Developmental competence and quality of
in vitro produced embryos has been demonstrated to be lower than
in vivo derived embryos. This study aimed specifically to determine the effects of
in vitro culture of feline embryos using various culture densities on developmental competence and expression of stress- and apoptotic-related genes in terms of heat shock protein 70 (
HSP70) and apoptotic-related (
BAX and
BCL-
2) gene expressions. In experiment 1, we characterized the inducible form of a feline-specific
HSP70 mRNA sequence, as it has not been previously reported. The primers for feline
HSP70 mRNA were synthesized and tested on heat-treated cat fibroblasts. In experiment 2, feline embryos were cultured at different culture densities (embryo:culture volume; 1:1.25, 1:5 and 1:20). The developmental competence was determined along with
HSP70,
BAX and
BCL-2 transcript abundances using quantitative RT-PCR.
In vivo derived embryos were used as a control group. A partial cat
HSP70 mRNA sequence (190 bp) was characterized and exhibited high nucleotide identity (93 to 96%) with other species. Cleaved embryos cultured at high density (1:1.25) developed to blastocysts at a lower rate than those generated from lower densities. Irrespective of the culture densities used,
in vitro cultured blastocysts showed increased levels of
HSP70 and
BAX transcripts compared with
in vivo counterparts. Blastocysts derived from the highest culture density (1:1.25) showed higher levels of upregulation of
HSP70 and
BAX transcripts than those cultured at lower culture densities (1:5 and 1:20). In conclusion, increased levels of pro-apoptotic (
BAX) and stress-response (
HSP70) transcripts correlated with developmental incompetence of embryos cultured at high embryonic density, indicating that stress accumulated during
in vitro embryo culture affected the fate for embryo development and quality.
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