Hatchability evaluation of bovine IVF embryos using OCT-based 3D image analysis.

Although embryo transfer is widely applied in cattle, many of the transferred embryos do not result in pregnancy. To determine a new parameter for bovine embryo evaluation, we investigated the relationships between in vitro hatchability and embryo morphological parameters using optical coherence tomography (OCT) that we established recently. Bovine embryos were obtained from Japanese Black cattle by in vitro fertilization (IVF). The quality of the blastocysts was examined under an inverted microscope and confirmed as Codes 1-3 according to the IETS standards for embryo evaluation. The OCT images of the embryos were captured on Day 7 after IVF, and the embryos were cultured until Day 9 to determine their hatchability. During OCT, the embryos were irradiated with near-infrared light for a few minutes to obtain three-dimensional images. In total, 22 parameters were assessed for each of the 42 embryos, of which 25 hatched (H embryos) and 17 did not (NH embryos). The thickness of the trophectoderm (TE) and TE+zona pellucida (ZP) was lesser, and the volumes of the TE, ZP, blastocoel, and whole embryo and blastocoel diameter were greater in the H embryos than in the NH embryos. PCA identified that the increase in the blastocoel-related value along with the decrease in the thickness-related value of the TE and/or ZP could be indicators for evaluating the hatchability of bovine IVF embryos. These results support the idea that OCT-captured structural data of blastocyst-stage embryos can be used as a potential model to predict the quality of bovine embryos.

Three-dimensional live imaging of bovine embryos by optical coherence tomography.

While embryo transfer (ET) is widely practiced, many of the transferred embryos fail to develop in cattle. To establish a more effective method for selecting bovine embryos for ET, here we quantified morphological parameters of living embryos using three-dimensional (3D) images non-invasively captured by optical coherence tomography (OCT). Seven Japanese Black embryos produced by in vitro fertilization that had reached the expanded blastocyst stage after 7 days of culture were transferred after imaged by OCT. Twenty-two parameters, including thickness and volumes of the inner cell mass, trophectoderm, and zona pellucida, and volumes of blastocoel and whole embryo, were quantified from 3D images. Four of the seven recipients became pregnant. We suggest that these 22 parameters can be potentially employed to evaluate the quality of bovine embryos before ET.

Effect of hypoxia on progesterone production by cultured bovine early and mid luteal cells.

A major role of the corpus luteum (CL) is to produce progesterone (P4). The CL has immature vasculature shortly after ovulation, suggesting it exists under hypoxic conditions. To elucidate the mechanism involved in regulation of luteal cell function during CL development, we compared the effect of hypoxia on P4 production by cultured bovine early and mid luteal cells. Luteal cells obtained from early and mid CL were incubated under different O2 concentrations (20% and 3%) with or without hCG (1 U/ml) for 6 h and 24 h. After 6 h of culture in the presence of hCG, P4 production was not affected by hypoxia whereas decrease in its production by mid luteal cells was observed. After 24 h of culture, P4 production was significantly decreased by hypoxia in both stages of luteal cells regardless of the use of hCG. At 6 h of culture, hypoxia increased mRNA expression of hydroxyl-Δ-5-steroid dehydrogenase, 3ß- and steroid Δ-isomerase 1 (HSD3B1) in early luteal cells, and decreased mRNA expression of cytochrome P450 cholesterol side chain cleavage (CYP11A1) enzyme in mid luteal cells. At 24 h of culture, mRNA expressions of steroidogenic acute regulatory protein (STAR), CYP11A1, and HSD3B1 were not affected by hypoxia in both stages of luteal cells. The overall results suggest that early luteal cells maintain P4 production under hypoxic conditions, and hypoxia-induced HSD3B1 may support this P4 production in the bovine early CL.

Three-dimensional morphology of bovine blastocysts hatched against lipopolysaccharide exposure in vitro.

Embryo transfer in cattle is globally becoming more ubiquitous, but the pregnancy rate is lower than that of artificial insemination. The uterus contains its own bacteria, and concentrations of lipopolysaccharides (LPS) from gram-negative bacteria are higher in uteri affected by endometritis than in healthy uteri and they suppress embryogenesis. The purpose of this study was to investigate the morphological characteristics of bovine embryos with a higher viability and implantability, by analyzing the morphology of bovine blastocysts that successfully hatched under challenge of LPS, using an optical coherence tomography (OCT) system. Developing embryos produced by in vitro fertilization that had reached the blastocyst stage on Day 7 were three-dimensionally scanned using an OCT system, then were continued to culture with or without LPS until Day 9, when the presence or absence of hatching was determined. The OCT-captured three-dimensional images were used to quantify 20 different metrics, including inner cell mass (ICM), trophectoderm, blastocoel, and total embryo volume; each of the parameters was compared between the hatched and unhatched embryos. Under the LPS challenge, hatched embryos had higher ICM thickness and volume, and lower trophectoderm thickness than unhatched embryos. Furthermore, hatched embryos under LPS challenge had higher ICM thickness and ICM volume than hatched embryos without LPS challenge. The present results suggest the possibility that ICM thickness and ICM volume calculated by OCT system could be indices for good quality bovine embryos.

Prediction of maturational competence of feline oocytes using supravital staining of cumulus cells by propidium iodide.

We examined the relationship between integrity of cumulus cells and nuclear maturation rate after in vitro culture to determine a non-invasive prediction of the maturational competence of feline oocytes. Feline cumulus-oocyte complexes (COCs) were collected from either small (400-800 µm) or large (≥800 µm) follicles. Immediately after collection, cumulus cells were evaluated morphologically (thickness of cumulus cell layers) and stained with propidium iodide (PI), which penetrates only non-viable cells. Cumulus cells without PI staining were judged as having good membrane integrity. After evaluation, COCs were cultured for 30 h and their nuclear maturation rate was determined. The nuclear maturation rate of oocytes derived from large follicles (89.8%) was higher (p < 0.05) than that from small follicles (60.8%). There was no difference in the maturation rate of oocytes from follicles with the same size regardless of cumulus morphology. In contrast, oocytes that had cumulus cells with good membrane integrity showed a higher maturation rate (93.8%) than oocytes with poor cumulus integrity (76.9%) in large follicles (p < 0.05). We conclude that evaluation of membrane integrity of cumulus cells by propidium iodide staining can be used to predict the maturational competence of oocytes.

Positive feedback loop between prostaglandin E2 and EGF-like factors is essential for sustainable activation of MAPK3/1 in cumulus cells during in vitro maturation of porcine cumulus oocyte complexes.

During in vitro maturation of porcine cumulus-oocyte complexes (COCs), follicle-stimulating hormone (FSH) increases both prostaglandin E2 (PGE2) production and the expression levels of EGF-like factors. The ligands act on cumulus cells by the autocrine system due to their specific receptors, EP2, EP4, or EGF receptor. When each pathway is suppressed by inhibitors, complete cumulus expansion and oocyte maturation do not occur. In this study, we examined the relationship between both of these pathways in cumulus cells of porcine COCs. When COCs were cultured with FSH, Fshr mRNA expression was immediately decreased within 5 h, whereas Ptger2, Ptger4, and Ptgs2 expression levels were significantly increased in cumulus cells in the culture containing FSH for 5 or 10 h. The PTGS2 inhibitor NS398 significantly suppressed not only PGE2 secretion at any culture time point but also Areg, Ereg, and Tace/Adam17 expression in cumulus cells at 10 and 20 h but not at 1 or 5 h. During the early culture period, phosphorylation of MAPK3 and MAPK1 (MAPK3/1) was not affected by NS398; however, at 10 and 20 h, phosphorylation was suppressed by the drug. Furthermore, down-regulations of MAPK3/1 phosphorylation and expression of the target genes by NS398 was overcome by the addition of either PGE2 or EGF. FSH-induced cumulus expansion and meiotic progression to the MII stage were also suppressed by NS398, whereas these effects were also overcome by addition of either PGE2 or EGF. These results indicated that PGE2 is involved in the sustainable activation of MAPK3/1 in cumulus cells via the induction of EGF-like factor, which is required for cumulus expansion and meiotic maturation of porcine COCs.

The effect of ovarian status and follicular diameter on maturational ability of domestic cat oocytes.

The objective of this study was to clarify the effect of ovarian status and follicular size on morphological normality and maturational ability of cat oocytes. Ovarian status was classified into inactive, follicular, luteal and prepubertal, and follicles were classified into three groups according to their diameter (400-800, 800-1200 and 1200-2000 µm). In each ovarian status, the number of follicles decreased but the percentage of morphologically normal oocytes increased with the growth of follicles (p<0.05). Only a single follicle that was 1200-2000 µm in diameter was observed in two of the five prepubertal cats. In follicles that were 800-1200 µm in diameter, the percentage of normal oocytes and maturation rate were higher in prepubertal cats than in mature cats (p<0.05). Oocyte diameter tended to increase with the growth of follicles. After oocytes were cultured individually in droplets of maturation medium, the oocyte maturation rate increased with the growth of follicles in each ovarian status (p<0.05). In conclusion, oocytes collected from larger follicles possess higher maturational ability in vitro in sexually mature cats. In prepubertal cats, a higher maturation rate can be obtained from oocytes derived from small follicles compared with in mature cats.

Three-Dimensional Live Imaging of Bovine Preimplantation Embryos: A New Method for IVF Embryo Evaluation.

Conception rates for transferred bovine embryos are lower than those for artificial insemination. Embryo transfer (ET) is widely used in cattle but many of the transferred embryos fail to develop, thus, a more effective method for selecting bovine embryos suitable for ET is required. To evaluate the developmental potential of bovine preimplantation embryos (2-cell stage embryos and blastocysts), we have used the non-invasive method of optical coherence tomography (OCT) to obtain live images. The images were used to evaluate 22 parameters of blastocysts, such as the volume of the inner cell mass and the thicknesses of the trophectoderm (TE). Bovine embryos were obtained by in vitro fertilization (IVF) of the cumulus-oocyte complexes aspirated by ovum pick-up from Japanese Black cattle. The quality of the blastocysts was examined under an inverted microscope and all were confirmed to be Code1 according to the International Embryo Transfer Society standards for embryo evaluation. The OCT images of embryos were taken at the 2-cell and blastocyst stages prior to the transfer. In OCT, the embryos were irradiated with near-infrared light for a few minutes to capture three-dimensional images. Nuclei of the 2-cell stage embryos were clearly observed by OCT, and polynuclear cells at the 2-cell stage were also clearly found. With OCT, we were able to observe embryos at the blastocyst stage and evaluate their parameters. The conception rate following OCT (15/30; 50%) is typical for ETs and no newborn calves showed neonatal overgrowth or died, indicating that the OCT did not adversely affect the ET. A principal components analysis was unable to identify the parameters associated with successful pregnancy, while by using hierarchical clustering analysis, TE volume has been suggested to be one of the parameters for the evaluation of bovine embryo. The present results show that OCT imaging can be used to investigate time-dependent changes of IVF embryos. With further improvements, it should be useful for selecting high-quality embryos for transfer.

Research of postpartum endometritis in Japanese Black cattle with cystic ovarian disease by vaginal mucus test and endometrial cytology.

The relationship between endometritis and cystic ovarian disease (COD) is still unclear in Japanese Black cattle. Endometritis is classified into clinical endometritis (CE) and subclinical endometritis (SE). The objective of this study was to clarify the interaction between postpartum endometritis (CE and SE) and COD in Japanese Black cattle. Twenty-six suckled cows with COD (COD group) and 16 suckled cows with cyclical ovarian activity (CA group) were submitted for the experiment. Uterine conditions of cows were classified into three groups (normal, CE, and SE) with vaginal mucus test and endometrial cytology. The combined data of CE and SE were represented as data for total endometritis (EMT total). The prevalence of EMT total in the COD group (42.3 %, 11 / 26 ) was significantly higher than that of the CA group (12.5 %, 2 / 16 ). The mean percentage of polymorphonuclear neutrophils (PMN %) in the COD group was significantly higher than that of the CA group at 40-60 DPP (days postpartum). Compared to 61-295 DPP, the mean PMN % at 40-60 DPP was significantly higher in the COD group. The diameters of uterine horn and cervix did not differ among normal uterine condition, CE and SE in the COD group, and they did not differ between normal uterine condition and SE in the CA group. However, endometrial thickness during both 40-60 and 61-295 DPP were greater in the COD group than in the CA group. In conclusion, Japanese Black cattle with COD have a potential implication on endometritis at 40-60 DPP compared to the normal ovarian cycle. As a specific symptom was not observed by transrectal ultrasonography, endometrial cytology is effective for diagnosis of SE in Japanese Black cattle.

Effect of post artificial insemination treatment with two different progesterone intravaginal devices on conception and synchronization of the returning estrus in Japanese Black cows.

The objective of this study was to evaluate the effects of post artificial insemination (AI) treatment with intravaginal progesterone device (P4 device) on conception rate, synchronization of returning estrus and plasma P4 concentration in Japanese Black cows. Nineteen cows were treated with DIB (1.0 g P4) from Day 12 to 19 (Day 0=day of the first AI), 27 cows were treated with a CIDR (1.9 g P4) from Day 12 to 19, and 33 cows were not treated after the first AI (control). Estrous behavior was daily examined between Day 20 and 25, and cows returning to estrus were inseminated (the second AI). On Day 19, plasma P4 concentration was not different among DIB, CIDR and control groups. There was no significant difference in conception rate after the first AI among three groups (DIB: 63.2%, CIDR: 66.7% and control: 72.7%). In non-pregnant cows, there was no significant difference in the proportion of cows showed returning estrus between Day 20 and 25 (DIB: 57.1%, CIDR: 22.2% and control: 44.4%), and day of returning estrus was not synchronized. The overall conception rate after the first and second AI was not different among the groups. In conclusion, post-AI treatment with intravaginal devices containing 1.0 and 1.9 g P4 from Day 12 to 19 neither increased plasma P4 concentration nor improved fertility and synchronization of the returning estrus in Japanese Black cows.

BNIP3 expression in bovine follicle and corpus luteum.

BNIP3 (BCL2/adenovirus E1B nineteen kilodalton interacting protein-3), a member of the BCL2 family, is activated under hypoxic conditions and induces apoptosis or mitochondrial autophagy for adapting cells to hypoxia. The physiological roles of BNIP3 in the mammalian ovary are still unclear. In order to understand the role of BNIP3 in the bovine ovary, we examined its mRNA and protein expressions of BNIP3 in follicular granulosa cells and corpus luteum (CL). BNIP3 mRNA and protein expressions in granulosa cells from large follicles (>10 mm) at the follicular stage were much higher than those in small follicles (2-8 mm). BNIP3 mRNA and protein expressions in the CL peaked at the early luteal stage. In bovine granulosa cells cultured for 6 hr under hypoxia (3% O2) and normoxia (20% O2), BNIP3 mRNA expression was higher under hypoxia. These results of the present study suggest that BNIP3 has some roles in luteal formation in the bovine ovary, and that the highly expressed BNIP3 in the granulosa cells from large follicles at the follicular stage is related to the roles of BNIP3 in the luteal formation.

Effects of isolation method and pre-treatment with ethylene glycol or raffinose before vitrification on in vitro viability of mouse preantral follicles.

Effects of isolation and vitrification protocols on follicular survival after warming were examined. Mouse preantral follicles enzymatically or mechanically isolated from ovaries of 12-day-old mice were exposed either to 2 M ethylene glycol (EG) for 2 or 5 min, or to ascending concentrations (0.15 then 0.3 M) of raffinose for 2 or 5 min each (2-2 and 5-5 min). They were then exposed to a vitrification solution (VS) composed of 6 M EG and 0.3 M raffinose for 0.5, 1, or 2 min before vitrification. Mechanically isolated follicles showed higher survival than enzymatically isolated follicles, regardless of periods of exposure to EG or raffinose and subsequent exposure to VS. After 10 days of culture, follicular growth and maturational ability of oocytes derived from vitrified follicles exposed to 2 M EG for 5 min and to VS for 1 min were higher than those from follicles exposed to raffinose solutions for 2-2 min and to VS for 1 min. Histological evaluation revealed that exposure of preantral follicles to raffinose solutions caused cytoplasmic vacuolation in granulosa cells which could be due to cellular shrinkage during dehydration; whereas, exposure to 2 M EG induced morphological alterations in follicles only to a lesser extent.

Hypoxia increases glucose transporter 1 expression in bovine corpus luteum at the early luteal stage.

A major role of the corpus luteum (CL) is to produce progesterone (P4). The CL has immature vasculature shortly after ovulation, suggesting it exists under hypoxic conditions. Hypoxia-inducible factor-1 (HIF1) induces the expression of glucose transporter 1 (GLUT1). To clarify the physiological roles of GLUT1 in bovine CL, we examined GLUT1 mRNA expression in the CL under hypoxic conditions by quantitative RT-PCR. We also measured the effects of glucose (0-25 mM) and GLUT1 inhibitors (cytochalasin B, STF-31) on P4 production in bovine luteal cells. GLUT1 mRNA expression in bovine CL was higher at the early luteal stage compared to the other later stages. Hypoxia (3% O2) increased GLUT1 mRNA expression in early luteal cells, but not in mid luteal cells. Glucose (0-25 mM) increased P4 production in early luteal cells, but not in mid luteal cells. Both GLUT1 inhibitors decreased P4 production in early and mid luteal cells. Overall, the results suggest that GLUT1 (possibly induced by hypoxic conditions in the early CL) plays a role in the establishment and development of bovine CL, especially in supporting luteal P4 synthesis at the early luteal stage.

Evaluation of membrane integrity of canine epididymal spermatozoa by short hypoosmotic swelling test with ultrapure water.

The effectiveness of the water test, short hypoosmotic swelling test with ultrapure water was examined in canine epididymal spermatozoa to evaluate tail membrane integrity. Spermatozoa during epididymal transit were also characterized. Sperm suspension obtained from cauda epididymis was diluted 1:4 with ultrapure water, and incubated for 5 min. The percentage of swollen spermatozoa in the water test was significantly correlated with both the sperm motility and the swelling value obtained by the conventional hypoosmotic swelling test. Canine spermatozoa collected from the caput epididymis were not motile, but revealed membrane integrity in a water test. The water test can be used as a simple and short hypoosmotic swelling test to evaluate the tail membrane integrity of canine epididymal spermatozoa.

Influence of theophylline supplementation on oocyte penetration of canine epididymal spermatozoa.

The influence of supplementation of theophylline to the medium regarding the penetration of canine epididymal spermatozoa into immature oocytes was examined. In the control medium, sperm penetration into the oocytes was observed in 8 of 13 dogs (61.5%), and the mean penetration rate was 22.0%. The penetration rate of individual dogs ranged from 0 to 64.9%. Supplementation of 0.1, 1.0 and 2.5 mM theophylline to the medium did not significantly affect sperm penetration. Sperm penetration was induced by supplementation of 2.5 mM theophylline in two dogs that showed no sperm penetration in the control group. Penetration of the epididymal spermatozoa into the oocytes was shown to vary among individual dogs in cases of the absence and presence of theophylline.

Protein kinase C (PKC) increases TACE/ADAM17 enzyme activity in porcine ovarian somatic cells, which is essential for granulosa cell luteinization and oocyte maturation.

During in vitro maturation of porcine cumulus cell-oocyte complexes and in vitro luteinization of porcine granulosa cells, FSH induces the expression of the protease TNFα-converting enzyme/A disintegrin and metalloproteinase domain 17 (TACE/ADAM17) and the epidermal growth factor (EGF)-like factors, which activate the EGF receptor (EGFR)-MAPK3/1 pathway in both cumulus and granulosa cells. FSH is known to activate not only protein kinase A and p38MAPK pathways in both cell types but also activates protein kinase C (PKC). Because PKC-induced association of cellular-Sarcoma (c-Src) and TACE/ADAM17 is required for TACE/ADAM17 enzyme activation in some cancer cells, we hypothesized that PKC and c-Src impact TACE/ADAM17-mediated activation of EGFR signaling pathway in porcine granulosa and cumulus cells. When granulosa cells or cumulus cell-oocyte complexes were cultured with FSH, PKC activity and c-Src phosphorylation increased and were associated with increased TACE/ADAM17 enzyme activity. The PKC inhibitor calphostin C (CalC) and the c-Src inhibitor (4 amino 5 (4 chlorophenyl) 7 (t butyl)pyrazolo[3,4 d]pyrimidine [PP2]) suppressed TACE/ADAM17 enzyme activity, whereas these inhibitors did not affect Tace/Adam17 mRNA expression. Immunoprecipitation analysis showed that FSH mediated the association of c-Src with TACE/ADAM17 via a PKC-dependent mechanism. Either CalC or PP2 suppressed EGFR downstream signaling pathway (MAPK3/1) in these ovarian cell types and reduced cumulus expansion, meiotic maturation of oocytes, and progesterone production. The negative effects were overcome by the addition of amphiregulin. Collectively, these results indicate that activation of TACE/ADAM17 via a PKC-induced c-Src-dependent manner mediates proteolytic activation of the EGF-like factors that are involved in the induction of granulosa cell differentiation, cumulus expansion, and meiotic maturation of porcine oocytes in vitro.

Effect of butylated hydroxytoluene on dog sperm longevity in chilling storage and cryopreservation.

This study evaluated the effect of butylated hydroxytoluene (BHT), a lipid-soluble antioxidant, on dog sperm in chilling storage and cryopreservation. In Experiment 1, 0.2, 0.4, 0.8 and 1.6 mM BHT were added to egg yolk Tris extender (EYT), and sperm were stored at 4°C for 96 hr. Sperm motility, viability, acrosomal integrity and morphological abnormality in the BHT treatment groups were not different from those of the control (0 mM BHT). In Experiment 2, the effect of BHT in EYT containing 0.75% Equex STM paste and 5% glycerol on survivability of cryopreserved sperm was examined after culture at 39°C for 3 hr. Sperm motility, viability and acrosomal integrity in the 0.2 to 0.8 mM BHT treatment groups were not different from those of the control. However, sperm motility, viability and acrosomal integrity decreased when 1.6 mM BHT was added to the extender (P<0.05). In conclusion, supplementation of the extender with 0.2 to 0.8 mM BHT did not affect characteristics of dog sperm in chilling storage and cryopreservation. Supplementation of 1.6 mM BHT did not affect characteristics of chilled sperm but impaired longevity of cryopreserved sperm in the dog.

Cryopreservation of microencapsulated canine sperm.

The objective was to develop a method for cryopreserving microencapsulated canine sperm. Pooled ejaculates from three beagle dogs were extended in egg yolk tris extender and encapsulated using alginate and poly-L-lysine at room temperature. The microcapsules were cooled at 4 °C, immersed in pre-cooled extender (equivalent in volume to the microcapsules) to reach final concentration of 7% (v/v) glycerol and 0.75% (v/v) Equex STM paste, and equilibrated for 5, 30 and 60 min at 4 °C. Thereafter, microcapsules were loaded into 0.5 mL plastic straws and frozen in liquid nitrogen. In Experiment 1, characteristics of microencapsulated canine sperm were evaluated after glycerol addition at 4 °C. Glycerol exposure for 5, 30 and 60 min did not significantly affect progressive motility, viability, or acrosomal integrity of microencapsulated sperm compared with pre-cooled unencapsulated sperm (control). In Experiment 2, characteristics of frozen-thawed canine microencapsulated sperm were evaluated at 0, 3, 6, and 9 h of culture at 38.5 °C. Pre-freeze glycerol exposure for 5, 30, and 60 min at 4 °C did not influence post-thaw quality in unencapsulated sperm. Post-thaw motility and acrosomal integrity of microencapsulated sperm decreased more than those of unencapsulated sperm (P < 0.05) following glycerol exposure for 5 min. However, motility, viability and acrosomal integrity of microencapsulated sperm after 30 and 60 min glycerol exposure were higher than unencapsulated sperm cultured for 6 or 9 h (P < 0.05). In conclusion, since microencapsulated canine sperm were successfully cryopreserved, this could be a viable alternative to convention sperm cryopreservation in this species.

Polled Intersex Syndrome with urethral atresia in a goat.

A 5-day-old hornless goat was referred with dysuria since birth. The scrotum was absent, and a small penis-like structure was seen below the perineal raphe. On the laparotomy, the testicles were found near the inguinal ring- and attached to a uterus-like structure. On histological analysis, the uterus-like structure was blind-end. Germ cells were absent in the testis. The karyotype of this goat was 60, XX and the SRY gene was absent. The goat was homozygous for a DNA deletion responsible for the Polled Intersex Syndrome (PIS). To the authors' knowledge, this is the first report as the clinical case of the PIS-/- goat with urethral atresia.

Progesterone is essential for maintenance of Tace/Adam17 mRNA expression, but not EGF-like factor, in cumulus cells, which enhances the EGF receptor signaling pathway during in vitro maturation of porcine COCs.

During in vitro maturation of porcine cumulus-oocyte complexes (COCs), progesterone was secreted from cumulus cells and acted on the cumulus cells themselves, which required for cumulus expansion and oocyte maturation. EGF-like factor (amphiregulin, AREG; epiregulin, EREG) and its protease, TACE/ADAM17, are also expressed in cumulus cells, and thereby, soluble EGF domain was acted on the EGF receptor expressed on cumulus cells. In this study, we examined the relationship between progesterone function and EGF-like factor stimuli in cumulus cells of porcine COCs. When COCs were cultured with FSH and LH, Areg, Ereg and Tace/Adam17 were expressed in cumulus cells. Treatment with a progesterone receptor (PGR) antagonist, RU486, did not affect the Areg and Ereg mRNA expression levels at any culture time points. However, the Tace/Adam17 mRNA level, protein level and its activity were significantly suppressed by RU486 at the 30 or 40 h time point. At 20 h of culture, phosphorylation of ERK1/2 and the expressions of target genes (Has2, Tnfaip6 and Ptgs2) were not suppressed by RU486; however, at 40 h, ERK1/2 phosphorylation and the target gene expression levels were significantly downregulated by RU486 in cumulus cells. Furthermore, the negative effects of RU486 at 40 h were overcome by the addition of EGF. These results indicated that the level of TACE/ADAM17 in cumulus cells was regulated by the progesterone-PGR pathway during in vitro maturation of porcine COCs. Therefore, we concluded that the progesterone-induced TACE/ADAM17 leads to production of soluble EGF domain from cumulus cells, which enhances functional changes of cumulus cells and progresses meiotic maturation of oocytes during in vitro maturation of porcine COCs.