Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8404388 | Animal Reproduction Science | 2015 | 9 Pages |
Abstract
Removal of oocytes from their natural inhibitory follicular environment results in spontaneous resumption of meiosis independent of normal signaling events that occur in vivo. Controlling the onset of meiotic resumption via maintenance of elevated oocyte cAMP levels with adenylyl cyclase (AC) activation and phosphodiesterase (PDE) inhibition, and subsequent hormone stimulation with follicle FSH has been shown to dramatically improve developmental competence of bovine and murine IVM oocytes. This study evaluated the effect of cAMP modulation during IVM of sheep oocytes on meiotic progression and development to blastocyst after parthenogenetic activation. Changes in oocyte cAMP levels were quantified during the first 2Â h of in vitro maturation in control or cAMP-modulating medium. No significant changes in intra-oocyte cAMP were observed under control conditions, though a slight and transient drop was noticed at 15Â min of maturation. Addition of the AC stimulator Forskolin and the PDE inhibitors IBMX altered the cAMP profile, resulting in 10-fold elevation of cAMP by 15Â min and sustained >3-fold elevated levels from 30 to 120Â min. The effect of cAMP elevation on meiotic resumption was measured by completion of germinal vesicle breakdown. Modulated oocytes were significantly delayed when compared to control media oocytes. Also, progression to MII was significantly delayed in modulated versus control oocytes at 20 and 24Â h, though no differences persisted to 28Â h. Lastly, when control and modulated oocytes were parthenogenetically activated, no differences in blastocyst formation were observed. Thus, while cAMP modulation delayed meiotic progression, it did not improve developmental competence of sheep IVM oocytes.
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Authors
Margaret Buell, James L. Chitwood, Pablo J. Ross,