Oocyte competence and cumulus cells gene expression

Human Reproduction, 2007

BACKGROUND: Dialogue between the oocyte and cumulus cells is essential for oocyte maturation. A prospective laboratory research project was designed to evaluate transcription of specific genes in cumulus cells harvested before intracytoplasmic sperm injection from pre-ovulatory follicles, according to individual oocyte nuclear maturity and developmental competence. Genes were chosen because their expression was induced by the LH peak [Steroidogenic Acute Regulatory protein (STAR), Cyclooxygenase 2 (COX2 or PTGS2), Amphiregulin (AREG)] or because they were involved in oocyte lipidic metabolism [Stearoyl-Coenzyme A Desaturase 1 and 5 (SCD1 and SCD5)] or in gap-junctions [Connexin 43 (CX43 or GJA1)]. METHODS: mRNA levels in cumulus cells were assessed by real-time PCR. RESULTS: Expression levels of all genes investigated, except Cx43, were increased after resumption of meiosis. Nuclear maturation was thus associated with increased expression of STAR, COX2, AREG, SCD1 and SCD5 by cumulus cells. When considering only cumulus associated with metaphase II oocytes, gene expression was independent of morphological status at Day 2. In contrast, transcript levels were lower and distributed over a narrower range in cumulus enclosing oocytes achieving blastocyst development at Day 5/6 than in cumulus enclosing oocytes unable to develop beyond the embryo stage. CONCLUSION: Further developmental potential from embryo to blastocyst stage was associated with lower expression in a narrow range for these genes.

Fertility and Sterility, 2007

BACKGROUND: Dialogue between the oocyte and cumulus cells is essential for oocyte maturation. A prospective laboratory research project was designed to evaluate transcription of specific genes in cumulus cells harvested before intracytoplasmic sperm injection from pre-ovulatory follicles, according to individual oocyte nuclear maturity and developmental competence. Genes were chosen because their expression was induced by the LH peak [Steroidogenic Acute Regulatory protein (STAR), Cyclooxygenase 2 (COX2 or PTGS2), Amphiregulin (AREG)] or because they were involved in oocyte lipidic metabolism [Stearoyl-Coenzyme A Desaturase 1 and 5 (SCD1 and SCD5)] or in gap-junctions [Connexin 43 (CX43 or GJA1)]. METHODS: mRNA levels in cumulus cells were assessed by real-time PCR. RESULTS: Expression levels of all genes investigated, except Cx43, were increased after resumption of meiosis. Nuclear maturation was thus associated with increased expression of STAR, COX2, AREG, SCD1 and SCD5 by cumulus cells. When considering only cumulus associated with metaphase II oocytes, gene expression was independent of morphological status at Day 2. In contrast, transcript levels were lower and distributed over a narrower range in cumulus enclosing oocytes achieving blastocyst development at Day 5/6 than in cumulus enclosing oocytes unable to develop beyond the embryo stage. CONCLUSION: Further developmental potential from embryo to blastocyst stage was associated with lower expression in a narrow range for these genes.

Animal Genetics, 2016

Cumulus cells (CCs) have an important role during oocyte growth, competence acquisition, maturation, ovulation and fertilization. In an attempt to isolate potential biomarkers for bovine in vitro fertilization, we identified genes differentially expressed in bovine CCs from oocytes with different competence statuses, through microarray analysis. The model of follicle size, in which competent cumulus-oocyte complexes (COCs) were recovered from bigger follicles (≥8.0 mm in diameter) and less competent ones from smaller follicles (1-3 mm), was used. We identified 4178 genes that were differentially expressed (P < 0.05) in the two categories of CCs. The list was further enriched, through the use of a 2.5-fold change in gene expression as a cutoff value, to include 143 up-regulated and 80 downregulated genes in CCs of competent COCs compared to incompetent COCs. These genes were screened according to their cellular roles, most of which were related to cell cycle, DNA repair, energy metabolism, metabolism of amino acids, cell signaling, meiosis, ovulation and inflammation. Three candidate genes up-regulated (FGF11, IGFBP4, SPRY1) and three down-regulated (ARHGAP22, COL18A1 and GPC4) in CCs from COCs of big follicles (≥8.1 mm) were selected for qPCR analysis. The selected genes showed the same expression patterns by qPCR and microarray analysis. These genes may be potential genetic markers that predict oocyte competence in in vitro fertilization routines.

Reproduction, 1993

The expansion of the mouse cumulus oophorus in vitro in response to FSH is dependent upon the presence of an enabling factor secreted by the oocyte. The purpose of this study was to determine whether the expansion of cumulus cells from rats and pigs were similarly dependent upon an oocyte-secreted enabling factor. Mouse and rat oocyte\p=n-\cumulus cell complexes were isolated from pregnant mares' serum gonadotrophin (PMSG)-stimulated animals; pig oocyte\p=n-\cumulus cell complexes with the attached piece of mural granulosa were obtained from either prepubertal gilts or cyclic sows. FSH (25\p=n-\1000 ng ml \m=-\1) or dibutyryl cyclic adenosine monophosphate (dbcAMP; 0.05\p=n-\2mmol 1\ m=-\ 1) induced a dose-dependent expansion of the oocyte\p=n-\cumuluscomplexes from rats and pigs. The hypothesis that the oocyte plays a role in the regulation of cumulus expansion was tested by microsurgically removing oocytes from oocyte\p=n-\cumulus complexes and the oocytectomized complexes were tested for their ability to undergo expansion in response to FSH. FSH did not induce cumulus expansion in oocytectomized mouse complexes; however, expansion occurred in rat and pig oocytectomized complexes. The pieces of mural granulosa, detached from the pig complexes, also expanded in response to FSH stimulation. Rat and pig oocytectomized complexes were then held in culture for up to 48 h before stimulation by FSH. The degree of expansion in rat oocytectomized complexes decreased as the delay before FSH stimulation increased such that, with an 8 h delay, oocytectomized complexes did not expand. Pig oocytectomized complexes expanded fully even with a 32 h delay before FSH stimulation, and in response to dbcAMP or epidermal growth factor (EGF). Finally, when rat or mouse oocytectomized complexes were cocultured with germinal vesicle-stage mouse, rat or pig oocytes, FSH stimulated expansion by all oocytectomized complexes. These results indicate that a factor(s) secreted by mouse and rat oocytes is necessary for the cumulus cells to undergo expansion in response to FSH, EGF or dbcAMP. Pig oocytes can secrete a cumulus expansion-enabling factor, but expansion of pig complexes does not depend upon this factor.

2013

Human Reproduction, 2010

enclosed oocyte, was recorded. To assess meiotic competence, oocytes were removed from follicles, cultured overnight, and the number that underwent germinal vesicle breakdown and reached metaphase II was recorded. Mitochondrial DNA (mtDNA) in individual oocytes was quantified using real-time PCR. Expression of Kit ligand (KL)-1 and -2 by granulosa cells were assayed using real-time RT-PCR. results: Wild-type and mutant mice possessed similar number of primary follicles. However, the mutants possessed fewer secondary and pre-antral follicles than wild-type litter-mates, and no large antral follicles. Oocytes of mutant mice grew to the same size as those of wild-type mice, however, and were able to complete maturation in vitro to metaphase II. Moreover, they contained the same quantity of mtDNA. Expression of KL-1 and KL-2 decreased in the granulosa surrounding fully grown oocytes, consistent with previous reports. However, although FSH can regulate KL expression in vitro, there was no difference between wild-type and mutant oocytes either in the amplitude of the decrease or in the ratio of KL-1:KL-2. conclusion: By the criteria so far examined, oocytes develop normally in vivo in the absence of FSH. Future work will test whether such oocytes can give rise to normal offspring.

Human Reproduction, 2006

The understanding of the mechanisms regulating human oocyte maturation is still rudimentary. We have identified transcripts differentially expressed between immature and mature oocytes, and cumulus cells.

Abstract An experimental design was framed to analyse the effect of cumulus oocyte complex (COC) morphology on in vitro maturation of bovine oocytes. Slaughter house derived bovine ovaries from South Indian breeds and crossbred cattle of Kerala were subjected to three retrieval methods to yield different quality grades of oocytes. Based on the number of layers of cumulus cells and ooplasm character, the oocytes were graded into four classes from A to D. Each grade of oocytes obtained through different retrieval methods were incubated at 38.5°C with 5% carbondioxide tension and maximum humidity for 24 h in TCM-199 medium supplemented with LH, FSH, estradiol, pyruvate and foetal calf serum. Maturation changes were assessed by cumulus expansion, formation of M II plates and polar body extrusion. Oocytes with more than three layers of cumulus cells exhibited maximum maturation rate irrespective of their retrieval method. The experiments revealed that COC morphology has a very significant role in maturation of bovine oocytes.

Reproductive BioMedicine Online, 2009

Meryem Filali obtained her degree in pharmaceutical biology in 2006 from University of Paris V, France. She completed her residency in the IVF programme at the Clamart Hospital in Paris, France between 2004 and 2006, where she is currently working. Her main areas of interest are oocyte maturation and cumulus gene expression with the intention of improving efficiency of assisted reproductive techniques.

PLoS ONE, 2012

Background: Single embryo transfer (SET) is the most successful way to reduce the frequency of multiple pregnancies following in vitro fertilisation. However, selecting the embryo for SET with the highest chances of pregnancy remains a difficult challenge since morphological and kinetics criteria provide poor prediction of both developmental and implantation ability. Partly through the expression of specific genes, the oocyte-cumulus interaction helps the oocyte to acquire its developmental competence. Our aim was therefore to identify at the level of cumulus cells (CCs) genes related to oocyte developmental competence. Methodology/Principal Findings: 197 individual CCs were collected from 106 patients undergoing an intra-cytoplasmic sperm injection procedure. Gene expression of CCs was studied using microarray according to the nuclear maturity of the oocyte (immature vs. mature oocyte) and to the developmental competence of the oocyte (ability to reach the blastocyst stage after fertilisation). Microarray study was followed by a meta-analysis of the behaviour of these genes in other datasets available in Gene Expression Omnibus which showed the consistency of this list of genes. Finally, 8 genes were selected according to oocyte developmental competence from the 308 differentially expressed genes (p,0.0001) for further validation by quantitative PCR (qPCR). Three of these 8 selected genes were validated as potential biomarkers (PLIN2, RGS2 and ANG). Experimental factors such as inter-patient and qPCR series variability were then assessed using the Generalised Linear Mixed Model procedure, and only the expression level of RGS2 was confirmed to be related to oocyte developmental competence. The link between biomarkers and pregnancy was finally evaluated and level of RGS2 expression was also correlated with clinical pregnancy. Conclusion/Significance: RGS2, known as a regulator of G protein signalling, was the only gene among our 8 selected candidates biomarkers of oocyte competence to cover many factors of variability, including inter-patient factors and experimental conditions.