Abstract
Objectives: The aim of this study was to assess different patterns of the human embryo secretome analysed as protein levels in culture media. Furthermore, analyses to correlate protein levels with quality and timing to development of human embryos were performed.Material and methods: Human day-2 cryopreserved embryos were cultured for four days in an EmbryoScope® with a time-lapse camera, and embryo quality was evaluated retrospectively. After culture, the media were collected and relative levels of secreted proteins were analysed using Proseek Multiplex Assays. Protein levels were evaluated in relation to timing to development and the ability to form a blastocyst.Results: Specific patterns of timing of development of blastocysts were found, where a difference in time to start of cavitation was found between high- and low-quality blastocysts. There appeared to be a correlation between specific protein patterns and successful formation of morulae and blastocysts. Embryos developing into blastocysts had higher levels of EMMPRIN than arrested embryos, and levels of caspase-3 were lower in high- versus low-quality blastocysts. Also, higher levels of VEGF-A, IL-6, and EMMPRIN correlated with shorter times to morula formation.Conclusions: The secretome and timing to development differ in embryos forming blastocysts and those that become arrested, and in high- versus low-quality blastocysts. The levels of certain proteins also correlate to specific times to development.
Highlights
Infertility affects about 15% of all couples of reproductive age
Embryos developing into high-quality blastocysts displayed a significantly shorter time to the start of cavitation compared with those that developed into low-quality blastocysts (61.1 h versus 69.7 h; P 1⁄4 0.039) (Table IV), and there was a tendency towards a shorter time to formation of a morula (50.6 h versus 57.2 h; P 1⁄4 0.059) (Table IV)
In culture medium collected from human embryos on developmental day 6, nine proteins were detected that were at a higher concentration than background levels in conditioned medium, i.e. culture medium without embryo (Figure 1; Table V)
Summary
Infertility affects about 15% of all couples of reproductive age. Assisted reproduction through in vitro fertilization (IVF) can be used as a treatment for these couples. The morphological approach, is inadequate for prediction of embryo quality and success rate after transfer, meaning a live born infant. The prediction models used in IVF clinics today are mainly based on general health factors such as body mass index (BMI), age, smoking, and reason for infertility, as well as biological markers and morphology of the embryo during development. VEGF-A, IL-6, and EMMPRIN ( known as CD147 or basigin) have been reported before as biomarkers of embryo development [17, 25,26,27], whereas, to our knowledge, this is the first time that PlGF, cystatin B, EpCAM, caspase-3, HE-4, and IL-8 have been detected in the secretome from early embryos and blastocysts. When comparing blastocysts and arrested embryos, the relative protein levels of EMMPRIN differed significantly. Levels of caspase were significantly lower, and those of VEGF-A tended to be higher in high-quality blastocysts compared with low-quality ones, which might suggest that these proteins could be considered as potential markers of the development of highquality blastocysts
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