Timing of Embryo Development

Abstract

In vitro produced (IVP) embryos often exhibit wide variations in developmental competence and viability, considerably more than are exhibited by embryos that develop in vivo. These anomalies in IVP embryos may be due to heterogeneity of oocyte quality, suboptimal culture conditions, disturbances in gene expression, or most likely a combination of these factors (Ho et al., 1994 Roth et al., 1994; McKiernan and Bavister, 1998; Hasler, 1998; Schramm and Bavister, 1999; Doherty et al., 2000; Hyttel et al., 2000; Niemann and Wrenzycki, 2000; Wrenzycki et al., 2001). In research studies or in clinical applications with domesticated animals, cats, non-human primates and humans, oocytes used for IVP are usually collected from a heterogeneous cohort of ovarian follicles that include oocytes which normally might not be ovulated and/or are deficient in developmental competence. Moreover, although major improvements in culture media for oocyte maturation and embryo culture have been made in the last decade or so, IVP technology is still far from perfect (Bavister, 1995; Thompson and Peterson, 2000; Gardner et al., 2000; Vanroose et al., 2001. It is now clear that gene expression, including the critical transition from maternal to embryonic genome control, is subject to perturbations by culture media components, although the mechanism of this disturbance is not understood.