Relationship Between the Length of Cell Cycles, Cleavage Pattern and Developmental Competence in Bovine Embryos Generated by <i>In Vitro</i> Fertilization or Parthenogenesis

Abstract

Abstract. This study was conducted to study the kinetics of initial cell divisions in relation with the cleavage patterns in viable (with the ability to develop to the blastocyst stage) and non-viable bovine embryos and parthenotes. The kinetics of in vitro development and cleavage patterns were observed by time lapse cinematography. The length of the first and second but not third cell cycle differed significantly between the viable and non-viable embryos after IVF or parthenogenesis. Viable embryos had significantly shorter first and second cell cycles than non-viable ones. The presence of fragments, protrusions and unequally-sized blastomeres was associated with an extended one-cell stage and reduced ability to develop to the blastocyst stage; however, the lengths of the second and third cell cycles were not altered. Oocytes showing direct division from one cell to 3 or 4 blastomeres showed similar developmental ability and embryonic cell numbers to those showing normal division, although, with a high frequency of chromosomal abnormalities. Our results suggest that the differences in the first cell cycles between viable and non-viable embryos were not sperm-related, whereas direct cleavage of 1-cell embryos to 3 or more blastomeres and protrusion formation are related to sperm-driven factors. The length of the first and second cell cycles and the cleavage pattern should be examined simultaneously to predict developmental competence of embryos at early cleavage stages. Key words: Bovine, Cleavage pattern, Developmental kinetics, Embryo, In vitro culture, Time lapse cinematography (J. Reprod. Dev. 56: [200][201][202][203][204][205][206][207] 2010) ecent progress in the improvement of in vitro embryo production (IVP) systems allows us to produce large quantities of bovine embryos [1]. Nevertheless, the developmental competence of embryos produced by IVP is still inferior to that of in vivo produced embryos due to by different stresses resulting from the imperfection of the IVP systems in imitating in vivo conditions [2,3]. Selection of embryos with good developmental competence is essential to achieve high success rates by transfer of embryos, especially when only one or a very few embryos are transferred into a surrogate mother at one time, such as in humans and cattle. The transfer of mammalian embryos at early cleavage stages (e.g., at the 1-8 cell stage) may have the advantage of avoiding stresses caused by the culture systems. Human embryos produced by assisted reproduction technology are still often selected and transferred at the cleavage stage [4]. Finding the most reliable marker of developmental competence in early embryos is still a matter of quest and debate among researchers. The number, morphology and position of pronuclei are often evaluated to estimate embryo quality in humans [5]; however, controversial data regarding these selection markers have also been reported [6,7]. Moreover oocytes of large farm animals such as pigs and cattle contain a high number of lipid droplets that completely blo...

Effect of follicular diameter, time of first cleavage and H3K4 methylation on embryo production rates of Bos indicus cattle

“…Similar results were obtained by another group who observed rates of 40% (cleavage up to 30 h post-IVF) and 10% (cleavage 30-36 h post-IVF, HUMBLOT et al, 2005), which are in agreement with previous reports (ISOM et al, 2012;LECHNJAK et al, 2008;SOMFAI et al, 2010) and later studies in which late-cleaving embryos resulted in lower blastocyst and pregnancy rates (BASTOS et al, 2008;MAGLI et al, 2007;SUGIMURA et al, 2012).…”

Evaluation of Developmental Competence of In Vitro-produced Porcine Embryos Based on the Timing, Pattern and Evenness of the First Cleavage and Onset of the Second Cleavage

“…In the same report, it was also reported that blastocysts derived from 3-or 4-and 5-to 8-cell embryos had a lower incidence of chromosomal abnormalities. On the other hand, an abnormal cleavage pattern may occur during the first embryonic cleavage, resulting in embryos with 3 or 4 blastomeres and abnormal chromosome numbers [22,23]. Selection of embryos with large blastomere numbers at an early developmental stage may therefore lead to contraselection of embryos with impaired developmental competence.…”

“…This result is different from previous observations in cattle embryos, in which the length of the second embryonic cell cycle was found to correlate with the developmental competence to the blastocyst stage [36]. Our data suggest clearly that, for early selection of high quality IVP embryos, careful investigation should be made for subsequent cleavages after the 2-cell stage.During embryo culture, an abnormal cleavage pattern may occur at the first embryonic cell division, resulting in embryos with unusually high numbers of blastomeres and abnormal chromosome numbers [22,23]. Abnormal cleavage pattern is believed to have a great influence on development of IVP porcine embryos [37]; however, it has not been studied substantially in this species yet.…”

Irregular cleavage of early preimplantation human embryos: characteristics of patients and pregnancy outcomes

“…Most aspirated oocytes are at the stage of metaphase II and develop two pronuclei after ICSI; yet, we surmise that in some, the cascade responsible for the activation of mitosis is disturbed. It ought to be mentioned that bovine zygotes that underwent direct division from one to three cells had developmental ability comparable to embryos with normal division, but with a high rate of chromosomal abnormalities [8].…”