Influence of epidermal growth factor supplementation during in vitro maturation on nuclear status and gene expression of canine oocytes

Liraglutide improves follicle development in polycystic ovary syndrome by inhibiting CXCL10 secretion

BACKGROUND

At present, a number of clinical trials have been carried out on GLP-1 receptor agonist liraglutide in the treatment of polycystic ovary syndrome (PCOS). However, the effect of liraglutide on follicle development and its specific mechanism are still unclear.

METHODS

RNA sequencing was used to explore the molecular characteristics of granulosa cells from patients with PCOS treated with liraglutide. The levels of C-X-C motif chemokine ligand 10 (CXCL10) in follicular fluid were detected by ELISA, the expression levels of ovulation related genes and inflammatory factor genes in follicles and granulosa cells were detected by qPCR and the protein levels of connexin 43 (Cx43), Janus Kinase 2 (JAK2) and phosphorylated JAK2 were detected by Western blot. The mouse ovarian follicles culture system in vitro was used to detect the status of follicle development and ovulation.

RESULTS

In the present study, we found that liraglutide inhibited the secretion of inflammatory factors in PCOS granulosa cells, among which CXCL10 was the most significant. In addition, CXCL10 was significantly higher in granulosa cells and follicular fluid in PCOS patients than in non-PCOS patients. We applied in vitro follicle culture and other techniques to carry out the mechanism exploration which revealed that CXCL10 disrupted the homeostasis of gap junction protein alpha 1 (GJA1) between oocyte and granulosa cells before physiological ovulation, thus inhibiting follicular development and ovulation. Liraglutide inhibited CXCL10 secretion in PCOS granulosa cells by inhibiting the JAK signaling pathway and can improved dehydroepiandrosterone (DHEA)-induced follicle development disorders, which is reversed by CXCL10 supplementation.

CONCLUSIONS

The present study suggests that liraglutide inhibits CXCL10 secretion in granulosa cells through JAK signaling pathway, thereby improving the homeostasis of GJA1 between oocyte and granulosa cells before physiological ovulation and ultimately improving the follicular development and ovulation of PCOS, which provides more supportive evidence for the clinical application of liraglutide in the treatment of ovulatory disorders in PCOS.

TRIAL REGISTRATION

Not applicable.

Supplementation of porcine in vitro maturation medium with FGF2, LIF, and IGF1 enhances cytoplasmic maturation in prepubertal gilts oocytes and improves embryo quality

In porcine in vitro production (IVP) systems, the use of oocytes derived from prepubertal gilts, whilst being commercially attractive, remains challenging due to their poor developmental competence following in vitro maturation (IVM). Follicular fluid contains important growth factors and plays a key role during oocyte maturation; therefore, it is a common supplementation for porcine IVM medium. However, follicular fluid contains many poorly characterized components, is batch variable, and its use raises biosecurity concerns. In an effort to design a defined IVM system, growth factors such as cytokines have been previously tested. These include leukaemia inhibitory factor (LIF), fibroblast growth factor 2 (FGF2), and insulin-like growth factor 1 (IGF1), the combination of which is termed 'FLI'. Here, using abattoir-derived oocytes in a well established porcine IVP system, we compared follicular fluid and FLI supplementation during both IVM and embryo culture to test the hypothesis that FLI can substitute for follicular fluid without compromising oocyte nuclear and cytoplasmic maturation. We demonstrate that in oocytes derived from prepubertal gilts, FLI supplementation enhances oocyte meiotic maturation and has a positive effect on the quality and developmental competence of embryos. Moreover, for the first time, we studied the effects of follicular fluid and FLI combined showing no synergistic effects.

Fighting Like Cats and Dogs: Challenges in Domestic Carnivore Oocyte Development and Promises of Innovative Culture Systems

In vitro embryo production in cats and dogs still presents some challenges, and it needs to be optimized to transfer efficient protocols to related wild, endangered species. While the chemical composition of culture media has been the focus of several studies, the importance of culture substrates for oocyte and embryo culture has often been neglected. Traditional in vitro systems, i.e., two-dimensional cultures, do not resemble the physiological environments where cells develop, and they may cause morphological and functional alterations to oocytes and embryos. More modern three-dimensional and microfluidic culture system better mimic the structure and the stimuli found in in vivo conditions, and they could better support the development of oocytes and embryos in vitro, as well as the maintenance of more physiological behaviors. This review describes the different culture systems tested for domestic carnivore reproductive cells along the years, and it summarizes their effects on cultured cells with the purpose of analyzing innovative options to improve in vitro embryo production outcomes.

Effects of serum and follicular fluid on the in vitro maturation of canine oocytes

The effects of gonadotropin, serum and follicular fluid on the in vitro maturation of canine oocytes were examined. Additionally, spindle size and spindle migration in MI-stage oocytes derived by in vivo or in vitro maturation were evaluated for the first time. Mature oocytes collected from beagle dog ovaries were divided into two experiments. In experiment I, oocytes were cultured in basic TCM 199 medium supplemented with different levels of P4, E2 and FSH. In experiment II, oocytes in the estrus or anestrus stage were cultured in basic medium supplemented with 30% or 40% canine serum plus 20% or 10% follicular fluid. Our results showed that in experiment I, more oocytes reached MI-MII (18.57%) after supplementation with 1 IU/ml FSH+ 5 IU/ml P4 + 5 IU/ml E2 than after supplementation with other levels of reagents. However, there were no significant differences among the groups (three different concentration groups and a control group) with respect to the proportions of oocytes that resumed meiosis, completed meiosis or degenerated. In experiment II, the number of oocytes from the estrus stage that reached MI-MII in TCM 199 medium supplemented with 40% canine serum and 10% follicular fluid (46.72%) was significantly higher (p < 0.01) than the number of oocytes from the anestrus stage that reached MI-MII in medium supplemented with 30% canine serum and 20% follicular fluid (21.84%). In addition, the degeneration rate was significantly lower (p < 0.05) in the 40% canine serum/10% follicular fluid group from follicular stage than in the other three groups. The average spindle length of the MI-stage oocytes that matured in vivo was significantly (p < 0.01) longer than that of the MI-stage oocytes that matured in vitro (21.75 vs. 14.39 μm). These results suggest that supplementation of the culture medium with 40% estrus serum and 10% follicular fluid had a positive influence on the in vitro maturation of canine oocytes and greatly affected spindle size in MI-stage oocytes.

Hyaluronic acid and epidermal growth factor improved the bovine embryo quality by regulating the DNA methylation and expression patterns of the focal adhesion pathway

Focal adhesion pathway is one of the key molecular pathways affected by suboptimal culture conditions during embryonic development. The epidermal growth factor (EGF) and hyaluronic acid (HA) are believed to be involved in the focal adhesion pathway function by regulating the adherence of the molecules to the extracellular matrix. However, regulatory and molecular mechanisms through which the EGF and HA could influence the embryo development is not clear. Therefore, this study aimed to investigate the effect of continued or stage specific supplementation of EGF and/or HA on the developmental competence and quality of bovine preimplantation embryos and the subsequent consequences on the expression and DNA methylation patterns of genes involved in the focal adhesion pathway. The results revealed that, the supplementation of EGF or HA from zygote to the blastocysts stage reduced the level of reactive oxygen species and increased hatching rate after thawing. On the other hand, HA decreased the apoptotic nuclei and increased blastocyst compared to EGF supplemented group. Gene expression and DNA methylation analysis in the resulting blastocysts indicated that, combined supplementation of EGF and HA increased the expression of genes involved in focal adhesion pathway while supplementation of EGF, HA or a combination of EGF and HA during the entire preimplantation period changed the DNA methylation patterns of genes involved in focal adhesion pathway. On the other hand, blastocysts developed in culture media supplemented with EGF + HA until the 16-cell stage exhibited higher expression level of genes involved in focal adhesion pathway compared to those supplemented after the 16-cell stage. Conversely, the DNA methylation level of candidate genes was increased in the blastocysts obtained from embryos cultured in media supplemented with EGF + HA after 16-cell stage. In conclusion, supplementation of bovine embryos with EGF and/or HA during the entire preimplantation period or in a stage specific manner altered the DNA methylation and expression patterns of candidate genes involved in the focal adhesion pathway which was in turn associated with the observed embryonic developmental competence and quality.

Production of collared peccary (Pecari tajacu Linnaeus, 1758) parthenogenic embryos following different oocyte chemical activation and in vitro maturation conditions

To optimize the protocols for assisted reproductive techniques (ARTs) in collared peccary (Pecari tajacu Linnaeus, 1758), we evaluated various conditions for oocyte in vitro maturation (IVM) and chemical activation. Initially, we assessed the IVM rates, cumulus-oocyte complex (COC) quality, and oocyte morphometry in the absence or presence of epidermal growth factor (EGF). There was no difference between the COCs matured in absence or presence of EGF for the expansion of cumulus cells (97.6% ± 1.2 vs. 100% ± 0.0), presence of first polar body (65.9% ± 1.2 vs. 70.5% ± 1.8), nuclear status in second metaphase (62.5% ± 11.6 vs. 68.4% ± 4.9), cytoplasmic maturation (100.0% ± 0.7 vs. 75.0% ± 0.7), reactive oxygen species levels (0.5 ± 0.2 vs. 0.3 ± 0.1), and mitochondrial membrane potential (1.1 ± 0.2 vs. 1.1 ± 0.1). However, the zona pellucida thickness of matured COCs was reduced in the presence of EGF. Thus, the EGF group was used for further experiments. The oocytes were artificially activated with ionomycin and four secondary activator combinations [6-dimethylaminopurine (6D), 6D and cytochalasin B (6D + CB), cycloheximide (CHX), and CHX and CB (CHX + CB)]. The effect of immature COCs based on cumulus cell layers and cytoplasm homogeneity (GI and GII or GIII COCs) on embryonic development and quality was evaluated. There was no difference in the cleavage rates among the groups of secondary activators. The cleavage rates of embryos derived from GI/GII and GIII COCs were greater than 72.2% and 25.0%, respectively. Moreover, treatment with CHX showed a reduction in the cleavage rate of embryos derived from GIII COCs when compared to the cleavage rate of embryos derived from GI/GII COCs (P < 0.05). Nevertheless, higher rates of blastocyst/total GI and GII COCs were observed in the 6D group (27.6% ± 0.3) compared to CHX group (6.9% ± 0.3). Additionally, only 6D treatment resulted in the production of embryos derived from GIII COCs (25.0% ± 0.2). The percentage of the ICM/total cell ratio was also greater in blastocysts derived from 6D (42.5% ± 19.0), 6D + CB (37.9% ± 21.9), and CHX + CB (43.8% ± 19.6) groups when compared to CHX (3.6% ± 0.1) group. Thus, the combination of ionomycin and 6D could produce collared peccary embryos by activation of both GI/GII COCs and GIII COCs. These optimized IVM conditions using EGF and chemical activation using ionomycin and 6D in collared peccaries form the first steps for establishing ARTs to conserve this species.

INFLUÊNCIA DO HEPES NA MATURAÇÃO IN VITRO DE OÓCITOS CANINOS OBTIDOS DE CADELAS EM DIESTRO E ANESTRO

Resumo Diferentemente de outras espécies domésticas, a maturação in vitro (MIV) de oócitos caninos apresenta sucesso limitado. O objetivo deste estudo foi avaliar o efeito do HEPES na maturação in vitro de oócitos caninos obtidos de cadelas em diestro e anestro. Os ovários foram coletados, isolados assepticamente e transportados refrigerados a uma temperatura de 4 ºC. Os complexos cumulus-oócito (CCOs), provenientes das duas fases do ciclo estral, foram submetidos a dois tratamentos: meio TCM-199 com adição de 25 mM de HEPES (GT) e meio sem suplementação (GC). Depois de 72 horas de maturação, os CCOs foram desnudados, fixados e corados com HOESCHT 33342 para avaliação da maturação nuclear. Os oócitos obtidos da fase de anestro e diestro do GT demonstraram, em relação ao grupo GC, maior frequência de oócitos nos estágios de M-II (p<0,01). Comparando-se os diferentes status reprodutivos, observou-se que os oócitos obtidos da fase de diestro apresentaram índices maiores de QVG e M-II. Nossos resultados demonstraram que o HEPES preserva a viabilidade e morfologia oocitária, indispensáveis para a aquisição da competência meiótica, potencializando as taxas de M-II, e que os oócitos obtidos da fase de diestro estão mais aptos a completarem a maturação oocitária.

Influence of growth differentiation factor 9 and bone morphogenetic protein 15 on in vitro maturation of canine oocytes

Growth differentiation factor 9 (GDF-9) and bone morphogenetic protein 15 (BMP-15) have pivotal roles in oocyte development in many species, therefore the aim was to investigate these factors during in vitro maturation (IVM) of canine oocytes. Canine cumulus oocytes complexes (COCs) were cultured in six groups for 72 hr in a supplemented TCM199-Hepes medium as (a) Control group; (b) GDF-9 antibody (Ab); (c) BMP-15 Ab; (d) recombinant human (rh) GDF-9; (e) rh BMP-15 or (f) rh BMP-15 and GDF-9. Data were evaluated by ANOVA. The Abs against GDF-9 or BMP-15 had a negative impact on meiotic development. Higher (p < 0.05) number of oocytes was arrested at GVBD stage when they were incubated with either GDF-9 Ab (64.4 ± 2.1%) or BMP-15 Ab (67.2%± 4.9%) in comparison to those in control group (32.4 ± 7.8%). In contrast, more (p < 0.05) oocytes in control group reached MI (37.4 ± 1.3%) and MII stages (10.2 ± 2.1%) comparing to those groups with GDF-9 Ab (23.1 ± 4.7% MI; 0.0% MII) or BMP-15 Ab (16.4 ± 2.4%MI; 5.9% ± 2.1 MII). Higher rates (p < 0.05) of oocytes in control group stayed still arrested at GV (19.9 ± 8.6%) in comparison to those cultured with either rhGDF-9 (3.7 ± 0.4%) or rhBMP-15 (10.9 ± 0.7%). However, there were no differences in MII rates between oocytes cultured with GDF-9 (14.7 ± 3.1) and BMP-15 (7.8 ± 2.5) separately. But, more oocytes (p < 0.05) reached the MII stage (20.5 ± 3.8%) compared to those exposed to each protein separately and to the control group. These results suggest that these proteins likely contribute to the meiotic development in dogs.

Differential gene-expression profiles from canine cumulus cells of ovulated versus in vitro-matured oocytes

We compared the nuclear maturation status and gene-expression profiles of canine cumulus cells (CCs) derived from cumulus-oocyte complexes (COCs) that were spontaneously ovulated versus those that were matured in vitro. Cumulus-oocyte complexes were retrieved from uteri by surgical flushing (after spontaneous ovulation) or by ovariectomy follicle aspiration and in vitro maturation. The objective of Experiment 1 was to investigate the nuclear maturation status of in vivo- versus in vitro-matured oocytes. The objective of Experiment 2 was to compare gene-expression profiles of CCs derived from in vivo- versus in vitro-matured COCs. Genes analysed are related to cell maturation, development and apoptosis, including GDF9, MAPK1, PTX3, CX43, Bcl2 and BAX; mRNA expression for all of these genes, except for GDF9, differed (P<0.05) between in vivo- and in vitro-matured CCs. In conclusion, we found that gene-expression profiles are related to the quality of CCs and therefore posit that monitoring gene expression could be a useful strategy to guide attempts to improve in vitro culture systems.

Epidermal growth factor improves developmental competence and embryonic quality of singly cultured domestic cat embryos

This study examined the influence of EGF on the expression of EGF receptors (EGFR) and developmental competence of embryos cultured individually versus those cultured in groups. Cat oocytes were in vitro matured and fertilized (IVM/IVF), and cleaved embryos were randomly assigned to one of seven culture conditions: one group each in which embryos were subjected to group culture supplemented with or without 5 ng/ml EGF and five groups in which embryos were subjected to single-embryo culture supplemented with EGF (0, 5, 25, 50 or 100 ng/ml). Morulae, blastocysts and hatching blastocysts were assessed at days 5 and 7; post IVF, respectively, and total blastocyst cell numbers were assessed at day 7. Relative mRNA expressions of EGFR of 2–4-cell embryos, 8–16-cell embryos, morulae and blastocysts cultured in groups or singly with or without EGF supplementation were examined. OCT3/4 and Ki67 in blastocysts derived from the group or single-embryo culture systems with or without EGF supplementation were localized. A higher rate of embryos cultured in groups developed to blastocysts than individually incubated cohorts. Although EGF increased blastocyst formation in the single-embryo culture system, EGF did not affect embryo development in group culture. Expression levels of EGFR decreased in morulae and blastocysts cultured with EGF. An increased ratio of Ki67-positive cells to the total number of cells in the blastocyst was observed in singly cultured embryos in the presence of EGF. However, EGF did not affect the expression of OCT3/4. These findings indicate that EGF enhanced developmental competence of cat embryos cultured singly by stimulating cell proliferation and modulating the EGFR expression at various developmental stages.

Comparative gene expression profiling in human cumulus cells according to ovarian gonadotropin treatments

In in vitro fertilization cycles, both HP-hMG and rFSH gonadotropin treatments are widely used to control human follicle development. The objectives of this study are (i) to characterize and compare gene expression profiles in cumulus cells (CCs) of periovulatory follicles obtained from patients stimulated with HP-hMG or rFSH in a GnRH antagonist cycle and (ii) to examine their relationship with in vitro embryo development, using Human Genome U133 Plus 2.0 microarrays. Genes that were upregulated in HP-hMG-treated CCs are involved in lipid metabolism (GM2A) and cell-to-cell interactions (GJA5). Conversely, genes upregulated in rFSH-treated CCs are implicated in cell assembly and organization (COL1A1 and COL3A1). Interestingly, some genes specific to each gonadotropin treatment (NPY1R and GM2A for HP-hMG; GREM1 and OSBPL6 for rFSH) were associated with day 3 embryo quality and blastocyst grade at day 5, while others (STC2 and PTX3) were related to in vitro embryo quality in both gonadotropin treatments. These genes may prove valuable as biomarkers of in vitro embryo quality.