Differential Staining of Inner and Outer Cells to Assess Mammalian Embryo Quality

Abstract

The famous statement “A rose is a rose is a rose” by Gertrude Stein does not apply to the mammalian embryo. At first sight, the preimplantation eutherian or mammalian embryo shows many similarities between different species. The fertilized mammalian oocyte follows a common pattern of cleavage divisions, compaction and blastulation. Furthermore, the initial size of the embryo does not vary greatly between species. It is therefore difficult for an inexperienced observer to differentiate between laboratory animal embryos, domestic animal embryos and human embryos by routine stereomicroscopical evaluation. Upon more detailed examination, pre-implantation mammalian embryos from even closely related species differ with regard to their timing of development, their culture/metabolic requirements, the way they expand at the blastocyst stage, their behaviour at and after hatching and in the lipid content of their cells. These differences are also reflected in the various ways mammalian embryos resist cryopreservation and the efficiency of in vitro production procedures.