Advances in embryo selection methods

Abstract

Despite many recent advances in the field of reproductive biology and medicine, the efficiency of in vitro fertilization procedures remains relatively low. There is a need for a reliable and non-invasive method of embryo selection to ensure that only embryos with the highest developmental potential are chosen for transfer to mothers-to-be. Here, we compare various methods currently used for assessing embryonic viability, such as examination of embryonic morphology, quality of the genetic material, or metabolism. Additionally, we discuss novel procedures for embryonic assessment based on advanced time-lapse imaging techniques, which show great promise and may lead to increased in vitro fertilization efficiencies.

Figure 1.. Novel methods of predicting mammalian embryo viability involving an advanced time-lapse imaging

The method described by Wong et al. involves time-lapse imaging of embryos every 5 min for several hours (from 1- to 4-cell stage) [33]. In comparison, the method established by Ajduk et al. requires a much shorter period of recording (2.5 hours for mouse embryos) but with images taken every 10 seconds [37].

Figure 2.. Analysis of fertilization-triggered cytoplasmic movements in mouse zygotes

Mouse eggs are subjected to time-lapse imaging (1 frame every 10 seconds for 2.5 hours) immediately after fertilization [37]. Acquired images are analysed by the particle image velocimetry method that follows patterns of contrasts between subsequent images and calculates how they move. The sum of all displacement vectors calculated for the zygote in a given time-point (i.e. mean cytoplasmic speed) is plotted over time. The graph shows when fast cytoplasmic movements occurred in the embryo. Mean interval between the fast movements (in red) and mean speed in periods inbetween the fast movements (mean basal speed, in blue) are indicative of developmental potential of the embryo.