Identification of apolipoprotein A1 in the human embryonic secretome.

OBJECTIVE: To identify factors secreted by the human embryo and correlate levels with embryo morphology and pregnancy outcome.
DESIGN: A laboratory-based study of human embryo protein synthesis and secretion and a retrospective analysis of spent embryo culture media as it relates to pregnancy outcome.
SETTING: University-based academic IVF program. PATIENT(S): IVF patients who had donated cryopreserved human pronuclear-stage embryos. Patients undergoing fresh IVF cycles resulting in a blastocyst transfer who donated spent media drops. INTERVENTION(S): In vitro embryo culture and collection of spent media. MAIN OUTCOME MEASURE(S): Protein analysis and identification by two-dimensional gel electrophoresis and mass spectrometry, ApoA1 quantification by ELISA, and mRNA analysis by quantitative reverse transcriptase-polymerase chain reaction. RESULT(S): By protein gel electrophoresis, apolipoprotein A1 (ApoA1) was increased in the culture media from good-quality blastocysts (n = 6 embryos) compared to either cleavage-arrested embryos (n = 6 embryos) or poor-quality blastocysts (n = 6 embryos) using spent media from culture days 4 and 5, respectively. Apolipoprotein A1 concentrations were 23.1% greater in day 5 spent culture media from good-grade blastocysts (n = 30) when compared to poor-grade embryos (n = 30). However, in a group of patients (n = 20) with transfer of two good-quality blastocysts, ApoA1 levels from day 5 spent media did not correlate with embryo implantation and pregnancy. Quantitative reverse transcriptase-polymerase chain reaction confirmed the presence of ApoA1 mRNA transcripts in human blastocysts. CONCLUSION(S): Apolipoprotein A1 is produced by human preimplantation embryos, and increased levels are present in spent culture media containing blastocysts of higher morphologic grade. These results suggest a role for lipoproteins in early embryologic development.