Human preimplantation embryos secrete a number of soluble factors into
their environment, be it in vivo or in vitro. In vivo, these signals are fundamental for
survival and implantation of the blastocysts. In vitro, during an assisted reproduction
treatment, embryo-derived signals may be detected in the conditioned culture media and
might serve for the estimation of embryo quality and its capacity to implant.
Furthermore, the same fundamental soluble factors may be added to preimplantation
embryo culture media or instilled into the uterus during embryo transfer. Several
molecules have been detected in conditioned embryo media. The available literature
about the most prominent factors, HLA-G, interleukins, hCG, PAF, leptin, SP-1, EPF,
and Wnt beta catenin, are reviewed in this article. Several published results are
contradictory or are based on doubtful analyses, which detect protein concentrations in
the media which exceed the weight of the entire blastocyst. This review discloses the
littleness of the current knowledge about the human embryo secretome, the difficulties
of analyses and the need of further investigation.
Keywords: Preimplantation embryos, HLA-G, interleukins, hCG, PAF, leptin,
SP-1, EPF, Wnt beta catenin.
