The development of chemically defined media has become a particularly important task for in vitro embryo production systems, which require maintained reproducible results when new additives are tested for culture, beyond observational studies. Specifically, we need studies measuring the impact of these media on the embryonic transcriptome, particularly those negatively affecting embryo quality. Consequently, this study evaluated by using a microarray approach the transcriptome of porcine embryos produced in vitro, cultured in a defined vs. an undefined medium and contrasted with in vivo-derived embryos. No significantly altered genes were found between in vitro-produced embryos, despite the theoretical limitations that usually accompany defined media. However, when they were compared with in vivo-derived embryos, many altered genes were observed, reflecting how current culture conditions deeply modify the embryonic transcriptome. A better understanding of these alterations may offer new ways to improve in vitro embryo production systems. Likewise, developing a chemically defined medium capable of producing embryos of a similar quality to traditional media may contribute to this task.

The development of chemically defined media is a growing trend in in vitro embryo production (IVP). Recently, traditional undefined culture medium with bovine serum albumin (BSA) has been successfully replaced by a chemically defined medium using substances with embryotrophic properties such as platelet factor 4 (PF4). Although the use of this medium sustains IVP, the impact of defined media on the embryonic transcriptome has not been fully elucidated. This study analyzed the transcriptome of porcine IVP blastocysts, cultured in defined (PF4 group) and undefined media (BSA group) by microarrays. In vivo-derived blastocysts (IVV group) were used as a standard of maximum embryo quality. The results showed no differentially expressed genes (DEG) between the PF4 and BSA groups. However, a total of 2780 and 2577 DEGs were detected when comparing the PF4 or the BSA group with the IVV group, respectively. Most of these genes were common in both in vitro groups (2132) and present in some enriched pathways, such as cell cycle, lysosome and/or metabolic pathways. These results show that IVP conditions strongly affect embryo transcriptome and that the defined culture medium with PF4 is a guaranteed replacement for traditional culture with BSA.