Clonality of urogenital organs as determined by analysis of chimeric mice

Mechanisms of Regeneration and Fibrosis in the Endometrium

The uterine lining (endometrium) regenerates repeatedly over the life span as part of its normal physiology. Substantial portions of the endometrium are shed during childbirth (parturition) and, in some species, menstruation, but the tissue is rapidly rebuilt without scarring, rendering it a powerful model of regeneration in mammals. Nonetheless, following some assaults, including medical procedures and infections, the endometrium fails to regenerate and instead forms scars that may interfere with normal endometrial function and contribute to infertility. Thus, the endometrium provides an exceptional platform to answer a central question of regenerative medicine: Why do some systems regenerate while others scar? Here, we review our current understanding of diverse endometrial disruption events in humans, nonhuman primates, and rodents, and the associated mechanisms of regenerative success and failure. Elucidating the determinants of these disparate repair processes promises insights into fundamental mechanisms of mammalian regeneration with substantial implications for reproductive health.

Effects of 2,4-dichlorophenoxyacetic acid on the ventral prostate of rats during the peri-pubertal, pubertal and adult stage

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is used on a wide variety of terrestrial and aquatic broadleaf weeds. 2,4-D has been shown to produce a wide range of adverse effects on animal and human health. The aim of the current study was to evaluate the effects of pre- and postnatal exposure to 2,4-D on rat ventral prostate (VP). Pregnant rats were exposed daily to oral doses of 70 mg/kg/day of 2,4-D from 16 days of gestation up to 23 days after delivery. Then, the treated groups (n = 8) were fed with a 2,4-D added diet until sacrificed by decapitation on postnatal day (PND) 45, 60, or 90. Morphometric studies were performed and androgen receptor (AR) protein levels in the VP were determined. AR, insulin-like growth factor-I (IGF-1) and insulin-like growth factor-I receptor (IGF-1R) mRNA expression in the VP along with testosterone (T), dihydroxytestosterone (DHT), growth hormone (GH) and IGF-1 serum levels were also determined to ascertain whether these parameters were differentially affected. Results of this study showed that 2,4-D exposure during gestation and until adulthood altered development of the prostate gland in male rats, delaying it at early ages while increasing its size in adults, indicate that 2,4-D could behave as endocrine disruptors (EDs).

Fluorescent transgenic mice suitable for multi-color aggregation chimera studies

We recently reported a novel method of mouse transgenesis called Pronuclear Injection-based Targeted Transgenisis (PITT) using which a series of fluorescent transgenic (Tg) mice lines were generated. These lines, unlike those generated using conventional random integration methods, express the transgenes faithfully and reproducibly generation after generation. Because of this superior nature, these lines are ideal for the generation of multi-colored aggregation chimeras that can be used to study cell-cell interactions and lineage analyses in living embryos/organs, where the transgenes can be detected and the clonal origin of a given cell population easily traced by its distinct fluorescence. In this study, to verify if Tg fluorescent mice generated through PITT were suitable for such applications, we sought to generate chimeric blastocysts and chimeric-Tg mice by aggregating two- or three-colored 8-cell embryos. Our analyses using these models led to the following observations. First, we noticed that cell mixing was infrequent during the stages of morula to early blastocyst. Second, chimeric fetuses obtained after aggregation of the two-colored 8-cell embryos exhibited uniform cell mixing. And third, in the organs of adult chimeric mice, the mode of cell distribution could be either clonal or polyclonal, as previously pointed out by others. Implications of our novel and improved Tg-chimeric mice approach for clonal cell lineage and developmental studies are discussed.

Comparative developmental biology of the uterus: insights into mechanisms and developmental disruption

The uterus is an essential organ for reproduction in mammals that derives from the Müllerian duct. Despite the importance of the uterus for the fertility and health of women and their offspring, relatively little is known about the hormonal, cellular and molecular mechanisms that regulate development of the Müllerian duct and uterus. This review aims to summarize the hormonal, cellular and molecular mechanisms and pathways governing development of the Müllerian duct and uterus as well as highlight developmental programming effects of endocrine disruptor compounds. Organogenesis, morphogenesis, and functional differentiation of the uterus are complex, multifactorial processes. Disruption of uterine development in the fetus and neonate by genetic defects and exposure to endocrine disruptor compounds can cause infertility and cancer in the adult and their offspring via developmental programming. Clear conservation of some factors and pathways are observed between species; therefore, comparative biology is useful to identify candidate genes and pathways underlying congenital abnormalities in humans.

Cytokine and endocrine signaling in prostate cancer

Prostate epithelial and stromal cells develop paracrine interactions, which may be responsible for the occurrence and progression of prostate pathologies. Strikingly, stromal cells exhibit pleiotropic effects on epithelial cell growth, ranging from stimulation to inhibition. Steroid hormone receptors are considered ligand-activated transcriptional factors. Moreover, it has been suggested that the human androgen receptor can also be activated in the absence of surrounding ligands such as growth factors and cytokines. Strong evidence suggests that cytokines may play an important role in ligand-independent activation of androgen receptor in prostate cancer cells. In our view, one of the most striking finding in the prostate cancer development process is the relationship between carcinogenesis and secretion of cytokines.

Adult stem cells in the endometrium

Rare cells with adult stem cell activity were recently discovered in human endometrium. Endometrial stem/progenitor cell candidates include epithelial, mesenchymal and endothelial cells, and all may contribute to the rapid endometrial regeneration following menstruation, rather than a single candidate. Endometrial mesenchymal stem-like cells (eMSC) are prospectively isolated as CD146(+)PDGF-Rβ(+) cells and are found in both basalis and functionalis as perivascular cells. Epithelial progenitor cells are detected in colony forming unit assays but their identity awaits elucidation. They are postulated to reside in the basalis in gland bases. Endometrial stem/progenitor cells may be derived from endogenous stem cells, but emerging evidence suggests a bone marrow contribution. Endometrial endothelial progenitor cells are detected as side population cells, which express several endothelial cell markers and differentiate into endometrial glandular epithelial, stromal and endothelial cells. Investigating endometrial stem cell biology is crucial to understanding normal endometrial physiology and to determine their roles in endometrial proliferative diseases. The nature of endometriosis suggests that initiation of ectopic endometrial lesions involves endometrial stem/progenitor cells, a notion compatible with Sampson's retrograde menstruation theory and supported by the demonstration of eMSC in menstrual blood. Evidence of cancer stem cells (CSC) in endometrial cancer indicates that new avenues for developing therapeutic options targeting CSC may become available. We provide an overview of the accumulating evidence for endometrial stem/progenitor cells and their possible roles in endometrial proliferative disorders, and discuss the unresolved issues.

Reepithelialization of the uterine surface arises from endometrial glands: evidence from a functional mouse model of breakdown and repair

The human endometrium is highly regenerative undergoing monthly cycles of growth and regression. Endometrial repair after menses is a critical component of the cycle; however, little is understood about the mechanisms behind this rapid process. Adult stem/progenitor cells identified in human and mouse endometrium may be responsible for its remarkable regenerative capacity; however, a functional role for stem/progenitor cells in menstruation is yet to be established. This study aimed to identify label retaining cells as candidate epithelial stem or progenitor cells involved in the rapid reepithelization of the uterine surface in our functional mouse model of endometrial breakdown and repair. Adult mice were pulse labeled with bromodeoxyuridine before endometrial breakdown and repair was induced. Throughout endometrial breakdown and repair, very rapid dilution of bromodeoxyuridine label was observed in the luminal epithelium, whereas label within the glandular epithelium remained constant. Importantly, glandular epithelial cells were shown to proliferate selectively in response to endometrial repair, and the majority strongly expressed estrogen receptor-alpha at this time. This is the first study to demonstrate a functionally diverse response during endometrial repair from the anatomically connected luminal and glandular epithelium and highlights the likelihood that the endometrial glands are the residence of epithelial progenitor cells contributing to reepithelialization of the uterine surface after menses.

Uterine stem cells: what is the evidence?

The mucosal lining (endometrium) of the human uterus undergoes cyclical processes of regeneration, differentiation and shedding as part of the menstrual cycle. Endometrial regeneration also follows parturition, almost complete resection and in post-menopausal women taking estrogen replacement therapy. In non-menstruating species, there are cycles of endometrial growth and apoptosis rather than physical shedding. The concept that endometrial stem/progenitor cells are responsible for the remarkable regenerative capacity of endometrium was proposed many years ago. However, attempts to isolate, characterize and locate endometrial stem cells have only been undertaken in the last few years as experimental approaches to identify adult stem/progenitor cells in other tissues have been developed. Adult stem cells are defined by their functional properties rather than by marker expression. Evidence for the existence of adult stem/progenitor cells in human and mouse endometrium is now emerging because functional stem cell assays are being applied to uterine cells and tissues. These fundamental studies on endometrial stem/progenitor cells will provide new insights into the pathophysiology of various gynaecological disorders associated with abnormal endometrial proliferation, including endometrial cancer, endometrial hyperplasia, endometriosis and adenomyosis.

The road to maleness: from testis to Wolffian duct

The establishment of the male internal reproductive system involves two crucial events: the formation of the testis and the maintenance and differentiation of the Wolffian duct. Testis formation, particularly the specification of Sertoli cell and Leydig cell lineages, is controlled strictly by genetic components initiated by the testis-determining gene SRY (sex-determining region of the Y chromosome). Conversely, Wolffian duct differentiation is not directly mediated via the composition of the sex chromosome or SRY; instead, it relies on androgens derived from the Leydig cells. Leydig cells do not express SRY, indicating that a crosstalk must be present between the SRY-positive Sertoli and Leydig cells to ensure normal androgen production. Recent advancement of genetic and genomic approaches has unveiled the molecular pathways for differentiation of Sertoli cells and Leydig cells as well as development of the Wolffian duct.

Comparative developmental biology of the mammalian uterus

The uterus is an essential organ for reproduction in mammals. Despite the importance of the uterus for the fertility and health of women and their offspring, relatively little is known about the hormonal, cellular, and molecular mechanisms that regulate development of the uterus in either the fetus or neonate. Disruption of uterine development in the fetus and neonate by genetic defects or exposure to endocrine disruptors can program the function of the uterus in the adult and lead to infertility, cancer, and even death. The intent of this chapter is to review the current knowledge of regulatory factors and pathways governing prenatal organogenesis and postnatal morphogenesis of the uterus in mammals, with a particular focus on laboratory and domestic animals. Prenatal organogenesis, postnatal morphogenesis, and adult functional differentiation of the uterus are complex, multifactorial processes. Although conservation of some factors and pathways are observed between species, it is clear that mutation of candidate genes in the mouse does not always recapitulate the same defects observed in the human. Therefore, comparative biology of the mechanisms regulating uterine development in other species may be useful to identify candidate genes and pathways to understand congenital abnormalities in humans. This knowledge is necessary to develop rational therapies to prevent and treat infertility and to enhance fertility in humans and domestic animals.

Wnt7a Is a Suppressor of Cell Death in the Female Reproductive Tract and Is Required for Postnatal and Estrogen-Mediated Growth1

The murine female reproductive tract is undifferentiated at birth and undergoes pronounced growth and cytodifferentiation during postnatal life. Postnatal reproductive tract development proceeds in the absence of high levels of circulating estrogens and is disrupted by precocious exposure to estrogens. The WNT gene family is critical in guiding the epithelial-mesenchymal interactions that direct postnatal uterine development. We have previously described a role for Wnt7a in controlling morphogenesis in the uterus. In addition to patterning defects, Wnt7a mutant uteri are atrophic in adults and do not show robust postnatal growth. In the present study, we examine immature female Wnt7a mutant and wild-type uteri to assess the cellular processes that underlie this failure in postnatal uterine growth. Levels of proliferation are higher in wild-type versus Wnt7a mutant uteri. Exposure to the potent estrogen-agonist diethylstilbestrol (DES) leads to an increase in cell proliferation in the uterus in wild-type as well as in mutant uteri, indicating that Wnt7a is not required in mediating cell proliferation. In contrast, we observe that Wnt7a mutant uteri display high levels of cell death in response to DES, whereas wild-type uteri display almost no cell death, revealing that Wnt7a plays a key role as a cell death suppressor. The expression pattern of other key regulatory genes that guide uterine development, including estrogen receptor (alpha), Hox, and other WNT genes, reveals either abnormal spatial distribution of transcripts or abnormal regulation in response to DES exposure. Taken together, the results of the present study demonstrate that Wnt7a coordinates a variety of cell and developmental pathways that guide postnatal uterine growth and hormonal responses and that disruption of these pathways leads to aberrant cell death.

Wnt5a is required for proper epithelial-mesenchymal interactions in the uterus

Epithelial-mesenchymal interactions play a crucial role in the correct patterning of the mammalian female reproductive tract (FRT). Three members of the Wnt family of growth factors are expressed at high levels in the developing FRT in the mouse embryo. The expression of Wnt genes is maintained in the adult FRT, although levels fluctuate during estrous. Wnt4 is required for Müllerian duct initiation, whereas Wnt7a is required for subsequent differentiation. In this study, we show that Wnt5a is required for posterior growth of the FRT. We further demonstrate that the mutant FRT has the potential to form the posterior compartments of the FRT using grafting techniques. Postnatally, Wnt5aplays a crucial role in the generation of uterine glands and is required for cellular and molecular responses to exogenous estrogens. Finally, we show that Wnt5a participates in a regulatory loop with other FRT patterning genes including Wnt7a, Hoxa10 and Hoxa11. Data presented provide a mechanistic basis for how uterine stroma mediates both developmental and estrogen-mediated changes in the epithelium and demonstrates that Wnt5a is a key component in this process. The similarities of the Wnt5a and Wnt7a mutant FRT phenotypes to those described for the Hoxa11 and Hoxa13 mutant FRT phenotypes reveal a mechanism whereby Wnt and Hox genes cooperate to pattern the FRT along the anteroposterior axis.

Mouse urogenital development: a practical approach

A detailed knowledge of the developmental anatomy of the embryonic mouse urogenital tract is required to recognize mutant urogenital phenotypes in transgenic and knock-out mice. Accordingly, the purpose of this article is to review urogenital development in the mouse embryo and to give an illustrated methodological protocol for the dissection of urogenital organ rudiments at 12-13 days of gestation (E12-13) to isolate the urogenital ridge and at E16 to isolate the seminal vesicle, Müllerian duct, Wolffian duct, and prostatic rudiment, the urogenital sinus (UGS). The UGS can be cultured and, in the presence of testosterone, prostatic buds form in vitro. Because of the importance of mesenchymal-epithelial interactions in urogenital development, methods for the isolation of epithelium and mesenchyme from the embryonic urogenital sinus are also described. Urogenital sinus mesenchyme (UGM) and urogenital sinus epithelium (UGE) can be used to construct tissue recombinants that can either be grown in vitro or grafted in vivo for the study of epithelial-mesenchymal interactions in prostatic development.

The BMP family member Gdf7 is required for seminal vesicle growth, branching morphogenesis, and cytodifferentiation

Epithelial-mesenchymal interactions play an important role in the development of many different organs and tissues. The secretory glands of the male reproductive system, including the prostate and seminal vesicles, are derived from epithelial precursors. Signals from the underlying mesenchyme are required for normal growth, branching, and differentiation of the seminal vesicle epithelium. Here, we show that a member of the BMP family, Gdf7, is required for normal seminal vesicle development. Expression and tissue recombination experiments suggest that Gdf7 is a mesenchymal signal that acts in a paracrine fashion to control the differentiation of the seminal vesicle epithelium.