Expression of nuclear estrogen-binding sites within developing human fetal vagina and urogenital sinus

Classic genetic and hormonal switches during fetal sex development and beyond

Critical genetic and hormonal switches characterize fetal sex development in humans. They are decisive for gonadal sex determination and subsequent differentiation of the genital and somatic sex phenotype. Only at the first glace these switches seem to behave like the dual 0 and 1 system in computer sciences and lead invariably to either typically male or female phenotypes. More recent data indicate that this model is insufficient. In addition, in case of distinct mutations, many of these switches may act variably, causing a functional continuum of alterations of gene functions and -dosages, enzymatic activities, sex hormone levels, and sex hormone sensitivity, giving rise to a broad clinical spectrum of biological differences of sex development (DSD) and potentially diversity of genital and somatic sex phenotypes. The gonadal anlage is initially a bipotential organ that can develop either into a testis or an ovary. Sex-determining region Y (SRY) is the most important upstream switch of gonadal sex determination inducing SOX9 further downstream, leading to testicular Sertoli cell differentiation and the repression of ovarian pathways. If SRY is absent (virtually "switched off"), e. g., in 46,XX females, RSPO1, WNT4, FOXL2, and other factors repress the male pathway and promote ovarian development. Testosterone and its more potent derivative, dihydrotestosterone (DHT) as well as AMH, are the most important upstream hormonal switches in phenotypic sex differentiation. Masculinization of the genitalia, i. e., external genital midline fusion forming the scrotum, growth of the genital tubercle, and Wolffian duct development, occurs in response to testosterone synthesized by steroidogenic cells in the testis. Müllerian ducts will not develop into a uterus and fallopian tubes in males due to Anti-Müllerian-Hormone (AMH) produced by the Sertoli cells. The functionality of these two hormone-dependent switches is ensured by their corresponding receptors, the intracellular androgen receptor (AR) and the transmembrane AMH type II receptor. The absence of high testosterone and high AMH is crucial for anatomically female genital development during fetal life. Recent technological advances, including single-cell and spatial transcriptomics, will likely shed more light on the nature of these molecular switches.

The mysteries of menopause and urogynecologic health: clinical and scientific gaps

OBJECTIVES

A significant body of knowledge implicates menopausal estrogen levels in the pathogenesis of the common pelvic floor disorders (PFDs). These health conditions substantially decrease quality of life, increase depression, social isolation, caregiver burden, and economic costs to the individuals and society.

METHODS

This review summarizes the epidemiology of the individual PFDs with particular attention to the understanding of the relationship between each PFD and menopausal estrogen levels, and the gaps in science and clinical care that affect menopausal women. In addition, we review the epidemiology of recurrent urinary tract infection (rUTI)-a condition experienced frequently and disproportionately by menopausal women and hypothesized to be potentiated by menopausal estrogen levels.

RESULTS

The abundance of estrogen receptors in the urogenital tract explains why the natural reduction of endogenous estrogen, the hallmark of menopause, can cause or potentiate PFDs and rUTIs. A substantial body of epidemiological literature suggests an association between menopause, and PFDs and rUTIs; however, the ability to separate this association from age and other comorbid conditions makes it difficult to draw definitive conclusions on the role of menopause alone in the development and/or progression of PFDs. Similarly, the causative link between the decline in endogenous estrogen levels and the pathogenesis of PFDs and rUTIs has not been well-established.

CONCLUSIONS

Innovative human studies, focused on the independent effects of menopausal estrogen levels, uncoupled from tissue and cellular senescence, are needed.

Molecular mechanisms of development of the human fetal female reproductive tract

Human female reproductive tract development rests mostly upon hematoxilyn and eosin stained sections despite recent advances on molecular mechanisms in mouse studies. We report application of immunohistochemical methods to explore the ontogeny of epithelial and mesenchymal differentiation markers (keratins, homobox proteins, steroid receptors), transcription factors and signaling molecules (TP63 and RUNX1) during human female reproductive tract development. Keratins 6, 7, 8, 10, 14 and 19 (KRT6, KRT7, KRT8, KRT10, KRT14, KRT19) were expressed in a temporally and spatially dynamic fashion. The undifferentiated Müllerian duct and uterovaginal canal, lined by simple columnar epithelia, expressed KRT7, KRT8 and KRT19. Glandular derivatives of the Müllerian duct (uterine tube, uterine corpus and endocervix) maintained expression of these keratins, while tissues that undergo stratified squamous differentiation (exocervix and vagina) expressed KRT6, KRT14 and KRT10 during development in an age-dependent fashion. TP63 and RUNX1 were expressed prior to KRT14, as these two transcription factors are known to be upstream from KRT14 in developing Müllerian epithelium. In the vagina, KRT10, a marker of terminal differentiation, appeared after endogenous estrogens transformed the epithelium to a thick glycogenated squamous epithelium. Uroplakin, a protein unique to urothelium, was expressed only in the bladder, urethra and vaginal introitus, but not in the female reproductive tract itself. Mesenchymal differentiation was examined through immunostaining for HOXA11 (expressed in uterine mesenchyme) and ISL1 (expressed in vaginal mesenchyme). A detailed ontogeny of estrogen receptor alpha (ESR1), progesterone receptor (PGR) and the androgen receptor (AR) provides the mechanistic underpinning for the teratogenicity of estrogens, progestins and androgens on female reproductive tract development. Immunohistochemical analysis of differentiation markers and signaling molecules advance our understanding of normal development of the human female reproductive tract. These observations demonstrate remarkable similarities in mouse and human female reproductive tract development, but also highlight some key differences.

Methods for studying human organogenesis

This review details methods for utilizing D & C suction abortus specimens as a source of human fetal organs to study the morphogenetic and molecular mechanisms of human fetal organ development. By this means it is possible to design experiments elucidating the molecular mechanisms of human fetal organ development and to compare and contrast human developmental mechanisms with that of laboratory animals. Finally human fetal organs can be grown in vivo as grafts to athymic mice, thus allowing ethical analysis of potential adverse effects of environmental toxicants.

Changes in the cellular phenotype and extracellular matrix during progression of estrogen-induced mesenchymal kidney tumors in Syrian hamsters

The cellular origin of estrogen-induced kidney tumors in male Syrian hamsters has been repeatedly the subject of controversy. Several authors have proposed that the tumors arise from proximal tubules, from a combination of tubular and interstitial stromal cells, or solely from interstitial cells. Because of the model character of this tumor for hormone-associated cancer, it was further investigated in this study with respect to morphology, enzyme and intermediate filament pattern, the expression of alpha-smooth muscle actin and the extracellular matrix proteins fibronectin and tenascin. These analyses were carried out with early and late tumors as well as metastases to determine possible changes in expression of biochemical parameters during the development and progression of this neoplasm. The enzyme histochemical and intermediate filament patterns were usually the same as those described previously for proliferative foci and early tumors, i.e. highly elevated activities of glucose-6-phosphate dehydrogenase, adenylate cyclase and alkaline phosphatase, a lack of glucose-6-phosphatase and gamma-glutamyltransferase and coexpression of vimentin and desmin, alpha-smooth muscle actin could not be detected in early lesions. In five of 24 advanced tumors inclusions of kidney tubules were found which showed various degrees of alteration in their morphology and enzyme histochemical pattern, but were often directly connected with tubular segments of normal appearance outside the tumor. Like the normal tubules, the enclosed tubular segments were strongly positive for cytokeratin but never expressed vimentin or desmin. Among the 24 tumors studied, two contained cysts which expressed cytokeratin and sometimes also vimentin but not desmin. The enzyme histochemistry of the cells lining the cysts was similar to that of the surrounding tumor mass, except adenylate cyclase was lacking and alkaline phosphatase was not uniformly distributed. In tumors containing cytokeratin-positive cysts, there often were cytokeratin-positive, vimentin-negative and desmin-negative tumor formations in close contact to these cysts. With the exception of cyst formation, the pattern of metastases were identical to that of the primary tumors. All large tumors and the main component of the metastases expressed vimentin, desmin and fibronectin. Mesothelia surrounding metastatic tumor complexes were positive for vimentin, desmin, alpha-smooth muscle actin, fibronectin, cytokeratin and tenascin. It was concluded from these and previous observations on early stages of tumor development that the estrogen-induced hamster kidney tumor originates from mesenchymal interstitial cells (probably pericytes) which may rarely acquire an epithelial phenotype by metaplastic transformation during tumor progression.

Temporal and spatial factors in diethylstilbestrol-induced squamous metaplasia of the developing human prostate

The effects of exogenous estrogen on the developing human prostate were examined in human fetal prostatic rudiments grown for 1 month as subcapsular renal grafts in athymic male nude mice treated with diethylstilbestrol (DES). Prostatic rudiments grown in untreated (control) hosts exhibited normal ductal morphogenesis, growth, and secretory cytodifferentiation. Squamous metaplasia was observed rarely in controls (2 of 22). Conversely, squamous metaplasia was observed in the prostatic utricle and urethra of all 17 specimens grown in DES-treated hosts. Proximal and distal prostatic ducts exhibited DES-induced squamous metaplasia in 13 and 12 of the specimens, respectively. When present, metaplastic changes were mild in the distal ducts. The distribution and intensity of metaplasia were related to the age of the specimen during the period of DES exposure. In specimens grown in DES-treated hosts to a gestational age equivalent of 16.5 weeks or less, squamous metaplasia was only seen in the prostatic utricle and urethra; however, in specimens grown to a gestational age equivalency of 17 weeks or more, squamous metaplasia was observed in the prostatic ducts as well. The nonuniform distribution of estrogen-induced squamous metaplasia within the developing prostatic ductal system emphasizes a regional and age-dependent susceptibility to exogenous estrogens in proximal ductal areas (near the urethra) as compared with distal ductal regions of the developing human prostate.

Teratogenic effects of clomiphene, tamoxifen, and diethylstilbestrol on the developing human female genital tract

The potential estrogenicity and teratogenicity of triphenylethylene antiestrogens were examined in 54 genital tracts isolated from 4- to 19-week-old human female fetuses and grown for 1 to 2 months in untreated athymic nude mice or host mice treated by subcutaneous pellet with the antiestrogens clomiphene and tamoxifen or the synthetic estrogen diethylstilbestrol (DES). In specimens grown to a gestational age equivalent of 15 weeks or less, the vagina and urogenital sinus were lined by an immature squamous epithelium, which were similar in both drug-treated and untreated specimens. Proliferation and maturation of the squamous vaginal epithelium were observed in specimens treated with clomiphene, tamoxifen, or DES only when grown to a gestational age equivalent of 16 weeks or more. Formation of endometrial and cervical glands proceeded in 87 per cent (13 of 15) of control specimens grown to a gestational age equivalent of 13 weeks or more in untreated hosts. By contrast, age-matched drug-treated specimens contained glands in only 44 per cent (12 of 27) of specimens. In the developing uterine corpus of untreated controls, the uterine mesenchyme segregated into inner (endometrial stroma) and outer (myometrial) layers; whereas in drug-treated specimens, condensation and segregation of the mesenchyme were greatly impaired. The fallopian tube was also affected by clomiphene and tamoxifen (and to a lesser extent by DES) in that its epithelium was hyperplastic and disorganized. The complex mucosal plications characteristic of the fallopian tube were also distorted in drug-treated specimens. These results emphasize the heretofore unrecognized estrogenicity and potential teratogenicity of triphenylethylene antiestrogens on the developing human genital tract and emphasize the need for caution to prevent inadvertent exposure of the developing fetus to these compounds.