Quality and Developmental Ability of Dromedary (Camelus dromedarius) Embryos Obtained by IVM/IVF,In VivoMatured/IVF orIn VivoMatured/Fertilized Oocytes

Effect of melatonin supplementation during IVM of dromedary camel oocytes (Camelus dromedarius) on their maturation, fertilization, and developmental rates in vitro

The positive impact of melatonin on in vitro embryo production (IVEP) has been reported in many domestic species; however, no studies have been carried out in camelids. We aimed to evaluate the effects of melatonin supplementation in maturation media on in vitro maturation, fertilization, and preimplantation embryo development of dromedary camel oocytes (experiment 1). We also evaluated the concentrations of total antioxidant capacity (TAC), and malondialdehyde (MDA) in the IVM spent medium in relation to melatonin supplementation. Cumulus oocyte complexes (COCs) were cultured in in vitro maturation media (IVM) supplemented with either 0.0, 25.0, 50.0 or 75.0 μM of melatonin for 30 h. Matured oocytes were then fertilized in vitro with epididymal camel spermatozoa. Following IVF, the resulting embryos were cultured in vitro for seven days. The percentage of maturation, fertilization, cleavage, and embryo developmental rates (morula and blastocyst) was recorded (experiment 1). TAC and MDA levels in the IVM spent maturation media were also evaluated at 30 h post-IVM (experiment 2). The results showed that supplementation of IVM media with 25 μM melatonin significantly improved oocyte nuclear maturation, fertilization (18 h post-insemination; pi), cleavage (day 3 pi), morula (day 5 pi) and blastocyst (day 7 pi) rates as compared with the controls and other melatonin-supplemented groups. Furthermore, the TAC in the IVM spent media was significantly increased (P < 0.05) in 25 μM melatonin supplemented groups than those supplemented with 0.0, 50.0, 75.0 μM melatonin. However, the concentration of MDA was significantly lower (P < 0.05) in IVM media supplemented with 25.0 μM of melatonin when compared with the control and other treatment groups. In conclusion, supplementation of IVM medium with 25 μM of melatonin could enhance the in vitro developmental capacity of dromedary camel oocytes.

Production of blastocysts following in vitro maturation and fertilization of dromedary camel oocytes vitrified at the germinal vesicle stage

Cryopreservation of oocytes would serve as an alternative to overcome the limited availability of dromedary camel oocytes and facilitate improvements in IVP techniques in this species. Our goal was to develop a protocol for the vitrification of camel oocytes at the germinal vesicle (GV) stage using different cryoprotectant combinations: 20% EG and 20% DMSO (VS1), 25% EG plus 25% DMSO (VS2) or 25% EG and 25% glycerol (VS3) and various cryo-carriers; straws or open pulled-straw (OPS) or solid surface vitrification (SSV); and Cryotop. Viable oocytes were cultured in vitro for 30 h. Matured oocytes were fertilized with epididymal spermatozoa and then cultured in vitro in modified KSOMaa medium for 7 days. Survival and nuclear maturation rates were significantly lower (P ≤ 0.05) in oocytes exposed to VS3 (44.8% and 34.0%, respectively) than those exposed to VS1 (68.2% and 48.0%, respectively) and VS2 (79.3% and 56.9%, respectively). Although recovery rates were significantly lower (P ≤ 0.05) in SSV and Cryotop vitrified oocytes (66.9% to 71.1%) than those vitrified by straws with VS1 or VS2 solutions (86.3% to 91.0%), survival rates were higher in the SSV and Cryotop groups (90.7% to 94.8%) than in the straw and OPS groups (68.2% to 86.5%). Among vitrified groups, maturation and fertilization rates were the highest in the Cryotop-VS2 group (51.8% and 39.2%, respectively). These values were comparable to those seen in the controls (59.2% and 44.6%, respectively). Cleavage (22.5% to 27.9%), morula (13.2% to 14.5%), and blastocyst (6.4% to 8.5%) rates were significantly higher (P ≤ 0.05) in SSV and Cryotop groups than in straws. No significant differences were observed in these parameters between the Cryotop and control groups. We report for the first time that dromedary oocytes vitrified at the GV-stage have the ability to be matured, fertilized and subsequently develop in vitro to produce blastocysts at frequencies comparable to those obtained using fresh oocytes.

L-carnitine enhances oocyte maturation and improves in vitro development of embryos in dromedary camels (Camelus dromedaries)

The aim of the present study was to investigate the effect of L-carnitine (LC) addition during either IVM or IVC on the developmental potential of camel oocytes. In Experiment 1; camel oocytes were matured in the absence (control) or presence of different concentrations of LC (0.25 mg, 0.5 mg, 0.75 mg and 1 mg/ml) for 30 h followed by in vitro fertilization and culture up to blastocyst stage. Our results demonstrated that oocytes treated with 0.5 mg/ml LC showed higher (P < 0.05) rates of maturation (74.7%) and fertilization (62.2%) compared with control group, 0.25 and 1 mg/ml of LC (60.2, 63.9, 59.7; 46.2, 48.7, 47.6%, respectively). Addition of 0.5 mg/ml of LC to IVM medium improved the rates of cleavage and embryo development (morula and blastocyst) than those obtained in the control group, 0.25 and 1 mg/ml of LC. No significant differences were noticed between 0.5 and 0.75 mg/ml of LC supplemented groups in term of maturation, fertilization and culture. In Experiment 2; zygotes resulting from in vitro matured (without LC) and fertilized were cultured in embryo culture medium supplemented with different concentrations of LC (0.25 mg, 0.5 mg, 0.75 mg and 1 mg/ml) or without LC (control). Also, the results showed a higher developmental rates to morula and blastocyst stages while adding L-carnitine at a level of 0.5 or 0.75 mg/ml concentration in the culture medium during IVC when compared with other groups. In conclusion, the results demonstrated the usefulness of L-carnitine supplementation at the level of 0.5 mg/ml during IVM or IVC after on the developmental potential of camel oocytes.

Developmental competence of Dromedary camel (Camelus dromedarius) oocytes selected using brilliant cresyl blue staining

The objectives of the present studies were to investigate the developmental capacity of dromedary camel oocytes selected by brilliant cresyl blue (BCB) staining and to investigate the expression of select transcripts in germinal vesicle (GV) stage oocytes. These transcripts included BMP15 and GDF9 as important transcripts for folliculogenesis and oocyte development, Zar1 and Mater as maternal transcripts required for embryonic development, Cyclin B1 and CDK1 as cell cycle regulators and Oct4 and STAT3 as transcription factors. Dromedary camel oocytes were retrieved from ovaries collected at a local slaughterhouse. After exposure to BCB staining, cumulus–oocyte complexes (COCs) from BCB+, BCB− and control (selected based on morphological criteria) groups were subjected toin vitromaturation,in vitrofertilization andin vitroculture. For gene expression studies, after BCB staining cumulus cells were stripped off and the completely denuded GV stage oocytes were used for RT-PCR analysis of selected transcripts. BCB+ oocytes showed higher maturation, and fertilization rates compared with BCB− and control groups. Indices of early embryonic development, namely, cleavage at 48 hours post insemination (hpi), and development to morula at day 5 and day 7 blastocyst rates were also significantly higher in the BCB+ group. RT-PCR revealed a higher expression of BMP15, GDF9, Zar1, Mater, Cyclin B1, CDK1, OCT4 and STAT3 in good quality oocytes that stained positively for BCB (BCB+). Collectively, results provide novel information about the use of BCB screening for selecting good quality oocytes to improvein vitroembryo production in the dromedary camel.

Confocal fluorescence assessment of bioenergy/redox status of dromedary camel (Camelus dromedarius) oocytes before and after in vitro maturation

BACKGROUND

Reproductive biotechnologies in dromedary camel (Camelus dromedarius) are less developed than in other livestock species. The in vitro maturation (IVM) technology is a fundamental step for in vitro embryo production (IVP), and its optimization could represent a way to increase the success rate of IVP. The aim of the present study was to investigate the bioenergy/oxidative status of dromedary camel oocytes before and after IVM by confocal microscopy 3D imaging.

METHODS

Oocytes were retrieved by slicing ovaries collected at local slaughterhouses. Recovered oocytes were examined before and after IVM culture for nuclear chromatin configuration and bioenergy/oxidative status, expressed as mitochondria (mt) distribution and activity, intracellular Reactive Oxygen Species (ROS) levels and distribution and mt/ROS colocalization.

RESULTS

The mean recovery rate was 6 oocytes/ovary. After IVM, 61% of oocytes resumed meiosis and 36% reached the Metaphase II stage (MII). Oocyte bioenergy/redox confocal characterization revealed changes upon meiosis progression. Immature oocytes at the germinal vesicle (GV) stage were characterised by prevailing homogeneous mt distribution in small aggregates while MI and MII oocytes showed significantly higher rates of pericortical mt distribution organized in tubular networks (P<0.05). Increased mt activity in MI (P<0.001) and MII (P<0.01) oocytes compared to GV stage oocytes was also observed. At any meiotic stage, homogeneous distribution of intracellular ROS was observed. Intracellular ROS levels also increased in MI (P<0.01) and MII (P<0.05) oocytes compared to GV stage oocytes. The mt/ROS colocalization signal increased in MI oocytes (P<0.05).

CONCLUSIONS

This study provides indications that qualitative and quantitative indicators of bioenergy and oxidative status in dromedary camel oocytes are modified in relation with oocyte meiotic stage. These data may increase the knowledge of camel oocyte physiology, in order to enhance the efficiency of IVP procedures.

Effects of activin A on the in vitro development and mRNA expression of bovine embryos cultured in chemically-defined two-step culture medium

The purpose of the present study was to evaluate the effects of activin A on the developmental competence of in vitro fertilized (IVF) bovine embryos derived from a two-step defined culture system (C1/C2 medium) during the early or later stages of embryo development. To evaluate the effects of activin A on transcriptional levels, we analysed genes related to blastocyst hatching and implantation and to activin signalling pathway in IVF embryos. Cumulus-oocyte complexes were matured for 22 h and fertilized in vitro. Presumptive zygotes were cultured in the presence or absence of activin A during early (0-120 h, C1) or later (120-192 h, C2) stages. Although the developmental competence of embryos cultured with activin A in C1 medium was not significantly different from their corresponding controls, development to blastocysts (22.4% vs 34.7%; p < 0.05) and the blastocyst hatching rate (9.3% vs 22.4%; p < 0.05) in C2 medium supplemented with 100 ng/ml activin A were significantly higher than in the control group. To evaluate the effect of activin A on transcription, the relative expression levels of genes related to blastocyst hatching and implantation (Na/K-ATPase, E-cad and Glut-1) as well as activin signalling pathway (ActRII, ActRIIB and Smad2) were analysed. Compared to control medium, gene expression of Na/K-ATPase, E-cad, Glut-1, ActRII and ActRIIB was increased in medium supplemented with activin A. In conclusion, this study suggests that activin A, during the later stage of in vitro bovine embryo development, can enhance in vitro development of embryos by increasing hatching rates and affecting expression levels of genes related to hatching and implantation in defined culture medium.