Impact of GnRH agonist and GnRH antagonist on GDF9 and BMP15 expression in mouse ovaries and oocyte development.

GnRH analogues were widely used for controlld ovary stimulation, but their effects on oocyte quality remain contradictory. This study aimed to explore the influence of GnRH analogues on oocyte quality in mice. A total of 120 mice were randomly assigned to four groups:(i)GnRH-a+PMSG group; (ii) GnRH-ant+PMSG group; (iii) PMSG group; (iv) Control group. Ovaries were collected for quantitative real-time polymerase chain reaction (qRT-PCR) to assess GDF9 and BMP15 mRNA expression, and protein expression were evaluated by western blotting. Moreover, embryo developmental progress in vitro and implantation rate in vivo were recorded. Compared with control group, both GDF9 mRNA and protein expressions were strengthened in PMSG group, but reduced in the presence of GnRH-a or GnRH-ant. The GnRH-a group exhibited decreased BMP15 mRNA expression compared to PMSG group, while the GnRH-ant group did not show the same pattern. BMP15 protein expression were not statisticlly different among the four groups. Notably, there was no statistically difference in the expression of these two factors between GnRH-a and GnRH-ant groups. The percentage of zygotes progressing to the 2-cell stage and percentage of 2-cell advancing to the blastocyst stage were similar in the PMSG group and control group. However, both the GnRH-a and GnRH-ant groups showed decreased embryos development rates compared to other two groups. The embryonic implantation rate in control group (53.3%) was higher than that in the GnRH-a and GnRH-ant groups (33.3% and 30.8%, P<0.05). The difference between the PMSG (45.0%) and GnRHa group was statistically significant (P value of 0.023), but not between the PMSG and GnRH-ant group (P value of 0.486). No statistical difference was confirmed between GnRH-a and GnRH-ant groups. Our findings shed light on the safety of GnRH analogues in ovary stimulation, and highlight the need for further research to establish optimal and effective controlled ovary stimulation protocol.

Protective effect of antioxidants on the pre-maturation aging of mouse oocytes.

Pre-maturation aging of immature oocytes may adversely affect the fate of an oocyte. Oxidative stress is one of the most detrimental factors affecting oocyte developmental competence and maturation during aging. In this study, experiments were designed to examine whether supplementation of antioxidants in a culture medium could protect immature mouse oocytes from damages caused by oxidative stress. Mouse oocytes at germinal vesicle stage were prevented from meiosis resumption and cultured in a medium with or without antioxidants for 12-36 h to allow oocytes to undergo aging. After aging, oocytes were cultured for maturation. Nuclear maturation, mitochondria activity, spindle morphology and DNA integrity were examined after maturation. It was found that antioxidants had protective effects on the oocytes in terms of nuclear maturation, functional mitochondria, spindle morphology and DNA integrity. As aging time was prolonged from 12 to 36 h, the protective effect of antioxidants became more obvious. However, as compared with oocytes without aging, it was found that aging significantly inhibited nuclear maturation, impaired mitochondria function, and damaged the spindle and DNA. These results indicate that pre-maturation aging is detrimental to oocytes' competence to undergo maturation and other cellular activities, and antioxidants can protect oocytes from damages caused by aging.

Casein kinase 1 (α, δ and ε) localize at the spindle poles, but may not be essential for mammalian oocyte meiotic progression.

CK1 (casein kinase 1) is a family of serine/threonine protein kinase that is ubiquitously expressed in eukaryotic organism. CK1 members are involved in the regulation of many cellular processes. Particularly, CK1 was reported to phosphorylate Rec8 subunits of cohesin complex and regulate chromosome segregation in meiosis in budding yeast and fission yeast. (1-3) Here we investigated the expression, subcellular localization and potential functions of CK1α, CK1δ and CK1ε during mouse oocyte meiotic maturation. We found that CK1α, CK1δ and CK1ε all concentrated at the spindle poles and co-localized with γ-tubulin in oocytes at both metaphase I (MI) and metaphase II (MII) stages. However, depletion of CK1 by RNAi or overexpression of wild type or kinase-dead CK1 showed no effects on either spindle organization or chromosome segregation during oocyte meiotic maturation. Thus, CK1 is not the kinase that phosphorylates Rec8 cohesin in mammalian oocytes, and CK1 may not be essential for spindle organization and meiotic progression although they localize at spindle poles.

Arrested human embryos are more likely to have abnormal chromosomes than developing embryos from women of advanced maternal age.

BACKGROUND: Aneuploidy is one of the major factors that result in low efficiency in human infertility treatment by in vitro fertilization (IVF). The development of DNA microarray technology allows for aneuploidy screening by analyzing all 23 pairs of chromosomes in human embryos. All chromosome screening for aneuploidy is more accurate than partial chromosome screening, as errors can occur in any chromosome. Currently, chromosome screening for aneuploidy is performed in developing embryos, mainly blastocysts. It has not been performed in arrested embryos and/or compared between developing embryos and arrested embryos from the same IVF cycle. METHODS: The present study was designed to examine all chromosomes in blastocysts and arrested embryos from the same cycle in patients of advanced maternal ages. Embryos were produced by routine IVF procedures. A total of 90 embryos (45 blastocysts and 45 arrested embryos) from 17 patients were biopsied and analyzed by the Agilent DNA array platform. RESULTS: It was found that 50% of the embryos developed to blastocyst stage; however, only 15.6% of the embryos (both blastocyst and arrested) were euploid, and most (84.4%) of the embryos had chromosomal abnormalities. Further analysis indicated that 28.9% of blastocysts were euploid and 71.1% were aneuploid. By contrast, only one (2.2%) arrested embryo was euploid while others (97.8%) were aneuploid. The prevalence of multiple chromosomal abnormalities in the aneuploid embryos was also higher in the arrested embryos than in the blastocysts. CONCLUSIONS: These results indicate that high proportions of human embryos from patients of advanced maternal age are aneuploid, and the arrested embryos are more likely to have abnormal chromosomes than developing embryos.