DNA Content in Embryonic Extracellular Vesicles Is Independent of the Apoptotic Rate in Bovine Embryos Produced In Vitro

Simple Summary In this study, it is described that embryos produced in vitro release nanoparticles charged with fragments of embryonic DNA. These nanoparticles, alongside their DNA content, can be recovered from the liquid medium where the embryos develop in vitro and used to assess the genetics of embryos. The analysis of gene markers is a common practice in clinics for selecting human embryos without genomic errors. In animals, it can help in selecting embryos with high genetic value. So far, this has been achieved using embryonic biopsy to collect several cells; however, this is invasive due to the manipulation of the embryo. In this sense, the secreted nanoparticles containing DNA could stand as samples for genetic analysis, without disturbing the embryo. The main concern is whether these particles are mainly released by low-quality embryos that will eventually die. This work aimed to evaluate whether the rate of cell death in the embryo affects the release of particles containing DNA. It was confirmed that viable and good-quality embryos secrete particles with DNA in the same way as low-quality embryos; therefore, they represent a suitable alternative for embryonic genetic diagnosis, avoiding the invasive nature and technical complexity of a biopsy.Abstract Pre-implantation embryos release extracellular vesicles containing different molecules, including DNA. The presence of embryonic DNA in E-EVs released into the culture medium during in vitro embryo production could be useful for genetic diagnosis. However, the vesicles containing DNA might be derived from embryos suffering from apoptosis, i.e., embryos of bad quality. This work intended to confirm that embryos release DNA that is useful for genotyping by evaluating the effect of embryonic apoptosis on DNA content in E-EVs. Bovine embryos were produced by parthenogenesis and in vitro fertilization (IVF). On Day 5, morulae were transferred to individual cultures in an EV-depleted SOF medium. On Day 7, embryos were used to evaluate cellular apoptosis, and each culture medium was collected to evaluate E-EV concentration, characterization, and DNA quantification. While no effect of the origin of the embryo on the apoptotic rate was found, arrested morulae had a higher apoptotic rate. E-EVs containing DNA were identified in all samples, and the concentration of those vesicles was not affected by the origin or quality of the embryos. However, the concentration of DNA was higher in EVs released by the arrested parthenogenetic embryos. There was a correlation between the concentration of E-EVs, the concentration of DNA-positive E-EVs, and the concentration of DNA. There was no negative effect of apoptotic rate on DNA-positive E-EVs and DNA concentration; however, embryos of the best quality with a low apoptotic rate still released EVs containing DNA. This study confirms that the presence of DNA in E-EVs is independent of embryo quality. Therefore, E-EVs could be used in liquid biopsy for noninvasive genetic diagnosis.