99 Impact of developmental environment and morphokinetic properties of bovine expanded blastocysts on mitochondrial fitness
J. Kurzella A , D. Salilew-Wondim B , F. Rings A , D. Miskel A , C. Blaschka B and M. Hoelker BA Institute of Animal Science, Animal Breeding, University of Bonn, Bonn, Germany
B Department of Animal Sciences, Biotechnology & Reproduction in Farm Animals, University of Goettingen, Goettingen, Germany
Reproduction, Fertility and Development 35(2) 176-176 https://doi.org/10.1071/RDv35n2Ab99
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Knowledge exists about differences between in vitro-produced (IVP) and in vivo-derived bovine embryos with respect to metabolism. Consequently, impaired quality of IVP embryos goes along with reduced blastocyst and pregnancy rates. Studies dealing with direct metabolic comparisons of embryos derived from these contrasting developmental environments regarding interdependencies between mitochondrial fitness and embryo quality, however, are rare. The present study therefore aimed to examine the relationship between contrasting environments (in vivo vs in vitro) as well as different intrinsic qualities (fast vs slow development), with mitochondrial metabolic activity. Therefore, bovine IVP embryos generated by routine procedures (SOFaa + 5% oestrus cow serum, 5% CO2 & 5% O2) reaching blastocyst expansion either faster (VITRO-HIGH-D7) or slower (VITRO-LOW-D8) were compared with expanded in vivo-derived Day-7 blastocysts (VIVO-D7) in terms of basal respiration, mitochondrial reserve capacity, and coupling efficiency of ATP production. These parameters were determined using an extracellular FLUX analyser (Seahorse XFp, Agilent) based on changes in oxygen consumption rate (pools of 8 expanded blastocysts, 4–6 replicates) following serial injection of oligomycin, FCCP, and rotentone/antimycin A (Cell-Mito Stress Test Kit, Agilent). Mean values for reserve capacity defined as maximal oxygen consumption after injection relative to basal oxygen consumption before injection were significantly impacted by developmental kinetics and environment (P < 0.05, ANOVA, bonferroni post hoc test). VITRO-LOW-D8 embryos showed a significantly lower mean reserve capacity compared to VITRO-HIGH-D7 and VIVO-D7 embryos (184.0 vs 279.0 vs 326%, respectively). In accordance, our results displayed that ATP coupling efficiency (defined as oxygen consumption for ATP production relative to basal oxygen consumption) was significantly reduced in VITRO-LOW-D8 embryos (P < 0.05), whereas coupling efficiency of VITRO-HIGH-D7 embryos did not differ compared to VIVO-D7 embryos (12.7% vs 66.1% vs 72.7%, respectively). Altogether, VITRO-LOW-D8 demonstrated significantly lower mitochondrial metabolic activities compared to VITRO-HIGH-D7 embryos. This finding was further confirmed by significantly lower values for lipid accumulation (Oil-Red-Staining) and higher contents of reactive oxygen species in VITRO-HIGH-D7 versus VITRO-LOW-D8 embryos. In summary, the present study illustrates a close connection between embryo developmental environment and intrinsic embryo quality and mitochondrial fitness. These findings might give points for further improvements of mitochondrial health of in vitro-derived embryos.
