mRNA Expression and Role of PPARγ and PPARδ in Bovine Preimplantation Embryos Depending on the Quality and Developmental Stage

SIMPLE SUMMARY: The results of the presented study proved that in vitro produced early- and late- cleaved bovine embryos express mRNA of peroxisome proliferator-activated receptor δ (PPARδ) and peroxisome proliferator-activated receptor γ (PPARγ) at all stages of early development (2-, 4-, 16-cell embryo, morula, blastocyst). The expression of PPARδ and PPARγ was correlated with the expression of quality markers in bovine blastocysts [sex-determining region Y-box 2 (SOX2), octamer-binding transcription factor 4 (OCT4), placenta-specific 8 (PLAC8), insulin-like growth receptor (IGF1R)]. It was found that in the group of early-cleaved embryos, which is after about 30 h after fertilization, positive correlations were stronger and more frequent, whereas the negative correlations were typical for group of late-cleaved embryos, which have a first cleave after 36 h. ABSTRACT: Peroxisome proliferator-activated receptors (PPARs), a nuclear receptors for prostacyclin (PGI(2)) have been recognized as being essential for early embryo development. The objectives of the present study were to determine if the bovine early- and late-cleaved embryos in different stages of early development express PPARγ and PPARδ. Since embryo developmental competence depends on numerous biological factors, we evaluated if the expression of PPARγ and PPARδ correlate with selected embryo quality markers (SOX2, OCT4, PLAC8, IGF1R) in the in vitro produced embryos at different stages of their development. Developmental rates and embryo quality for early- and late-cleaved embryos were provided according to International Embryo Transfer Society (IETS; developmental stages: 2-, 4-, 16-cell embryo, morula, blastocyst (1—early, 2—developing, 3—expanded, 4—hatched); quality stages: A—high quality, B—moderate quality, C—low quality). We found that bovine embryos expressed mRNA of PPARδ and PPARγ at all stages of early development, independently of their quality. In addition, the expression of PPARδ and PPARγ correlated with the expression of quality markers in bovine blastocysts. Positive correlations were stronger and more frequent in the group of early-cleaved embryos, whereas the negative correlations were typical for the group of late-cleaved embryos. Obtained results and available literature reports may indicate the participation of PGI(2), via PPARδ and PPARγ, in the processes related to the early embryo development, through the participation of this factor in the modulation of blastocyst hatching, implantation, and post-implantation development.