Apoptosis‐independent Poor Morphology of Bovine Embryos Produced by Multiple Ovulation

Abstract

ContentsIn multiple ovulation and embryo transfer (MOET) programmes in cattle, a considerable number of morphologically poor-quality embryos continue to be produced; this is one of the limiting factors of the technique. Apoptosis has often been implicated in developmental arrest and fragmentation; these are regarded as poor traits of embryonic quality in mammalian pre-implantation embryos. In the present study, apoptosis was assessed in morphologically poor-quality embryos in comparison with good-quality embryos that were recovered from a MOET programme. Retarded embryos (two to 16 cell stage), morulae with severe fragmentation and morphologically goodquality morulae recovered from superstimulated cows at day 7 post-insemination were subjected to TdT-mediated dUTP nick-end labelling (TUNEL) and Hoechst staining. Cell nuclei that showed both TUNEL staining and apoptotic morphology were considered to be apoptotic. Apoptotic index (AI) was calculated as the percentage of apoptotic cells per embryo. Fifteen of 17 retarded embryos and 10 of 15 morphologically poor-quality morulae did not show signs of apoptosis. The mean AIs in the morphologically poor-quality embryos (two to 16 cell stage, 2.2%; poor morulae, 1.3%) were as low as that in the good-quality embryos (2.9%). These results suggest that another mode of developmental arrest and/or fragmentation that is independent of apoptosis occurs in morphologically poor-quality embryos recovered from MOET programmes.

Gene Expression in Early Expanded Parthenogenetic and In Vitro Fertilized Bovine Blastocysts

“…Within IVF bovine embryos, the stress-related protein p66 shc is upregulated in early arrest, while p53 seems to not be involved in the same function [60][61][62]. In contrast, within embryos developed in the uterus, developmental arrest has been described as being both apoptosis-dependent [63] and apoptosis-independent [64]. It is conceivable that gene expression upstream BAX differs between parthenotes and embryos, particularly in the way they channel apoptotic stimuli through p66 shc and p53 [11,65,66].…”

Senescence and Apoptosis During in vitro Embryo Development in a Bovine Model

“…Controversies between the association of apoptosis and embryo viability still exist (Haouzi and Hamamah, 2009), as shown by similar apoptotic indexes found by TUNEL between developmentally arrested in vivo bovine embryos, fragmented morulae and non-fragmented morulae (Ikeda et al, 2006). Similar results have been reported in the human species by TUNEL and Annexin V (Antczak and Van Blerkom, 1999).…”

Observation of freshBos indicusembryos comparing stereoscopic and phase contrast microscopy

“…Hardy & Spanos (2002) mentioned that cytoplasmic fragmentation may be a non-invasive marker of apoptosis-type programmed cell death, especially of the inner cell mass (ICM). Also, Ikeda et al (2006) have suggested that embryonic fragmentation is due to cellular division asymmetry, more than to the apoptosis process. However, in humans, the relationship between fragmentation and apoptosis has been described as subjective (Hardy et al, 1999;Jurisicova et al, 2003).…”

“…However, in humans, the relationship between fragmentation and apoptosis has been described as subjective (Hardy et al, 1999;Jurisicova et al, 2003). Also, Ikeda et al (2006) have suggested that embryonic fragmentation is due to cellular division asymmetry, more than to the apoptosis process. The index of apoptotic cells remained the same in the morula stage, whilst the fragmentation index was 50% higher; indicating that apoptosis and fragmentation may be independent processes (Van Soom et al, 2003).…”