Infertility is a distressing human health concern with a large proportion of cases attributed, at least in part, to dysfunction of the female reproductive system and specifically to reduced oocyte quality. As a result, patients often turn to costly assisted reproductive technologies (ART), with over 2 billion dollars spent annually on ART procedures in the US and failure ~ 69% of the time. Much needed improvements in the efficacy and safety of ART are limited by a dearth of fundamental knowledge of the intracellular and intercellular mechanisms and mediators of oocyte quality. The studies proposed here build upon a solid foundation of published data demonstrating a positive association of oocyte expression of the TGFb superfamily binding protein follistatin with bovine oocyte quality and a functional role for follistatin in promoting enhanced development of in vitro fertilized bovine embryos to blastocyst stage and blastocyst cell allocation to trophectoderm. Comparative studies using rhesus monkey embryos also support similar tropic actions of follistatin on embryonic development to blastocyst stage. However, lack of understanding of mechanism of action of follistatin in mediating above embryotropic actions and impact of follistatin treatment during embryo culture on pregnancy rates following embryo transfer limit understanding of the functional significance of follistatin to early embryogenesis and the translational relevance of above findings to improvements in human ART and biomedically relevant biotechnologies such as nuclear transfer/cloning in bovine species. Studies in Aim 1 will utilize a combination of pharmacological approaches, ablation replacement strategies and overexpression procedures in early embryos, combined with traditional RNA and protein analysis and analysis of epigenetic marks on key trophectoderm expressed genes to determine the mechanism of action of follistatin in promoting enhanced blastocyst development, blastocyst cell allocation to trophectoderm and interactions with specific TGFb superfamily members and their signal transduction pathways. Furthermore, deficiencies in extraembryonic lineage are common in pregnancies from nuclear transfer embryos and preliminary results demonstrate potent stimulatory effects of follistatin on nuclear transfer embryo blastocyst development and cell allocation to trophectoderm.
In Aim 2, the translational relevance of follistatin treatment as a tol to enhance ART will be determined via measurement of pregnancy rates and placental development for follistatin treated in vitro fertilized and nuclear transfer bovine embryos following embryo transfer and impact of follistatin treatment on epigenetic reprogramming of developmentally significant trophectoderm expressed genes examined. Upon completion of proposed studies, a better understanding of potential mechanism of action of follistatin and additional targets for therapeutic intervention will be known and the translational relevance of follistatin treatment during in vitro embryo culture as a tool to enhance ART and nuclear transfer pregnancy rates further elucidated.
Improvements in the efficacy and safety of assisted reproductive technologies (ART) utilized for treatment of infertility are limited by a dearth of fundamental knowledge of the mechanisms and mediators of oocyte (egg) quality. We are studying the intrinsic role and mechanism of action of follistatin in enhancing progression through early embryonic development and whether follistatin treatment of early bovine embryos can enhance pregnancy rates following embryo transfer. Such information is critical to potential application of follistatin treatment as a tool to enhance human ART and biomedically relevant embryo biotechnologies in cattle.
