Pre-fertilization approach using α-l-fucosidase modulates zona pellucida hardening during bovine in vitro embryo production

The polyspermy occurrence is considerably lower under in vivo compared to in vitro embryo culture conditions, suggesting that the presence of some factors in the maternal environment is responsible for this. The α-L-fucosidase (FUCA) is a natural glycosidase present in the oviductal fluid, therefore, this study aimed at investigating the effect of adding FUCA to the hardening of the zona pellucida (ZP), polyspermy control, and embryonic yield and quality of bovine blastocysts produced in vitro. In the first experiment, the effect of FUCA (0.125 U/mL) was evaluated during the entire in vitro fertilization (IVF). However, it was demonstrated to be embryotoxic by completely inhibiting the blastocyst formation. In the second experiment, the FUCA (0.125 U/mL) was tested as short-term incubation before IVF (pre-fertilization step) for 30 min or 2 h, which demonstrated that FUCA treatment for 30 min resulted in ZP hardening. In the third experiment, a pre-fertilization FUCA treatment (1 h) at different concentrations (0, 0.0625, and 0.125 U/mL) showed that FUCA (0.0625 U/mL) improved pre-fertilization ZP hardening and tended to increase monospermic fertilization rates but did not improve embryo yield and quality. Together, it has been demonstrated that FUCA can induce oocyte pre-fertilization ZP hardening and might improve monospermic fertilization performance, and this effect is dependent on both variables (protein concentration and incubation time).

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.

Serum and tissue pregnanes and pregnenes after dexamethasone treatment of cows in late gestation

Dexamethasone (DEX) initiates parturition by inducing progesterone withdrawal and affecting placental steroidogenesis, but the effects of DEX in fetal and maternal tissue steroid synthetic capacity remains poorly investigated. Blood was collected from cows at 270 days of gestation before DEX or saline (SAL) treatment, and blood and tissues were collected at slaughter 38 h later. Steroid concentrations were determined by liquid chromatography tandem mass spectrometry to detect multiple steroids including 5α-reduced pregnane metabolites of progesterone. The activities of 3β-hydroxysteroid dehydrogenase (3βHSD) in cotyledonary and luteal microsomes and mitochondria and cotyledonary microsomal 5α-reductase were assessed. Quantitative PCR was used to further assess transcripts encoding enzymes and factors supporting steroidogenesis in cotyledonary and luteal tissues. Serum progesterone, pregnenolone, 5α-dihydroprogesterone (DHP) and allopregnanolone (3αDHP) concentrations (all <5 ng/mL before treatment) decreased in cows after DEX. However, the 20α-hydroxylated metabolite of DHP, 20αDHP, was higher before treatment (≈100 ng/mL) than at slaughter but not affected by DEX. Serum, cotyledonary and luteal progesterone was lower in DEX- than SAL-treated cows. Progesterone was >100-fold higher in luteal than cotyledonary tissues, and serum and luteal concentrations were highly correlated in DEX-treated cows. 3βHSD activity was >5-fold higher in luteal than cotyledonary tissue, microsomes had more 3βHSD than mitochondria in luteal tissue but equal in cotyledonary sub-cellular fractions. DEX did not affect either luteal or cotyledonary 3βHSD activity but luteal steroidogenic enzyme transcripts were lower in DEX-treated cows. DEX induced functional luteal regression and progesterone withdrawal before any changes in placental pregnene/pregnane synthesis and/or metabolism were detectable.

Bovine Fetal Placenta During Pregnancy and the Postpartum Period

Bovine abortion is a worldwide problem, but despite extensive histopathologic and molecular investigations, the cause of abortion remains unclear in about 70% of cases. Cellular debris is a commonly observed histopathologic finding in the fetal placenta and is often interpreted as necrosis. In this study, the nature of this cellular debris was characterized, and histologic changes in the normal fetal placenta during pregnancy and after delivery were assessed. In addition, the presence of the most common abortifacient pathogens in Switzerland ( Chlamydiaceae, Coxiella burnetii, Neospora caninum) was tested by polymerase chain reaction. We collected 51 placentomes and 235 cotyledons from 41 and from 50 cows, respectively. In total, cellular debris was present in 48 of 51 (94%) placentomes and in 225 of 235 (96%) cotyledons, inflammation occurred in 1 of 51 (2%) placentomes and in 46 of 235 (20%) cotyledons, vasculitis was seen in 1 of 51 (2%) placentomes and 46 of 235 (20%) cotyledons, and 18 of 51 (35%) placentomes and 181 of 235 (77%) cotyledons had mineralization. The amount of cellular debris correlated with areas of positive signals for cleaved caspase 3 and lamin A. Therefore, this finding was interpreted as an apoptotic process. In total, 10 of 50 cotyledons (20%) were positive for C. burnetii DNA, most likely representing subclinical infections. The results of our study indicate that histologic features in the fetal placenta such as cellular debris, inflammation, vasculitis, and mineralization must be considered physiological processes during pregnancy and after delivery. Therefore, their presence in placentae of aborted fetuses must be interpreted with caution and might not be necessarily linked to an infectious cause of abortion.

Maternal-fetal cross talk through cell-free fetal DNA, telomere shortening, microchimerism, and inflammation

There exists a strong correlation between unscheduled inflammation at the maternal-fetal interface and the continuum of pregnancy complications. In normal pregnancy, immunological tolerance is established to protect the semi-allogeneic fetus. There has been extensive research on how the immunity, endovascular trophoblast migration, and hormonal nexus are orchestrated during pregnancy at the maternal-fetal interface to program a normal pregnancy outcome. It is not clear what contributes to the plasticity of uterine immune tolerance, fetal survial, and long-term post-partum health of the mother and the offspring. Old and new concepts have reemerged and emerged that include cell-free fetal DNA (cffDNA), telomere shortening, microchimerism involving bidirectional migration of maternal and fetal cells, and pregnancy as a stress factor. The question is how these pathways converge in a gestational age-dependent manner to contribute to the health of the mother and the offspring later in life and respond to an array of inflammatory challenges. In this Review, we provide pertinent discussion on maternal-fetal cross talk through cffDNA, telomere shortening, and microchimerism in the context of inflammatory and anti-inflammatory settings, particularly how these pathways lead to normal and adverse pregnancy outcomes.

Localization of TGF-β and TGF-β receptor in bovine term placentome and expression differences between spontaneous and induced parturition

INTRODUCTION

Mechanisms of detachment of fetal membrane after parturition in cattle are poorly understood. Glucocorticoids trigger the initiation of parturition and may facilitate the placental maturation. We compared the disappearance of trophoblast binucleate cells (BNCs) and expression of transforming growth factor-β (TGFB) in term placentomes between spontaneous and induced parturition to investigate the influences of glucocorticoids on the placental maturity.

METHODS

Cows were delivered spontaneously (SP group) or after the administration of prostaglandin (PG) F(2)α (PG group); dexamethasone, PGF(2)α, and estriol (DEX group); and triamcinolone acetonide, PGF(2)α, and betamethasone (BET group) and placentomes were collected immediately after parturition. The number of BNCs in hematoxylin and eosin stained section was examined. Protein localization and mRNA levels of TGFB and its receptor (TGFBR) were analyzed using immunohistochemistry and qRT-PCR, respectively.

RESULTS

TGFB1 is characteristically localized in the maternal septum in caruncle in contrast to TGFB2 and TGFB3, which are mainly found in cotyledonary villi and maternal epithelial cells. TGFBR1 and TGFBR2 colocalized in BNCs. The number of BNCs was lower in the SP group than in PG and DEX groups. mRNA levels of TGFB1, TGFBR1 and TGFBR2 in the SP group differed from PG and DEX groups. There was no difference between SP and BET groups in all analyses.

DISCUSSION

These results indicate that parturition inductions using PGF(2)α or dexamethasone were not able to induce disappearance of BNCs and change of TGFB signaling. Results in the BET group suggest that investigation into types, dose, and dosage schedule of glucocorticoids may facilitate placental maturation.

Cell-Free Fetal DNA, Telomeres, and the Spontaneous Onset of Parturition

Multiple previous reports have provided compelling support for the premise that spontaneous parturition is mediated by activation of inflammation-related signaling pathways leading to increased secretion of cytokines and chemokines, the influx of neutrophils and macrophages into the pregnant uterus, increased production of uterine activation proteins (eg, connexin-43, cyclo-oxygenase-2, oxytocin receptors, etc), activation of matrix metalloproteinases, and the release of uterotonins leading to cervical ripening, membrane rupture, and myometrial contractions. The missing link has been the fetal/placental signal that triggers these proinflammatory events in the absence of microbial invasion and intrauterine infection. This article reviews the biomedical literature regarding the increase in cell-free fetal DNA (cffDNA), which is released during apoptosis in the placenta and fetal membranes at term, the ability of apoptosis modified vertebrate DNA to stimulate toll-like receptor-9 (TLR9) leading to increased release of cytokines and chemokines, and the potential "fail-safe" role for the anti-inflammatory cytokine IL-10. This article also reviews the literature supporting the key role that telomere loss plays in regard to increasing the ability of vertebrate (including placental) DNA to stimulate TLR9, and in regard to signaling the onset of apoptosis in the placenta and fetal membranes, thereby providing a biologic clock that determines the length of gestation and the timing for the onset of parturition. In summary, this literature review provides a strong rationale for future research to test the hypothesis that telomere loss and increased cffDNA levels trigger the proinflammatory events leading to the spontaneous onset of parturition in mammals: the "cffDNA/telomere hypothesis."