MI Stage Research Articles

Oocyte cryopreservation and in vitro culture affect calcium signalling during human fertilization

What are the precise patterns of calcium oscillations during the fertilization of human oocytes matured either in vivo or in vitro or aged in vitro and what is the effect of cryopreservation? Human oocytes matured in vivo exhibit a specific pattern of calcium oscillations, which is affected by in vitro maturation, in vitro ageing and cryopreservation. Oscillations in cytoplasmic calcium concentration are crucial for oocyte activation and further embryonic development. While several studies have described in detail the calcium oscillation pattern during fertilization in animal models, studies with human oocytes are scarce. This was a laboratory-based study using human MII oocytes matured in vivo or in vitro either fresh or after cryopreservation with slow freezing or vitrification. Altogether, 205 human oocytes were included in the analysis. In vivo and in vitro matured human oocytes were used for this research either fresh or following vitrification/warming (V/W) and slow freezing/thawing (F/T). Human oocytes were obtained following written informed consent from patients undergoing ovarian hyperstimulation. For the calcium pattern analysis, oocytes were loaded with the ratiometric calcium indicator fluorescent dye Fura-2. Following ICSI using sperm from a single donor, intracellular calcium was measured for 16 h at 37°C under 6% CO(2). The calcium oscillation parameters were calculated for all intact oocytes that showed calcium oscillations and were analyzed using the Mann-Whitney U-test. Human in vivo MII oocytes display a specific pattern of calcium oscillations following ICSI. This pattern is significantly affected by in vitro ageing, with the calcium oscillations occurring over a longer period of time and with a lower frequency, shorter duration and higher amplitude (P < 0.05). In vitro matured oocytes from the GV and MI stage exhibit a different pattern of calcium oscillations with calcium transients being of lower frequency and shorter duration compared with in vivo matured MII. In MI oocytes that reached the MII stage within 3 h the calcium oscillations additionally appear over a longer period of time (P < 0.05). In vivo MII oocytes show a different calcium oscillation pattern following V/W with calcium oscillations occurring over a longer period of time, with a higher amplitude and a lower frequency (P < 0.05). In vitro matured oocytes, either from the GV or the MI stage, also display an altered pattern of calcium oscillations after V/W and the parameters that were similarly affected in all these oocyte groups are the frequency and the amplitude of the calcium transients. Slow freezing/thawing differentially affects the calcium oscillation pattern of in vitro matured and in vitro aged oocytes. The relationship between a specific pattern of calcium oscillations and subsequent human embryonic development could not be evaluated since the calcium indicator used and the high-intensity excitation light impair development. Furthermore, all oocytes were derived from stimulated cycles and immature oocytes were denuded prior to in vitro maturation. Our data show for the first time how calcium signalling during human fertilization is affected by oocyte in vitro maturation, in vitro ageing as well as V/W and slow freezing/thawing. The analysis of calcium oscillations could be used as an oocyte quality indicator to evaluate in vitro culture and cryopreservation techniques of human oocytes. This work was supported by a clinical research mandate from the Flemish Foundation of Scientific Research (FWO-Vlaanderen, FWO09/ASP/063) to F.V.M, a fundamental clinical research mandate from the FWO-Vlaanderen (FWO05/FKM/001) to P.D.S and a Ghent University grant (KAN-BOF E/01321/01) to B.H. The authors have no conflict of interest to declare.

Successful Pregnancy Following Dual Triggering Concept (rhCG + GnRH Agonist) in a Patient Showing Repetitive Inmature Oocytes and Empty Follicle Syndrome: Case Report

After ovarian stimulation some oocytes collected for IVF cycles are arrest at the GV o MI stage at the time of retrieval despite controlled ovarian stimulation (COS) and a correct administration of hCG. However, it is unusual to have a complete failure of oocyte maturation after COS, especially in presence of normally growing follicles. Empty follicle syndrome (EFS) is a condition of uncertain etiology in which no oocytes are retrieved from apparently normally growing ovarian follicles with normal estradiol levels after ovarian stimulation for assisted reproductive techniques. In genuine EFS, dysfunction of the folliculogenesis seems to be the most plausible etiology. We report a case of primary infertility in which four consecutive IVF attempts yielded immature oocytes or EFS. Finally, at a fifth attempt the use of hCGr + GnRHa (dual triggering) for final follicular maturation resulted in a successful live birth. doi: http://dx.doi.org/10.4021/jmc1055w

Fertilization and pregnancy potential of immature oocytes from stimulated intracytoplasmic sperm injection cycles

ObjectiveWe evaluated the fertilization potential of immature oocytes obtained from controlled ovarian hyperstimulation cycles of patients undergoing ICSI.MethodsWe retrospectively analyzed 463 ICSI cycles containing at least one immature oocyte at oocyte denudation. ICSI was performed on mature oocytes at oocyte denudation (metaphase-II [MII] oocytes) and the oocytes that extruded the first polar body between oocyte denudation and ICSI (MI-MII oocytes). Fertilization and early embryonic development were compared between MII and MI-MII oocytes. To investigate the pregnancy potential of MI-MII oocytes, the pregnancy outcome was analyzed in 24 ICSI cycles containing only immature oocytes at retrieval.ResultsThe fertilization rate of MI-MII oocytes (37.0%) was significantly lower than that of MII oocytes (72.3%). The rates of delayed embryos and damaged embryos did not significantly differ. Eighty-one immature oocytes were retrieved in 24 cycles that retrieved only immature oocytes and 61 (75.3%) of them were in the MI stage. ICSI was performed on 36 oocytes (59.0%) that extruded the first polar body before ICSI and nine MI-MII oocytes (25.0%) were fertilized. Embryo transfers were performed in five cycles. Pregnancy was observed in one cycle, but it ended in biochemical pregnancy.ConclusionIn ICSI cycles, oocytes that extruded the first polar body between denudation and ICSI can be used as a source of oocytes for sperm injection. However, their fertilization and pregnancy potential are lower than that of mature oocytes. Therefore, ovarian stimulation should be performed carefully for mature oocytes obtained at retrieval, especially in cycles with a small number of retrieved oocytes.

Overexpression of SETβ, a protein localizing to centromeres, causes precocious separation of chromatids during the first meiosis of mouse oocyte

Chromosome segregation in mammalian oocyte meiosis is an error-prone process, and any mistake in this process may result in aneuploidy, which is the main cause of infertility, abortion and many genetic diseases. It is now well known that shugoshin and protein phosphatase 2A (PP2A) play important roles in the protection of centromeric cohesion during the first meiosis. PP2A can antagonize the phosphorylation of rec8, a member of the cohesin complex, at the centromeres and thus prevent cleavage of rec8 and so maintain the cohesion of chromatids. SETβ is a protein that physically interacts with shugoshin and inhibits PP2A activity. We thus hypothesized that SETβ might regulate cohesion protection and chromosome segregation during oocyte meiotic maturation. Here we report for the first time the expression, subcellular localization and functions of SETβ during mouse oocyte meiosis. Immunoblotting analysis showed that the expression level of SETβ was stable from the germinal vesicle stage to the MII stage of oocyte meiosis. Immunofluorescence analysis showed SETβ accumulation in the nucleus at the germinal vesicle stage, whereas it was targeted mainly to the inner centromere area and faintly localized to the interchromatid axes from germinal vesicle breakdown to MI stages. At the MII stage, SETβ still localized to the inner centromere area, but could relocalize to kinetochores in a process perhaps dependent on the tension on the centromeres. SETβ partly colocalized with PP2A at the inner centromere area. Overexpression of SETβ in mouse oocytes caused precocious separation of sister chromatids, but depletion of SETβ by RNAi showed little effects on the meiotic maturation process. Taken together, our results suggest that SETβ, even though it localizes to centromeres, might not be essential for chromosome separation during mouse oocyte meiotic maturation, although its forced overexpression causes premature chromatid separation.

Knockdown of UCHL5IP causes abnormalities in γ-tubulin localisation, spindle organisation and chromosome alignment in mouse oocyte meiotic maturation

UCHL5IP is one of the subunits of the haus complex, which is important for microtubule generation, spindle bipolarity and accurate chromosome segregation in Drosophila and human mitotic cells. In this study, the expression and localisation of UCHL5IP were explored, as well as its functions in mouse oocyte meiotic maturation. The results showed that the UCHL5IP protein level was consistent during oocyte maturation and it was localised to the meiotic spindle in MI and MII stages. Knockdown of UCHL5IP led to spindle defects, chromosome misalignment and disruption of γ-tubulin localisation in the spindle poles. These results suggest that UCHL5IP plays critical roles in spindle formation during mouse oocyte meiotic maturation.

Effect of cryotop vitrification method on oocytes at different meiotic stages and embryo development in vitro

The effectiveness of existing procedures based on viable embryos per oocyte frozen remains low compared to use of fresh oocytes in cattle, and the probable causes of the freezing-induced reduction in oocyte developmental competence include chromosome, cytoskeleton disruption, or even the choice of the frozen stage of the oocytes. In the present study, after vitrification, the survival rate of GV and MI oocytes were significantly lower than those in MII. The vitrifid GV oocyte showed some chromosomes dispersed and less condensed, The vitrifid MI oocytes with “Fading’’ and discontinuous staining pattern were as having an abnormal microfilament distribution. The stage of GV and MI, both cleavage rate and blastocyst formation rate were reduced significantly. Therefore, the cryopreservation of GV or MI oocytes seems could not instead of the MII oocytes.

Involvement of microRNA-335-5p in cytoskeleton dynamics in mouse oocytes

MicroRNA is a short RNA molecule expressed in eukaryotic cells that is involved in multiple processes, including translational repression, target degradation and gene silencing. However, its specific role(s) in these processes remains largely unknown, especially in terms of germ cell development. The present study identified a microRNA, namely miR-335-5p, that is involved in mouse oocyte meiosis. MiR-335-5p was highly expressed in oocytes, but levels decreased markedly shortly after fertilisation. Microinjection of miR-335-5p or its inhibitor into oocytes resulted in a higher proportion of 2-cell-like MII oocytes and oocytes at the germinal vesicle breakdown and/or MI stage, indicating failure of asymmetric oocyte division. This may be due to regulation of actin because perturbation of miR-335-5p resulted in reduced expression of actin nucleator Daam1, a member of the Formin family. Moreover, injection of miR-335-5p or its inhibitor resulted in aberrant spindle morphology, namely an elongated spindle and multiple poles spindle. After injection of oocytes, levels of phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) decreased, suggesting that miR-335-5p may regulate spindle formation via the mitogen-activated protein kinase pathway. Overexpression and inhibition of miR-335-5p had no effect on embryo development. Together, the results of the present study indicate that miR-335-5p is a novel regulator expressed in oocytes that is involved in cytoskeleton dynamics.

The G Protein Coupled Receptor 3 Is Involved in cAMP and cGMP Signaling and Maintenance of Meiotic Arrest in Porcine Oocytes

The arrest of meiotic prophase in mammalian oocytes within fully grown follicles is dependent on cyclic adenosine monophosphate (cAMP) regulation. A large part of cAMP is produced by the Gs-linked G-protein-coupled receptor (GPR) pathway. In the present study, we examined whether GPR3 is involved in the maintenance of meiotic arrest in porcine oocytes. Expression and distribution of GPR3 were examined by western blot and immunofluorescence microscopy, respectively. The results showed that GPR3 was expressed at various stages during porcine oocyte maturation. At the germinal vesicle (GV) stage, GPR3 displayed a maximal expression level, and its expression remained stable from pro-metaphase I (MI) to metaphase II (MII). Immunofluorescence staining showed that GPR3 was mainly distributed at the nuclear envelope during the GV stage and localized to the plasma membrane at pro-MI, MI and MII stages. RNA interference (RNAi) was used to knock down the GPR3 expression within oocytes. Injection of small interfering double-stranded RNA (siRNA) targeting GPR3 stimulated meiotic resumption of oocytes. On the other hand, overexpression of GPR3 inhibited meiotic maturation of porcine oocytes, which was caused by increase of cGMP and cAMP levels and inhibition of cyclin B accumulation. Furthermore, incubation of porcine oocytes with the GPR3 ligand sphingosylphosphorylcholine (SPC) inhibited oocyte maturation. We propose that GPR3 is required for maintenance of meiotic arrest in porcine oocytes through pathways involved in the regulation of cAMP and cGMP.

Differences in transcriptomic profiles of human cumulus cells isolated from oocytes at GV, MI and MII stages after in vivo and in vitro oocyte maturation

Oocyte maturation and competence to development depends on its close relationship with cumulus cells (CCs). However, the maturation conditions of human cumulus-oocyte complexes (COCs) might affect gene expression in both oocyte and CCs. We thus compared the transcriptome profiles of CCs isolated from in vivo and in vitro matured COCs at different nuclear maturation stages. Three groups of CCs from patients who underwent ICSI were included: CCs of patients with polycystic ovary syndrome (PCOS) referred for in vitro maturation (IVM), CCs from patients with PCOS for in vivo maturation (used as controls) and CCs from normal responders referred for in vivo maturation. CCs were isolated from COCs at the germinal vesicle, metaphase I and metaphase II stages. Microarray technology was used to analyse the global gene expression and significance analysis of microarray to compare the expression profiles of CCs from COCs at different nuclear maturation stages following IVM or in vivo maturation. Selected genes were validated by RT-qPCR. In CCs isolated after IVM, genes related to cumulus expansion and oocyte maturation, such as EREG, AREG and PTX3, were down-regulated, while cell cycle-related genes were up-regulated in comparison with CCs from in vivo matured COCs from PCOS and normal responder patients. Moreover, irrespective of the stage of oocyte maturation, genes involved in DNA replication, recombination and repair were up-regulated in CCs after IVM. The CC transcriptomic signature varies according to both the oocyte maturation stage and the maturation conditions. Our findings suggest a delay in the acquisition of the mature CC phenotype following IVM, opening a new perspective for the improvement in IVM conditions.

Changes in histone acetylation during oocyte meiotic maturation in the diabetic mouse

Although there is considerable evidence that diabetes can adversely affect meiosis in mammalian oocytes, acetylation status of oocytes in a diabetic environment remains unclear. The objective was to determine acetylation or deacetylation patterns (based on immunostaining) of H3K9, H3K14, H4K5, H4K8, H4K12, and H4K16 sites at various stages during meiosis in murine oocytes from control and diabetic mice. According to quantitative real time polymerase chain reaction (qPCR), mean ± SEM relative expression of Gcn5 (1.70 ± 0.14 at metaphase [M]I and 1.27 ± 0.01 at MII, respectively), Ep300 (1.74 ± 0.04 at MI and 1.80 ± 0.001 at MII), and Pcaf (2.01 ± 0.03 at MI and 1.41 ± 0.18 at MII) mRNA in oocytes from diabetic mice were higher than those from controls (P < 0.05), whereas there was no difference (P > 0.05) during the germinal vesicle (GV) stage between the two groups (1.23 ± 0.04 for Gcn5, 0.82 ± 0.06 for Ep300, and 0.80 ± 0.07 for Pcaf). Conversely, relative mRNA expression concentrations of Hdac1, Hdac2, Hdac3, Sirt1 and Sirt2 during the germinal vesicle stage were lower in oocytes of diabetic mice (0.24 ± 0.03 for Hdac1, 0.11 ± 0.001 for Hdac2, 0.31 ± 0.03 for Hdac3, 0.28 ± 0.02 for Sirt1, and 0.55 ± 0.02 for Sirt2; P < 0.05). Similarly, the expression concentrations of these genes at the MI stage were lower in oocytes from diabetic mice (0.79 ± 0.12 for Hdac1, 0.72 ± 0.001 for Hdac2, 0.02 ± 0.001 for Sirt1, and 0.84 ± 0.08 for Sirt2; P < 0.05). Their expression concentrations at the MII stage were also lower in oocytes from diabetic mice (0.46 ± 0.03 for Hdac1, 0.93 ± 0.01 for Hdac2, 0.56 ± 0.01 for Hdac3, 0.01 ± 0.002 for Sirt1, and 0.84 ± 0.04 for Sirt2; P < 0.05). At the MI stage, however, there was no difference in the expression of Hdac3 between the two groups of oocytes (0.96 ± 0.03; P > 0.05). Taken together, diabetes altered the intracellular histone modification system, which may have contributed to changes in histone acetylation, and may be involved in the compromised maturation rate of oocytes in diabetic humans.

Delivering Quality Motivational Interviewing Training: A Survey of MI Trainers

The MI community places an emphasis on attempting to understand the training process. Yet little is known about what MI trainers perceive as the important variables in training MI. A mixed method survey of 92 members of the Motivational Interviewing Network of Trainers was used to elicit important variables to consider in providing quality MI training. Based on results, it appears that MI trainers are familiar with Miller and Moyers’ (2006) eight stages of learning MI and used them to develop trainings. However, the respondents reported that they do not use these stages to evaluate trainings. Moreover, the respondents emphasized the importance of trainee and trainer variables in organizing trainings. They also provided varied opinions regarding the important ingredients in developing MI competency. The authors discuss the need for further empirical exploration of the important training ingredients and the eight stages model. Finally, the need for exploration of how these ingredients help trainees develop competency and future focus on the integration of best practices in adult learning is discussed.

Successful pregnancy following a novel endometrial preparation in a PCOS patient undergoing IVM: a case report

In-vitro fertilization (IVF) relies heavily on controlled ovarian stimulation to increase the number of available oocytes and embryos, and therefore the pregnancy rate. However, the side effects, such as nausea, mood swings, menopausal symptoms, ovarian hyperstimulation syndrome (OHSS), and potential cancer risk of ovarian stimulation may not be avoided. Therefore, the recovery of immature oocytes followed by in-vitro maturation (IVM) and fertilization is an attractive alternative to avoid the side effects of using gonadotrophin stimulation. In IVM, immature oocytes are retrieved from unstimulated or minimally stimulated cycles, then cultured using IVM culture media for maturation in vitro [1]. In comparison with conventional IVF, IVM technology is generally associated with the absence of OHSS, lower cost, and fewer complications. However, the efficiency of existing IVM technique is suboptimal because embryos generated from IVM exhibit frequent cleavage blocks and low implantation rate [2]. Women with polycystic ovarian syndrome (PCOS) are considered as the target population for this approach. This group of patients is extremely sensitive to ovarian stimulation and have a high potential for developing of OHSS [3]. In recent years, many improvements have been made in clinical and laboratory aspects of IVM treatment which have resulted in better pregnancy outcomes [4]. It was shown that pretreatment with FSH in the early days of folliculogenesis phase may increase the number of retrieved immature oocytes and/or maturation potential [5, 6]. In addition, hCG priming promotes some GV oocytes to reach the MI stage and increases the maturation rate of immature oocytes in vitro setting. Despite increased pregnancy rates following IVM in recent years, implantation rates are still lower than conventional IVF cycles. One possible explanation may be related to insufficient endometrial preparation during IVM cycles before ET [4, 7]. Here, we aim to report a novel endometrial preparation method in a PCOS case undergoing IVM. Case report A 33 years old patient with history of primary infertility for 3 years was referred to our program for infertility treatment. She was diagnosed as PCOS according to Rotterdam criteria [8] with history of acne, hirsutism and oligomenorrhea. The clinical profile showed that she had BMI = 28, LH = 4, FSH = 1.5, LH/FSH > 2. The patient had history of both clomiphen failure and metformin administration for more than 6 months. She also underwent laparoscopy and ovarian cauterization approximately 1 year before. Infertility work up for the husband showed abnormal sperm analysis including a count of 28 millions/ml, <20% progressive motility and <14% normal morphology according to WHO criteria. A recent varicoceletomy did not improve semen quality for her husband. In her first treatment cycle and due to a high response to the antagonist protocol and to avoid the risk of severe OHSS, it was decided to cancel the cycle, and to continue the treatment using IVM techniques. After progesterone withdrawal bleeding, FSH priming was delayed until 13th day of the cycle when endometrial thickness reached 7 mm. At that time, FSH priming started, 75 IU/day of FSH (Serono, Aubnne, Switzerland) was injected for 3 days, followed by an injection of 10,000 IU hCG (Pregnyl, Organon, Netherlands). Follicular diameters were less than 10 mm at the time of hCG injection. On the day of hCG injection, both endometrial thickness and level of estradiol were measured. Oocytes were retrieved 36 h after hCG injection using a 19-gauge aspiration needle under transvaginal ultrasound guidance. A total of 10 immature oocytes were retrieved, including 3 at GV stage, 5 at MI stage, and 2 were degenerated. Immature oocytes were transferred to IVM culture media (SAGE Co., CT) for 28 h, when 5 oocytes reached MII stage. The rest of oocytes were arrested. The mature oocytes were microinjected with husbands’ sperm and normal fertilization was confirmed when two polar bodies with two pronuclei were observed 18–20 h after insemination. A total of 3 oocytes were fertilized and 3 four cells embryos (grade B) were transferred 2 days after microinjection using ET catheter (Labotect, Gottingen, Germany). Lutheal phase support was done with 100 mg progesterone in oil (Aburaihan Co, Tehran, Iran) injected daily. Estradiol valerate (Aburaihan C,Tehran, Iran) was taken orally at the dose of 6 mg/day from day of oocytes retrieval, and continued until confirmation of fetal heart by sonography. βhCG was measured 14 days after ET, which was reported positive (>180 IU/L). A healthy baby girl was born at 39 weeks of pregnancy by cesarean section. The baby weigh at the time of birth was 3,500 g with the apgar of 9/10.

200 SYNCHRONIZATION OF OOCYTE MEIOTIC MATURATION IN SUPEROVULATED MICE IMPROVES IN VITRO FERTILIZATION RATE

In vitro synchronization of oocyte nuclear and cytoplasmic maturation has been found to improve the IVF rate of ovarian oocytes in several species, including humans, in comparison with nonsynchronized in vitro-matured oocytes. Here, we tested the hypothesis that synchronization of oocyte meiotic maturation by an in vivo system in superovulated mice would increase the oocyte fertilization rate when compared to that of conventional superovulated oocytes. Recently, we observed that cilostazol (CZL), a PDE3-I, was able to inhibit mouse oocyte meiotic maturation in both in vitro and in vivo systems. Administering CZL at 7.5 mg, 4 or 7 h pre-hCG allowed retrieval of ovulated oocytes of which &gt;95% were at MI stage, scored by Nikon stereo microscope (SMZ 1500). A conventional superovulation program was adapted in all treated and their control groups, in which mice were injected with eCG and after 48 h with hCG (7.5 IU for each hormone). On the second morning, 13 to 14 h post-hCG, mice were killed and oocytes were collected from oviducts and in vitro fertilized (control). For the treated groups, CZL was administered in a single 7.5 mg oral dose (gavage) 4 or 7 h before the hCG injection. On the second morning, CZL-treated animals were killed at the same timing as control animals and oocytes were retrieved from the oviduct and in vitro matured for 6 h (for those gavaged with CZL, 4 h pre-hCG) or 3 h (for those gavaged with CZL, 7 h pre-hCG) to MII oocytes before IVF. These groups were designated as in vivo-in vitro synchronized/matured oocytes. In other groups treated with CZL, 4 or 7 h pre-hCG, the ovulated oocytes were allowed to mature in the oviduct (full in vivo synchronization and maturation) and oocytes were retrieved and fertilized with the same fertilization timings as the in vivo-in vitro synchronized/matured oocytes. Oocytes were cultured for 1 day after IVF and examined for cleavage. Statistical differences were analyzed by cross-tabulated chi-square test. The full in vivo synchronization and maturation (for both CZL dose timings of 4 and 7 h pre-hCG) gave significantly higher early embryonic development rates compared with those of the control [89% (n = 219) and 92.2% (n = 374) vs 81.8% (n = 198); P = 0.034 and P &lt; 0.0001, respectively]. The in vivo-in vitro synchronized/matured oocytes (CZL dose timing at 7 h, but not 4 h pre-hCG) gave significantly higher early embryonic development rates compared with those of the control [88.5% (n = 339) vs 83.4% (n = 458), respectively; P = 0.043]. However, the increase of the IVF rate of the oocytes from mice treated with CZL, 4 h pre-hCG, in the in vivo-in vitro synchronized/matured group was not significantly different from the control group [88.5% (n = 399) vs 83.4% (n = 458), respectively; P = 0.43]. It is concluded from the present study that synchronization of oocyte meiotic maturation by the in vivo and in vivo-in-vitro protocols can increase the IVF rate of oocytes in superovulated mice.

45 THE EFFECT OF MEIOTIC STAGE OF BOVINE OOCYTES ON THE SURVIVAL OF VITRIFIED CUMULUS–OOCYTE COMPLEXES

Vitrification is a rapid freezing method in which cells/tissues are frozen in a glass state without ice crystal formation. However, vitrification of bovine oocytes is challenging due to their complex structure and sensitivity to chilling. Oocytes at the germinal vesicle (GV) stage of maturation are thought to be less prone to chromosomal and microtubular damage during cryopreservation because no spindle is present and genetic material is contained within the nucleus. However, immature oocytes are thought to be more sensitive to osmotic stress and have lower cell membrane stability than mature, metaphase II (MII) stage oocytes. The present studies aimed to validate the in vitro culture system used in our laboratory and to evaluate the effect of vitrification of bovine cumulus-oocyte complexes (COC) at different meiotic stages on their in vitro maturation (IVM), cleavage and early embryo development. Analyses were conducted on each dataset with PROC GLIMMIX in SAS using binary distribution (for yes/no response variable) and considering replicate as a random factor. In Experiment 1, meiotic progression of oocytes was evaluated at different time intervals during IVM. The following COC stages were predominantly found at different IVM time intervals: GV (89%) at 0 h, GV (47%) and germinal vesicle breakdown (GVBD; 44%) at 6 h, metaphase I (MI; 90%) at 12 h and MII (84%) at 22 h (n &gt; 62 oocytes at each time group). In Experiment 2, bovine COC at 0, 6, 12 and 22 h of IVM were exposed to vitrification solution (15% dimethyl sulfoxide + 15% ethylene glycol + 0.5 M sucrose + 20% CS in TCM-199), loaded onto a cryotop device and vitrified by plunging in liquid nitrogen. Following warming (1 min in 0.5 M sucrose + 20% CS in TCM-199), COC completed 22 h of IVM and the nuclear stage was evaluated with lamin A/C-4′6-diamidino-2-phenylindole staining. Upon completion of 22 h of IVM, 23, 23, 35 and 89% of oocytes from 0-, 6-, 12- and 22-h groups, respectively were detected at MII (P &lt; 0.0001). In Experiment 3, cleavage and embryo development of oocytes vitrified at 0, 12 and 22 h of IVM were evaluated. The cleavage rate did not differ among vitrification groups (i.e. 14% at 0 h, 17% at 12 h and 14% at 22 h; P = 0.825). Cleavage and blastocyst rates were higher (P &lt; 0.0001) in the non-vitrified (control) group than in vitrified groups (i.e. 73 vs 15% and 22 vs 0.3%, respectively). In conclusion, the maturation kinetics validated our in vitro culture system and vitrification adversely affected the ability of bovine oocytes to undergo in vitro maturation to the MII stage, in vitro fertilization and early embryo development. Vitrification of oocytes at GV, MI and MII stages of nuclear maturation did not differ in their subsequent survivability. This study was supported by the Canadian Animal Genetic Resources Program, Agriculture and Agri-Food Canada.

Platelet-derived growth factor involvement in myocardial remodeling following infarction

Cardiac remodeling occurs in the infarcted heart (MI). The underlying regulatory mechanisms are under investigation. Platelet-derived growth factor (PDGF) is a family of growth factors that stimulates cell growth, differentiation and migration. Herein, we sought to determine whether PDGF is involved in cardiac repair/remodeling following MI. The temporal and spatial expressions of PDGF isoforms (A, B, C and D) and PDGF receptor (PDGFR)-α and β as well as cell types expressing PDGF were examined in the infarcted rat heart. Sham-operated rats served as controls. We found that the normal myocardium expressed all PDGF isoforms, and cell types expressing PDGF were primarily interstitial cells. Following MI, PDGF-A and D were significantly increased in the infarcted myocardium during 6 weeks of the observation period and cells expressing PDGF-A and D were primarily endothelial cells, macrophages and myofibroblasts (myoFb). PDGF-B and C expressions were, however, reduced in the infarcted heart. In the noninfarcted myocardium, PDGF-D expression was increased in the late stage of MI and cells expressing PDGF-D were predominantly fibroblasts. Both PDGFR-α and β were significantly increased in the infarcted myocardium in the early and late stages of MI and in the noninfarcted myocardium in the late stage of MI. Enhanced PDGF-A, PDGF-D and PDGFR are coincident with angiogenesis, and inflammatory and fibrogenic responses in the infarcted myocardium, suggesting their regulation on cardiac repair. Elevated PDGF-D in the noninfarcted myocardium suggests its involvement in the development of interstitial fibrosis that appears in the late stage of MI.

Stimulation of AMP-Activated Protein Kinase Promotes Maturation and Suppresses Spontaneous Activation of Mouse Oocytes.

Our lab has previously demonstrated that AMP-activated protein kinase (AMPK) in mouse oocytes promotes germinal vesicle breakdown (GVB), and meiotic progression to MII. Active AMPK was localized to the germinal vesicle prior to GVB, condensed chromosomes after GVB, spindle poles at metaphase I and II, and the spindle midzone during anaphase. This staining pattern of active AMPK was dependent on microtubule spindle integrity. On the other hand, inhibiting AMPK activity during spontaneous maturation induced spontaneous activation of oocytes. In this study, we further investigated the effects of AMPK activation on the maturation and activation of oocytes. We used the genetically predisposed parthenogenetic activation strains, LT/SvEiJ mice and its related hybrid strain, LT/SvEiJ x C57B/6J (LTBL) to test the effect of AMPK. Oocytes were cultured in either control MEM/BSA or medium supplemented with the AMPK activator, AICAR (0.2 mM), for 17h. There was no sign of PB formation in the control LT/SvEiJ group; however, 29.8% formed PBs in the presence of AICAR. The PB rates for both control and AICAR-treated groups in LTBL oocytes were intermediate between LT/SvEiJ and B6SJL strains. When oocytes from LT/SvEiJ mice were cultured for 30h in either control medium or medium containing AICAR, 22% of the control group oocytes were activated as shown by formation of pronuclei and cleavage of oocytes, and AICAR reduced this number to 1.9%. AICAR had a similar effect on LTBL oocytes,reducing activation from 15.7% to 4%. To determine the critical window of AMPK activity required to convey this suppressive effect on oocyte activation, LT/SvEiJ oocytes were first cultured in either MEM or medium containing AICAR for 17h, then transferred to either MEM or AICAR-supplemented medium for another 13h before of activation was assessed. Oocytes had control levels of activation when they were first cultured in MEM and then transferred to AICAR. In contrast, oocytes showed low levels of activation when they were first cultured in the presence of AICAR even if AICAR was absent during the subsequent 13h. Experiments using B6SJL oocytes showed a similar effect. When superovulated B6SJL oocytes were retrieved from oviducts 16, 20 and 24h post-hCG, 0.5 mM but not 0.2 mM AICAR produced a subtle and transient suppression of activation during 6h of culture. These data indicated an early requirement of AMPK for suppressing premature activation. Immunofluorescent staining of LT/SvEiJ oocytes after 17h of in-vitro culture indicated that oocytes stayed arrested at MI stage. Interestingly, we observed abnormal active AMPK localization in those oocytes. Instead of staining at the both spindle poles, the localization was shifted from the poles in some oocytes and some were missing spindle pole localization. This suggested that the improper functioning of AMPK might also contribute to the defect of LT/SvEiJ oocytes. (poster)

In Vitro Developmental Potential of Nuclear Transfer Embryos Cloned with Enucleation Methods using Pre-denuded Bovine Oocytes

Enucleation of a recipient oocyte is an important essential process in the procedure of somatic cell nuclear transfer (SCNT). The present study investigated a method for the improvement of enucleation efficiency. Oocytes were denuded of cumulus cells before the completion of nuclear maturation (pre-denuded) after 12 h of culture at MI stage and subsequently cultured for additional 6 h until the completion of nuclear maturation and extrusion of the first polar body (PB1). The extrusion rate of PB1 was not significantly different in the pre-denuded oocyte group, compared with control oocyte group matured for 18 h. However, the number of oocytes showing the metaphase II (MII) located just underneath the PB1 was significantly higher (p<0.05) in the pre-denuded oocyte group than those in control oocyte group. To test the effect of pre-denuding on the enucleation rate and developmental potential of embryos to blastocyst stage, subsequent somatic cell nuclear transfer comparisons were made with three different methods of enucleation at MII stage using vital dyes (demicoline and Hoescht) or the PB1 (blind enucleation) to localize the chromosome plate. Enucleation rate of the oocytes with demicoline, Hoechst and pre-denuding enucleation groups were significantly higher (p<0.05) than those of blind enucleation groups. However, cleavage rate to two-cell stage and, developmental rate to blastocyst and hatched blastocyst stage, the mean numbers of total and ICM cells in the SCNT embryos with Hoechst enucleation groups were significantly decreased (p<0.05), compared to those of blind, demicoline and pre-denuding enucleation groups. Moreover, the level of telomerase activity was also significantly (p<0.05) decreased in SCNT blastocysts of Hoechst enucleation group, compared to those of blind, demicoline and pre-denuding enucleation groups. Taken together, pre-denuding enucleation group using pre-denuded oocytes was a useful and simple enucleation method for bovine SCNT embryos.

Effects of Hormonal Supplementation on Nuclear Maturation and Cortical Granules Distribution of Canine Oocytes During Various Reproductive Stages

The aim of this study was to evaluate the effects of hCG, progesterone and oestradiol supplementation on nuclear and cytoplasmic maturation of canine oocytes cultured for 24, 48, 72 and 96 h. Oocytes obtained from 18 healthy bitches were divided into three groups according to their reproductive status (follicular, luteal and anoestrus stages) and cultured in TCM 199 + 25 UI/ml of hCG + 1 μg/ml of progesterone + 1 μg/ml of 17-β oestradiol or without hormonal supplementation (control) for different periods. Then, they were stained with FITC-LCA-Hoescht for chromatin configuration and cortical granules distribution and evaluated under an epifluorescence microscope. Culture time and the influence of different stages of the oestrous cycle were also evaluated. The present study demonstrated that there was no significant difference among the reproductive stages. With regards to culture medium, only oocytes from the supplemented medium were able to complete meiosis; however, significant difference was only noticed in the percentage of MI stage oocytes (p < 0.05) in the follicular and luteal group at 72 h of culture. Most oocytes in germinal vesicle, germinal vesicle breakdown and metaphase I stage had cortical granules distributed throughout the cytoplasm (immature pattern), irrespective of the culture period (p < 0.05). Cortical granules distributed immediately beneath the plasma membrane (mature) was only observed in metaphase II stage oocytes, but not all of them presented matured cytoplasm. Our results reveal that cortical granules distribution in canine oocytes matured in vitro did not progressed in correspondence with nuclear stage changes and are in accordance with those from other species.

Defective deacetylation of histone 4 K12 in human oocytes is associated with advanced maternal age and chromosome misalignment

Chromosome segregation errors during human oocyte meiosis are associated with low fertility in humans and the incidence of these errors increases with advancing maternal age. Studies of mitosis and meiosis suggest that defective remodeling of chromatin plays a causative role in aneuploidy. We analyzed the histone deacetylation pattern during the final stages of human oocyte maturation to investigate whether defective epigenetic regulation of chromatin remodeling in human oocytes is related to maternal age and leads to segregation errors. Human surplus oocytes of different meiotic maturation stages [germinal vesicle (GV), metaphase (M)I and MII] were collected from standard IVF/ICSI treatments. Oocytes were analyzed for acetylation of different lysines of histone 4 (H4K5, H4K8, H4K12 and H4K16) and for α-tubulin. Human GV oocytes had an intense staining of the chromatin for all four histone 4 lysine acetylations. MI and MII stage oocytes showed either normal deacetylation or various amounts of defective histone deacetylation. Residual H4K12 acetylation was more frequently found in oocytes obtained from older women, with a significant correlation between defective deacetylation and maternal age (r = 0.185, P = 0.007). Eighty-eight percent of the oocytes with residual acetylation had misaligned chromosomes, whereas only 33% of the oocytes that showed correct deacetylated chromatin had misaligned chromosomes (P < 0.001). We conclude that defective deacetylation during human female meiosis increases with maternal age and is correlated with misaligned chromosomes. As chromosome misalignment predisposes to segregation errors, our data imply that defective regulation of histone deacetylation could be an important factor in age-related aneuploidy.

Perturbation of Spc25 expression affects meiotic spindle organization, chromosome alignment and spindle assembly checkpoint in mouse oocytes.

Spc25 is a component of the Ndc80 complex which consists of Ndc80, Nuf2, Spc24, and Spc25. Previous work has shown that Spc25 is involved in regulation of kinetochore microtubule attachment and the spindle assembly checkpoint in mitosis. The roles of Spc25 in meiosis remain unknown. Here, we report its expression, localization and functions in mouse oocyte meiosis. The Spc25 mRNA level gradually increased from the GV to MI stage, but decreased by MII during mouse oocyte meiotic maturation. Immunofluorescent staining showed that Spc25 was restricted to the germinal vesicle, and associated with chromosomes during all stages after GVBD. Overexpression of Spc25 by mRNA injection resulted in oocyte meiotic arrest, chromosome misalignment and spindle disruption. Conversely, Spc25 RNAi by siRNA injection resulted in precocious polar body extrusion and caused severe chromosome misalignment and aberrant spindle formation. Our data suggest that Spc25 is required for chromosome alignment, spindle formation, and proper spindle checkpoint signaling during meiosis.