in our first-trimester Down syndrome screening program. Myoma volume was evaluated by ultrasound at 11-14, 20-22 and 32-34 weeks of gestation.

RESULTS

Mean myoma volume increased significantly throughout pregnancy. Taking a volumetric change of > 10% between gestational periods to be an increase in size, 71.4% of uterine myomas increased in size between the first and second gestational periods, while this percentage was slightly lower (66.6%) between the second and third periods. Logistic regression analysis revealed that greater maternal age was correlated with a reduction/no change in overall myoma size and multiparity was correlated with a decrease/no change between the first and second trimesters, while a higher prepregnancy maternal body mass index (BMI) was correlated with a volumetric increase between the first and second trimesters and a decrease/no change between the second and third trimesters.

CONCLUSIONS

Fibroids enlarge during pregnancy regardless of their initial size or local factors, and maternal age, prepregnancy BMI and parity are apparently correlated with these changes.

Oxytocin-induced cell growth proliferation in human myometrial cells and leiomyomas

OBJECTIVE

To assess the expression of the oxytocin receptor (OTR) and the role of oxytocin (OT) in the proliferation of myometrial and leiomyoma cells.

DESIGN

Prospective laboratory study.

SETTING

Research laboratory at the Italian National Research Council.

PATIENT(S)

Twenty-two women who underwent therapeutic myomectomy for fibroids.

INTERVENTION(S)

Primary cultures of leiomyoma and myometrium cells were established from eutopic and ectopic myometrial tissues. An immortalized myometrial cell line (h-TERTmyo) and a leiomyosarcoma cell line (SK-UT-1) were also characterized.

MAIN OUTCOME MEASURE(S)

Expression of OTR and desmin mRNA was determined by quantitative real-time polymerase chain reaction. Cell growth was determined by 3-[4,5-dimethylthiazol-2-yl]5-(3-carboxymethoxyphenyl)2-(4-sulfophenyl)-2H tetrazolium assay. Apoptosis was determined by annexin V cell staining and flow cytometry analysis.

RESULT(S)

Oxytocin stimulated proliferation of primary myometrial and leiomyoma cells but inhibited the proliferation of h-TERTmyo and SK-UT-1, indicating a change in phenotype during immortalization. A progressive and rapid decrease in desmin and OTR mRNA was observed in primary cultures, indicating that myometrial cells dedifferentiate very rapidly in culture. The relative expression of OTR mRNA varied widely in both myometrial and leiomyoma smooth muscle cells, but there was no significant difference.

CONCLUSION(S)

These results indicate that OT stimulates the proliferation of both myometrial and leiomyoma cells, demonstrating that the OT/OTR system plays an important role in regulating uterine cell growth and providing a rationale for evaluating the use of OTR antagonists in managing uterine myomas.

General gynaecology: Effect of uterotonics on intra-operative blood loss during laparoscopy-assisted vaginal hysterectomy: a randomised controlled trial

OBJECTIVE

To investigate the effectiveness of uterotonics misoprostol and oxytocin on reducing blood loss during laparoscopy-assisted vaginal hysterectomy (LAVH).

DESIGN

Randomised, double-blind placebo-controlled trial.

SETTING

University hospital.

POPULATION

One hundred and seventy-three women underwent LAVH for symptomatic uterine myomas and were randomly allocated to uterotonics (n = 91) or placebo (n = 82).

METHODS

Women underwent LAVH for symptomatic uterine myomas and were randomly assigned to receive either rectal misoprostol (400 microg) and intravenous oxytocin (10 IU/hour) or placebo during LAVH. Parameters related to surgical outcome were compared.

MAIN OUTCOME MEASURES

The main outcome measure was intra-operative blood loss.

RESULTS

Patient characteristics and indications for LAVH were similar in both groups. Mean [SD] for all continuous data estimated weight of blood loss (198.1 [123.2] vs 396 [337.6] g; P < 0.0001), mean operation time (106.2 [39.4] vs 116.6 [34.6] minutes; P = 0.02), mean change in haemoglobin (1.5 [1.0] vs 1.9 [1.2] g/dL; P = 0.02) and haematocrit levels (4.8 [2.9]% vs 5.8 [3.6]%; P = 0.04) and mean hospitalisation period (3.3 [0.8] vs 3.9 [1.1] days; P < 0.0001), which were significantly less in the group given rectal misoprostol and intravenous oxytocin than in the placebo group, respectively. There was no significant difference in complications and side effects between the two groups (P > 0.05).

CONCLUSION

Combined rectal misoprostol and intravenous oxytocin is a feasible and effective method of reducing blood loss and operation time in LAVH.