Effects of Chronic Dietary Exposure to Phytoestrogen Genistein on Uterine Morphology in Mice

Genistein is naturally occurring in plants and binds to estrogen receptors. Humans are mainly exposed through diet, but the use of supplements is increasing as genistein is claimed to promote health and alleviate menopausal symptoms. We analyzed diverse uterine features in adult mice chronically fed genistein for different times. The luminal epithelium height was increased in females treated with 500 and 1000 ppm at PND 95, and the width of the outer myometrium was increased in females treated with 1000 ppm at PND 65 compared to that in controls. An increase in proliferation was noted in the inner myometrium layer of animals exposed to 300 ppm genistein at PND 185 compared to that in controls. Luminal hyperplasia was greater in the 1000 ppm group at PND 65, 95, and 185, although not statistically different from control. These results indicate that genistein may exert estrogenic activity in the uterus, without persistent harm to the organ.

Effect of neonatal exposure to endosulfan on myometrial adaptation during early pregnancy and labor in rats

Proper myometrial adaptation during gestation is crucial for embryo implantation, pregnancy maintenance and parturition. Previously, we reported that neonatal exposure to endosulfan alters uterine development and induces implantation failures. The present work investigates the effects of endosulfan exposure on myometrial differentiation at the pre-implantation period, and myometrial activation during labor. Newborn female rats were s.c. injected with corn oil (vehicle) or 600 μg/kg/day of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5 and 7. On PND90, the rats were mated to evaluate: i) the myometrial differentiation on gestational day 5 (GD5, pre-implantation period), by assessment myometrial histomorphology, smooth muscle cells (SMCs) proliferation, and expression of proteins involved in myometrial adaptation for embryo implantation (steroid receptors, Wnt7a and Hoxa10); ii) the timing of parturition and myometrial activation during labor by determining the uterine expression of contraction-associated genes (oxytocin receptor, OTXR; prostaglandin F₂α receptor, PTGFR and connexin-43, Cx-43). Endosulfan decreased the thickness of both myometrial layers, with a concomitant decrease in the collagen remodeling. Blood vessels relative area in the interstitial connective tissue between muscle layers was also decreased. Endo600 group showed lower myometrial proliferation in association with a downregulation of Wnt7a and Hoxa10. Although in all females labor occurred on GD23, the exposure to endosulfan altered the timing of parturition, by inducing advancement in the initiation of labor. This alteration was associated with an increased uterine expression of OTXR, PTGFR and Cx-43. In conclusion, neonatal exposure to endosulfan produced long-term effects affecting myometrial adaptation during early pregnancy and labor. These alterations could be associated with the aberrant effects of endosulfan on the implantation process and the timing of parturition.

Identification of a Sensitive Period for Developmental Programming That Increases Risk for Uterine Leiomyoma in Eker Rats

Epidemiological and experimental animal studies have shown that exposure to xenoestrogens during reproductive tract development reprograms target tissues, leading to increased disease risk later in adult life. To understand what defines the critical risk period for this effect, termed developmental programming, the authors assess the sensitivity of the female reproductive tract to developmental programming during various stages of neonatal development. Eker rats, which are predisposed to develop uterine leiomyoma because of a germ-line defect in the tuberous sclerosis complex 2 (Tsc-2) tumor suppressor gene, were exposed to the xenoestrogen diethylstilbestrol (DES) on either postnatal days 3 to 5, 10 to 12, or 17 to 19, 3 important periods of reproductive tract development and differentiation. Developmental programming was observed in both carrier (Tsc-2(Ek/+)) and wild-type (Tsc-2(+/+)) rats exposed to DES at days 3 to 5 and days 10 to 12 but not in rats exposed at days 17 to 19. Developmental programming resulted in increased tumor suppressor gene penetrance in Tsc-2(Ek/+) females relative to vehicle controls. In contrast, DES exposure at days 17 to 19 did not significantly increase the incidence of uterine leiomyoma in carrier females, indicating that the window of susceptibility had closed by this time. Gene expression analysis to determine what defined the susceptible (days 3-5 and days 10-12) versus resistant (days 17-19) periods revealed that in adult myometrium, expression of the estrogen-responsive genes calbindin D(9)K and progesterone receptor had been reprogrammed in females exposed to DES at days 3 to 5 and days 10 to 12 but not in those exposed at days 17 to 19. Reprogramming in response to DES exposure resulted in a hyperresponsiveness to ovarian hormones and could be prevented by ovariectomy prior to sexual maturity. Furthermore, in the neonatal uterus, DES was equally effective at inducing transcription of estrogen-responsive genes during both sensitive and resistant periods, indicating that resistance to developmental programming was not due to an inability of the estrogen receptor to transactivate gene expression. Interestingly, the resistant period coincided with the time at which reproductive tract tissues are exposed to endogenous estrogen, suggesting that target tissues are most vulnerable to developmental programming during the period in which they would normally be maintained in an estrogen-naïve state.

TGFBR1 is required for mouse myometrial development

The smooth muscle layer of the uterus (ie, myometrium) is critical for a successful pregnancy and labor. We have shown that the conditional deletion of TGFβ type 1 receptor (TGFBR1) in the female reproductive tract leads to remarkable smooth muscle defects. This study was aimed at defining the cellular and molecular basis of the myometrial defects. We found that TGFBR1 is required for myometrial configuration and formation during early postnatal uterine development. Despite the well-established role of TGFβ signaling in vascular smooth muscle cell differentiation, the majority of smooth muscle genes were expressed in Tgfbr1 conditional knockout (cKO) uteri at similar levels as controls during postnatal uterine development, coinciding with the presence but abnormal distribution of proteins for select smooth muscle markers. Importantly, the uteri of these mice had impaired synthesis of key extracellular matrix proteins and dysregulated expression of platelet-derived growth factors. Furthermore, platelet-derived growth factors induced the migration of uterine stromal cells from both control and Tgfbr1 cKO mice in vitro. Our results suggest that the myometrial defects in Tgfbr1 cKO mice may not directly arise from an intrinsic deficiency in uterine smooth muscle cell differentiation but are linked to the impaired production of key extracellular matrix components and abnormal uterine cell migration during a critical time window of postnatal uterine development. These findings will potentially aid in the design of novel therapies for reproductive disorders associated with myometrial defects.

The Caenorhabditis elegans T-box factor MLS-1 requires Groucho co-repressor interaction for uterine muscle specification

T-box proteins are conserved transcription factors that play crucial roles in development of all metazoans; and, in humans, mutations affecting T-box genes are associated with a variety of congenital diseases and cancers. Despite the importance of this transcription factor family, very little is known regarding how T-box factors regulate gene expression. The Caenorhabditis elegans genome contains 21 T-box genes, and their characterized functions include cell fate specification in a variety of tissues. The C. elegans Tbx1 sub-family member MLS-1 functions during larval development to specify the fate of non-striated uterine muscles; and, in mls-1 mutants, uterine muscles are transformed to a vulval muscle fate. Here we demonstrate that MLS-1 function depends on binding to the Groucho-family co-repressor UNC-37. MLS-1 interacts with UNC-37 via a conserved eh1 motif, and the MLS-1 eh1 motif is necessary for MLS-1 to specify uterine muscle fate. Moreover, unc-37 loss-of-function produces uterine muscle to vulval muscle fate transformation similar to those observed in mls-1 mutants. Based on these results, we conclude that MLS-1 specifies uterine muscle fate by repressing target gene expression, and this function depends on interaction with UNC-37. Moreover, we suggest that MLS-1 shares a common mechanism for transcriptional repression with related T-box factors in other animal phyla.

Mammalian target of rapamycin is activated in association with myometrial proliferation during pregnancy

The adaptive growth of the uterus during gestation involves gradual changes in cellular phenotypes from the early proliferative to the intermediate synthetic phase of cellular hypertrophy, ending in the final contractile/labour phenotype. The mammalian target of rapamycin (mTOR) signaling pathway regulates cell growth and proliferation in many tissues. We hypothesized that mTOR was a mediator of hormone-initiated myometrial hyperplasia during gestation. The protein expression and phosphorylation levels of mTOR, its upstream regulators [insulin receptor substrate-1, phosphoinositide-3-kinase (PI3K), Akt], and downstream effectors [S6-kinase-1 (S6K1) and eI4FE-binding protein 1 (4EBP1)] were analyzed throughout normal pregnancy in rats. In addition, we used an ovariectomized (OVX) rat model to analyze the modulation of the mTOR pathway and proliferative activity of the uterine myocytes by estradiol alone and in combination with the mTOR-specific inhibitor rapamycin. Our results demonstrate that insulin receptor substrate-1 protein levels and the phosphorylated (activated) forms of PI3K, mTOR, and S6K1 were significantly up-regulated in the rat myometrium during the proliferative phase of pregnancy. Treatment of the OVX rats with estradiol caused a transient increase in IGF-I followed by an up-regulation of the PI3K/mTOR pathway, which became apparent by a cascade of phosphorylation reactions (P-P85, P-Akt, P-mTOR, P-S6K1, and P-4EBP1). Rapamycin blocked activation of P-mTOR, P-S6K1, and P-4EBP1 proteins and significantly reduced the number of proliferating cells in the myometrium of OVX rats. Our in vivo data demonstrate that estradiol was able to activate the PI3K/mTOR signaling pathway in uterine myocytes and suggest that this activation is responsible for the induction of myometrial hyperplasia during early gestation.

Insulin-like growth factors and their binding proteins define specific phases of myometrial differentiation during pregnancy in the rat

While the insulin-like growth factor (IGF) system is known to regulate uterine function during the estrous cycle, there are limited data on its role in myometrial growth and development during pregnancy. To address this issue, we defined the expression of the Igf hormones (1 and 2), their binding proteins (Igfbp 1-6), and Igf1r receptor genes in pregnant, laboring, and postpartum rat myometrium by real-time PCR. IGF family genes were differentially expressed throughout gestation. Igf1 and Igfbp1 mRNA levels were upregulated during proliferative phase (Days 6-12) of rat gestation. Igfbp3 gene expression also was elevated in proliferating smooth muscle cells (SMCs) and was highest at the time of transition between proliferative and synthetic phases (Days 12-15). Igfbp6 gene expression profile paralleled plasma progesterone (P4) concentrations, peaking during the synthetic phase (Days 17-19) and decreasing thereafter. Administration of P4 at late pregnancy (starting from Day 20) to maintain elevated plasma P4 concentrations blocked the onset of labor and prevented the fall in Igfbp6 mRNA levels. In contrast, the treatment of pregnant rats with the P4 receptor antagonist RU486 on Day 19 induced preterm labor and the premature decrease of Igfbp6 gene expression. Igfbp2 gene expression was transiently upregulated during the contractile phase of gestation (Days 21-23) solely in the gravid horn of unilaterally pregnant rats, but it was not affected in P4- or RU486-treated animals, supporting a role for mechanical stretch imposed by the growing fetuses. Igfbp5 gene was induced during postpartum involution. Our results suggest the importance of the IGF system in phenotypic and functional changes of myometrial SMCs throughout gestation in preparation for labor.

Conditional deletion of beta-catenin in the mesenchyme of the developing mouse uterus results in a switch to adipogenesis in the myometrium

Precise cell fate decisions during differentiation of uterine tissues from the embryonic Müllerian duct are critical for normal fertility. Wnt-7a, a member of the Wnt family of secreted signaling molecules that can signal through a canonical beta-catenin pathway, is necessary for the correct differentiation of both anterior/posterior and radial axes of the uterus. In order to investigate the role of beta-catenin directly in mouse uterine development, we have generated mice that are deficient in beta-catenin expression in the embryonic Müllerian duct. We have found that conditional deletion of beta-catenin in the Müllerian duct mesenchyme before postnatal differentiation of the uterine layers results in a phenotype that is distinct from the phenotype observed by deletion of Wnt-7a. Shortly after birth, the uteri of the conditional mutants appear smaller and less organized. The uteri of adult conditional beta-catenin mutants are grossly deficient in smooth muscle of the myometrium, which has been replaced by adipose, a phenotype resembling human lipoleiomyoma. We also show that the adipocytes in the uteri of mice conditionally deleted for beta-catenin are derived from Müllerian inhibiting substance type II receptor-expressing cells suggesting that they share a common origin with the uterine smooth muscle cells. These results describe the first molecular evidence linking disruption of beta-catenin expression in mesenchymal cells with a switch from myogenesis to adipogenesis in vivo.

Growth dynamics of human leiomyoma cells and inhibitory effects of the peroxisome proliferator-activated receptor-γ ligand, pioglitazone

Uterine leiomyomas (fibroids) are the most frequent tumour of the female reproductive tract and are the primary cause of hysterectomies in women worldwide. Effective treatment options are few. In a search for alternative treatments, we have established primary cultures of human leiomyoma cells and adjacent myometrial tissues, and documented their growth dynamics in response to estradiol (E2) and pioglitazone (PIO), a peroxisome proliferation-activated receptor-gamma (PPARgamma) ligand, currently in clinical use for type II diabetes mellitus. Human uterine primary cell cultures display morphology and desmin content consistent with their smooth muscle origin. Surprisingly, leiomyoma cells exhibited slower proliferation patterns relative to matched myometrial cells, both in the absence and presence of E2, suggesting that tumour genesis may not be because of increased growth potential but could be related to suppression of growth-inhibiting factors in vivo. PIO significantly inhibited the cell proliferation of both myometrial and leiomyoma cells in a dose-dependent manner. Our results suggest the possibility of using PPARgamma ligands, such as PIO, as therapeutic agents for the conservative management of uterine fibroids.

Ovarian regulation of endometrial gland morphogenesis and activin-follistatin system in the neonatal ovine uterus

Postnatal development of the ovine uterus between birth and Postnatal Day (PND) 56 involves differentiation of the endometrial glandular epithelium from the luminal epithelium followed by tubulogenesis and branching morphogenesis. Previous results indicated that ovariectomy of ewes at birth did not affect uterine growth or initial stages of endometrial gland genesis on PND 14 but did affect uterine growth after PND 28. Available evidence from a number of species supports the hypothesis that the ovary does not affect endometrial gland morphogenesis in the postnatal uterus. To test this hypothesis in our sheep model, ewes were assigned at birth to a sham surgery as a control or bilateral ovariectomy (OVX) on PND 7. Uteri were removed and weighed on PND 56. Ovariectomy did not affect circulating levels of estradiol-17beta. Uterine weight was 52% lower in OVX ewes. Histomorphological analyses indicated that the thickness of the endometrium and myometrium, total number of endometrial glands, and endometrial gland density in the stratum spongiosum stroma was reduced in uteri of OVX ewes. In contrast, the number of superficial ductal gland invaginations and gland density in the stratum compactum stroma was not affected by ovariectomy. The uteri of OVX ewes contained lower levels of betaA subunit, activin receptor (ActR) type IA, ActRIB, and follistatin protein expression but higher levels of betaB subunit. In the neonatal ovary, follistatin, inhibin alpha subunit, betaA subunit, and betaB subunit were expressed in antral follicles between PNDs 0 and 56. These results led to rejection of the hypothesis that the ovary does not influence endometrial adenogenesis. Rather, the ovary and, thus, an ovarian-derived factor regulates, in part, the coiling and branching morphogenetic stage of endometrial gland development after PND 14 and expression of specific components of the activin-follistatin system in the neonatal ovine uterus that appear to be important for that critical process.

The activin-follistatin system in the neonatal ovine uterus

Uterine gland development or adenogenesis in the neonatal ovine uterus involves budding and tubulogenesis followed by coiling and branching morphogenesis of the glandular epithelium (GE) from the luminal epithelium (LE) between birth (Postnatal Day [PND] 0) and PND 56. Activins, which are members of the transforming growth factor beta superfamily, and follistatin, an inhibitor of activins, regulate epithelial branching morphogenesis in other organs. The objective of the present study was to determine effects of postnatal age on expression of follistatin, inhibin alpha subunit, betaA subunit, betaB subunit, activin receptor (ActR) type IA, ActRIB, and ActRII in the developing ovine uterus. Ewes were ovariohysterectomized on PND 0, 7, 14, 21, 28, 35, 42, 49, or 56. The uterus was analyzed by in situ hybridization and immunohistochemistry. Neither inhibin alpha subunit mRNA or protein was detected in the neonatal uterus. Expression of betaA and betaB subunits was detected predominantly in the endometrial LE and GE and myometrium between PND 0 and PND 56. In all uterine cell types, ActRIA, ActRIB, and ActRII were expressed, with the highest levels observed in the endometrial LE and GE and myometrium. Between PND 0 and PND 14, follistatin was detected in all uterine cell types. However, between PND 21 and PND 56, follistatin was only detected in the stroma and myometrium and not in the developing GE. Collectively, the present results indicate that components of the activin-follistatin system are expressed in the developing neonatal ovine uterus and are potential regulators of endometrial gland morphogenesis.

Expression of estrogen receptor alpha and beta in myometrium of premenopausal and postmenopausal women

Although a clear role for estrogen receptor (ER) alpha has been established, the contribution of ERbeta in estrogen-dependent development, growth and functions of the myometrium is not understood. As a first step towards understanding the role of ERbeta, we have examined the expression of ERalpha and ERbeta in the human myometrium. With competitive RT-PCR assays, the level of ERbeta mRNA was 10-200 times lower than that of ERalpha mRNA in both premenopausal and postmenopausal myometrium. In premenopausal myometrium, the expression pattern of ERbeta mRNA during the menstrual cycle was similar to that of ERalpha mRNA, with highest levels in peri-ovulatory phase. In postmenopausal myometrium, ERbeta mRNA was significantly higher than it was in premenopausal myometrium, while the level of ERalpha mRNA was lower. The net result was a change in the ratio of ERbeta to ERalpha mRNA expression. The ratio changed from 0.6-1.5 in premenopausal to 2.5-7.6 in postmenopausal myometrium. In premenopausal women, the gonadotropin releasing hormone analogue, leuprorelin acetate, elicited a decrease in ERalpha and an increase in ERbeta mRNA expression to cause a postmenopausal receptor phenotype. Estradiol, on the other hand, reversed ERalpha and ERbeta mRNA expression and their ratio in postmenopausal myometrium to those of premenopausal myometrium. Immunohistochemical staining and Western blot analysis of ERalpha and ERbeta with semiquantitative analysis showed good agreement between mRNA and protein levels. The data indicate that coordinated expression of ERalpha and ERbeta might be necessary for normal estrogen action in myometrium. Furthermore, estrogen appears a dominant regulator of both receptors in the myometrium.

Effects of GnRH analogues, 'add-back' steroid therapy, antiestrogen and antiprogestins on leiomyoma and myometrial smooth muscle cell growth and transforming growth factor-beta expression

The objective of this study was to elucidate the biological significance of GnRH and antiprogestins and antiestrogen in leiomyoma and their interactions with ovarian steroid 'add-back' therapy. Leiomyoma and myometrial smooth muscle cells (LSMC and MSMC) were isolated and exposed to GnRH agonist (leuprolide acetate, LA), 17beta-estradiol (E2), medroxyprogesterone acetate (MPA), GnRH antagonist (Antide), estrogen antagonist, ICI182780 (Fulvestrant) and progesterone antagonists RU486 (Mifepristone) and ZK98299 (Onapristone) and combinations thereof. The rate of DNA synthesis, cell proliferation and transforming growth factor-beta (TGF-beta) expression were then determined. In both cell types, we found that in a dose-dependent manner, LA inhibited, whereas E2, MPA and the combination of E2 + MPA stimulated, the rate of DNA synthesis in these cells. Antide reversed the inhibitory effect of LA, while LA partly inhibited the stimulatory effect of the steroids. In addition, RU486, ICI182780 and ZK98299 at 0.1 micro mol/l or higher doses inhibited the rate of DNA synthesis and partly reversed the effects of E2 and/or MPA. We also found that LSMC expressed elevated levels of TGF-beta1 compared with MSMC. In both cell types, the effects of LA, E2, MPA, RU, ZK and ICI and combinations thereof on TGF-beta1 production were reflective of their effects on DNA synthesis. In line with this, TGF-beta1 was found to stimulate DNA synthesis and the E2-, TGF-beta1- or E2 + TGF-beta1-induced DNA synthesis was found to be inhibited by TGF-beta1 neutralizing antibodies and/or LA. In conclusion, the results provide further evidence that GnRH agonist- and RU486-induced leiomyoma regression is mediated in part through an interactive mechanism that results in altered cell growth and suppression of TGF-beta production.

Altered hormonal responsiveness of proliferation and apoptosis during myometrial maturation and the development of uterine leiomyomas in the rat

Uterine leiomyomas are responsive to the ovarian steroids, estrogen and progesterone; however, a mechanistic understanding of the role of these hormones in the development of this common gynecologic lesion remains to be elucidated. We have used the Eker rat uterine leiomyoma model to investigate how ovarian hormones regulate or promote the growth of these tumors. Proliferative and apoptotic rates were quantitated in normal uterine tissues and leiomyomas in response to endogenous ovarian steroids. In 2- to 4-mo-old animals, cell proliferation in the normal uterus corresponded with high serum levels of steroid hormones during the estrous cycle, and apoptosis occurred in the rat uterus in all cell types following sharp, cyclical declines in serum hormone levels. It is interesting that the responsiveness of uterine mesenchymal cells changed between 4 and 6 mo of age, with significant decreases in both proliferative and apoptotic rates observed in myometrial and stromal cells of cycling animals. Leiomyomas displayed much higher levels of proliferation than did age-matched myometrium; however, their apoptotic index was significantly decreased in comparison with normal myometrium. This disregulation between proliferative and apoptotic responses, which were tightly regulated during ovarian cycling in the normal myometrium, may contribute to the disruption of tissue homeostasis and underlie neoplastic growth of these tumors.

Developmental and gestational changes of phosphoethanolamine and taurine in rat brain, striated and smooth muscle

Concentrations of taurine and phosphoethanolamine in rat smooth (intestinal and uterine), skeletal and cardiac muscle, and brain have been determined, using high-performance liquid chromatography (HPLC), to examine possible interrelationships in their tissue content. Concentrations were determined in fetal and neonatal samples, as well as in adult tissue, to investigate whether phosphoethanolamine and taurine levels are influenced by developmental state. The effect of gestational state was also studied. A marked decrease in cerebral phosphoethanolamine concentration during development was found together with a concomitant decrease in striated muscle but not in the two smooth muscles studied. A rise in uterine phosphoethanolamine during the early postpartum period confirmed previous NMR data. This occurred only in the uterus, suggesting it is specific to the process of involution within the myometrium. Taurine concentrations showed no consistent pattern of change with postnatal development. In adult animals, the highest levels of taurine were found in cardiac muscle. Pregnancy was associated with a fall in taurine concentration in all tissues, suggesting an influence of steroid hormones. As taurine is cotransported with Na+ in many systems it may be related to the increased water retention seen in pregnancy. It is concluded that marked changes in phosphoethanolamine and taurine levels occur during development and gestation, but that the changes are not interdependent, i.e., the changes are tissue specific.

Neonatal age and period of estrogen exposure affect porcine uterine growth, morphogenesis, and protein synthesis

To determine whether neonatal age and estrogen exposure affect uterine growth, morphogenesis, and protein synthesis, crossbred gilts were randomly assigned at birth (Day 0) to receive either corn oil vehicle (CO) or estradiol-17 beta valerate (EV; 50 micrograms/kg BW/day). Gilts were treated for 7 days, chosen to coincide with specific periods of uterine development, prior to hysterectomy on Day 7, 14, or 49. Uteri were weighed, and tissues were fixed for histology or explanted with L-4,5-[3H]leucine (3H-leu) for 24 h. Endometrial and myometrial thicknesses were measured in uterine wall cross sections. Radiolabeled proteins produced by uterine wall tissues from 3H-leu and released into explant medium were identified by fluorography of two-dimensional SDS-PAGE gels. Proteins for which fluorographic spot intensities were consistently affected by age and/or treatment were excised from gels, and associated radioactivity was quantified. Normal growth and histogenesis were observed in uteri from CO-treated gilts. Exposure to EV increased (p < 0.01) uterine wet weight on all days examined, although effects were most pronounced on Day 49 (day x treatment, p < 0.01). Histologically, uteri of EV-treated gilts exhibited precocious or altered patterns of development of endometrial glands and folds. Endometrial thickness was greater (p < 0.01) in EV-treated gilts, and response was most pronounced on Day 49 (day x treatment, p < 0.01). Treatment with EV increased (p < 0.01) myometrial thickness on Day 49 only. Twenty-five uterine proteins were identified to be affected consistently by neonatal age, EV, or both. Production of four of these proteins was affected by age alone, while six were affected exclusively by treatment with EV alone, and 15 were affected differentially by both age and EV. Treatment with EV affected production of three of these 25 proteins on Day 7, 8 of 25 on Day 14, and 14 of 25 on Day 49. Results indicate that uterine growth and development of the porcine uterine wall during early neonatal life are accompanied by predictable alterations in patterns of uterine protein synthesis. Data also demonstrate that the neonatal porcine uterus is estrogen-sensitive and that both physical and biochemical responses of uterine tissues to estrogen vary with period of exposure. It is suggested that EV may be useful as a tool with which to induce developmental lesions in neonatal porcine uterine tissues.(ABSTRACT TRUNCATED AT 400 WORDS)

Histologic, morphometric, and immunocytochemical analysis of myometrial development in rats and mice: I. Normal development

Myometrial development from the prenatal to adult period was examined in rats and mice 1) by histologic and immunocytochemical methods with anti-actin, -vimentin, and -laminin to assess cytodifferentiation of smooth muscle and fibroblastic cells; and 2) by morphometric procedures to assess quantitatively the expression of cellular orientation in the emerging inner circular myometrial layer. Uterine mesenchymal cells initially were uniformly vimentin-positive, undifferentiated, and randomly oriented during the late fetal period. By the early neonatal period, three mesenchymal layers became recognizable histologically, the middle one of which (prospective circular myometrium) developed distinct circular orientation and differentiated into a layer composed of actin-positive smooth muscle cells. The cells of the inner mesenchymal layer initially exhibited radial orientation. By 10 days postpartum, the outer longitudinal mesenchymal layer differentiated into bundles of smooth muscle cells representing the longitudinal myometrium. The inner mesenchymal layer remained vimentin-positive and differentiated into the randomly ordered endometrial stroma. The cells of the middle and outer mesenchymal layers that were destined to form myometrium initially expressed vimentin throughout and then coexpressed vimentin and actin, but with time vimentin staining disappeared in the maturing smooth muscle cells as they expressed actin.

Histologic, morphometric, and immunocytochemical analysis of myometrial development in rats and mice: II. Effects of DES on development

The effects of diethylstilbestrol (DES) treatment on myometrial development from the prenatal to adult period were examined in rats and mice by histologic and immunocytochemical methods using anti-actin, -vimentin, and -laminin to assess cytodifferentiation of smooth muscle and fibroblastic cells, and by morphometric procedures to assess quantitatively the effect of DES on the expression of cellular orientation in the emerging inner circular myometrial layer. Neonatal rats and mice were treated with DES from day 0 (day of birth) to day 2 with dosages known to perturb myometrial development. Neonatal treatment with DES increased the degree of circular orientation within the uterine mesenchyme, an effect detectable following as little as 24 hr of DES treatment. This effect on spatial organization of the mesenchyme was followed by an increase in the thickness of the actin-positive middle layer (prospective circular myometrium) of uterine mesenchyme during days 3-15; from day 15 onward, however, the circular myometrial layer began to fragment into irregular bundles of smooth muscle, and the longitudinal myometrial layer became thinner and more irregularly organized than controls. Vimentin localization in rats treated with DES neonatally was more intense than in controls within the circularly orientated uterine mesenchyme at 5 days. By 60 days the circular and longitudinal myometrial layers of DES-treated animals showed strands and bundles of vimentin-positive cells, which were not present in controls. Both rats and mice show comparable effects of DES treatment.

Role of uterine epithelium in the development of myometrial smooth muscle cells

To study the role of epithelial-mesenchymal interactions in myometrial development, uteri from neonatal Balb/c mice 1 to 60 days postpartum were utilized. Intact (untrypsinized) uteri, trypsinized but unseparated uteri, homotypic uterine tissue recombinants (separated-recombined), or uterine mesenchyme alone were grafted beneath the renal capsule of syngeneic female hosts and grown for 1 mo. Uterine mesenchyme from 1-day mice grafted alone produced small amounts of smooth muscle, most of which was associated with vasculature, whereas uterine mesenchyme from older donors possessing a rudimentary myometrium at the time of grafting formed intermediate amounts of myometrium (actin-positive smooth muscle bundles). In contrast, all specimens containing epithelium (intact, trypsinized, and separated-recombined) developed large amounts of myometrium. Uterine epithelia from neonatal through adult stages were equally effective in permissively inducing myometrial development in 1-day uterine mesenchyme. From these data, it is apparent that uterine epithelium plays an important promotional role in the differentiation and possibly the spatial organization of the myometrium.

[Development of the uterine microcirculatory bed in postnatal ontogeny]

Age peculiarities of common structure of the microcirculatory pathways, specific volumes and amount of microvessels, zonal parameters of pericapillary microcirculation of metabolites, glycosamine glycans and glycoproteins contents, phosphatase and ATPase activity, collagen and elastic fibers of the microcirculatory bed vessels have been studied in 190 unchanged uteri, beginning from 36-week-old fetuses up to 35 years of age. The microcirculatory bed of myometrium during the period of postnatal ontogenesis investigated possesses a polymer-homonomous structural organization; its base make myoangiomas, including the terminal arteriole with precapillaries and collecting venule, that run from it. Similar structure of the myometrium microcirculatory pathways is already observed in fetuses of late antenatal period. In endometrium formed glanduloangionomas are revealed in the prepubertal age. Increase in glycosamine glycans contents is stated in the microvessel walls and in the uterine stroma during the process of its development. Compensatory-adaptive changes in the uterine microcirculatory bed are described during the newborn period up to the puberty. Functionally mature structures of the microcirculatory pathways in the submucosal and vascular layers of myometrium, endometrium and in the cervix uteri are found to be formed earlier than in other areas of the organ.