Extracellular vesicles (EVs) are biomarkers and modifiers of human disease. EVs secreted by insulin-responsive tissues like skeletal muscle (SkM) and white adipose (WAT) contribute to metabolic health and disease but the relative abundance of EVs from these tissues has not been directly examined. Human Protein Atlas data and directly measuring EV secretion in mouse SkM and WAT using an ex vivo tissue explant model confirmed that SkM tissue secretes more EVs than WAT. Differences in EV secretion between SkM and WAT were not due to SkM contraction but may be explained by differences in tissue metabolic capacity. We next examined how many EVs secreted from SkM tissue ex vivo and in vivo are myofiber-derived. To do this, a SkM myofiber-specific dual fluorescent reporter mouse was created. Spectral flow cytometry revealed that SkM myofibers are a major source of SkM tissue-derived EVs ex vivo and EV immunocapture indicate that ~5% of circulating tetraspanin-positive EVs are derived from SkM myofibers in vivo. Our findings demonstrate that 1) SkM secretes more EVs than WAT, 2) many SkM tissue EVs are derived from SkM myofibers and 3) SkM myofiber-derived EVs reach the circulation in vivo. These findings advance our understanding of EV secretion between metabolically active tissues and provide direct evidence that SkM myofibers secrete EVs that can reach the circulation in vivo.
BACKGROUND Extended embryo culture to blastocyst stage is widely used in IVF and is the default strategy in most clinics. The last decade has witnessed a growing interest in obstetric–perinatal outcomes following blastocyst transfer. Recent studies have challenged the conclusions of systematic reviews that associate risks of preterm birth (PTB) and large for gestational age (LGA) babies with blastocyst transfer. A higher proportion of blastocysts is transferred as frozen-thawed embryos, which may also have added implications. OBJECTIVE AND RATIONALE The aim of this study was to conduct an updated systematic review of the obstetric–perinatal outcomes in singleton pregnancies following blastocyst-stage transfer compared to cleavage-stage transfer in IVF/ICSI cycles. Where deemed appropriate, data were combined in cumulative meta-analyses. SEARCH METHODS Data sources from Medline, EMBASE, CINAHL, Web of Science, the Cochrane Central Register of Clinical Trials and the International Clinical Trials Registry Platform (ICTRP) (1980–2020) were searched using combinations of relevant keywords. Searches had no language restrictions and were limited to human studies. Observational studies and randomized controlled trials comparing obstetric–perinatal outcomes between singleton pregnancies after blastocyst-stage transfer and those after cleavage-stage transfer in IVF/ICSI cycles were sought. Two independent reviewers extracted data in 2 × 2 tables and assessed the methodological quality of the relevant studies using the Critical Appraisal Skills Programme scoring. Cumulative meta-analyses were carried out with independent analysis of pregnancies after fresh and frozen embryo transfers, using the Comprehensive Meta-Analysis software. If provided by included studies, adjusted effect sizes were combined in a sensitivity analysis. OUTCOMES A total of 35 studies were included (n = 520 769 singleton pregnancies). Outcome data suggest singleton pregnancies following fresh blastocyst transfer were associated with higher risk of LGA (risk ratio (RR) 1.14; 95% CI 1.05–1.24) and very PTB (RR 1.17; 95% CI 1.08–1.26) compared to fresh cleavage-stage transfer. Singleton pregnancies following frozen blastocyst transfer were associated with higher risks of LGA (RR 1.17; 95% CI 1.08–1.27), PTB (RR 1.13; 95% CI 1.03–1.24) and caesarean section (RR 1.08; 95% CI 1.03–1.13) but lower risks of small for gestational age (RR 0.84, 95% CI 0.74–0.95) and perinatal mortality (RR 0.70; 95% CI 0.58–0.86). Increased risks of LGA and PTB after frozen blastocyst transfer persisted in the sensitivity analysis, which also showed a significantly increased risk of PTB after fresh blastocyst transfer. Cumulative meta-analyses revealed consistency in prevalence and magnitude of risks for a number of years. Data on other perinatal outcomes are still evolving. WIDER IMPLICATIONS While the available evidence is predominantly reassuring in the context of blastocyst-stage embryo transfer, observational data suggest that blastocyst transfer is associated with a higher risk of LGA. This holds true irrespective of fresh or frozen transfer. Meta-analysis of adjusted data showed an increased risk of PTB with fresh and frozen blastocyst transfer. However, the quality of available evidence ranges from low to very low. Although blastocyst-stage embryo transfer remains the default position in most centres, based on individual risk profile we may need to consider cleavage-stage embryo transfer in some to mitigate the risk of LGA/PTB.
Accurate DNA replication and segregation are critical for maintaining genome integrity and suppressing cancer. Metnase and EEPD1 are DNA damage response (DDR) proteins frequently dysregulated in cancer and implicated in cancer etiology and tumor response to genotoxic chemo- and radiotherapy. Here, we examine the DDR in human cell lines with CRISPR/Cas9 knockout of Metnase or EEPD1. The knockout cell lines exhibit slightly slower growth rates, significant hypersensitivity to replication stress, increased genome instability and distinct alterations in DDR signaling. Metnase and EEPD1 are structure-specific nucleases. EEPD1 is recruited to and cleaves stalled forks to initiate fork restart by homologous recombination. Here, we demonstrate that Metnase is also recruited to stalled forks where it appears to dimethylate histone H3 lysine 36 (H3K36me2), raising the possibility that H3K36me2 promotes DDR factor recruitment or limits nucleosome eviction to protect forks from nucleolytic attack. We show that stalled forks are cleaved normally in the absence of Metnase, an important and novel result because a prior study indicated that Metnase nuclease is important for timely fork restart. A double knockout was as sensitive to etoposide as either single knockout, suggesting a degree of epistasis between Metnase and EEPD1. We propose that EEPD1 initiates fork restart by cleaving stalled forks, and that Metnase may promote fork restart by processing homologous recombination intermediates and/or inducing H3K36me2 to recruit DDR factors. By accelerating fork restart, Metnase and EEPD1 reduce the chance that stalled replication forks will adopt toxic or genome-destabilizing structures, preventing genome instability and cancer. Metnase and EEPD1 are overexpressed in some cancers and thus may also promote resistance to genotoxic therapeutics.
BACKGROUND Registry data from the Human Fertilisation and Embryology Authority (HFEA) show an increase of 40% in IUI and 377% in IVF cases using donor sperm between 2006 and 2016. OBJECTIVE AND RATIONALE The objective of this study was to establish whether pregnancies conceived using donor sperm are at higher risk of obstetric and perinatal complications than those conceived with partner sperm. As more treatments are being carried out using donor sperm, attention is being given to obstetric and perinatal outcomes, as events in utero and at delivery have implications for long-term health. There is a need to know if there is any difference in the outcomes of pregnancies between those conceived using donor versus partner sperm in order to adequately inform and counsel couples. SEARCH METHODS We performed a systematic review and meta-analysis of the outcomes of pregnancies conceived using donor sperm compared with partner sperm. Searches were performed in the OVID MEDLINE, OVID Embase, CENTRAL and CINAHL databases, including all studies published before 11 February 2019. The search strategy involved search terms for pregnancy, infant, donor sperm, heterologous artificial insemination, donor gametes, pregnancy outcomes and perinatal outcomes. Studies were included if they assessed pregnancies conceived by any method using, or infants born from, donor sperm compared with partner sperm and described early pregnancy, obstetric or perinatal outcomes. The Downs and Black tool was used for quality and bias assessment of studies. OUTCOMES Of 3391 studies identified from the search, 37 studies were included in the review and 36 were included in the meta-analysis. For pregnancies conceived with donor sperm, versus partner sperm, there was an increase in the relative risk (RR) (95% CI) of combined hypertensive disorders of pregnancy: 1.44 (1.17–1.78), pre-eclampsia: 1.49 (1.05–2.09) and small for gestational age (SGA): 1.42 (1.17–1.79) but a reduced risk of ectopic pregnancy: 0.69 (0.48–0.98). There was no difference in the overall RR (95% CI) of miscarriage: 0.94 (0.80–1.11), gestational diabetes: 1.49 (0.62–3.59), pregnancy-induced hypertension (PIH): 1.24 (0.87–1.76), placental abruption: 0.65 (0.04–10.37), placenta praevia: 1.19 (0.64–2.21), preterm birth: 0.98 (0.88–1.08), low birth weight: 0.97 (0.82–1.15), high birthweight: 1.28 (0.94–1.73): large for gestational age (LGA): 1.01 (0.84–1.22), stillbirth: 1.23 (0.97–1.57), neonatal death: 0.79 (0.36–1.73) and congenital anomaly: 1.15 (0.86–1.53). WIDER IMPLICATIONS The majority of our findings are reassuring, except for the mild increased risk of hypertensive disorders of pregnancy and SGA in pregnancies resulting from donor sperm. However, the evidence for this is limited and should be interpreted with caution because the evidence was based on observational studies which varied in their quality and risk of bias. Further high-quality population-based studies reporting obstetric outcomes in detail are required to confirm these findings.
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