The impact of follicle-flushing during oocyte collection on embryo development of in-vitro fertilization.

BACKGROUND: To evaluate the impact of follicle-flushing during oocyte collection on embryo development potential retrospectively. METHODS: A total of 1714 cases, including 133 who experienced retrieval difficulty (repeated follicle-flushing) on the day of oocyte retrieval (difficulty group) and the control 1581 cases (control group), were assessed in this retrospective study. The number of oocytes recovered, two pro-nuclei fertilization (2PN-fertilization), day 3 good-quality embryo and day 5/6 blastocyst utilization rates were compared between the difficulty group and control group correspondingly. Embryo implantation, clinical pregnancy and neonatal outcomes were further analyzed between the two groups in the fresh day- 3 embryo transfer cycles. RESULTS: The number of oocytes recovered in the difficulty group (9.08 ± 4.65) were significantly reduced compared with the control group (12.13 ± 5.27),P < 0.001; The 2PN-fertilization, day 3 good-quality embryo and blastocyst utilization rates were significantly lower in the difficulty group compared with controls (71.7% vs. 75.7%; 52.7% vs. 56.5%; 31.9% vs. 37.0%, all P < 0.05). Embryo implantation in the difficulty group was 53.2%, which was lower than the control value of 58.7%, although not reaching statistical significance. The rate of fresh embryo transfer cycles in the difficulty group was lower than normal ones (51.88% vs. 61.99%, P = 0.026). The pregnancy and live birth rates were similar between the two groups. But the rate of spontaneous miscarriages of the difficulty group was higher than the control group, although not reaching statistical significance. The neonatal outcomes had no statistical difference between the two groups. CONCLUSIONS: Oocyte retrieval difficulty, which include repeated flushing and the corresponded extending time required for oocyte recovery, significantly reduced day 3 good-quality embryo and blastocyst utilization rates of these patients. But the live birth rate had no difference between the difficulty group and the normal ones.

RNF2/Ring1b negatively regulates p53 expression in selective cancer cell types to promote tumor development.

Large numbers of studies have focused on the posttranslational regulation of p53 activity. One of the best-known negative regulators for p53 is MDM2, an E3 ubiquitin ligase that promotes p53 degradation through proteasome degradation pathways. Additional E3 ligases have also been reported to negatively regulate p53. However, whether these E3 ligases have distinct/overlapping roles in the regulation of p53 is largely unknown. In this study, we identify RNF2 (ring finger protein 2) as an E3 ligase that targets p53 for degradation. The E3 ligase activity of RNF2 requires Bmi1 protein, a component of the polycomb group (PcG) complex. The up-regulation of p53 does not affect RNF2 expression. Unlike Mdm2, RNF2 only degrades p53 in selective cell lines, such as those from germ-cell tumors. The knockdown of RNF2 induces apoptosis, which can be rescued through the reduction of p53 expression. Moreover, the down-regulation of RNF2 expression in germ-cell tumors significantly reduces tumor cell growth, while the simultaneous down-regulation of both genes restores tumor cell growth in vitro and in tumor xenograft models. Furthermore, a reverse correlation between RNF2 and p53 expression was detected in human ovarian cancer tissues. Together, these results indicate that RNF2 is an E3 ligase for p53 degradation in selective cells, implicating RNF2 as a therapeutic target to restore tumor suppression through p53 in certain tumor cells.

Activity of long-chain acyl-CoA synthetase is required for maintaining meiotic arrest in Xenopus laevis.

In most vertebrates, fully grown oocytes are arrested in meiotic prophase I and only resume the cell cycle upon external stimuli, such as hormones. The proper arrest and resumption of the meiotic cycle is critical for reproduction. A Galpha(S) signaling pathway essential for the arrest is conserved in organisms from Xenopus to mouse and human. A previous gene association study implicated that mutations of human ACSL6 may be related to premature ovarian failure. However, functional roles of ACSL6 in human infertility have yet to be reported. In the present study, we found that triacsin C, a potent and specific inhibitor for ACSL, triggers maturation in Xenopus and mouse oocytes in the absence of hormone, suggesting ACSL activity is required for the oocyte arrest. In Xenopus, acsl1b may fulfill a major role in the process, because inhibition of acsl1b by knocking down its RNA results in abnormal acceleration of oocyte maturation. Such abnormally matured eggs cannot support early embryonic development. Moreover, direct inhibition of protein palmitoylation, which lies downstream of ACSLs, also causes oocyte maturation. Furthermore, palmitoylation of Galpha(s), which is essential for its function, is inhibited when the ACSL activity is blocked by triacsin C in Xenopus. Thus, disruption of ACSL activity causes inhibition of the Galpha(s) signaling pathway in the oocytes, which may result in premature ovarian failure in human.