Hoxa-10 regulates uterine stromal cell responsiveness to progesterone during implantation and decidualization in the mouse

Hoxa-10 is an AbdominalB-like homeobox gene that is expressed in the developing genitourinary tract during embryogenesis and in the adult uterus during early pregnancy. Null mutation of Hoxa-10 in the mouse causes both male and female infertility. Defective implantation and decidualization resulting from the loss of maternal Hoxa-10 function in uterine stromal cells is the cause of female infertility. However, the mechanisms by which Hoxa-10 regulates these uterine events are unknown. We have identified two potential mechanisms for these uterine defects in Hoxa-10(-/-) mice. First, two PGE2 receptor subtypes, EP3 and EP4, are aberrantly expressed in the uterine stroma in Hoxa-10(-/-) mice, while expression of several other genes in the stroma (TIMP-2, MMP-2, ER, and PR) and epithelium (LIF, HB-EGF, Ar, and COX-1) are unaffected before implantation. Further, EP3 and EP4 are inappropriately regulated by progesterone (P4) in the absence of Hoxa-10, while PR, Hoxa-11 and c-myc, three other P4-responsive genes respond normally. These results suggest that Hoxa-10 specifically mediates P4 regulation of EP3 and EP4 in the uterine stroma. Second, since Hox genes are implicated in local cell proliferation, we also examined steroid-responsive uterine cell proliferation in Hoxa-10(-/-) mice. Stromal cell proliferation in mutant mice in response to P4 and 17beta-estradiol (E2 was significantly reduced, while epithelial cell proliferation was normal in response to E2. These results suggest that stromal cell responsiveness to P4 with respect to cell proliferation is impaired in Hoxa-10(-/-) mice, and that Hoxa-10 is involved in mediating stromal cell proliferation. Collectively, these results suggest that Hoxa-10 mutation causes specific stromal cell defects that can lead to implantation and decidualization defects apparently without perturbing epithelial cell functions.

Fatty-acid amide hydrolase is expressed in the mouse uterus and embryo during the periimplantation period

Arachidonoylethanolamide (anandamide) is an endogenous ligand for cannabinoid receptors. We demonstrated previously that the periimplantation mouse uterus has high levels of anandamide and can synthesize and hydrolyse anandamide. In the present investigation, we examined the expression of the recently identified fatty-acid amide hydrolase (FAAH) gene, which is involved in hydrolyzing anandamide to arachidonic acid and ethanolamine, in the periimplantation mouse embryo and uterus. As previously reported, Northern blot hybridization detected a transcript of approximately 2.5 kilobases of FAAH mRNA in whole uterine poly(A)+ RNA samples. The levels of this mRNA were higher in the liver and brain than in the uterus. In the uterus, higher accumulation of FAAH mRNA occurred on Days 1-4 followed by declines on later days (Days 5-8) of pregnancy. In situ hybridization detected this mRNA primarily in uterine luminal and glandular epithelial cells on Days 1-4 of pregnancy. With the progression of implantation (Days 5-8), accumulation of this mRNA was retained in the luminal and glandular epithelia. In addition, implanting blastocysts showed accumulation of this mRNA. FAAH mRNA accumulation was absent or minimal in the myometrium during this period. Western blotting detected an approximately 60-kDa protein in uterine membrane preparations. In preimplantation embryos, FAAH mRNA was present in one-cell and two-cell embryos but was absent in embryos at the eight-cell/morula stage. However, this mRNA was again detected in Day 4 blastocysts. The presence of FAAH mRNA in one- and two-cell embryos reflects accumulation of maternal message, while its presence in blastocysts reflects embryonic gene activation. Collectively, our present and previous results provide evidence that FAAH is expressed in the mouse uterus and embryo during early pregnancy to modulate local levels of anandamide that could be important for embryo development and implantation.

Heparin-binding EGF-like growth factor interacts with mouse blastocysts independently of ErbB1: a possible role for heparan sulfate proteoglycans and ErbB4 in blastocyst implantation

Blastocyst implantation requires molecular and cellular interactions between the uterine luminal epithelium and blastocyst trophectoderm. We have previously shown that heparin-binding EGF-like growth factor (HB-EGF) is induced in the mouse luminal epithelium solely at the site of blastocyst apposition at 16:00 hours on day 4 of pregnancy prior to the attachment reaction (22:00-23:00 hours), and that HB-EGF promotes blastocyst growth, zona-hatching and trophoblast outgrowth. To delineate which EGF receptors participate in blastocyst activation, the toxicity of chimeric toxins composed of HB-EGF or TGF-(&agr;) coupled to Pseudomonas exotoxin (PE) were used as measures of receptor expression. TGF-(&agr;) or HB-EGF binds to EGF-receptor (ErbB1), while HB-EGF, in addition, binds to ErbB4. The results indicate that ErbB1 is inefficient in mediating TGF-(&agr;)-PE or HB-EGF-PE toxicity as follows: (i) TGF-(&agr;)-PE was relatively inferior in killing blastocysts, 100-fold less than HB-EGF-PE, (ii) analysis of blastocysts isolated from cross-bred egfr+/- mice demonstrated that HB-EGF-PE, but not TGF-(&agr;)-PE, killed egfr-/- blastocysts, and (iii) blastocysts that survived TGF-(&agr;)-PE were nevertheless killed by HB-EGF-PE. HB-EGF-PE toxicity was partially mediated by cell surface heparan sulfate proteoglycans (HSPG), since a peptide corresponding to the heparin-binding domain of HB-EGF as well as heparitinase treatment protected the blastocysts from the toxic effects of HB-EGF-PE by about 40%. ErbB4 is a candidate for being an HB-EGF-responsive receptor since RT-PCR analysis demonstrated that day 4 mouse blastocysts express two different erbB4 isoforms and immunostaining with anti-ErbB4 antibodies confirmed that ErbB4 protein is expressed at the apical surface of the trophectoderm cells. It is concluded that (i) HB-EGF interacts with the blastocyst cell surface via high-affinity receptors other than ErbB1, (ii) the HB-EGF interaction with high-affinity blastocysts receptors is regulated by heparan sulfate, and (iii) ErbB4 is a candidate for being a high-affinity receptor for HB-EGF on the surface of implantation-competent blastocysts.

COX-2 compensation in the uterus of COX-1 deficient mice during the pre-implantation period

Prostaglandins (PGs) produced by cyclooxygenase (COX) participate in many aspects of female reproduction. The two isoforms of cyclooxygenase, COX-1 and COX-2, have distinct expression patterns in the mouse uterus during the peri-implantation period and suggest their independent contribution to uterine PGs. Using wild type and COX-1(-/-) mice, we examined the role of COX-1-derived PGs on day 4 of pregnancy, when its expression is maximal. Uterine vascular permeability was measured by 125I-labeled bovine serum albumin (BSA) uptake, and PG content was measured by gas chromatography-mass spectrometry. Vascular permeability and PG concentrations were reduced in COX-1(-/-) mice, but by less than the expected amount. After ovariectomy, uterine vascular permeability declined in both groups, but returned to baseline in wild type and was exaggerated in COX-1(-/-) females after treatment with ovarian steroids. Most importantly, COX-1(-/-) uteri displayed COX-2 expression on the morning of day 4, when COX-2 is normally absent. This hybridization pattern resembles the native expression of COX-1, and may partially offset the loss of COX-1-derived PGs. These data indicate that COX-1-derived PGs are important during uterine preparation for implantation, and that COX-2 compensation occurs in the absence of COX-1.

Zonula occludens-1 and E-cadherin are coordinately expressed in the mouse uterus with the initiation of implantation and decidualization

Two-way interactions between the blastocyst trophectoderm and the uterine luminal epithelium are essential for implantation. The key events of this process are cell-cell contact of trophectoderm cells with uterine luminal epithelial cells, controlled invasion of trophoblast cells through the luminal epithelium and the basement membrane, transformation of uterine stromal cells surrounding the blastocyst into decidual cells, and protection of the "semiallogenic" embryo from the mother's immunological responses. Because cell-cell contact between the trophectoderm epithelium and the luminal epithelium is essential for implantation, we investigated the expression of zonula occludens-1 (ZO-1) and E-cadherin, two molecules associated with epithelial cell junctions, in the mouse uterus during the periimplantation period. Preimplantation uterine epithelial cells express both ZO-1 and E-cadherin. With the initiation and progression of implantation, ZO-1 and E-cadherin are expressed in stromal cells of the primary decidual zone (PDZ). As trophoblast invasion progresses, these two molecules are expressed in stroma in advance of the invading trophoblast cells. These results suggest that expression of these adherence and tight junctions molecules in the PDZ serves to function as a permeability barrier to regulate access of immunologically competent maternal cells and/or molecules to the embryo and provide homotypic guidance of trophoblast cells in the endometrium.

Stage-specific excitation of cannabinoid receptor exhibits differential effects on mouse embryonic development

Anandamide (N-arachidonoylethanolamine), an arachidonic acid derivative, is an endogenous ligand for both the brain-type (CB1-R) and spleen-type (CB2-R) cannabinoid receptors. We have previously demonstrated that preimplantation mouse embryos express mRNA for these receptors and that the periimplantation uterus contains the highest level of anandamide yet discovered in a mammalian tissue. We further demonstrated that 2-cell mouse embryos exposed to low levels of anandamide (7 nM) or other known cannabinoid agonists in culture exhibit markedly compromised embryonic development to blastocysts and that this effect is mediated by CB1-R. In contrast, the present study demonstrates that blastocysts exposed in culture to the same low levels of cannabinoid agonists exhibited accelerated trophoblast differentiation with respect to fibronectin-binding activity and trophoblast outgrowth. Again, these effects resulted from activation of embryonic CB1-R. There was a differential concentration-dependent effect of cannabinoids on the trophoblast, with an observed inhibition of differentiation at higher doses. These results provide evidence for the first time that cannabinoid effects are differentially executed depending on the embryonic stage and cannabinoid levels in the environment. Since uterine anandamide levels are lowest at the sites of implantation and highest at the interimplantation sites, the new findings imply that site-specific levels of anandamide and/or other endogenous ligands in the uterus may regulate implantation spatially by promoting trophoblast differentiation at the sites of blastocyst implantation.

Homeopathy in HIV infection: a trial report of double-blind placebo controlled study

OBJECTIVE

This study was aimed to evaluate the immuno-modulator role of homeopathic remedies in Human Immunodeficiency Virus (HIV) infection.

METHODOLOGY

A randomised double blind clinical trial was conducted to compare the effect of homeopathic remedies with placebo, on CD4+ve T-lymphocytes in HIV infected individuals, conforming to Centres for Disease Control (CDC) stage II & III. 100 HIV+ve individuals between 18-50 y (71% males) were included in the study. 50 cases conformed to CDC stage II--Asymptomatic HIV infection, and 50 cases to CDC stage III--Persistent Generalised Lymphadenopathy (PGL). Cases were stratified according to their clinical status and CD4+ve lymphocyte counts. The randomisation charts were prepared much before the start of the trial by randomly assigning placebo and verum codes to registration numbers from 1 to 50. A single individualised homeopathic remedy was prescribed in each case and was followed up at intervals of 15 d to one month. A six months study was performed for each registered case. Assessment of progress was made by evaluation of CD+ve lymphocyte counts, which was the prospectively-defined main outcome measure of the study; the results were compared with the base line immune status.

RESULTS

In PGL, a statistically significant difference was observed in CD+ve T-lymphocyte counts between pre and post trial levels in verum group (P < 0.01). In the placebo group a similar comparison yielded non-significant results. (P = 0.91). Analysis of change in the pre and post trial counts of CD4+ve cells between groups was also statistically significant (P = 0.04). In asymptomatic HIV infection, differences in absolute CD4+ve lymphocyte counts between pre and post trial levels were not significant. Analysis of changes in pre and post trial CD4 levels of placebo and verum groups for combined strata of asymptomatic and PGL groups was also not significant.

CONCLUSION

The study suggests a possible role of homeopathic treatment in HIV infection in symptomatic phase, as evidenced by a statistically significant elevation of base line immune status in persistent generalised lymphadenopathy.

Spatiotemporal expression of cyclooxygenase 1 and cyclooxygenase 2 during delayed implantation and the periimplantation period in the Western spotted skunk

Embryonic development in the western spotted skunk is arrested after blastocyst formation for about 200 days. This developmental arrest is believed to be due to insufficiency of uterine conditions to support continuous development. Implantation and decidualization are defective in cyclooxygenase 2 (Cox2)-, but not Cox1-, deficient mice. We therefore used Northern and in situ hybridization to investigate changes in uterine expression of Cox1 and Cox2 genes during various stages of pregnancy in the spotted skunk. Cox1 was constitutively expressed at all stages of pregnancy examined, but it did exhibit localized up-regulation in the trophoblast and necks of uterine glands at early implantation sites. Cox2 expression was highly regulated with little or no expression during delayed implantation. Cox2 expression was first detected in the uterus and trophoblast prior to blastocyst attachment and remained detectable for 5-6 days after blastocyst attachment. Cox2 expression was also localized in the luminal and glandular epithelia of uterine segments located between implantation chambers. Changes in Cox expression were not correlated with the abrupt increase in uterine weight that occurs simultaneously with renewed embryonic development but was correlated with an influx of serum proteins into the uterus observed in a previous study.

Changes in uterine expression of leukemia inhibitory factor during pregnancy in the Western spotted skunk

Mutation of the leukemia inhibitory factor (LIF) gene results in reproductive failure in LIF -/- mice due to an inability to implant their blastocysts. This condition is reversed by infusion of LIF or by transferral of embryos to pseudopregnant, wild-type mice. This led us to hypothesize that embryonic diapause in the spotted skunk is due to insufficient uterine expression of LIF whereas resumption of development and implantation are associated with increased LIF expression. We also investigated the hormonal control of LIF expression. Uterine concentrations of LIF mRNA were determined by quantitative reverse transcription-polymerase chain reaction. Changes in cell-specific localization of LIF mRNA and protein were determined by in situ hybridization and immunocytochemistry. LIF mRNA was detected but was not abundant during embryonic diapause; it then increased when blastocysts resumed development and remained elevated prior to implantation. LIF mRNA and protein could not be localized in the uterus during embryonic diapause but were quite apparent in luminal and glandular epithelium during blastocyst activation. Prolactin, progesterone, and estradiol failed to increase uterine concentrations of LIF mRNA above those in ovariectomized controls. These data are consistent with the initial hypothesis and suggest that LIF may somehow be involved in preparing the uterus for implantation in the spotted skunk.

Cyclin D3 in the mouse uterus is associated with the decidualization process during early pregnancy

In the mouse, the attachment reaction between the blastocyst trophectoderm and the receptive uterine luminal epithelium occurs at 2200-2300 h on day 4 of pregnancy and is rapidly followed by transformation of stromal cells into decidual cells (decidual cell reaction). This process can also be induced experimentally (deciduoma) by intraluminal oil infusion in the uterus on day 4 of pseudopregnancy. The decidual cell reaction is associated with up- and down-regulation of many genes in a cell-specific manner. Using mRNA differential display, we identified cyclin D3 as one of the genes that is upregulated in the uterus at the sites of blastocyst apposition during the attachment reaction. The levels of expression were low in the morning of days 1-4 as determined by Northern hybridization. In situ hybridization analysis showed that on days 1 and 2, signals were primarily localized in uterine epithelial cells, while signals were detected in both the stromal and epithelial cells on days 3 and 4. In contrast, with the initiation and progression of decidualization on days 5, 6 and 7, the levels of cyclin D3 mRNA were remarkably upregulated in stromal cells both at the mesometrial and the antimesometrial poles. However, on day 8, signals were primarily localized in stromal cells at the mesometrial decidual bed. Implanting blastocysts on these days also expressed cyclin D3 mRNA. In the progesterone-treated delayed implanting mice, the uterine levels of cyclin D3 mRNA were modest at the sites of blastocyst apposition, but were upregulated with the onset of implantation by estradiol-17beta. However, the decidual expression of cyclin D3 mRNA was not dependent on the presence of blastocysts, since increased expression also occurred in experimentally induced deciduoma in the absence of blastocysts. The importance of cyclin D3 in decidualization was further examined in Hoxa-10-deficient mice which show defective decidualization. The expression of cyclin D3 mRNA in Hoxa-10(-/-) uteri on day 5 was severely compromised after application of a deciduogenic stimulus on day 4 of pseudopregnancy. Collectively, the results suggest that cyclin D3 could be important for the process of decidualization.

erbB genes in the mouse uterus: cell-specific signaling by epidermal growth factor (EGF) family of growth factors during implantation

We previously described spatiotemporal expression of various epidermal growth factor (EGF)-like ligands and receptor subtypes, ErbB1 and ErbB2, during the peri-implantation period. To better understand the roles of these ligands and their possible signaling schemes in implantation, it is important to define the status of all the ligands and receptor subtypes in the uterus/embryo. No information is available about uterine and embryonic status of ErbB3 or ErbB4 during implantation. We cloned mouse erbB3 and erbB4 cDNAs and examined their expression and bioactivity in the peri-implantation uterus (days 1-8). Two erbB3 (cytoplasmic and extracellular) and three erbB4 (two cytoplasmic and one extracellular) clones were generated. Both forms of the erbB3 clone showed similar transcript profiles, while different transcript profiles were obtained with erbB4 clones. The steady-state levels of erbB3 and erbB4 mRNAs in whole uterine poly(A)+ RNA samples showed little changes during the peri-implantation period, while their unique cell-specific accumulation was noted. erbB3 is predominantly expressed in the epithelial cells, although decidual and embryonic cells also accumulate this mRNA. In contrast, the erbB4 mRNA is primarily expressed in the submyometrial stroma and myometrial connective tissues during this period. Additionally, the extracellular form of the erbB4 clone detected signals in a subpopulation of stromal cells. Autophosphorylation and immunoprecipitation studies provided evidence that uterine ErbB3 and ErbB4 are biologically active. This study provides a comprehensive analysis of possible ligand-receptor signaling schemes for EGF-like ligands in implantation.

Coordination of differential effects of primary estrogen and catecholestrogen on two distinct targets mediates embryo implantation in the mouse

In the mouse, estrogen is essential for blastocyst implantation in the progesterone (P4)-primed uterus. The mechanism(s) by which estrogen initiates this response still remains elusive. The present investigation, using delayed implantation in the mouse, examined the differential role of estradiol-17beta (E2) and its catechol metabolite 4-hydroxy-E2 (4-OH-E2) in uterine and blastocyst activation for implantation. The conditions of delayed implantation were induced by ovariectomizing mice on day 4 (day 1 = vaginal plug) of pregnancy or pseudopregnancy and maintaining them with P4 from days 5-7. The binding of EGF to blastocysts was used as a marker for blastocyst activation. Our results show that whereas E2 fails to activate dormant blastocysts (with respect to EGF binding in vitro), 4-OH-E2, cAMP, or prostaglandin E2, is effective in this response. Further, whereas 4-OH-E2 induced-activation is not blocked by an antiestrogen, an inhibitor of PG synthesis, adenylyl cyclase or protein kinase A effectively blocks this activation. These results suggest that 4-OH-E2 effects on blastocysts are mediated by PGs, which, in turn, stimulate cAMP production and thus activation of protein kinase A. Two-fluoro-E2 is a poor substrate and an inhibitor of catecholestrogen synthesis, but it is estrogenic, with respect to uterine growth and gene expression. Using blastocyst transfer experiments, we observed that dormant blastocysts incubated with 4-OH-E2 in vitro, but not with E2, are capable of implanting in P4-treated delayed implanting mice receiving two-fluoro-E2. The results suggest that whereas E2 is necessary for preparation of the uterus, uterine-derived catecholestrogen is important for blastocyst activation for implantation. Indeed, the receptive uterus has the capacity to synthesize 4-OH-E2. Collectively, we demonstrate that the primary ovarian estrogen E2, via its interaction with nuclear estrogen receptors, participates in the preparation of the P4-primed uterus to the receptive state in an endocrine manner, whereas its metabolite 4-OH-E2, produced from E2 in the uterus, mediates blastocyst activation for implantation in a paracrine manner. Our results also establish that these target-specific effects of primary estrogen and catecholestrogen are both essential for implantation and that successful implantation occurs only when the activated stage of the blastocyst coincides with the receptive state of the uterus.

Histidine decarboxylase gene in the mouse uterus is regulated by progesterone and correlates with uterine differentiation for blastocyst implantation

Cell-cell interactions between the blastocyst trophectoderm and uterine luminal epithelium are essential to the process of implantation. The factors that participate in these interactions or their mechanism of actions are poorly understood. Histamine has long been suspected as one of the factors that is involved in implantation. Histamine is formed from L-histidine by histidine decarboxylase (HDC). We examined the expression and regulation of HDC gene in the mouse uterus during early pregnancy and under steroid hormonal stimulation. Northern blot hybridization detected a 2.6-kb transcript of HDC messenger RNA (mRNA) in uterine poly(A)+ RNA samples. Maximum uterine accumulation of HDC mRNA occurred on days 3 and 4 of pregnancy, followed by marked declines on later days (days 5-8). In ovariectomized mice, uterine mRNA levels were up-regulated by an injection of progesterone (P4) by 6 h, and the levels were maintained through 24 h. In contrast, an injection of estradiol-17beta neither stimulated nor antagonized P4-induced HDC mRNA accumulation. P4-induced up-regulation was considerably abrogated by pretreatment with RU-486, a P4 receptor antagonist, suggesting involvement of P4 receptor. In situ hybridization detected HDC mRNA specifically in uterine epithelial cells but not in other cell types. Again, high epithelial accumulation occurred on day 4 of pregnancy. With the progression of implantation (days 5-8), HDC mRNA levels declined in the luminal epithelium surrounding the implanting blastocysts, as compared with that away from the blastocysts. Immunoreactive histamine and HDC were colocalized with HDC mRNA. Western blotting detected a 54-kDa protein in epithelial cell extracts, which also exhibited HDC activity. Expression of HDC in epithelial cells, preceding implantation on day 4, at lower levels after initiation of implantation on day 5, and its regulation by P4 suggest that this gene plays an important role in implantation.

Differential spatiotemporal regulation of lactoferrin and progesterone receptor genes in the mouse uterus by primary estrogen, catechol estrogen, and xenoestrogen

Many xenobiotics are considered reproductive toxins because of their ability to interact with the nuclear estrogen receptors (ERalpha and ERbeta). However, there is evidence that these xenobiotics can regulate gene expression in the reproductive targets by mechanisms that do not involve these ERs. To examine this further, we compared the effects of estrogenic (o,p'-DDT [1-(o-chlorophenyl)-1-(p-chlorophenyl)2,2,2-trichloroethane] and Kepone, chlordecone) and nonestrogenic (p,p'-DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane], a metabolite of p,p'-DDT) xenobiotics with those of 17beta-estradiol (E2) and 4-hydroxyestradiol-17beta (4-OH-E2), a catechol metabolite of E2, on uterine expression of lactoferrin (LF) and progesterone receptor (PR). These genes are estrogen responsive in the mouse uterus. Normally, LF is expressed in the uterine epithelium, whereas PR is expressed in both the epithelium and stroma in response to estrogenic stimulation. Ovariectomized mice were injected with xenobiotics (7.5 mg/kg), E2 (10 microg/kg), 4-OH-E2 (10 microg/kg), or the vehicle (oil, 0.1 ml/mouse), and uterine tissues were processed for Northern blot and in situ hybridization. The pure antiestrogen ICI-182780 (ICI; 1 or 20 mg/kg) was used to interfere with estrogenic responses that were associated with the ERs. The results of Northern and in situ hybridization demonstrated increased uterine levels of PR and LF messenger RNAs (mRNAs) by all of these xenobiotics, but quantitatively the responses were much lower than those induced by E2 or 4-OH-E2. The results further showed that the E2-inducible epithelial LF mRNA accumulation was markedly abrogated by pretreatment with ICI (20 mg/kg). In contrast, this treatment retained the epithelial expression of PR mRNA, but down-regulated the stromal expression. In contrast, ICI had negligible effects on LF and PR mRNA responses to 4-OH-E2, indicating that this catechol estrogen exerted its effects primarily via a mechanism(s) other than the ERs. The heightened accumulation of LF mRNA in the epithelium in response to Kepone and o,p'-DDT was also severely compromised by pretreatment with ICI, but this antiestrogen had little effect on responses to p,p'-DDD. Similar to E2, Kepone increased the expression of PR mRNA in both uterine epithelium and stroma. However, pretreatment with ICI decreased stromal cell expression, whereas epithelial cell expression remained unaltered or increased. These responses were not noted in mice treated with o,p'-DDT or p,p'-DDD. Collectively, the results demonstrate that catechol estrogens or xenobiotics can alter uterine expression of estrogen-responsive genes by mechanisms that are not totally mediated by the classical nuclear ERs, and these alterations are cell type specific. We conclude that an interaction of a compound with the nuclear ERalpha and/or ERbeta is not an absolute requirement for producing specific estrogen-like effects in the reproductive target tissues.

Effects of cannabinoids on preimplantation mouse embryo development and implantation are mediated by brain-type cannabinoid receptors

We examined the relative importance of G (Gi) protein-coupled brain-type (CB1-R) and spleen-type (CB2-R) cannabinoid receptors in preimplantation embryo development using agonists and antagonists specific to CB1-R and CB2-R. The results establish that endogenous cannabinoid ligands, anandamide and sn-2 arachidonoylglycerol, arrest embryo development in vitro, and this effect is reversed by CB1-R antagonists SR141716A or AM 251, but not by SR144528, a CB2-R antagonist. A CB2-R selective agonist AM 663 failed to affect embryo development. These results suggest that cannabinoid effects on embryo development are mediated by CB1-R. We also observed that delta9-tetrahydrocannabinol ([-]THC) infused in the presence of cytochrome P450 inhibitors interfered with blastocyst implantation. This adverse effect was reversed by coinfusion of SR141716A. The less active stereoisomer (+)THC plus the inhibitors failed to affect implantation. Analysis of tissue levels demonstrated that uterine accumulation of (-)THC occurred when it was infused in the presence of the P450 inhibitors. These results demonstrate that the uterus and perhaps the embryo have the cytochrome P450 enzymes to metabolize (-)THC and neutralize its adverse effects on implantation. Collectively, the present study demonstrates that cannabinoid effects on embryo development and implantation are mediated by embryonic and/or uterine CB1-R, but not CB2-R.

Abdominal B (AbdB) Hoxa genes: regulation in adult uterus by estrogen and progesterone and repression in müllerian duct by the synthetic estrogen diethylstilbestrol (DES)

Mice deficient for the Abdominal B (AbdB) Hox gene Hoxa-10 exhibit reduced fertility due to defects in implantation. During the peri-implantation period Hoxa-10 is sequentially expressed in the uterine epithelium and stroma. These observations, combined with the stringent regulation of uterine implantation by ovarian steroids, prompted us to test whether estrogen and progesterone directly regulate the expression of Hoxa-10 and other AbdB Hoxa genes. Here we show that Hoxa-10 expression in the adult uterus is strongly activated by progesterone. This activation is blocked by the progesterone receptor antagonist RU486 and is independent of new protein synthesis. In addition, Hoxa-10 expression is repressed by estrogen in a protein synthesis-independent manner. Analysis of adjacent AbdB Hoxa genes reveals that Hoxa-9 and a-11 are also activated in a colinear fashion by progesterone but differentially regulated by estrogen. These results suggest that the regulation of AbdB Hox gene expression in the adult uterus by ovarian steroids is a property related to position within the cluster, mediated by the direct action of estrogen and progesterone receptors upon these genes. We next examined whether the embryonic expression of Hoxa10 is regulable by hormonal factors. Previous work has demonstrated that perinatal administration of the synthetic estrogen diethylstilbestrol (DES) to mice and humans produces uterine, cervical, and oviductal malformations. Certain of these phenotypes resemble those in Hoxa-10 knockout mice, suggesting that Hoxa-10 gene expression might be repressed by DES during reproductive tract morphogenesis. Exposure of the developing female reproductive tract to DES, either in vivo or in organ culture, represses the expression of Hoxa-10 in the Müllerian duct. Thus, these data not only establish a direct link between ovarian steroids and AbdB Hoxa gene expression in the adult uterus, but also provide a potential mechanism for the teratogenic effects of DES on the developing reproductive tract.

Expression of neu differentiation factor during the periimplantation period in the mouse uterus

Complex cellular interactions occur between the blastocyst and the uterus during implantation. The expression of various polypeptide growth factors and their receptors in the uterus and/or blastocyst during the periimplantation period suggest that growth factors participate in the implantation process. Neu differentiation factor (NDF) is a member of the epidermal growth factor (EGF) family of growth factors and is represented by multiple conserved isoforms. The expression of several EGF-like ligands in the periimplantation uterus has been characterized, including EGF, heparin binding-EGF, transforming growth factor alpha, amphiregulin, betacellulin, and epiregulin. We analyzed the expression pattern of NDF in the periimplantation mouse uterus because of its mitogenic and differentiation-promoting effects. By using Northern analysis and isoform-specific polymerase chain reaction, we found that multiple isoforms are expressed in the periimplantation uterus. NDF displays a highly restricted temporal and spatial expression, with autoradiographic signals localized to the uterine stroma immediately surrounding the implanting blastocyst. NDF expression was absent in mice with delayed implantation but briefly reappeared with the same restricted distribution after termination of the delay by an injection of estrogen. Taken together, these results suggest that an activated blastocyst is required for the expression of NDF and that multiple isoforms may be involved in the complex network of cell-signaling events between the implanting blastocyst and the receptive uterus.

Estrogenic responses in estrogen receptor-alpha deficient mice reveal a distinct estrogen signaling pathway

Estrogens are thought to regulate female reproductive functions by altering gene transcription in target organs primarily via the nuclear estrogen receptor-alpha (ER-alpha). By using ER-alpha "knock-out" (ERKO) mice, we demonstrate herein that a catecholestrogen, 4-hydroxyestradiol-17beta (4-OH-E2), and an environmental estrogen, chlordecone (kepone), up-regulate the uterine expression of an estrogen-responsive gene, lactoferrin (LF), independent of ER-alpha. A primary estrogen, estradiol-17beta (E2), did not induce this LF response. An estrogen receptor antagonist, ICI-182,780, or E2 failed to inhibit uterine LF gene expression induced by 4-OH-E2 or kepone in ERKO mice, which suggests that this estrogen signaling pathway is independent of both ER-alpha and the recently cloned ER-beta. 4-OH-E2, but not E2, also stimulated increases in uterine water imbibition and macromolecule uptake in ovariectomized ERKO mice. The results strongly imply the presence of a distinct estrogen-signaling pathway in the mouse uterus that mediates the effects of both physiological and environmental estrogens. This estrogen response pathway will have profound implications for our understanding of the physiology and pathophysiology of female sex steroid hormone actions in target organs.

Prostaglandin E2 receptor subtype EP2 gene expression in the mouse uterus coincides with differentiation of the luminal epithelium for implantation

Among the PGs, PGE2 is considered especially important for implantation and decidualization. Four major PGE2 receptor subtypes, EP1, EP2, EP3, and EP4, mediate various PGE2 effects via their coupling to distinct signaling pathways. Previously, we have shown that the EP1, EP3, and EP4 genes are expressed in the periimplantation mouse uterus in a spatio-temporal manner, suggesting compartmentalized actions of PGE2 during this period. In this study, we examined the expression of the EP2 gene in the mouse uterus during the periimplantation period (days 1-8) and during experimentally induced progesterone (P4)-maintained delayed implantation and its resumption by 17beta-estradiol (E2). We also examined its regulation in the uterus by ovarian steroid hormones. Our results establish that EP2 messenger RNA (mRNA) is expressed exclusively in the luminal epithelium primarily on day 4 (the day of implantation) and day 5 (early implantation) of pregnancy. In (P4)-maintained delayed implanting mice, EP2 mRNA was present in the luminal epithelium, and the expression was further enhanced regardless of the location of the blastocysts after reinitiation of implantation. This observation suggests little or no embryonic influence in regulating EP2 expression and, instead, shows its regulation by P4 and E2. Indeed, treatment with E2 and/or P4 exhibited unique regulation of this gene. The treatment of adult ovariectomized mice with E2 down-regulated the basal levels of EP2 mRNA, whereas that with P4 up-regulated its levels in the luminal epithelium. The up-regulation of EP2 mRNA levels by P4 was further augmented by superimposition of the E2 treatment, suggesting a synergistic interaction between E2 and P4 in regulating this gene in the uterus. Collectively, the results suggest that EP2 could be a potential mediator of PGE2 actions in regulating luminal epithelial differentiation and serve as a marker for uterine receptivity for implantation.

Multiple female reproductive failures in cyclooxygenase 2-deficient mice

Cyclooxygenase (COX) is the rate-limiting enzyme in the synthesis of prostaglandins (PGs) and exists in two isoforms, COX-1 and COX-2. In spite of long-standing speculation, definitive roles of PGs in various events of early pregnancy remain elusive. We demonstrate herein that the targeted disruption of COX-2, but not COX-1, in mice produces multiple failures in female reproductive processes that include ovulation, fertilization, implantation, and decidualization. Using multiple approaches, we conclude that these defects are the direct result of target organ-specific COX-2 deficiency but are not the result of deficiency of pituitary gonadotropins or ovarian steroid hormones, or reduced responsiveness of the target organs to their respective hormones.

Expression of betacellulin and epiregulin genes in the mouse uterus temporally by the blastocyst solely at the site of its apposition is coincident with the "window" of implantation

In the mouse, the process of implantation is initiated by the attachment reaction between the blastocyst trophectoderm and uterine luminal epithelium that occurs at 2200-2300 h on day 4 (day 1 = vaginal plug) of pregnancy. Several members of the EGF family are considered important in embryo-uterine interactions during implantation. This investigation demonstrates that the expression of two additions to the family, betacellulin and epiregulin, are exquisitely restricted to the mouse uterine luminal epithelium and underlying stroma adjacent to the implanting blastocyst. These genes are not expressed during progesterone-maintained delayed implantation, but are rapidly switched on in the uterus surrounding the implanting blastocyst following termination of the delay by estrogen. These results provide evidence that expression of betacellulin and epiregulin in the uterus requires the presence of an active blastocyst and suggest an involvement of these growth factors in the process of implantation.

Production and physiological actions of anandamide in the vasculature of the rat kidney

The endogenous cannabinoid receptor agonist anandamide is present in central and peripheral tissues. As the kidney contains both the amidase that degrades anandamide and transcripts for anandamide receptors, we characterized the molecular components of the anandamide signaling system and the vascular effects of exogenous anandamide in the kidney. We show that anandamide is present in kidney homogenates, cultured renal endothelial cells (EC), and mesangial cells; these cells also contain anandamide amidase. Reverse-transcriptase PCR shows that EC contain transcripts for cannabinoid type 1 (CB1) receptors, while mesangial cells have mRNA for both CB1 and CB2 receptors. EC exhibit specific, high-affinity binding of anandamide (Kd = 27.4 nM). Anandamide (1 microM) vasodilates juxtamedullary afferent arterioles perfused in vitro; the vasodilation can be blocked by nitric oxide (NO) synthase inhibition with L-NAME (0.1 mM) or CB1 receptor antagonism with SR 141716A (1 microM), but not by indomethacin (10 microM). Anandamide (10 nM) stimulates CB1-receptor-mediated NO release from perfused renal arterial segments; a similar effect was seen in EC. Finally, anandamide (1 microM) produces a NO-mediated inhibition of KCl-stimulated [3H]norepinephrine release from sympathetic nerves on isolated renal arterial segments. Hence, an anandamide signaling system is present in the kidney, where it exerts significant vasorelaxant and neuromodulatory effects.

Expression of vascular endothelial growth factor (VEGF) and VEGF-receptor messenger ribonucleic acids in the peri-implantation rabbit uterus

The endometrial vasculature undergoes expansion during preimplantation stages and, even more prominently, after implantation. In addition to angiogenesis, vascular hyperpermeability accompanies the attachment and invasion of blastocysts into the uterine lining. Vascular endothelial growth factor (VEGF) is an angiogenic factor expressed in mammalian uteri that also has potent activity in inducing vascular permeability. Rabbit uteri were examined using Northern and in situ hybridization to assess the temporal and spatial expression of VEGF and its receptor (Flk-1, Flt-1) mRNAs during the pre- and peri-implantation periods (Days 0-8). Steady-state levels of VEGF mRNA were highest in endometrium at estrous and peri-implantation stages (Days 6-8). In situ hybridization revealed a shift from uniform expression of VEGF transcripts throughout the uterus at estrus and Day 4, to an endometrial epithelial localization just before and during implantation. At implantation sites, a pronounced signal was present in the trophoblastic knobs, the syncytial aggregates that attach to and invade the endometrium. VEGF protein was detected by immunoblot analysis in peri-implantation-stage uteri but was below the limit of detection in estrous endometrium. VEGF receptor mRNAs were expressed in the uterus at all stages examined, with high levels of Flk-1 and Flt-1 at estrus and again just before implantation, 6-3/4 days pregnant. The high level just before implantation correlates with in situ hybridization results showing a prominent, but transient, signal for Flk-1 mRNA in the endometrial epithelium. During implantation, Flk-1 mRNA was associated with blood vessels of the endometrial stroma. We conclude that VEGF is a candidate factor for the induction of vascular hyperpermeability at implantation in the rabbit and in the angiogenic process that follows.