Analysis of protein expression (secretome) by human and mouse preimplantation embryos

Objective: To analyze the protein production into the surrounding medium (secretome) of both human and mouse embryos and correlate these findings with ongoing blastocyst development. Along with improvements in culture systems, there is renewed focus on the development of noninvasive viability assays in human IVF. Because the majority of biologic functions are carried out by proteins, it is important to study the dynamics of the proteome during embryonic development and its response to both internal and external stimuli. Design: Experimental study. Setting: Research laboratory. Patient(s): Couples undergoing infertility treatment donated with consent spent culture media for research. Intervention(s): Analysis by time-of-flight mass spectrometry. Main Outcome Measure(s): Protein profiles of spent culture media. Result(s): Distinctive and significantly different secretome profiles were observed at each embryonic developmental stage (P < 0.05). Correlation of day 5 secretome data with ongoing blastocyst development revealed an 8.5-kDa protein biomarker that was significantly up-regulated (P < 0.05). The best candidate for this protein biomarker was ubiquitin, which has been implicated in the implantation process of mammalian species. Conclusion(s): This approach to analyze the secretome should not only further our understanding of embryo physiology but provide the basis for the development of noninvasive assays of embryo viability in human IVF.