95 IN VITRO MATURATION AND FERTILIZATION OF OOCYTES FROM OVARIAN TISSUES CRYOPRESERVED AND XENOGRAFTED INTO NUDE MICE

Primordial follicles act as stores of ovarian follicles and are potential sources of oocytes for medical, agricultural, and zoological purposes. Ovarian xenografting seems to be advantageous for maturing the oocytes in primordial follicles (primordial oocytes) and useful for the conservation and reproduction of domestic or endangered animals. We have generated viable embryos from porcine primordial oocytes xenografted into nude mice (Kaneko et al. 2006 Reproduction). Xenografting of ovarian tissues after cryopreservation would be a very powerful tool for this purpose. Recently, Moniruzzaman et al. 2009 Theriogenology) reported that follicles were able to develop to the pre-antral stage in ovarian tissues after cryopreservation and xenografting, but that oocytes were not obtainable from them. In the present study, we vitrified the tissue after different immersion periods in a cryoprotectant, ethylene glycol (EG), and evaluated the possibility of oocyte collection, and also their maturation and fertilization abilities. Ovarian tissue from piglets approximately 20 days old was minced into cubes of about 1.0 to 2.0 mm. After equilibration in 4% EG in IVC-PyrLac (Kikuchi et al. 2002 Biol. Reprod.) as a base solution (BS) for 15 min, they were immersed in vitrification solution (35% EG, 5% polyvinyl pyrrolidone, and 0.3 M trehalose in BS) for 45 s or 7 min (45-s and 7-min immersion groups, respectively), then dropped with about 4 μL of vitrification solution into liquid nitrogen (LN2). After storage in LN2, microdroplets were transferred in warming solution (0.4 M trehalose in BS) at 37°C for 2 min, then consecutively transferred for 2-min periods into 0.2 M, 0.1 M, or 0.05 M trehalose in BS.As described previously (Kaneko et al. 2006 Reproduction), 20 to 30 pieces of tissue were grafted into kidney capsules of ovariectomized nude mice. The host mice were treated with porcine FSH (62.5 U mL-1 in osmotic pomp) for 12 days before assessment of the survival of the ovarian grafts. When antral follicles were evident in the grafts, oocytes were collected using a surgical blade. They were then matured and fertilized in vitro (Kikuchi et al. 2002 Biol. Reprod.). Ovaries containing antral follicles were obtained between 62 and 125 days after grafting from 6 out of 12 mice in the both 45-s and 7-min groups. When a total of 39 and 49 fully grown oocytes, respectively, had been collected from these groups and cultured, the maturation rates calculated on the basis of 1st polar body extrusion were 18% (7/39) and 33% (16/49), respectively. The corresponding rates for sperm-penetrated oocytes were 83% (5/6) and 88% (14/16), respectively. All the oocytes formed male and female pronuclei at 10 h after insemination. The rates in the 2 immersion groups did not differ significantly by chi-square test, with or without Yates’ correction. In conclusion, fully grown porcine oocytes can be collected from primordial follicles that have been cryopreserved and xenografted into nude mice. The period of immersion before vitrification may not affect oocyte maturation or fertilization ability.

378 INVOLVEMENT OF THE SPERM TAIL IN TRIGGERING OOCYTE ACTIVATION IN PIGS

In mammals, repetitive increases of the intracellular Ca2+ level, known as Ca2+ oscillations, are observed in oocytes immediately after sperm-oocyte fusion, which is a prerequisite event for oocyte activation. Previous studies indicate that phospholipase C zeta (PLCζ), a strong candidate sperm factor for triggering Ca2+ oscillations, is localized in the sperm head of several mammalian species. We have reported that the rate of pronucleus formation in oocytes injected with a sperm head is lower than that for oocytes injected with a whole spermatozoon (Nakai et al. 2009 IETS). This has given rise to a hypothesis that not only the sperm head but also the tail play a role in inducing oocyte activation in pigs. In this study, we attempted to detect the localization of PLCζ in the pig sperm tail and also its ability to activate porcine oocytes after injection. To clarify the localization of PLCζ in pig sperm, frozen-thawed ejaculated pig sperm were immunostained using an anti-PLCζ antibody that has been reported previously (Kurokawa et al. 2005). Western blotting was also carried out to examine whether PLCζ (72 kDa) was present in the sperm tail. Sperm tails were detached from the head by sonication and then collected after centrifugation in a Percoll density gradient. We also confirmed whether the sperm tail itself had the ability to trigger oocyte activation using the following 4 injection groups: (1)1 sperm head (Head), (2) 1 sperm tail (Tail), (3) 1 sperm head and 1 tail (Head + Tail), and (4) Sham. The nuclear status of the injected oocyte was evaluated at 10 h after injection. In the present study, we used 3 sperm samples that were prepared from different boars. In pig sperm, the acrosome, tail, and post-acrosomal regions were stained by the PLCζ antibody. The signals in both the post-acrosomal and tail regions disappeared after pretreatment with antigenic peptide, but that in the acrosome region was retained. Furthermore, we confirmed the presence of a band of approximately 72 kDa from the sperm tail and also confirmed its disappearance upon pretreatment with antigenic peptide. The rates of oocytes released from metaphase-II arrest in the Head, Tail, and Head+Tail groups were significantly higher than that in the Sham group (P < 0.05 by ANOVA andTukey test). However, most of the oocytes in the Tail group failed to form pronuclei and showed other meiotic stages (anaphase-II, telophase-II, or metaphase-III). In conclusion, we have shown that PLCζ is expressed in the post-acrosomal and tail region of pig sperm. It is suggested that, in the pig, the sperm tail participates in the triggering of oocyte activation. The authors thankRafaelA. Fissore (Department ofVeterinary and Animal Sciences, University of Massachusetts Amherst) for providing the antigenic peptide for PLCζ. This study was supported in part by JSPS Fellowship (71310042 to M.N.) from the Japanese Society for Promotion of Science (JSPS).

Inhibitory effect of oxytocin on accelerated colonic motility induced by water-avoidance stress in rats

Recent studies have indicated that brain and gut activities are interrelated and exposure to several stressors, such as water-avoidance stress, stimulates the motor function of the gut through corticotropin-releasing factor (CRF)-signalling pathways in the brain. Central oxytocin is known to attenuate stress responses, including CRF expression in the brain. Here, we examined whether central oxytocin attenuated the acceleration of colonic motility induced by water-avoidance stress. A force transducer was attached to the distal colon of male rat, and the colonic motility and faecal pellet output were recorded while the rats were exposed to water-avoidance stress. Intracerebroventricular (i.c.v.) injections of oxytocin (5, 50 and 500 pmol) and the oxytocin receptor antagonist tocinoic acid (25 microg) were administered before exposure to water-avoidance stress, and the effect of oxytocin on colonic motor function was determined. Centrally administered oxytocin inhibited the accelerated colonic motility induced by water-avoidance stress. The effective dose ranged between 5 and 50 pmol on i.c.v. injection. Oxytocin also decreased the number of CRF-positive cells in the paraventricular nucleus and corticosterone release. The inhibitory effect of oxytocin on accelerated colonic motility was blocked by pretreatment with oxytocin receptor antagonist. Furthermore, centrally administered tocinoic acid enhanced the acceleration of colonic motility. These results suggested that endogenous central oxytocin may contribute to the regulation of colonic function and inhibit the brain CRF-signalling pathways targeting the gut, resulting in the inhibition of stress-induced colonic contractions.

Rheodielectric study on shear-induced structural change in the smectic-A phase of 4-n-octyl-4'-cyanobiphenyl (8CB)

Simultaneous measurements of rheological and dielectric properties are made to investigate shear-induced structural change in the smectic-A phase of 8CB (4-n-octyl-4'-cyanobiphenyl). With increasing the shear rate, the fluidity changes from non-Newtonian to Newtonian flow via an unstable flow region, accompanied by a characteristic change in the dielectric permittivity. In the non-Newtonian flow region, a dielectric dispersion, which can be ascribed to an undulation motion of smectic layer, is recognized. On the basis of these results, it is suggested that with increasing the shear rate the undulation changes to a chaotic structure, which is followed by a more simple structure with the layer normal along the neutral axis, and that these structural changes are responsible for the fluidity change.

Association study of TRAF1-C5 polymorphisms with susceptibility to rheumatoid arthritis and systemic lupus erythematosus in Japanese

OBJECTIVE

The primary aim of this study was to investigate the association of polymorphisms of TRAF1-C5, a newly identified rheumatoid arthritis (RA) risk locus in Caucasians, with susceptibility to RA and systemic lupus erythematosus (SLE) in Japanese populations. Gene expression levels of TRAF1 and C5 to assess the functional significance of genotypes were also analysed.

METHODS

A multicentre association study consisting of 4 RA case-control series (4397 cases and 2857 controls) and 3 SLE case-control series (591 cases and 2199 shared controls) was conducted. Genotyping was performed using TaqMan genotyping assay for two single nucleotide polymorphisms (SNPs) that showed the best evidence of association in the previous Caucasian studies. Quantifications of TRAF1 and C5 expression were performed with TaqMan expression assay.

RESULTS

Significant differences in allele frequency for both SNPs were observed between RA and control subjects (combined odds ratio = 1.09), while no significant difference was detected between patients with SLE and controls. Interestingly, alleles rs3761847 A and rs10818488 G had increased the risk for RA in the present study, while they decreased the risk in the original studies. A significant difference was found between risk allele carriers and non-carriers of rs10818488 for the expression level of TRAF1 in phorbol myristate acetate-stimulated lymphoblastoid cell lines (p = 0.04).

CONCLUSION

Association of TRAF1-C5 locus with RA susceptibility was detected in the Japanese populations with modest magnitude, while no significant association was observed for SLE. Significant positive effect of genotype on the expression of TRAF1 might support the genetic association between TRAF1 and RA.

Changes in the gene expression of peripheral blood mononuclear cells during the menstrual cycle of females is associated with a gender bias in the incidence of systemic lupus erythematosus

OBJECTIVE

The incidence of systemic lupus erythematosus (SLE) is far higher in females than in males and the onset and/or disease activity is influenced by pregnancy and the menstrual cycle. Sex hormones seem to influence the pathogenesis of SLE, therefore, changes in gene expression in peripheral blood mononuclear cells (PBMC) were examined during the menstrual cycle in females, under the comparison of gene expression of patients with SLE.

METHODS

The detection and a quantitative analysis of the gene expression was performed by DNA microarray or real-time quantitative polymerase chain reaction (RQ-PCR) method.

RESULTS

There were thirteen known genes which showed significant quantitative changes during the menstrual cycles of females, but not in males. Among these genes, statistical quantitative differences between normal controls and SLE patients were observed in six genes.

CONCLUSION

Based on these findings, certain genes (such as the tumor necrosis factor receptor superfamily, member 14; TNFRSF14, and signal regulatory protein, gamma; SIRPG) appear to contribute to gender difference of SLE.

Nuclear replacement of in vitro-matured porcine oocytes by a serial centrifugation and fusion method

The objective of the present study was to establish a method for nuclear replacement in metaphase-II (M-II) stage porcine oocytes. Karyoplasts containing M-II chromosomes (K) and cytoplasts without chromosomes (C) were produced from in vitro-matured oocytes by a serial centrifugation method. The oocytes were then reconstructed by fusion of one karyoplast with 1, 2, 3 or 4 cytoplasts (K + 1C, K + 2C, K + 3C and K + 4C, respectively). Reconstructed oocytes, karyoplasts without fusion of any cytoplast (K) and zona-free M-II oocytes (control) were used for experiments. The rates of female pronucleus formation after parthenogenetic activation in all groups of reconstructed oocytes (58.2-77.4%) were not different from those of the K and control groups (58.2% and 66.0%, respectively). In vitro fertilization was carried out to assay the fertilization ability and subsequent embryonic development of the reconstructed oocytes. The cytoplast : karyoplast ratio did not affect the fertilization status (penetration and male pronuclear formation rates) of the oocytes. A significantly high monospermy rate was found in K oocytes (p < 0.05, 61.6%) compared with the other groups (18.2-32.8%). Blastocyst formation rates increased significantly as the number of the cytoplasts fused with karyoplasts increased (p < 0.05, 0.0-15.3%). The blastocyst rate in the K + 4C group (15.3%) was comparable with that of the control (17.8%). Total cell numbers in both the K + 3C and K + 4C groups (16.0 and 15.3 cells, respectively) were comparable with that of the control (26.2 cells). Our results demonstrate that a serial centrifugation and fusion (Centri-Fusion) is an effective method for producing M-II chromosome transferred oocytes with normal fertilization ability and in vitro development. It is suggested that the number of cytoplasts fused with a karyoplast plays a critical role in embryonic development.

Generation of porcine diploid blastocysts after injection of spermatozoa grown in nude mice

It is anticipated that the utilization of spermatogonia through testicular xenografting will open new avenues for the conservation of male gametes. With the aim of establishing this new technique for genetic preservation of pigs, we used it in combination with intracytoplasmic sperm injection (ICSI). Testicular tissues derived from neonatal piglets, which contained seminiferous cords consisting of only gonocytes/spermatogonia, were transplanted under the back skin of castrated nude mice. Between 125 and 192 d after xenografting, sperm (morphologically similar to epididymal sperm) were recovered from 41 of the 65 host mice (63.1%). Testicular spermatozoa from adult boars were used as a positive control. A single spermatozoon was injected into an in vitro matured porcine oocyte, and the oocytes were electro-stimulated and cultured (graft-ICSI and testis-ICSI, respectively). Blastocyst rates in both ICSI groups (24.9% and 37.4%, respectively) were higher (P<0.05) than those without the injection procedure (parthenogenetic; 12.7%) and after injection of a small amount of injection buffer (sham; 13.0%). Rates of diploid blastocysts in both graft-ICSI and testis-ICSI groups (48.9% and 60.6%) were higher (P<0.05) than those in the parthenogenetic and sham groups (13.5% and 28.0%). Therefore, we demonstrated that porcine oocytes injected with xenogeneic sperm have in vitro developmental ability to the blastocyst stage.

270 PRETREATMENTS OF PORCINE SPERM BEFORE INTRACYTOPLASMIC SPERM INJECTION AFFECT QUANTITY OF PLCZETA;

In pigs, the intracytoplasmic sperm injection (ICSI) procedure alone is insufficient to induce oocyte activation for embryonic development. Artificial activation can be accomplished, such as by electrical pulse-enhanced in vitro development to the blastocyst stage (Nakai et al. 2006). It is well known that the sperm factor (phospholipase Cζ; PLCζ) in spermatozoa, which triggers oocyte activation, is diffused into ooplasm when sperm fuse with oocytes. Our previous study showed that the activation rate of porcine oocytes injected with one sonicated sperm head was significantly lower than that of oocytes injected with a whole spermatozoon or with 3 sonicated sperm heads (Nakai et al. IETS 2007). These results suggest that the sonication treatment per se may affect the quantity of PLCζ in sperm. Furthermore, various pretreatments of sperm besides sonication have been conducted (e.g. removal of the sperm membrane) to increase the efficacy of ICSI. In this study, we investigated the effect of pretreatments (sonication, Triton X-100, and repeated cycles of freezing–thawing without cryoprotectant) on the quantity of PLCζ in porcine sperm. Cryopreserved-thawed boar-ejaculated sperm were used for 3 experimental groups: (1) sperm were sonicated for 10 s in pig-fertilization medium (pig-FM; Suzuki et al. 2002; Soni group), (2) freezing–thawing was repeated 3 times in pig-FM without cryoprotectant (3-F/T group), or (3) sperm were incubated in pig-FM supplemented with 0.1 or 1% Triton X-100 at 37°C for 1 min (0.1 and 1% Triton X-100 groups, respectively). Cryopreserved-thawed whole sperm without any treatment was used as a control. Results from staining with fluorescein diacetate and propidium iodide showed that almost all sperm were propidium iodide positive (dead sperm) immediately after the each treatment. In the control group, approximately 40% of sperm were fluorescein diacetate positive (live sperm) after thawing. The presence of PLCζ (72 kDa) was examined by Western blotting using the antibody against the N-terminal 19-mer sequence of porcine PLCζ (Kurokawa et al. 2005). A band corresponding to porcine PLCζ was not detected in any treatment group in any culture period (from 0 to 135 min). In contrast, PLCζ was detected in the control group and in all culture periods. These results strongly suggest that PLCζ in porcine sperm was lost immediately after the pretreatments, such as by sonication, incubation with 0.1 or 1% Triton X-100, and repeated cycles of freezing–thawing. The decrease in PLCζ protein by pretreatment may be one of the causes of incomplete activation of oocytes in porcine ICSI. This work was supported by a Grant-in-Aid for JSPS Fellows.

Selected aspects of advanced porcine reproductive technology

In vitro fertilization (IVF) of in vitro matured (IVM) oocytes in pigs has become the most popular method of studying gametogenesis and embryogenesis in this species. Furthermore, because of recent advances in in vitro culture (IVC) of IVM-IVF embryos, in vitro production (IVP) of embryos now enables us to generate viable embryos as successfully as for in vivo-derived embryos and with less cost and in less time. These technologies contribute not only to developments in reproductive physiology and agriculture but also to the conservation of porcine genetic resources and the production of cloned or genetically modified pigs. However, in IVP, there still remains the problem of abnormal ploidy, which is caused by performing procedures under non-physiological conditions. In recent years, unique technologies such as intracytoplasmic sperm injection (ICSI) or xenografting of gonadal tissue into immunodeficient experimental animals have been developed to help conserve gamete resources. These technologies combined with IVP are expected to be useful for the conservation of gametes from important genetic resources. Here, we discuss the developmental ability and normality of porcine IVP embryos and also the utilization of ICSI and xenografting in advancing biotechnology in pigs.