Ovine cumulus cells estradiol-17ß production in the presence or absence of oocyte

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• 作者：A. Shirazi ; Z. Moalemian
• 关键词：Sheep ; Oocyte ; Cumulus ; Estradiol-17&#xdf ; Nuclear maturation
• 刊名：Animal Reproduction Science
• 出版年：2007
• 期刊代码：8_03784320
• 类别：abs
• 出版时间：September 2007
• 卷：101
• 期：1-2
• 页码：125-133
• 文件大小：136 K

摘要

The objective of the present study was to compare the in vitro production of estradiol-17ß (E₂) by cumulus cells in the presence or absence of ovine oocyte. Moreover, the relationship between the concentration of produced estradiol-17ß and oocyte nuclear maturation was assessed.

Ovaries collected from the local abattoir were transported to the laboratory in saline at 30–35 °C within 1–3 h after collection. The oocytes of follicles, 2–6 mm in diameter, were recovered by aspiration. The oocytes with evenly granulated cytoplasm and which were surrounded with at least three layers of cumulus cells were selected and subjected to culture in pre-incubated oocyte culture medium (OCM). Before culturing, the selected oocytes were randomly divided into five treatment groups: Group 1, cumulus enclosed oocytes cultured in OCM (Group COCs); Group 2, denuded oocytes cultured in OCM (Group D); Group 3, denuded oocytes co-cultured with a cumulus cell-monolayer in OCM (Group D + M); Group 4, denuded oocytes co-cultured with previously cultured (for 26 h) cumulus cell-monolayer (10⁵ cells/ml) in refreshed OCM (Group D + M₂₆); Group 5, cumulus cell-monolayer (10⁵ cells/ml) cultured in OCM (Group M). After an incubation period (26 h at 38.6 °C, 5%CO₂ and 100%humidity), the media were collected and kept at −20 °C until hormonal assay. The concentration of E₂ was determined by RIA method. For assessment of nuclear status, the completely denuded oocytes were subjected to DAPI staining. The highest percentage of metaphase II (MII) stage oocytes was observed in Group N (91%) and the lowest percentage was observed in Group D (6%) and Group D + M₂₆ (6%). The mean production of E₂ was highest and lowest in Group D + M (378.69 ± 54.34 pg/ml) and Group D + M₂₆ (109.15 ± 8.24 pg/ml), respectively. The production of E₂ was significantly (P < 0.01) higher in Group D ± M when compared with Groups M and D ± M₂₆. Regarding the nuclear maturation, the percentage of MII stage oocytes was significantly (P < 0.001) higher in Group COCs compared to the other groups.

The results suggest that steroidogenic activity of cumulus cells in in vitro condition can be influenced by the pattern of connection between cumulus cells and the oocyte. Moreover, the nuclear maturation of oocytes is not influenced by the different production levels of E₂.