Coculture with porcine luteal cells during in vitro porcine oocyte maturation affects lipid content, cortical reaction and zona pellucida ultrastructure

CONTEXT

In pigs, in vitro fertilisation (IVF) is associated with high polyspermy rates, and for this reason, in vitro embryo production (IVP) is still an inefficient biotechnology. Coculture with somatic cells is an alternative to improve suboptimal in vitro maturation (IVM) conditions.

AIM

This study was conducted to test a coculture system of porcine luteal cells (PLC) and cumulus-oocyte complexes (COC) to improve oocyte metabolism.

METHODS

COC were matured in vitro with PLC. Oocyte lipid content, mitochondrial activity, zona pellucida (ZP) digestibility and pore size, cortical reaction and in vitro embryo development were assessed.

KEY RESULTS

Coculture reduced cytoplasmic lipid content in the oocyte cytoplasm without increasing mitochondrial activity. Although ZP digestibility and ZP pore number were not different between culture systems, ZP pores were smaller in the coculture. Coculture impacted the distribution of cortical granules as they were found immediately under the oolemma, and more of them had released their content in the ZP. Coculture with porcine luteal cells during IVM increased monospermic penetration and embryo development after IVF.

CONCLUSIONS

The coculture of COC with PLC affects the metabolism of the oocyte and benefits monospermic penetration and embryo development.

IMPLICATIONS

The coculture system with PLC could be an alternative for the conventional maturation medium in pigs.

Canine IVM With SOF Medium, Insulin-Transferrin-Selenium, and Low O2 Tension Improves Oocyte Meiotic Competence and Decreases Reactive Oxygen Species Levels

Assisted reproductive technologies in canine species are limited due to the low efficiency of in vitro maturation (IVM). Unlike other mammals, bitches ovulate oocytes in the germinal vesicle stage and complete metaphase II (MII) after 48–72 h in the oviductal environment and become fertilizable. For this reason, we compared two different IVM media, synthetic oviductal fluid (SOF) supplemented with 8% bovine serum albumin (BSA) or a mixture of 8% BSA–2.5% fetal bovine serum (FBS) and TCM-199 with 10% FBS. Additionally, we evaluated the effect of supplementation with insulin-transferrin-selenium (ITS) and low O₂ tension in oocyte maturation, reactive oxygen species (ROS) levels, membrane integrity, and embryo development following parthenogenetic activation (PA). After 72 h of culture, SOF + BSA, SOF + BSA + FBS, and TCM-199 + FBS show 5, 7, and 4% of MII, respectively, without a statistical difference. However, SOF + BSA produced significantly higher degeneration rates compared to SOF + BSA + FBS (44 and 23%, respectively). Remarkably, supplementation with 1 μl/ml of ITS under high O₂ tension demonstrated a beneficial effect by improving maturation rates up to 20% compared to the other groups. Low O₂ tension increased maturation rates to 36.5%, although there were no statistical differences compared to high O₂ tension in the presence of ITS. Lower ROS levels and higher integrity of the cytoplasmic membrane were found in the presence of ITS despite no differences in maturation rates under low O₂ tension groups. Additionally, after PA, 1% development until the eight-cell stage was obtained after activation of in vitro-matured oocytes in the presence of ITS. Taken together, these results indicate that SOF supplemented with 8% BSA and 2.5% FBS is suitable for IVM of canine oocytes and ITS supplementation was beneficial for both high and low O₂ tension. Furthermore, the addition of ITS in the cultured system lowers ROS levels and increases membrane integrity in domestic dog oocytes after IVM.

Coculture of porcine luteal cells during in vitro porcine oocyte maturation affects blastocyst gene expression and developmental potential

Oocyte maturation in culture is still the weakest part of in vitro fertilization (IVF) and coculture with somatic cells may be an alternative to improve suboptimal culture conditions, especially in the pig in which maturation takes more than 44 h. In the present study, we investigated the effect of a coculture system of porcine luteal cells (PLC) during in vitro maturation (IVM) on embryo development and gene expression. Cumulus-oocyte complexes were matured in vitro in TCM-199 with human menopausal gonadotrophin (control) and in coculture with PLC. IVF was performed with frozen-thawed boar semen in Tris-buffered medium. Presumptive zygotes were cultured in PZM for 7 days. The coculture with PLC significantly increased blastocysts rates. Gene expression changes were measured with a porcine embryo-specific microarray and confirmed by RT-qPCR. The global transcription pattern of embryos developing after PLC coculture exhibited overall downregulation of gene expression. Following global gene expression pattern analysis, genes associated with lipid metabolism, mitochondrial function, endoplasmic reticulum stress, and apoptosis were found downregulated, and genes associated with cell cycle and proliferation were found upregulated in the PLC coculture. Canonical pathway analysis by Ingenuity Pathway revealed that differential expression transcripts were associated with the sirtuin signaling pathway, oxidative phosphorylation pathway, cytokines and ephrin receptor signaling. To conclude, the coculture system of PLC during IVM has a lasting effect on the embryo until the blastocyst stage, modifying gene expression, with a positive effect on embryo development. Our model could be an alternative to replace the conventional maturation medium with gonadotrophins with higher rates of embryo development, a key issue in porcine in vitro embryo production.

The antioxidant dimethylthiourea improves IVF efficiency and decreases cumulus cell apoptosis in pigs

Abattoir ovaries, which are the main source of oocytes for reproductive biotechnologies, arrive at the laboratory under ischaemic conditions. Reoxygenation generates reactive oxygen species (ROS) in ischaemic tissues, which could affect oocyte quality. The aim of this study was to evaluate the effect of supplementation of media with dimethylthiourea (DMTU) during the collection and washing of cumulus-oocyte complexes (COC) on ROS levels, COC apoptosis and oocyte nuclear and cytoplasmic maturation. Thus, the collection (TCM-199) and washing (TCM-199 with 10% porcine follicular fluid, sodium pyruvate and antibiotics) media were supplemented with 1 and 10mM DMTU. In the control group, the media were not supplemented with DMTU. Intracellular ROS levels decreased significantly in the DMTU-treated groups (P<0.05). Although no effects on rate of nuclear maturation were observed, DMTU significantly increased sperm penetration rates without increasing polyspermy (P<0.05). The addition of 10mM DMTU to the collection and washing media enhanced IVF efficiency. DMTU did not modify the early or late apoptosis of oocytes. Both concentrations of DMTU significantly increased viability and decreased the apoptosis of cumulus cells (P<0.05). These results suggest that the addition of 1 or 10mM of DMTU to the media during the collection and washing of porcine COCs is useful for decreasing cumulus apoptosis mediated by ROS and for optimising the IVF of porcine oocytes.

Fluorescent redox-dependent labeling of lipid droplets in cultured cells by reduced phenazine methosulfate

Natural and synthetic phenazines are widely used in biomedical sciences. In dehydrogenase histochemistry, phenazine methosulfate (PMS) is applied as a redox reagent for coupling reduced coenzymes to the reduction of tetrazolium salts into colored formazans. PMS is also currently used for cytotoxicity and viability assays of cell cultures using sulfonated tetrazoliums. Under UV (340 nm) excitation, aqueous solutions of the cationic PMS show green fluorescence (λem: 526 nm), whereas the reduced hydrophobic derivative (methyl-phenazine, MPH) shows blue fluorescence (λem: 465 nm). Under UV (365 nm) excitation, cultured cells (LM2, IGROV-1, BGC-1, and 3T3-L1 adipocytes) treated with PMS (5 μg/mL, 30 min) showed cytoplasmic granules with bright blue fluorescence, which correspond to lipid droplets labeled by the lipophilic methyl-phenazine. After formaldehyde fixation blue-fluorescing droplets could be stained with oil red O. Interestingly, PMS-treated 3T3-L1 adipocytes observed under UV excitation 24 h after labeling showed large lipid droplets with a weak green emission within a diffuse pale blue-fluorescing cytoplasm, whereas a strong green emission was observed in small lipid droplets. This fluorescence change from blue to green indicates that reoxidation of methyl-phenazine to PMS can occur. Regarding cell uptake and labeling mechanisms, QSAR models predict that the hydrophilic PMS is not significantly membrane-permeant, so most PMS reduction is expected to be extracellular and associated with a plasma membrane NAD(P)H reductase. Once formed, the lipophilic and blue-fluorescing methyl-phenazine enters live cells and mainly accumulates in lipid droplets. Overall, the results reported here indicate that PMS is an excellent fluorescent probe to investigate labeling and redox dynamics of lipid droplets in cultured cells.

Apoptosis in porcine cumulus-oocyte complexes: Relationship with their morphology and the developmental competence

The aim of this study was to assess the presence and distribution of apoptosis in porcine cumulus-oocyte complexes (COCs) and its relations with COC morphology and developmental competence. The COCs were obtained from slaughterhouse ovaries, classified into A1 (top category), A2, B1, B2, C, and D based on their morphology. A1, A2, and B1 were matured and fertilized in vitro, and blastocyst rate was compared among them. Before and after in vitro maturation (IVM), annexin-V staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays were performed to assess early and late apoptosis, respectively. There was a significant increase in both annexin-V (+) oocytes and TUNEL (+) cumulus cells as morphology further deteriorated. There were no statistical differences regarding annexin-V (+) oocytes within immature and post-IVM COCs, but TUNEL (+) oocytes were only observed in post-IVM COCs. Early and late apoptosis was detected in cumulus cells of all categories of immature and post-IVM COCs. However, the difference was only significant for annexin-V (+). There were no significant differences in embryo development. Therefore, apoptosis increases as the morphological features of the immature COCs decrease. In conclusion, the selection of COCs from Categories A1, A2, and B1 may be used as a selection criterion for in vitro development.

Expression of GnRH receptor and 3βHSD during meiosis and foliculogénesis in Columba livia (Aves: Columbiformes): Histological and immunohistochemical analysis

During the ovarian ontogeny in birds, five fundamental events can be recognized: migration and colonization of the primordial germ cells, differentiation and proliferation of oogonies, an organization of germinal nests, beginning of the meiotic process and folliculogenesis. The knowledge of these events is fundamental for the interpretation of the processes involved in the differentiation of female gametes. However, there are only references for some model species such as Gallus gallus domesticus and Coturnix coturnix. In a previous study, the histological structure of embryonic ovaries of Columba livia was revealed. Therefore, the objective of this work is to characterize the processes of meiosis and folliculogenesis C. livia from the analysis of the expression of the GnRH receptor, the 3βHSD enzyme and the cell proliferation protein PCNA in embryonic and postnatal ovaries. Therefore, the expression of GnRHR, 3βHSD, and PCNA was revealed in histological testicular and ovarian preparations in embryos (stages 41-43) and neonates (2, 5, 7, 10 and 75 days post-hatching). The present study demonstrates that the fate of germline cells is dictated by their location during gonadal development. Thus, the germline cells located in the cortex of the left gonad enter meiosis, while those in the right gonad and those in the medulla of the left ovary fail to go into meiosis. This indicates that somatic signals, instead of an autonomous cellular mechanism, regulate the entry of the germline cells into meiosis in the C. livia embryo. Future studies will be focused on the analysis of proteins associated with meiotic events and folliculogenesis in embryonic and neonatal ovaries of C. livia, to evaluate the regulation of meiosis in vitro.

Effects of EPA on bovine oocytes matured in vitro with antioxidants: Impact on the lipid content of oocytes and early embryo development

The eicosapentaenoic acid (EPA) is an n-3 polyunsaturated fatty acid (PUFA) present in the lipid composition of bovine oocytes. Little is known about the importance of EPA in bovine oocyte maturation and embryo development in vitro. Although previous work suggest that n-3 PUFAs may inhibit oocyte maturation, the available data are inconsistent. In this study, we evaluated the effect of EPA (1, 10, 100 nM) during in vitro maturation (IVM) of bovine oocytes, alone and in combination with vitamin E (VE) or cysteamine (CYS). EPA treatment in IVM decreased oocyte lipid content and affected lipid droplets pattern (P < 0.05). EPA 100 nM reduced oocytes maturation rate (P < 0.05), without affecting cumulus expansion. At the concentrations tested, EPA did not modify embryo development. However, the addition of antioxidants during IVM reduced the levels of reactive oxygen species in the culture system by increasing intracellular glutathione content (P < 0.05). Besides, the combination of EPA with VE or CYS reduced the percentages of MI oocytes after 24 h of IVM (P < 0.05). EPA reduced oocyte lipid content without any detrimental for embryo development.

Chaotic tip trajectories of a single spiral wave in the presence of heterogeneities

Spiral waves have been observed in a variety of physical, chemical, and biological systems. They play a major role in cardiac arrhythmias, including fibrillation, where the observed irregular activation patterns are generally thought to arise from the continuous breakup of multiple unstable spiral waves. Using spatially extended simulations of different electrophysiological models of cardiac tissue, we show that a single spiral wave in the presence of heterogeneities can display chaotic tip trajectories, consistent with fibrillation. We also show that the simulated spiral tip dynamics, including chaotic trajectories, can be captured by a simple particle model which only describes the dynamics of the spiral tip. This shows that spiral wave breakup, or interactions with other waves, are not necessary to initiate chaos in spiral waves.

Anatomical, histological and immunohistochemical study of testicular development in Columba livia (Aves: Columbiformes)

In this work, testicular ontogeny is analyzed at the anatomical, histological and immunohistochemical levels; the latter through the detection of GnRHR and PCNA in the testicles of embryos, neonates and juveniles of Columba livia. We analyzed 150 embryos, 25 neonates and 5 juveniles by means of observations under a stereoscopic magnifying glass and scanning electron microscope (SEM). The histological analysis was performed using hematoxylin-eosin staining techniques and the PAS reaction. For the immunohistochemical analysis, the expression of GnRHR and PCNA in embryos corresponding to stages 41, 43 and in neonates of 2, 5, 7 and 75 days post-hatch was revealed in testicular histological preparations. That gonadal outline is evident in stage 18. In stage 29, the testes are constituted of a medulla in which the PGCs are surrounded by the Sertoli cells, constituting the seminiferous tubules. From stage 37 a greater organization of the tubules is visualized and at the time of hatching the testicle is constituted of the closed seminiferous tubules, formed of the PGCs and Sertoli cells. The Leydig cells are evident outside the tubules. In the juvenile stages, the differentiation of germline cells and the organization of small vessels that irrigate the developing testicle begin to be visible. In the analyzed stages, the immunodetection of the GnRHR receptor and PCNA revealed specific marking in the plasma membrane and in the perinuclear zone for GnRHR and in the nucleus of the germline cells in juvenile testicles for PCNA. These results can be used as a basis for further study of endocrine regulation events during testicular ontogeny in avian species.

Systematic reduction of a detailed atrial myocyte model

Cardiac arrhythmias are a major health concern and often involve poorly understood mechanisms. Mathematical modeling is able to provide insights into these mechanisms which might result in better treatment options. A key element of this modeling is a description of the electrophysiological properties of cardiac cells. A number of electrophysiological models have been developed, ranging from highly detailed and complex models, containing numerous parameters and variables, to simplified models in which variables and parameters no longer directly correspond to electrophysiological quantities. In this study, we present a systematic reduction of the complexity of the detailed model of Koivumaki et al. using the recently developed manifold boundary approximation method. We reduce the original model, containing 42 variables and 37 parameters, to a model with only 11 variables and 5 parameters and show that this reduced model can accurately reproduce the action potential shape and restitution curve of the original model. The reduced model contains only five currents and all variables and parameters can be directly linked to electrophysiological quantities. Due to its reduction in complexity, simulation times of our model are decreased more than three-fold. Furthermore, fitting the reduced model to clinical data is much more efficient, a potentially important step towards patient-specific modeling.

Comparison of Detailed and Simplified Models of Human Atrial Myocytes to Recapitulate Patient Specific Properties

Computer studies are often used to study mechanisms of cardiac arrhythmias, including atrial fibrillation (AF). A crucial component in these studies is the electrophysiological model that describes the membrane potential of myocytes. The models vary from detailed, describing numerous ion channels, to simplified, grouping ionic channels into a minimal set of variables. The parameters of these models, however, are determined across different experiments in varied species. Furthermore, a single set of parameters may not describe variations across patients, and models have rarely been shown to recapitulate critical features of AF in a given patient. In this study we develop physiologically accurate computational human atrial models by fitting parameters of a detailed and of a simplified model to clinical data for five patients undergoing ablation therapy. Parameters were simultaneously fitted to action potential (AP) morphology, action potential duration (APD) restitution and conduction velocity (CV) restitution curves in these patients. For both models, our fitting procedure generated parameter sets that accurately reproduced clinical data, but differed markedly from published sets and between patients, emphasizing the need for patient-specific adjustment. Both models produced two-dimensional spiral wave dynamics for that were similar for each patient. These results show that simplified, computationally efficient models are an attractive choice for simulations of human atrial electrophysiology in spatially extended domains. This study motivates the development and validation of patient-specific model-based mechanistic studies to target therapy.

Vesicles Cytoplasmic Injection: An Efficient Technique to Produce Porcine Transgene-Expressing Embryos

The use of vesicles co-incubated with plasmids showed to improve the efficiency of cytoplasmic injection of transgenes in cattle. Here, this technique was tested as a simplified alternative for transgenes delivery in porcine zygotes. To this aim, cytoplasmic injection of the plasmid alone was compared to the injection with plasmids co-incubated with vesicles both in diploid parthenogenic and IVF zygotes. The plasmid pcx-egfp was injected circular (CP) at 3, 30 and 300 ng/μl and linear (LP) at 30 ng/μl. The experimental groups using parthenogenetic zygotes were as follows: CP naked at 3 ng/μl (N = 105), 30 ng/μl (N = 95) and 300 ng/μl (N = 65); Sham (N = 105); control not injected (N = 223); LP naked at 30 ng/μl (N = 78); LP vesicles (N = 115) and Sham vesicles (N = 59). For IVF zygotes: LP naked (N = 44) LP vesicles (N = 94), Sham (N = 59) and control (N = 79). Cleavage, blastocyst and GFP+ rates were analysed by Fisher's test (p < 0.05). The parthenogenic CP naked group showed lower cleavage respect to control (p < 0.05). The highest concentration of plasmids to allow development to blastocyst stage was 30 ng/μl. There were no differences in DNA fragmentation between groups. The parthenogenic LP naked group resulted in high GFP rates (46%) and also allowed the production of GFP blastocysts (33%). The cytoplasmic injection with LP vesicles into parthenogenic zygotes allowed 100% GFP blastocysts. Injected IVF showed higher cleavage rates than control (p < 0.05). In IVF zygotes, only the use of vesicles produced GFP blastocysts. The use of vesicles co-incubated with plasmids improves the transgene expression efficiency for cytoplasmic injection in porcine zygotes and constitutes a simple technique for easy delivery of plasmids.

Structural variations in metal complexes of a tertiary α-hydroxyoxime

A ligand based on commercial solvent extractant is found to support mono-, di-, and tri-nuclear coordination complexes.

Reproductive aspects of Dendropsophus sanborni (Anura, Hylidae) in northeastern Argentina

Reproductive aspects of Dendropsophus sanborni (Anura, Hylidae) in northeastern Argentina. The aim of this investigation was to characterize reproductive aspects of Dendropsophus sanborni (Schmidt, 1944) (Anura, Hylidae) in the northwest of Corrientes province, in northeastern Argentina. The reproductive cycles of males and females, the existence of sexual dimorphism and the male’s vocalization period were analyzed. Samplings were made from September 2011 to August 2012. Dendropsophus sanborni showed a prolonged reproductive pattern because reproductive activity was observed during most part of the year. Calling males were recorded all months except in July. The spermatogenic cycle can be characterized as potentially continuous. In males, snout-vent length was significantly correlated with mean testicular volume. The species showed sexual dimorphism in body mass, with females larger than males. Post-ovulatory females were found from March to June and most females had oocytes at different stages of maturity, with abundant post-vitellogenic oocytes from August to December.

Effects of differential pulse frequencies of chicken gonadotrophin-releasing hormone-I (cGnRH-I) on laying hen gonadotrope responses in vitro

The aim of this work was to determine the effects of cGnRH I pulse frequencies on FSH and LH release and the changes in features and number of cultured laying hen FSH-cells and LH-cells in vitro. Primary adenohypophyseal cell cultures taken from laying hens were stimulated by four 5 min pulses using 1 or 10 nM cGnRH, administered with interpulses between pulses at 15, 30 or 60 min. Pulse frequencies and dose dependent effects were examined in six separate experiments including two controls. After the last interpulse time, the supernatants were collected and stored at -70° C until the performance of an indirect enzyme-linked immunosorbent assay (ELISA) using chicken LH and chicken FSH antisera at 1:1000 and 1:2000 dilutions, respectively. Supernatants were coated in duplicate on the inner surface of Immulon 2 plates and later blocked with the optimal solutions. They were incubated with each antiserum and subsequently with isotype-specific peroxidase-labeled anti-rabbit antibodies. Hydrogen peroxide/o-phenylenediamine was added as substrate/chromogen and the optical density (OD) was determined at 492 nm. The ABC immunocytochemical method was performed to characterize and re-count the gonadotropes employing anti-chicken FSH and anti-chicken LH as primary antibodies. The number of FSH-LH cells was obtained using stereological analysis and the data were statistically processed. The ODs obtained for each anti-hormone were compared with the control groups and with each other. Significant differences were found in number of aggregated-positive LH cells, which decreased with 1 nM cGnRH-I, 15 vs. 30 min pulses, increased with 30 vs. 60 min pulses, and also with 10 nM cGnRH-I, 30 vs. 60 min pulses. Aggregated positive FSH cells, however, did not show significant differences in percentage at any GnRH dose or pulse frequencies, but did show activity at low pulse frequencies of 15 and 30 min. The results suggest that LH cells varied in percentage in a dose dependent manner at higher pulse frequency (15 min) and were dose independent at low pulse frequency (60 min) and showed inactive features; while FSH cell numbers were unaffected showing features of activity at low pulse frequencies. High and moderate pulse frequencies of cGnRH-I (15-30 min) increased the FSH release in dose independent manner without changes in features or percentage of FSH cells. Low pulse frequency (60 min) of cGnRH-I increased LH release dose independently disminished LH cell percentage and showed changes in cells' features. These results in avian cells showed differences in responses to GnRH pulse frequencies from those reported earlier in mammals.

Hepatic hemangiomas vs metastases: MR differentiation at 1.5 T

We retrospectively studied the value of MR imaging at 1.5 T in distinguishing hepatic hemangiomas (n = 15) from metastases (n = 15) by using (1) lesion/liver signal-intensity ratios, (2) contrast/noise ratios, and (3) T2 relaxation time on long TR/TE spin-echo (SE) sequences. Lesion/liver margin sharpness, lesion shape, and overall lesion morphologic pattern were evaluated also. Univariate logistic regression analysis of the quantitative data showed that T2 was the only statistically significant (p less than .02) variable for distinguishing a hemangioma from a metastasis. A receiver-operator-characteristic plot of T2 produced an area of 0.80 (+/- 0.08). T2 values for these lesions still overlapped with those for metastases. Morphologically, hemangiomas were sharply marginated (80%), rounded or oval (93%), homogeneous, hyperintense lesions (73%), whereas metastases were poorly marginated (66%) and inhomogenous (67%) lesions. The marked, hyperintense appearance was present in 27% of metastases. Retrospective, multivariate logistic regression analysis of T2 and the presence of hyperintense morphology did not improve results based on T2 alone. Morphologic criteria are helpful in differentiation, as some metastases have a prolonged T2 and are not homogenous, hyperintense lesions. In cases where T2 or morphology are equivocal, other diagnostic tests may help confirm the MR findings. We currently use a T2 of greater than 88 msec and the presence of hyperintense morphology to diagnose hemangiomas. Despite both quantitative and qualitative analysis, data for these hemangiomas and metastases still overlap.