Meiotic spindle morphogenesis in in vivo and in vitro matured mouse oocytes: insights into the relationship between nuclear and cytoplasmic quality

Abstract

The results emphasize the importance of coupling MT remodeling and cell cycle components during oocyte maturation to achieve a balanced coordination of nuclear and cytoplasmic maturation that under physiological conditions occurs within the first 5 h of LH stimulation.

Genetic strain variations in the metaphase-II phenotype of mouse oocytes matured in vivo or in vitro

“…Recently we have shown that the temporal progression of cytoplasmic and nuclear remodeling events were distinctly different in in vivo matured oocytes compared with oocytes matured under basal in vitro conditions in the outbred CF-1 mouse strain (Sanfins et al 2003(Sanfins et al , 2004, further supporting the notion that in vivo produced ova are generally of superior quality with respect to production of healthy embryos and offspring. It is well established that during in vitro maturation, although nuclear maturation takes place, complete cytoplasmic maturation is not assured (Eppig et al 1996).…”

Cumulus cell contact during oocyte maturation in mice regulates meiotic spindle positioning and enhances developmental competence

“…Maintaining a structural interaction during the earliest stages of meiotic resumption between the GV and oocyte cortex is likely to impact spindle morphogenesis at later stages of meiotic maturation as well as over-all developmental competence of the egg. In vivo matured oocytes assemble spindles within a contracted nuclear matrix comprised of lamin B that was proposed to limit MT assembly and MTOC involvement thus yielding diminutive spindles [39] compared to their in vitro matured counter. The notion of conserving resources at the protein level has also been studied in relation to spindle and/or polar body size.…”

“…COCs were cultured under conditions that either promote cumulus expansion, by adding hormone supplementation as well as the addition of FBS (IVM+), or not (IVMb) [8,39]. In IVMb (basal conditions, n=30), oocytes undergo GVBD within 2 h and chromosome condensation proceeds within a centrally positioned GV (Fig.…”

“…Despite the recognized functions of TZPs in gap junction mediated metabolite exchange, heterocellular adhesion, cell cycle regulation and bidirectional signaling [10,18,40,47], the precise role these structures play in the acquisition of developmental competence during oocyte maturation is unknown. It is known that the majority of mammalian oocytes develop in situ with an eccentrically positioned germinal vesicle (GV) that may facilitate retention of maternal transcripts and essential organelles by excluding these components from the developing spindle [2], Interestingly, in rodent species, the GV has been shown to lose an eccentric position after culture [38,39] and That has been proposed to be a result of a loss in cortical stability secondary to precocious TZP retraction. At ovulation, oocyte derived signaling molecules such as GDF9 and BMP-15 effect expansion of the compact cumulus mass through a process that confers enhanced developmental competence in oocytes of certain mammals [21,46].…”

Morphology and Aneuploidy of in vitro Matured (IVM) Human Oocytes

“…In vitro, oocytes begin their maturation earlier than in vivo (Motlik & Fulka, 1976) which is most probably a consequence of their premature extraction from the ovaries (Sanfins et al, 2004). Ovarian follicles contain inhibiting factors that retain the oocyte at proper meiotic phase for adequate time.…”