A combination of EGF and IGF-I accelerates the progression of meiosis in bovine follicular oocytes in vitro and fetal calf serum neutralizes the acceleration effect

Effect of IGFBP-4 during In Vitro Maturation on Developmental Competence of Bovine Cumulus Oocyte Complexes

Insulin-like growth factors (IGFs) are essential for oocyte maturation. Their bioavailability is regulated by their respective binding proteins (IGFBPs) and proteases. IGFBP-4 blocks the biological effects of IGFs. High IGFBP-4 expression has been associated with follicle atresia. We hypothesized that IGFBP-4 affects oocyte developmental competence during maturation. Therefore, the aim of this study was to examine the effect of IGFBP-4 on the developmental rate of bovine cumulus-oocyte complexes (COCs) during in vitro embryo production. Abattoir-derived COCs were matured with rbIGFBP-4 (2000, 540, and 54 ng/mL) compared to a control. Cumulus expansion, oocyte maturation, cleavage, blastocyst, and hatching rates were evaluated. Furthermore, blastocyst gene expression of SOCS2, STAT3, SLC2A1, SLCA3, BAX, and POU5F1 transcripts were quantified using RT-qPCR. No statistical differences were detected among the groups for cumulus expansion, maturation, cleavage, blastocyst rates, or all gene transcripts analyzed. However, at day 8 and 9, the number of total hatching and successfully hatched blastocysts was lower in 2000 ng/mL rbIGFBP-4 compared to the control (day 8: total hatching: 17.1 ± 0.21 vs. 31.2 ± 0.11%, p = 0.02 and hatched blastocyst 6.7 ± 0.31 vs. 21.5 ± 0.14%, p = 0.004; day 9 total hatching 36.4 ± 0.18 vs. 57.7 ± 0.10%, p = 0.009 and hatched blastocyst 18.2 ± 0.21 vs. 38.1 ± 0.11%, p = 0.004). We concluded that high concentrations of rbIGFBP-4 might negatively affect the subsequent ability of the embryo to hatch and possibly compromise further elongation.

Improvement of oocyte competence and in vitro oocyte maturation with EGF and IGF-I in Guinea pig model

In vitro maturation (IVM) system is an alternative method to superovulation protocols to obtain mature oocytes. Epidermal Growth Factor (EGF) and Insulin-like Growth Factor I (IGF-I) have been widely used in IVM medium in different species. Although the guinea pig is a valuable animal model for reproductive studies, IVM is rarely used. We aimed to establish a suitable in vitro production system using EGF and/or IGF-I during IVM to improve oocyte competence. Firstly, immunolocalization of EGF and IGF-I receptors in the ovary was assessed. An IVM dose-response experiment was performed with cumulus-oocyte complexes (COCs) supplemented with: 1) EGF [0, 10, 50, 100 ng/mL or 10% fetal calf serum (FCS)]; 2) IGF-I [0, 50, 100, 200 ng/mL or 10% FCS]; or 3) the concentrations of EGF and IGF-I which showed the best IVM index in the previous experiments, with or without Fetal Calf Serum (FCS). Cortical granule and mitochondria distribution patterns were determined in in vivo and in vitro-matured oocytes for the first time in this species. Apoptotic rate after IVM and oocyte competence by in vitro embryo development were evaluated. Immunohistochemistry results showed positive immunostaining of EGF and IGF receptors in corpus luteum, oocytes, granulosa and theca cells in follicles in all stages of development. Supplementation of IVM medium with 50 ng/mL EGF or 100 ng/mL IGF-I or their combination with FCS successfully led to oocyte nuclear and cytoplasmic maturation and reduced the apoptotic rate. Both growth factors improved oocyte competence during IVM in this species since early embryos were in vitro developed, showing better results when FCS was used in the IVM medium.

Simple and Efficient Chemically Defined In Vitro Maturation and Embryo Culture System for Bovine Embryos

Supplementation of the culture media for in vitro production (IVP) of bovine embryos with fetal bovine serum (FBS) is associated with inconsistent outcomes. The present study sought to replace FBS and BSA by insulin-like growth factor 1 (IGF1), fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF). In Experiment 1, absence of FBS from maturation medium (MM) did not affect the rate of in vitro maturation, as assessed by the extrusion of the first polar body. However, when gonadotropins and FBS were removed from the MM, the maturation rate was significantly reduced even in the presence of growth factors. Therefore, gonadotropin-supplemented MM medium was established as the base medium for the defined maturation condition. In Experiment 2, the addition of growth factors to gonadotropin-supplemented MM medium supported similar maturation (~90%) compared to the undefined condition (FBS-carrying). In Experiment 3, the addition of growth factors to embryo culture medium showed similar in vitro competence compared to the undefined (FBS) control. In Experiment 4, completely defined conditions (absence of FBS and BSA during in vitro maturation and embryo culture) were tested. A higher cleavage was observed with FGF2 (86%) compared to EGF (77%) and the FBS control (77%), but similar blastocyst rates were observed for FGF2 (24%), EGF (19%) and the FBS control (25%). Embryo quality was similar among groups. Finally, post-thawing survival was higher for FGF2 (94%) compared to the FBS control (77%). Thus, we report a simple defined IVP system for bovine species that generates developmental outcomes and embryos of similar quality than those produced under conditions containing FBS.

Mesenchymal stem cells-derived exosomes as a promising new approach for the treatment of infertility caused by polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a multifactorial metabolic and most common endocrine disorder that its prevalence, depending on different methods of evaluating PCOS traits, varies from 4% to 21%. Chronic low-grade inflammation and irregular apoptosis of granulosa cells play a crucial role in the pathogenesis of PCOS infertility. Mesenchymal stem cells (MSCs)-derived exosomes and extracellular vesicles (EVs) are lipid bilayer complexes that act as a means of intercellular transferring of proteins, lipids, DNA and different types of RNAs. It seems that this nanoparticles have therapeutic effects on the PCOS ovary such as regulating immunity response, anti-inflammatory (local and systemic) and suppress of granulosa cells (GCs) apoptosis. Although there are few studies demonstrating the effects of exosomes on PCOS and their exact mechanisms is still unknown, in the present study we reviewed the available studies of the functions of MSC-derived exosome, EVs and secretome on apoptosis of granulosa cells and inflammation in the ovary. Therefore, the novel cell-free therapeutic approaches for PCOS were suggested in this study.

Oral propylene glycol modifies follicular fluid and gene expression profiles in cumulus-oocyte complexes and embryos in feed-restricted heifers

Dietary supplementation with propylene glycol (PG) increases in vitro production of high-quality embryos in feed-restricted heifers. The aim of the present study was to evaluate the effects of PG in feed-restricted heifers on follicular fluid insulin and insulin-like growth factor (IGF) 1 concentrations, expression of IGF system genes in oocytes and cumulus cells and the expression of selected genes in blastocysts. Feed-restricted (R) heifers were drenched with water or PG during induced oestrous cycles (400mL of PG or water/drench, daily drenching at 1600 hours for the first 9 days of the oestrous cycle). Ovum pick-up (OPU) was performed after superovulation to produce in vitro embryos and without superovulation to recover oocytes, cumulus cells and follicular fluid. OPU was also performed in a control group (not feed restricted and no drenching). Follicular fluid IGF1 concentrations were reduced by R, and PG restored IGF1 concentrations to those seen in the control group. In cumulus cells, expression of IGF1, IGF1 receptor (IGF1R) and IGF binding protein 4 (IGFBP4) was decreased in the R group, and fully (IGF1 and IGF1R) or partially (IGFBP4) restored to control levels by PG. Blastocyst perilipin 2 (PLIN2; also known as adipophilin), Bcl-2-associated X protein (BAX), SCL2A1 (facilitated glucose/fructose transporter GLUT1), aquaporin 3 (AQP3), DNA (cytosine-5)-methyltransferase 3A (DNMT3A) and heat shock 70-kDa protein 9 (HSPA9B) expression were decreased in R heifers; PG restored the expression of the last four genes to control levels. In conclusion, these results suggest that, during follicular growth, PG exerts epigenetic regulatory effects on gene expression in blastocyst stage embryos.

The effects of platelet lysate on maturation, fertilization and embryo development of NMRI mouse oocytes at germinal vesicle stage

Purpose

Improving in vitro maturation could increase the rate of pregnancy from oocytes matured in vitro. Consequently, patients will be prevented from using gonadotropin with its related side effects. In this study, the maturation medium was enriched by platelet lysate (PL), then maturation and subsequent developments were monitored.

Methods

Oocytes at germinal vesicle stage with cumulus cells (cumulus-oocyte complex) and without cumulus cells (denuded oocytes) were obtained from mature female mice. The maturation medium was enriched by 5 and 10 % PL and 5 % PL + 5 % fetal bovine serum (FBS) as experimental groups; the control groups' media consisted of 5 and 10 % FBS. After 18 h, the matured oocytes were collected and, after fertilization, subsequent development was monitored.

Results

The rates of maturation, fertilization and 2-cell embryo development for the denuded oocyte groups in experimental media 5 % PL and 5 % PL + 5 % FBS were significantly higher than those of the control groups (P < 0.05), while the results for the cumulus-oocyte complex groups were similar between the experimental groups and control groups.

Conclusions

The results of this study indicated that platelet lysate could improve the maturation rate in the absence of granulosa cells compared to media with FBS. This extract also had positive effects on fertilization and embryo development.

Epidermal growth factor-mediated mitogen-activated protein kinase3/1 pathway is conducive to in vitro maturation of sheep oocytes

Epidermal growth factor (EGF) has been shown to facilitate the in vitro maturation of sheep oocytes, and enhance embryo’s capability for further development. However, such kind of molecular mechanism has not yet been elucidated. In the present study, we investigated the effect of EGF-mediated mitogen-activated protein kinases 3 and 1 (MAPK3/1) pathway on in vitro maturation of sheep oocytes. U0126, a specific inhibitor of MEK (MAPK kinase), was added into the maturation culture medium to block the EGF-mediated MAPK3/1 pathway with different doses. Then, the nuclear maturation of sheep oocytes was examined. Additionally, the effect of EGF-mediated MAPK3/1 on cytoplasmic maturation was examined though in vitro fertilization and embryonic development. The rate of germinal vesicle breakdown (GVBD) after 6 h of culture with 10⁻⁴ mol/l of U0126 (50.4%) was significantly decreased compared with control (67.2%, p < 0.05), and the first polation body (PB1) extrusion rate after 22 h of culture in drug treatment was also significantly inhibited compared with control (28.6% vs. 48.4%, p < 0.05). However, 10⁻⁶ mol/l U0126 had slight effect on oocyte nuclear maturation. The normal distribution rate of α-tubulin in the oocytes after 22 h of in vitro maturation was significantly decreased in the 10⁻⁴ mol/l U0126 group (54%) compared with control (68%, p < 0.05). After in vitro fertilization, the cleavage rate in drug treatments (56.8% in 10⁻⁶ mol/l U0126 group and 42.6% in 10⁻⁴ mol/l U0126 group) was significantly decreased compared with control (72.3%, p < 0.01). The blastocyst rate in 10⁻⁴ mol/l U0126 group (17.6%) was also significantly decreased compared with control (29.9%, p < 0.05). Collectively, these results suggest that EGF-mediated MAPK3/1 pathway is conducive to in vitro maturation of sheep oocytes.

Carrying-over effects of GVBD blocking on post-blocking meiotic progression of oocytes: species difference and the signaling pathway leading to MPF activation

Efforts to improve the quality of in vitro matured oocytes by blocking germinal vesicle breakdown (GVBD) and allowing more time for ooplasmic maturation have achieved little due to a lack of knowledge on the molecular events during GVBD blocking. Such knowledge is also important for studies aimed at regulating gene expression in maturing oocytes prior to GVBD. We studied species difference and signaling pathways leading to the carrying-over effect of GVBD blocking on post-blocking meiotic progression (PBMP). Overall, GVBD-blocking with roscovitine decelerated PBMP of mouse oocytes but accelerated that of pig oocytes. During blocking culture, whereas cyclin B of pig oocytes increased continuously, that of mouse oocytes declined first and then increased slowly. In both species, (a) whereas active CDC2A showed a dynamics similar to cyclin B, inactive CDC2A decreased continuously; (b) when oocytes were blocked in blocking medium containing cycloheximide, PBMP was decelerated significantly while cyclin B and active CDC2A decreasing to the lowest level; (c) whereas sodium vanadate in blocking medium reduced PBMP, epidermal growth factor (EGF) in blocking medium accelerated PBMP significantly with no effect on cyclin B levels. In conclusion, the EGF signaling cascade accelerated PBMP by promoting the pre-MPF (M-phase-promoting factor) to MPF conversion during GVBD blocking with roscovitine. The significant difference in PBMP observed between mouse and pig oocytes was caused by species difference in cyclin B dynamics during blocking culture as no species difference was observed in either pre-MPF to MPF conversion or the EGF signaling activity.

In vitro maturation of ovine oocytes using different maturation media: effect of human menopausal serum

OBJECTIVE

To compare the effect of human menopausal serum with estrous sheep serum, estrous goat serum, ovine follicular fluid and bovine follicular fluid on in vitro maturation, in vitro fertilization and embryo development of sheep oocytes METHOD (S): Oocytes were treated in culture with different sera and follicular fluids supplemented media to examine effects on embryo development.

RESULTS

Basic culture medium supplemented with human menopausal serum, estrous sheep serum and estrous goat serum supported better rates of in vitro maturation, in vitro fertilization and embryo development. Ovine follicular fluid and bovine follicular fluid supplementations supported similar rates of In vitro maturation, In vitro fertilization and embryo development which were lower than those supported by human menopausal serum, estrous sheep serum, estrous goat serum and control medium.

CONCLUSION

Human menopausal serum, estrous sheep serum, and estrous goat serum resulted in higher maturation, fertilization and embryo development than ovine follicular fluid, bovine follicular fluid and control media.

Effect of bovine cumulus-oocyte complexes-conditioned medium on in-vitro maturation of canine oocytes

Purpose

To investigate the ability of medium conditioned with bovine cumulus-oocyte complexes (COCs) to support nuclear maturation of canine oocytes recovered from domestic dog ovaries.

Methods

Cumulus-oocyte complexes were obtained from ovaries of domestic bitches (8 months old to 7 years old), and in-vitro maturation was evaluated in TCM-199 supplemented with different concentrations (0, 20, 30 or 50%) of bovine COCs-conditioned medium (BCM). The canine COCs were cultured for 72 or 96 h at 38.5°C in 5% CO₂, 5% O₂ and 90% N₂. The bovine COCs-conditioned medium was obtained from culture of bovine COCs with TCM-199 supplemented with 5% FCS for 22 h at 38.5°C in 2% CO₂, 98% air.

Results

The proportion of germinal vesicle breakdown (GVBD) after 72 h was significantly higher (P < 0.05) in medium supplemented with 30% BCM (20.7%) compared with the control group (13.4%). The rates of GVBD-MII stage were significantly higher (P < 0.05) when oocytes were matured with BCM at concentration of 30% (41.5%) compared with control (26.6%) after 72 h in-vitro culture. After 96 h in-vitro culture, the oocytes matured in medium supplemented with 30% BCM (5.5%) showed a significant increase (P < 0.05) in the proportion of MII compared with control (0.7%). However, increasing the cultivation time from 72 to 96 h resulted in an increase in oocyte degeneration rate.

Conclusions

The results suggested that bovine COCs-conditioned medium supplementation significantly increased nuclear maturation of canine oocytes.

Effect of conditioned medium of mesenchymal stem cells on the in vitro maturation and subsequent development of mouse oocyte

Mesenchymal stem cells (MSCs) secrete a variety of cytokines and growth factors in addition to self-renewal and multiple forms of differentiation. Some of these secreted bioactive factors could improve meiotic maturation in vitro and subsequent embryo developmental potential. The aim of the present study was to determine whether in vitro maturation (IVM) of mouse oocyte with or without cumulus cells could be improved by contact with conditioned medium (CM) of MSCs as well as the efficiency of CM to support follicular growth and oocyte maturation in the ovarian organ of mice cultured on soft agar. The developmental potential of matured oocyte was assessed by blastocyst formation after in vitro fertilization (IVF). Germinal vesicle stage oocytes with or without cumulus cells were subjected to IVM in either CM, Dulbecco's modified Eagle's medium (DMEM), alpha-minimum essential medium (alpha-MEM) or human tubal fluid (HTF). Approximately 120 oocytes were studied for each medium. CM produced a higher maturation rate (91.2%) than DMEM (54.7%), alpha-MEM (63.5%) and HTF (27.1%). Moreover, CM improved embryo development to blastocyst stage significantly more than DMEM and HTF (85 vs 7% and 41.7%, respectively) but there was no significant difference compared with alpha-MEM (85 vs 80.3%). The behavior of cortical granules of IVM oocytes cultured in CM revealed cytoplasmic maturation. Moreover, CM also supported preantral follicles growth well in organotypic culture on soft agar resulting in the maturation of 60% of them to developmentally competent oocytes. The production of estrogen progressively increased approximately 1-fold every other day during organ culture, while a dramatic 10-fold increase in progesterone was observed 17 h after human chorionic gonadotropin stimulus at the end of culture. Thus, CM is an effective medium for preantral follicle growth, oocyte maturation, and sequential embryo development.

Effects of insulin-like growth factor-I, epidermal growth factor and cysteamine on the in vitro maturation and development of oocytes collected from 6- to 8-week-old Merino lambs

To improve the viability of embryos produced in vitro from lamb oocytes, maturation medium was supplemented with insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF), cysteamine, and combinations thereof. Experiment 1 examined the effects of IGF-I supplementation and duration of oocyte maturation on nuclear maturation and embryo development while Experiments 2 and 3 examined the effects of cysteamine and EGF supplementation respectively on embryo development. In Experiment 4, embryo development was examined after maturation with various combinations of supplements. IGF-I supplementation increased cleavage rate (P < 0.05) but its effect on the rate of blastocyst production from original oocytes was variable. Supplementation with IGF-I increased (P < 0.01) the proportion of oocytes at Metaphase II (MII) after 18 h of maturation but not at later times. EGF either alone or combined with IGF-I significantly (P < 0.05) increased cleavage rates compared with other treatment groups but EGF consistently failed to improve blastocyst production rates. Cysteamine improved hatching rates but only when supplemented alone. Maturation of lamb oocytes for 22 h in medium supplemented with 100 ng mL(-1) IGF-I and 100 microm cysteamine resulted in the production of 16.0 lambs per donor lamb after embryos were transferred to recipient ewes. It is concluded that EGF and, to a lesser extent, IGF-I, whilst beneficial to initial cleavage, can adversely influence subsequent embryo development. Improvements in embryo viability may more likely be obtained by addressing issues that influence fetal oocyte quality than by modifying in vitro methodology.

Developmental potential of bovine oocytes cultured in different maturation and culture conditions

Diverse groups of chemicals in culture media are needed for successful bovine oocyte maturation and embryo development during which dramatic cytoplasmic and nuclear reprogramming events take place. In vitro embryo production (IVP) procedures frequently include supplements such as serum and/or co-culture with various types of somatic cells. However, the presence of undefined serum in culture media introduces a variation from batch to batch, increases viral or prion contamination risk, and leads to problems during fetal development. The aim of the present study was to investigate the possibility of using chemically defined-synthetic serum substitute (SSS) in place of fetal calf serum (FCS) during maturation and long-term culture to stimulate in vitro maturation (IVM), fertilization (IVF) and subsequent embryo development. In Experiment I, the effect of the protein source on in vitro maturation was tested by maturing oocytes in culture media supplemented with 10% FCS (Control Group), 10% SSS (Group I) and 10% SSS+10 ng/ml epidermal growth factor (EGF) (Group II). In Experiment II, effects of SSS on both oocyte maturation and embryo development during in vitro culture (IVC) were tested by maturing oocytes in media supplemented with 10% FCS (FCS Group) or 10% SSS+10 ng/ml EGF (SSS Group), followed by IVF and IVC in SOF media supplemented with 10% FCS and 10% SSS on day 4 for FCS and SSS Groups, respectively. Even though rates for cleavage and development to blastocyst stage were not different, blastocyst cell numbers were higher in Group II containing SSS and EGF. The SSS supplementation group had higher apoptotic nuclei as compared to the FCS Group in Experiment II. Transcripts for heat shock protein 70 (Hsp70), interferon tau (IF-tau), DNA methyltransferase 3a (Dnmt3a), desmosomal glycoprotein desmocollin III (DcIII) and insulin-like growth factor II receptor (Igf-2r) were altered in different culture conditions in Experiment I. However, only glucose transporter-1 (Glut-1) mRNA was different in the SSS and FCS Groups in the second experiment. In summary, SSS and EGF in maturation medium and replacement of FCS with SSS alone in culture medium on day 4 of IVC support oocyte maturation and embryo development in vitro. However, significance of culture condition induced changes on the genome-wide abundance of messenger ribonucleic acid and the significance of the apoptotic nuclei during fetal development still remain to be determined.

Influence of epidermal growth factor and insulin-like growth factor 1 on nuclear maturation and fertilization of buffalo cumulus oocyte complexes in serum free media and their subsequent development in vitro

The in vitro maturation, fertilization and development of Indian water buffalo (Bubalus sp.) cumulus oocyte complexes (COCs) to blastocysts were studied during culture, either in serum free tissue culture medium 199 (TCM 199) or Waymouth MB (WM). Based on different supplements added to these media, the experimental groups included: (a) no supplement (control); (b) hormones (FSH, LH and oestradiol) (c) Epidermal growth factor (EGF); (d) IGF-1; and (e) EGF + IGF-1. Experiments were conducted to note three end points: (1) nuclear maturation 24 h after culture (eight replicates); (2) fertilization 24 h after insemination (10 replicates); (3) development to blastocysts (nine replicates). The oocytes were cultured in groups of up to five per drop. Using a two-way (5 x 2) factorial model with interactions, the results were compared using generalized linear models with binomial errors and the logit link function. In experiment 1, the proportion of oocytes reaching metaphase II was higher for all the supplement treatments than the control treatment (t = 3.68, p < 0.0001). The proportion of oocytes reaching metaphase II was 74.7, 63.2, 64.7 and 81% with hormone (chi2 = 17.23, p < 0.0001), EGF (chi2 = 7.07, p = 0.007), IGF-1 (chi2 = 19.21, p = 0.002) and EGF + IGF-1 (chi2 = 33.04, p < 0.0001) supplementation, respectively, compared to 46.6% in the control (no supplement) group. Media did not have an effect on outcome. In experiment 2, the proportion of oocytes fertilized was significantly higher with hormones (31.0%, chi2 = 12.5, p = 0.0004), IGF-1 (35.7%, chi2 = 20.53, p < 0.0001), and the EGF + IGF-1 combination (49.7%, chi2 = 51.35, p < 0.0001) compared to control (16.2%). No significant effect of media was seen. In experiment 3, the proportion of oocytes that cleaved at 48 h after culturing was significantly higher for all supplement treatments compared to control. IGF-1 supplementation was the only treatment that did not produce a significantly higher rate of progression to blastocysts compared to the control. Once again, media had no effect on outcome. It was concluded that maturation, fertilization and development of buffalo oocytes were enhanced by all supplements tested. Enhancement was maximal with the combination of EGF+IGF-1. In contrast, no significant differences were found between the two types of media used.

Expression of epidermal growth factor receptor in the goat cumulus-oocyte complex

It has been previously reported that epidermal growth factor (EGF) influences meiotic maturation and development competence of oocytes in various mammalian species. The present study was undertaken to analyze the expression of the gene encoding the EGF-receptor (EGF-R) in the goat cumulus-oocyte complex during meiotic competence acquisition. Expression of EGF-R mRNA was evaluated by PCR on reverse transcribed mRNA from follicular cells and oocytes, using EGF-R specific primers designed from human cDNA. The presence of the EGF-R transcript was evidenced in follicular cells as well as in meiotically competent and incompetent oocytes. Western blot analysis performed with specific anti EGF-R antibody revealed in meiotically competent and incompetent oocytes and in follicular cells a 170 kD polypeptide corresponding to the goat EGF-R protein. In oocytes the amount of EGF-R increased with meiotic competence acquisition. EGF-R distribution was examined by indirect immunofluorescence on frozen sections of cumulus-oocyte complexes (COCs). EGF-R immunoreactivity was observed in cumulus cells and in oocytes. Staining appeared to be confined to the periphery of the cells for both oocytes and cumulus cells. In this study, we identified the main component required for signaling via EGF-R in the goat oocyte and in follicular cells. These results suggest a possible involvement of EGF in the regulation of follicular growth and oocyte maturation in goat.

IGF-1/IGFBP-1 increases blastocyst formation and total blastocyst cell number in mouse embryo culture and facilitates the establishment of a stem-cell line

Background

Apoptosis occurs frequently for blastocysts cultured in vitro, where conditions are suboptimal to those found in the natural environment. Insulin-like growth factor-1 (IGF-1) plays an important role in preventing apoptosis in the early development of the embryo, as well as in the progressive regulation of organ development. We hypothesize that IGF-1 and its dephosphorylated binding protein (IGFBP-1) may be able to improve embryo culture with an associated reduced cell death, and that the resultant increase in the total cell number of the embryo could increase the chances of establishing an embryonic stem-cell line.

Results

In vivo fertilized zygotes were cultured in medium containing supplementary IGF-1, or IGFBP-1/IGF-1. The stages of the resultant embryos were evaluated at noon on day five post-hCG injection. The extent of apoptosis and necrosis was evaluated using Annexin V and propidium iodine staining under fluorescent microscopy. The establishment of embryonic stem-cell lines was performed using the hatching blastocysts that were cultured in the presence of IGF-1 or IGFBP-1/IGF-1. The results show that the rate of blastocyst formation in a tissue-culture system in the presence of IGF-1 was 88.7% and IGFBP-1/IGF-1 it was 94.6%, respectively, and that it was significantly greater than the figure for the control group (81.9%). IGFBP-1/IGF-1 also resulted in a higher hatching rate than was the case for the control group (68.8% vs. 48.6% respectively). IGF-1 also increased the number of Annexin V-free and propidium iodine-free blastocysts in culture (86.8% vs. 75.9% respectively). Total cell number of blastocyst in culture was increased by 18.9% for those examples cultured with dephosphorylated IGFBP-1/IGF-1. For subsequent stem-cell culture, the chances of the successful establishment of a stem-cell line was increased for the IGF-1 and IGFBP-1/IGF-1 groups (IGF-1 vs. IGFBP-1/IGF-1 vs. control: 45.8% vs. 59.6% vs. 27.3% respectively).

Conclusion

IGF-1 or dephosphorylated IGFBP-1/IGF-1 supplement does result in an anti-apoptotic effect for early embryo development in culture, with a subsequent increased total cell number resulting from cell culture. The effect is beneficial for the later establishment of a stem-cell line.

Preovulatory rise of NGF in ovine follicular fluid: possible involvement in the control of oocyte maturation

Since nerve growth factor (NGF) is produced in vitro by granulosa cells after gonadotropin stimulation, the present research has been designed to investigate whether this neurotropin is involved in the events triggered by the gonadotropin surge that lead the follicle to ovulate a mature oocyte. To this aim, NGF levels in follicular fluid, collected before or 20 hours after the gonadotropin surge, was measured by ELISA. To evaluate whether NGF may have a non-neurotropic effect on follicle cells, the presence of NGF receptors was investigated by immunohistochemistry and further evaluated by analysing the tyrosine-phosphorylation pattern after NGF stimulation in vitro. The effect of NGF on the degree of cumulus expansion, cumulus-oocyte metabolic coupling, and meiotic maturation was finally studied by using the culture of follicle-enclosed oocyte. The results demonstrate that GnRH causes a dramatic rise of NGF in large follicles. Immunohistochemistry revealed a discrete positivity for trkA receptors localised in cumulus cells. Tyrosine phosphorylation pattern confirms that somatic cells are capable to transduce NGF signal. By contrast, all the oocytes examined were negative for trkA and did not change the phosphorylation pattern after NGF. In vitro NGF (100 ng/ml) induced a marked cumulus expansion and a progressive cumulus-oocyte uncoupling similar to that produced by gonadotropins. The addition of NGF also caused the resumption of meiosis in more than 70% of the oocytes analysed with an effect that is only slightly less pronounced than that of gonadotropins (80%). The increase in NGF secretion following gonadotropin surge suggests that this neurotropin may be involved in the control of oocyte maturation.

Quantification and distribution of equine oocyte cortical granules during meiotic maturation and after activation

In vitro fertilization (IVF) is being routinely used in humans and several domestic species, however, limited success has been achieved in the horse. Although immature equine oocytes are capable of completing meiosis in vitro, subsequent fertilization, and embryonic development of those oocytes are questionable. The lack of development of these oocytes could be attributed to an impaired cytoplasmic maturation. In the horse, the study of oocyte cytoplasmic maturation and post-fertilization development has been hindered by the lack of progress in IVF. In mammalian oocytes, migration of cortical granules (CG) has been used as an important criterion to evaluate cytoplasmic maturation. The aim of this study was to describe and quantify the CG distribution of equine oocytes during in vitro meiotic maturation and to assess activation of oocytes with calcium ionophore based upon fluorescein isothiocyanate (FITC)-labeled Lens culinaris agglutinin (LCA) and laser confocal microscopy. The results of this study indicate that CG are distributed throughout the cytoplasm of oocytes at the germinal vesicle (GV) stage (immature). As maturation proceeds, a progressive centripetal migration of CG to the oocyte cortex occurs with the formation of a monolayer adjacent to the plasma membrane starting by the end of a 30 hr incubation period and increasing significantly after 36 hr. After activation, significant reduction in the number of CG was observed (P < 0.001) suggesting that oocytes cultured under the present conditions possess the ability to release CG in response to the elevation of intracellular free calcium.

Bovine somatotropin increases embryonic development in superovulated cows and improves post-transfer pregnancy rates when given to lactating recipient cows

Previous studies indicated that the use of bovine somatotropin (bST) in concurrence with a timed artificial insemination (TAI) protocol increased pregnancy rates. However, the mechanisms for such a bST effect on fertility were not clear. Objectives of this study were to determine the effects of bST on fertilization and early embryonic development after cows received a superovulation treatment, test whether embryos recovered from bST-treated cows were more likely to survive after transfer to recipients, and evaluate whether treatment of recipient cows with bST affects pregnancy rates. Lactating (n = 8) and nonlactating (n = 4) Holstein donor cows were superovulated, inseminated at detected estrus and assigned to a nontreated control group or to a treatment group receiving a single injection of bST (500 mg, sc) at insemination. Embryos were nonsurgically flushed 7 days after AI and frozen in ethylene glycol for direct transfer. Embryos derived from bST-treated (bST-embryos) or control (control-embryos) donors were transferred to lactating Holstein recipient cows that received either bST treatment 1 day after estrus (500 mg, sc; bST-recipients) or were untreated controls (control-recipients). Thus, there were four treatment groups: control-embryos/control-recipients (n = 43), bST-embryos/control-recipients (n = 41), control-embryos/bST-recipients (n = 37), and bST-embryos/bST-recipients (n = 60). Pregnancy was determined by palpation per rectum 33-43 days after embryo transfer. Unfertilized ova per flush was less for bST than for control (1.0 +/- 0.9 < 3.7 +/- 0.9; P < 0.04). Percentage of transferable embryos was greater for bST than for control (77.2% > 56.4%; P < 0.01). Number of blastocysts per flush was greater for bST than for control (2.4 +/- 0.7 > 0.4 +/- 0.7; P < 0.04). Pregnancy rates following embryo transfer were 25.6% for control-recipient/control-embryo, 43.2% for bST-recipient/control-embryo, 56.1% for control-recipient/bST-embryo, and 43.3% for bST-recipient/bST-embryo. Transfer of bST-embryos increased pregnancy rates compared with transfer of control-embryos (P < 0.04). An interaction between embryo and recipient treatments (P < 0.05) indicated that treatment of recipient cows with bST increased pregnancy rates as compared to control-recipients that received a control-embryo. However, there was no additive effect when bST-recipients received a bST-embryo. Administration of bST at AI decreased the number of unfertilized ova, increased the percentage of transferable embryos, and stimulated embryonic development to the blastocyst stage. Moreover, bST affected both early embryonic development and recipient components to increase pregnancy rates following embryo transfer.