Effect of Type 3 and Type 4 Phosphodiesterase Inhibitors on the Maintenance of Bovine Oocytes in Meiotic Arrest1

Abstract

The use of broad-spectrum inhibitors first suggested that phosphodiesterases (PDEs) are involved in the maturation of bovine oocytes. Modulation of individual PDE families is now possible with the use of newly developed type-specific PDE inhibitors. This study evaluated the role of type 3- and type 4-specific PDE inhibitors on the meiotic arrest of bovine cumulus-oocyte complexes (COCs) and denuded oocytes (DOs). It also evaluated the role of these specific inhibitors on meiotic arrest when COCs are incubated in the presence or absence of theca cell monolayers. Bovine COCs were aspirated from ovaries collected at the abattoir. Denuded oocytes and COCs were incubated for 12 h in culture medium alone or culture medium containing the type 3 PDE inhibitors cilostamide (10 and 20 microM) or milrinone (10 and 50 microM) or the type 4 PDE inhibitor rolipram (10 and 50 microM). Oocytes were then fixed and classified according to the status of nuclear maturation. Cumulus-oocyte complexes were coincubated with untreated theca cell monolayers or theca cell monolayers treated with the different specific PDE inhibitors. Bovine COCs or DOs incubated in culture medium resumed meiosis, but supplementation of the culture medium with the PDE3 inhibitors cilostamide or milrinone resulted in meiotic arrest. On the other hand, supplementation of the culture medium with rolipram did not prevent oocyte maturation. Furthermore, PDE3 inhibitors, but not PDE 4 inhibitors, had an additive effect on the inhibitory action of theca cell monolayers on oocyte maturation. These data support the hypothesis that inhibition of PDE3 prevents the meiotic resumption of bovine oocytes, whereas inhibition of PDE4 does not block oocyte maturation even under normally inhibitory conditions. The additive effect of PDE3 inhibitors on the ability of theca cells to maintain bovine oocytes in meiotic arrest suggests that type 3 PDE has an important role in meiotic resumption of bovine oocytes.

Effects of long-term in vitro exposure to phosphodiesterase type-3 inhibitors on follicle and oocyte development

“…To date, several reports attest the efficiency of selective PDEIs to arrest oocyte meiosis when applied in a short culture period during follicle and oocyte development (Tsafriri et al 1996, Mayes & Sirard 2002, Thomas et al 2002, Jensen et al 2002, Nogueira et al 2003b). The present results have revealed that long-term exposure of germ cells and their somatic follicular cells to the PDE3 specific inhibitors, cilostamide or org9935, does not alter their normal development.…”

“…Soluble forms of PDE3A exist in oocytes (Shitsukawa et al 2001), but the mechanisms of activation of the PDE3A remain unknown. Studies aiming to develop a new contraceptive strategy have shown that inhibition of PDE3A blocks oocyte meiosis in several species in vivo and in vitro (Tsafriri et al 1996, Wiersma et al 1998, Jensen et al 2002, Mayes & Sirard 2002, Nogueira et al 2003a.…”

Oocyte maturation and quality: role of cyclic nucleotides

“…Several years later, activity of the oocyte PDE3 was shown to increase before both spontaneous and gonadotrophin-induced meiotic resumption (Richard et al 2001). The effect of specific PDE3 inhibitors on maintaining oocyte meiotic arrest in vitro has now been demonstrated across many mammalian species: rats (Tsafriri et al 1996), mice (Wiersma et al 1998), cattle (Mayes & Sirard 2002, Thomas et al 2002, monkeys (Jensen et al 2002), humans (Nogueira et al 2003a) and swine (Laforest et al 2005). Demonstration of sterility of female mice bearing a PDE3A-null mutation due to the ovulation of GV-stage oocytes was the final proof of the central role of PDE3A in maintaining oocyte meiotic arrest (Masciarelli et al 2004).…”

The Control of Meiotic Arrest and Resumption in Mammalian Oocytes

“…In bovine oocytes, specific inhibition of PDE3 in vitro delayed spontaneous meiotic maturation and increased cAMP levels in cumulus cells and in denuded oocytes (BilodeauGoeseels, 2003b;Mayes & Sirard, 2002;Thomas et al, 2002). A study of PDE isoforms present in bovine follicle components showed that PDE3 accounted for 80% of the PDE activity in the oocyte, while PDE8 activity accounted for the remaining 20 and 60% of PDE activity in oocytes and cumulus cells, respectively.…”