Abstract
Simple SummaryThis study was conducted with the aim of analyzing the morphokinetic parameters that determine the proper development of feline embryos in vitro. Our research was carried out using a time-lapse monitoring system shows that the timing of the first and second cleavage divisions, the timing of blastocyst cavity formation and morphological anomalies can all be used as early and non-invasive indicators of cat embryo development in vitro.The aim of this study was to analyze the morphokinetic parameters of feline embryos using a time lapse system. Oocytes matured in vitro were fertilized (IVF) and in vitro cultured in a time lapse-system (Primo Vision®, Gothenburg, Sweden). The first cell division of embryos occurred between 17 h post insemination (hpi) and 38 hpi, with the highest proportion of embryos (46%) cleaving between 21 and 24 hpi. The timing of the first cleavage significantly affected further embryo development, with the highest development occurring in embryos that cleaved at 21–22 hpi. Embryos that cleaved very early (17–18 hpi) developed poorly to the blastocyst stage (2%) and none of the embryos that cleaved later than 27 hpi were able to reach the blastocyst stage. Morphological defects were observed in 48% of the embryos. There were no statistically significant differences between the timing intervals of the first cleavage division and the frequency of morphological defects in embryos. Multiple (MUL) morphological defects were detected in more than half (56%) of the abnormal embryos. The most frequent single morphological defects were cytoplasmic fragmentation (FR) (8%) and blastomere asymmetry (AS) (6%). Direct cleavage (DC) from 1–3 or 3–5 blastomeres, reverse cleavage (RC) and vacuoles were rarely observed (2–3%). The timing of blastocyst cavity formation is a very good indicator of embryo quality. In our study, blastocyst cavity formation occurred between 127–167 hpi, with the highest frequency of hatching observed in blastocysts that cavitated between 142–150 hpi. Blastocysts in which cavitation began after 161 h did not hatch. In conclusion, the timing of the first and second cleavage divisions, the timing of blastocyst cavity formation and morphological anomalies can all be used as early and non-invasive indicators of cat embryo development in vitro.
Highlights
The domestic cat (Felis catus) is frequently used in research as a model for other feline species threatened with extinction
The first domestic cat kittens derived as a result of in vitro fertilization (IFV) were born 30 years ago [4], production efficiency remains low compared with other animal species, as an average of only 50% of inseminated cat oocytes develop into cleaved embryos and only 20% of these embryos reach the blastocyst stage [5,6,7]
A total of 1460 Cumulus-oocyte complexes (COCs) were collected in 33 repetitions of the experiment, of which 805 were suitable for fertilization (IVF)
Summary
The domestic cat (Felis catus) is frequently used in research as a model for other feline species threatened with extinction. The first domestic cat kittens derived as a result of in vitro fertilization (IFV) were born 30 years ago [4], production efficiency remains low compared with other animal species, as an average of only 50% of inseminated cat oocytes develop into cleaved embryos and only 20% of these embryos reach the blastocyst stage [5,6,7]. Progress in this area will rely on developing a better understanding of the mechanisms of fertilization and optimization of the in vitro culture conditions for feline embryos. Since most of these analyses require the destruction of the embryo, the most common non-invasive method used for the assessment of embryo quality and selection for embryo transfer is the standard morphological evaluation
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