Peptidomic analysis of blastocyst culture medium and the effect of peptide derived from blastocyst culture medium on blastocyst formation and viability.

High-quality in vitro human embryo culture medium can improve the blastocyst formation rate and blastocyst quality and be beneficial for the clinical application of single blastocyst transfer. Mammalian embryos can secrete protein products into the surrounding medium. As a group of bioactive molecules and degraded proteins, peptides have been shown to participate in various biological processes. Using liquid chromatography-tandem mass spectrometry, we performed comparative peptidomic analysis of human culture medium in blastocyst formation and nonblastocyst-formation groups. A total of 201 differentially expressed peptides originating from 157 precursor proteins were identified. Among these, a peptide derived from HERC2 (peptide derived from blastocyst culture medium [PDBCM]) passed through the zona pellucida, was distributed on the perivitelline space, was absent in arrest embryos and highly expressed in high-quality blastocysts compared with low-quality blastocysts, and significantly promoted blastocyst formation in a concentration-dependent manner. These results indicate that PDBCM may be a novel biomarker for predicting blastocyst formation and viability. The mechanism remains unclear and needs to be explored in the future.