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Age-associated changes in bovine oocytes and granulosa cell complexes collected from early antral follicles.

ABSTRACT: PURPOSE: To assess the age-associated changes in oocytes and granulosa cells derived from early antral follicles (EAFs). METHOD: Gene expression analysis of granulosa cells of the EAFs using a genome analyzer (Illumina) and in vitro culture of oocyte-granulosa cell complexes (OGCs) of EAFs (400-700 ?m in diameter) collected from ovaries of aged (>120 months) and young (<50 months) cows. RESULTS: Gene expression profiles in granulosa cells of EAFs of aged cows, which included changes in genes that encode chaperone proteins and antioxidants. In vivo development of EAFs, as determined by oocyte diameter of EAFs and AFs (3-6 mm in diameter), appeared to be impaired in aged cows and the OGCs of aged cows contained low GSH compared to younger counterparts. When the OGCs were cultured in a medium containing low estradiol (E2, 0.1 ?g/mL), the ratio of antrum formation was higher for OGCs from aged animals than that from young animals, while higher abnormal fertilization rate and lower total cell number of the blastocysts were observed in the OGCs of aged cows compared with those of young cows. On the contrary, when the OGCs were cultured in a medium containing 10 ?g/mL E2, the ratio of antrum formation and fertilization outcome was comparable between the two age groups, whereas the total cell number of the blastocysts was still low in the aged group. CONCLUSION: Aging affects the gene expression profiles of the granulosa cells, and impairs in vitro developmental ability of OGCs collected from EAFs.

SUBMITTER: Itami N

PROVIDER: S-EPMC4130926 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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Age-associated changes in bovine oocytes and granulosa cell complexes collected from early antral follicles.

Itami N N Kawahara-Miki R R Kawana H H Endo M M Kuwayama T T Iwata H H

Journal of assisted reproduction and genetics 20140517 8

<h4>Purpose</h4>To assess the age-associated changes in oocytes and granulosa cells derived from early antral follicles (EAFs).<h4>Method</h4>Gene expression analysis of granulosa cells of the EAFs using a genome analyzer (Illumina) and in vitro culture of oocyte-granulosa cell complexes (OGCs) of EAFs (400-700 μm in diameter) collected from ovaries of aged (>120 months) and young (<50 months) cows.<h4>Results</h4>Gene expression profiles in granulosa cells of EAFs of aged cows, which included c ...[more]

PMID: 24830789

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Project description:BackgroundAt later stages of folliculogenesis, the mammalian ovarian follicle contains layers of epithelial granulosa cells surrounding an antral cavity. During follicle development granulosa cells replicate, secrete hormones and support the growth of the oocyte. In cattle, the follicle needs to grow > 10 mm in diameter to allow an oocyte to ovulate, following which the granulosa cells cease dividing and differentiate into the specialised cells of the corpus luteum. To better understand the molecular basis of follicular growth and granulosa cell maturation, we undertook transcriptome profiling of granulosa cells from small (< 5 mm; n = 10) and large (> 10 mm, n = 4) healthy bovine follicles using Affymetrix microarrays (24,128 probe sets).ResultsPrincipal component analysis for the first two components and hierarchical clustering showed clustering into two groups, small and large, with the former being more heterogeneous. Size-frequency distributions of the coefficient of variation of the signal intensities of each probe set also revealed that small follicles were more heterogeneous than the large. IPA and GO enrichment analyses revealed that processes of axonal guidance, immune signalling and cell rearrangement were most affected in large follicles. The most important networks were associated with: (A) Notch, SLIT/ROBO and PI3K signalling, and (B) ITGB5 and extracellular matrix signalling through extracellular signal related kinases (ERKs). Upstream regulator genes which were predicted to be active in large follicles included STAT and XBP1. By comparison, developmental processes such as those stimulated by KIT, IHH and MEST were most active in small follicles. MGEA5 was identified as an upstream regulator in small follicles. It encodes an enzyme that modifies the activity of many target proteins, including those involved in energy sensing, by removal of N-acetylglucosamine from serine and threonine residues.ConclusionsOur data suggest that as follicles enlarge more genes and/or pathways are activated than are inactivated, and gene expression becomes more uniform. These findings could be interpreted that either the cells in large follicles are more uniform in their gene expression, or that follicles are more uniform or a combination of both and that additional factors, such as LH, are additionally controlling the granulosa cells.

Project description:Oocyte in vitro maturation can be improved by mimicking the intra-follicular environment. Oocyte, cumulus cells, granulosa cells, and circulating factors act as meiotic regulators in follicles and maintain oocyte in the meiotic phase until oocyte becomes competent and ready to be ovulated. In a randomized experimental design, an ovine model was used to optimize the standard in vitro maturation media by Granulosa secreted factors. At first, the development capacity of oocyte derived from medium (>4 to 6 mm) and small (2 to ≤4 mm) size follicles was determined. Differential gene expression of granulosa secreted factors and their receptors were compared between the cumulus cells of the two groups. Then, the best time and concentration for arresting oocytes at the germinal vesicle stage by natriuretic peptide type C (CNP) were determined by nuclear staining in both groups. Oocyte quality was further confirmed by calcein uptake and gene expression. The developmental competence of cumulus oocyte complexes derived from small size follicles that were cultured in the presence of CNP in combination with amphiregulin (AREG) and prostaglandin E2 (PGE2) for 24 h was determined. Finally, embryo quality was specified by assessing expressions of NANOG, SOX2, CDX2, OCT4, and TET1. The cumulus oocyte complexes derived from small size follicles had a lower capacity to form blastocyst in comparison with cumulus oocyte complexes derived from medium size follicles. Prostaglandin E receptor 2 and prostaglandin-endoperoxide synthase 2 had significantly lower expression in cumulus cells derived from small size follicles in comparison with cumulus cells derived from medium size follicles. Natriuretic peptide type C increased the percentage of cumulus oocyte complexes arresting at the germinal vesicle stage in both oocytes derived from medium and small follicles. Gap junction communication was also improved in the presence of natriuretic peptide type C. In oocytes derived from small size follicles; best blastocyst rates were achieved by sequential exposure of cumulus oocyte complexes in [TCM+CNP (6 h), then cultured in TCM+AREG+PGE2 (18h)] and [TCM+CNP (6 h), then cultured in conventional IVM supplements+AREG+PGE2 (18h)]. Increased SOX2 expression was observed in [TCM+CNP (6 h), then cultured in TCM+AREG+PGE2 (18h)], while decreased OCT4 expression was observed in [TCM+CNP (6 h), then cultured in conventional IVM supplements+AREG+PGE2 (18h)]. It seems that the natriuretic peptide type C modulates meiotic progression, and oocyte development is probably mediated by amphiregulin and prostaglandin E2. These results may provide an alternative IVM method to optimize in vitro embryo production in sheep and subsequently for humans.

Project description:BackgroundThe major function of the ovary is to produce oocytes for fertilisation. Oocytes mature in follicles surrounded by nurturing granulosa cells and all are enclosed by a basal lamina. During growth, granulosa cells replicate and a large fluid-filled cavity (the antrum) develops in the centre. Only follicles that have enlarged to over 10 mm can ovulate in cows. In mammals, the number of primordial follicles far exceeds the numbers that ever ovulate and atresia or regression of follicles is a mechanism to regulate the number of oocytes ovulated and to contribute to the timing of ovulation. To better understand the molecular basis of follicular atresia, we undertook transcriptome profiling of granulosa cells from healthy (n = 10) and atretic (n = 5) bovine follicles at early antral stages (< 5 mm).ResultsPrincipal Component Analysis (PCA) and hierarchical classification of the signal intensity plots for the arrays showed primary clustering into two groups, healthy and atretic. These analyses and size-frequency plots of coefficients of variation of signal intensities revealed that the healthy follicles were more heterogeneous. Examining the differentially-expressed genes the most significantly affected functions in atretic follicles were cell death, organ development, tissue development and embryonic development. The overall processes influenced by transcription factor gene TP53 were predicted to be activated, whereas those of MYC were inhibited on the basis of known interactions with the genes in our dataset. The top ranked canonical pathway contained signalling molecules common to various inflammatory/fibrotic pathways such as the transforming growth factor-β and tumour necrosis factor-α pathways. The two most significant networks also reflect this pattern of tissue remodelling/fibrosis gene expression. These networks also contain molecules which are present in the canonical pathways of hepatic fibrosis/hepatic stellate cell activation and transforming growth factor-β signalling and were up regulated.ConclusionsSmall healthy antral follicles, which have a number of growth outcomes, exhibit greater variability in gene expression, particularly in genes associated with cell division and other growth-related functions. Atresia, on the other hand, not only involves cell death but clearly is an active process similar to wound healing.

Dataset Information

Age-associated changes in bovine oocytes and granulosa cell complexes collected from early antral follicles.

Publications

Age-associated changes in bovine oocytes and granulosa cell complexes collected from early antral follicles.

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