Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cumulus Cells”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed2002

Mitogen-activated protein kinase activity in cumulus cells is essential for gonadotropin-induced oocyte meiotic resumption and cumulus expansion in the mouse.

This study investigated the participation of MAPK in the resumption of meiosis [germinal vesicle breakdown (GVB)] in oocytes and cumulus expansion using oocyte-cumulus cell complexes (OCC) from Mos-null mice (Mos(tm1Ev)/Mos(tm1Ev), hereafter Mos(-/-)). MAPK activity was not detected in Mos(-/-) oocytes whether they matured in vivo or in vitro, with or without gonadotropin stimulation. Therefore, there are no pathways independent of MOS that activate MAPK during gonadotropin-induced maturation. In contrast, MAPK activity was always detected coincident with GVB in Mos(+/+) oocytes. Moreover, MAPK activity was detected in cumulus cells before gonadotropin-induced GVB in OCC regardless of genotype. A specific inhibitor (U0126) of MEK, a MAPKK required for MAPK activity, inhibited gonadotropin-induced GVB in OCC of both Mos(+/+) and Mos(-/-) mice. Activation of MAPK was downstream of elevation of cAMP. U0126 also inhibited cumulus expansion stimulated by FSH, epidermal growth factor, 8-bromo-cAMP, and recombinant growth differentiation factor-9. It is concluded that under the in vitro conditions used here, gonadotropin-induced GVB requires the participation of MAPK activity in the cumulus cells, but not in the oocyte. Moreover, the induction of cumulus expansion also requires the participation of MAPK, and this action is downstream of both elevation of cAMP and growth differentiation factor-9.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2005

Effect of serum and cumulus cell expansion on marker gene transcripts in bovine cumulus-oocyte complexes during maturation in vitro.

OBJECTIVE: To determine the distribution of transcripts encoding the FSH receptor (FSHr), LH receptor (LHr), connexin 43 (Cx43), cyclooxygenase-2 (COX-2), and prostaglandin E(2) receptors 2 and 3 (EP2 and EP3) within bovine cumulus-oocyte complexes (COCs) and denuded oocytes and investigate the influence of gonadotropins, serum, and cumulus cell expansion on the abundance of transcripts encoding these genes. DESIGN: Prospective controlled animal study. SETTING: University research laboratory. PATIENT(S): Animal models for human studies. INTERVENTION(S): Cumulus-oocyte complexes were treated in culture with serum and gonadotropin-supplemented media to examine the effects to mRNA transcript levels. MAIN OUTCOME MEASURE(S): Variation in mRNA transcript levels. RESULT(S): Luteinizing hormone receptor, FSHr, and EP3 mRNAs were detected in intact COCs and not in cumulus cell-denuded oocytes, whereas Cx43, COX-2, and EP2 mRNAs were found in both COCs and oocytes. The relative abundance of marker gene mRNAs did not vary in media containing no additives or FSH alone, independent of whether the media induced cumulus cell expansion. However, the presence of serum in maturation media significantly decreased expression of all mRNAs except LHr. CONCLUSION(S): The relative abundance of COC mRNAs is altered by serum in the maturation medium, which may signify long-term consequences for embryonic development.

Animals↗
PubMed2004

Expression of two progesterone receptor isoforms in cumulus cells and their roles during meiotic resumption of porcine oocytes.

The present study aimed to investigate progesterone receptor (PR) gene expression in cumulus cells and their roles during meiotic resumption of porcine oocytes. The amount of PR-A or PR-B mRNA was analyzed by RT-PCR using primer sets for the PR-B region or the PR-A/B common region. The level of PR-B mRNA in cumulus cells was up-regulated by FSH and LH during the first 8 h of cultivation but the level significantly decreased at 12 h. However, a high level of total PR mRNA was maintained up to a cultivation period of 20 h. The level of PR-B protein in cumulus cells reached its maximum at 4 to 12 h, whereas PR-A predominated in cumulus cells of cumulus-oocyte complexes (COCs) at 20 h. Accompanying the shift in expression of PR isoforms, progesterone production in cumulus cells was significantly increased, and both the proliferative activity of cumulus cells during a 10- to 20-h cultivation period and the level of connexin-43, a major component of the gap junction, in cumulus cells significantly decreased. When COCs were cultured with FSH and LH for 10 h and then further cultured with additional RU486, there was a significant suppression in the shift in PR isoforms and in progesterone production, a loss of proliferative activity, and a decrease in connexin-43 mRNA in cumulus cells. Moreover, treatment with RU486 after 10-h cultivation of COCs inhibited the meiotic resumption of oocytes and cumulus cell expansion. These results suggest that the induction of PR isoforms in cumulus cells and their binding to progesterone appear to impact on proliferation and differentiation in a time-dependent manner, and the shift from PR-B to PR-A may help mediate certain events.

Animals↗
PubMed2001

Dynamic changes of connexin-43, gap junctional protein, in outer layers of cumulus cells are regulated by PKC and PI 3-kinase during meiotic resumption in porcine oocytes.

Mammalian oocytes are surrounded by numerous layers of cumulus cells, and the loss of gap junctional communication in the outer layers of cumulus cells induces meiotic resumption in oocytes. In this study, we investigated the dynamic changes in the gap junctional protein connexin-43 in cumulus cells during the meiotic resumption of porcine oocytes. The amount of connexin-43 in all layers of cumulus cells recovered from cumulus-oocyte complexes was increased after 4-h cultivation. However, at 12-h cultivation, the positive signal for connexin-43 immunoreactivity was markedly reduced in the outer layers of cumulus cells. When these reductions of connexin-43 were blocked by protein kinase C (PKC) or phosphatidylinositol (PI) 3-kinase inhibitor, networks of filamentous bivalents (i.e., advanced chromosomal status) were undetectable in the germinal vesicle of the oocyte. After 28-h cultivation, when the majority of oocytes were reaching the metaphase I (MI) stage, the connexin-43 in the inner layers of cumulus cells was phosphorylated, regardless of mitogen-activated protein (MAP) kinase activation. These results suggest that the initiation of meiotic resumption, namely, the formation of networks of filamentous bivalents in germinal vesicle, is associated with the reduction of gap junctional protein connexin-43 in the outer layers of cumulus cells via the PKC and/or PI 3-kinase pathway. Moreover, the connexin-43 in the inner layers of cumulus cells is phosphorylated during meiotic progression beyond the MI stage, regardless of MAP kinase activation in cumulus cells surrounding the oocyte.

Animals↗
PubMed2003

Phosphatidylinositol 3-kinase in cumulus cells is responsible for both suppression of spontaneous maturation and induction of gonadotropin-stimulated maturation of porcine oocytes.

In this study, we investigated the mechanisms of protein kinase B (PKB) activation and its role in cumulus cells during in vitro meiotic resumption of porcine oocytes. PKB activity in cumulus cells was significantly decreased by 12 h cultivation of cumulus-oocyte complexes (COCs) in basic medium. However, the addition of phosphodiesterase inhibitors, hypoxanthine or 3-isobutyl-1-methylxanthine, maintained the level of PKB activity in cumulus cells at comparable with that in cumulus cells just after collection from their follicles. When COCs were cultured with phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, LY294002, PKB activity was significantly decreased, and both caspase 3 activity and the proportion of apoptotic cells were significantly increased as compared with those in cumulus cells just after collection from their follicles. Moreover, the inhibitory effect of hypoxanthine on spontaneous meiotic resumption was overcome by addition of LY294002. On the other hand, markedly high activity of PKB and high intensity of the phosphorylated PKB band were observed in cumulus cells of COCs which were cultured with FSH. The addition of 20 microM LY294002 to FSH-containing medium induced an apoptosis of cumulus cells, whereas little apoptotic-positive signal was detected in COCs cultured with 5 microM LY294002 and FSH. However, the inhibitory effects of LY294002 on progesterone production by cumulus cells and germinal vesicle breakdown in oocytes reached a maximum at 5 microM. Thus, high activity of the PI 3-kinase-PKB pathway in cumulus cells plays an important role in FSH regulation of cell function. Judging from these results, it is estimated that PI 3-kinase in cumulus cells is required for both the suppression of spontaneous meiotic resumption and the induction of gonadotropin-stimulated meiotic resumption.

Animals↗
PubMed1994

Effects of cumulus cells on sperm penetration of bovine oocytes in protein-free medium.

The present study was conducted to examine the effects of cumulus cells on sperm capacitation, acrosome reaction and penetration of bovine oocytes in vitro in a protein-free medium. In vitro matured oocyte-cumulus complexes (OCCs) and denuded oocytes were co-incubated with spermatozoa in the medium with or without bovine serum albumin (BSA). Higher fertilization rates were obtained in the OCCs (92 and 89%, respectively) than denuded oocytes (57 and 6%, respectively) in the medium with or without BSA (P<0.01). Higher proportion of the denuded oocytes were fertilized in the medium with BSA (57%) than without BSA (6%; P<0.01). These results suggest that the cumulus cells are more effective for increasing fertilization rate than BSA (P<0.05). Both the percentages of capacitated and acrosome-reacted spermatozoa incubated for 4 h with isolated cumulus cells were not significantly different in the medium without cumulus cells in the presence or absence of BSA. The denuded oocytes were inseminated with isolated cumulus cells taken from OCCs matured with or without hormones, follicle stimulating hormone (FSH) and estradiol-17beta (E(2)), and from immature OCCs in a protein-free medium. Presence of the cumulus cells matured with hormones enhanced sperm penetration of denuded oocytes more effectively (81%) than either of the cells matured without hormones (41%) or the immature cells (26%; P<0.01). The conditioned medium of cumulus cells matured with hormones was not effective for sperm penetration of denuded oocytes (2%), while a high proportion (82%) of the oocytes were fertilized when they were inseminated with isolated cumulus cells (P<0.01). In conclusion, the presence of cumulus cells matured with FSH and E(2) was effective for sperm penetration but not for sperm capacitation or acrosome reaction.

Journal Article↗
PubMed1984

Ultrastructure of the cumulus cell mass surrounding a human egg in the pronuclear stage.

The cumulus cell mass enclosing a penetrated human egg was studied. The egg, recovered from the Fallopian tube approximately 80 h after luteinizing hormone peak and 35 h after insemination, was surrounded by a large, expanded and dissociated cumulus. Dispersions of the outermost cumulus cell layers occurred during processing, the innermost cell layers remained attached enclosing the egg. The photomicrographs showed that the follicular cells were embedded in an intercellular matrix and contact via gap-junction-like structures between neighboring cells existed. Cumulus cell processes traversing the zona pellucida were not found. Two types of follicular cells coexisted within the cumulus, light and dark cells. These cellular types, were different in morphology and size. Light cells displayed cytoplasmic organelles normally associated with protein synthesis and steroidogenesis. Dark cells with long cytoplasmic processes were involved in sperm phagocytosis. It is suggested from the characteristics of the cytoplasmic organelles that dark cells seem to be modified light follicular cells.

Female↗
PubMed2005

Effect of the removal of cumulus cells on the nuclear maturation, fertilization and development of porcine oocytes.

The present study was conducted to investigate the effects of attachment of cumulus cells to porcine oocytes during the process of maturation and fertilization on the nuclear maturation, fertilization and subsequent development after in vitro fertilization (IVF). In the first experiment, the cumulus cells were removed from cumulus-oocyte complexes (COCs) at 0, 24 and 42 h after the onset of maturation culture and were then cultured until reaching 42 h of cultivation. In the second experiment, COCs were denuded as described in the first experiment, then fertilized and cultured for 7 days. As a control, cumulus cells were allowed to maintain attachment to the oocytes until the end of IVF. The proportion of oocytes reaching metaphase II significantly increased with the delay in the removal treatment of cumulus cells. The proportion of normal fertilization gradually increased with delay in the removal treatment of cumulus cells from COCs until the end of IVF. However, no significant difference in the proportion of normal fertilization was found between the 42-h and control groups. The removal treatment of cumulus cells in the 0- and 24-h group significantly (p < 0.05) decreased the proportion of cleaved embryos when compared with the control, and none of them developed to the blastocyst stage. The proportion of development to the blastocyst stage was significantly higher (p < 0.05) in the control group than in the 42-h group (18.1% vs 12.4%; p < 0.05). The present study indicates that the attachment of cumulus cells to the oocyte during maturation and fertilization is important to support oocyte nuclear maturation, fertilization and subsequent embryo development. Particularly, the attachment of cumulus cells to the oocyte during IVF promotes embryonic development.

Animals↗
PubMed1996

Beneficial effects of coculture with cumulus cells on blastocyst formation in a prospective trial with supernumerary human embryos.

PURPOSE: We reported previously on the use of coculture with cumulus cells in insemination medium for the development of human embryos in vitro. Here we describe a prospective trial to determine if this procedure has a significant beneficial effect. METHODS: On the day after insemination, zygotes were randomized for culture in either a fresh drop of medium without (- cum) or were left in their insemination drop with (+ cum) cumulus cells. Embryos with the best morphological quality were replaced on the third day of development at the eight-cell stage. The remaining embryos were cultured for a further 3 days and cryopreserved if they reached the fully expanded blastocyst (FEB) stage. Three different culture media were used over the period of this study. RESULTS: In 11 patients, supernumerary embryos were available only for continued culture in +cum and three patients had embryos cultured in only -cum. Thirty-nine other patients had embryos assigned to both +cum and -cum treatments. In the +cum group, 98 blastocysts developed from 216 embryos cultured for 6 days (45%), and this was significantly greater (P < 0.01) than the 48 blastocysts from 156 embryos (31%) developing in the absence of cumulus cells. In basal HTF medium (HTF medium with EDTA and glutamine) and basal XI HTF medium (similar to basal HTF but devoid of glucose and phosphate), culture of embryos with cumulus cells produced significantly more FEBs than in the absence of cumulus cells. There was no significant difference between the two culture treatments when regular HTF medium was used. Preliminary results indicate that pronectin-coated dishes provide a good substratum for cumulus cell attachment and embryo development. CONCLUSIONS: The culture of human embryos with their cumulus cells in insemination drops of medium produces a significantly greater proportion of FEBs than when the zygotes are transferred to fresh culture drops devoid of cumulus cells. This is the first report of a significantly higher blastocyst rate with coculture in which a real comparison has been made between two culture treatments which differ only in the presence or absence of homologous cumulus cells in insemination drops.

Blastocyst↗
PubMed1983

Freeze-fracture observations of ovulated hamster oocytes with their cumulus cells.

Mature unfertilized oocytes in the cumulus oophorus were examined using the freeze-fracture technique. The P face of the oocyte plasma membrane (oolemma) has randomly distributed intramembranous particles (IMPs) with an average diameter of about 10 nm. No marked difference is found between the intermicrovillous and microvillous regions of the oocyte with respect to the size and distribution of IMPs. The E face of the oolemma has fewer IMPs than the P face. The intermicrovillous region is slightly elevated in some places because of close contact with underlying cortical granules. The oolemma of this elevated region and the membrane of the cortical granule have IMPs which are considerably smaller than those in the remaining areas of the oolemma. The IMP density of the P face of the cortical granule membrane is much lower than that of the E face, possibly indicating a membrane specialization required for fusion of the cortical granule membrane with the overlying oolemma at the time of exocytosis. Cytoplasmic lamellae appear as parallel bands of particles in freeze-fractured specimens. No gap junctions are found between the oocyte and cumulus cells, but residual gap junctions are seen among clustered cumulus cells.

Animals↗
PubMed1988

Gonadotropin-induced murine oocyte maturation in vivo is not associated with decreased cyclic adenosine monophosphate in the oocyte-cumulus cell complex.

The cyclic adenosine monophosphate (cAMP) content of intact oocyte-cumulus cell complexes at various times after the induction of oocyte maturation in mice in vivo was correlated with the time of commitment by the oocytes to undergo germinal vesicle breakdown (GVB) and metabolic coupling between the oocyte and cumulus cells. Seventy-nine percent of the oocytes either underwent GVB or were committed to do so by 2 h after injection of human chorionic gonadotropin (hCG). This occurred without a decrease in the coupling between cumulus cells and the oocyte and with increasing cAMP levels in the oocyte-cumulus cell complex. Maintenance of threshold levels of cAMP within mammalian oocytes appears essential for the maintenance of meiotic arrest, but data presented here suggest that oocyte maturation in mice is induced by gonadotropins in nonatretic follicles in vivo by some mechanism other than one which decreases the cAMP content of the intact oocyte-cumulus cell complex.

Animals↗
PubMed2003

Protein kinase C and mitogen-activated protein kinase cascade in mouse cumulus cells: cross talk and effect on meiotic resumption of oocyte.

Protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) in cumulus cells are involved in FSH-induced meiotic resumption of cumulus-enclosed oocytes (CEOs), but their regulation and cross talk are unknown. The present experiments were designed to investigate 1) the possible involvement of MAPK cascade in PKC-induced meiotic resumption; 2) the regulation of PKC on MAPK activity in FSH-induced oocyte maturation; and 3) the pattern of PKC and MAPK function in induced meiotic resumption of mouse oocytes. PKC activators, phorbol 12-myristate 13-acetate (PMA) and 1-oleoyl-2-acetyl-sn-glycerol (OAG), induced the meiotic resumption of CEOs and activation of MAPK in cumulus cells, whereas this effect could be abolished by PKC inhibitors, calphostin C and chelerythrine, or MEK inhibitor U0126. These results suggest that PKC might induce the meiotic reinitiation of CEOs by activating MAPK in cumulus cells. Both PKC inhibitors and U0126 inhibited the FSH-induced germinal vesicle breakdown (GVBD) of oocytes and MAPK activation in cumulus cells, suggesting that PKC and MAPK are involved in FSH-induced GVBD of mouse CEOs. Protein synthesis inhibitor cycloheximide (CHX) inhibited FSH- or PMA-induced oocyte meiotic resumption, but not the MAPK activation in cumulus cells. FSH and PKC activators induced the GVBD in denuded oocytes cocultured with cumulus cells in hypoxanthine (HX)-supplemented medium, and this effect could be reversed by U0126. Thus, when activated by FSH and PKC, MAPK may stimulate the synthesis of specific proteins in cumulus cells followed by secretion of an unknown positive factor that is capable of inducing GVBD in oocytes.

Animals↗
PubMed2005

Studies of gene expression in human cumulus cells indicate pentraxin 3 as a possible marker for oocyte quality.

OBJECTIVE: To search for differentially expressed genes in cumulus cells from two groups of oocytes with different developmental outcome in vitro. DESIGN: Analyses of gene expression in human cumulus cells from oocytes that failed to fertilize in vitro (group A) and those that developed into normal-appearing embryos on day 3 (group B). SETTING: University-based facilities for clinical service and research. PATIENT(S): Women undergoing IVF treatment for infertility. INTERVENTION(S): Cumulus cells were collected from oocytes that were aspirated from ovarian follicles for IVF. The oocytes were cultured individually for IVF and embryo development. Total RNA was extracted from the cumulus cells for gene expression analyses. MAIN OUTCOME MEASURE(S): General gene expression profiles and relative abundance of pentraxin 3 (Ptx3) mRNA. RESULT(S): DNA microarray analysis identified 160 genes, including Ptx3, that were differentially expressed between cumulus cells in group A and group B. Quantitative analysis confirmed that the relative abundance of Ptx3 mRNA in cumulus cells was highly associated with oocyte development. CONCLUSION(S): This study demonstrated that changes in the expression levels of 160 genes, including particularly Ptx3, in human cumulus cells may be indicative of the quality of their enclosed oocyte.

Biomarkers↗
PubMed1990

Protein synthesis and acrosome reaction-inducing activity of human cumulus cells.

The acrosome reaction of human spermatozoa is a prerequisite to fertilization. It has been hypothesized that secretions of cumulus cells could be involved in the induction of this sperm reaction. A source of variation in the in-vitro fertilization of human oocytes could be the maturational differences in the cumulus cells which affect the acrosome reaction. In order to investigate this possibility, we have studied the capability of secretions obtained from cumulus cells of different maturational stages to induce the acrosome reaction. Capacitated spermatozoa were exposed to the culture medium containing cumulus cell secretions and their acrosomal status was evaluated using the triple stain technique. The maturational status of the cumulus or fertilization of the enclosed oocyte did not influence the percentage of acrosome-reacted live spermatozoa. In order to further document these observations, cumulus cells were submitted to [35S]methionine incorporation and total and secreted proteins were analysed by SDS-PAGE electrophoresis. Neither quantitative nor qualitative changes were detected in the electrophoretic patterns of the proteins obtained from cumulus cells of different maturational status. Thus, variation of the acrosome reaction-inducing activity of cumulus cells does not appear to be involved in the variable fertilization of oocytes obtained from follicles of differing maturity.

Acrosome↗
PubMed1999

Production of plasminogen activators (PAs) in bovine cumulus-oocyte complexes during maturation in vitro: effects of epidermal growth factor on production of PAs in oocytes and cumulus cells.

We examined whether plasminogen activators (PAs) are produced by bovine cumulus-oocyte complexes (COCs) during maturation in vitro. The effects of epidermal growth factor (EGF) on production of PAs in oocytes and cumulus cells were also examined. When COCs were cultured for 24 h with 30 ng/ml EGF, three plasminogen-dependent lytic zones (58.5 +/- 3.5 kDa, 79.0 +/- 3.0 kDa, and 113.5 +/- 6.5 kDa) were observed. Addition of amiloride, a competitive inhibitor of urokinase-type PA (uPA), to the zymogram eliminated the activity of the 58.5 +/- 3.5-kDa zone, suggesting that this band is a uPA. However, since the activity of the remaining two bands was not eliminated, it was suggested that the 79.0 +/- 3.0-kDa band is a tissue-type PA (tPA) and the 113.5 +/- 6.5-kDa band is possibly a tPA-PA inhibitor (tPA-PAI) complex. In COCs before culture, however, no activity of PAs was detected. At 6 h of culture, the same level of uPA activity was detected in COCs cultured both in the absence and in the presence of EGF. The uPA activity was increased at 12 h of culture but without further increase at 24 h of culture, with higher activity in the presence than in the absence of EGF. The activity of tPA and tPA-PAI was first detected at 24 h of culture in the absence of EGF. In the presence of EGF, however, some activity of tPA-PAI was detected at 12 h of culture. At 24 h of culture, the activity of all PAs was detected in cumulus cells, but only uPA activity was detected in oocytes, with higher activity in the presence than in the absence of EGF. The uPA activity in oocytes was not detected when they were cultured without cumulus cells in either the presence or absence of EGF, although cumulus expansion was stimulated by EGF, exhibiting a time-course similar to that observed in PA production. These results suggest that uPA, tPA, and tPA-PAI are all produced by bovine COCs, but only uPA by oocytes, during maturation in vitro. However, cumulus cells play an essential role or roles in the production of uPA by oocytes, and EGF enhances the roles of cumulus cells.

Amiloride↗
PubMed1995

Cumulus cell function during bovine oocyte maturation, fertilization, and embryo development in vitro.

Several contemporary micromanipulation techniques, such as sperm microinjection, nuclear transfer, and gene transfer by pronuclear injection, require removal of cumulus cells from oocytes or zygotes at various stages. In humans, the cumulus cells are often removed after 15-18 hr of sperm-oocyte coincubation to assist the identification of the fertilization status. This study was designed to evaluate the function of cumulus cells during oocyte maturation, fertilization, and in vitro development in cattle. Cumulus cells were removed before and after maturation and after fertilization for 0, 7, 20, and 48 hr. The cumulus-free oocytes or embryos were cultured either alone or on cumulus cell monolayers prepared on the day of maturation culture. Percentages of oocyte maturation, fertilization, and development to cleavage, morula, and blastocyst stages and to expanding or hatched blastocysts were recorded for statistical analysis by categorical data modeling (CATMOD) procedures. Cumulus cells removed before maturation significantly reduced the rate of oocyte maturation (4-26% vs. 93-96%), fertilization (0-9% vs. 91-92%), and in vitro development at all stages evaluated. Cumulus cells removed immediately prior to in vitro fertilization (IVF) or 7 hr after IVF reduced the rates of fertilization (58-60% and 71%, respectively, vs. 91-92% for controls), cleavage development (40-47% and 53-54% vs. 74-78% for controls), and morula plus blastocyst development (15% and 24% vs. 45%, P < 0.05). Cumulus cell co-culture started at various stages had no effect on fertilization and cleavage development but significantly improved rates of embryo development to morula or blastocyst stages (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Influence of oocyte-secreted factors and culture duration on the metabolic activity of bovine cumulus cell complexes.

Intracellular communication between the cumulus cell complex and the oocyte is essential for numerous processes during oocyte maturation. The aim of this study was to determine the interaction between oocyte-secreted factors and the metabolic activity of bovine cumulus cell complexes during in vitro maturation (IVM). Cumulus-oocyte complexes (COCs) were aspirated from ovaries derived from an abattoir and divided into four treatment groups: (i) intact COCs, (ii) oocytectomized complexes (OOX), in which the ooplasm was microsurgically removed, (iii) OOX co-cultured with denuded oocytes (OOX+DO) and (iv) DO. The complexes were cultured individually in IVM media. After 0-4, 10-14 and 20-24 h of culture, the utilization of oxygen, glucose, pyruvate and L-lactate by the complexes was measured. The metabolic activity of the DO was undetectable. There were no significant differences in metabolic measurement among any of the treatment groups, indicating that the metabolism of the cumulus complex is not affected by the presence of the oocyte. When metabolic activity for the complexes was analysed relative to time in culture, there was an approximate twofold increase in the consumption of oxygen, glucose and pyruvate over the 24 h period (P<0.05), although production of L-lactate remained constant. The relationship between total glucose uptake and L-lactate production indicated that the majority of glucose consumed at the start of culture was being utilized via glycolysis, but by the cessation of the maturation period, there was significant utilization of glucose elsewhere, possibly for the formation of cumulus extracellular matrix. These results indicate that metabolism of COC does not reflect biochemical activity of the oocyte. Nevertheless, the metabolic requirements of the COC increase throughout maturation.

Animals↗
PubMed2026

Cumulus cells enhance oocyte genomic quality control by promoting DNA damage-induced meiotic arrest.

Cumulus cells are known to maintain oocyte arrest at prophase I through gap junction-mediated cAMP signalling, but their role after meiotic resumption remains unclear. Here, we show that cumulus cells enhance oocyte genomic quality control by sensitizing mouse oocytes to DNA damage-induced meiotic arrest. Time-lapse imaging of SiR-tubulin-labelled spindles revealed that oocytes from cumulus-oocyte complexes (COCs) matured faster than denuded oocytes (DOs). Upon mild DNA damage induced by low-dose etoposide, COC oocytes arrested at metaphase I, whereas DOs completed maturation despite similar levels of DNA lesions. This arrest required spindle assembly checkpoint (SAC) activity, as reversine rescued polar body extrusion and BubR1 and Mad2 were elevated in COCs but not DOs. Disruption of gap junctions or inhibition of mTOR signalling abolished the checkpoint response. Notably, cumulus cells did not enhance oocyte response to minor spindle perturbations. These findings reveal a previously unrecognized role of cumulus cells in mediating DNA damage-induced SAC activation, providing post-GVBD genomic surveillance beyond prophase I arrest.

Animals↗