Effect of sex steroids on rat endometrial epithelium and stroma cultured separately

Glycogen in the uterus and fallopian tubes is an important source of glucose during early pregnancy†

Pregnancy loss is common during the peri-implantation period in mammals when glucose is required for both embryonic development and decidualization of the endometrium. As the uterus cannot synthesize glucose, all glucose must come directly from maternal circulation as needed or transiently stored as the macromolecule glycogen. Glycogen acts as a glucose reservoir, storing up to 55 000 glucose moieties per molecule. Endometrial glycogen concentrations are correlated with fertility in humans, indicating that glycogen is an essential source of glucose during early pregnancy. In humans and primates, endometrial glycogen concentrations peak during the luteal phase due to progesterone. In contrast, in rats and mink, estradiol triggers an accumulation of uterine glycogen during proestrus and estrus. In mated rats, the glycogen content of the endometrium increases again after implantation due to high levels of glycogen stored in the decidua. In mink, endometrial glycogen reserves are localized in the uterine epithelia at estrus. These reserves are mobilized before implantation, suggesting they are used to support embryonic growth. Uterine glycogen concentrations continue to decrease after implantation in mink, probably due to a lack of decidualization. How ovarian steroids stimulate glycogenesis in the endometrium is unclear, but current evidence suggests that estradiol/progesterone interacts with insulin or insulin-like growth factor signaling. In summary, endometrial glycogen is an essential source of glucose during the peri-implantation period. More work is needed to characterize differences among species, elucidate the fate of the glucose liberated from glycogen, and understand how ovarian steroids regulate glycogen metabolism in the uterus.

Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy

We have determined uterine glycogen content, metabolizing enzyme expression and activity in the mink, a species that exhibits obligatory embryonic diapause, resulting in delayed implantation. Gross uterine glycogen concentrations were highest in estrus, decreased 50% by diapause and 90% in pregnancy (P ≤ 0.05). Endometrial glycogen deposits, which localized primarily to glandular and luminal epithelia, decreased 99% between estrus and diapause (P ≤ 0.05) and were nearly undetectable in pregnancy. Glycogen synthase and phosphorylase proteins were most abundant in the glandular epithelia. Glycogen phosphorylase activity (total) in uterine homogenates was higher during estrus and diapause, than pregnancy. While glycogen phosphorylase protein was detected during estrus and diapause, glycogen synthase was almost undetectable after estrus, which probably contributed to a higher glycogenolysis/glycogenesis ratio during diapause. Uterine glucose-6-phosphatase 3 gene expression was greater during diapause, when compared to estrus (P ≤ 0.05) and supports the hypothesis that glucose-6-phosphate resulting from phosphorylase activity was dephosphorylated in preparation for export into the uterine lumen. The relatively high amount of hexokinase-1 protein detected in the luminal epithelia during estrus and diapause may have contributed to glucose trapping after endometrial glycogen reserves were depleted. Collectively, our findings suggest to us that endometrial glycogen reserves may be an important source of energy, supporting uterine and conceptus metabolism up to the diapausing blastocyst stage. As a result, the size of uterine glycogen reserves accumulated prior to mating may in part, determine the number of embryos that survive to the blastocyst stage, and ultimately litter size.

Tenascin is highly expressed in endometriosis and its expression is upregulated by estrogen

OBJECTIVE

To investigate the localization of tenascin expression in the endometrium of women without endometriosis and in endometriotic implants, and to determine the in vitro regulation of tenascin by E(2) in these tissues.

DESIGN

Experimental laboratory study.

SETTING

University medical center.

PATIENT(S)

Reproductive age women with or without endometriosis.

INTERVENTION(S)

Proliferative (n = 14), and secretory (n = 14) endometrium from women without endometriosis and endometriosis implants (n = 14) were used for immunohistochemical analysis. Endometrial and endometriotic stromal cells were grown in culture and treated with E(2), the estrogen receptor antagonist ICI 182 780 (ICI) alone, E(2) in combination with ICI, or vehicle (control) for 24 hours, and tenascin expression was analyzed by Western blotting.

MAIN OUTCOME MEASURE(S)

Expression levels of tenascin in normal endometrium and endometriotic implants and its regulation by E(2).

RESULT(S)

Tenascin immunostaining revealed an increasing intensity in the stromal cells, starting from normal secretory endometrium, then normal proliferative endometrium, and reaching the highest expression in endometriotic implants. Estradiol induced a significant increase in tenascin protein levels in the endometriotic stromal cells in culture.

CONCLUSION(S)

The modulation of tenascin as an extracellular matrix protein by E(2) in endometriotic stromal cells may be one of the factors playing a role in the development of endometriosis.

Elucidation of a role for stromal steroid hormone receptors in mammary gland growth and development using tissue recombinants

The use of tissue recombinants in conjunction with steroid receptor deficient mice is described as a tool to dissect the complex paracrine pathways of sex-hormone-regulated epithelial growth and ductal morphogenesis in the mammary gland and other hormone target organs. The basic methodology involves the construction of the four possible tissue recombinants composed of epithelium (E) and stroma (S) from wild-type (wt) and knock-out (KO) mice: wt-S + wt-S, wt-S + KO-E, KO-S + KO-E, and KO-S + wt-E. All tissue recombinants are grown as subrenal capsule grafts in nude mice. Following appropriate hormonal challenge epithelial growth can be studied in the four types of tissue recombinants. Such studies using estrogen receptor, androgen receptor and progesterone receptor knockout mice demonstrate that epithelial steroid receptors are neither necessary nor sufficient for hormonal regulation of epithelial proliferation. Instead, hormonal regulation of epithelial proliferation is a paracrine event mediated by hormone-receptor-positive stromal cells.

Stromal estrogen receptors mediate mitogenic effects of estradiol on uterine epithelium

Estradiol-17beta (E2) acts through the estrogen receptor (ER) to regulate uterine growth and functional differentiation. To determine whether E2 elicits epithelial mitogenesis through epithelial ER versus indirectly via ER-positive stromal cells, uteri from adult ER-deficient ER knockout (ko) mice and neonatal ER-positive wild-type (wt) BALB/c mice were used to produce the following tissue recombinants containing ER in epithelium (E) and/or stroma (S), or lacking ER altogether: wt-S + wt-E, wt-S + ko-E, ko-S + ko-E, and ko-S + wt-E. Tissue recombinants were grown for 4 weeks as subrenal capsule grafts in intact female nude mice, then the hosts were treated with either E2 or oil a week after ovariectomy. Epithelial labeling index and ER expression were determined by [3H]thymidine autoradiography and immunohistochemistry, respectively. In tissue recombinants containing wt-S (wt-S + wt-E, wt-S + ko-E), E2 induced a similar large increase in epithelial labeling index compared with oil-treated controls in both types of tissue recombinants despite the absence of epithelial ER in wt-S + ko-E tissue recombinants. This proliferative effect was blocked by an ER antagonist, indicating it was mediated through ER. In contrast, in tissue recombinants prepared with ko-S (ko-S + ko-E and ko-S + wt-E), epithelial labeling index was low and not stimulated by E2 despite epithelial ER expression in ko-S + wt-E grafts. In conclusion, these data demonstrate that epithelial ER is neither necessary nor sufficient for E2-induced uterine epithelial proliferation. Instead, E2 induction of epithelial proliferation appears to be a paracrine event mediated by ER-positive stroma. These data in the uterus and similar studies in the prostate suggest that epithelial mitogenesis in both estrogen and androgen target organs are stromally mediated events.

Relationship between cellular DNA synthesis, PCNA expression and sex steroid hormone receptor status in the developing mouse ovary, uterus and oviduct

The proliferative activities of the different cellular compartments of the developing mouse ovary, uterus, and oviduct were studied by radioautographic assessment of DNA synthesis with [3H]-thymidine labeling and by immunohistochemical staining of proliferating cell nuclear antigen (PCNA). The distributions of estrogen and progesterone receptors (ER and PR) were studied by immunohistochemical staining. The values of the PCNA positive staining indices were a little higher than that of the radioautographic labeling indices. However, linear relations were shown for the two indices. The proliferative activities were high from postnatal day 1-7 and decreased from day 14 in the different cellular compartments of the ovary. The proliferative activities were high on days 1, 3 and decreased from day 7 in the uterus and oviduct. Staining of ER and PR was very weak in the surface epithelium, stroma and large follicles of the ovary. Positive staining for ER occurred from day 14 in the uterine epithelium and from day 7 in oviductal epithelium. Positive staining for PR was observed from day 1 in both the uterine and oviductal epithelium. However, the positivity of both ER and PR occurred from postnatal day 1 in the stromal cells of the uterus and oviduct. These results suggest that the appearance of the steroid receptors differ between the different cellular compartment of the reproductive organs. The proliferative activities have an inverse relation with the expression of the steroid hormone receptors in the female reproductive organs during developmental stages.(ABSTRACT TRUNCATED AT 250 WORDS)

A simple efficient method for separating murine uterine epithelial and mesenchymal cells

A simple, and very efficient, method for isolating pure uterine epithelium from neonatal, immature, or adult mice and pure uterine mesenchyme from neonatal mice is described. The technique uses mild tryptic digestion of the tissues to loosen the adherence of the epithelium to its underlying mesenchyme followed by gentle mechanical manipulation to effect removal of the luminal epithelium as an intact tube of cells. The epithelial fraction collected by this method was free of stromal cell contamination as judged by microscopic examination of the freshly isolated cells and of cell cultures made from that fraction. The mesenchymal fraction was consistently devoid of epithelium when collected from neonatal mice (5 days old or younger), but mesenchyme from uteri of mice greater than or equal to 10 days old was usually contaminated with epithelial cells due to retention of glandular epithelial crypts in the mesenchyme following removal of the luminal epithelium. Both epithelial and mesenchymal cells obtained by this method are viable, as judged by their ability to attach, spread, and synthesize DNA in vitro. Epithelial cells isolated from 20-day-old or adult animals have a full complement of estrogen receptors, as assessed by whole cell uptake of [3H]estradiol. The technique described here has clear advantages over previously described methods for obtaining pure uterine epithelium and in addition allows mesenchymal tissue free of epithelial contamination to be obtained when applied to uteri of animals less than or equal to 5 days old.

Pattern of steroid interaction with inducers of aryl hydrocarbon hydroxylase activity in several cloned estradiol-responsive stromal cell strains from mouse endometrium

Several steroid responsive stromal cell strains were isolated from normal mouse endometrium. Both estrogen responsive and progesterone responsive strains were obtained. The estrogen responsive cells were also responsive to diethylstilbestrol (DES). The progesterone responsive strains were inhibited by estrone and estriol. One of the estrogen responsive cell strains, E041, was cloned in the presence and absence of 17-beta-estradiol (E2). Of 14 clones developed in the absence of E2 and screened for responsivity of growth, six were significantly responsive to E2. Six of 26 clones developed in the presence of E2 were responsive to E2. Microsomes isolated from these clones were shown to have aryl hydrocarbon hydroxylase (AHH) activity which was inducible with either benzanthracene (BA) or 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD). The basal levels of AHH activity were significantly reduced by E2 in E2 responsive clones. The TCDD induced levels of AHH activity in the E2 responsive and E2 non-responsive clones were significantly reduced by E2. The BA induced levels of AHH were significantly increased by E2 in one of the clones. These results show that mouse endometrial stroma consists of a number of populations of cells with different specific proliferative and metabolic responses to steroids.

A comparison of developmental changes in surface charge in mouse blastocysts and uterine epithelium using DEAE beads and dextran sulfate in vitro

The ability of 3.5-day mouse blastocysts and vesicles prepared from maternal uterine epithelium to adhere to surfaces by charge interactions was compared by observing their adhesion to DEAE-Sephadex beads in the presence of increasing concentrations of dextran sulfate. The adhesion frequency for both the blastocysts and epithelium declined in a manner suggesting that predominantly ionic sites were being titrated, but differences between the two tissues in characteristics of the titration curve and susceptibility to neuraminidase digestion indicated that nonionic interactions were relatively more important for blastocysts. Because the threshold concentration of dextran sulfate required to initiate displacement of uterine epithelium from the DEAE beads was at least 4X that required to initiate the displacement of blastocysts, we argue that the uterine epithelium had at least 4X more interactive charged groups on its surface than the blastocysts. These differences were even more pronounced 4.5 days after mating, a time when attachment to the uterine epithelium is normally first seen in vivo. Blastocysts isolated at this time showed a marked increase in resistance to polyanion competition, but the epithelium showed a nearly 50% decline in surface negative charge that was not compensated by nonionic mechanisms. These observations support the conclusion that the initial adhesion of blastocysts in vivo is accompanied by a reduction in negativity of the uterine epithelial surface and by the formation of new trophoblast cell surfaces that adhere by nonelectrostatic interactions.