线粒体与哺乳动物卵母细胞成熟及早期胚胎发育

哺乳动物卵母细胞成熟以及早期胚胎发育,是复杂的生物学过程,必须经历一系列细胞核和细胞质的协调有序变化才能实现。线粒体是细胞质内最重要的细胞器,在卵母细胞成熟和早期胚胎发育过程中,线粒体经历了阶段性的空间再分布,线粒体的结构缺陷和拷贝数的异常都可能影响卵母细胞的成熟和胚胎的发育。线粒体最主要的生物学功能就是产生ATP,为维持卵母细胞和胚胎的正常生命活动提供能量。     

哺乳动物胚胎着床分子机制综述的研究现状

胚胎着床涉及到胚胎和子宫间复杂的关系,是胚胎能否继续发育的重要环节。胚胎发育到囊胚阶段以及子宫内膜同步分化到容受状态是成功着床的关键。着床过程涉及到许多信号通路分子的相互作用,但是其中同步胚胎和子宫状态的调控网络仍有很多谜题未解开。本文总结了目前对于着床的分子调控以及在这个领域中的研究进展,对着床机制的了解有助于阐明女性不明原因的不孕症并且帮助提高胚胎着床率和妊娠率。     

早期胚胎监护方法

对有危险因素的早期妊娠胚胎监护可通过生化监护如人绒毛膜促性腺素、孕酮等与超声动态监护联合,并针对不同类型的危险因素进行个体化筛查,如免疫因素等,遵循胚胎发育规律,评估胚胎生长状态,指导不良妊娠及妊娠并发症的早期干预。     

激素与早期胚胎发育

激素是构成机体内环境的重要因素之一,可以通过对多个组织和器官的直接调节来间接参与早期胚胎的发育调控。越来越多的研究表明,激素还可以通过其受体直接调节早期胚胎的发育,但其调节机制尚不完全清楚。     

Significance of morphological attributes of the early embryo

There are many morphological transformations during development of human embryos that mainly involve phenomena that can be easily assessed in living embryos by simple non-invasive microscopical observation. A clear correlation between pronuclear morphology and the ability of the resulting embryo to continue developing and to implant has been described. There is also general agreement that a positive relationship exists between early embryo morphology and implantation rate. The parameters classically involved in embryo evaluation are: cleavage rate, blastomere symmetry, cytoplasmic appearance, extent of fragmentation and blastomere nuclear status. In this paper, morphological features that have been related to embryo developmental potential are described. Furthermore, the ability of a cumulative classification scheme developed in the laboratory to predict blastocyst formation and implantation is analysed.     

Cryopreservation of early human embryo stages

A short review of freezing procedures applied to early human embryos is given. It is noted that human embryos survived freezing and thawing at a developmental stage of 1. cell to blastocyst. But it seems to be necessary to use for any developmental stage of early embryo a special freezing and thawing method. Embryo survival is correlated with their morphologic features where as neither age of embryos nor developmental stage were involved in freezing and thawing ability.     

Isofluorane inhibits early mouse embryo development in vitro

In vitro development of 2-cell mouse embryos to the blastocyst stage was used to assess the toxicity of isofluorane, nitrous oxide, fentanyl, and meperidine. Isofluorane at concentrations similar to those employed during human oocyte recovery for IVF significantly inhibited mouse embryo development. Since the other agents were without effect, balanced anesthesia with nitrous oxide and narcotics may be preferable to isofluorane for IVF and GIFT.     

Role of mammalian sperm nuclear structure in fertilization and embryo development

Although intact spermatozoon is successfully collected from infertile patients, repeated implantation failure or pregnancy loss are often experienced. Sperm nuclear defects have been thought to be one of the most important reasons for repeated assisted reproductive technology failure. In comparison with other mammalians, characteristic heterogeneity has been found in each mature human sperm nuclei, therefore it is necessary to investigate the significance between fertilization failure, developmental disability and structural abnormality of human sperm nuclei. Furthermore, if close relationships between the heterogeneity of human ejaculated sperm nuclei and DNA fragmentation are defined by analyzing sperm nucleoproteins, it would be clearly shown that impaired sperm chromatin leads to failure of embryo development in vitro or in vivo , so called late paternal effect on embryo development. It will be necessary in the near future to study the strategy for more novel methodology than those previously reported in terms of sperm selection. The present report reviews the roles of mammalian sperm nuclear structure, especially in humans, in fertilization and embryo development after the insemination procedure. (Reprod Med Biol 2006; 5 : 161–168)     

Endometrial secretory proteins enhance early embryo development

Purpose To evaluate the role of endometrial stromal cells and their secretory proteins in early embryo development, two-celled CB6F1 mouse embryos were cultured alone or cocultured with human endometrial stromal cells in various culture conditions.Results The percentage of embryo blastocyst formation, hatching, and outgrowth was significantly greater in (1) coculture with endometrial stromal cells than in a cell-free control when both coculture and control were carried out in protein-free medium or in RPMI 1640 plus 10% fetal calf serum; (2) coculture with hormone (i.e., progesterone plus relaxin)-treated cells than in coculture with hormone-nontreated cells; and (3) media supplemented with isolated endometrial secretory proteins than in media supplemented with BSA (0.35%). Embryo development was not found to be significantly different in coculture and in media supplemented with endometrial secretory protein.Conclusion Our data provides credence to the theory that endometrial stromal cells enhance embryo development by secreting specific proteins that are beneficial to embryo growth in vitro.Presented at the 48th Annual Meeting of the American Fertility Society, New Orleans, Louisiana, October 31–November 5, 1992.     

Clinical value of early cleavage embryo.

OBJECTIVE: This study was undertaken to see if embryo transfer containing early cleavage embryos resulted in better clinical pregnancy rate. METHODS: The treatment outcomes of IVF-ET were retrospectively reviewed. Out of 258 transfer cycles, 160 cycles contained no early cleavage embryos (Group I) and 98 cycles contained at least one early cleavage embryo (Group II). The definition of early cleavage embryo is the presence of two blastomeres 24-26 h after insemination. The implantation rate, clinical pregnancy rate were compared between two groups. Student's t-test and the Mann-Whitney U-test were used for continuous variables, and the Chi-squared (chi(2)) test was used for binary variables. Differences were considered statistically significant at P<0.05. RESULT: The implantation rate and clinical pregnancy rate were 11.6% and 25.6% in Group I, 18.6% and 38.8% in Group II (P<0.05). CONCLUSION: Early cleavage embryos possess greater implantation potential. Embryo transfer containing early cleavage embryos had a better clinical pregnancy rate.     

Thoughts and observations on patterning in early mammalian development

The preimplantation mammalian conceptus shows an impressive ability to develop normally following the loss, gain or rearrangement of cells. This has prompted the view that, unlike in other species, patterning in mammals cannot depend on information that is already present in the zygote before it begins to cleave. However, various findings are hard to reconcile with this conclusion, including evidence that the incidence of monozygotic twinning is sensitive to the conditions to which eggs or very early concepti are exposed. Possible causes of early twinning are discussed, and it is argued that partial hatching of the conceptus through a hernia in the zona pellucida cannot account for all cases. Moreover, it remains questionable whether studies on aggregated morulae and isolated blastomeres really provide compelling evidence against the existence of indispensible patterning information in the egg. Finally, regularities in axial relationships between the blastocyst and zygote have been revealed employing strictly non-invasive techniques. These show that, at least in normal development, patterning begins before cleavage.     

High pregnancy rate after early human embryo freezing

Human embryos produced by in vitro fertilization (IVF) were frozen with 1,2-propanediol as a cryoprotectant. Embryo survival after thawing was related to the presence of a nucleus in frozen cells and decreased with the increasing number of cells in the frozen embryo. None of five embryos frozen 3 or 4 days after IVF survived when thawed. Of 48 early embryos (35 patients) frozen 1 or 2 days after IVF, 42 (87.5%) were transferred in 32 patients. Ten pregnancies were initiated after frozen embryo transfer (ET). If we exclude the three infertile patients who had sexual intercourse in the fertile period, the pregnancy rate for each patient who had 1- or 2-day frozen embryo(s) was 22% (7 of 32). One of the pregnancies was obtained after ET of a 1-cell pronucleated frozen and thawed embryo. The rate of ongoing pregnancies after triple fresh ET was 23%. In patients having four embryos obtained in a single IVF cycle, the expected overall liveborn rate in an IVF-ET program including embryo cryopreservation could theoretically equal that of natural human fertility.     

Sperm origin impact on early human embryo kinetics

IntroductionTime-lapse imaging in embryology is a recent and developing technology, which not only allows constant embryo monitoring but is also a promising non-invasive tool for embryo selection, as it permits the annotation of the embryo's kinetics throughout early development. Several external factors together with patient characteristics are reported as affecting embryo kinetics. Controversy still exists regarding whether sperm origin affects the timing of the embryo's developmental events evaluated by time-lapse monitoring. The aim of this study is to examine the effect of sperm origin on embryonic kinetics in IVF cycles.Material and methodsA retrospective analysis of 161 IVF cycles between 2014 and 2020 were included. The morphokinetic parameters of 220 embryos obtained from couples with severe male factor infertility who underwent testicular sperm extraction (TESE), and 613 embryos from couples with fresh ejaculated spermatozoa were evaluated.ResultsStatistically significant morphokinetic differences were observed between embryos from the TESE group compared to the normozoospermic embryos. In fact, 7 kinetic variables were eventually found to be relevant (p < .05).ConclusionsThis study showed that embryos derived from testicular-retrieved spermatozoa presented delayed cell divisions, compared to ejaculated spermatozoa embryos.     

Impact of the assessment of early cleavage in a single embryo transfer policy

The policy of single embryo transfer (SET) adopted for women <36 years old since 1 July 2003, strongly calls for improvement of embryo selection. A total of 196 cycles in which SET was performed were randomly allocated to two groups. In the first group, early cleavage was assessed (ECA) 25 h after insemination. The embryo with the best score that cleaved early, if present, was selected for transfer. In the second group, early cleavage was not assessed (ECNA) and embryo selection was based solely on the embryo score. Ninety-eight cycles were allocated in the ECA and ECNA group respectively. Early cleavage occurred in 64% of cycles and 32.2% of embryos. Patient population and embryo morphology were similar between the two groups, and similar delivery rates were observed (27.6 versus 24.5% respectively in the ECA and ECNA groups). The assessment of early cleavage as additional parameter did not improve the delivery rate in the single embryo transfer policy.