The Perivitelline Space-Forming Capacity of Mouse Oocytes is Associated with Meiotic Competence

Abstract

Abstract. Although mouse oocytes progressively acquire meiotic competence during their growth in the ovaries, only half of full-grown oocytes can accomplish meiosis. Two types of full-grown oocytes have been reported on the basis of their chromatin configuration, the surrounded-nucleolus (SN) type and the non-surrounded-nucleolus (NSN) type. Therefore, full-grown oocytes collected from the ovaries of adult animals comprise a heterogeneous population; some oocytes are meiotically incompetent (NSN-type), and some are competent (SN-type). In the present study, we found that fullgrown oocytes could be classified into two groups using the criterion of formation of the perivitelline space (PVS) after culture with 3-isobutyl-1-methylxanthine (IBMX) for 1 h. In oocytes with a PVS, actin-filled processes within zona pellucidae originating from cumulus cells were reduced, while they were rich in oocytes without a PVS, suggesting that a reduction in these processes contributes to PVS formation. PVS formation was highly correlated with meiotic competence and SN-type configuration. The results of this study demonstrate that PVS formation is a useful criterion for easily distinguishing between SN-and NSN-type oocytes, without injury to the cells.

Prediction of Developmentally Competent Chromatin Conformation in Mouse Antral Oocytes

“…The SN conformation of oocyte chromatin was reported to correlate with developmental potential of the oocytes, both in terms of completing meiotic maturation as well as promoting embryonic development after fertilization (ZUCCOTTI et al 1998;INOUE et. al.…”

“…Another approach was reported by Inoue and colleagues (INOUE et al 2007) who found that antral oocytes with SN configuration and high developmental competences develop perivitelline space upon one hour of incubation in the culture. This method is less complicated and time consuming and gives significant enrichment of the SN fraction from 64% in the whole population to 91% in oocytes which form the perivitelline space.…”

“…Using specific morphological criteria, oocyte quality may be predicted according to the NSN/SN chromatin configuration, position of the GV (BRU- NET & MARO 2007) or the ability to form perivitelline space during culture (INOUE et al 2007). All these approaches may have, however, some limitations.…”

“…Hoechst/UV exposure, however, was shown to impair development in several mammalian species (SMITH 1993;MASIDE et al 2011;GIL et al 2012;VERSIEREN et al 2014) which undermines the use of this procedure in oocyte selection for ART purposes. Other studies reported that in the mouse the oocyte chromatin conformation may be predicted in non-invasive ways according to the position of the oocyte nucleus (BRUNET & MARO 2007) or the ability to form perivitelline space (INOUE et al 2007). Having in mind that SN chromatin is attained upon oocyte growth, we examined to what extent the oocytes isolated from antral follicles differ in size and whether the size difference among such oocytes correlates with a specific type of chromatin.…”

Cell volume regulation in mammalian oocytes and preimplantation embryos

“…By the time they develop into mature MII eggs, oocytes have developed a perivitelline space (PVS) between the oocyte plasma membrane and zona pellucida (Dandekar and Talbot, 1992;Talbot and Dandekar, 2003). Although the development of the PVS had been largely assumed to be the result of the loss of oocyte volume to the first polar body, the PVS actually develops well before the extrusion of the first polar body and also develops in oocytes maintained in GV arrest that do not form a polar body (Inoue et al, 2007). Consistent with this, direct measurements indicated that oocyte volume decreases in vivo by about 20% within 8 hr after ovulation is triggered, reaching a minimum just before first polar body emission (Tartia et al, 2009).…”