CCL20-CCR6 axis directs sperm-oocyte interaction and its dysregulation correlates/associates with male infertility‡.

The interaction of sperm with the oocyte is pivotal during the process of mammalian fertilization. The limited numbers of sperm that reach the fallopian tube as well as anatomic restrictions indicate that human sperm-oocyte encounter is not a matter of chance but a directed process. Chemotaxis is the proposed mechanism for re-orientating sperm toward the source of a chemoattractant and hence to the oocyte. Chemokines represent a superfamily of small (8-11 kDa), cytokine-like proteins that have been shown to mediate chemotaxis and tissue-specific homing of leukocytes through binding to specific chemokine receptors such as CCRs. Here we show that CCR6 is abundantly expressed on human sperms and in human testes. Furthermore, radioligand-binding experiments showed that CCL20 bound human sperm in a specific manner. Conversely, granulosa cells of the oocyte-surrounding cumulus complex as well as human oocytes represent an abundant source of the CCR6-specific ligand CCL20. In human ovaries, CCL20 shows a cycle-dependent expression pattern with peak expression in the preovulatory phase and CCL20 protein induces chemotactic responses of human sperm. Neutralization of CCL20 in ovarian follicular fluid significantly impairs sperm migratory responses. Conversely, analyses in infertile men with inflammatory conditions of the reproductive organs demonstrate a significant increase of CCL20/CCR6 expression in testis and ejaculate. Taken together, findings of the present study suggest that CCR6-CCL20 interaction may represent an important factor in directing sperm-oocyte interaction.

Live birth after artificial oocyte activation using a ready-to-use ionophore: a prospective multicentre study.

Artificial oocyte activation has been proposed as a suitable means to overcome the problem of failed or impaired fertilization after intracytoplasmic sperm injection (ICSI). In a multicentre setting artificial oocyte activation was applied to 101 patients who were diagnosed with fertilization abnormalities (e.g. less than 50% fertilized oocytes) in a previous conventional ICSI cycle. Female gametes were activated for 15 min immediately after ICSI using a ready-to-use Ca(2+)-ionophore solution (A23187). Fertilization, pregnancy and live birth rates were compared with the preceding cycle without activation. The fertilization rate of 48% in the study cycles was significantly higher compared with the 25% in the control cycles (P < 0.001). Further splitting of the historical control group into failed (0%), low (1-30%) and moderate fertilization rate (31-50%) showed that all groups significantly benefitted (P < 0.001) in the ionophore cycle. Fewer patients had their embryo transfer cancelled compared with their previous treatments (1/101 versus 15/101). In total, 99% of the patients had an improved outcome with A23187 application resulting in a 28% live birth rate (35 babies). These data suggest that artificial oocyte activation using a ready-to-use compound is an efficient method.

Selection of the in vitro culture media influences mRNA expression of Hedgehog genes, Il-6, and important genes regarding reactive oxygen species in single murine preimplantation embryos.

BACKGROUND: The aim of this paper was to determine the influence of different in vitro culture media on mRNA expression of Hedgehog genes, il-6, and important genes regarding reactive oxygen species in single mouse embryos. METHODS: Reverse transcription of single embryos either cultured in vitro from day 0.5 until 3.5 (COOK's Cleavage medium or Vitrolife's G-1 PLUS medium) or in vivo until day 3.5 post coitum. PCR was carried out for ß-actin followed by nested-PCR for shh, ihh, il-6, nox, gpx4, gpx1, and prdx2. RESULTS: The number of murine blastocysts cultured in COOK medium which expressed il-6, gpx4, gpx1, and prdx2 mRNA differed significantly compared to the in vivo group. Except for nox, the mRNA profile of the Vitrolife media group embryos varied significantly from the in vivo ones regarding the number of blastocysts expressing the mRNA of shh, ihh, il-6, gpx4, gpx1 and prdx2. CONCLUSIONS: The present study shows that different in vitro culture media lead to different mRNA expression profiles during early development. Even the newly developed in vitro culture media are not able to mimic the female reproductive tract. The question of long-term consequences for children due to assisted reproduction techniques needs to be addressed in larger studies.

In vitro culture does not alter the expression of vascular endothelial growth factor and its receptors in single murine preimplantation embryos.

BACKGROUND: In vitro culture of embryos, as widely used in assisted reproduction techniques, may influence embryonic development and subsequently the establishment of pregnancy. The aim of this study was to determine a potential influence of the in vitroculture regarding VEGF, VEGFR1 and VEGFR2 mRNA expression in developing single mouse embryos. METHODS: Murine embryos were isolated on day 1 post coitus (p.c.) and cultivated for a developmental time course followed by examination for mRNA expression using RT-nested PCR. Furthermore, in vitro cultured blastocysts were compared to in vivo development at 101 h p.c. RESULTS: At 101 h p.c. there were no significant differences between in vivo and in vitro cultured blastocysts regarding the expression of VEGF and its receptors. In the developmental time course, VEGF expression increased up to 94% in late blastocysts whereas the VEGF receptor expression remained low. CONCLUSIONS: This study showed that the in vitro culture did not alter the embryonic VEGF and VEGFR mRNA expression reassuring that the culture conditions in assisted reproduction techniques are well suited for maintaining the VEGF mRNA expression profile. Additionally, nearly 100% VEGF expression in late blastocysts highlights its importance for angiogenesis induction at the fetal-maternal interface.

Interleukin-1 system in the human fallopian tube-No spatial but a temporal regulation of mRNA and protein expression.

The human fallopian tube provides the environment for the first 5 days of embryonic development in vivo. The IL-1 system is involved in human embryo implantation. This study aimed to investigate IL-1beta, IL-1ra and IL-1R tI expression within the length of the human fallopian tube on mRNA- and protein-level in samples from proliferative versus secretory phase, postmenopause (PMP) samples and samples from intra- (IUP) and extrauterine pregnancies (EUP) to examine possible spatial and hormonal induced changes (fimbrial, ampullary and isthmic tube segments). On mRNA-level, IL-1beta was expressed in all samples except in PMP. IL-1R tI could be detected in all samples whereas IL-1ra was only expressed in secretory phase and the IUP sample. Immunohistochemically we could detect IL-1beta and IL-1R t1 protein in all proliferative and secretory phase samples with maximum intensity in secretory phase samples whereas IL-1ra was expressed in secretory phase samples only. Overall no spatial but temporal differences possibly due to hormonal changes could be observed suggesting a precise regulation of the IL-1 system, especially for IL-1ra and moreover a stable molecular architecture within the full length of the fallopian tube.

Expression of the vascular endothelial growth factor receptor neuropilin-1 in the human endometrium.

Angiogenesis is a key process in the endometrium which undergoes dramatic changes during the menstrual cycle. Molecules such as vascular endothelial growth factor (VEGF), acting via two tyrosine kinase family receptors (VEGFR1 [Flt-1] and VEGFR2 [KDR/Flk-1]), are potent modulators of angiogenesis and vascular remodelling in the endometrium. Recently, neuropilin-1 (NRP-1) was shown to be expressed in endothelial cells binding VEGF(165) and therewith enhancing the binding of VEGF(165) to VEGFR2. This suggests that NRP-1, in addition to the known VEGF receptors, may play an important role in VEGF-induced angiogenesis. In this study, the expression of NRP-1 in the cycling human endometrium has been investigated by reverse transcription (RT)-polymerase chain reaction (RT-PCR), semi-quantitative competitive RT-PCR (RT-cPCR) and immunohistochemical staining. NRP-1 was expressed in all 32 endometrium samples throughout the menstrual cycle. However, samples from the proliferative phase showed significantly higher expression levels of NRP-1 mRNA compared to samples from the secretory phase (t/c-ratio 2.13 vs. 0.84, p<0.05). Immunohistochemistry confirmed the results showing increased NRP-1 staining in vascular endothelium, glandular epithelium and stromal cells of the proliferative phase endometrium. This study demonstrates mRNA and protein expression of NRP-1 in human endometrium samples throughout the menstrual cycle. The enhanced expression of NRP-1 in the proliferative phase suggests that it may participate in hormonally regulated changes of endometrial angiogenesis, preparing the endometrium for the implantation of an embryo. NRP-1 expression might act as a co-factor for VEGF(165) enhancing the angiogenic stimulus.

Angiopoietin-1 and -2 mRNA and protein expression in mouse preimplantation embryos and uteri suggests a role in angiogenesis during implantation.

After attachment and migration through the endometrial epithelium, the embryo must induce angiogenesis within the endometrial stroma to successfully complete the implantation process. Growth factors have been shown to play an important role in embryo implantation and placentation. The aim of the study was to investigate the expression of angiopoietin-1 and -2 (Ang-1 and -2) mRNA and protein expression during the development of single preimplantation mouse embryos and of possible complementary expression in mouse uteri. Angiopoietin-1 mRNA was expressed throughout development in 78% of zygotes, 66% of 2-cell-embryos, 71% of 4-cell-embryos, 70% of 8-cell-embryos, 60% of morula stages, 48% of early blastocysts and 78% of late blastocysts. The number of Ang-1-expressing embryos in the early-blastocyst group was significantly different in comparison with zygotes, 4-cell-embryos, 8-cell-embryos and late blastocysts. Angiopoietin-2 mRNA and protein expression could not be detected in preimplantation embryos. Examination of the uteri revealed Ang-2 mRNA and protein expression in the oestrogen-dominated cycling phase and the progesterone-dominated mated phase, whereas Ang-1 expression was restricted to the mated phase. Herein, Ang-1 expression in preimplantation mouse embryos as well as Ang-1 and -2 expression in mouse uteri is demonstrated, suggesting a possible role for angiopoietins in the embryo-maternal dialogue of the implantation process via an enhancement of the vascular remodelling in favour of an implanting conceptus.

Vascular endothelial growth factor (VEGF) mRNA splice variants are differentially expressed in human blastocysts.

The aim of our study was to detect and characterize mRNA expression of VEGF isoforms VEGF(121), VEGF(145), VEGF(165), VEGF(189), and VEGF(206) in human blastocysts. We recently demonstrated VEGF mRNA expression during human preimplantation embryo development, and further information regarding the alternatively spliced mRNAs resulting in freely secreted proteins or proteins bound to cell surface heparan-sulphate proteoglycans is needed to better understand the process of angiogenesis during implantation. Human blastocysts unsuitable for transfer obtained from the IVF programme at Stanford University were examined by reverse transcription/hemi-nested polymerase chain reaction for their expression of VEGF mRNA splice variants. VEGF mRNA was expressed in 17 out of 19 (89%) blastocysts. Of the 17 blastocysts, VEGF(121) mRNA was detected in 88%, VEGF(145) mRNA in 100%, VEGF(165) mRNA in 71%, and VEGF(189) mRNA in 24% of blastocysts. There was co-expression of mRNA for VEGF(121) and VEGF(145) only in 29% blastocysts, of mRNA for VEGF(165) and VEGF(145) only in 12%, and of mRNA for VEGF(121), VEGF(145) and VEGF(165) in 59% blastocysts. VEGF(206) mRNA could not be detected. In conclusion, we demonstrated that blastocysts express the mRNAs encoding for the free VEGF proteins, enabling the implanting embryo to immediately induce angiogenesis at the implantation site.

Expression of vascular endothelial growth factor mRNA in human preimplantation embryos derived from tripronuclear zygotes.

OBJECTIVE: To detect the expression of vascular endothelial growth factor (VEGF) mRNA and/or secretion of VEGF protein by human preimplantation embryos. DESIGN: Human preimplantation embryos not suitable for uterine transfer were examined for beta-actin and VEGF mRNA expression. Culture media from normally fertilized and developing preimplantation embryos were assessed for VEGF protein secretion. SETTING: Clinics and academic research laboratories at the Departments of Obstetrics and Gynecology at the Stanford University, Palo Alto, California and the Heinrich-Heine-University, Düsseldorf, Germany. PATIENT(S): Couples undergoing IVF by intracytoplasmic sperm injection for various reasons. INTERVENTION(S): Six unfertilized oocytes and 33 pathologically fertilized (tripronucleic, 3PN) preimplantation embryos were examined for VEGF mRNA expression, and 16 embryos were examined for VEGF protein secretion. MAIN OUTCOME MEASURE(S): Embryonic expression of VEGF mRNA and VEGF protein as determined by reverse transcription (RT)/nested polymerase chain reaction (PCR) and ELISA. RESULT(S): VEGF mRNA and protein could not be detected in unfertilized oocytes. However, 30/33 preimplantation embryos did express VEGF mRNA (11/12 10-to-16-cell embryos, 3/4 morulae, 11/12 early blastocysts, 5/5 hatched blastocysts). The VEGF protein level was below the sensitivity of the ELISA. CONCLUSION(S): Production of VEGF may give the embryo the ability to induce neoangiogenesis at the implantation site, thus creating an environment necessary for its survival.

Is there a place for biochemical embryonic preimplantational screening?

The advent of assisted reproductive techniques such as intracytoplasmic sperm injection has markedly reduced the problem of unsuccessful fertilization in modern IVF. However, pregnancy rates and 'take-home-baby' rates remain unsatisfactorily low. Attempts to overcome low pregnancy rates by transferring a larger number of embryos to the mother often result in multiple pregnancies. The preimplantation embryo synthesizes several proteins that may signal its presence to the maternal system, and the interaction between the embryo and the endometrium is controlled, at least in part, by cytokines and growth factors. However, little is known about the interactions between the embryonic and maternal proteins. A better understanding of normal preimplantation embryo development may lead to improved in vitro culture conditions and higher pregnancy rates. This review gives an overview of the current knowledge of the embryonic factors produced during the preimplantation period. The development of the interleukin 1 system for screening human preimplantation embryos is also discussed. Current biochemical embryonic screening procedures are highly experimental, but increasing knowledge of the physiology of embryonic development might enable these screening procedures to be used to identify embryos that are capable of successful implantation.

Disruption of myoglobin in mice induces multiple compensatory mechanisms.

Myoglobin may serve a variety of functions in muscular oxygen supply, such as O(2) storage, facilitated O(2) diffusion, and myoglobin-mediated oxidative phosphorylation. We studied the functional consequences of a myoglobin deficiency on cardiac function by producing myoglobin-knockout (myo(-/-)) mice. To genetically inactivate the myoglobin gene, exon 2 encoding the heme binding site was deleted in embryonic stem cells via homologous recombination. Myo(-/-) mice are viable, fertile, and without any obvious signs of functional limitations. Hemoglobin concentrations were significantly elevated in myo(-/-) mice. Cardiac function and energetics were analyzed in isolated perfused hearts under resting conditions and during beta-adrenergic stimulation with dobutamine. Myo(-/-) hearts showed no alteration in contractile parameters either under basal conditions or after maximal beta-adrenergic stimulation (200 nM dobutamine). Tissue levels of ATP, phosphocreatine ((31)P-NMR), and myocardial O(2) consumption were not altered. However, coronary flow [6.4 +/- 1.3 ml.min(-1).g(-1) [wild-type (WT)] vs. 8.5 +/- 2.4 ml.min(-1).g(-1) [myo(-/-)] [and coronary reserve [17.1 +/- 2.1 (WT) vs. 20.8 +/- 1.1 (myo(-/-) ml. min(-1).g(-1) were significantly elevated in myo(-/-) hearts. Histological examination revealed that capillary density also was increased in myo(-/-) hearts [3,111 +/- 400 mm(-2) (WT) vs. 4,140 +/- 140 mm(-2) (Myo(-/-)]. These data demonstrate that disruption of myoglobin results in the activation of multiple compensatory mechanisms that steepen the pO(2) gradient and reduce the diffusion path length for O(2) between capillary and the mitochondria; this suggests that myoglobin normally is important for the delivery of oxygen.

Epidermal growth factor and leukemia inhibitory factor levels in follicular fluid. Association with in vitro fertilization outcome.

OBJECTIVE: To determine the levels of epidermal growth factor (EGF) and leukemia inhibitory factor (LIF) in follicular fluid, if any, and to assess the association of these cytokines with the outcome of in vitro fertilization (IVF). STUDY DESIGN: EGF and LIF levels determined by enzyme-linked immunosorbent assay in 60 preovulatory follicular fluids were compared with 25 IVF outcomes. RESULTS: Immunoreactive EGF and LIF could be detected in human follicular fluid. Levels of these cytokines were similar in FF obtained from follicles that resulted in fertilized oocytes and those that did not. EGF levels were significantly lower in patients establishing a pregnancy as compared to patients achieving no pregnancy (P < .007). LIF levels were similar in both groups of patients. CONCLUSION: EGF appears to be associated with IVF outcome.

Expression of mRNA for vascular endothelial growth factor transmembraneous receptors Flt1 and KDR, and the soluble receptor sflt in cycling human endometrium.

The aim of this study was to quantify and localize the mRNA expression of the vascular endothelial growth factor (VEGF) receptors Flt1, KDR and sflt, in human endometrium throughout the menstrual cycle. Since neoangiogenesis is crucial during embryonic implantation, we postulate that endometrial receptivity to VEGF may be altered during the luteal phase in order to support implantation. Human endometrium was collected and specified as early proliferative (n = 3), mid-proliferative (n = 4), late proliferative (n = 3), early secretory (n = 2), mid-secretory (n = 4), and late secretory (n = 4). Competitive reverse transcription-polymerase chain reaction (RT-PCR) was performed to evaluate the mRNA values throughout the menstrual cycle. Additionally, four samples were separated into epithelial and stromal-enriched cell fractions and competitive RT-PCR was carried out to specify the distribution of the mRNA expression. While mRNA for the transmembraneous receptors Flt1 and KDR was shown to be present at almost constant values throughout the menstrual cycle, the soluble receptor, sflt, had a three-fold higher level of transcription during mid-proliferative and late proliferative when compared with early proliferative and the entire secretory phase. The expression of Flt1, KDR and sflt mRNA was detected in both isolated endometrial epithelial and stromal cell fractions. In conclusion, the down-regulation of sflt, which functions as a soluble antagonist, during the luteal phase may act to sensitize the maternal endothelial receptors to angiogenetic stimuli secreted by the implanting embryo.

Coronary hemodynamics in endothelial NO synthase knockout mice.

For the specific analysis of endothelial NO synthase (eNOS) function in the coronary vasculature, we generated a mouse homozygous for a defective eNOS gene (eNOS-/-). Western blot as well as immunohistochemical staining revealed the absence of eNOS protein in eNOS-/- mice. Aortic endothelial cells derived from eNOS-/- mice displayed only background levels of NOx formation compared with wild-type (WT) cells (88 versus 1990 pmol NOx x h-1/mg protein-1). eNOS-/- mice were hypertensive (mean arterial pressure, 135 +/- 15 versus 107 +/- 8 mm Hg in WT) without the development of cardiac hypertrophy. Coronary hemodynamics, analyzed in Langendorff-perfused hearts, showed no differences either in basal coronary flow or in maximal and repayment flow of reactive hyperemia. Acute NOS inhibition with Nomega-nitro-L-arginine methyl ester (L-NAME) in WT hearts substantially reduced basal flow and reactive hyperemia. The coronary response to acetylcholine (ACh) (500 nmol/L) was biphasic: An initial vasoconstriction (flow, -35%) in WT hearts was followed by sustained vasodilation (+190%). L-NAME significantly reduced vasodilation in WT hearts (+125%) but did not alter the initial vasoconstriction. In eNOS-/- hearts, the initial vasoconstriction was augmented (-70%), whereas the ACh-induced vasodilation was not affected. Inhibition of cyclooxygenase with diclofenac converted the ACh-induced vasodilation into vasoconstriction (-49% decrease of basal flow). This effect was even more pronounced in eNOS-/- hearts (-71%). Our results demonstrate that (1) acute inhibition of eNOS reveals a role for NO in setting the basal coronary vascular tone as well as participation in reactive hyperemia and the response to ACh; (2) chronic inhibition of NO formation in eNOS-/- mutant mice induces no changes in basal coronary flow and reactive hyperemia, suggesting the activation of important compensatory mechanisms; and (3) prostaglandins are the main mediators of the ACh-induced vasodilation in both WT and eNOS-/- mice.

A comparison of the germline potential of differently aged ES cell lines and their transfected descendants.

The germline transmission (g.l.t.) of gene trap or gene targeted mutations by ES-cell-derived chimaeric mice is a crucial step in the generation of stable transgenic lines. The wild-type ES cell lines CJ7, D3 and R1 of different passage numbers and their transfected clone-descendants generated in gene targeting or gene trap experiments were tested for their ability to colonize the germline. The maximal g.l.t. age for wild-type ES cells was equal to passage 26 and for transfected clones was equivalent to passage 32 of parental lines. It is shown that wild-type ES cells of less than a passage 15 should be used for effective production of transgenic g.l.t. clones. A simple system is outlined to evaluate the probability of g.l.t. on the basis of the chimaeric progeny obtained.

Cloning and expression analysis of a novel mouse gene with sequence similarity to the Drosophila fat facets gene.

The Drosophila fat facets (faf) gene is a ubiquitin-specific protease necessary for the normal development of the eye and of the syncytial stage embryo in the fly. Using a gene trap approach in embryonic stem cells we have isolated a murine gene with extensive sequence similarity to the Drosophila faf gene and called it Fam (fat facets in mouse). The putative mouse protein shows colinearity and a high degree of sequence identity to the Drosophila protein over almost its entire length of 2554 amino acids. The two enzymatic sites characteristic of ubiquitin-specific proteases are very highly conserved between mice and Drosophila and this conservation extends to yeast. Fam is expressed in a complex pattern during postimplantation development. In situ hybridisation detected Fam transcripts in the rapidly expanding cell populations of gastrulating and neurulating embryos, in post-mitotic cells of the CNS as well as in the apoptotic regions between the digits, indicating that it is not associated with a single developmental or cellular event. The strong sequence similarity to faf and the developmentally regulated expression pattern suggest that Fam and the ubiquitin pathway may play a role in determining cell fate in mammals, as has been established for Drosophila.

E-cadherin null mutant embryos fail to form a trophectoderm epithelium.

The cell adhesion molecule E-cadherin mediates the compaction process of mouse preimplantation embryos and is important for the maintenance and function of epithelial cell layers. To determine precisely the role of E-cadherin in epithelial biogenesis we monitored the developmental potential of embryos homozygously negative for E-cadherin that were derived from E-cadherin heterozygous transgenic mice. The homozygous negative embryos died around the time of implantation, although they did undergo compaction like their littermate controls, largely due to the presence of residual maternal E-cadherin. At the blastocyst stage, E-cadherin-negative embryos failed to form a trophectodermal epithelium or a blastocyst cavity. These results demonstrate the pivotal role of E-cadherin in one of the most basic morphogenetic events in the development of multicellular organisms, the biogenesis of an epithelium.