Epidermal growth factor binding in rat uterus during the peri-implantation period

Effect of epidermal growth factor on preimplantation development and its receptor expression in porcine embryos

The present study aimed to determine the influence of exogenous epidermal growth factor (EGF) on in vitro preimplantation porcine embryo development and its mRNA expression for EGF receptor (EGFR). Oocytes were aspirated from abattoir ovaries, selected and cultured in defined, protein-free media for 44 hr before in vitro fertilization (IVF). Thirty-six hours after IVF, two-cell stage embryos were selected and treated or cultured until embryo treatment. In experiment 1, compact morulae were selected on day 4 after IVF and randomly allocated into 5 groups: NCSU 23 with PVA as group 1; NCSU 23 with PVA and 0.1 ng/ml, 1.0 ng/ml, 10.0 ng/ml EGF as group 2, 3, 4, respectively; NSCU 23 with 0.4% BSA as group 5. In experiment 2, treatment groups were the same as in experiment 1 except that 0.1% crystallized BSA was added to both washing media and all treatment groups instead of PVA. In experiments 3 and 4, two-cell stage embryos were treated and cultured in the same experimental design as experiments 1 and 2, respectively. RT-PCR was used to detect the mRNA expression of EGF receptor in compact morulae and blastocysts. The PCR products were subjected to direct DNA sequencing. There was no significant improvement in the development rate of embryos from compact morulae to blastocysts in the presence of various EGF concentrations (0.1, 1.0, 10.0 ng/ml) versus without EGF addition. They were all significantly lower than those embryos cultured in the continuous presence of 0.4% BSA. However, when a reduced concentration (0.1%) of crystallized BSA was added to all the treatment groups, a significantly lower rate of embryo development was observed in control media (NCSU23 with 0.1% crystallized BSA) compared with those developed in culture media with 0.4% BSA. With the addition of EGF at 10 ng/ml (with 0.1% BSA), embryo development rates were significantly improved over the control group (P < 0.05) and were as good as those rates in 0.4% BSA culture group. When embryos were selected and treated from the 2-cell stage, they did not develop to blastocyst stages after five more days' culture without any protein (BSA) or growth factor addition. When 0.1% BSA was included in the media, blastocyst formation rates were significantly improved by EGF addition at the concentration of both 1.0 or 10 ng/ml (P < 0.05) as compared to 0.0 or 0.1 ng/ml. EGFR mRNA was detected in both compact morulae and blastocyst stages of porcine embryos and confirmed by direct DNA sequencing. Our results indicate that IVM-IVF porcine embryo developmental rates could be improved by the addition of EGF in the culture media with the presence of a reduced amount of defined BSA (>97% albumin). However, EGF alone was not able to elicit any stimulatory effects on embryo development in the absence of protein supplementation. Further studies are needed to investigate the potential synergistic factors in embryo culture media to eventually define the porcine embryo culture media.

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.

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.

The effects of heparin-binding epidermal growth factor-like growth factor on preimplantation-embryo development and implantation in the rat

This study examined the effects of heparin-binding epidermal growth factor-like growth factor (HB-EGF) on preimplantation-embryo development and initiation of implantation in the rat. In vitro studies showed that HB-EGF improved the development of 8-cell embryos to the blastocyst stage in a concentration-dependent manner, and the growth factor had no effect on the cell number of the blastocyst developed. Intraluminal injection of an anti-HB-EGF antiserum into the uterine horns at 0600 h on day 5 of pregnancy decreased the number of implantation sites (blue dye reaction) at 0200 h on day 6. Intraluminal injection of 20 microl of HB-EGF solution (10 or 100 ng/ml) into each uterine horn induced implantation in about half of the ovariectomized progesterone-treated delayed implanting rats, and the number of implantation sites per rat increased dose-dependently. These results suggest that HB-EGF is involved in the preimplantation-embryo development and initiation of implantation in the rat.

Non-identical distribution pattern of epidermal growth factor and platelet-derived growth factor in the mouse uterus during the oestrous cycle and early pregnancy

In the present study, we examined by immunohistochemistry the cell-specific distribution of epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) in the mouse uterus during the oestrous cycle and throughout the first 7 days of pregnancy. Paraffin-embedded tissue samples were immunostained using the avidin-biotin peroxidase technique and then examined by light microscopy. Our results showed that immunostaining for EGF was detected in the stroma but not in the luminal or glandular epithelium. A high concentration of EGF was detected in the stroma around the time of embryo implantation at days 3, 4 and 5 of pregnancy. The implanted embryo at day 7 of gestation showed immunostaining for EGF between the ectoderm and endoderm layers. The cell distribution pattern for PDGF was found to be different from that observed with EGF. Luminal and glandular epithelia displayed PDGF immunostaining throughout the first 7 days of pregnancy, with the highest intensity at days 4 and 5 of gestation. In contrast, no immunostaining was observed in the luminal and glandular epithelia at post-oestrus, dioestrus and pro-oestrus stages. However, a weak reaction started to appear at oestrus. The embryo at the blastocyst stage displayed a strong immunoreaction for antibody against PDGF. In addition, the decidual boundary zone surrounding the implanted embryo at days 5, 6 and 7 of gestation also showed an immunostaining for PDGF. The present observations demonstrate clearly the presence of EGF and PDGF in the mouse uterus in high concentrations at the peri-implantation period. Thus, our results, together with what is known about the effect of EGF and PDGF in controlling the growth, differentiation and activation of a variety of cell types, suggest a possible role for these growth factors during the preparation of the endometrium for implantation in controlling the proliferation activity of stromal and/or epithelial cells.

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.

EGF, TGF-alpha and EGFR expression in human preimplantation embryos

Epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) through their common receptor, epidermal growth factor receptor (EGFR) are known to enhance mitogenesis, development and implantation in several species. In the mouse, co-culture of grouped embryos in microdrops increases the cell number and proportion developing to the blastocyst stage. A similar effect is observed with culture of single embryos in medium supplemented with EGF or TGF-alpha highlighting their embryotrophic effects. To study the role of EGF, TGF-alpha and EGFR in early human development, two methods applicable for analysis of expression at the single embryo level have been employed. In the first method, reverse transcription-polymerase chain reaction has been used to examine the presence of transcripts. Following reverse transcription, strategically designed nested primers, optimised for specificity, were used for amplification from the cDNA equivalent of a single embryo. The products were then verified by restriction enzyme digestion and sequence analysis. In the second method, immunocytochemistry has been used to colocalise the expressed proteins. Individual embryos were paraffin embedded and serial sectioned, allowing adjacent sections to be examined with different antibodies and controls. Monoclonal TGF-alpha and polyclonal EGF and EGFR primary antibodies were used. Staining was performed by peroxidase-conjugated avidin-biotin immunocytochemistry with the appropriate controls. The combination of these two methods can potentially be used for simultaneous analysis of several growth factors and/or their receptors in the same human embryos. Transcripts for EGF, TGF-alpha and EGFR were detected in unfertilized oocytes and embryos between 8-cell and blastocyst stages on day 3 to 6 post-insemination.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidermal growth factor--induced implantation and decidualization in the rat

Effects of epidermal growth factor (EGF) on blastocyst implantation and experimentally-induced decidualization were examined in the rat. Intraluminal injection of EGF into each uterine horn induced implantation in the ovariectomized progesterone-treated delayed implanting rat in a dose-dependent manner. This induction was inhibited by indomethacin, an inhibitor of prostaglandin synthesis. Intraluminal injection of EGF on day 5 of pseudopregnancy elicited a greater decidual response when compared to the vehicle-injected contralateral uterine horn. These results suggest that EGF may play important roles in the process of implantation and decidualization in the rat.

Epidermal growth factor (EGF) replaces estradiol for the initiation of embryo implantation in the hypophysectomized rat

Several studies have provided evidence that epidermal growth factor (EGF) or transforming growth factor alpha (TGF alpha) mediate some of the physiological effects of estrogen. The object of the present study was to determine whether exogenous EGF could initiate embryo implantation in the rat, a response known to depend upon the action of estrogen in a progesterone-primed uterus. Immunocytochemical examination showed the presence of immunoreactive EGF, TGF alpha and the EGF receptor in luminal glandular epithelium of uteri on days 4,5 and 6 of pregnancy. EGF receptor was also present in the implanting embryo and in decidual cells of the uterine stroma. Attempts to initiate implantation by intravenous injection of murine EGF into ovariectomized or hypophysectomized delayed-implanting rats maintained with progesterone were unsuccessful. Implantation sites were found, however, in 24 of 33 (73 per cent) hypophysectomized progesterone-primed rats given 100 micrograms EGF immediately after intrauterine transfer of blastocysts from hypophysectomized delayed implanting animals. Although EGF is capable of initiating implantation in the delayed implanting rat model it remains to be determined whether this growth factor is responsible for the implantation inducing action of estrogen in vivo.

Gene expression in pre-implantation mammalian embryos

The pre-implantation mammalian embryo is initially under the control of maternal informational macromolecules that are accumulated during oogenesis. Subsequently, the genetic program of development becomes dependent upon new transcription derived from activation of the embryonic genome. Several embryonic transcripts including those that encode growth factors, cell junction components and plasma membrane ion transporters are required for normal progression of the embryo to the blastocyst stage. The pattern of genes expressed and the overall program of development is subject to the influences of genomic imprinting as well as external influences encountered by the embryo within the maternal reproductive tract.

Characterization of the epidermal growth factor receptor in preimplantation pig conceptuses

Embryos recovered from sows on Days 9-13 of pregnancy (Day 0 = first day of estrus) exhibited saturable and time-dependent specific binding of 125I-epidermal growth factor (EGF). The specific binding (pg/mg protein) was greater (P less than 0.001) for Day 13 elongated conceptuses than for conceptuses of earlier stages. Scatchard analyses showed two classes of binding sites (Kd = 7.0 +/- 2.6 x 10(-11) M, Bmax = 6.2 +/- 1.4 fmol/mg protein and Kd = 3.4 +/- 0.2 x 10(-8) M, Bmax = 420 +/- 80 fmol/mg protein). The EGF receptor in Day 13 conceptus membranes is a 170-kDa protein and was phosphorylated in the presence of EGF and adenosine triphosphate. EGF stimulated protein tyrosine kinase activity about 1.6-fold over basal levels. The results show that the preimplantation pig conceptus possesses EGF-binding sites with the properties of functional EGF-receptors.

Growth factors in the uterus: steroidal regulation and biological actions

Rapid progress has been made within the last 5-6 years in characterizing polypeptide growth factors in uterine tissues and fluids. There is convincing evidence that their synthesis and/or secretion is regulated by steroid hormones. The possibility that these growth factors play a central role in growth and development of the uterus or placenta is suggested by the presence of their receptors on uterine or placental cells and their stimulatory effects on these cells in vitro. Since growth factors interact synergistically and also have non-mitogenic functions, the presence of a variety of these factors in the uterus suggests that they probably regulate various aspects of uterine function through complex autocrine and paracine pathways. However, experimental models need to be designed that will permit a more detailed analysis of the actual role of these factors in utero. Fruitful approaches may be to administer neutralizing antibodies or blocking peptides so as to antagonize uterine growth factor action, or to develop appropriate transgenic animals. These and other lines of study should help us to understand the role of growth factors in development of the immature uterus, growth of the placenta or gravid uterus, repair and angiogenesis of the endometrium, and uterine pathology.

Reversal of indomethacin-induced inhibition of implantation in the mouse by epidermal growth factor

In the mouse, estriol (E3) can induce implantation as a phase I of estrogen action. E3-induced implantation was attenuated by indomethacin(INDO), an inhibitor of prostaglandin (PG) synthesis. The inhibitory effect of INDO was reversed by administration of epidermal growth factor (EGF), and this EGF effect was dose-dependent. These results suggest that one of the functions of estrogen could be to activate the EGF ligand-receptor signalling in the uterus in generating PGs required for initiation of implantation. This is consistent with the results of EGF stimulation of synthesis of PGs in uterine stromal cells in culture.

The role of EGF in testosterone-induced reproductive tract differentiation

EGF is known to modulate a variety of cellular functions including differentiation. The aim of this investigation was to determine the role of EGF in androgen-induced masculine differentiation. Accordingly, a series of experiments were designed and the results are summarized as described below. (1) We found that the specific deprivation of EGF using anti-EGF serum during the period of masculine differentiation in an organ culture bioassay system resulted in the disintegration of the Wolffian system in a dose-dependent manner. (2) Exogenous EGF supplemented in the above experiment corrected the anti-EGF effect, suggesting a specific role of EGF. (3) Anti-EGF serum was also found to disrupt the differentiation even in the presence of exogenous testosterone, suggesting an effect independent of testosterone synthesis. (4) EGF was found to have a direct masculinizing effect both in vivo and in vitro; however, it was not able to mimic all masculinizing effects of testosterone. The mesonephric segment of the Wolffian duct was retained by EGF in the female fetal tract under in vitro conditions, and under in vivo conditions EGF was able to increase anogenital distance and to induce epididymis in some female fetal mice. (5) We were able to detect an EGF-like material in the fetal genital tract during differentiation and found that the level of this material increased with advancement of differentiation. Thus, it appears from the above results that EGF plays a role in testosterone-induced reproductive tract differentiation.

Epidermal growth factor binding and receptor distribution in the mouse reproductive tract during development

The ontogeny of the epidermal growth factor (EGF) receptor in the different cell types in the neonatal and immature mouse uterus and vagina was examined. Immunohistochemical examination of prenatal and neonatal reproductive tracts with a polyclonal antibody to the EGF receptor shows immunoreactive EGF receptors as early as Day 13 of gestation. Autoradiographic analysis of tissue sections at 3 to 17 days of age (the day of birth is Day 1) demonstrates that both uterine and vaginal epithelial and stromal cells are capable of binding 125I-labeled EGF. Both the 125I-labeled EGF autoradiography and immunohistochemistry in whole tissue show higher EGF receptor levels in the uterine epithelium than the uterine stroma. The presence of EGF receptors was also confirmed by affinity labeling and Scatchard analysis of isolated uterine cell types at 7 and/or 17 days of age. However, in contrast to the autoradiography and immunohistochemistry data of intact tissue, the affinity labeling and Scatchard data of isolated cells indicate that the uterine stroma contains higher levels of EGF receptor than that of the uterine epithelium. The reason for this discrepancy between the different techniques is, as yet, unknown. Regardless of the differences in the actual numbers of EGF receptors obtained, our data demonstrate that the developing mouse reproductive tract contains immunoreactive EGF receptors that are capable of binding 125I-labeled EGF.

Immunohistochemical localization of epidermal growth factor receptor during implantation in the rabbit

Epidermal growth factor receptor was localized immunohistochemically during implantation (gestational days 7 through 14) in the rabbit. During early implantation (days 7 through 9), immunostaining was observed in the cytoplasm and on the surface of the syncytiotrophoblastic knobs. By day 8, immunoreactivity was most pronounced in knobs interacting directly with uterine epithelium but was noted in nonknob cytotrophoblast as well. Fetal membranes, identified by day 10, were stained intensely on all days examined. In later gestation the trophoblast was stained intensely on the surface and in the cytoplasm, with some staining over nuclei. No appreciable changes in the staining pattern were observed after day 10. Uterine epithelium demonstrated epidermal growth factor receptor staining first on the antimesometrial (day 7) and then the paraplacental epidermal (day 9). After day 10, most staining was at the embryo-maternal interphase. These data suggest that the embryo and uterine epithelia can receive signals from their environment during and after implantation through the epidermal growth factor receptor.