In vitro culture of mouse embryos reduces differential gene expression between inner cell mass and trophectoderm

Differences in gene expression and imprinting have been reported, comparing in vivo versus in vitro generated preimplantation embryos. Furthermore, mouse studies have shown that placenta development is altered following in vitro culture. However, the molecular mechanisms underlying these findings are unknown. We therefore isolated trophectoderm (TE) and inner cell mass (ICM) cells from in vivo and in vitro fertilization (IVF) embryos and evaluated their transcriptome using microarrays. We found that the transcriptomes of in vitro produced ICM and TE cells showed remarkably few differences compared to ICM and TE cells of in vivo generated embryos. In vitro fertilization embryos showed a reduced number of TE cells compared to in vivo embryos. In addition, TE of IVF embryos showed significant downregulation of solute transporter genes and of genes involved in placenta formation (Eomesodermin, Socs3) or implantation (Hbegf). In summary, IVF and embryo culture significantly affects the transcriptome of ICM and TE cells.

Effect of ICSI on gene expression and development of mouse preimplantation embryos

BACKGROUND

In vitro culture (IVC) and IVF of preimplantation mouse embryos are associated with changes in gene expression. It is however not known whether ICSI has additional effects on the transcriptome of mouse blastocysts.

METHODS

We compared gene expression and development of mouse blastocysts produced by ICSI and cultured in Whitten's medium (ICSI(WM)) or KSOM medium with amino acids (ICSI(KSOMaa)) with control blastocysts flushed out of the uterus on post coital Day 3.5 (in vivo). In addition, we compared gene expression in embryos generated by IVF or ICSI using WM. Global pattern of gene expression was assessed using the Affymetrix 430 2.0 chip.

RESULTS

Blastocysts from ICSI fertilization have a reduction in the number of trophoblastic and inner cell mass cells compared with embryos generated in vivo. Approximately 1000 genes are differentially expressed between ICSI blastocyst and in vivo blastocysts; proliferation, apoptosis and morphogenetic pathways are the most common pathways altered after IVC. Unexpectedly, expression of only 41 genes was significantly different between embryo cultured in suboptimal conditions (WM) or optimal conditions (KSOM(aa)).

CONCLUSIONS

Our results suggest that fertilization by ICSI may play a more important role in shaping the transcriptome of the developing mouse embryo than the culture media used.

Pregnancy rates and peripheral progesterone levels following Ovsynch or CIDR ovulation synchronization/timed artificial insemination protocols in postpartum dairy cows

Peripheral progesterone (P4) concentrations as well as pregnancy rates (PR) between cows treated with Ovsynch or CIDR ovulation synchronization/TAI protocols were compared. Two hundred and twenty-seven postpartum lactating Holstein cows were randomly assigned to Ovsynch (n = 111) or CIDR (n = 116) ovulation synchronization/TAI protocols. Pregnancy was diagnosed by ultrasonography at day 35 after TAI and later confirmed by rectal palpation at day 60 post TAI. Milk samples were taken from the beginning of treatment (day -10) until day 35 after TAI (day 0) for P4 determination. Pregnancy rates for Ovsynch and CIDR groups of cows were 31 and 41%, respectively. The PR of ovulation synchronized cows for Ovsynch and CIDR groups were 49 and 69%, respectively. Progesterone levels during the sampling period were similar (P > 0.05) between Ovsynch and CIDR treated cows. Key words: Pregnancy rate, progesterone, Ovsynch, CIDR, cows

Gonadotropin releasing hormone receptor gene and protein expression and immunohistochemical localization in bovine uterus and oviducts

Recently GnRH, GnRH-R systems has been demonstrated in various extrahypothalamic and extrapituitary reproductive tissues in different mammalian species, where GnRH acts in an autocrine and or paracrine manner and modulates different biological processes. GnRH-R mRNA has also been demonstrated in bovine ovaries (follicle and corpus luteum) and normal and carcinogenic human endometrium/endometrial cells. This is the first study elucidating presence of GnRH-R mRNA and GnRH-R protein in bovine uterus and oviducts in follicular and luteal phases of the estrous cycle and further localizing the receptors to endometrial and oviductal epithelial cells. To our knowledge this is the first report demonstrating GnRH-R mRNA and protein in mammalian oviducts. We used gene-specific primers and monoclonal GnRH-R antibody to test GnRH-R mRNA and GnRH-R protein through RT-PCR and immunobloting. Immunohistochemistry was employed to localize these receptors to endometrial and oviductal epithelial cells. GnRH-R mRNA and receptor protein were expressed at expected molecular weights of 920bp and 60kD, respectively. Densitometry analysis revealed that expression levels for GnRH-R protein in uterus and oviducts were similar to bovine pituitary. The presence of GnRH receptors in bovine uterus and oviducts is intriguing and it would be imperative to examine the functional role of this system in the regulation of reproductive processes.

Paternal influence on apoptosis, and expression of BCL2, BAX, TP53, heat shock protein-70 and interferon tau genes in bovine preimplantation embryo

The bull effects on apoptosis, and BAX, BCL2, TP53, heat shock protein 70 (HSPA1A) and interferon tau (IFNT) gene expression in in vitro produced embryos were investigated. The degree of correlation of this effect with the 60- to 90-d non-return rates was also investigated. Standard in vitro fertilization and embryo culture were performed using frozen semen from six genetically unrelated bulls. Live, apoptotic, and dead cell percentages in blastocysts were determined, after staining with annexin V, propidium iodide, and bisbenzamide. BAX, BCL2, TP53, HSPA1A and IFNT gene expression levels in blastocysts were determined by RT-PCR. The non-return rate data for all experimental bulls were obtained from a local artificial insemination center. Apoptotic, live and dead blastomere percentages, and HSPA1A and IFNT expression levels in blastocysts were different (P < 0.01) among bulls. BAX, BCL2 and TP53 expression levels were not different among bulls. The non-return rate was highly correlated (P < 0.05) with BCL2 (r = -0.93) or the ratio of BAX to BCL2 (r = 0.84) gene expression. None of the other in vitro fertility parameters were correlated with non-return rate. This study concluded that the development, apoptosis, and HSPA1A and IFNT gene expression of in vitro produced embryos are influenced by individual bulls. Key words: Bovine, embryo, fertility, apoptosis, gene expression, interferon

Development of in vitro tests to predict fertility of bulls

The overall objective was to develop an in vitro test to predict fertility of bulls in the field. We investigated the bull effect on in vitro embryo production, zona binding and acrosome reaction, and the correlation of this effect to field fertility meas ured by 60–90 d non-return rate. Frozen semen from three separate ejaculates of eight unrelated young bulls, obtained from an artificial insemination (AI) center, was used. On thawing, ejaculates from each bull were pooled, motile sperm were selected and (a) subjected to immunofluorescent assay at 0 and 4 h of incubation in capacitation medium to assess acrosome status, (b) used in an in vitro fertilization assay system to assess cleavage and blastocyst production rates, and (c) sperm-zona binding assay was carried out to determine the number of sperm bound to the zona pellucida of mature oocytes. Percentage of pre-freeze motile sperm (PrFM) and non-return rate data were obtained from the AI center. PrFM, percentage of acrosome reacted sperm at 0 h (AR1), increase in percentage of acrosome reacted sperm after 4 h (InAR) and sperm-zona binding rates (ZB) differed (P < 0.05) among sperm samples obtained from different young bulls. Significant correlations (P < 0.05) were observed between PrFM and AR1 (r = -0.31), InAR (r = 0.36), and ZB (r = 0.32). AR1 was negatively correlated to ZB (r = -0.27) and cleavage rate (r = -0.20), InAR was positively correlated with ZB (r = 0.31) and cleavage rate (r = 0.26). None of the in vitro tests was correlated with non-return rate. These findings indicate that along with pre-freeze motility, a combination of in vitro tests including the percentage of spontaneously acrosome reacted sperm at thawing, might be useful in predicting bull field fertility. Such a combination of assays, however, has yet to be determined. Key words: Field fertility, acrosome reaction, zona binding, IVF, fertility assay

In vitro assessment of corpus luteum function in cattle following Ovsynch and CIDR ovulation synchronization protocols

Non-lactating beef cows (N = 40) were used to determine in vitro production of progesterone by CLs collected on days 6–8, 13–15 and 19–20, following Ovsynch or CIDR ovulation synchronization protocols. Progesterone released by the CL tissues into the medium was measured after 1 h of incubation (control) and after 6 h of hormone treatments (LH, PGF2α or LH + PGF2α). In vitro progesterone production did not differ (P > 0.05) between Ovsynch and CIDR ovulation synchronization protocols. Pooled data, irrespective of ovulation synchronization treatments, showed interaction (P < 0.05) between hormone treatment and stage of CL. Key words: Corpus luteum, progesterone, cows, ovulation synchronization

GnRH receptor messenger ribonucleic acid expression in bovine ovary

The present study was undertaken to investigate the mRNA expression for gonadotropin-releasing hormone (GnRH) receptor in bovine ovary. Granulosa cells from small (< 4 mM), medium (5–8 mM) and large follicles (> 8 mM) and tissues from corpora lutea (CL) of different stages: Stage I (days 1–4), Stage II (days 5–10), Stage III (days 11–17), and Stage IV (days 18–21, days after ovulation) were harvested from bovine ovaries collected at a local abattoir. The mRNA isolated from representative samples was subjected to reverse transcription-polymerase chain reaction (RT-PCR) using gene sequence specific primers. The resultant PCR amplified gonadotropin-releasing horm one receptor (GnRH-R) cDNA products were identified and confirmed through Southern blot hybridization and nucleotide sequence analysis, respectively. The results showed the presence of GnRH-R mRNA transcripts in both follicles and CL. Key words: Bovine, granulosa cells, corpus luteum, GnRH receptor, mRNA

In vitro embryo production using ovaries removed from culled cows

The objective was to utilize in vitro maturation and fertilization to maximize embryo production from culled dairy cows. Ovaries were removed (via a colopotomy technique) from culled Holstein cows (n = 21) 2 d after standing estrus (T1), 2 d after treatment with 40 mg follicle stimulating hormone (FSH) given at standing estrus (T2), or at an unknown stage of the estrous cycle (T3).Treatment with FSH increased (P < 0.05) oocyte recovery rate (mean ± SEM, 14.6 ± 2.2, 25.4 ± 3.4, and 11.1 ± 2.6 oocytes ovary–1), for groups T1, T2 and T3, respectively, and the number of blastocysts obtained (1.6 ± 0.5, 4.4 ± 0.4 and 1.6 ± 0.6 blastocysts ovary–1). Culled dairy cows of high genetic merit are potential embryo donors, with an average of six to eight transferable embryos obtained from each FSH-treated cow. Key words: FSH treatment, oocyte recovery, IVM, IVF, culled cows