Inappropriate expression of human transforming growth factor (TGF)-alpha in the uterus of transgenic mouse causes downregulation of TGF-beta receptors and delays the blastocyst-attachment reaction

Chemerin Effect on the Endometrial Proteome of the Domestic Pig during Implantation Obtained by LC-MS/MS Analysis

Chemerin (CHEM) is a hormone mainly expressed in adipocytes involved in the regulation of energy homeostasis and inflammatory response. CHEM expression has been demonstrated in the structures of the porcine hypothalamic-pituitary-gonadal axis, as well as in the uterus, trophoblasts and conceptuses of pigs. In this study, we performed high-throughput proteomic analyses (liquid chromatography with tandem mass spectrometry, LC-MS/MS) to examine the influence of CHEM (400 ng/mL) on differentially regulated proteins (DRPs) in the porcine endometrial tissue explants during implantation (15 to 16 days of gestation). Among all 352 DRPs, 164 were up-regulated and 188 were down-regulated in CHEM-treated group. DRPs were assigned to 47 gene ontology (GO) terms (p-adjusted < 0.05). Validation of four DRPs (IFIT5, TGFβ1, ACO1 and PGRMC1) by Western blot analysis confirmed the veracity and accuracy of the LC-MS/MS method used in the present study. We suggest that CHEM, by modulating various protein expressions, takes part in the endometrial cell proliferation, migration and invasion at the time of implantation. It also regulates the endometrial immune response, sensitivity to P4 and the formation of new blood vessels. Additionally, CHEM appears to be an important factor involved in endothelial cell dysfunction during the pathogenesis of preeclampsia. The identification of a large number of DRPs under the influence of CHEM provides a valuable resource for understanding the molecular mechanisms of this hormone action during implantation, which is a prerequisite for better control of pig reproduction.

Dual role of TGF-β in early pregnancy: clues from tumor progression

TGF-β signaling in the endometrium is active during the implantation period and has a pivotal role in regulating endometrial receptivity and embryo implantation. During embryo implantation, both apoptosis and proliferation of endometrial cells happen at the same time and it seems TGF-β is the factor that controls both of these processes. As shown in cancer cells, in special conditions this cytokine can have a dual effect and switch the action from apoptosis to proliferation. Owing to the similarity between embryo implantation and cancer development and also unusual pattern of proliferation and remodeling in the uterus, in this review we suggest the existence of such a switching in endometrium during the early pregnancy. Moreover, we address some potential mechanisms that could regulate the switching. A better understanding of the molecular mechanisms regulating TGF-β action and signaling during the implantation period could pave the way for introducing novel therapeutic strategies in order to solve implantation-associated issues such as repeated implantation failure.

Bovine ovarian follicular growth and development correlate with lysophosphatidic acid expression

The basis of successful reproduction is proper ovarian follicular growth and development. In addition to prostaglandins and vascular endothelial growth factor, a number of novel factors are suggested as important regulators of follicular growth and development: PGES, TFG, CD36, RABGAP1, DBI and BTC. This study focuses on examining the expression of these factors in granulosa and thecal cells that originate from different ovarian follicle types and their link with the expression of lysophosphatidic acid (LPA), known local regulator of reproductive functions in the cow. Ovarian follicles were divided into healthy, transitional, and atretic categories. The mRNA expression levels for PGES, TFG, CD36, RABGAP1, DBI and BTC in granulosa and thecal cells in different follicle types were measured by real-time PCR. The correlations among expression of enzymes synthesizing LPA (autotaxin, phospholipase A2), receptors for LPA and examined factors were measured. Immunolocalization of PGES, TFG, CD36, RABGAP1, DBI and BTC was examined by immunohistochemistry. We investigated follicle-type dependent mRNA expression of factors potentially involved in ovarian follicular growth and development, both in granulosa and thecal cells of bovine ovarian follicles. Strong correlations among receptors for LPA, enzymes synthesizing LPA, and the examined factors in healthy and transitional follicles were observed, with its strongest interconnection with TFG, DBI and RABGAP1 in granulosa cells, and TFG in thecal cells; whereas no correlations in atretic follicles were detected. A greater number of correlations were found in thecal cells than in granulosa cells as well as in healthy follicles than in transitional follicles. These data indicate the role of LPA in the growth, development and physiology of the bovine ovarian follicle.

Placental overgrowth and fertility defects in mice with a hypermorphic allele of epidermal growth factor receptor

Epidermal growth factor receptor (EGFR) is a member of the ERBB family of receptor tyrosine kinases that has been shown to play an important developmental and physiologic role in many aspects of pregnancy. We have previously shown in mice that Egfr(tm1Mag) nullizygous placentas have fewer proliferative trophoblasts than wild-type and exhibit strain-specific defects in the spongiotrophoblast and labyrinth layers. In this study we used mice with the hypermorphic Egfr(Dsk5) allele to study the effects of increased levels of EGFR signaling on placental development. On three genetic backgrounds, heterozygosity for Egfr(Dsk5) resulted in larger placental size with a more prominent spongiotrophoblast layer and increased expression of glycogen cell-specific genes. The C3HeB/FeJ strain showed additional placental enlargement of Egfr(Dsk5) homozygotes with a significant number of homozygous embryos dying prior to 15.5 days post-coitus (dpc). We also observed strain-specific subfertility in Egfr(Dsk5) heterozygous females and pregnancy loss was dependent on maternal factors rather than embryo genotype. Higher levels of phospho-EGFR were detected in the uterus of Egfr(Dsk5) heterozygotes but the structure of Egfr(Dsk5) heterozygous nonpregnant uteri appeared similar to wild-type. Collectively, our results demonstrate that mice with increased levels of EGFR signaling exhibit an extensive level of genetic background-dependent phenotypic variability. In addition, EGFR promotes growth of the placental spongiotrophoblast layer in mice, and EGFR expressed in the uterine stroma may play an underappreciated role in preparation of the uterus for embryo implantation.

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.

Cytokines: Important for implantation?

PROBLEM

Cytokines are obviously very important in an established pregnancy, but what about human embryo implantation?

METHODS

Literature review.

RESULTS

We first discuss the necessity and limits of animal models, and then review the few cytokines which have been demonstrated by knock-out methods to be absolutely necessary for embryo implantation using in animal models. We then review what is known or discussed about the role of other cytokines as deduced from quantitative and/or qualitative dysregulation in animals and in humans.

CONCLUSIONS

Cytokines are indeed involved in implantation as they are in ongoing pregnancy and delivery. Relevance to infertility and recurrent pregnancy loss is discussed.

TGF-beta signaling is essential for joint morphogenesis

Despite its clinical significance, joint morphogenesis is still an obscure process. In this study, we determine the role of transforming growth factor beta (TGF-beta) signaling in mice lacking the TGF-beta type II receptor gene (Tgfbr2) in their limbs (Tgfbr2(PRX-1KO)). In Tgfbr2(PRX-1KO) mice, the loss of TGF-beta responsiveness resulted in the absence of interphalangeal joints. The Tgfbr2(Prx1KO) joint phenotype is similar to that in patients with symphalangism (SYM1-OMIM185800). By generating a Tgfbr2-green fluorescent protein-beta-GEO-bacterial artificial chromosome beta-galactosidase reporter transgenic mouse and by in situ hybridization and immunofluorescence, we determined that Tgfbr2 is highly and specifically expressed in developing joints. We demonstrated that in Tgfbr2(PRX-1KO) mice, the failure of joint interzone development resulted from an aberrant persistence of differentiated chondrocytes and failure of Jagged-1 expression. We found that TGF-beta receptor II signaling regulates Noggin, Wnt9a, and growth and differentiation factor-5 joint morphogenic gene expressions. In Tgfbr2(PRX-1KO) growth plates adjacent to interphalangeal joints, Indian hedgehog expression is increased, whereas Collagen 10 expression decreased. We propose a model for joint development in which TGF-beta signaling represents a means of entry to initiate the process.

Control of ErbB signaling through metalloprotease mediated ectodomain shedding of EGF-like factors

Epidermal growth factor (EGF)-like proteins comprise a group of structurally similar growth factors, which contain a conserved six-cysteine residue motif called the EGF-domain. EGF-like factors are synthesized as transmembrane precursors, which can undergo proteolytic cleavage at the cell surface to release a mature soluble ectodomain; a process often referred to as "ectodomain shedding". Ectodomain shedding of EGF-like factors has been linked to multiple zinc-binding metalloproteases of the matrix metalloprotease (MMP) and a disintegrin and metalloprotease (ADAM) families. Shedding can be activated by a variety of pharmacological and physiological stimuli and these activation events have been linked to the enhancement of metalloprotease activity, possibly via the action of intracellular signaling modules. Once shed from the cell surface, EGF-like factors bind to a family of four cell surface receptors named ErbB-1, -2, -3 and -4. Heterodimerization or homodimerization of these receptors following ligand binding drives intracellular signal transduction cascades, which eventuate in diverse cell fates including proliferation, differentiation, migration and inhibition of apoptosis. In addition to its role in driving normal developmental processes, a wealth of evidence now exists showing that de-regulated ErbB signaling is associated with the formation of tumors in a variety of tissues and that ectodomain shedding of EGF-like factors plays a critical event in this process. Thus, knowledge of the molecular mechanisms by which EGF-like factors are shed from the cell surface and the nature of the proteases and cellular signals that govern this process is crucial to understanding ErbB receptor signaling and potentially also in the development of novel cancer therapeutics targeting the ErbB pathway. This review focuses on the structure and function of EGF-like factors, and the mechanisms that govern the shedding of these transmembrane molecules from the cell surface.

Endometriotic Cells Exhibit Metaplastic Change and Oxidative DNA Damage as Well as Decreased Function, Compared to Normal Endometrium

A widely accepted theory of the etiology of endometriosis is that it originates from the implantation and invasion of cells from retrograde menstruation to various sites in the body particularly the pelvic peritoneal cavity. Little is known of the function of these cells in ectopic sites. Normal endometrium was compared with endometriotic tissue using an antibody to Placental Cadherin (P Cadherin), a recently studied cadherin that is implicated in metaplasia and early neoplasia and also 8-hydroxyguanine, an indicator of oxidative DNA damage. Comparisons of endometrial tissue function were made using expression of transforming growth factor beta-1 (TGFbeta-1) and insulin-like growth factor-I (IGF-I). There was no labelling for anti-P Cadherin or anti-8-hydroxydeoxyguanosine in normal endometrium but marked labelling for both on the apical surface of the endometriotic epithelium. Studies of markers of normal endometrial function were all de-expressed in endometriosis. This study indicates that endometriosis cells are abnormal and exhibit oxidative DNA damage, metaplasia and markedly reduced function compared to normal endometrium.

Expression of TGF-beta type II receptors in the olfactory epithelium and their regulation in TGF-alpha transgenic mice

Numerous in vitro studies of neurogenesis of olfactory receptor neurons (ORNs) suggest that transforming growth factor (TGF)-beta promotes the maturation/differentiation of olfactory progenitors. We demonstrate that in vivo both mature and immature ORNs, and possibly a basal neuronal progenitor cell, express the TGF-beta type II receptor (TGF-betaRII), suggesting that these cells are targets for TGF-beta signaling. In a previous study of neurogenesis in the OE of TGF-alpha overexpressing transgenic (T) mice, we observed an apparent reduction in the expression of olfactory marker protein (OMP), a marker of terminal differentiation in ORNs in T mice compared to nontransgenic (NT) littermate controls; this was confirmed by Western blotting and immunohistochemistry. In contrast, there was no apparent difference between T and NT mice in the intensity of immunoreactivity for a neuronal marker, protein gene product 9.5. Because TGF-alpha overexpression has been reported to affect TGF-beta signaling in other epithelia, we compared the expression of the TGF-beta type II receptor (TGF-betaRII) in T and NT mice. The intensity of TGF-betaRII immunoreactivity on ORNs was substantially reduced in T compared to NT mice. Similar reductions in TGF-betaRII expression in vomeronasal receptor neurons and in other epithelia in the nasal cavity of T mice were also observed. Taken together, these results indicate that TGF-beta signaling regulates terminal differentiation of ORNs in vivo and suggest ways in which interactions between TGF-alpha and TGF-beta signaling pathways may interact in the OE.

Temporal and spatial expression of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta type 1 (TGF-beta1) at the utero-placental interface during early pregnancy in the pig

AIMS

To determine the localisation and distribution of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta type 1 (TGF-beta1) in uterine tissues from cycling and early pregnant pigs.

METHODS

In situ hybridisation and immunohistochemistry were used to localise CCN2 (CTGF) or TGF-beta1 in uteri obtained from gilts on days 0, 5, 10, 12, 15, and 18 of the oestrous cycle or days 10, 12, 14, 16, 17, and 21 of gestation.

RESULTS

In cycling animals, CCN2 (CTGF) mRNA and protein were abundant in luminal epithelial cells (LECs) and glandular epithelial cells (GECs), with lesser amounts in stromal fibroblasts and little or none in endothelial cells. A similar pattern of staining was seen up to day 10 of pregnancy, except that overall staining intensities for CCN2 (CTGF) mRNA or protein were higher and that stromal and endothelial cells were CCN2 (CTGF) positive. However, on days 12-17 there was a striking decrease in the amount of CCN2 (CTGF) in LECs at the utero-conceptus interface, which was associated with maternal stromal matrix reorganisation and the onset of subepithelial neovascularisation. This differential distribution of CCN2 (CTGF) was localised to those LECs that were in close proximity to or in apposition with trophoblast cells. This decrease in CCN2 (CTGF) staining was transient in nature and high amounts of CCN2 (CTGF) were again apparent in LECs on days 17-21, when endometrial neovascularisation and matrix remodelling were complete. The expression of uterine TGF-beta1 was comparable to that of CCN2 (CTGF) at most stages of the oestrous cycle or early pregnancy. Pre-elongation blastocysts recovered on day 10 were positive for both CCN2 (CTGF) and TGF-beta1 in the extra-embryonic trophectoderm, endoderm, and inner cell mass. On day 12, trophectoderm expressed low amounts of TGF-beta1 mRNA and non-detectable amounts of TGF-beta1 protein or CCN2 (CTGF) mRNA or protein. By days 17-21, the expression of both growth factors in the extra-embyronic/placental membranes increased and frequently exceeded that seen in LECs.

CONCLUSIONS

The pattern of CCN2 (CTGF) production during the initial attachment phase supports a role for this factor in stromal remodelling and neovascularisation, although alternative functions at later stages such as epithelial-epithelial interactions are also possible. In most major cell types in the uterus or utero-placental unit, CCN2 (CTGF) expression was highly correlated with that of TGF-beta(1), indicating that CCN2 (CTGF) may mediate some of the functions of TGF-beta in the reproductive tract during the oestrous cycle and pregnancy. The data further highlight epithelium as an important source of CCN2 (CTGF) in the regulation of uterine function.

Steroidal regulation of connective tissue growth factor (CCN2; CTGF) synthesis in the mouse uterus

AIMS

To determine mechanisms regulating the production of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta1 (TGF-beta1) in the mouse uterus.

METHODS

In situ hybridisation and immunohistochemistry were used to localise CCN2 (CTGF) and TGF-beta1 in uteri from sexually mature female mice that had either been (1) mated with sterile males to induce pseudopregnancy or (2) ovariectomised (OVX) and administered estradiol-17beta (E2) or progesterone (P4), either alone or in combination. Uteri collected on days 0.5, 1.5, 2.5, 3.5, 4.5, or 5.5 of pseudopregnancy or at one, three, six, 12, or 24 hours after steroid administration were fixed, sectioned, and incubated with specific riboprobes or antibodies to permit detection and localisation of mRNA or protein for CTGF and TGF-beta1.

RESULTS

On days 0.5-2.5 of pseudopregnancy, CCN2 (CTGF) and TGF-beta1 were principally colocalised to uterine epithelial cells, with much smaller amounts in the stroma. On days 3.5-4.5, there was a reduction of CCN2 (CTGF) and TGF-beta1 in the epithelium but an increase in stromal and endothelial cells, corresponding to a period of extracellular matrix remodelling and neovascularisation within the endometrium. In OVX mice, epithelial cells were weakly positive for both CCN2 (CTGF) and TGF-beta1 in the absence of steroid hormones. Epithelial CTGF mRNA production were strongly but transiently stimulated in OVX mice cells by E2. These effects were antagonised by P4, which itself transiently stimulated epithelial CCN2 (CTGF) production, although less robustly than E2. CTGF and TGF-beta1 protein amounts were high in epithelial cells throughout steroid treatment and were increased in the stroma, where they were relatively long lived. Stromal CCN2 (CTGF) and TGF-beta1 were lower after co-administration of E2 and P4 than in response to each hormone individually. Although ccn2 (ctgf) is a TGF-beta1 inducible gene in other systems, and both growth factors were often co-localised in uterine tissues in these studies, several treatment regimens resulted in high amounts of TGF-beta1 protein in stromal cells without the concomitant production of ccn2 (ctgf) mRNA.

CONCLUSIONS

Maternal factors are principal cues for CCN2 (CTGF) and TGF-beta1 production in the uterus because (1) their expression during pseudopregnancy is comparable to that seen in pregnancy and (2) they are regulated by ovarian steroids. TGF-beta dependent and independent mechanisms of ccn2 (ctgf) gene transcription exist in the uterus that are variably regulated by steroid hormones. Collectively, the data support a role for CCN2 (CTGF) in mediating the effects of steroid hormones and TGF-beta on endometrial function.

Detection of estrogen alpha and progesterone receptors and cell proliferation in the uterus during early pregnancy in the goat

The objectives of this study were to investigate in the goat uterus the expression of estrogen-alpha (ER alpha) and progesterone receptors (PR) and their relationship to proliferation indices (Ki-67) during peri-implantation on Days 22 to 30 post coitum (pc). Immunohistochemical methods were used to quantify ER alpha and PR for luminal and deep regions of the endometrium and of the myometrium. On Day 22 pc cell proliferation was only observed in the luminal epithelium. On Day 24 pc, high cell proliferation indices were seen in luminal epithelium and proliferation began in the luminal stroma and glands. There was a positive correlation between Ki-67 and total ER alpha score in the luminal epithelium (r = 0.53, P < 0.01). Levels of PR scores were highly correlated with Ki-67 indices in luminal epithelium (r = 0.74, P < 0.01) and stroma (r = 0.70, P < 0.01). No Ki-67 expression was observed in deep glands, stroma or myometrium on any of the days studied. Results indicate that patterns of ER alpha and PR expression differ markedly, and that there was a high correlation between PR expression and cell proliferation in the caprine uterus during the peri-implantation period.

Regulation of sialomucin complex/Muc4 expression in rat uterine luminal epithelial cells by transforming growth factor-beta: implications for blastocyst implantation

Blastocyst implantation is arguably the most critical stage of mammalian embryogenesis and requires that the uterus be in a receptive state. Initiation of receptivity involves loss of anti-adhesive molecules from the apical surface of the uterine luminal epithelium, one of which is sialomucin complex (SMC/Muc4), a highly O-glycosylated, anti-adhesive glycoprotein composed of mucin ascites sialoglycoprotein-1 (ASGP-1) and transmembrane (ASGP-2) subunits. SMC expression at the uterine luminal surface, but not in glandular epithelium, is hormonally regulated and varies with the estrous cycle. SMC is lost from the luminal uterine surface at the period of receptivity. However, the mechanism by which SMC is hormonally regulated is not understood. Analyses of SMC regulation in hormone-responsive primary cultures of rat uterine luminal epithelial cells (RULEC) demonstrated robust SMC expression by the RULEC, which is not altered by treatments with estrogen or progesterone. However, both SMC protein and transcript are downregulated by transforming growth factor-beta (TGF-beta1). SMC is also downregulated when RULEC are co-cultured with isolated uterine stromal cells. Estradiol and anti-TGF-beta block the stromal cell effect. These results suggest an indirect hormonal regulation of RULEC SMC, in which TGF-beta acts as a hormonally regulated, mesenchymal paracrine factor to repress SMC production by the epithelial cells and permit 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.

Immunohistochemical localization of epidermal growth factor, transforming growth factor-alpha and growth factor-beta s in the caprine peri-implantation period

Control over the action of steroid hormones in the uterus and conceptus during the initial period of gestation appears to be regulated locally by growth factors. This study involved immunohistochemical detection of epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha) and transforming growth factor-beta s (TGF-beta s), to determine their role in the caprine peri-implantation period. Epidermal growth factor was expressed in the luminal and glandular endometrial epithelium of goats on all days studied (Days 22 to 30 post coitum), but it was not detected in trophoblastic cells or in other embryonic structures. Between Days 22 and 30 post coitum, TGF-alpha was detected in the epithelial cells and superficial stroma of the uterus and in the trophoendodermic cells of the embryo. Transforming growth factor-beta s expression, observed in the endometrium, embryo and extraembryonic membranes on Day 22 post coitum, decreased by Day 24 post coitum and disappeared in the embryo by Day 30 post coitum, while remaining in the other structures. The presence of these growth factors during the peri-implantation period in the goat suggests their participation in proliferation and differentiation phenomena which occur during implantation and embryonic development.

Beta transforming growth factors (TGFbeta) at the porcine conceptus-maternal interface. Part II: uterine TGFbeta bioactivity and expression of immunoreactive TGFbetas (TGFbeta1, TGFbeta2, and TGFbeta3) and their receptors (type I and type II)

Porcine uterine tissues were collected from Days 10 to 14 of gestation (peri-implantation period) or corresponding days of the estrous cycle. Results indicated a marked increase in beta transforming growth factors (TGFbeta1, TGFbeta2, and TGFbeta3) and TGFbeta receptor (type I and type II) immunostaining in uterine luminal epithelium (ULE) between Days 10 and 14 of gestation, but there was no increase in ULE immunostaining on the corresponding days of the estrous cycle. Uterine glands and stroma were intensely immunopositive in pregnant gilts for TGFbeta isoforms and their receptors, but immunostaining was weak to undetectable in cycling gilts. No differences were detected in myometrium, in which immunostaining was moderate in both cycling and pregnant gilts. Additionally, TGFbeta2 and TGFbeta receptor (type I and type II) immunostaining was detected in uterine monocyte/macrophage-like cells. Western blotting detected the presence of all three TGFbeta isoforms in uterine luminal flushings. The CCL64 cell TGFbeta bioassay detected bioactive TGFbetas++ in uterine luminal flushings on Days 12, 13, an 14 of gestation. These results strongly indicate that uterine expression of TGFbetas and their receptors is pregnancy specific and that bioactive TGFbetas are present at the conceptus-maternal interface in the peri-implantation period in pigs. Thus TGFbetas are likely to be involved in autocrine-paracrine interactions between the maternal uterus and the conceptus.

Cytokines in implantation

Implantation is a complex process which involves the 'invasion' of the maternal endometrium by the trophoblast surrounding the developing blastocyst. In response to this interaction there is a cellular reaction within the endometrium which has some features analogous to invasion by a tumour and some which are more characteristic of an inflammatory response. In addition, and also in common with cancer and inflammation, there is a release of biologically active molecules, including cytokines, at and around the implantation site. The information on cytokines is complex and often contradictory but it is recognised that they play an important role in the successful establishment of pregnancy. The evidence for this role is examined in this review.