The ART of selecting the best embryo: A review of early embryonic mortality and bovine embryo viability assessment methods

Abstract

Animal reproductive biotechnology is continually evolving. Significant advances have been made in our understanding of early embryonic mortality and embryo development in domestic animals, which has improved the selection and success of in vitro technologies. Yet our knowledge is still relatively limited such that identifying a single embryo with the highest chance of survival and development for transfer remains challenging. While invasive methods such as embryo biopsy can provide useful information regarding the genetic status of the embryos, morphological assessment remains the most common evaluation. A recent shift, however, favors alternative, adjunct approaches for non-invasive assessment of an embryo's viability and developmental potential. Various analytical techniques have facilitated the evaluation of cellular health through the metabolome, the assessment of end products of cellular metabolism, or by analyzing spent media for small RNAs. This review discusses the application of noninvasive approaches for ascertaining the health and viability of in vitro-produced bovine embryos. A comparative analysis of noninvasive techniques for embryo assessment currently being investigated in cattle and humans is also discussed.

Mining of variables from embryo morphokinetics, blastocyst’s morphology and patient parameters: an approach to predict the live birth in the assisted reproduction service

“…The time-lapse system (TLS) allows embryo development monitoring without its remotion from the incubator, through a coupled camera and an appropriate software that produces a video recording of its evolution (Kovacs, 2014;Perkel et al, 2015). In addition, frames obtained by means of TLS allow the acquisition of morphological and kinetic information besides asymmetry of the cleavages in a non-invasive way (Wong et al, 2010;Chen et al, 2013;Milewski & Ajduk, 2017).…”

Methods for assessing the quality of mammalian embryos: How far we are from the gold standard?

“…The technical quality assessment relies on the experience, attention to detail and systematic approach of the examiner on analyzing the embryo, from the more evident features as dead and extruded cells, or reduction of the percentage of viable cells to the more subtle characteristics that may influence embryo development such as irregularity of shape, heterogeneity of color, asynchrony between expected and encountered stage of development and the presence of vacuoles. On this classical approach of embryonic morphology, the variables are not measured in an objective form, resulting in low repeatability and subjectiveness of analysis (Bényei et al, 2006; van Loendersloot et al ., 2014; Perkel et al ., 2015; Richardson et al ., 2015; Thompson et al ., 2016). On this approach, a given embryo when analyzed by different examiners may be classified in different distinct degrees of quality (Farin et al ., 1995, 1999; Chen et al ., 2016).…”

>b<Cinética e desenvolvimento embrionário >i<in vitro>/i< de embriões bovinos de touros de alta e baixa fertilidade>/b<

“…Estima-se que a eficiência global do processo não ultrapasse 10% de embriões viáveis, quando feita a razão entre a taxa de prenhez e o número de oócitos fecundados no início do processo. Dentre as razões para a baixa eficiência, ou a falta de repetibilidade nas produções, destacam-se a baixa qualidade oocitária associada a fatores nutricionais, hormonais e metabólicos da fêmea, maturação oocitária incompleta, condições sub-ótimas de cultivo in vitro, qualidade da matéria prima dos meios de produção, qualidade da água e baixa qualidade espermática (PERKEL et al, 2015).…”

“…Sendo assim, a cinética embrionária, especialmente a primeira clivagem, poderia auxiliar a diferenciar touros com alta e baixa fertilidade in vitro. (PERKEL et al, 2015).…”

“…Outras metodologias, invasivas ou não, como avaliação de apoptose célular, contagem total e diferencial de células, presença e metabólitos no meio de cultivo, cariotipagem têm sido utilizadas para tentar estabelecer um padrão de qualidade embrionária ( VAN SOOM et al, 2003;PERKEL et al, 2015;SANCHEZ et al, 2017). (KROPP et al, 2017).…”