Detection of the hyaluronan receptor CD44 in the bovine oviductal epithelium

Hyaluronan is involved in fundamental reproductive events such as sperm storage in the female reproductive tract, fertilization, and early embryo development, these functions are presumably mediated by its major cell surface receptor, CD44. The present study was conducted to investigate the presence and localization of CD44 in the bovine oviductal epithelium, using immunohistochemical and Western blot methods on tissue sections and epithelial cell extracts collected from the uterotubal junction (UTJ), isthmus, and ampulla of animals in the oestrus or luteal phase of the oestrous cycle. While positive immunolabelling for CD44 was found on the ad-luminal surface and supra-nuclear region of epithelial cells in all tubal segments investigated, in the UTJ, there were epithelial cells in which the entire cytoplasm positively stained. We found no differences in terms of CD44-positive staining between the different stages of the oestrous cycle. Presence of CD44 was detected by Western blotting in the tubal epithelium as a single band at 200 kDa. Although it appeared in all tubal segments, the expression of CD44 protein was more accentuated in the sperm reservoir (UTJ) than in the other segments. This is the first time CD44 has been detected in the epithelium of the tubal sperm reservoir in cattle, suggesting a pathway for the action of hyaluronan in this segment.     

猪卵母细胞体外成熟的影响因素

卵母细胞是胚胎工程和发育生物学的重要组成部分,它是体外受精、性别控制、克隆及转基因等技术成功与否的前提和关键。本文初步探讨猪卵母细胞体外成熟的影响因素。     

Role of acidification elicited by sialylation and sulfation of zona glycoproteins during oocyte maturation in porcine sperm-zona pellucida interactions

The porcine zona pellucida (ZP) undergoes biochemical changes during the final phase of maturation prior to fertilization. The present study was conducted to elucidate whether the acidification of ZP glycoproteins during porcine oocyte maturation influences sperm-ZP interactions. Two-dimensional gel electrophoresis clearly demonstrated that ZP acidification occurred in accordance with the sialylation and sulfation of ZP glycoproteins in oocytes matured for 44 h. The increases in the incidences of sperm penetration and polyspermy with the progress of the IVM culture period were significantly suppressed by ZP desialylation on treatment with neuraminidase as a consequence of reductions in the number of sperm bound to ZPs and the acrosome reaction (AR) in ZP-bound sperm (P<0.05). In contrast, the blocking of ZP sulfation by NaClO(3) treatment during IVM markedly reduced the incidence of polyspermy with no inhibitory effect on penetration, but the number of sperm bound to ZPs and the rate of AR-inducing sperm were decreased to the same level as in desialylated oocytes. The results indicate that ZP sulfation influences sperm-ZP interactions in a ZP sialylation-independent manner. Moreover, sialylation and sulfation were not associated with a protective proteolytic modification of the ZP matrix before fertilization. These findings suggest that ZP acidification elicited by the sialylation and sulfation of ZP glycoproteins during oocyte maturation contributes to the porcine ZP acquiring the capacity to accept sperm.     

Steroidogenesis and the influence of MAPK activity during in vitro maturation of porcine cumulus oocyte complexes

The aim of this study was to investigate steroidogenesis within porcine cumulus oocyte complexes during in vitro maturation and to examine the possible influence of the mitogen-activated protein kinase (MAPK). Porcine cumulus oocyte complexes were matured in vitro with and without the MAPK kinase inhibitor U0126 for 0, 5, 26 and 46 h. The 17β-estradiol and progesterone concentration in the culture medium were then determined. In addition, the mRNA levels of StAR, Cyp11A1, 3β-HSD and Cyp19A1 in cumulus cells were analysed by RT-PCR. Using an immunoblot, the MAPK phosphorylation in cumulus cells and oocytes was examined. During the first 26 h of in vitro maturation, 17β-estradiol secretion was predominant, whereas, after a culture period of 46 h, the progesterone secretion decreased conspicuously. Under the influence of U0126, the secretion of 17β-estradiol increased progressively during the complete maturation period, while progesterone secretion was completely inhibited. The mRNA levels of StAR and Cyp11A1 were not altered by U0126; however, corresponding to the hormone secretion, the gene expression of Cyp19A1 was up-regulated and the expression of 3β-HSD down-regulated. The results suggested an influence of the MAPK on steroidogenesis in cumulus cells comparable to a luteinization factor. Hormone synthesis in cumulus cells during oocyte maturation seems to be regulated by altering expression of Cyp19A1 and 3β-HSD.     

DRP1 deficiency induces mitochondrial dysfunction and oxidative stress-mediated apoptosis during porcine oocyte maturation

Background: Environmental pollution induces oxidative stress and apoptosis in mammalian oocytes, which can cause defects in reproduction;however, the molecular regulation of oxidative stress in oocytes is still largely unknown. In the present study, we identified that dynamin-related protein 1(DRP1) is an important molecule regulating oocyte mitochondrial function and preventing oxidative stress/apoptosis. DRP1 is a member of the dynamin GTPase superfamily localized at the mitochondrial-endoplasmic reticulum interaction site, where it regulates the fission of mitochondria and other related cellular processes.Results: Our results show that DRP1 was stably expressed during different stages of porcine oocyte meiosis, and might have a potential relationship with mitochondria as it exhibited similar localization. Loss of DRP1 activity caused failed porcine oocyte maturation and cumulus cell expansion, as well as defects in polar body extrusion.Further analysis indicated that a DRP1 deficiency caused mitochondrial dysfunction and induced oxidative stress,which was confirmed by increased reactive oxygen species levels. Moreover, the incidence of early apoptosis increased as detected by positive Annexin-V signaling.Conclusions: Taken together, our results indicate that DRP1 is essential for porcine oocyte maturation and that a DRP1 deficiency could induce mitochondrial dysfunction, oxidative stress, and apoptosis.     

Phosphorylation of inositol 1,4,5-triphosphate receptor 1 during in vitro maturation of porcine oocytes

During fertilization in mammalian species, a sperm-induced intracellular Ca²⁺ signal ([Ca²⁺]_i) mediates both exit of meiosis and oocyte activation. Recently, we demonstrated in mouse oocytes that the phosphorylation levels of inositol 1,4,5 trisphosphate receptor type1 (IP₃R1), the channel responsible for Ca²⁺ release and oscillations during fertilization, changed during maturation and fertilization. Therefore, we examined the expression and phosphorylation of IP₃R1 during in vitro maturation of pig oocytes. Here, our present study shows that expression of IP₃R1 protein did not change during maturation, although the phosphorylation status of the receptor, specifically at an MPM-2 epitope, did. We found that while at the beginning of maturation IP₃R1 lacked MPM-2 immunoreactivity, it became MPM-2 reactive by 24 h and reached maximal reactivity by 36 h. Interestingly, the acquisition of MPM-2 reactivity coincided with the activation of p34^cdc2 kinase and mitogen-activated protein kinase (MAPK), which are involved in meiotic progression. Following completion of maturation, inactivation of MAPK by U0126 did not affect IP₃R1 phosphorylation, although inactivation of p34^cdc2 kinase by roscovitine dramatically reduced IP₃R1 phosphorylation. Neither inhibitor affected total expression of IP₃R1. Altogether, our results show that IP₃R1 undergoes dynamic phosphorylation during maturation and this might underlie the generation of oscillations at fertilization.     

Inhibition of mitogen activated protein kinase activity induces parthenogenetic activation and increases cyclin B accumulation during porcine oocyte maturation

The inhibition of mitogen activated protein kinase (MAPK) activation during porcine oocyte maturation leads to decreased maturation promoting factor (MPF) activity and to the induction of parthenogenetic activation. In the present study, in order to analyze the mechanism underlying the suppression of MPF activity in MAPK-inhibited porcine oocytes, we injected mRNA of SASA-MEK, a dominant negative MAPK kinase, or antisense RNA of c-mos, a MAPK kinase kinase, into immature porcine oocyte cytoplasm. The injection of SASA-MEK mRNA or c-mos antisense RNA inhibited the MAPK activity partially or completely, respectively, decreased the MPF activity slightly or significantly, respectively, and induced parthenogenetic activation in 17.1% or 96.6% of mature oocytes, respectively, although no parthenogenetic activation was observed in the control oocytes. Immunoblotting experiments revealed that cyclin B accumulation in these MAPK-suppressed porcine oocytes was increased significantly after 50 h of culture and that a considerable amount of MPF was converted into inactive pre-MPF by hyperphosphorylation. These results indicate that the inhibition of MAPK activity in porcine oocytes did not promote cyclin B degradation but rather suppressed it; also the decrease in MPF activity in MAPK-suppressed porcine oocytes correlated with the conversion of active MPF into inactive pre-MPF.     

Dynamic changes in histone acetylation during sheep oocyte maturation

The changes in histone acetylation are not always consistent in various cell types and at different developmental stages. We immunostained specific antibodies against acetylated lysine 9 of histone H3 and acetylated lysines 5 and 12 of histone H4 in an effort to understand the detailed changes in histone acetylation during sheep oocyte meiosis. We found that the acetylation fluorescence signals of H3/K9 and H4/K12 on chromatin appeared intensively in the germinal vesicle (GV), late-GV (L-GV), and germinal vesicle breakdown (GVBD) stages and became weak in metaphase I (MI); however staining reappeared in anaphase I-telophase-I (AI-TI) and metaphase II (MII). Furthermore, staining was detected in the first polar bodies. The fluorescence signals of H4/K5 first appeared in the MI stage and became intensive in the AI-TI stage; however they were barely detectable in MII stage chromosomes and first polar bodies. We conclude that the acetylation patterns of H3/K9 and H4/K12 during oocyte meiotic maturation are similar and that the pattern of H4/K5 is unique.     

Resveratrol compares with melatonin in improving in vitro porcine oocyte maturation under heat stress

Background: Resveratrol, an important phyto-antioxidant commonly found in grapes, mulberry, and other plants,has a variety of functions including anti-aging, anti-cancer and anti-inflammatory activities. In the current study, we investigated the beneficial effects of resveratrol on in vitro porcine oocyte maturation under heat stress(HS). The effect of resveratrol, melatonin and their combination on alleviating HS was compared according to the maturation rate of oocytes and the development competence of embryos after parthenogenetic activation(PA).Results: Supplementation with resveratrol(2.0 μmol/L) not only improved the nuclear maturation but also raised the blastocyst rate of porcine embryos' PA from oocytes that underwent HS by increasing their glutathione(GSH)level, reducing reactive oxygen species(ROS) and up-regulating the expression of Sirtuin 1(SIRT1). It was also found that melatonin(10~(-7)mol/L) and the combination of resveratrol(2.0 μmol/L) plus melatonin(10~(-7)mol/L) exhibited more potent effects than resveratrol alone regarding their protective activities on oocyte maturation under HS.Conclusions: This study compared the efficiencies of resveratrol, melatonin and their combination for protecting porcine oocytes from heat stress. The mechanisms are attributed to the fact that each treatment may have different ability to regulate the synthesis of steroid hormones and the expression of mature related genes.     

The risk of using monoclonal or polyclonal commercial antibodies: controversial results on porcine sperm CD44 receptor identification

Presence of the hyaluronan (hyaluronic acid, HA) receptor CD44 on spermatozoa has been difficult to pursue, mostly obeying to the use of different commercial mono‐ and/or polyclonal antibodies, often lacking proper controls. Here, we describe how the presence (Western blotting) and specific location (immunocytochemistry) of the CD44 receptor differs in ejaculated pig spermatozoa depending on the type of antibody and protocol used. While we were able to detect binding to spermatozoa and mark its presence in the sperm membrane, the use of blocking peptides clearly indicated that only the monoclonal antibody could confirm the specific presence and location of the CD44 receptor, whereas the polyclonal antibody was detecting multiple presumed CD44 isoforms or degraded proteins thus proving unspecific. These results call for strict protocols when attempting immunological determination of sperm membrane receptors.     

兔卵母细胞成熟过程中组蛋白H3Ser10磷酸化表达分析

为研究卵母细胞成熟过程中组蛋白H3第10位丝氨酸(H3Ser10)磷酸化变化规律及其表达水平,本研究以体外成熟免卵母细胞为材料,采用免疫荧光标记方法检测兔卵母细胞成熟各时期组蛋白H3Ser10磷酸化的动态分布,同时探讨不同浓度组蛋白磷酸化激酶抑制剂(ZM447439)处理卵母细胞对组蛋白H3Ser10磷酸化表达的影响.结果显示:(1)兔卵母细胞组蛋白H3Ser10磷酸化始于生发泡破裂期(GVBD),且表达水平最高;第1次减数分裂中期(MⅠ期)磷酸化水平降低,第1次减数分裂后期(AⅠ期)及第2次减数分裂中期(MⅡ期)磷酸化水平呈上升趋势,但均比GVBD期低.(2)低浓度ZM447439对兔卵母细胞核成熟进程影响不大,当其浓度增加到30 μmol/L时,93.5％的卵母细胞停留在GVBD期.(3)ZM447439浓度为5μmol/L时,20.7％卵母细胞H3Ser10去磷酸化,其他卵母细胞H3Ser10磷酸化信号与未处理组相似;当ZM447439浓度增加到30μmol/L时,大多数卵母细胞中的H3Ser10磷酸化消失.以上结果表明:兔卵母细胞组蛋白H3Ser10磷酸化始于GVBD期,且一直持续到MⅡ期,GVBD期磷酸化水平最高.ZM447439可有效抑制兔卵母细胞减数分裂的恢复,且随其浓度的增加,组蛋白H3Ser10磷酸化水平降低;当浓度达30μmol/L时,卵母细胞组蛋白H3Ser10终止磷酸化.     

Changes in follicular endocrinology during final maturation of porcine oocytes

Thirty-one gilts were ovariectomized between 21 and 34 hr after the onset of estrus to compare changes in follicular endocrinology with stages of oocyte maturation. Oocytes were recovered from 6 to 8 mm follicles and classified by stage of meiosis. Remaining follicular fluid was assayed for steroids and dermatan sulfate. Amounts of prostaglandin F2 alpha (PGF2 alpha) and E2 (PGE2) were measured in intramural tissues. Coincident with germinal vesicle breakdown, the follicular content of all steroids except testosterone decreased (P less than .05). As oocytes approached metaphase II, the amount of progesterone within follicles increased (P less than .05), and estradiol continued to decrease (P less than .05). The pattern of dermatan sulfate content was biphasic and peaked at germinal vesicle breakdown and anaphase stages. Amounts of PGF2 alpha and PGE2 within intramural tissues increased (P less than .05) throughout oocyte maturation. Follicular atresia was evident during estrus; however, more (P less than .05) atretic follicles were recovered at germinal vesicle than metaphase II stages (20 vs 3%, respectively). Follicular development, within a gilt, was skewed (P less than .05) and classification of follicles by hormone content demonstrated that a majority were more mature than a minority of less mature follicles. These data suggest that follicular maturation and oocyte development are highly correlated in swine. Furthermore, partitioning the follicular variability by hour and stage of oocyte maturation allowed for more precise assessment of follicular endocrinology than previously reported.     

Crocin supplementation during oocyte maturation enhances antioxidant defence and subsequent cleavage rate

The purpose of the present study was to assess the effect of crocin supplementation during oocyte maturation on the antioxidant defence and anti‐apoptotic ability and subsequent developmental competence of porcine oocytes. Oocytes were cultured in media containing 0, 300, 400 or 500 µg/ml of crocin. Upon maturation, the maturation rates, reactive oxygen species (ROS) and glutathione (GSH) levels, mRNA expression of genes (SOD, CAT, GPx, Bcl‐2, BAX and Caspase3), expression of cleaved caspase3 and subsequent embryo cleavage rates were measured. Results indicated that the maturation rate of the 400 µg/ml group was 86.80% (p < 0.01). The ROS concentration of the 500 µg/ml group was the lowest (p < 0.01). The GSH concentration of the 400 µg/ml group was the highest (p < 0.01). The SOD, CAT and GPx mRNA expression levels were the highest in the 300, 400 and 500 µg/ml groups, respectively, with the expression levels of all genes being significantly higher than that of the control group (p < 0.01). The Bcl‐2/BAX mRNA expression ratio in 400 and 500 µg/ml groups significantly higher than other groups and significantly decreased caspase3 expression level (p < 0.01). The expression level of cleaved caspase3 in the 500 µg/ml treatment group was the lowest, significantly lower than that of the control group (p < 0.01). The cleavage rate of the 400 µg/ml group was 62.50% (p < 0.01). These experimental results show that the supplementation of in vitro culture medium with 400 µg/ml of crocin significantly enhanced the antioxidant defence and anti‐apoptotic ability and subsequent cleavage rate of porcine embryo.     

Effects of E2 binding enzyme UBC9 on porcine oocyte maturation,apoptosis and embryo development

SUMOylation is a dynamic post-translational modification process. However, the function of small ubiquitin-like modifiers (SUMOs) in the maturation of porcine oocytes and embryo growth is not well known. Therefore, the aim of this study was to investigate the effect of E2 binding enzyme UBC9 on the expression of SUMO-1 protein during the in vitro maturation of porcine oocytes and embryo development after in vitro fertilization. Four groups were used: 0 (Control), 5, 10 and 15 µg/ml UBC9. Western blotting, flow cytometry and RT-qPCR were used to detect the in vitro maturation of porcine oocytes, SUMO-1 content, viability and the expression of apoptotic genes. Compared to those in the control treatment, the maturation rate (p < .05) and viability (p < .01) of oocytes in the 5 μg/ml treatment group decreased significantly. SUMO-1 protein markers appeared at 59 and 71 kDa and the content of SUMO-1 protein in the 10 µg/ml treatment group decreased significantly (p < .05). In the expression of apoptosis-related genes, Bcl-2 gene expression was significantly downregulated in the 10 μg/ml treatment group (p < .05). However, Bax and Caspase-3 were significantly upregulated in the 5 μg/ml treatment group (p < .05). During embryonic development, the cleavage rate of oocytes in the 10 µg/ml treatment group was significantly reduced (p < .05), whereas blastocyst formation rate in the 5 µg/ml treatment group was significantly reduced. UBC9 regulates SUMO-1 content in mature pig oocytes in vitro, which affects oocyte maturation rate, viability, apoptotic genes expression and embryo development after fertilization.     

Experimental studies of the function of cumulus cells during extracorporeal oocyte maturation in the pig]

In order to study in more detail the functional significance of the granulosa cell reaction for the in vitro oocyte maturation in the pig, 412 oocytes taken from Graafian follicles and 510 taken from tertiary follicles were grown on different culture media. 147 oocytes, which during in vitro maturation showed a granulosa cell reaction, were transplanted and were utilized to study their embryonic developmental potentialities. It was possible to induce the granulosa cell reaction in about two-thirds of oocytes by the addition of the fluid taken from Graafian follicles. Denudation of oocytes led to a severe inhibition of maturation. Only one-third of the transplanted oocytes showed normal embryonic developmental potentialities. The findings suggest that maturation of the oocyte nucleus is related directly to the granulosa cell reaction, while the maturation of the cytoplasm is independent of it.     

Distribution and viability of spermatozoa in the canine female genital tract during post-ovulatory oocyte maturation

Background

Unlike other domestic mammals, in which metaphase-II oocytes are ovulated, canine ovulation is characterized by the release of primary oocytes, which may take 12 to up to 36 hours. Further 60 hours are needed for maturation to secondary oocytes which then remain fertile for about 48 hours. Oestrus takes 7 to 10 days on average and may start as early as a week before ovulation. This together with the prolonged process of post-ovulatory oocyte maturation requires an according longevity of spermatozoa in the female genital tract in order to provide a population of fertile sperm when oocytes have matured to fertilizability. Therefore the distribution and viability of spermatozoa in the bitch genital tract was examined during post-ovulatory oocyte maturation.

Methods

Thirteen beagle bitches were inseminated on the day of sonographically verified ovulation with pooled semen of two beagle dogs containing one billion progressively motile spermatozoa. Ovariohysterectomy was performed two days later (group 1, n = 6) and four days later (group 2, n = 7). The oviduct and uterine horn of one side were flushed separately and the flushing’s were checked for the presence of gametes. The oviducts including the utero-tubal junction and the uterine horns, both the flushed and unflushed, were histologically examined for sperm distribution.

Results

The total number of spermatozoa recovered by flushing was low and evaluation of viability was limited. Prophase-I oocytes were collected from oviduct flushing in group 1, whereas unfertilized metaphase-II oocytes were detected in group 2. From day 2 to day 4 after ovulation a significant decrease in the percentage of glands containing sperm (P<0.05) and a marked reduction of the mean sperm number in uterine horn glands were observed. A concomitant diminution of spermatozoa was indicated in the utero-tubal junction accompanied by a slight increase in sperm numbers in the mid oviduct.

Conclusions

Oocyte maturation to metaphase-II stage is accompanied by a continuous sperm detachment and elimination in the uterine horns. Entrance of spermatozoa into the caudal oviduct seems to be steadily controlled by the utero-tubal junction thus providing a selected sperm population to be shifted towards the site of fertilization when oocyte maturation is completed.     

Chlorogenic acid supplementation during in vitro maturation improves maturation,fertilization and developmental competence of porcine oocytes

Chlorogenic acid (CGA) is a quinic acid conjugate of caffeic acid, and a phytochemical found in many fruits and beverages that acts as an antioxidant. The present study investigated the effects of CGA supplementation during in vitro maturation (IVM), on in vitro development of porcine oocytes, to improve the porcine in vitro production (IVP) system. Oocytes were matured either without (control) or with CGA (10, 50, 100 and 200 μM). Subsequently, the matured oocytes were fertilized and cultured in vitro for 7 day. The rates of maturation, fertilization and blastocyst formation of oocytes matured with 50 μM CGA were significantly (p < .05) higher than those of the control oocytes. Hydrogen peroxide (H₂O₂) is one of the reactive oxygen species and induces DNA damage in porcine oocytes. When oocytes were matured with 1 mM H₂O₂ to assess the protective effect of CGA, 50 μM CGA supplementation improved the maturation rate and the proportion of DNA‐fragmented nuclei in oocytes compared with control oocytes matured without CGA. Moreover, when oocytes were matured with either 50 μM CGA (control) or caffeic acid (10, 50 and 100 μM), the rates of maturation, fertilization and the blastocyst formation of oocytes matured with 50 μM CGA were similar to those of oocytes matured with 10 and 50 μM caffeic acid. Our results suggest that CGA has comparable effects to caffeic acid, and IVM with 50 μM CGA is particularly beneficial to IVP of porcine embryos and protects oocytes from DNA damage induced by oxidative stress. Supplementation of CGA to the maturation medium has a potential to improve porcine IVP system.     

Effects of the E1 activating enzyme UBA2 on porcine oocyte maturation,apoptosis, and embryonic development in vitro

The purpose of this study was to investigate the effect of the E1 activating enzyme UBA2 on the expression of the SUMO-1 protein during in vitro maturation (IVM) of pig oocytes and embryonic development. In the 5 μg/ml UBA2 treatment group, the expression of the anti-apoptotic gene Bcl-2 and the embryo cleavage rate was significantly increased, while the proapoptotic gene Bax was significantly reduced. When 10 μg/ml UBA2 was added, the in vitro maturation rate, blastocyst rate, and SUMO-1 protein content of oocytes increased significantly (p < .05), and the expression of proapoptotic gene Caspase3 was significantly decreased (p < .05), while the viability of cumulus cells was extremely significantly reduced (p < .01). In summary, UBA2 can regulate the content of the SUMO-1 protein in mature pig oocytes in vitro, which in turn affects the maturation rate of oocytes, expression of apoptosis genes, cumulus cell viability, and the development of embryos after fertilization.