Cellular and molecular regulation of zona lysis in mammalian preimplantation embryo. Austauschprogramm mit Indien

The cellular and molecular regulation of mammalian pre- and peri-implantation development is complex and difficult to study in vivo. The Indian and German research collaborators have successfully devised in vitro culture systems to study regulatory mechanisms governing blastocyst development and differentiation, including the phenomenon of zona pellucida (zona) lysis and blastocyst hatching, primarily in hamsters and rabbits. But also preimplantation embryo development in the mouse and bovine have been studied by both groups. In hamsters, an embryonic cysteine-like protease is involved in blastocyst hatching and the process is augmented by growth factors such as heparin binding-epidermal growth factor (HB-EGF) or leukaemia inhibitory factor (LIF), and the former also improves attachment and trophoblast outgrowth. Interestingly, rabbit blastocysts shed the zona by similar proteolytic mechanisms and rabbit, bovine and embryos of other mammalian species such as pig, sheep and horse also express a variety of growth factors and their cognate receptors. However, we do not yet know the biochemical and molecular nature of zona lysin(s) in these species and how its expression in the embryo-maternal (endometrial) tissues is regulated by various moleculaed such as EGF-, HB-EGF; LIF and transforming growth factor- (TGF- ). Expression paterns of some of these molecules and their possible function in zona lysis will be studied by both investigators. We believe that, among other developmental processes, blastocyst zona lysis and trophoblast attachment and outgrowth are regulated by autocrine and/or paracrine growth factors, produced by embryo-endometrial tissues, which remain to be thoroughly investigated.