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PubMed2005

Growth and maturation of follicles and oocytes following xenotransplantation of porcine ovarian tissues and in vitro maturation.

This is the first report to show morphological evidence of in vitro maturation of oocytes recovered from xenotransplanted antral follicles. To develop a suitable tool for studing the growth and maturation of follicles and oocytes, we xenotransplanted small pieces of ovarian cortical tissue from sows, which contained small preantral follicles (primordial, primary, and secondary follicles; less than 0.05, 0.1 and 0.3 mm in diameter, respectively), under the capsules of kidneys of adult female severe combined immunodeficient (SCID) mice for 2 and 8 weeks, and then recovered cumulus-oocyte complexes from the growing tertiary follicles in xenografted tissues. The distribution of processes from cumulus cells to oocytes and the follicular growth, development, and maturation during xenotransplantation were histochemically analyzed. Tertiary follicles, 0.5 to 3.0 mm in diameter, were obtained from grafted tissues 2 (85%: 52 follicles/61 grafted tissues) and 8 (50%: 15/30) weeks after xenotransplantation, and then oocytes, which were tightly attached to cumulus cells, were collected from each tertiary follicle and cultured to assess their quality. At 2 weeks after grafting, 17.6% of the oocytes had matured to the metaphase II stage, but no such maturation was observed 8 weeks after grafting. Thus, in the 2 weeks group, preantral follicles rapidly grew in xenotransplanted porcine ovarian tissues to the tertiary stage, and oocytes could be recovered and matured from them by in vitro culture.

Actin Cytoskeleton↗

PubMed2002

Cysteamine supplementation during in vitro maturation and embryo culture: a useful tool for increasing the efficiency of bovine in vitro embryo production.

Cysteamine when added during in vitro maturation (IVM) or in vitro embryo culture (IVC) stimulates glutathione (GSH) synthesis and improves embryo developmental rates. This suggests that GSH synthesis is decreased in the in vitro produced embryo. The present study was carried out to evaluate if addition of cysteamine to culture medium at the same time, during IVM and IVC of bovine oocytes, may promote an overall improvement on the developmental rate and embryo quality. Oocytes were matured in TCM 199 supplemented with 10% (v/v) fetal calf serum, hormones, and 0 or 100 microM of cysteamine for 24 hr. After IVM, the oocytes were fertilized (day 0). Day 2 embryos (2-8 cell) were washed and transferred to fresh IVC medium supplemented with 0, 25, 50, or 100 microM of cysteamine and cultured for 48 hr. After this, embryos were cultured in IVC medium without cysteamine until day 8 of IVC. In the present study, we confirmed our previous results by demonstrating that the percentage of embryos that developed to the blastocyst stage was significantly higher (P < 0.05) when 100 microM of cysteamine was added during IVM, and this was further improved when 100 and 50 microM of cysteamine where present during IVM and IVC, respectively (P < 0.05). After cryopreservation, no differences were observed on embryo development, but a significant increase on embryo hatching was found between unsupplemented and supplemented oocytes with 100 and 50 microM of cysteamine during IVM and IVC, respectively (P < 0.05). We can conclude that GSH synthesis stimulation during bovine IVM with cysteamine, concomitant with GSH stimulation during IVC, will be a useful and simple tool for increasing the efficiency of in vitro bovine embryo production.

Animals↗

PubMed1993

Effect of medium-199 and fetal calf serum on in vitro maturation of domestic cat oocytes.

In vitro maturation (IVM) and fertilization are potentially useful for propagating threatened or endangered species. The domestic cat is currently used in this field as an experimental model for studies aimed at non-domestic Felidae. At present optimal conditions for obtaining IVM of cat oocytes have not yet been completely defined. The aim of this study was to evaluate two parameters derived from the procedures that currently ensure high maturation rates in domestic ruminants: (1) the suitability of a complex medium (M-199) for IVM of cat oocytes; (2) the effect of different concentrations of fetal calf serum in the culture medium with or without the addition of gonadotrophins. The maturation rate at two different intervals from the onset of culture (24 and 48 h) was also evaluated. The use of M-199 allowed resumption of meiosis in 4.3-18.7% of cat oocytes, according to the supplements and culture periods used. No significant differences were recorded among the treatment groups (P > 0.05). Meiosis was completed in 90.9% of cases within 24 h with no significant differences between the three treatment groups (P > 0.05). A 3.2% rate of parthenogenesis was observed at the end of the maturation period with no significant differences between the culture systems (P > 0.05). However, the percentage cleavage of oocytes was much higher (29%) when correlated with the percentage that had matured. In this case significant differences among treatments were also observed (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2001

Morphology of in-vitro matured oocytes: impact on fertility potential and embryo quality.

BACKGROUND: The purpose of the present study was to investigate the morphology of in-vitro matured metaphase II (MII) oocytes and to observe if there was a difference in the morphology between polycystic and normal ovaries. Furthermore, the morphology of in-vitro matured MII oocytes was related to their subsequent fertilization and cleavage rates and to embryo quality. METHODS: This retrospective study included 264 MII oocytes obtained in 100 consecutive cycles. Oocyte retrieval was performed transvaginally and cumulus enclosed oocytes were matured for 28--30 h before evaluation. Prior to ICSI, all MII oocytes were graded into three groups according to the number of anomalies: grade I: oocytes without any anomaly (n = 144, 54%), grade II: oocytes with one anomaly (n = 87, 33%) and grade III: oocytes with at least two anomalies (n = 33, 12.5%). RESULTS: Oocyte grades did not differ between women with polycystic ovaries [grades I, II and III respectively: 58/94 (61.7%), 29/94 (30.9%) and 7/94 (7.4%)] and women with normal ovaries [grades I, II and III respectively: 86/170 (50.6%); 58/170 (34%); 26/170 (15.3%)]. Morphology was not related to fertilization rates. The cleavage rate was, however, affected by morphological anomalies (grade I [77/144 (53.5%) versus grade II 33/87 (37.9%) (P = 0.03)], although no significant decrease in cleavage rate could be demonstrated when all grade II and III oocytes were compared with normal oocytes. Significantly more embryos of good quality developed after grade I oocytes [54/144 (37.5%)] compared with those from grade II and grade III oocytes (22/120; P = 0.001). The presence of cytoplasmic abnormalities significantly decreased the cleavage rate (P = 0.04) and also the number of good quality embryos (P < 0.001). CONCLUSION: The in-vitro maturation of oocytes without anomalies yields higher quality embryos, with higher cleavage rates, than those with anomalies.

Cells, Cultured↗

PubMed2006

Effect of gonadotrophin priming on in-vitro maturation of oocytes collected from women at risk of OHSS.

This study examined the effects of human menopausal gonadotrophin (HMG) or human chorionic gonadotrophin (HCG) priming on cumulus-oocyte complex (COC) morphology, oocyte maturation and embryo development in patients undergoing in-vitro maturation (IVM) cycles. The patients were primed with nothing (group 1), low-dose HMG (group 2) or 10,000 IU HCG (group 3) before oocyte retrieval. COC with dispersed cumulus cell appearance was only observed in group 3. In addition, 11% of metaphase II stage oocytes at the time of retrieval were collected from group 3. Oocyte maturation in vitro in group 3 was faster than that in groups 1 and 2. The blastocyst development rate of residual embryos after embryo transfer in group 3 was significantly higher than that of groups 1 and 2 (P < 0.05). These results suggest that HCG priming may stimulate the COC, promote oocyte maturation, and improve developmental competence in IVM cycles.

Adult↗

PubMed2004

Origin of bovine follicular fluid and its effect during in vitro maturation on the developmental competence of bovine oocytes.

Protein supplementation during in vitro maturation can profoundly affect both the rate and overall efficiency of the maturation procedure. The present study was conducted to assess the ability of different concentrations (1, 5, and 10%) of bovine follicular fluid (bFF) to support in vitro maturation of oocytes and subsequent developmental capacity. The bFF was derived either from competent follicles ( > 8 mm) obtained by transvaginal recovery following superovulation or from a pool of small follicles (2-5 mm) from abbatoir-derived ovaries. Bovine oocytes were cultured for 24 h in synthetic oviduct fluid medium (m-SOF) supplemented with polyvinylpyrrolidone. Following fertilization and embryo culture, more oocytes (P < 0.05) reached the blastocyst stage when oocytes were cultured with 5% bFF from competent follicles (41 +/- 3.7%) compared with bFF derived from small follicles (16 +/- 2.9%). Estradiol and recombinant human follicle stimulating hormone added to the competent bFF during maturation acted in synergy to increase blastocyst production rate (P < 0.05); this blastocyst production rate (57 +/- 1.2%) was higher than those obtained with the addition of these two hormones to bFF derived from small follicles (26 +/- 2.9%). The quality of blastocysts obtained was reflected by inner cell mass (51.30 +/- 3.5 and 25.50 +/- 3.7) and trophectoderm cell numbers (99.72 +/- 2.5 and 94.80 +/- 4.7) for bFF from competent and small follicles, respectively. In conclusion, follicular fluid originating from competent follicles increased the developmental competence of abbatoir-derived oocytes.

Abattoirs↗

PubMed2002

Conditions for in vitro maturation and artificial activation of ferret oocytes.

The ferret represents an attractive species for animal modeling of lung diseases because of the similarity between ferret and human lung biology and its relatively small size and short gestation time. In an effort to establish experimental protocols necessary for cloning ferrets, optimized conditions for in vitro maturation and artificial activation of ferret oocytes were examined. Cumulus-oocyte complexes were harvested from ovaries of superovulated ferrets, and in vitro maturation was evaluated in three different culture media: medium 1 (TCM-199 + 10% FBS), medium 2 (TCM-199 + 10% FBS with eCG [10 IU/ml] and hCG [5 IU/ml]), or medium 3 (TCM-199 + 10% FBS with eCG, hCG, and 17beta-estradiol [2 microg/ml]). After 24 h of maturation in vitro, the maturation rate of oocytes cultured in medium 2 (70%, n = 79) was significantly greater (P < 0.01) than those of oocytes cultured in the other two media (27%-36%, n = 67-73). At 48 h, similar maturation rates (56%-69%, n = 76-87) were observed for all three types of media. For activation experiments, oocytes cultured in medium 2 were stimulated with electrical and chemical stimuli either individually or in combination. Treatment with cycloheximide and 6-dimethylaminopurine (6-DMAP) following electrical stimulation resulted in 43% (n = 58) of the oocytes developing to the blastocyst stage. Such an activation rate represented a significant improvement over those obtainable under other tested conditions, including individual treatment with electrical pulses (10%, n = 41), cycloheximide (3%, n = 58), or 6-DMAP (5%, n = 59). Blastocysts derived from in vitro activation appeared to be normal morphologically and were composed of an appropriate number of both inner cell mass (mean +/- SEM, 10.3 +/- 1.1; n = 11) and trophectoderm (60.8 +/- 2.9, n = 11) cells. These results have begun to elucidate parameters important for animal modeling and cloning with ferrets.

Animals↗

PubMed1998

Development of hatching blastocysts from immature human oocytes following in-vitro maturation and fertilization using a co-culture system.

Recently, in-vitro maturation (IVM) of immature human oocytes recovered from non-stimulated follicles has been applied in the treatment of infertility. However, in previous reports, very few embryos cultured in conventional medium have reached the expanded blastocyst stage following in-vitro maturation and fertilization (IVM/IVF). The objective of this study was to investigate whether the developmental competence of human embryos following IVM/IVF could be enhanced by the use of a human ampullary cell co-culture system. Immature human oocytes were aspirated from small follicles at Caesarean section and then cultured in medium containing human menopausal gonadotrophin for 36 to 48 h, followed by insemination. Zygotes were randomly cultured either in conventional culture medium alone or in the co-culture system. Of 48 embryos cultured in conventional medium alone, all arrested at the 2-16-cell stage on day 3 after insemination. Of 46 embryos cultured in the co-culture system, 26 embryos (56.5%) arrested at the 2-16-cell stage. Six embryos (13%) developed to the morula stage. Fourteen embryos (30.4%) developed to expanded blastocysts and two blastocysts were hatching on day 7 after insemination. We conclude that co-culture significantly enhances the development of blastocysts in embryos resulting from IVM/IVF.

Adult↗

PubMed1999

Pregnancies resulting from in vitro matured oocytes retrieved from patients with polycystic ovary syndrome after priming with human chorionic gonadotropin.

OBJECTIVE: To describe pregnancies that resulted from in vitro matured oocytes derived from two unstimulated, anovulatory patients with polycystic ovary syndrome after priming with hCG before oocyte retrieval. DESIGN: Case series. SETTING: McGill Reproductive Center, Royal Victoria Hospital, McGill University. PATIENT(S): Two women with polycystic ovary syndrome. INTERVENTION(S): Progesterone induction of a withdrawal bleeding episode. The administration of subcutaneous hCG 36 hours before oocyte retrieval in a natural menstrual cycle. In vitro maturation of immature oocytes, fertilization, and ET. Luteal support with oral estrogen and progesterone. MAIN OUTCOME MEASURE(S): Pregnancy outcome. RESULT(S): Two clinical pregnancies were confirmed after oocyte maturation in vitro, fertilization with intracytoplasmic sperm injection, and ET. CONCLUSION(S): The administration of hCG 36 hours before harvesting of immature oocytes may improve the maturational and developmental competence of the oocytes and the pregnancy rates of unstimulated patients with polycystic ovary syndrome.

Adult↗

PubMed1998

Nuclear staining and culture requirements for in vitro maturation of domestic bitch oocytes.

Oocyte nuclear staining and culture requirements for in vitro maturation (IVM) in the bitch have yet to be fully investigated. In the first part of this study we investigated 7 methods for labeling nuclear material (573 oocytes). The most favorable method involved fixation plus aceto-orcein staining and light microscopy. The influence of serum supplementation of the culture medium for IVM was then investigated (1292 oocytes). Culture was performed in media supplemented with no serum or with 5, 10 and 20% fetal calf serum (FCS) and 0.3 or 4% bovine serum albumin (BSA). Identifiable nuclear material was either a germinal vesicle (GV) or GV breakdown (GVBD). After 48 h in medium plus 0, 5, 10 or 20% FCS and 0.3 or 4% BSA, the percentage of oocytes matured to GVBD was 13, 9, 15, 23, 36 and 40%, and the percentage matured to metaphase I/anaphase I/metaphase II was 4, 12, 24, 14, 36 and 13%, respectively. After 96 h, maturation to GVBD was 31, 14, 21, 11, 50 and 38%, and to metaphase I/anaphase I/metaphase II it was 6, 5, 3, 19, 15 and 9%, respectively. Within the limits of this study, BSA or high concentrations of FCS appear to be optimal for bitch oocyte maturation in vitro.

Animals↗

PubMed1996

Stimulation of glutathione synthesis of in vitro matured bovine oocytes and its effect on embryo development and freezability.

Glutathione (GSH) has been shown to play an important role in embryo development. In a previous study, we demonstrated that cysteamine supplementation of in vitro maturation (IVM) medium increased the intracellular GSH content in bovine oocytes and improved subsequent embryo development to the blastocyst stage. The present study was carried out to evaluate the effect of inhibition by buthionine sulfoximide (BSO) of GSH synthesis during IVM in the presence of cysteamine, on subsequent embryo development, and the effect of cysteamine during IVM on the survival of blastocysts following freezing. The effect of beta-mercaptoethanol and cysteine added to the maturation medium on GSH levels in bovine oocytes, as well as the effect of these compounds on de novo GSH synthesis by oocytes during in vitro maturation, was also studied. The inhibitory effect of BSO during in vitro maturation on GSH synthesis was also evaluated. Evidence was found confirming that GSH synthesis occurs intracellularly during IVM of oocytes and is stimulated by cysteamine, beta-mercaptoethanol and cysteine. Moreover, the present results suggest that the increase in the rate of embryo development exerted by cysteamine, when present during IVM, was due to its stimulatory effect on GSH synthesis. This increase in GSH levels during IVM improves embryo development and quality, producing more embryos reaching the blastocyst stage on day 6, those most suitable for freezing.

Animals↗

PubMed2000

Possible factors affecting the development of oocytes in in-vitro maturation.

To date, pregnancy rates from oocytes matured in-vitro (IVM) have been much lower than those with in-vivo stimulated maturation. In order to improve the developmental potential of IVM oocytes, we studied the effect of three possible factors on pregnancy rates: (i) priming in vivo with FSH before aspiration; (ii) the time interval of maturation in vitro, and (iii) timing the aspiration by monitoring the serum concentrations of oestradiol and inhibin A. In all experiments, oocyte retrieval was performed transvaginally and oocytes were matured individually in culture medium (TCM 199) under oil. Intracytoplasmic sperm injection (ICSI) was carried out on all metaphase II oocytes. Suitable embryos (maximum of two) were replaced after culturing for 2-3 days in IVF medium. Endometrial priming consisted of 2 mg 17beta-oestradiol, taken orally three times a day from the day of oocyte retrieval, and intravaginal progesterone suppositories initiated 2 days later. In the first experiment, 20 women were randomly allocated to two groups: group I (n = 10 cycles) received no stimulation, while group II (n = 10 cycles) received recombinant FSH 150 IU/day for 3 days, initiated on day 3. FSH priming did not affect the rates of maturation, fertilization or cleavage, and no effect was seen on embryo development. The second experiment included 48 patients undergoing 55 unstimulated cycles. The effects of IVM periods of 28 and 36 h were compared. Shortening the IVM period did not compromise subsequent embryo development. The third study analysed the results of maturation of oocytes obtained in 87 cycles in 75 unstimulated normal women, after a leading follicle of 10 mm in diameter and an endometrial thickness of at least 5 mm were observed. A pregnancy rate of 12.6% (11/87) per aspiration and 17.4% (11/63) per transfer was obtained. Serum concentrations of oestradiol and inhibin A were evaluated retrospectively. Significantly more pregnancies were obtained in cycles with a detected increase in the concentration of oestradiol from day 3 to the day of aspiration (19% per aspiration) compared with cycles without such an increase (0% per aspiration). A higher pregnancy rate was observed after an increase in inhibin A concentration (24 versus 0%). In conclusion, monitoring the timing of aspiration may potentially improve the developmental potential of immature oocytes. FSH priming did not affect either cleavage rate or embryo development. Shortening the maturation period from 36 to 28 h did not compromise subsequent embryonic development.

Adolescent↗

PubMed1990

Recovery of bovine oocytes from small vesicular follicles for in vitro maturation and fertilization.

Five dairy and four beef breed, mature cows were used as oocyte donors to develop a system of multiple recovery of oocytes for in vitro maturation and fertilization. The animals were alternately treated with either 20 mg of follicle stimulating hormone (FSH) in four equal intramuscular injections or saline at 12 h intervals starting between days 9 and 13 of the oestrous cycle, and the procedure was repeated at three-week intervals for up to four collections. Eighteen collections resulted in the recovery of 124 oocytes from 181 follicles (69%). No serious side-effects were observed. Recovery was equally successful in both breeds and was not reduced in repeat attempts upon the same animal. Treatment with FSH only marginally increased the recovery rate (p less than 0.07) and did not affect the number of follicles aspirated (p greater than 0.05), which varied significantly (p less than 0.05) between cows. From 110 oocytes matured and fertilized in vitro, 70 embryos were recovered after culture in the rabbit oviduct or with trophoblastic vesicles in vitro, of which 30 had cleaved and 5 had progressed to an advanced stage of development. Hormone treatment did not affect zygote development (p greater than 0.05). Four non-surgical transfers of embryos obtained in these studies have resulted in two pregnancies determined ultrasonographically and the birth of a heifer calf. This suggests that the procedure for multiple oocyte recovery is safe and that it can be used successfully for obtaining oocytes for in vitro maturation and fertilization.

Animals↗

PubMed1988

Pregnancies after co-culture of cumulus cells with bovine embryos derived from in-vitro fertilization of in-vitro matured follicular oocytes.

Bovine follicular oocytes surrounded by cumulus cells for more than one-third of their surface were matured, fertilized and developed in vitro utilizing a co-culture system with bovine cumulus cells. Embryos developed into blastocysts were non-surgically transferred to the uteri of cows at Day 6, 7 or 8 (Day 0 = oestrus). Out of 6 recipient cows (19 blastocysts transferred), 3 became pregnant. One of the 3 pregnant cows carried twins. The results of this study demonstrated the viability of embryos obtained from in-vitro maturation of bovine oocytes followed by in-vitro fertilization and culture to the blastocyst stage in vitro.

Animals↗

PubMed2002

Cytogenetic analysis of embryos generated from in vitro matured mouse oocytes reveals an increase in micronuclei due to chromosome fragmentation.

PURPOSE: (i) To determine the prevalence of micronuclei in the cytoplasm of embryos generated from in vitro matured oocytes. (ii) Assess whether micronuclei presence are the result of chromosome fragmentation or the loss of whole chromosomes. METHODS: In vitro fertilization was performed on mature oocytes generated from superovulated mice (control) and in vitro matured mouse oocytes. Fertilized oocytes were cultured to the two-cell stage and fixed to slides. Micronuclei assessment was performed after staining with Giemsa. Centromere assessment was made using immunofluorescent staining (CREST) of the centromeric kinetochores. RESULTS: Micronuclei were observed in 2% (4/197) of control two-cell embryos and 36.2% (46/127) of two-cell embryos generated from in vitro matured oocytes (P < 0.02). Centromeres were not detected in micronuclei from either group. CONCLUSIONS: A significant increase in micronuclei was observed in embryos generated from in vitro matured oocytes. The lack of accompanyingcentromeres would suggest the micronuclei are the result of chromosome fragmentation.

Animals↗

PubMed2002

Delay of nuclear maturation and reduction in developmental competence of pig oocytes after mineral oil overlay of in vitro maturation media.

Steroid hormones, such as progesterone, oestrogen, androgen and meiosis activating sterols, are secreted from cumulus cells that are stimulated by gonadotrophins during maturation of oocytes in vitro. These steroid hormones may be absorbed by mineral oil or paraffin oil; however, in vitro maturation of pig oocytes is commonly performed using medium covered by oil. In this study, high concentrations of progesterone, oestradiol and testosterone were detected in the culture medium after pig cumulus-oocyte complexes (COCs) were cultured with FSH and LH for 44 h in medium without an oil overlay. However, high concentrations of these steroid hormones were not detected in medium when COCs were cultured with the mineral oil overlay. When high concentrations of these steroid hormones were secreted by COCs, germinal vesicle breakdown (GVBD) and the activation of p34(cdc2) kinase and mitogen-activated protein (MAP) kinase in oocytes occurred earlier in comparison with oocytes cultured in medium covered with mineral oil. Moreover, a decrease in p34(cdc2) kinase activity during meiotic progression beyond metaphase I was observed in oocytes cultured in conditions under which high concentrations of steroid hormones were secreted by COCs. In addition, the rate of development to the blastocyst stage after IVF was higher in oocytes matured in medium without an oil overlay. These adverse effects of oil may be explained by absorption by the oil of cumulus-secreted steroids or by the release of toxic compounds into the medium.

Animals↗

PubMed1990

Developmental potential of early bovine zygotes submitted to centrifugation and microinjection following in vitro maturation of oocytes.

This study was designed to investigate the potential use of in vitro matured, in vitro fertilized bovine zygotes for producing transgenic calves by microinjection of foreign DNA. In Experiment 1, the effect of centrifugation (4 min, 15,000 x g, 20 degrees C) on in vitro derived bovine zygotes was evaluated. In vitro development from 2 to 8 cells was not affected (80 vs 78%) when control zygotes (n = 211) were compared with zygotes treated (n = 210) 18 h post insemination. In Experiment 2, the influence of the centrifugation alone on the developmental potential of embryos was evaluated in rabbit oviducts for 120 h. The percentage of control and treated zygotes that developed to 1, 2 to 8, 8 to 32 and more than 32 cells were 7, 54, 10 and 10% vs 7, 40, 11 and 10%, respectively. In Experiment 3, the effect of pronuclear injection with plasmid containing CRF (corticotropin releasing factor) gene or pOCAT 330 Delta 1 plasmids; 2 microg/ml in Tris 10 mM, EDTA 0.2 mM, 18 to 20 h post insemination was evaluated by in vivo development in the rabbit oviduct. The embryos submitted only to centrifugation and vortexing resulted in a morula-blastocyst (> 32 cells) rate of 25% (n = 226) compared with the injected zygotes of which only 5% (n = 206) achieved the same stage. We conclude that in vitro produced bovine zygotes have a reduced developmental potential following microinjection, and this effect is not due to the centrifugation process.

Journal Article↗

PubMed2004

Peroxiredoxin 6 is upregulated in bovine oocytes and cumulus cells during in vitro maturation: role of intercellular communication.

Peroxiredoxins are peroxidases involved in antioxidant defense and intracellular signaling. Expression of transcripts coding for peroxiredoxin 6 (PRDX6) has been previously described to be upregulated in oocytes after in vitro maturation, a period during which general transcription decreases dramatically in oocytes. The aim of the present work was to evaluate PRDX6 regulation in bovine cumulus-oocyte complexes in relation to maturation and intercellular communication. PRDX6 expression was analyzed by reverse transcription-PCR and Western blotting in oocytes and cumulus cells before and after in vitro maturation. PRDX6 was found to be upregulated at the mRNA and protein levels in both cell types after maturation. The effect of paracrine and gap junctional communication on PRDX6 expression was then assessed by culturing cumulus clusters in the presence or absence of denuded oocytes. While PRDX6 upregulation in oocytes required intact cumulus-oocyte junctions, the presence of denuded oocytes was necessary but sufficient for the upregulation to occur in cumulus cells. Finally, the influence of recombinant mouse growth differentiation factor-9 (GDF-9) on PRDX6 expression in cumulus cells was studied. GDF-9 induced cumulus expansion and PRDX6 upregulation in bovine cumulus clusters. Altogether, our data suggest that PRDX6 upregulation in cumulus-oocyte complexes during in vitro maturation is mutually regulated by both cell types: PRDX6 upregulation in oocytes would require gap junctions with cumulus cells, while upregulation in cumulus would depend on secretion of oocyte paracrine factor(s) with GDF-9 being a likely candidate.

Animals↗