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Objective To investigate the presence of viral RNA in human semen of patients with severe acute-respiratory syndrome coronavirus 2 (SARS-CoV-2) and to evaluate its presence and relevance in semen parameters. Design Pilot cohort study. Setting University hospital. Patient(s) Thirty-four men were distributed as: 1) patients in convalescence (patients with confirmed SARS-CoV-2 infection in pharyngeal swab according to reverse-transcription polymerase chain reaction [RT-PCR] or antibodies); 2) negative control group (no antibodies); and 3) patients with an acute infection (detection of SARS-CoV-2 in pharyngeal swab). Intervention Semen and a blood sample were collected from each individual. Main Outcome Measure(s) Analysis of semen quality according to the World Health Organization standards. Detection of SARS-CoV-2 by RT-PCR in the native semen sample and after density gradient preparation. Confirmation of immunoglobulin (Ig) A und IgG antibodies in the blood. Result(s) Eighteen semen samples from recovered men were obtained 8–54 days after absence of symptoms, 14 from control subjects, and 2 from patients with an active COVID-19 infection. No RNA was detected by means of RT-PCR in the semen, including semen samples from two patients with an acute COVID-19 infection. Subjects with a moderate infection showed an impairment of sperm quality. Conclusion(s) A mild COVID-19 infection is not likely to affect testis and epididymis function, whereas semen parameters did seem impaired after a moderate infection. SARS-CoV-2 RNA could not be detected in semen of recovered and acute COVID-19–positive men. This suggests no viral transmission during sexual contact and assisted reproductive techniques, although further data need to be obtained.

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.

Endometrial epithelial cells are known to undergo apoptosis during trophoblast invasion. We postulate that the cell surface molecule Syndecan-1 which is expressed on endometrial cells and syncytiotrophoblast is important for implantation in general and especially for induction of maternal cell apoptosis during trophoblast invasion because Syndecan-1's influence on apoptotic susceptibility of cancer cells is already described in the literature. Using the human endometrial epithelial cell line RL95-2, a new stable cell line with Syndecan-1 knockdown was generated. Via antibody array analysis, a significant decrease in the expression of anti-apoptotic proteins like inhibitors of apoptosis, Clusterin, heme oxygenase (HO-2), heat shock protein (HSP)27 and -70 and Survivin due to the Syndecan-1 knockdown was discovered. Correspondingly, active Caspase-3 as an indicator for apoptosis was increased more severely in these cells compared with unmodified RL95-2 after treatment with implantation-related stimuli, which are the cytokines interleukin-1β, interferon-γ, tumor necrosis factor-α and transforming growth factor-β1 and an anti-Fas antibody. Furthermore, a treatment with a combination of all factors caused a higher Caspase-3 induction compared with each single treatment. These results demonstrate that Syndecan-1 is involved in the control of apoptosis in RL95-2 cells and therefore may affect the fine tuning of apoptosis in endometrial epithelium regulating the embryo's invasion depth as a crucial step for regular implantation followed by successful pregnancy.

The human oviduct serves as a conduit for spermatozoa in the peri-ovulatory phase and nurtures and facilitates transport of the developing embryo for nidation during the luteal phase. Interactions between the embryo and oviductal epithelial surface proteins and secreted products during embryo transit are largely undefined. This study investigated gene expression in the human oviduct in the early luteal versus follicular phases to identify candidate genes and biomolecular processes that may participate in maturation and transport of the embryo as it traverses this tissue. Oviductal RNA was hybridized to oligonucleotide arrays and resulting data were analysed by bioinformatic approaches. There were 650 genes significantly down-regulated and 683 genes significantly up-regulated (P

A successful implantation of a mammalian embryo into the maternal endometrium depends on a highly synchronized fetal–maternal dialogue involving chemokines, growth factors, and matrix-modifying enzymes. A growing body of evidence suggests an important role for proteinases playing a role in matrix degeneration and enhancing the embryo's invasive capacity and influencing the mother's immunological status in favor of the conceptus. This study focused on the expression of cathepsin S (CTSS) and its inhibitors in the murine fetal–maternal interface as well as the detection of the cellular sources of either proteinase and inhibitors. Nested RT-PCR for detection of embryonic mRNAs, immunohistochemistry of maternal and fetal tissues in B6C3F1 mice, and FACS analysis for determination of immunocompetent cell population were applied. This study shows that the cysteine proteinase CTSS is upregulated in the stroma of the implantation site, and that pregnancy induces an influx of CTSS-positive uterine natural killer cells. Compared to maternal tissues, the CTSS inhibitors cystatin F and C, but not the proteinase itself, are expressed in blastocysts. In conclusion, CTSS underlies a hormonal regulation in the maternal tissue and therewith most likely supports the embryonic implantation. The invading embryo regulates the depth of its own invasion through the expression of the cathepsin inhibitors and furthermore, interleukin-6 to activate CTSS in maternal tissues. Additionally, the observed decrease in CD3+cells leads to the hypothesis that cells of the cytotoxic T-cell group are down-regulated in the decidua to support the implantation and ensure the survival of the embryo.

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, p0.05). 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.