12-Oxoeicosatetraenoic acid, a candidate signal for placenta separation, activates matrix metalloproteinase and induces apoptosis in bovine trophoblast cells

OBJECTIVE

12-oxo-5Z,8Z,10E,14Z-eicosatetraenoic acid (12-KETE), a metabolite of arachidonic acid, is a strong candidate signal for placenta separation following calf discharge at delivery. In the present study, the effects of 12-KETE on bovine trophoblast cells were investigated to determine its function in the placentome at delivery.

METHODS

Bovine trophoblast cells derived from blastocysts were used. They were cocultured with or without fibroblasts derived from bovine placentome and/or bovine uterine epithelial cells. 12-KETE was added to the culture medium.

RESULTS

Bovine trophoblast cells contained binucleate cells and strongly expressed caudal type homeobox 2 (CDX-2) genes. Addition of 12-KETE to the trophoblast cell colony without feeder cells or that on a fibroblast monolayer induced rapid exfoliation of the colony. After 12-KETE addition, trophoblast cells emitted strong fluorescence caused by the degradation of dye-quenched collagen, indicating that 12-KETE activated matrix metalloproteinase of the trophoblast cells. Exfoliated cell colonies were stained with YOPRO-1, but not propidium iodide (PI). Moreover, DNA fragmentation and Bcl-2 associated X protein (Bax) gene (apoptosis stimulator) upregulation were observed in exfoliated cells, indicating that 12-KETE induced trophoblast cell apoptosis. These results were consistent with previous in vivo observations; however, even a lower concentration of 12-KETE activated trophoblast protease. Meanwhile, fibroblasts derived from the bovine placentome converted arachidonic acid to 12-KETE.

CONCLUSION

These observations indicate that 12-KETE may serve as a signal for placenta separation at delivery.

Anti-Müllerian hormone stimulates expression of the collagen-specific chaperone 47-kDa heat shock protein in bovine uterine epithelial cells

Uterine collagen is the most abundant component of the uterine extracellular matrix and plays a critical role in pregnancy. The 47-kDa heat shock protein (HSP47) is the sole collagen-specific molecular chaperone. We investigated the mechanisms regulating the expression of HSP47 in the uterus by assessing the effect of anti-Müllerian hormone (AMH) stimulation on HSP47 expression in cultured bovine uterine epithelial cells. AMH receptor type 2 (AMHR2), AMH, and HSP47 expression was assessed by fluorescence immunocytochemistry in uterine epithelial layers of the uteri of Japanese Black cows. The effect of AMH on HSP47 expression was assessed in cultured epithelial cells. The effect of MEK/ERK inhibitor on AMH-induced HSP47 expression was also assessed. We confirmed the expression of AMHR2, AMH, and HSP47 in the uterine epithelial layers. We confirmed the expression of AMHR2, AMH, HSP47, and type IV collagen in cultured uterine epithelial cells. AMH treatment at 10 or 100 ng/ml promoted significant HSP47 expression (p < 0.05). MEK/ERK inhibitor U0126 pretreatment suppressed such AMH stimulation on HSP47. These findings indicate that AMH induced HSP47 protein expression through the ERK pathway in bovine uterine epithelial cells.

Up-regulated mRNA expression of some anti-inflammatory mediators in bovine oviduct epithelial cells by urea in vitro: Cellular pathways by Reactome analysis

Increased urea concentration is a major cause of low fertility in dairy cows fed high-protein diets. A strong correlation exists between the urea concentration in the blood and oviduct fluid of dairy cows. In this study, bovine oviduct epithelial cells (BOECs) were incubated with varying concentrations of urea (0, 20, 40, and 80 mg/dL) in the absence of ovarian sex steroids (estradiol and progesterone) and luteinizing hormone. The 80 mg/dL urea reduced the cell viability, and thus was excluded in further analysis. Compared to the control (U0), the 20 mg/dL urea (U20) increased the mRNA expression of Toll-like receptor (TLR) 4, interleukin (IL) 10, IL4, and prostaglandin (PG) E synthase (mPGES) but decreased the mRNA expression of tumor necrosis factor α (TNFA). Compared to U0, the 40 mg/dL urea (U40) decreased the mRNA expression of TNFA and increased alpha-1-acid glycoprotein (AGP). U40 also increased TLR2, IL10, and IL4 mRNA expression compared to U0. In addition, compared to U20, the U40 decreased the mRNA expression of TLR4 and IL1B but increased that of AGP and TLR2. Subsequently, the mRNA expression data were then projected into the Reactome database. The Reactome analysis showed that pathways, including cytokine signaling in the immune system (i.e., TNFs bind their physiological receptors) and death receptor signaling (i.e., TNF signaling), were down-regulated in the presence of urea compared to the U0 group. These in vitro data implied that high urea level can alter the balance between pro- and anti-inflammatory responses in BOECs, thus providing a suboptimal environment for the early reproductive events or a weakened innate immune system, predisposing the oviduct to infections.

MicroRNA-199a mediates mucin 1 expression in mouse uterus during implantation

Embryo implantation is a complicated process involving interactions between the blastocyst and the luminal epithelium of the receptive uterus. Mucin 1 (MUC1) is an integral membrane glycoprotein expressed apically by secretory epithelial cells and the glandular epithelium in different organs, including the uterus. It is believed that loss of MUC1 on the surface of uterine epithelial cells is necessary for embryo implantation. The endogenous non-protein coding microRNAs (miRNAs) of 21-24 nucleotides are found in diverse organisms. It has been shown that miRNAs participate in a range of cellular processes by regulating gene expression at the post-transcriptional level. In the present study, the regulatory role of miRNA-199a on the expression of MUC1 in mouse uterus during implantation was investigated for its effect on embryo implantation. Western blotting and immunohistochemistry results showed high MUC1 expression on Day 0.5 and low expression by Day 4.5 of pregnancy. In contrast with MUC1 expression, increased miRNA-199a expression was evident at Day 4.5 of pregnancy, as measured by real-time reverse transcription-polymerase chain reaction. In addition, we demonstrated direct binding of miRNA-199a to the 3'-untranslated region of MUC1. Transfection of miRNA-199a into mouse uterine epithelial cells isolated from Day 0.5 of pregnancy also downregulated expression of MUC1. Therefore, the present study provides evidence that MUC1 is a direct target of miRNA-199a and suggests that development of novel strategies to facilitate a successful pregnancy and repair implantation failure humans may include miRNA.

Biological activity of recombinant bovine interferon τ produced by a silkworm-baculovirus gene expression system

Bovine interferon (bIFN) τ plays a crucial role in maternal-fetal recognition and was expressed using a Bombyx mori (Bm) nuclear polyhedrosis virus (silkworm baculovirus) gene expression system. The biological effects of Bm-recombinant bIFNτ (rbIFNτ) on prostaglandin (PG) F_2α synthesis were investigated in cultured bovine endometrial epithelial cells with oxytocin (OT, 100 nM) and on the in vitro development of bovine embryos. Bm-rbIFNτ and OT were shown to suppress PGF_2α production in a dose-dependent manner. When in vitro produced morula stage embryos were cultured for 72 hr in modified CR1aa medium supplemented with or without rbIFNτ, Bm-rbIFNτ (10 ng/ml) significantly promoted development to the expanded blastocyst stage. In conclusion, Bm-rbIFNτ was suggested to have the same bioactivity as native IFNτ.

Expression of extracellular matrix metalloproteinase inducer (EMMPRIN) and its related extracellular matrix degrading enzymes in the endometrium during estrous cycle and early gestation in cattle

BACKGROUND

Extracellular matrix metalloproteinase inducer (EMMPRIN) regulates several biological functions involving the modulation of cell behaviors via cell-cell and cell-matrix interactions. According to its diverse functions, we hypothesized that EMMPRIN may play an important role in endometrial remodeling and establishment of pregnancy in cow.

METHODS

In this study, endometrial tissues from the cyclic cows during before ovulation, after ovulation and middle of estrous cycle; and pregnant endometrial tissues from Day 19 to 35 of gestation have been used. Expression of mRNA was analyzed by RT-PCR, qPCR and in situ hybridization whereas protein expression by immunohistochemistry and western blot analysis.

RESULTS

EMMPRIN mRNA was expressed in both cyclic and pregnant endometrium and significantly higher in the endometrium at Day 35 of gestation than the cyclic endometrium. In Western blot analysis, an approximately 65 kDa band was detected in the endometrium, and approximately 51 kDa in the cultured bovine epithelial cells and BT-1 cells, respectively. Both in situ hybridization and immunohistochemistry data showed that EMMPRIN was primarily expressed in luminal and glandular epithelium with strong staining on Day 19 conceptus. At Day 19 of gestation, expression of EMMPRIN mRNA on luminal epithelium was decreased than that observed at middle of estrous cycle, however, on Day 30 of gestation, slightly increased expression was found at the site of placentation. Expression of matrix metalloproteinase-2 (MMP-2) and MMP-14 mRNA were mainly detected in stroma and their expression also decreased at Day 19 of gestation however it was also expressed at the site of placentation at Day 30 of gestation as observed for EMMPRIN. Expression of MMP-1 or -9 mRNA was very low and was below the detection limit in the cyclic and pregnant endometrium.

CONCLUSION

EMMPRIN from the luminal epithelium may regulate the expression of stromal MMP-2 and -14 suggesting its crucial role in adhesion and fusion of embryo to luminal epithelium by directly itself through physiological tissues remodeling and developmental process, and/or stimulating MMPs to compensate endometrial functions.

Development of an in vitro model for bovine placentation: a comparison of the in vivo and in vitro expression of integrins and components of extracellular matrix in bovine placental cells

BACKGROUND/AIMS

Interaction of trophoblastic integrins with the extracellular matrix plays a role in embryo implantation and trophoblast invasion. The phenomenon of restricted trophoblast invasion, observed in the bovine epitheliochorial placenta offers intriguing conditions to study invasive processes. The migration of bovine trophoblast giant cells is accompanied by the expression of specific integrins and corresponding extracellular matrix ligands.

METHODS

Primary cultures of different cell populations from cow placentomes were established and characterized, and in vitro phenotypes were compared with in vivo conditions by immunofluorescence.

RESULTS

Propagated epithelial cells were positive for cytokeratin and vimentin, while fibroblasts contained alpha-smooth muscle actin, desmin and vimentin. Epithelial cells coexpressed integrin subunits alpha(6) and beta(1) with laminin, and fibroblast cells were positive for alpha(v), beta(3), fibronectin and laminin. In contrast to cells in vivo, cultured epithelial cells secreted fibronectin, while collagen IV was not detected. The occurrence of integrin subunits was confirmed at mRNA level by RT-PCR.

CONCLUSION

We have established cell cultures isolated from maternal and fetal components of bovine placentomes expressing typical cytoskeletal filaments and integrin receptors also present in their in vivo counterparts. These bovine placentomal cells provide a suitable in vitro model for the study of cell-cell interactions.

Validation of primary epitheloid cell cultures isolated from bovine placental caruncles and cotyledons

In order to study feto-maternal interactions in the bovine synepitheliochorial placenta primary cell cultures of both placentomal components throughout pregnancy, namely caruncular epithelial cells and trophoblast cells were developed. The aim of this study was to validate and improve a method to culture caruncular epithelial cells and fetal trophoblast from manually separated placentomes. Prior to seeding the presence of fetal cells in caruncular samples and vice-versa could be demonstrated by the detection of the Y-chromosome via fluorescence in situ hybridization (FISH) provided the fetus was male. Epitheloid shaped cells present in both cultures (cotyledon and caruncle) were characterized on a morphological basis as well as by immunofluorescence and Western blot thereby detecting cytokeratin, zonula occludens-1 and vimentin but not alpha-smooth muscle actin and desmin. The absence of the Y-chromosome demonstrated the caruncular origin of epitheloid cells. In addition, a population of polygonally shaped cells derived from the cotyledon was propagated and displayed the same cytoskeletal characteristics as described above. The presence of the Y-chromosome confirmed the fetal origin of these cells and the lacking uptake of fluorescence conjugated low density lipoprotein, specific for endothelial cells, identified polygonally shaped cells as fetal trophoblast cells. In conclusion, the cross-contamination of maternal and fetal cells in manually separated placentomes should be considered in future experiments as it may lead to false positive results dependent on the sensitivity of the method applied. This study highlights the importance of an appropriate cell characterization and identification, especially when isolating primary cells.

Establishment of a specific radioimmunoassay for bovine interferon τ

A radioimmunoassay (RIA) was developed for quantification of bovine interferon (bIFN) tau, conceptus secretory protein, which allows for the maintenance of the corpus luteum during early pregnancy. A cDNA coding bIFN tau was derived from cultured trophoblast cells (TBs). Recombinant (r) bIFN tau was produced in a baculovirus expression system with two different viruses. The RIA was a double-antibody competitive binding assay that used anti-bIFN tau antiserum (raised in rabbits) as the primary antibody, a radioiodinated derivative of bIFNtau as the radioactive tracer, and goat anti-rabbit IgG as the secondary antibody. The antibody did not cross-react with rbIFN alpha, recombinant human IFN beta or recombinant ovine IFN tau. The correct recovery of amounts of rbIFN tau indicated good accuracy. Serially concentrated TB conditioned media, paralleled the standard curve for bIFN tau. The intra-assay and inter-assay coefficients of variation at bIFN tau levels of 7.8 and 15.6 ng/mL were 7.1 and 8.1%, and 11.0 and 8.5%, respectively. bIFN tau was directly detected in uterine flushings obtained from cows at Day 16 of pregnancy. In summary, this assay was suitable for the measurement of bIFN tau.

Biological activity of recombinant bovine interferon tau using an Autographa californica nuclear polyhedrosis virus expression system

Bovine interferon (bIFN) tau, which plays a key role in maternal-fetal recognition of pregnancy, was expressed by an Autographa californica nuclear polyhedrosis virus expression system. cDNA coding bIFNtau was derived from cultured trophoblast cells. The recombinant (r) bIFNtau had high antiviral activity (1 x 10 (8) IU/mg) and the molecular weight of rbIFNtau was estimated to be 23 kDa by Western blotting analysis. We investigated the biological effect of rbIFNtau on prostaglandin (PG) F(2alpha) synthesis in cultured bovine endometrial epithelial cells in the presence or absence of oxytocin (OT, 100 nM). rbIFNtau suppressed basal and OT-induced PGF(2alpha) production in a dose-dependent manner (1-1,000 ng/ml). These results showed that biologically active rbIFNtau was produced in the baculovirus expression system, and that rbIFNtau had the ability to suppress the synthesis of PGF(2alpha) from bovine endometrial epithelial cells.

Differential Effects of Interferon-τ on the Prostaglandin Synthetic Pathway in Bovine Endometrial Cells Treated with Phorbol Ester

Rationale for these experiments was to evaluate the dose effects of bovine interferon-tau (IFN-tau) on the prostaglandin secretory pathway of immortalized bovine endometrial (BEND) cells in response to phorbol 12, 13-dibutyrate (PdBu) and to characterize similar responses in primary bovine uterine epithelial cells as a biomonitor of embryo-induced antiluteolytic effects on the endometrium. The BEND cells were treated with PdBu (0 or 100 ng/mL) and IFN-tau (0 or 50 ng/mL) for 6 h. The PdBu stimulated secretions of PGF2alpha and prostaglandin E2 (PGE2). Co-treatment of cells with IFN-tau blocked PdBu-induced secretion of both PGF2alpha and PGE2. Treatment with PdBu for 6 h induced expression of prostaglandin H synthase-2 mRNA, prostaglandin H synthase-2 protein, and prostaglandin E synthase mRNA, which were blocked with concurrent addition of IFN-tau. Doses of IFN-tau (0.05, 0.5, 1, 5, 10, and 20 microg/mL) were used with PdBu (0 and 100 ng/mL). The IFN-tau alone failed to stimulate secretion of PGF2alpha and PGE2, whereas IFN-tau doses <5 microg/mL suppressed PdBu-stimulated secretions of PGF2alpha and PGE2. Uterine epithelial cells were isolated from cows at d 17 after estrus and were cultured to confluence in serum-free medium. Cells were treated with IFN-tau (0, 50, or 500 ng/mL) and PdBu (0 or 100 ng/mL) before media were collected after 24 h for PGF2alpha and PGE2 analyses. Treatment of primary uterine epithelial cells with PdBu induced PGF2alpha secretion, and IFN-tau (50 and 500 ng/mL) caused a reduction in PGF2alpha secretion induced by PdBu. In the absence of PdBu, IFN-tau increased basal secretion of PGF2alpha. Concentrations of PGE2 increased in response to PdBu, and the 50-ng/mL dose of IFN-tau had a stimulatory effect on PGE2 concentrations compared with the 500-ng/mL dose in the absence of PdBu. Phorbol ester-induced gene transcription as related to prostaglandin synthesis is regulated by IFN-tau in vitro.

Regulation of blastocyst migration, apposition, and initial adhesion by a chemokine, interferon gamma-inducible protein 10 kDa (IP-10), during early gestation

For a pregnancy to be established, initial apposition and adhesion of the blastocyst to maternal endometrium must occur in a coordinated manner; however, a key factor(s) that mediates the trophoblast cell migration and attachment to the apical surface of the endometrium has not been identified. In this study, we examined the effect of an endometrial chemokine, interferon-gamma-inducible protein 10 kDa (IP-10), on conceptus migration to the endometrial epithelium. We first studied endometrial IP-10 mRNA expression, which was localized in the subepithelial stromal region, and detected the protein in the uterine flushing media during early pregnancy. Expression of IP-10 mRNA by the endometrium of cyclic animals was stimulated by the addition of a conceptus factor interferon-tau (IFN-tau). Immunofluorescent analysis revealed that IP-10 receptor, CXCR3, was localized in the trophoblast cells, to which biotinylated-recombinant caprine IP-10 (rcIP-10) bound. Chemotaxis assay indicated that rcIP-10 stimulated the migration of trophoblast cells, and the effects of rcIP-10 were neutralized by the pretreatment with an anti-IP-10 antibody. Adhesive activity of trophoblast cells to fibronectin was promoted by rcIP-10, and the effect was inhibited by the use of anti-IP-10 antibody. Further adhesion experiments demonstrated that binding of trophoblast cells to fibronectin was completely inhibited by a peptide of the Arg-Gly-Asp (RGD) sequence, which binds to integrins alpha5beta1, alphaVbeta1, alphaVbeta3, and alphaVbeta5, whereas non-binding peptide containing Arg-Gly-Glu (RGE) had minimal effects. More importantly, rcIP-10 promoted the adhesion of trophoblast cells to primary cells isolated from endometrial epithelium. Furthermore, rcIP-10 stimulated the expression of integrin alpha5, alphaV, and beta3 subunit mRNA in trophoblast cells. These findings suggest that endometrial IP-10 regulates the establishment of apical interactions between trophoblast and epithelial cells during early gestation.

A three-dimensional cell culture model for bovine endometrium: regeneration of a multicellular spheroid using ascorbate

The development of a multicellular spheroid comprising bovine endometrial epithelial cells (BEE) and bovine endometrial stromal cells (BES) is described in this study. The BES were cultured to confluence in medium with L -ascorbic acid phosphate magnesium salt n -hydrate (AsA-P) which stimulates collagen synthesis in BES. The BEE were co-cultured on a BES cell-sheet for 24h before detachment of the cell-sheet to generate a hetero-spheroid. After EDTA treatment and agitating with pipette, the floating cell-sheet shrank and became an aggregated cell mass in a few days; it finally formed a round-shaped hetero-spheroid composed of BES and BEE. Histological examination found that hetero-spheroids were covered with BEE on the outer layer. When cell viability was examined with TUNEL (terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling), no positive signal was detected in the spheroid for up to 10 days. Immunofluorescence observations showed that spheroids contained abundant extracellular matrices, including type-I, -III, -IV collagen, fibronectin, and laminin. PGF(2alpha) produced by hetero-spheroids in response to oxytocin was significantly higher than those produced by monolayer cultured BEE (P< 0.05). MMPs were not detected in media from spheroids cultured for 5 days after detachment of the cell sheet. These results indicate that bovine endometrial cells have the capacity to regenerate as a multicellular spheroid after treatment with ascorbate in vitro. The spheroid displays an endometrium-mimic feature. Thus, we conclude that spheroids formed by BES and BEE are a useful in vitro model of bovine endometrium.

A Passage and Storage System for Isolated Bovine Endometrial Epithelial and Stromal Cells

To establish a storage system for isolated endometrial cells, we investigated the basal, oxytocin (OT)- and tumor necrosis factor (TNF) alpha-stimulated production of prostaglandin (PG) F(2alpha) in bovine-passaged and frozen-thawed endometrial cells. Stromal and epithelial cells obtained from cows in the early stage of the estrous cycle (Days 2-5) were frozen at -80 C or further cultured and/or passaged until passage 4 in DMEM/Ham's F-12 supplemented with 10% calf serum. A fresh-unfrozen primary culture and one-time passaged fresh-unfrozen cells were used as the control. When both unfrozen and frozen cells reached confluence, the culture medium was replaced with fresh medium with 0.1% BSA and the cells were stimulated with OT (100 ng/ml) or TNFalpha (1 ng/ml) for 4 h. The passage and freezing of the endometrial cells did not affect their morphology. In primary culture of frozen and unfrozen endometrial cells, OT strongly stimulated PGF(2alpha) production in epithelial cells, and TNFalpha strongly stimulated PGF(2alpha) production in stromal cells (P<0.05). The basal output of PGF(2alpha) in frozen stromal cells was similar to that in unfrozen stromal cells. However, the basal output of PGF(2alpha) in frozen epithelial cells was significantly lower than that unfrozen cells (P<0.05). On the other hand, in passaged cells, the basal level of PGF(2alpha) production was retained until passage 1 in epithelial cells, whereas it was retained until passage 4 in stromal cells. Although epithelial cells responded to OT in PGF(2alpha) production until passage 2 (P<0.05), the stromal cells showed a significant response to TNFalpha until passage 4 (P<0.05). These results suggest that stored cells could be used for studying the physiology of bovine endometrium in vitro until passage 1 in endometrial epithelial cells, and until passage 4 in stromal cells.