Distribution of transforming growth factor alpha precursors in the mouse uterus during the periimplantation period and after steroid hormone treatments

Establishment of a Primary Culture Model of Mouse Uterine and Vaginal Stroma for Studying In Vitro Estrogen Effects

Effects of 17β-estradiol (E2) on uterine and vaginal epithelial cell proliferation could be mediated by stromal cell-derived paracrine factors. To study the epithelial-stromal interactions in mice, an in vitro model of uterine and vaginal stromal cells of immature mice is essential. Therefore, we established a primary culture model of stromal cells both from uterus and vagina and examined the effect of E2 on proliferation of cultured stromal cells. We found that E2 stimulated proliferation of stromal cells from both organs in vitro, showing an increase in the number of cells and the percentage of 5-bromo-2'-deoxyurldine (BrdU)-labeled cells. Interestingly, vaginal stromal cells responded to lower E2 than uterine stromal cells in proliferation (10−12 M vs. 10−8 M) and BrdU labeling (10−14 -10−10 M vs. 10−10 - 10−6 M). To examine the effect of E2 in vivo, cells were grafted into the subrenal capsule of the host mice and grown for 2 weeks. The BrdU labeling in cultured stromal cells was increased by E2 in vivo. To examine the effect of cultured stromal cells on epithelial cell proliferation, uterine and vaginal epithelium of adult mice were separated, recombined with the cultured stromal cells, and grafted under the renal capsule of hosts for 3 weeks. Epithelial cells recombined with cultured stromal cells showed simple columnar morphology in uterine grafts and stratified and keratinized morphology in vaginal grafts under the influence of the hormonal environment of the hosts. The BrdU labeling in epithelial cells was increased by E2, suggesting that cultured stromal cells can stimulate epithelial cell proliferation. In conclusion, we established a primary culture model of uterine and vaginal stromal cells, which can be mitogenically stimulated by E2 in vitro and in vivo after being grafted under the renal capsule. This culture system will be useful for investigating the underlying molecular mechanisms of uterine and vaginal epithelial-stromal interactions.

Autocrine embryotropins revisited: how do embryos communicate with each other in vitro when cultured in groups?

In the absence of the maternal genital tract, preimplantation embryos can develop in vitro in culture medium where all communication with the oviduct or uterus is absent. In several mammalian species, it has been observed that embryos cultured in groups thrive better than those cultured singly. Here we argue that group-cultured embryos are able to promote their own development in vitro by the production of autocrine embryotropins that putatively serve as a communication tool. The concept of effective communication implies an origin, a signalling agent, and finally a recipient that is able to decode the message. We illustrate this concept by demonstrating that preimplantation embryos are able to secrete autocrine factors in several ways, including active secretion, passive outflow, or as messengers bound to a molecular vehicle or transported within extracellular vesicles. Likewise, we broaden the traditional view that inter-embryo communication is dictated mainly by growth factors, by discussing a wide range of other biochemical messengers including proteins, lipids, neurotransmitters, saccharides, and microRNAs, all of which can be exchanged among embryos cultured in a group. Finally, we describe how different classes of messenger molecules are decoded by the embryo and influence embryo development by triggering different pathways. When autocrine embryotropins such as insulin-like growth factor-I (IGF-I) or platelet activating factor (PAF) bind to their appropriate receptor, the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) pathway will be activated which is important for embryo survival. On the other hand, the mitogen-activated protein kinase (MAPK) pathway is activated when compounds such as hyaluronic acid and serotonin bind to their respective receptors, thereby acting as growth factors. By activating the peroxisome-proliferator-activated receptor family (PPAR) pathway, lipophilic autocrine factors such as prostaglandins or fatty acids have both survival and anti-apoptotic functions. In conclusion, considering different types of messenger molecules simultaneously will be crucial to understanding more comprehensively how embryos communicate with each other in group-culture systems. This approach will assist in the development of novel media for single-embryo culture.

Transforming growth factor-α mRNA expression and its possible roles in mouse endometrial stromal cells

Transforming growth factor-α (TGFα) is thought to be involved in the regulation of endometrial cells. We investigated Tgfa mRNA expression, and the effects of TGFα on DNA-synthesis and gene expression of insulin-like growth factor 1 (IGF1), IGF binding protein-3 (IGFBP3) and IGF1 receptor in the mouse endometrial cells, because IGF1 is involved in estrogen-induced growth of endometrial cells. We also investigated the role of TGFα on matrix metalloproteinase (MMP) expression, as MMPs are involved both in tissue remodeling during cell proliferation and in enhancement of IGF1 signaling through the degradation of IGFBP3. Tgfa mRNA expression was detected in endometrial luminal and glandular epithelial cells, and stromal cells. Tgfa mRNA signals did not appear to change in endometrial luminal epithelial cells, but signals in glandular epithelial cells were higher at diestrus 1, 2 and proestrus, and the number of stromal cells showing strong signals appeared to increase at diestrus 1 and 2. Endometrial epithelial and stromal cells were treated with estradiol-17β (E2) or progesterone (P4). E2 or P4 stimulated Tgfa mRNA expression in stromal cells. TGFα stimulated DNA synthesis in endometrial epithelial and stromal cells, while E2 and P4 stimulated DNA synthesis in stromal cells. In stromal cells, TGFα, at as low as 1 ng/ml, decreased Igfbp3 and Mmp9 mRNA levels, while high dose (10 ng/ml) of TGFα decreased Igf1 mRNA level and increased Mmp3 mRNA level. These results imply that TGFα stimulates proliferation of endometrial stromal cells through multiple mechanisms, including its regulation of Igfbp3 and Mmp3 transcription.

Implantation-related expression of epidermal growth factor family molecules and their regulation by progesterone in the pregnant rat

The uterine expressions of epidermal growth factor(EGF) family are examined to elucidate their exact role(s) in rat pregnancy. EGF and its receptors' (EGF-R) mRNA levels increased significantly at implantation after which their expression gradually decreased. Heparin-binding EGF (HB-EGF) and transforming growth factor-alpha (TGF-alpha) showed a modest expression at gestation day (GD), GD4 and GD3, respectively, but were much strongly expressed at mid-pregnancy.Amphiregulin (Areg) was strongly expressed around implantation (GD4) and at mid-pregnancy (GD12).Treatment of pregnant rats with RU486 at GD5 or GD8 blocked the expression of all the genes, and administration of immature rats with progesterone (P4) induced the uterine expression of all the genes except HB-EGF. In addition, HB-EGF,TGF-alpha, and Areg proteins in the uterine and glandular epitheliums may participate in mid-pregnancy. Taken together, all of these activities are likely to be controlled by P4 in the uterus of pregnant rats.

Betacellulin Overexpression in the Mouse Ovary Leads to MAPK3/MAPK1 Hyperactivation and Reduces Litter Size by Impairing Fertilization1

The epidermal growth factor receptor (EGFR) and its ligands are emerging as key molecules in regulating female reproduction. Here, we used a transgenic mouse model to evaluate whether and at which level of the reproduction cascade higher-than-normal levels of the EGFR ligand betacellulin (BTC) in the reproductive organs affect fertility. Western blots and immunohistochemistry revealed increased BTC levels in uterus and ovaries from transgenic females, particularly evident in granulosa cells of antral follicles. Onset of puberty, estrous cyclicity, and the anatomy and histology of reproductive organs at puberty were not altered as compared to control females. Fertility tests revealed a reduction (~50%) in litter size as the major reproductive deficit of transgenic females. Embryo implantation was delayed in transgenic females, but this was not the reason for the reduced litter size. Transgenic females produced a normal number of oocytes after natural ovulation. The in vivo fertilization rate was significantly reduced in untreated transgenic females but returned to normal levels after superovulation. Impaired oocyte fertilization in the absence of superovulation treatment was associated with MAPK3/MAPK1 hyperactivation in BTC transgenic ovaries, whereas similar levels of MAPK3/MAPK1 activation were detected in transgenic and control ovaries after superovulation treatment. Thus, tight regulation of MAPK3/MAPK1 activity appears to be essential for appropriate granulosa cell function during oocyte maturation. Our study identified hitherto unknown effects of BTC overabundance in reproduction and suggests BTC as a novel candidate protein for the modulation of fertility.

Tumor necrosis factor regulation of apoptosis in mouse preimplantation embryos and its antagonism by transforming growth factor alpha/phosphatidylionsitol 3-kinase signaling system

Survival and apoptosis of cells in preimplantation embryos are fundamental for successful pregnancy. Relevant to these processes, tumor necrosis factor (TNF) and transforming growth factor alpha (TGFA) are produced by mammalian oviducts and uteri. In early embryos, TNF induces apoptosis, whereas TGFA could act as a survival factor. Here we investigated the TNF regulation of apoptosis in early mouse embryos and its antagonism by TGFA. TNF receptor superfamily, member 1a mRNA was detectable throughout early embryonic stages, with an increase after the early blastocyst stage, whereas the expression of TNF receptor superfamily, member 1b transcripts were detected only at the expanded blastocyst stage. Although pregnant uteri produced TNF, physiologic levels were low during the preimplantation period. Treatment with TNF inhibited the development of two-cell stage embryos to blastocysts showing decreased proliferation and increased apoptosis both in vitro and in vivo. These detrimental effects of TNF on early embryo development and survival were blocked by a neutralizing anti-TNF antibody. In addition to the death receptor-mediated pathway, TNF-induced apoptosis was further mediated by disruption of mitochondrial functions, characterized by release of cytochrome c and activation of caspase 9. The proapoptotic effects of TNF in blastocysts were counteracted by cotreatment with TGFA. The antagonistic effect of TGFA on TNF-induced apoptosis was blocked by phosphatidylionsitol 3-kinase (PI3K) inhibitors. The present findings demonstrate the stage-selective susceptibility to the apoptosis-inducing effect of TNF in mouse preimplantation embryos and that the TGFA/PI3K signaling system has an important role in the control of TNF-induced apoptosis in blastocysts.

Effects of Progranulin on Blastocyst Hatching and Subsequent Adhesion and Outgrowth in the Mouse1

Using cDNA microarray methodology, we have shown previously that transcripts of progranulin gene (Grn, also known as acrogranin), a recently identified autocrine growth factor, were upregulated in mouse blastocysts adhered to the filter membrane in an in vitro-culture system. In the present study, we investigated the expression and effects of progranulin on blastocyst hatching, adhesion, and embryo outgrowth during the peri-implantation period in the mouse. During this period, substantial amounts of Grn mRNA were present in both inner cell mass (ICM) and trophectoderm. Progranulin was localized exclusively to the surface of the trophectoderm in early and pre- and postadhesion blastocysts as well as in trophoblast cells and ICM of outgrowth embryos, being secreted as a single, 88-kDa form into the surrounding medium. NIH3T3 cells that had been transfected with a progranulin expression construct secreted the 88-kDa form of the protein, from which a 68-kDa form could be generated by deglycosylation. In vitro treatment of blastocysts with recombinant progranulin promoted blastocyst hatching, adhesion, and outgrowth, whereas rabbit anti-mouse progranulin immunoglobulin G reduced the incidence of blastocyst hatching, adhesion, and outgrowth. Studies of bromodeoxyuridine incorporation and immunodissection of the ICM revealed that progranulin was effective on the trophectoderm but not on the ICM. These results indicate that progranulin is an important factor for the processes of blastocyst hatching, adhesion, and outgrowth, and they suggest that the effects of progranulin on blastocyst adhesion and outgrowth may have been triggered by the previous action of progranulin to induce hatching of the blastocysts.

Survivin contributes to the anti-apoptotic activities of transforming growth factor alpha in mouse blastocysts through phosphatidylinositol 3'-kinase pathway

Transforming growth factor alpha (TGFA) is produced by epithelial cells in the oviducts and uteri and has the potential to act as an anti-apoptotic factor on preimplantation embryos expressing its receptor. Previously, we demonstrated that survivin (also known as BIRC5), an anti-apoptotic gene expressed in mouse preimplantation embryos, protects embryos from apoptosis. In this study, we investigated the role of survivin on TGFA-mediated inhibition of apoptosis in mouse blastocysts. Under the suboptimal conditions produced by single embryo culture, blastocysts showed an increase of apoptosis that correlated with a decrease of survivin expression. TGFA treatment significantly decreased apoptosis and increased the levels of survivin mRNA in a dose-dependent manner in blastocyst, and conversely, these activities were neutralized by an anti-TGFA antibody. Antibody treatment alone exerted little effect on either the occurrence of apoptosis or the levels of survivin mRNA. Upregulation of survivin expression by TGFA treatment was insignificant before the blastocyst stage. Using an antisense approach, we examined whether upregulation of survivin is responsible for the anti-apoptotic effect of TGFA in blastocysts. Apoptosis was inhibited by TGFA treatment in blastocysts, but the effect was abrogated by cotreatment with antisense oligonucleotides directed against survivin. These data suggest that survivin contributes to the anti-apoptotic activities of TGFA in blastocysts. We also found that the upregulation of survivin expression was mediated by activation of the phosphatidylinositol 3-kinase (PI3K) signaling pathway. Thus, TGFA inhibits apoptosis in mouse blastocysts through upregulation of survivin expression via the PI3K pathway.

Animal models of implantation

Implantation is an intricately timed event necessary in the process of viviparous birth that allows mammals to nourish and protect their young during early development. Human implantation begins when the blastocyst both assumes a fixed position in the uterus and establishes a more intimate relationship with the endometrium. Due to the impracticalities of studying implantation in humans, animal models are necessary to decipher the molecular and mechanical events of this process. This review will discuss the differences in implantation between different animal models and describe how these differences can be utilized to investigate discrete implantation stages. In addition, factors that have been shown to be involved in implantation in the human and other various animal models including growth factors, cytokines, modulators of cell adhesion, and developmental factors will be discussed, and examples from each will be given.

Dominant expression of porcine Calbindin-D9k in the uterus during a luteal phase

Calbindin-D9k (CaBP-9k) is a member of intracellular calcium binding proteins, which have a high affinity to calcium. CaBP-9k is mainly expressed in the mammalian intestine, uterus and placenta, and is regulated in tissue- and species-specific manners. Previous studies have shown that CaBP-9k expression is mainly controlled by steroid hormones and their receptors. Thus, we further investigated the expression and regulation of CaBP-9k during an estrus cycle in the pig uterus by Northern blot and immunoblot analysis in this study. In addition, serum levels of estrogen (E2) and progesterone (P4) were measured using ELISA. The CaBP-9k mRNA is highly expressed in the porcine uterus during a luteal phase compared to a follicular phase, and its mRNA level in a luteal phase is increased up to 10-fold compared to a follicular phase. In parallel to the level of CaBP-9k mRNA, the CaBP-9k protein is also dominantly expressed in the porcine uterus, and strongly expressed in the epithelium and glands of the porcine uterus during a luteal phase. Although, the localization of the CaBP-9k protein is scarcely detected at follicular phase, it is dominantly expressed in the porcine uterus during a luteal phase. In addition, the serum P4 level was significantly increased during a luteal phase compared to a follicular phase, whereas no difference was observed in E2 levels between follicular and luteal phases, indicating that the ratio of P4/E2 is remarkably increased in porcine uterus during a luteal phase compared to a follicular phase. In conclusion, these results suggest that P4 may play an important role in the up-regulation of CaBP-9k gene in the porcine uterus in a luteal phase, which is unlike the condition in the rat uterus. In addition, the porcine CaBP-9k may be dominantly expressed in the epithelium and glandular structure of pig uterus during a luteal phase. It may also be differentially regulated during this cycle presumably by steroid hormones, especially up-regulated P4 levels in this tissue.

Control of growth and differentiation of the endometrium: the role of tissue interactions

Early work with neonatal mice showed that estrogen receptor-negative uterine epithelium responded to estrogen treatment. Since the underlying mesenchymal cells were estrogen receptor-positive, it was suggested that these cells mediated the hormonal response through elaboration of a paracrine factor. Cell culture work showed that mesenchymal cells produced soluble factors that stimulate uterine epithelium, but hormonal regulation was absent or minimal. The paracrine hypothesis of estrogen action has been proved by the use of tissue recombinant studies in which epithelium from estrogen receptor-alpha knockout mice was combined with wild-type mesenchyme; estrogen stimulated the ER alpha-negative epithelium if the underlying stromal cells were receptor-positive. Also, it is hypothesized that there is a reciprocal paracrine interaction during stimulation with progesterone and estrogen. Accordingly, under progesterone dominance, the epithelium elaborates factors that direct the underlying stroma to proliferate when estrogen is administered. Although this hypothesis needs further testing, it has been shown that the uterine epithelium is required for stromal responsiveness to hormones. The question arises: What are the factors that mediate the effects of the steroid hormones in the uterus? Several peptide growth factors are regulated by estrogen and/or progesterone. Use of knockout animals will allow a determination of the role that these factors play in the uterus. However, ablation of many of these growth factor genes has proved lethal to the newborn animals, making it impossible to study hormonal effects using standard techniques. Tissue xenograft and tissue recombination studies offer a means of defining the role of specific growth factors in uterine physiology.

Regulation of cyclooxygenase gene expression in rat endometrial stromal cells: the role of epidermal growth factor

Epidermal growth factor stimulates prostaglandin production and cyclooxygenase activity in endometrial stromal cells isolated from the uteri of ovariectomized rats sensitized for the decidual reaction. The present study examined the effect of epidermal growth factor on cyclooxygenase-1 and cyclooxygenase-2 mRNA and protein levels in these cells. Treatment with epidermal growth factor (40 ng/ml) for 24 hr increased steady-state cyclooxygenase-1 and cyclooxygenase-2 mRNA and protein levels in the cells as determined by Northern and Western analyses. Dexamethasone inhibited the epidermal growth factor-induced increased in steady-state mRNA levels fro cyclooxygenase-2, but not for cyclooxygenase-1. Finally, the effects of epidermal growth factor and dexamethasone on steady-state cyclooxygenase-1 and cyclooxygenase-2 mRNA levels paralleled the changes in the levels of immunocytochemical staining for these enzymes in the cells. This showed that the changes in cyclooxygenase-1 and -2 protein levels were due to generalized changes in most cells, and not to changes in a subpopulation of stromal cells. The results of this study suggest that epidermal growth factor causes an increase in cyclooxygenase-1 and cyclooxygenase-2 gene expression in endometrial stromal cells isolated from the uteri of rats which have been sensitized for decidualization, and that the previously reported transcriptional- and translational-dependent increases in cyclooxygenase activity in these cells in response to epidermal growth factor were likely due to its effect on cyclooxygenase-1.

Preimplantation development of the mammalian embryo and its regulation by growth factors

Preimplantation development in mammals involves both the development of the embryo and the preparation of the uterus in anticipation of blastocysts implantation. Preparation of the uterus for implantation is primarily under the control of the ovarian sex steroids, estrogen and progesterone. Increasing evidence is revealing that their effects on cell proliferation and differentiation in the uterus are medicated by locally produced growth factors and cytokines. In contrast, preimplantation development of the embryo to the blastocyst stage appears to be independent of exogenous growth factors. Implantation, the point at which the blastocyst forms a more intimate association with the maternal tissues, is regulated by the uterine expression of leukemia inhibitory factor (LIF). LIF is required both to promote embryo attachment and for decidualization of the uterus. In the absence of LIF, neither of these events occur. Uterine expression of LIF at the time of implantation has been described in many species, suggesting that LIF may be of general significance in regulating embryo implantation in mammals.

Epidermal growth factor and basic fibroblast growth factor increase the production of matrix metalloproteinases during in vitro decidualization of rat endometrial stromal cells

Numerous growth factors are involved in mediating proliferation and differentiation of endometrial stromal cells during decidualization. During this period, the extracellular matrix of the endometrium undergoes extensive remodeling. We tested the hypothesis that epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), and transforming growth factor-beta regulate expression of matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs), during decidualization. Stromal cells were isolated from uteri hormonally sensitized to undergo decidualization and were cultured in the absence or presence of a growth factor. Using substrate-gel electrophoresis with gelatin as the substrate, we detected activity for gelatinase A and B, and collagenase-3, and using casein as a substrate, we detected activity for stromelysin-1. Increasing concentrations of EGF and bFGF resulted in increased activity of gelatinase B, collagenase-3, and stromelysin-1. Northern blot analyses revealed that EGF and bFGF also increased messenger RNA levels for these MMPs. There was no effect of these growth factors on gelatinase or TIMP-1, -2, and -3, nor was there an effect of transforming growth factor-beta on any MMP or TIMP examined. These data demonstrate that EGF and bFGF increase levels of proteolytic enzymes produced by endometrial stromal cells undergoing decidualization in vitro while having no effect on their inhibitors.

TNF-alpha regulates transforming growth factor-alpha expression in regenerating murine liver and isolated hepatocytes

TNF-alpha is a pleotropic proinflammatory cytokine that has been implicated as a contributing factor in a number of disease processes, primarily through its ability to induce the expression of inflammatory and cytotoxic mediators. TNF-alpha is also involved in cell growth accompanying the healing process in multiple organ systems and influences liver repair following hepatotoxic damage or regeneration following partial hepatectomy. In this respect, TNF-alpha is a known mitogen for hepatocytes. In this paper we describe a novel role for TNF-alpha in the modulation of expression of TGF-alpha, the latter being a complete hepatocyte mitogen. TNF-alpha directly up-regulates TGF-alpha mRNA by up to 7-fold in isolated mouse hepatocytes, whereas neutralization of TNF-alpha significantly decreased liver mRNA and protein expression of TGF-alpha following chemical-induced hepatotoxicity. That TNF-alpha directly stimulated TGF-alpha was suggested by the inability of either anti-IL-6 Abs or cycloheximide to inhibit TNF-alpha-induced TGF-alpha expression in hepatocytes. However, in the presence of anti-TGF-alpha neutralizing Abs, the mitogenic activity of TNF-alpha is abrogated. Using cells transfected with the TGF-alpha promoter, and an RNA polymerase inhibitor, it was shown that TNF-alpha modulates TGF-alpha expression through both pre- and posttranscriptional events. Taken together, these data suggest that TNF-alpha participates in liver repair and regeneration, in part, by directly inducing the expression of TGF-alpha.

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.

Regulation of cytosolic phospholipase A2 in rat endometrial stromal cells: the role of epidermal growth factor

The effect of epidermal growth factor on the levels of cytosolic phospholipase A2 mRNA and protein in cultured rat endometrial stromal cells isolated from uteri sensitized for the decidual cell reaction was examined. Treatment with epidermal growth factor increased the steady-state cytosolic phospholipase A2 mRNA and protein levels as demonstrated by Northern and Western blot analyses, respectively. Immunocytochemical analysis demonstrated an increase of cytosolic phospholipase A2 protein in most cells, as opposed to a small subpopulation of cells in culture. These results show that epidermal growth factor causes an increase in steady-state cytosolic phospholipase A2 mRNA and protein levels in rat endometrial stromal cells from uteri sensitized for the decidual cell reaction. Epidermal growth factor receptor ligands may regulate cytosolic phospholipase A2 and thus prostaglandin production in the endometrial stromal cells during implantation.

Evidence of juxtacrine signaling for transforming growth factor alpha in human endometrium

To determine the mechanism of signaling for transforming growth factor alpha (TGFalpha) in human endometrium, uterine luminal fluid proteins were retrieved by lavage followed by collection of the adjacent endometrium at hysterectomy. In the endometrium we observed the presence of the full-length transmembrane TGFalpha protein and the phosphorylation of its only known receptor, the epidermal growth factor receptor (EGFR), by immunoprecipitation-Western blot; TGFalpha mRNA via reverse transcription-polymerase chain reaction; and immunolocalization of TGFalpha to the surface endometrium adjacent to the uterine lumen. Despite this demonstration of TGFalpha in functional endometrium, we could not detect measurable amounts of TGFalpha in any of the 16 endometrial washings by either immunoprecipitation-Western blot or by ELISA. Recovery rate for intraluminal fluid spiked with TGFalpha control peptide was 93.4-97%. The inability to detect TGFalpha in intraluminal fluid despite its high concentration in cells directly adjacent to the uterine lumen, along with the absence of any cleaved TGFalpha species identified in the endometrium, suggests that TGFalpha signals its receptor as a transmembrane ligand. Since the EGFR is present in the endometrium and on the surface of embryos, these data are consistent with a juxtacrine mode of signaling for TGFalpha between endometrial cells, and between the luminal surface epithelium and preimplantation embryos.

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.

Localization of connective tissue growth factor during the period of embryo implantation in the mouse

A role for connective tissue growth factor (CTGF) in reproductive function has been suggested from recent studies in the pig. To extend these findings, we have analyzed the immunohistochemical localization of CTGF during the estrous cycle and early pregnancy in mice. During the diestrous and early proestrous stages, CTGF was localized at high levels to both luminal and glandular uterine epithelial cells and at much lower levels in the stroma or myometrium. Epithelial expression of CTGF was considerably reduced at estrus. On Days 1.5-3.5 of pregnancy, CTGF was localized mainly to the uterine epithelial cells, which showed a substantially reduced level of CTGF on Day 4.5. On Days 5.5 and 6.5, CTGF was present at high levels in uterine decidual cells. CTGF was detected in the trophectoderm and inner cell mass of the preimplantation embryo on Day 4.5 and became preferentially localized to embryonic endoderm and mesoderm on Days 5.5-6.5. Multiple mass forms of CTGF (Mr 14 000-38 000) were present in endometrial extracts and uterine luminal flushings. Collectively, these data support a role for CTGF in uterine cell growth, migration, adhesion, and extracellular matrix production during the estrous cycle and early pregnancy, as well as in early development of the embryo.

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.

Regulation of plasminogen activator in rat endometrial stromal cells: the role of epidermal growth factor

The effect of epidermal growth factor (EGF) on the accumulation of plasminogen activator (PA) activity in the medium of cultured rat endometrial stromal cells isolated from uteri sensitized for the decidual cell reaction was examined. Treatment with EGF increased, in a concentration-dependent manner, PA activity in the medium. This effect was inhibited or greatly reduced by inhibitors of transcription and translation. Incubation of the cells with prostaglandin E2 increased PA activity in the medium. Indomethacin, which inhibited prostaglandin accumulation in the medium, slightly but significantly decreased the EGF-induced increase in PA activity in the medium. As indicated by zymography and the use of amiloride in the PA assay, the activity in the medium was primarily urokinase-type plasminogen activator (uPA). Finally, EGF caused an increase in the steady-state uPA mRNA levels in the cells. These results provide evidence that EGF causes an increase in the secretion of uPA by rat endometrial stromal cells from uteri sensitized for the decidual cell reaction through a mechanism that involves an increase in steady-state uPA mRNA levels.

Uterine and vaginal organ growth requires epidermal growth factor receptor signaling from stroma

Estrogens are crucial for growth and function of the female genital tract. Recently, we showed that induction of uterine epithelial proliferation by estradiol is a paracrine event requiring an estrogen receptor-positive stroma. Growth factors [such as EGF (epidermal growth factor) ligands] are likely paracrine mediators, which may directly or indirectly regulate epithelial proliferation in estrogen target organs via cell-cell interactions. In this report, we used mice with a null mutation in their EGF receptor (EGFR) to examine the role of EGFR signaling in growth of the uterus and vagina and in estrogen-induced uterine and vaginal epithelial proliferation. When WT and EGFR-knockout (EGFR-KO) uteri and vaginae were grown as renal capsule grafts in nude mice, growth of uterine and vaginal grafts of EGFR-KO mice was reduced, compared with their WT counterparts. Grafts of both EGFR-KO uteri and vaginae were about one third smaller (wet weight) than their corresponding WT organs, even though differentiation of both epithelium and mesenchyme were normal in both cases. Both wild-type and EGFR-KO vaginal grafts contained within their lumina alternating layers of cornified and mucified epithelial cell layers, indicating cyclic alteration of epithelial differentiation. In response to estradiol treatment, stromal cell labeling index (LI), as assessed by incorporation of 3H-thymidine, was severely depressed in EGFR-KO uterine and vaginal grafts vs. stromal cell LI in WT uterine and vaginal grafts. Unexpectedly, epithelium of both EGFR-KO and wild-type grafts responded comparably to estradiol with a marked elevation (approximately 7-fold overall) of epithelial LI in response to estradiol in uterine and vaginal epithelia. These data supported the hypothesis that overall uterine and vaginal organ growth, in response to estrogen, required EGFR signaling for DNA synthesis in the fibromuscular stroma, whereas EGFR signaling was not essential for estrogen-induced epithelial growth in the uterus and vagina.

Increased cell death in rat blastocysts exposed to maternal diabetes in utero and to high glucose or tumor necrosis factor-alpha in vitro

The morphogenetic function of the transient phase of cell death that occurs during blastocyst maturation is not known but it is thought that its regulation results from a delicate balance between survival and lethal signals in the uterine milieu. In this paper, we show that blastocysts from diabetic rats have a higher incidence of dead cells than control embryos. Differential lineage staining indicated that increased nuclear fragmentation occurred mainly in the inner cell mass. In addition, terminal transferase-mediated dUTP nick end labeling (TUNEL) demonstrated an increase in the incidence of non-fragmented DNA-damaged nuclei in these blastocysts. Analysis of the expression of clusterin, a gene associated with apoptosis, by quantitative reverse transcription-polymerase chain reaction detected an increase in the steady-state level of its transcripts in blastocysts from diabetic rats. In situ hybridization revealed that about half the cells identified as expressing clusterin mRNA exhibited signs of nuclear fragmentation. In vitro experiments demonstrated that high D-glucose increased nuclear fragmentation, TUNEL labeling and clusterin transcription. Tumor necrosis factor-alpha (TNF-alpha), a cytokine whose synthesis is up-regulated in the diabetic uterus, did not induce nuclear fragmentation nor clusterin expression but increased the incidence of TUNEL-positive nuclei. The data suggest that excessive cell death in the blastocyst, most probably resulting from the overstimulation of a basal suicidal program by such inducers as glucose and TNF-alpha, may be a contributing factor of the early embryopathy associated with maternal diabetes.

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.

Specificity of antibodies against rodent transforming growth factor-alpha protein

We found that the immunohistochemical distribution of TGF-alpha varied in rodent tissues depending on the antibody used, suggesting that the specificity of anti-TGF-alpha antibodies differs significantly. To address this issue, we compared the specificity of two representative antibodies that have been widely used to detect rodent TGF-alpha. In a competition study, the antibodies were preincubated with an excess of synthetic rat TGF-alpha 34-50 and were used for staining of rat and mouse kidneys and/or uterus. The results revealed that one of the antibodies, anti-rat TGF-alpha polyclonal antibody, was neutralized by the peptide, whereas the other, anti-human TGF-alpha monoclonal antibody, was not absorbed by the peptide up to an excess of 100-fold. Western blotting analysis showed that the anti-rat TGF-alpha polyclonal antibody recognized both human and rat purified TGF-alpha. However, the anti-human TGF-alpha monoclonal antibody did not detect purified rat TGF-alpha, although the antibody reacted with mouse proteins other than TGF-alpha from kidneys and uterus, purified human TGF-alpha, and mouse carbonic anhydrase II. These data indicate that the anti-human TGF-alpha monoclonal antibody does not recognize rodent TGF-alpha under our experimental conditions and suggest that distribution of TGF-alpha in rodent tissues may need to be reexamined.

Evidence for the involvement of transforming growth factor-alpha in implantation in the rat

This study was conducted to examine the possibility for participation of transforming growth factor-alpha (TGF-alpha), one of the epidermal growth factor (EGF) family of growth factors, in implantation in the rat. Immunostaining of TGF-alpha in the periimplantation uterus showed distinct staining in the luminal and glandular epithelium and moderate staining in stromal and myometrial cells. After implantation decidual cells and embryos were also positive stained for immunostaining. Immunocytochemistry of EGF receptor showed distinct staining in the luminal and glandular epithelium during the preimplantation period, and after implantation decidua at implantation sites and embryos were stained. Intraluminal injection of anti-TGF-alpha antibodies into uterine horns at 0600 h on day 5 of pregnancy decreased the number of rats showing implantation (blue dye reaction) at 0200 h on day 6 in a dose-dependent manner. Intraluminal injection of 100 pg of TGF-alpha on day 5 of pseudopregnancy elicited a greater decidual response when compared with the vehicle-injected contralateral uterine horn. Intraluminal injection of 20 pg of TGF-alpha into each uterine horn induced implantation in 50% of the ovariectomized progesterone-treated delayed implanting rats. These results suggest that TGF-alpha is involved in the implantation process in the rat.

Secretion of unprocessed human surfactant protein B in milk of transgenic mice

Because of the apparent clinical importance of human pulmonary surfactant B (SP-B), the expression of SP-B was directed to the mammary gland of transgenic mice using previously characterized rat whey acidic protein (WAP) regulatory sequences. rWAP/SP-B mRNA was expressed specifically in the mammary gland, and ranged from 1 to 5% of the endogenous WAP mRNA levels. SP-B was detected immunologically in both tissue and milk. The transgene product had an apparent molecular weight of 40-45 kDa, corresponding to the predicted size of the SP-B proprotein. Incubation of an SP-B-enriched fraction of milk with cathepsin D in vitro produced 20-25 kDa species, consistent with cleavage of the amino terminal domain by cathepsin D. This was confirmed using antibodies specific to the carboxy-terminal domain of SP-B. However, the appearance of only the SP-B proprotein in milk suggests that cathepsin D is not involved in the in vivo processing of SP-B. The SP-B proprotein in milk suggests that cathepsin D is not involved in the in vivo processing of SP-B. The SP-B proprotein can be expressed in milk of transgenic mice without any observed effects on mammary gland morphology or lactation.

Differential hormonal regulation of leukemia inhibitory factor (LIF) in rabbit and mouse uterus

Leukemia inhibitory factor (LIF) has been shown to be essential for the implantation of mouse blastocysts. The present study was designed to determine how LIF protein was hormonally regulated in rabbit and mouse uterus using immunohistochemistry. In unmated rabbits, LIF protein was at a low level in the uterine epithelium and glands, and up-regulated by progesterone alone or estradiol-17 beta and progesterone combined. Estradiol-17 beta alone had no apparent effect. In ovariectomized mice, the level of LIF protein was very low in the uterine epithelium and glands, and was up-regulated by estradiol-17 beta alone or estradiol-17 beta and progesterone combined. Progesterone alone had no apparent effect. These results suggest that LIF protein is differentially regulated in rabbit and mouse uterus by progesterone and estrogen, respectively. This would explain the high level of LIF protein observed in uterine epithelium and glands prior to blastocyst implantation in the two species with different hormonal requirements for implantation.

Mouse preimplantation blastocysts adhere to cells expressing the transmembrane form of heparin-binding EGF-like growth factor

Previous studies have shown that heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) mRNA is synthesized in the mouse uterine luminal epithelium temporally, just prior to implantation, and spatially, only at the site of blastocyst apposition (Das, S. K., Wang, X. N., Paria, B. C., Damm, D., Abraham, J. A., Klagsbrun, M., Andrews, G. K. and Dey, S. K. (1994) Development 120, 1071–1083). HB-EGF is synthesized as a transmembrane protein (HB-EGF TM) that can be processed to release the soluble growth factor. An antibody that cross-reacts only with the transmembrane form detected HB-EGF TM in uterine luminal epithelium in a spatial manner similar to that of HB-EGF mRNA. HB-EGF TM is a juxtacrine growth factor that mediates cell-cell contact. To ascertain if HB-EGF TM could be an adhesion factor for blastocysts, a mouse cell line synthesizing human HB-EGF TM was co-cultured with mouse blastocysts. Cells synthesizing HB-EGF TM adhered to day-4 mouse blastocysts more extensively than parental cells or cells synthesizing a constitutively secreted form of HB-EGF. Adhesion of cells synthesizing HB-EGF TM to blastocysts was inhibited by excess recombinant HB-EGF but less so by TGF-alpha. Adhesion was also inhibited by the synthetic peptide P21 corresponding to the HB-EGF heparin binding domain, and by incubating the blastocysts with heparinase. In addition, adhesion to delayed implanting dormant blastocysts, which lack EGF receptor (EGFR), was diminished relative to normal blastocysts. These results suggested that adhesion between blastocysts and cells synthesizing HB-EGF TM was mediated via interaction with both blastocyst EGFR and heparan sulfate proteoglycan (HSPG). It was concluded that HB-EGF TM, which is synthesized exclusively in the luminal epithelium at the site of blastocyst apposition, and which is a juxtacrine adhesion factor for blastocysts, could be one of the mediators of blastocyst adhesion to the uterus in the process of implantation.

Epidermal growth factor receptor function in early mammalian development

We review here the data indicating a role for epidermal growth factor receptor (EGF receptor) signalling in early mouse development. Embryonic development of the metazoan embryo generally begins with the formation of a cystic structure and epithelial layers that subsequently form anlagen of the definitive body parts and organs. For the mammalian embryo, this cystic structure is a blastocyst whose wall consists of trophectoderm, the first epithelium to develop during mammalian embryogenesis. The onset of expression and function of EGF receptors is coincident with the onset of trophectoderm development. Modulating EGF receptor expression and function modulates trophectoderm differentiation, leading to the hypothesis that functional EGF receptors participate in the induction of trophectoderm development and perhaps of other embryonic epithelial derivatives such as nervous tissues.

Opposite effects of transforming growth factor alpha and epidermal growth factor on mouse placental lactogen I secretion

This study was undertaken to determine whether transforming growth factor alpha (TGF-alpha) regulates the production of mouse placental lactogen I (mPL-I) and mPL-II in a manner that is similar to that of epidermal growth factor (EGF), which was previously shown to stimulate mPL-I secretion and inhibit mPL-II secretion. In contrast to the activity of EGF, human (h) and rat (r) TGF-alpha (each at 100 ng/ml) inhibited secretion of mPL-I by placental cells isolated from mice on day 7 of pregnancy. Maximum inhibition of mPL-I secretion occurred on the third day of a 5-day culture period and ranged between 37% and 56% in multiple trials. Incubation of cells with hTGF-alpha and EGF was not followed by a change in the mPL-I concentration of the medium, suggesting the peptides antagonized each other's effects. hTGF-alpha and rTGF-alpha inhibited secretion of mPL-II; maximum inhibition ranged between 62% and 84% in multiple trials. The lowest concentrations of hTGF-alpha that affected mPL-I and mPL-II secretion were 10 ng/ml and 1 ng/ml, respectively. EGF and hTGF-alpha bound to the same receptors on placental cells, as assessed by cross-linking, and both peptides stimulated receptor phosphorylation, as assessed by Western blot analysis. There are three types of mPL-containing cells in placental cultures: cells that contain only mPL-I, cells that contain only mPL-II, and cells that contain both mPLs. The percentage of each type of mPL-containing cell in the culture was determined by immunostaining. hTGF-alpha affected the differentiation of the subpopulations of PL-containing cells in a manner that differed from that of EGF. The data suggest that TGF-alpha and EGF do not regulate the production of mPL-I and mPL-II in a similar manner.

Heparin-binding EGF-like growth factor gene is induced in the mouse uterus temporally by the blastocyst solely at the site of its apposition: a possible ligand for interaction with blastocyst EGF-receptor in implantation

Heparin-binding EGF-like growth factor (HB-EGF) is a newly discovered member of the EGF family of growth factors. HB-EGF can bind to two loci on cell surfaces, heparan sulphate proteoglycans and EGF-receptor (EGF-R), and either one or both of these interactions could play a role in cell-cell interactions. In the rodent, increased endometrial vascular permeability at the site of blastocyst apposition is considered to be an earliest discernible prerequisite event in the process of implantation and this event coincides with the initial attachment reaction between the blastocyst trophectoderm and uterine luminal epithelium. This investigation demonstrates that the HB-EGF gene is expressed in the mouse uterine luminal epithelium surrounding the blastocyst 6–7 hours before the attachment reaction that occurs at 2200–2300 hours on day 4 of pregnancy. It was further demonstrated that this gene is not expressed in the luminal epithelium at the site of the blastocyst apposition during the progesterone-maintained delayed implantation, but is readily induced in the luminal epithelium surrounding an activated blastocyst after termination of the delay by an estrogen injection. In vitro studies showed that HB-EGF induced blastocyst EGF-R autophosphorylation, and promoted blastocyst growth, zona-hatching and trophoblast outgrowth. These results suggest possible interactions between the uterine HB-EGF and blastocyst EGF-R very early in the process of implantation, earlier than any other embryo-uterine interactions defined to date at the molecular level.