Developmental competence of IVM pig oocytes after SCNT in relation to the shrinkage pattern induced by hyperosmotic treatment

Thermally conductive graphene-based nanofluids, a novel class of cryosolutions for mouse blastocysts vitrification

Limited heating and cooling rates have long been recognized as bottlenecks in improving embryo cryopreservation. As a result, efforts to achieve higher heat transfer rates gave rise to milestones like open cryodevices and minimal media loading. A crucial but commonly ignored variable is heat conduction by cryosolutions. The low heat conductivity of the aqueous media surrounding embryos slows down cooling and heating rates of the embryo, imposing the risk of preventable damages. In this study, we introduce a novel thermally conductive cryosolution based on graphene oxide nanoparticles and test its performance against conventional sucrose-based solutions for vitrification of mouse blastocysts. Replacing sucrose with graphene oxide brought about similar re-expansion, hatching, and implantation rates of post-vitrification embryos while also preventing an array of cellular and molecular stresses. Our results showed significantly reduced oxidative stress, characterized by control-level expression of Sod1 and significant downregulation of Sod2 transcription when graphene oxide was used instead of sucrose. This molecular response was in agreement with the reduced level of reactive oxygen species produced in vitrified/warmed embryos using graphene-based solutions. The downstream impacts of this stress reduction manifested in significant downregulation of two major pro-apoptotic genes, Bax and Trp53, down to the same level as fresh embryos. Interestingly, embryos maintained their spherical shape during dehydration in graphene-based solutions and did not "collapse" when shrinking, like in sucrose-based solutions. These results provide new insights into the benefits of thermally conductive cryosolutions and showcase the potential of graphene oxide as a cryoprotectant in embryo vitrification.

In vitro growth culture in a medium with reduced sodium chloride improves maturation and developmental competence of pig oocytes derived from small antral follicles

The objective of this study was to evaluate the effects of reducing the sodium chloride content in in vitro growth (IVG) medium to 61.6 mM on in vitro maturation (IVM) and embryonic development of pig oocytes derived from small antral follicles (SAF) less than 3 mm in diameter. SAF oocytes were cultured for 2 days to induce IVG in alpha-minimal essential medium with 108 mM NaCl (αMEM-108) or porcine zygote medium (PZM) containing 61.6 mM (PZM-61.6) or 108 mM (PZM-108) NaCl. These media were further supplemented with 1 mM dibutyryl cyclic adenosine monophosphate (dbcAMP) and 10% (v/v) fetal bovine serum. After IVG culture, oocytes were matured for 44 h in our standard IVM medium. The IVG culture in PZM-61.6 significantly increased nuclear maturation (88.0 ± 2.2%) of SAF oocytes compared to that in PZM-108 (77.3 ± 3.9%) or αMEM-108 (75.9 ± 3.8%). After parthenogenesis (PA), the proportions of blastocysts, based on the number of metaphase II (MII) oocytes, induced for PA were not different among IVG oocytes cultured in PZM-61.6 (50.2 ± 3.0%), PZM-108 (46.8 ± 2.9%), or αMEM-108 (45.6 ± 2.9%). The IVM oocytes derived from IVG in PZM-61.6 showed increased perivitelline space (PVS) (12.1 ± 0.6 μm) and intra-oocyte glutathione (GSH) content (1.19 ± 0.04 pixels/oocyte) compared to PVS (8.0 ± 0.5 and 7.4 ± 0.4 μm) and GSH (1.03 ± 0.04 and 1.00 ± 0.04 pixels/oocyte) of oocytes derived from PZM-108 and αMEM-108, respectively. The IVG culture in PZM-61.6 stimulated meiotic resumption after IVG and faster nuclear progression after IVM than that in αMEM-108. After somatic cell nuclear transfer (SCNT), the blastocyst formation of SAF oocytes grown in PZM-61.6 (17.8 ± 3.3%) was higher than that of oocytes grown in PZM-108 (7.5 ± 2.7%) but not different from that of oocytes in αMEM-108 (11.4 ± 3.4%). Regardless of the different osmotic pressures, nuclear maturation was significantly increased by IVG culture in PZM with reduced NaCl (86.8 ± 2.3 and 84.9 ± 4.2% in PZM-61.6 and PZM-61.6 with sorbitol, respectively) than in PZM-108 (70.5 ± 3.4%). Blastocyst formation was not affected by the differences in NaCl content and osmotic pressure of the IVG medium, whereas the mean number of cells in blastocysts was significantly higher following IVG culture in PZM-61.6 than in the other groups. In conclusion, the results demonstrate that, following SCNT in pigs, IVG culture of SAF oocytes in a medium with a reduced NaCl concentration stimulates oocyte maturation and improves subsequent embryonic development.

In vitro maturation on ovarian granulosa cells encapsulated in agarose matrix improves developmental competence of porcine oocytes

In vivo, mammalian oocytes are surrounded by granulosa cells (GCs) that exist in a three-dimensional (3D) microenvironment with soft stiffness. The GCs play an important role for the in vivo growth and development of oocytes, through bidirectional communication between oocytes and GCs. To mimic the cellular microenvironment of a 3D organized follicle, this study designed a co-culture system using porcine ovarian GCs (pGCs) encapsulated in agarose matrix for in vitro maturation (IVM) of pig oocytes. We report the effects of our newly designed co-culture system on IVM and development of pig oocytes. Immature cumulus-oocyte-complexes (COCs) were matured on a 1% (w/v) agarose matrix encapsulated without or with pGCs. The number of pGCs within the agarose matrix was optimized by analyzing the in vitro development of parthenogenetic embryos. Moreover, the role of the ovarian stromal pGCs as feeder cells was assessed by analyzing the PA embryonic development. Subsequently, the effect of pGCs encapsulated in a 3D agarose matrix was evaluated for the developmental competence of pig oocytes by analyzing blastocyst formation after parthenogenetic activation (PA), intra-oocyte GSH and ROS contents, expression levels of BMP15 and BAX, TUNEL (terminal deoxynucleotidyl transferase-mediated d-UTP nick end-labeling) assay, protein expression levels of BMP15, and intra-oocyte ATP levels. The optimized number of pGCs (5 × 10⁴ cells/well) in a 3D agarose matrix led to a significantly higher blastocyst formation, increased BMP15 gene and protein expression, and intra-oocyte ATP levels; moreover, it induced significantly lower intra-oocyte ROS contents, pro-apoptotic BAX gene expression, and apoptotic index, compared to control. Our results demonstrate that application of pGCs as feeder cells encapsulated in the agarose matrix for IVM effectively increases the developmental competence of porcine oocytes.

Influence of oocyte selection, activation with a zinc chelator and inhibition of histone deacetylases on cloned porcine embryo and chemically activated oocytes development

The aim of this study was to evaluate the effects of alternative protocols to improve oocyte selection, embryo activation and genomic reprogramming on in vitro development of porcine embryos cloned by somatic cell nuclear transfer (SCNT). In Experiment 1, in vitro-matured oocytes were selected by exposure to a hyperosmotic sucrose solution prior to micromanipulation. In Experiment 2, an alternative chemical activation protocol using a zinc chelator as an adjuvant (ionomycin + N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) + N-6-dimethylaminopurine (6-DMAP)) was compared with a standard protocol (ionomycin + 6-DMAP) for the activation of porcine oocytes or SCNT embryos. In Experiment 3, presumptive cloned zygotes were incubated after chemical activation in a histone deacetylase inhibitor (Scriptaid) for 15 h, with the evaluation of embryo yield and total cell number in day 7 blastocysts. In Experiment 1, cleavage rates tended to be higher in sucrose-treated oocytes than controls (123/199, 61.8% vs. 119/222, 53.6%, respectively); however, blastocyst rates were similar between groups. In Experiment 2, cleavage rates were higher in zygotes treated with TPEN than controls but no difference in blastocyst rates between groups occurred. For Experiment 3, the exposure to Scriptaid did not improve embryo development after cloning. Nevertheless, the total number of cells was higher in cloned zygotes treated with Scriptaid than SCNT controls. In conclusion, oocyte selection by sucrose as well as treatments with zinc chelator and an inhibitor of histone deacetylases did not significantly improve blastocyst yield in cloned and parthenotes. However, the histone deacetylases inhibitor produced a significant improvement in the blastocyst quality.

In vitro maturation of collared peccary (Pecari tajacu) oocytes after different incubation times

ABSTRACT: Oocyte in vitro maturation (IVM) is the first step of the in vitro reproductive technologies that enables mature oocytes to be generated ex vivo and after used for embryo production. In this sense, the establishment of culture environment, as oocyte incubation time, is essential for the success of the IVM. Therefore, the study was carried out to investigate the relationship between the meiotic potential and the IVM times of collared peccary oocytes, wild mammals of great commercial and ecological interest. Thus, ovaries were collected of females derived from captivity and transported to the laboratory within 1 hour of slaughtering. The oocytes derived from follicles (3-6mm in diameter) were recovered by aspirated and sliced. Good quality oocytes (evenly granulated cytoplasm with a least one layer of surrounding cumulus cells) were selected and subjected to culture in TCM 199 supplemented with 10µg/mL FSH, 10% FBS and 100µM cysteamine at 38.5°C, 5% CO2 and maximum humidity for 24 or 48 hours. After the incubation period, the nuclear status, the presence of first polar body and the expansion of cumulus cells of oocytes were assessed. The data obtained were analyzed by Fisher exact test (P<0.05). A total of four sessions (2-3 females per session) were performed, resulting in eighteen aspirated and sliced ovaries with normal morphological characteristics. An oocyte recovery rate of about 83.1% (59/71) was obtained with 3.3 oocytes/ovary and 2.3 viable oocytes/ovary. After different incubation times, differences (P<0.05) were observed in 24 and 48 hours for expansion of the cumulus cells (38.1% vs. 100%), presence of first polar body (52.4% vs. 90.5%) and nuclear status in second metaphase (19.0% vs. 76.2%), respectively. In conclusion, 48 hours is suitable time for the in vitro maturation of oocytes derived from collared peccaries when compared to the time of 24 hours, according to the meiotic potential observed. Additional studies should be conducted to improve the quality of the oocyte culture environment, as medium composition, aiming to obtain viable mature oocytes for other in vitro biotechnologies.

Sucrose assists selection of high-quality oocytes in pigs

We investigated whether high‐quality in vitro matured (IVM) oocytes can be distinguished from poor ones based on the morphological changes after treatment with hyperosmotic medium containing 0.2 mol/L sucrose in pigs. We hypothesize that IVM oocytes maintaining round shape have higher quality than mis‐shapened oocytes following dehydration. Oocyte quality was verified by determining embryonic developmental competence using in vitro fertilization, nuclear transfer and parthenogenetic activation. In all cases, the round oocytes had greater (p < .05) developmental competence than that of mis‐shapened oocytes in terms of blastocyst rate and total cell number in blastocysts obtained after 6 days of in vitro culture. We also confirm that round aged oocytes are higher in quality than mis‐shapened aged oocytes. In an attempt to find out why high‐quality oocytes maintain a round shape whereas poorer oocytes become mis‐shapened following sucrose treatment, we examined the arrangement of actin microfilaments and microtubules. Abnormal organization of these cytoskeletal components was higher (p < .05) in mis‐shapened oocytes compared to round oocytes after 52 hr of IVM. In conclusion, sucrose treatment helps selection of high‐quality oocytes, including aged oocytes, in pigs. Abnormal cytoskeleton arrangements partly explain for low developmental competence of mis‐shapened oocytes.

Generation of liver-specific TGF-α/c-Myc-overexpressing porcine induced pluripotent stem-like cells and blastocyst formation using nuclear transfer

Transgenic porcine induced pluripotent stem (iPS) cells are attractive cell sources for the development of genetically engineered pig models, because they can be expanded without senescence and have the potential for multiple gene manipulation. They are also useful cell sources for disease modeling and treatment. However, the generation of transgenic porcine iPS cells is rare, and their embryonic development after nuclear transfer (NT) has not yet been reported. We report here the generation of liver-specific oncogenes (TGF-α/c-Myc)-overexpressing porcine iPS (T/M iPS)-like cells. They expressed stem cell characteristics and were differentiated into hepatocyte-like cells that express oncogenes. We also confirmed that NT embryos derived from T/M iPS-like cells successfully developed blastocysts in vitro. As an initial approach toward porcine transgenic iPS cell generation and their developmental competence after NT, this study provides foundations for the efficient generation of genetically modified porcine iPS cells and animal models.

Laser researches on livestock semen and oocytes: A brief review

This article presents a brief review of the past and present literature pertinent to laser effects on sperm motility parameters, improvement of oocyte maturation and characterization of semen in livestock. The aim was, on one hand, to make the readers aware of such knowledge and on the other hand to trigger the interest of the animal reproduction scientific community in attempting some laser techniques that have not yet been fully exploited in the field of artificial insemination. With respect to the conventional methods, laser is a more sensitive and less costly technology that can be used for improving artificial insemination and embryo production system. Since 1980s, laser treatment came on the biological samples scene; its applications have continuously been developed thereafter. Exploitation of laser light by various researchers for improving the reproductive efficiency of sperm cells and the maturation rate in different livestock is demonstrated herein. Laser irradiation, in principal, can increase the production of adenosine triphosphate (ATP) and consequently increases the energy provided to the cell. Since sperm motility and oocyte maturation depend on the energy consumption, an increase in the energy supply to the cells will be of great importance. In addition, the authors also discuss the use of laser spectrochemical analytical techniques, such as laser induced breakdown spectroscopy (LIBS) and laser induced fluorescence (LIF), in characterization of semen samples.