Effect of Specific Phosphodiesterase Isoenzyme Inhibitors During In Vitro Maturation of Bovine Oocytes on Meiotic and Developmental Capacity1

Abstract

Compared with oocytes matured in vivo, in vitro-matured oocytes are compromised in their capacity to support early embryo development. Delaying spontaneous in vitro meiotic maturation using specific phosphodiesterase (PDE) isoenzyme inhibitors may permit more complete oocyte cytoplasmic maturation, possibly by prolonging cumulus cell (CC)-oocyte gap junctional communication during meiotic resumption. This study aimed to investigate the effect of the isoenzyme 3- (oocyte) and isoenzyme 4- (granulosa cell) specific PDE inhibitors on the kinetics of in vitro maturation and on subsequent oocyte developmental competence. Cumulus-oocyte complexes from antral bovine follicles were isolated and cultured in the presence of the specific PDE inhibitors milrinone (type 3) or rolipram (type 4) (100 microM). In the presence of FSH, both PDE inhibitors only slightly extended CC-oocyte gap junctional communication over the first 9 h, but they completely blocked meiotic resumption during this period (P < 0.001). The indefinite inhibitory effect of milrinone on meiotic resumption (30% at germinal vesicle stage after 48 h) was overridden by 24 h when treated with FSH, but not with hCG, suggesting a form of induced meiotic resumption. Oocytes treated with FSH with or without either PDE inhibitor were inseminated at either 24, 26, or 28 h. Treated with either the type 3 or type 4 PDE inhibitor significantly (P < 0.05) increased embryo development to the blastocyst stage by 33%-39% (to an average of 52% blastocysts) compared with control oocytes (38%) after insemination at 28 h, and significantly (P < 0.05) increased blastocyst cell numbers when inseminated at 24 h. These results suggest that delayed spontaneous meiotic maturation, coupled with extended gap junctional communication between the CCs and the oocyte has a positive effect on oocyte cytoplasmic maturation, thereby improving oocyte developmental potential.

Regulation of sheep oocyte maturation using cAMP modulators

“…In parallel, increases in CC cAMP induce expression of EGF-like peptides and subsequent activation of the EGF receptor and MAPK pathway, thereby stimulating cumulus expansion and oocyte maturation [40][41][42]. It is widely reported that cAMP modulators in cattle IVM extended CC-oocyte GJC and increased oocyte developmental competence [13,19,20,32,43,44].…”

“…This spontaneous resumption of meiosis is accompanied by a rapid decrease in oocyte cAMP and is associated with reduced developmental competence [18]. There is now ample evidence that culturing oocytes in an environment where meiosis is regulated (via cAMP management), either prior to or during IVM, improves developmental competence [19][20][21][22][23]. This can be achieved by preventing the decrease in cAMP concentrations using PDE inhibitors throughout IVM, or by increasing COC cAMP concentrations during maturation with cAMP-elevating agents, e.g.…”

Fat area and lipid droplet morphology of porcine oocytes during in vitro maturation with trans-10, cis-12 conjugated linoleic acid and forskolin

“…However, when this supplementation was reduced to the first 2 h, meiosis progression, oocyte areas and cleavage rates were similar to those of control group. Nonetheless, several authors suggest that forskolin might be applied during oocytes IVM to improve synchronization of nuclear and cytoplasmic maturation, simultaneously increasing the homogeneity and developmental potential of matured oocytes (Racowsky, 1985;Thomas et al, 2004). Further studies are needed to clarify forskolin positive action on oocyte developmental competence for embryo production and quality.…”

“…At 10 mM dose, the meiotic arrest was fully reversible (Laforest et al, 2005). Moreover, by delaying spontaneous meiotic resumption, forskolin can increase oocyte development potential owing to a better synchronization of nuclear and cytoplasmic maturation (Thomas et al, 2004). Thus, the possibility of embracing both forskolin effects on meiosis synchronization and lipid content reduction in porcine oocytes should be investigated using different supplementation time periods.…”

Reversible meiotic arrest in feline oocytes

“…Similarly, the biochemical pathways involved with gonadotrophin-induced maturation following a period of arrest may better mimic the events occurring in the follicle after the LH surge (Gilchrist 2011). This approach has been tested by a variety of laboratories in pigs, cattle and mice, with some groups reporting significant improvements in embryonic development and others reporting little or no improvement compared with traditional IVM protocols (Funahashi et al 1997;Thomas et al 2004b;Gilchrist and Thompson 2007;Kawashima et al 2008;Albuz et al 2010).…”