Effects of cilostamide and/or forskolin on the meiotic resumption and development competence of growing ovine oocytes selected by brilliant cresyl blue staining.

The relevance of low developmental competence of in vitro-matured oocyte to the incomplete/delayed cytoplasmic maturation, and the heterogeneity of retrieved oocytes is well established in several species. A short phase of prematuration culture was used to allow better oocyte cytoplasmic maturation. The preselection of growing and fully grown oocytes has been proposed to improve developmental competency. This study investigated the effects of phosphodiesterase type 3-specific inhibitor, cilostamide, and adenylate cyclase activator, forskolin, on the resumption of meiosis and developmental competence of growing ovine oocytes selected by brilliant cresyl blue (BCB) staining. Results indicate that cilostamide, forskolin, and their combination significantly (P < 0.05) increased the percentage of growing (BCB-) oocytes maintained at the germinal vesicle stage. However, only forskolin significantly (P < 0.05) increased the yield and quality of blastocysts derived from BCB- oocytes compared with non-BCB-treated oocytes. We conclude that a short prematuration culture with forskolin may improve the in vitro developmental competency of growing oocytes in ovine.

Effect of phosphodiesterase type 3 inhibitor on nuclear maturation and in vitro development of ovine oocytes.

The present study aims to investigate if prematuration culture (PMC) of ovine oocytes in the presence of a phosphodiesterase type 3 (PDE3) inhibitor cilostamide can improve the shortcomings of conventional in vitro maturation (IVM) system. Therefore, a two-step culture system consisting of 22 hours culture in the presence of 1, 10, and 20 µM cilostamide (PMC medium), followed by 22 hours culture in maturation medium, was designed. The effect of cilostamide on gap junction communications and nuclear status was studied. The variables assessed were chromosome organization, spindle pattern, polar body extrusion, and embryonic development. According to the results, inhibition of PDE3 could not permanently block nuclear maturation in ovine oocytes but it delayed the process of nuclear maturation. Elevation of intra-oocyte cAMP concentration could inhibit cumulus cells expansion and maintain gap junction communications between oocyte and cumulus cells. Deletion of cilostamide and refreshing maturation medium after 22 hours culture revealed that cumulus cells were completely expanded. The inhibitory effect induced by 1 µM cilostamide was reversible, and it increased the number of mature oocytes with aligned chromosomes and normal spindle. However, the inhibitory effects of 10 and 20 µM cilostamide was not fully reversible and was associated with deleterious effects on chromosome organization and spindle pattern. Investigation of embryonic development via parthenogenetic activation and in vitro fertilization revealed that the blastocyst rate of oocytes that were prematured with 1 µM cilostamide was not significantly different from oocytes that underwent conventional IVM but it was significantly reduced in oocytes that were prematured with 10 and 20 µM cilostamide. Our results provide the evidence that reduced cAMP via PDE3 is not the only mechanism that controls the progress of nuclear maturation in sheep oocytes, and that alternative or additional mechanisms may also exist.

Effects of Protein Source and Energy Substrates on the In Vitro Development of Bovine Embryos in a Two-step Culture System

In this study, we examined the effects of a two-step culture system, which involves the use of different culture media for early cleavage and later stage embryos, on the in vitro development of bovine embryos. We also investigated the effect of glucose, phosphate and citrate on the in vitro early developmental period of bovine embryos in a two-step culture system. Moreover, the supplementation of different protein sources (BSA-V, BSA-FAF and FBS) during IVC did not affect the frequency of blastocyst development. Using two-step culture, embryos were cultured in protein-free media for an initial 5 days. This was then followed by the same culture media or an FBS supplemented media. The developmental rates of blastocysts in the FBS containing group were significantly higher than in the replaced with no serum containing group. Embryos cultured in mSOF supplemented with 1.5 mM glucose plus 1.2 mM phosphate were significantly inhibited. The inhibition of developmental competence by glucose plus phosphate was consistent with the existence of 0.5 mM sodium citrate. This study indicates that a two-step culture system, which applies different conditions for early cleavage embryos, i.e., serum-free media, vs. later stage embryos, with serum containing media, may be effective for in vitro production systems. In addition, the developmental competence of bovine embryos was depressed in the presence of glucose plus phosphate as compared to either alone or the absence of both. Therefore, the avoidance of this negative effect should allow more optimal conditions to be developed for in vitro production.