A new alternative method for superovulation using passive immunization against inhibin in adult rats

Superovulation with an anti-inhibin monoclonal antibody improves the reproductive performance of rat strains by increasing the pregnancy rate and the litter size

Rats are multiparous rodents that have been used extensively in research; however, the low reproductive performance of some rat strains hampers the broader use of rats as a biomedical model. In this study, the possibility of increasing the litter size after natural mating in rats through superovulation using an anti-inhibin monoclonal antibody (AIMA) was examined. In outbred Wistar rats, AIMA increased the number of ovulated oocytes by 1.3-fold. AIMA did not affect fertilization and subsequent embryonic development, resulting in a 1.4-fold increase in litter size and a high pregnancy rate (86%). In contrast, conventional superovulation by eCG/hCG administration decreased the pregnancy rate to 6-40% and did not increase the litter size. In inbred Brown Norway rats, AIMA increased the litter size by 1.2-fold, and the pregnancy rate increased more than twice (86% versus 38% in controls). AIMA also increased the litter size by 1.5-fold in inbred Tokai High Avoiders and Fischer 344 rats. AIMA increased the efficiency of offspring production by 1.5-, 2.7-, 1.4-, and 1.4-fold, respectively, in the four rat strains. Thus, AIMA may consistently improve the reproductive performance through natural mating in rats, which could promote the use of AIMA in biomedical research.

A combined treatment with progesterone, anti-inhibin serum, and equine chorionic gonadotropin improves number of ovulated oocytes in young C57BL/6J mice

Superovulation procedures are routinely and widely used in mouse reproductive technology. Previous studies have shown that a large number of oocytes can be obtained from adult mice (> 10 weeks old) using a combined treatment with progesterone (P4) and anti-inhibin serum (AIS). However, these effects have not been fully investigated in young (4 weeks) C57BL/6J mice. Here, we found that a modified superovulation protocol (combined treatment with P4, AIS, eCG (equine chorionic gonadotropin), and hCG (human chorionic gonadotropin); P4D2-Ae-h) improved the number of oocytes compared to the control (eCG and hCG) (39.7 vs. 21.3 oocytes/mouse). After in vitro fertilization, pronuclear formation rates were 69.3% (P4D2-Ae-h group) and 66.2% (control group). After embryo transfer, 46.4% (116/250) of the embryos in the P4D2-Ae-h group successfully developed to term, which was comparable to the control group (42.9%; 123/287 embryos). In conclusion, our protocol (P4D2-Ae-h) was effective for superovulation in young C57BL/6J mice.

Use of anti-inhibin monoclonal antibody for increasing the litter size of mouse strains and its application to i-GONAD

The litter size of mouse strains is determined by the number of oocytes naturally ovulated. Many attempts have been made to increase litter sizes by conventional superovulation regimens (e.g., using equine or human gonadotropins, eCG/hCG but had limited success because of unexpected decreases in the numbers of embryos surviving to term. Here, we examined whether rat-derived anti-inhibin monoclonal antibodies (AIMAs) could be used for this purpose. When C57BL/6 female mice were treated with an AIMA and mated, the number of healthy offspring per mouse increased by 1.4-fold (11.9 vs. 8.6 in controls). By contrast, treatment with eCG/hCG or anti-inhibin serum resulted in fewer offspring than in nontreated controls. The overall efficiency of production based on all females treated (including nonpregnant ones) was improved 2.4 times with AIMA compared with nontreated controls. The AIMA treatment was also effective in ICR mice, increasing the litter size from 15.3 to 21.2 pups. We then applied this technique to an in vivo genome-editing method (improved genome-editing via oviductal nucleic acid delivery, i-GONAD) to produce C57BL/6 mice deficient for tyrosinase. The mean litter size following i-GONAD increased from 4.8 to 7.3 after the AIMA treatment and genetic modifications were confirmed in 80/88 (91%) of the offspring. Thus, AIMA treatment is a promising method for increasing the litter size of mice and may be applied for the easy proliferation of mouse colonies as well as in vivo genetic manipulation, especially when the mouse strains are sensitive to handling.

Morphometric, subcellular, in vitro fertilisation and embryonic developmental assessment of mouse oocytes produced by anti-inhibin serum or pregnant mare serum gonadotrophin superovulation

This study compared the morphometric, subcellular characteristics, in vitro fertilisation (IVF) and embryonic developmental potential of metaphase II (MII) mouse oocytes obtained from females superovulated with either anti-inhibin serum-human chorionic gonadotrophin (AIS-hCG) or pregnant mare serum gonadotrophin (PMSG)-hCG. The oocyte's quantity, quality, zona pellucida (ZP) thickness, perivitelline space (PVS), diameter, microtubules, F-actin, cortical granules (CGs) and mitochondrial distribution were determined. Superovulation using AIS-hCG resulted in a higher numbers of oocyte/donor compared with PMSG-hCG (P=0.002). There was no difference in morphologically normal and abnormal oocytes between AIS-hCG and PMSG-hCG (P=0.425 and P=0.194, respectively). The morphometric measurements showed no difference in oocyte diameter between AIS-hCG and PMSG-hCG (P=0.289). However, the thickness of the ZP of oocytes from AIS-hCG females was decreased compared with PMSG-hCG (P<0.001). The PVS of oocytes from the AIS-hCG was larger than with PMSG-hCG (P<0.001). The microtubules of oocytes from both AIS-hCG and PMSG-hCG were normal, although there was an increased fluorescence intensity in the AIS-hCG oocytes (P<0.001). The F-actin and CGs distribution in oocytes from both AIS-hCG and PMSG-hCG were similar (P=0.330 and P=0.13, respectively). Although the oocytes from PMSG-hCG females had homogenously distributed mitochondria, AIS-hCG oocytes showed more peripheral distribution with no differences in fluorescence intensity (P=0.137). The blastocyst development rates after IVF with fresh sperm showed no difference between AIS-hCG and PMSG-hCG (P=0.235). These data suggested that AIS-hCG superovulation produces high numbers of morphologically normal oocytes that also possess normal subcellular structures, good morphological characteristics and had high invitro embryonic developmental potential.

Improving ovulation in gilts using anti-inhibin serum treatment combined with fixed-time artificial insemination

For successful batch farrowing, porcine oestrus and ovulation must be synchronized using fixed-time artificial insemination (FTAI). However, exogenous gonadotropins, which are currently used in FTAI, negatively affect gilt ovulation. Here, we aimed to improve sexually mature gilt superovulation efficiency using passive immunization against inhibin during FTAI. Altrenogest-treated gilts were challenged with 10 ml anti-inhibin serum (AIS group, n = 6), 1,000 IU pregnant mare serum gonadotropin (PMSG group, n = 6), or 10 ml goat serum (control group, n = 6). Gilts in the AIS and PMSG groups were inseminated according to the FTAI protocol, and gilts in the control group were inseminated during natural oestrus. When PMSG was replaced by AIS during FTAI of gilts, ovulation rate and embryos recovered were significantly greater in the AIS group as compared to the other two groups (p < .05). Especially the average number of 6-8-cell embryos in the AIS group was significantly higher than that in the PMSG group (p < .01). Moreover, the blastocyst number in the AIS group was significantly higher than that in the PMSG group and the control group (p < .05). But there was no significant difference in the blastocyst number between the PMSG group and the control group (p > .05). Besides, plasma levels of estradiol-β (E2) and progesterone (P4) were significantly greater in the AIS group as compared to the other two groups on Day 23 and D 27, respectively (p < .01). In summary, we devised an improved high-yield FTAI protocol for sexually mature gilts using AIS; this protocol had a greater superovulation efficiency than the FTAI using PMSG.

Development of assisted reproductive technologies in small animal species for their efficient preservation and production

Assisted reproductive technologies (ARTs) are widely used in the animal industry, human clinics, and for basic research. In small laboratory animal species such as mice, ARTs are essential for the production of animals for experiments, the preservation of genetic resources, and for the generation of new strains of genetically modified animals. The RIKEN BioResource Research Center (BRC) is one of the largest repositories of such animal bioresources, and maintains approximately 9,500 strains of mice with a variety of genetic backgrounds. We have sought to devise ARTs specific to the reproductive and physiological characteristics of each strain. Such ARTs include superovulation, in vitro fertilization (IVF), the cryopreservation of embryos and spermatozoa, transportation of cryopreserved materials and embryo transfer (ET). Of these, superovulation likely has the most influence on animal production because it determines the quantity of starting material for other ARTs. Superovulation using anti-inhibin serum combined with estrous synchronization has resulted in approximately a three-fold increase in production efficiency with IVF-ET in the C57BL/6J strain. Wild-derived strains are important as genetically diverse resources for murine rodents (Genus Mus), and many are unique to the BRC. We have also successfully developed ARTs for more than 50 wild-derived strains, which have been cryopreserved for future use. Our work to improve and develop ARTs for mice and other small laboratory species will contribute to the cost-effectiveness of routine operations at repository centers, and to the provision of high quality animals for research use.

Cloning expression and immunogenicity analysis of inhibin gene in Ye Mule Aries sheep

Background

Ye Mule Aries sheep is one of the most important sheep breeds in Xinjiang, China. This breed is well adapted to harsh environmental conditions and displays strong disease resistance, fast growth, and high cold tolerance. To analyze the clonal expression and immunogenicity of the Ye Mule Aries sheep inhibin gene, total RNA was extracted from sheep ovarian tissue and used as a template to generate a eukaryotic expression vector and study inhibin immunogenicity.

Methods

Primers were designed to amplify the inhibin A gene via polymerase chain reaction and the amplified product was cloned between the ScalI and EcoRI restriction sites of the expression vector pEGFP-N1 to construct a recombinant plasmid, pEGFP-INHα. Following the validation of successful cloning, the pEGFP-INHα plasmid was transfected into BHK cells to verify expression in eukaryotes and subsequently utilized as an antigen in rabbits. Rabbits were tested for anti-inhibin antibodies and serum follicle-stimulating hormone (FSH) concentrations.

Results

The analysis of the INHα gene sequence revealed that INHα is 1109 bp long and is translated to an approximately 40 KDa protein. Bioinformatics approach indicated that the INHα gene is highly conserved between organisms. Immunization with the eukaryotic expression vector, pEGFP-INHα, which expresses the INHα gene elicited immune response and generatigeneration on of anti-INHα antibody. The antibody had a significant regulatory effect on the serum concentration of FSH in rabbits and led to higher levels of FSH, indicating increased ovary function.

Conclusions

The present work resulted in a successful construction of eukaryotic expression plasmid pEGFP-INHα and verified the immunogenicity of this highly conserved protein. Further, the expression of pEGFP-INHα was shown to have a significant impact on the secretion of FSH, indicating a potential regulatory role in ovarian function. In conclusion, our current findings can serve as a working model for studying the effect of INHα on the breeding performance of Ye Mule Aries sheep, providing a novel strategy to improve their reproduction rates.

Efficient derivation of knock-out and knock-in rats using embryos obtained by in vitro fertilization

Rats are effective model animals and have contributed to the development of human medicine and basic research. However, the application of reproductive engineering techniques to rats is not as advanced compared with mice, and genome editing in rats has not been achieved using embryos obtained by in vitro fertilization (IVF). In this study, we conducted superovulation, IVF, and knock out and knock in using IVF rat embryos. We found that superovulation effectively occurred in the synchronized oestrus cycle and with anti-inhibin antiserum treatment in immature rats, including the Brown Norway rat, which is a very difficult rat strain to superovulate. Next, we collected superovulated oocytes under anaesthesia, and offspring derived from IVF embryos were obtained from all of the rat strains that we examined. When the tyrosinase gene was targeted by electroporation in these embryos, both alleles were disrupted with 100% efficiency. Furthermore, we conducted long DNA fragment knock in using adeno-associated virus and found that the knock-in litter was obtained with high efficiency (33.3–47.4%). Thus, in this study, we developed methods to allow the simple and efficient production of model rats.

High-Yield Superovulation in Adult Mice by Anti-Inhibin Serum Treatment Combined with Estrous Cycle Synchronization

Producing many mature oocytes is of great importance for assisted reproductive technologies. In mice, superovulation by consecutive injections of equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) has been the gold standard for oocyte collection. However, the yield of mature oocytes by this regimen can fluctuate according to the stage of the estrous cycle, strain, and age. Therefore, our objective was to develop a high-yield superovulation protocol to collect higher numbers of oocytes from adult female mice of different strains and ages. First, we aimed to synchronize the estrous cycle using C57BL/6 (B6) female mice. Most (93%) were synchronized to metestrus after two daily injections of progesterone. Second, we found that with the injection of anti-inhibin serum (AIS) instead of eCG, the mean number of ovulated oocytes almost doubled (21 vs. 41 per mouse). Third, by combining estrous cycle synchronization with two AIS injections, we obtained 62 oocytes per mouse, about three times that with the eCG-hCG protocol. Importantly, this approach increased the proportion of mice that ovulated >25 oocytes from about 40% (eCG-hCG) to 90%. The same protocol was also effective in other inbred (BALB/cA), outbred (ICR), and hybrid (B6D2F1) strains. In addition, B6 female mice aged over 1 yr ovulated 1.8-fold more oocytes by this protocol. Thus, estrous cycle synchronization followed by AIS-hCG yielded a broadly applicable, highly efficient superovulation. This protocol should promote the effective use of invaluable female mouse strains and decrease the numbers of animals euthanized.

Molecular mechanisms of enhancing porcine granulosa cell proliferation and function by treatment in vitro with anti-inhibin alpha subunit antibody

BACKGROUND

This study was conducted to clarify the effect of the inhibiting action of inhibin on porcine granulosa cell proliferation and function, and to investigate the underlying intracellular regulatory molecular mechanisms.

METHODS

Porcine granulosa cells were cultured in vitro, and were treated with an anti-inhibin alpha subunit antibody, with or without co-treatment of follicle-stimulating hormone (FSH) in the culture medium.

RESULTS

Treatment with anti-inhibin alpha subunit antibody led to a significant increase in estradiol (E2) secretion and cell proliferation. Anti-inhibin alpha subunit antibody worked synergistically with FSH at low concentrations (25 microg/mL) to stimulate E2 secretion, but attenuated FSH action at high concentrations (50 microg/mL). Immunoneutralization of inhibin bioactivity increased FOXL2, Smad3, and PKA phosphorylation, and mRNA expression of the transcription factors CEBP and c-FOS. The expression of genes encoding gonadotropin receptors, FSHR and LHR, and of those involved in steroidogenesis, as well as IGFs and IGFBPs, the cell cycle progression factors cyclinD1 and cyclinD2, and the anti-apoptosis and anti-atresia factors Bcl2, TIMP, and ADAMTS were upregulated following anti-inhibin alpha-subunit treatment. Treatment with anti-inhibin alpha subunit down regulated expression of the pro-apoptotic gene encoding caspase3. Although expression of the pro-angiogenesis genes FN1, FGF2, and VEGF was upregulated, expression of the angiogenesis-inhibiting factor THBS1 was downregulated following anti-inhibin alpha subunit treatment.

CONCLUSIONS

These results suggest that immunoneutralization of inhibin bioactivity, through augmentation of the activin and gonadotropin receptor signaling pathways and regulation of gene expression, permits the development of healthy and viable granulosa cells. These molecular mechanisms help to explain the enhanced ovarian follicular development observed following inhibin immunization in animal models.

Fertilizability of Superovulated Eggs by Estrous Stage-independent PMSG/hCG Treatment in Adult Wistar-Imamichi Rats

We investigated the fertilization and developmental ability of superovulated eggs obtained from adult Wistar-Imamichi (WI) rats, by using pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) treatment. Female WI rats, 11-13 weeks of age, were divided into four groups by estrous stage (metestrus [ME], diestrus [DE], proestrus [PE], or estrus [E]). PMSG (150 IU/kg) and hCG (75 IU/kg) were injected at an interval of 48 or 55 h and the female rats were mated with mature male rats. The ovulated eggs were collected 20, 24, and 27 h after hCG injection. Regardless of the estrous stage at the time of PMSG injection, the treated rats mated and ovulated similar to the untreated spontaneously ovulated rats (S group). Although the proportion of fertilized eggs in the E- and PE-treated groups was less than the S group 20 h after hCG injection, the proportion was not different among all treated and S groups 24 h after hCG injection. The proportion of fertilized eggs using in vitro fertilization and the proportion of offspring obtained from 2-cell stage embryo transfer did not differ among the treated and S groups. In comparison with PMSG/hCG-treated immature rats, mating and ovulation rate of adult rats were significantly higher. The proportion of fertilized eggs obtained from mated rats did not differ between immature and adult rats. These results demonstrate that adult WI rats are good egg donors for reproductive biotechnological studies using unfertilized or fertilized eggs.

Endocrine disruptive actions of inhaled benzo(a)pyrene on ovarian function and fetal survival in fisher F-344 adult rats

This study evaluated the effect of inhaled BaP on female reproductive function. Rats were exposed to 50, or 75 or 100 μg BaP/m(3), 4 h a day for 14 days via inhalation. Plasma E(2), P(4), LH and FSH concentrations were determined. Ovarian BaP metabolism and aryl hydrocarbon hydrolase (AHH) activity at proestrus were determined and fertility evaluations were conducted. Ovulation rate and number of pups/litter were reduced in rats exposed to 100 μg BaP/m(3) compared with other treatment and control groups. Plasma concentrations of E(2), and LH were significantly reduced at proestrus in BaP-exposed versus those of controls whereas those of P(4) were significantly reduced at diestrus I. The activity of AHH in ovarian and liver tissues and concentrations of BaP 7,8-diol and BaP 3,6-dione metabolites increased in an exposure concentration-dependent manner. These data suggest that exposure of rats to BaP prior to mating contributes to reduced ovarian function and fetal survival.

Efficient production of offspring from Japanese wild-derived strains of mice (Mus musculus molossinus) by improved assisted reproductive technologies

Because the genetic diversity of the laboratory mouse (Mus musculus) is very limited, wild-derived strains from this genus could provide invaluable experimental models for studies of mouse genetics and epigenetics such as quantitative trait locus analysis. However, such strains generally show poor reproductive performance under conventional husbandry conditions, so their use for large-scale analyses has been limited. This study was undertaken to devise assisted reproductive technologies (ARTs) for the efficient production of offspring in two wild-derived strains, MSM/Ms and JF1/Ms (Mus musculus molossinus). First, as females of these strains are poor responders to equine chorionic gonadotropin (eCG) stimulation, we examined the efficiency of superovulation by injecting anti-inhibin serum followed by human chorionic gonadotropin (hCG). Approximately four to six times more oocytes were ovulated than with eCG-hCG treatment in both strains, reaching ∼25-30 oocytes per female. Consequently, the procedures for in vitro fertilization using these superovulated oocytes and cryopreservation of embryos and spermatozoa could be optimized for both of the wild-derived strains. However, MSM/Ms embryos but not JF1/Ms embryos failed to develop to term after embryo transfer because of intrauterine death at mid to late gestation. We were able to overcome this obstacle by cotransfer of these embryos with those from laboratory strains combined with treatment of recipient females with an immunosuppressant (cyclosporin A). Thus, a series of ARTs essential for efficient production and preservation of the wild-derived strains were successfully devised. These technologies will facilitate systematic studies of mouse genetics and epigenetics using a wider range of genetic diversity than currently available in the genus Mus.

Effect of a DNA vaccine harboring two copies of inhibin α (1-32) fragments on immune response, hormone concentrations and reproductive performance in rats

The objective was to investigate the effects of a novel DNA vaccine (pcISI) harboring two copies of inhibin α (1-32) fragments on immune response, hormone concentrations and reproductive performance in rats. Female Wistar rats (n=18 per group) were immunized (twice, 4 wk apart) with 10, 50, or 100 μg (T1, T2 and T3, respectively), of the pcISI plasmid. At 4 wk after the second immunization, plasma antibody titers were higher (P<0.05) in T3 than in either T1 or T2 (0.341±0.123, 0.236±0.068, and 0.251±0.077, respectively, mean±SD). Concurrrently, plasma concentrations of FSH and estradiol were highest (P<0.05) in T3, and were higher (P<0.05) in T1 and T2 than in control groups. For antibody-positive rats, there was a correlation (P<0.01) between antibody titer and FSH concentrations after two pcISI immunizations. The number of mature follicles in the T3 group (46.00±4.65) was higher (P<0.05) than in two control groups (29.25±3.72 and 27.92±3.48), and also higher (P<0.05) than in T1 and T2 (37.17±4.99 and 38.75±7.09). Antibody-positive rats had more mature ovarian follicles than negative rats (46.75±4.23 vs. 35.60±3.38, P<0.05). Moreover, litter size and number of placentas were increased (P<0.05) in the pcISI immunization groups, except for the T1 group, compared to the control groups. In conclusion, the pcISI DNA vaccine successfully induced a humoral immune response, improved reproductive hormone concentrations, stimulated follicular development, and increased number of placentas and litter size. Furthermore, 100 μg yielded the best immune response.

Human follicular fluid from superovulated women inhibits progesterone receptor-dependent gonadotropin-releasing hormone self-priming in an estrous cycle-dependent manner in the rat

These experiments investigated the involvement of gonadotrope progesterone receptor (PR) in the effects of the putative gonadotropin surge-attenuating factor (GnSAF) on gonadotropin (LH and FSH) secretion. Human follicular fluids (hFF) used in this study were aspirated from follicles in gonadotropin-treated women for in vitro fertilization. Samples were subjected to two-fold charcoal extraction of steroid hormones and two-fold inhibin immunoprecipitation. Gonadotropin secretion parameters were assessed by specific radioimmunoassays. In the first experiment, the effects of hFF on both basal and GnRH-stimulated gonadotropin secretion and GnRH self-priming were studied in incubated hemipituitaries from rats on each day of the 4-day estrous cycle. hFF inhibited only GnRH self-priming in pituitaries from rats in diestrus. In the second experiment, immunohistochemical PR expression and action were evaluated in pituitaries from rats in diestrus. PR-positive (PR10A9 antibody) gonadotropes were detected (4-5/field 40x), and antiprogestins added to the incubation media blocked the ligand-independent (GnRH) activation of PR effects on GnRH selfpriming. Finally, the third experiment evaluated the effects of hFF on P-induced potentiation of GnRH-stimulated LH secretion. GnSAF bioactivity, as evidenced by inhibition of PR-induced potentiation of GnRH-stimulated LH secretion, was found in diestrous pituitaries incubated with hFF. The results indicate that GnSAF attenuated GnRH-dependent LH secretion in diestrus through the inhibition of PR-dependent GnRH self-priming.

Superovulatory response, oocyte spontaneous activation, and embryo development in WMN/Nrs inbred rats

WMN/Nrs inbred rats have been widely used in radiation biology for years. However, their reproductive profile has never been examined. We examined various reproductive characteristics of WMN/Nrs inbred rats such as superovulatory response, oocytes spontaneous activation (OSA), and embryo development in vitro and in vivo. Superovulation was induced in 3- to 9-week-old females by injection of 150 IU/kg PMSG and 150 IU/Kg hCG by 48 h apart. Only 8- and 9-week-old animals superovulated averaging 31.4 and 43.9 oocytes, respectively, and superovulation did not depend on estrous cycle. Animals 3-7 weeks of age did not superovulate. Because Wistar strains have been known to show a high incidence of OSA, factors expected to affect OSA in WMN/Nrs, including the time interval of various steps from euthanasia to oocyte recovery, incubation media, estrous cycle, and anesthetic treatments, were examined. The time from animal euthanasia to oviduct excision was the only factor shown to affect OSA. We also compared in vitro and in vivo embryo developmental competence between embryos obtained by natural ovulation and superovulation. Although percent in vitro development of 2-cell embryos to blastocysts was similar for embryos obtained by natural ovulation (63.7%) and superovulation (69.7%), fetus development after oviductal transfer of 2-cell embryos was significantly lower in embryos obtained by superovulation than in those obtained by natural ovulation (60.2% vs. 87.5%, P=0.02). Our results provide important normative data regarding future applications of rat assisted reproductive technologies (ARTs) such as in vitro fertilization and cryopreservation in WMN/Nrs strain and may be applicable to other strains of laboratory rats.

Ovarian stimulation with FSH reduces phosphorylation of gonadotrope progesterone receptor and LH secretion in the rat

Administration of human FSH (hFSH) to cyclic rats during the dioestrous phase attenuates progesterone receptor (PR)-dependent events of the preovulatory LH surge in pro-oestrus. The increased bioactivity of the putative ovarian gonadotropin surge inhibiting/attenuating factor induced by hFSH treatment is not associated with a decrease in PR protein expression, and the possibility of its association at a PR posttranslational effect has been raised. The present experiments aimed to analyse PR phosphorylation status in the gonadotrope of rats with impaired LH secretion induced byin vivohFSH injection. Two experimental approaches were used. First, incubated pro-oestrous pituitaries from hFSH-injected cycling and oestrogen-treated ovariectomized (OVX) rats were used to analyze the effect of calyculin, an inhibitor of intracellular phosphatases, on PR-dependent LH release, which was measured in the incubation medium by RIA. Second, pituitaries taken from hFSH-injected intact cycling and OVX rats and later incubated with P or GNRH1 were used to assess the phosphorylation rate of gonadotrope. The latter was analysed in formalin-fixed, paraffin-embedded tissue sections by immunohistochemistry using a MAB that recognizes the phosphorylated (p) form of PR at Ser294. Calyculin reduced the ovary-mediated inhibition of hFSH in GNRH1-stimulated LH secretion. In addition, the immunohistochemical expression of pSer294 PR was significantly reduced after ovarian stimulation with hFSH in pituitaries from pro-oestrous rats incubated with P or GNRH1. Altogether, these results suggested that the ovarian-dependent inhibitory effect of FSH injection on the preovulatory LH secretion in the rat may involve an increase in dephosphorylation of PR.

Enhancing embryo yield in superovulated holstein heifers by immunization against inhibin

Eight heifers, aged 16-17 months and showing normal oestrous cycles, were immunized against a recombinant porcine inhibin alpha subunit immunogen, together with another 10 heifers of the same age as controls and treated with placebo immunogen. Primary (1 mg immunogen) and two booster (0.5 mg immunogen each) immunizations were administered at 28-day intervals. Ten days after the second booster immunization, both groups of heifers underwent a superovulation treatment. Each animal was given an intravaginal progesterone releasing sponge, which was withdrawn 7 days following an i.m. injection of 0.5 mg cloprostenol. Heifers were treated with FSH for 4 days and artificially inseminated after oestrus occurred. The embryos were flushed and evaluated 7 days after insemination. Immunization significantly (p < 0.01) increased blood antibody titres against recombinant porcine inhibin alpha subunit, from pre-immunizaion and control values of approximately 0.06 of ELISA 450 nm reading to 0.6 to 0.7 after two or three immunizations. The immunized heifers produced on average 15.8 +/- 2.8 embryos, significantly (p < 0.05) higher than the yield of 8.3 +/- 1.5 in the controls. The number of transferable embryos were non-significantly higher in immunized than in control heifers (9.6 +/- 3.1 vs 5.8 +/- 1.6, p > 0.05). The peak plasma oestradiol concentrations were significantly higher in immunized than in control heifers, both immediately after FSH treatment and 20 days thereafter. Plasma P4 concentrations after superovulation were in the range of 20 ng / ml in the immunized heifers, significantly (p < 0.05) higher than the values approximately 15 ng / ml in control heifers. These results indicated that prior immunization against inhibin alpha subunit stimulated production of antibodies against inhibin, which enhanced follicular developmental response to superovulation and lead to higher yield of total and transferable embryos. Therefore immunization combined with the conventional superovulatory gonadotrophin treatment, can be a simple and efficient method to produce low cost bovine embryos.

Physiological roles of inhibin in regulation of FSH secretion and follicular development during early pregnancy in goats

The aim of the current study was to clarify the physiological role of inhibin in controlling FSH secretion and follicular development during the early pregnancy in goats. Eight goats investigated sonographically on Days 19-21 (Day 0=day of mating) for pregnancy were assigned into control (n=3) and treated (n=5) groups. The ovaries of all animals were daily scanned with ultrasound for follicles 2mm or more in diameter from 1 day before to 5 days after treatment. On Day 25 postbreeding; animals received either 10 ml, of normal goat serum or antiserum against [Tyr (30)]-inhibin alpha (1-30). Jugular blood samples were collected every 6 h starting 24 h before and until 120 h after treatment. The plasma concentration of FSH increased at 6 h and remained at significantly high levels until 120 h in treated vs. control group. The plasma concentrations of estradiol showed a marked increased at 66 h, with peak levels at 120 h after treatment of antiserum. The basal concentrations of LH and the pattern of plasma concentrations of progesterone were not significantly different between the two groups. The number of medium size (3.5-5.0 mm) follicles increased considerably from Day 2, whereas small (3.5 mm or less) and large (5 mm or more) follicles increased noticeably from Day 3, as compared with pre-treatment and controls. These results clearly indicated that inhibin is a key hormone in regulation of follicular development through regulation of endogenous FSH secretion during early pregnancy in goats.

Cellular Localization of Inhibin alpha-subunit, PKB/Akt and FoxO3a proteins in the ovaries of minipigs

Experiments were conducted to examine the cellular localization of inhibin alpha-subunit, protein kinase B (PKB/Akt), and FoxO3a proteins in the ovaries of minipigs, Chinese Xiang pigs, by immunohistochemistry. The results indicated that inhibin alpha-subunits were localized in the granulosa cells of follicles at all stages but were not localized in corpora lutea. PKB was localized in the granulosa cells of primordial follicles and in the basal layers of the granulosa cells of preantral and antral follicles, but were not localized in atretic follicles and corpora lutea. FoxO3a was localized in the granulosa cells of follicles at all stages and was extensively localized in the cytoplasma of the luteinized granulosa cells of corpora lutea. Together, the stage- and cell-specific expression patterns of inhibin alpha-subunit, FoxO3a, and PKB suggest that these proteins might play potential roles in follicular development, atresia, and luteinization in the minipig.

Advances in transgenic rat production

Predictable and reproducible production of transgenic rats from a standardized input of egg donors and egg recipients is essential for routine rat model production. In the course of establishing a transgenic rat service, transgenic founders were produced from three transgenes in outbred Sprague-Dawley (SD) rats and four transgenes in inbred Fischer 344 (F344) rats. Key parameters that affect transgenesis efficiency were assessed, including superovulation treatments, methods to prepare pseudopregnant recipients, and microinjection technique. Five superovulation regimens were compared and treatment with 20 IU PMSG and 30 IU HCG was selected for routine use. Four methods to prepare pseudopregnant egg recipients were compared and estrus synchronization with LHRHa and mating to vasectomized males was selected as most effective. More than 80% of eggs survived microinjection when modified pronuclear microinjection needles and DNA buffers were used. The efficiencies of transgenic production in rats and C57BL/6J (B6J) mice were compared to provide a context for assessing the difficulty of transgenic rat production. Compared to B6J mice, SD rat transgenesis required fewer egg donors per founder, fewer pseudopregnant egg recipients per founder, and produced more founders per eggs microinjected. Similar numbers of injection days were required to produce founders. These results suggest that SD rat transgenesis can be more efficient than B6J mouse transgenesis with the appropriate technical refinements. Advances in transgenic rat production have the potential to increase access to rat models.

Induction of superovulation by immunoneutralization of endogenous inhibin in immature rats

The effects of passive immunoneutralization of endogenous inhibin on ovulation rate in immature rats were investigated. Efficiency of superovulation on production of fertilized oocytes was compared between the inhibin antiserum (inhibin-AS) and equine chorionic gonadotropin (eCG) protocols. Immature female Wistar strain rats were superovulated with a single injection of 100-200 microl inhibin-AS, with and without an injection of human chorionic gonadotropin (hCG). A total of 77.8% of the 26-30-day-old rats treated with a single injection of 100-200 microl inhibin-AS ovulated 72 h after treatment, while rats given normal goat serum (NGS; 200 microl) did not ovulate. At 28 days of age, all of the inhibin-AS treated rats ovulated when additional hCG treatment was given, whereas the number of ovulated oocytes was not affected. The number of ovulated oocytes in the inhibin-AS-hCG treated groups was significantly higher than that of the NGS-hCG treated group. In addition, plasma concentrations of FSH in the inhibin-AS-hCG treated group significantly increased compared with the NGS treated group. While the percentage of mated rats in the 200 microl inhibin-AS-hCG treated group was significantly lower than that of the 15 IU eCG-hCG treated group, the fertilization rate was comparable between the two groups. The number of fertilized oocytes in the 200 microl inhibin-AS-hCG treated group was significantly higher in comparison with the 15 IU eCG-hCG treated group. These results suggest that immunoneutralization of endogenous inhibin could be a reliable method for induction of superovulation to collect a large number of normally fertilized oocytes in immature rats.

Passive Immunoneutralization of Endogenous Inhibin Increases Ovulation Rate in Miniature Shiba Goats

We reported previously that passive immunization against inhibin enhances follicular growth and increases the ovulation rate. However, the ovulation rate was not comparable to the number of follicles. Therefore, the aim of this study was to attempt to increase the ovulation rate by increasing the interval between inhibin immunization and PGF2alpha injection. Five miniature Shiba goats were treated with 10 ml inhibin antiserum (inhibin-AS) developed against [Tyro30]-inhibin alpha (1-30). A control group (n=5) was treated with normal goat serum. All animals were injected intramuscularly with 125 microg PGF2alpha 72 h after treatment to induce estrus and ovulation. Blood samples were collected for hormonal assay and the ovulation rate was determined by laparotomy. In contrast to the control group, there was a significant increase in plasma concentrations of FSH in the immunized group. After luteolysis, plasma concentrations of estradiol-17beta increased markedly to a preovulatory peak about 2 folds higher (P<0.01) than that of controls. In addition, the ovulation rate was greater in the immunized group (14.4 +/- 2.2) than in the control group (2.2 +/- 0.6), and the mean number of follicles > or = 4 mm in diameter was 10.0 +/- 0.8 in the inhibin-AS group compared with 2.4 +/- 0.3 in control group. The present results demonstrate that immunoneutralization of endogenous inhibin increased FSH secretions in miniature shiba goats. The increased FSH secretion enhanced follicular growth and increased the ovulation rate. Additionally, increasing the interval between inhibin-AS and PGF2alpha injections (to 72 h) resulted in a greater ovulation rate compared with the previous protocol (48 h). Therefore, inhibin-AS treatment proved to be an effective alternative to exogenous gonadotropin methods for induction of superovulation in goats.